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Standard Components
Light Sources
Light Sources Semiconductor Components Sensors and Switches Clutches, Motors, and Solenoids Other Electrical Components Consumables
Our products use a variety of different light sources. These range from intense sources such as halogen lamps to relatively weak sources such as LED arrays. The light source selected depends on the function--original exposure, quenching, etc.--and the machine design. The most important light sources from a design point of view are those commonly used for original exposure (scanning)--the halogen lamp, the fluorescent lamp, and the xenon lamp. The most basic characteristics of these three lamps are summarized in the following table. Halogen Light Intensity Spectrum Temperature dependency* Stability at start-up Heat output Cost
*Dependency of light intensity on temperature
Fluorescent Low Narrow Large Poor Small Low
Xenon Low Narrow Large Good Smallest Lowest
High Wide Small Good Large High
of these three lamp types.
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Light Sources
Halogen Lamp
A Halogen lamp is an incandescent lamp filled with halogen gas (iodine or bromine). The halogen gas suppresses filament evaporation using a chemical regeneration process known as the "halogen cycle" (see below). Halogen lamps have a long effective life and strong light output.
Characteristics
· · · Extensive spectrometric distribution High illumination level Small changes resulting from the temperature of the light source and small transient changes · Long lead time to lighting · Large electricity consumption · Large heat output
halogen.pcx
Halogen Cycle
During lamp operation, the halogen gas combines with tungsten molecules that have evaporated off the filament. The evaporated tungsten molecules are then deposited back onto the filament, instead of on the lamp wall. Consequently, there is almost no reduction of light output from lamp wall darkening. Some light reduction from filament degradation does occur, but it is significantly lower than in other incandescent lamps. The halogen regenerative process requires that tungsten-halogen
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Light Sources
lamps operate at an extremely high temperature, which slightly increases lamp efficiency, and produces bright light and high temperatures. To withstand these high temperatures, tungstenhalogen lamps usually have quartz glass walls. Halogen lamps with quartz walled bulbs must be handled carefully. Quartz materials are extremely sensitive to oil and dirt from human skin, which can cause bulb wall deterioration, and premature lamp failure.
Applications
The intense light and wide spectral output of the halogen lamp suit it to color copiers and high-speed copiers. However, as it consumes a lot of electricity and undergoes drastic rises in temperature, it is generally not used for low-speed copiers and single scanner models. Since halogen lamps output a large amount of heat, they are also commonly used as a heat source in fusing units.
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Light Sources
Fluorescent Lamp
A fluorescent lamp is a closed glass tube that has electrodes at each end and an internal coated surface of a phosphorous material. The tube is filled with argon gas (or argon/krypton gas) mixed with a small amount of mercury vapor. When a suitable high voltage is applied across the electrodes, an electric arc forms and the resulting current ionizes the mercury vapor. The ionized mercury emits ultraviolet radiation, which strikes and excites the phosphor coating, causing it to glow and produce visible light.
FL operation (Illustration source unknown)
Characteristics
· · · · Has a medium luminance Produces excess heat from filaments Short lead time to lighting The exact makeup of the phosphor coating determines the color properties of a fluorescent lamp's light output. · The intensity of illumination changes depending on the tube temperature. · Uneven illumination at the ends of the tube requires shading plates.
Lamp heater
Fluorescent lamp
fluorsnt.pcx
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Light Sources
Applications
Fluorescent lamps are suited for use in low-speed color copiers as well as medium-speed black and white copiers. They are the most commonly used type of lamp in fax machines. However, the light quantity changes depending on the tube temperature; and a lamp heater may be included to solve this problem. Some Ricoh machines use a variation of the fluorescent lamp, called the cold cathode fluorescent lamp (sometimes called CFL or CCFL), as a quenching lamp or pre-transfer lamp. CFLs are also sometimes used as the exposure lamp in image scanners.
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Light Sources
Xenon Lamps
A xenon lamp is a tube filled with xenon gas. When a voltage is applied across the lamp terminals, the xenon gas ionizes and current flows through the gas, which emits light. The terminals do not have to be preheated, unlike in fluorescent lamps. There are different kinds of xenon lamp. The xenon lamps used in black and white digital machines output a yellowish-green light with a peak at 543 nm. The xenon lamps used with color machines utilize fluorescence as well as gas discharge to produce white light.
The xenon lamp used in model A250
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Light Sources
Characteristics
· · · · · Medium brightness light output Less expensive than fluorescent or halogen lamps Good durability--generally can be expected to last the life of the machine Low heat output--exposure cavity cooling isn't required More compact than fluorescent lamps
Applications
Xenon lamps can be used as exposure lamps for printers, lower speed copiers, fax machines, and scanners. Recently, xenon lamps have been increasingly used in digital products. This is mainly due to improvements in the spectral sensitivity of CCDs, which allows use of the more economical xenon lamp.
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Light Sources
Xenon Flash Lamp
The xenon flash lamps used in office machines are basically the same as the flash lamps used in photography-- only larger. A xenon flash lamp has main electrodes at both ends of a gas tube, which contains xenon (Xe) gas. (Generally, any noble gas will work in a flash lamp. However, gases other than xenon are rarely used.) The lamp also has trigger electrodes, generally in the form of a wire, or conductive coating in the lamp tube wall.
xenon.pcx
The typical xenon flash lamp circuit consists of four parts: (1) power supply, (2) energy storage capacitor, (3) trigger circuit, and (4) the flash lamp itself. It operates as follows: · · · The energy storage capacitor connected across the flash lamp is charged by the power supply. (The energy storage capacity is quite large.) A separate small capacitor is charged to generate a trigger pulse. The charge on the trigger capacitor to is dumped into the primary of a pulse transformer whose secondary is connected to the trigger electrodes. The pulse generated by this trigger is enough to ionize the xenon gas inside the flash lamp.
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Light Sources
·
The resistance of the ionized xenon gas is very low and the energy storage capacitor discharges through the flash lamp, which then emits a brilliant burst of light.
Characteristics
· Produces an intense peak of radiant energy. · Since flash lamps use a high voltage, precautions must be taken against electric shocks.
Applications
Xenon flash lamps are suited for use in high-speed black-and-white copiers. They are also occasionally used as the heat source for flash fusing.
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Light Sources
Neon Lamps
Like the cold cathode fluorescent lamp, a neon lamp uses a cold cathode to excite the atoms of a gas in an enclosed tube. However, the light is emitted by the neon gas in the tube rather than by a phosphorous coating inside the tube. The neon gas gives an orangish-red light.
Applications
In Ricoh products, neon lamps are used only as quenching lamps.
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Light Sources
LED Arrays
LED stands for light emitting diode. As the name implies, an LED is a diode that emits light when a small electric current passes through it. LEDs are commonly used as display devices and indicators (see the next section), but they can also be mounted together in an array and used as a light source.
Characteristics
· LED arrays can be wired so that the LEDs can be turned on/off in blocks to provide precise illumination. · LED arrays are useful where compact components are required.
Applications
In Ricoh products, LED arrays are used for document exposure in small fax machines and scanners. They are commonly used as quenching lamps in analog and digital copiers. Also, most analog copiers use them for erase lamps. The illustration to the right shows an LED array [A] used as an erase lamp in a copier.
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[A]
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Standard Components
Semiconductor Components
Semiconductor Components
This section deals with components that are based on semiconductors.
Diodes
Normal Diodes
A diode consists of a p-type semiconductor joined to an ntype semiconductor. A diode only passes current in one direction. If it is connected up as shown opposite, current will flow. However, if the power source is connected up the opposite way around, current will not flow.
Current flow P
+
_
N
Symbol:
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Zener Diodes
A zener diode is connected the opposite way around from a normal diode. Normal diodes cannot pass any current if connected up in this way, and may be destroyed. However, zener diodes connected in V reverse will pass current, if the voltage across the diode exceeds a certain value, known as the breakdown voltage. After the breakdown voltage has been reached, the voltage across the diode will not change much, even if the current is greatly increased. Zener diodes can be used to make sure that the voltage at a certain point in a circuit (Vz in the above-right diagram) does not exceed a certain value. The diagram below right is the typical diode characteristic curve. While normal diodes should operate below the breakdown voltage and may be damaged if it is exceeded, the zener diode is intended to operate at that voltage.
+
V Z
Zener Diode
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Semiconductor Components
Varistors
A varistor acts like two zener diodes connected back to back. This means that it has positive and negative breakdown voltages. A single zener diode only has a negative breakdown voltage. Varistors are used in similar ways to zener diodes. They are also useful in protecting circuits against voltage spikes. The example to the right shows a varistor connected across a switch to eliminate sparking. The illustration below right shows the characteristic double-breakdown curve of the varistor.
Vac
L
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Semiconductor Components
Light Emitting Diodes
A light emitting diode (LED) is a kind of diode that emits photons (light particles) when a small electric current passes through it. When current flows across the pn junction in diodes, energy is released in the form of heat. However, the material used to make LEDs is selected so that some of the energy is emitted as light. Light emitting diodes have some special characteristics. They convert electrical current directly into light; therefore, the LED is more efficient than many other light sources. Also the light emitted by an LED has a narrow wavelength range. The LED is enclosed in a transparent case of epoxy resin or plastic. The typical LED produces red or infrared light; however, there are varieties to produce many colors. Alternately, as shown in the illustration, a colored case can be used to modify the light output. LEDs can be used to form large displays and are often the lighting elements in information displays used in public places such as highways and airports. In office machines, LEDs are used to light indicators on operation panels, as indicator lights on circuit boards, and in LED arrays.
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+
Current flow P N
_
P N
Symbol:
A small PCB with indicator LEDs on it.
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Semiconductor Components
Laser Diodes Natural light is a mixture of light of different wavelengths. However, a laser beam consists of light at one wavelength, and the waves are all in phase (the peaks and troughs in the waves all coincide). As the waves are all in phase, the light is very intense (if peaks and troughs do not coincide, they tend to cancel each other out, reducing the power of the beam). Natural light can be focused, but it cannot be focused to so fine a point as laser light can. This is because a lens at the same angle does not refract the different components of natural light, having different wavelengths. To the right is a simplified diagram of a laser diode. Laser diodes can be considered as similar to LEDs in operating principle; current flowing across the pn junction causes energy to be emitted in the form of light. LEDs emit light in all directions. However, the pn junction in laser diodes has a mirror at each end, reflecting the light back into the diode. When the current
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P
N
Current flow
+
_
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Semiconductor Components
passing through the diode reaches a threshold value, the light reflected back into the junction stimulates more atoms in that region to emit more radiation of the same wavelength. Some of this light passes out of the diode through one of the mirrors, which is partially transparent. The light beams emerge from the mirror parallel to each other. The wavelength of the laser depends on the composition of the semiconductor material. The lasers used in most printers emit red light. Engineers are trying to develop lasers that emit green or blue light; the shorter wavelengths of this light would allow smaller dots to be written to the photoconductor, leading to higher resolution printouts.
Laser diode LD Unit
For More Information
For a brief introduction to laser theory and more information on laser diodes we suggest you reference A Brief Introduction to Laser Diodes at the University of Washington web site (http://www.ee.washington.edu/class/ ConsElec/Chapter6.html)*. *We have no control over this web page. The content or location may change at any time.
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Transistors
Bipolar Junction Transistors
A bipolar junction transistor contains two junctions between p and n type semiconductor, and three electrodes (the collector, the base, and the emitter). The most common use of a transistor is as a switch. They are also used in amplification and rectification. There are two types of transistor: the npn transistor, and the pnp transistor. The npn transistor is the most commonly-used of these. The diagrams to the right show the symbols for both types of transistor, their construction, and the direction of current flow. Notice that the batteries in the pnp transistor circuit are connected up the opposite way round from the npn transistor. (Continued on next page.)
NPN Type
PNP Type
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In the diagram on the right, an npn transistor is controlling a lamp. A positive voltage is applied between the collector and the emitter. The lamp cannot switch on unless a voltage is also applied between the base and the emitter.
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Phototransistors
A phototransistor works like an ordinary bipolar transistor, except that the transistor is switched on by light shining on the base region of the transistor. The diagram on the right shows an npntype phototransistor. In office machines, phototransistors are used in photointerrupters, optoisolators, and reflective photosensors.
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Sensors and Switches
Sensors and Switches
Reflective Photosensors
Reflective photosensors are short range sensors that have a light emitting element (usually an LED) and a light sensitive element (usually a phototransistor). Reflective photosensors work by bouncing light off of an object. There are two main types of reflective photosensor. The simplest type signals the presence or absence of an object or condition--the presence of paper, the presence of a belt reference plate, the presence of a cassette or cartridge. The illustration to the right is an example. This type of sensor has a binary output; it is either activated or deactivated. The other type of reflective photosensor is used to gather information about the surface being sensed. It has a variable output that depends on the strength of the light striking the light sensitive element. The primary example is the image density sensor (or ID sensor) used in copiers and other products.
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Characteristics
! Small, inexpensive, rugged ! Available in many different types (size, shape, sensitivity, specifications).
Applications
Reflective photosensors are used for detecting paper in the paper path, paper size detection, master belt position detection, and a number of other functions.
A reflective photosensor
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Sensors and Switches
ID Sensor
The ID sensor is a special application of the reflective photosensor. Two types of ID sensor are used as part of the process control system in photocopiers. One type is a direct reflection ID sensor. It is positioned so that light from the LED reflects directly to the detector. This is the commonly used type of ID sensor. The other type is a diffused reflection ID sensor. In addition to the light reflected at a direct angle, diffuse light reflects at all angles from the toner on the drum. This sensor detects image density by receiving some of this diffused light. Using this type of sensor improves the measurement accuracy of the sensor pattern densities-- particularly for yellow, cyan, and magenta toners.
Direct reflection ID sensor
Drum Toner
LED
Detector
Diffused reflection ID sensor
Drum Toner
Detector LED Diffuse light
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Sensors and Switches
Photointerrupters
A photointerrupter consists of an LED and a phototransistor separated by a slot. The sensor detects when something enters or leaves the slot, such as an actuator, a part of the machine, or a sheet of paper. When there is no actuator in the slot, light from the LED activates the phototransistor, and current flows through it. However, if an actuator enters the slot, light from the LED is blocked and current cannot pass through the phototransistor. Photointerrupters have a variety of uses in office machines. They are commonly used as home position detectors for moving parts such as lenses and scanners and to detect paper as it moves through the paper feed path. In machines such as photocopiers that handle a variety of feed stock photointerrupters are generally preferred over reflective photosensors because photointerrupters are not affected by the reflectivity of the paper. Continued on next page.)
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Sensors and Switches
Characteristics
! Small, inexpensive, rugged ! Available in many different types (size, shape, sensitivity, specifications).
Most photointerrupters that are used as paper detectors use a "feeler" type plastic actuator. However, a photointerrupter is occasionally installed across a paper feed path, as shown above. This type of photointerrupter may become dirty and will need cleaning periodically.
[A]
Photointerrupters: The one on the left has a weight operated actuator built on it.
A photointerrupter [A] used as a home position sensor. Notice the scanner drive wire below the slot of the photointerrupter.
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Sensors and Switches
Charge transfer control signals T1 T2 T3
CCDs
A CCD (Charge Coupled Device) is a semiconductor chip with light receiving elements etched onto it. In a digital machine that scans documents, the CCD is a row of these elements; each element on the CCD corresponds to one pixel on one main scan line across the original. The CCD also contains circuits for transferring the accumulated charges out of the elements and into the video processing circuits. The diagram on the right shows a simplified crosssection of a CCD element. When applying the appropriate voltage across the element, any light hitting the element liberates electrons from the silicon at the boundary between the n and p type semiconductors. Positive charges can flow out, but an insulating layer traps the electrons, and gathers them under the electrodes. The brighter the light shining on the element, the more electrons generated in that element.
Charge transfer circuits Light sensitive elements
Output
N P
_ +
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Sensors and Switches
After scanning a line, the charges trapped in each element must be moved out of the CCD and into the video signal processing circuits so that the next line can be scanned. The diagram shows how this is done. The diagram shows two adjacent elements. Each element has three electrodes attached to it. After scanning a line of data, the electrons are under electrode 1, as shown in the top diagram. A voltage V2, higher than V1, is then applied to electrode 2. The electrons are attracted to the area beneath electrode 2, as shown in the middle diagram. Then, the voltage at electrode 1 switches off and the voltage at electrode 2 is set to V1, as shown in the bottom diagram. The electrons all gather under electrode 2. By repeating the above procedure, but using electrodes 2 and 3 instead of electrodes 1 and 2, the electrons move to
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T1 = V1 T2 = 0 1 2 3 1 2 3 T3 = 0
__ __
__ __
T1 = V1 T2 = V2
1
2
3
1
2
3
T3 = 0
__ __ _ _ __
__ __ _ _ __
T1 = 0 T2 = V1
1
2
3
1
2
3
T3 = 0
__ __
__ __
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electrode 3. The result of this is that one element shifts all the charges along, and the element charges at the end of the CCD shift out of the CCD. By continuing this process, all the charges shift out of the CCD. The series of charges appears on the CCD output line as a serial analog video signal. This signal passes to the video processing circuits, allowing the next line of the original to be scanned.
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Sensors and Switches
Contact Image Sensors (CIS)
The contact image sensor (CIS) is a compact image reading assembly containing an LED array, an array of self-focusing optic fibers (SELFOC), and a strip of light detectors, such as phototransistors. The CIS is used instead of the CCD in the most compact of fax machines. The illustration to the right (from model H545) shows a typical CIS. Light from the LED array [A] reflects off of the document, through a row of selffocusing optic fibers [B], and onto a strip of phototransistors [C]. The entire assembly is located directly below the document, so a long light path is not necessary. When using a fluorescent lamp/lens/CCD arrangement, the light path is typically about 300 to 500 mm. However, with a CIS, the light path can be reduced to about 15 to 50 mm; with the most recent types, the CIS is positioned less than 0.1 mm from the surface of the document.
[B] [A]
[C]
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Sensors and Switches
Hall Effect Sensors
Hall effect sensors are used in some network control units (NCU) of fax machines to detect line current. The output of a Hall effect sensor is called the Hall voltage. If a conductor [A] is placed in a magnetic field [B], and current [C] flows through this conductor perpendicularly to the magnetic field, a Hall voltage (VH) is generated across the conductor. The conductive material in Hall effect sensors is normally a semiconductor, as the Hall effect is too small to measure accurately in metallic conductors.
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Sensors and Switches
Thermistors
A thermistor is a device that undergoes a very large change of resistance with temperature. The name is derived from thermally sensitive resistor. Typically, a thermistor is made from a semiconductor or sintered metal oxides. Most types have a negative temperature coefficient--that is, the resistance decreases as the temperature increases. However, some positive temperature coefficient varieties are also available. The material can be formed into rods or small beads, but for sensing purposes the small bead shape is generally used in order to get the fastest possible response. Thermistors have a large variety of uses. In office machines, they are used mainly to measure the temperature at critical points--for example inside fusing units or optic cavities.
[A]
Thermistors [A] used to measure the temperature of fusing rollers (model G024)
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Sensors and Switches
Microswitches
Microswitches are electromechanical devices, which contain two contacts. They are modular, inexpensive, resistant to dust and contamination as well as metered. This means that any time the actuator is depressed, the contacts of the switch will close at the same point each time. These switches have a characteristic sound or click when the contacts close. The main advantage of a microswitch is its durability and its consistency.
The "normally open" terminal of this switch has been removed so that it cannot be connected incorrectly.
FP = Free Postion OT = Overtravel OP = Operating Position PT = Pretravel RP = Release Position MD = Movement Differential OF = Operating Force Above pictures courtesy of Zippy USA Inc.
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Sensors and Switches
Reed Switches
Reed switches are magnetically operated components with contacts hermetically sealed in a glass capsule. Bringing a permanent magnet to the switch or placing the switch in or near an electromagnet causes the contact "reeds" to flex and touch, completing the circuit. Either protective inert gas or a vacuum within the capsule keeps the contacts clean, protecting them for the life of the device. Due to their lack of mechanical parts, reed switches are maintenance-free and remain unaffected by temperature change, moisture, chemicals, dust, abrasive fluids and other hostile surroundings. Features: · Reliable · Non-mechanical · Long operating life · Compact · Rugged
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Sensors and Switches
Thermoswitches
As the name implies, a thermoswitch (also known as thermal switch or thermostat) is a temperature controlled switch. Thermoswitches have contacts made of two dissimilar metals molecularly bonded together. These are called bi-metal contacts. The two metals expand and contract at different rates with changes in temperature. As the temperature rises the bi-metal contacts start to flex, and at a certain temperature, the contacts will open. At a lower, temperature, the contacts will close again. The difference between the opening and closing temperature of a thermoswitch is the "hysterisis" or "differential" of the device. Some thermoswitches, such as those used in deep fat cookers or popcorn machines, have a narrow hysterisis. However, In Ricoh products, thermoswitches are usually overheating safety devices with a large hysterisis. For example, the thermoswitch used in the 1st scanner of model A257 opens at 140ºC but will not close again until its temperature drops to -35ºC!
A collection of thermoswitches. (Photo courtesy of Elmwood Sensors, Inc.)
Note: Thermoswitch and thermostat are often used interchangeably. In fact, thermostat is the term used in our parts catalogs. However, here we use thermoswitch to avoid confusion with adjustable control devices such as room temperature thermostats.
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Standard Components
Clutches, Motors, And Solenoids
Clutches, Motors, And Solenoids
Clutches
Torque Limiter Clutches
In Ricoh products, torque limiter clutches are often in reverse rollers of feed and reverse roller paper feed mechanisms. In concept, torque limiter clutches (also called slip clutches) are simple. They transmit rotation to a drive component (usually a roller, pulley, or gear mounted on a rotating shaft). As long as the resistance to rotation is less than the torque (twisting force) limitation of the clutch, the roller turns with the shaft. If the resistance exceeds the torque limitation, the roller stops turning--it slips. In fact, it may turn in the opposite direction if sufficient counter force is applied. Torque limiter structures vary: some use springs as slip mechanism, while others use magnetic force or powder filling. Compared to those that use springs, torque limiters that use magnets and/or powders do not need to be lubricated with
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Clutches, Motors, And Solenoids
grease or other lubricants, so that they are easier to maintain. In addition, the magnet-type torque limiter does not generate much heat, even after extended use, because it does not come in contact with other components. Consequently, it ensures stable torque. The torque limiter of the model A112 reverse roller, shown on the previous page, is a magnetic type. Here are some other examples of torque limiter clutches: The clutch used in Model A084, illustrated to the right, uses two coupled magnetic type clutches. (Two coupled clutches have a stronger total torque than a single clutch.) Continued on the next page.
Model A084 (magnet) Outer magnet Casing Inner magnet
Drive shaft
Rotor
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Clutches, Motors, And Solenoids
Model A133 uses a magnet and ferrite powder type slip clutch.
Model A133 (magnet + ferrite powder)
Magnetic ring
Output hub
Input hub Ferrite ring
Ferrite powder
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Clutches, Motors, And Solenoids
Electromagnetic Clutches
The illustration to the right diagrams the basic [D] parts of an electromagnetic clutch. Gear [A] is driven by a motor. This gear is an idle gear; it does not drive the roller shaft [B]. Shaft [B] is attached to the rotatable part [C] of the clutch, and held in place by an E-ring [D]. When the clutch is switched on, current flows through the coil [E]. The magnetic field generated by this coil attracts plate [F], which is connected to gear [A]. The motor is still turning gear [A], and when plate [F] comes into contact with the rotating part of the clutch [C], the roller shaft begins to turn. A typical application is shown to the right, where a clutch [A] switches on to connect shaft [B] to the drive from motor [C]. Continued on the next page.
[E]
[F] [A] [B]
[C]
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Clutches, Motors, And Solenoids
An electromagnetic clutch requires + 24 or + 12 volts to drive it, but a CPU cannot output this high a voltage, so the CPU controls the clutch through a driver. When the clutch is off, the driver is holding the control signal to the clutch high, preventing current from going to ground. When the CPU drops the control signal low, + 24V flows through the coils in the clutch, and through the driver to ground.
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Clutches, Motors, And Solenoids
Spring Clutch
A spring clutch is purely mechanical clutch. It is a simple device that consists of two separate pieces fitted inside a coiled spring. One piece called the drive hub, supplies rotation from a motor. The other piece, called the output hub, delivers the rotation of the drive hub to a shaft. Under normal circumstances, the spring grips both pieces very tightly, so they function as one unit and pass on the rotation from the motor. The clutch's release mechanism is a sleeve that surrounds the spring. The sleeve is attached to one end of the spring--the clutch spring tail. The other end of the spring is engaged with the output hub. When the sleeve is kept from turning, the spring expands away from the drive hub, disengaging the drive. The sleeve of a spring clutch either has a ratchet surface for a pawl to engage with or one or more projections for a stopper to engage with. Typically, spring clutches are engaged and disengaged by some kind of electronic control--usually a solenoid.
Spring tail
Sleeve projection
Drive Hub
Output Hub Sleeve
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Clutches, Motors, And Solenoids
Magnetic Spring Clutch
A magnetic spring clutch is a hybrid of the electromagnetic clutch and the spring clutch. Unlike the normal spring clutch, the spring is loose while idling. When the electric coil is energized, it causes the spring to tighten around the output element.
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Clutches, Motors, And Solenoids
DC Motors
Electric motors are based on the following two observations: · When current flows along a wire, a magnetic field develops about that wire. · When two magnetic fields are close to each other, an attractive or a repulsive force is felt. So, if a wire carrying current is placed in a magnetic field, a magnetic field develops around the wire, and a force is exerted on the wire. The force is strongest if the wire is at 90° to the magnetic field. The force is also at 90° to the wire. If there is no angle between the wire and the field, there is no force. This is summarized in the diagram opposite; the wire would be forced directly upwards, away from the plane of the paper. If a loop of wire is placed in a magnetic field, the current direction is opposite on each side of the loop. This means that one side has an upward force on it, and the other side has a downward
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Clutches, Motors, And Solenoids
force on it. This causes the loop to rotate, as shown opposite. The part of the motor containing the loop of wire is called the armature. It is normally in the form of a drum, with many loops of wire wound around it for increased motor power. The armature is connected to the drive current by a split metal ring called the commutator, and a pair of brushes made from a low-resistance material such as graphite. Each segment of the commutator is insulated from the other. The commutator is split in a dc motor so that the polarity of the current flowing through the loop is reversed every 180° of rotation. This allows the rotation of the coil to continue; if there were no reversal of current, the coil would not rotate constantly.
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Clutches, Motors, And Solenoids
Brushless DC Motors
In the dc motor described above, the magnet is stationary while the coil rotates. In the brushless dc motor, the coil is stationary and the magnet moves. In a typical example, nine coils are attached to the motor drive board, arranged in a circle around the shaft. A circular magnet, com-posed of eight alternating north and south polarized segments, fits around the outside of these coils. The magnet is bonded to a metal cover, which is bolted to the motor shaft. As shown in the diagram, the coils are wired up so that there are three north poles, three south poles, and three neutral positions around the center. To rotate the magnet, the motor drive board switches the positions of the poles in such a way that the magnet is always pulled around in the same direction. Ricoh products primarily use two types of brushless dc motors--servomotors and stepper motors.
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Standard Components
Clutches, Motors, And Solenoids
Servomotors
Servomotors use feedback to maintain a constant rotating speed. To check that a dc servomotor is running at the correct speed, the drive board contains a circuit known as a phase-locked loop. An oscillator generates a reference frequency. The circuit board contains a detector that converts the motor's rotation into another frequency signal. The phase detector compares both signals; a feedback signal is sent to the motor drive board to adjust the motor speed until it reaches the correct value. When the motor is at the correct speed, the two frequencies are the same.
Rotor
Stator
A servomotor mounted on its controller board.
The same motor disassembled to show stator and rotor.
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Standard Components
Clutches, Motors, And Solenoids
Stepper Motors
Stepper motors are used whenever accurate positioning of a component is required. The outer shell of the motor is stationary. Coils are wound around teeth attached to this shell. The core of the motor, made of iron, can rotate. The arrangement of the teeth is such that, if pulses are applied to the coils in the correct timing sequence, the core of the motor can be rotated in stepwise increments of a few degrees. In the example shown here, when phase 1 is energized, two of the teeth on the motor core will align with the coils on the outer shell, but the other four teeth will be out of alignment. Then, if phase 2 is energized, the core rotates by 15 ° to align two of the other teeth. If phases 1, 2, 3, and 4 are energized in sequence continuously, the motor will drive the shaft in increments of 15 °. The order of activating the coils can be varied to give different effects, such as reverse motion, or coarser steps.
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Standard Components
Clutches, Motors, And Solenoids
The stator A typical stepper motor
The Rotor
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Standard Components
Clutches, Motors, And Solenoids
Solenoids
The solenoid is one of the oldest, simplest and most commonly used electromagnetic devices. It consists of a hollow electromagnet (coil) and a movable plunger that fits inside. When an electric current energizes the coil, it creates an electromagnetic force around the coil. This force causes the plunger to move into the coil. The picture to the right shows a disassembled solenoid. The amount of force created by a solenoid is in direct proportion to the amount of current applied. Some other factors, such as the number of turns in the coil, the magnetic character of the steel, and the stroke of the solenoid affect the amount of force produced. The solenoid drive circuit is similar to the drive circuit for and electromagnetic clutch as explained on an earlier page. Continued on the next page.
Coil Plunger
Plunger
Coil
Direction of motion
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Standard Components
Other Electrical Components
A typical application is shown to the right, where the solenoid's plunger is activating a mechanical paper feed mechanism. A pawl [A] is gripping the ratchet sleeve of a spring clutch [B], preventing motor drive from reaching the feed rollers [C]. When the solenoid [D] turns on, the plunger pulls the pawl away from the ratchet sleeve, and the rollers start to rotate. [C]
[B]
For More Information
For more information on solenoid theory, operation, and design, we suggest you reference What is a Solenoid at the web site of the Detroit Coil Company. (http://www.detroitcoil.com/whatis.htm)*. *We have no control over this web page. The content or location may change at any time.
[D] [A]
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Standard Components
Other Electrical Components
Other Electrical Components
Thermal Heads
Operation
The thermal head is the central component of the thermal printer. A thermal head consists of a row of heating elements. If a heating element is turned on, it will heat up. The heat from the element will make a dot on the thermosensitive printer paper. Roughly speaking, each element on the thermal head reproduces what was scanned by the corresponding element of the CCD at the transmitter. There are 8 heating elements for each mm across the thermal head. A4 [8.5"] thermal heads have 1728 elements, B4 [10.1"] thermal heads have 2048 elements, and A3 [11.7"] thermal heads have 2368 elements. Basically, the CPU clocks a line of data into a shift register in the thermal head. When the line is complete, the CPU sends a latch signal, then prints the line. Then the paper is fed forward one line, and the next line is printed in the same way. When printing a line, the CPU divides the line into 4 blocks. It prints the blocks one at a time. Each of these blocks is transferred to the printing elements using a strobe signal. Each block has a separate strobe signal.
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Standard Components
Other Electrical Components
The blocks are usually adjacent on the thermal head, but they do not have to be. In fact it is even possible to interleave the blocks, having an element from block 0 next to an element from block 1, then one from block 2, followed by one from block 3, then back to block 0 again, and so on across the thermal head. Data, latch, and strobe signals reach a decoder in the thermal head from the CPU. The + 24VD supply comes directly from the power supply; it is a separate channel from the + 24VD supply used by the rest of the machine. Serial data comes from the CPU on pin A (see the diagram on the previous page). In most models, for a black dot, A is high. The data is clocked into the shift registers (the clock is on pin B). When a line of data has been fed to the shift registers, the CPU sends a latch pulse (pin C) and the data moves into the latches. To print the line of data, the CPU sends strobe signals to the thermal head. First, the strobe signal for block 0 (pin D goes low) is sent to
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Standard Components
Other Electrical Components
block 0, and the data in the block 0 elements passes from the latch to the heating elements (for a black dot, the element is heated). After all elements for block 0 have been printed, pin D goes high again. Then blocks 1 (pin E), 2 (pin F), and 3 (pin G) are sent in sequence, in the same way as block 0. The duration of the strobe pulse determines how much an element is heated to make a black dot. The CPU monitors the thermistor on the thermal head (see section 3-5-4). The CPU calculates the strobe pulse width based on the thermistor reading and on the value for the pulse width entered using service mode when the head was installed. NOTE: In most models, the pulse width must be programmed using a service function after installing a new thermal head or system RAM board (called the MBU in most fax models). In a few models, the pulse width is programmed automatically.
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Standard Components
Other Electrical Components
1728 Heating Elements Block 0 Block 1 Block 2 Block 3
Internal Structure
The internal structure of the thermal head varies from model to model. However, two basic types have been used so far. These are the discreteelement control type and the block control type. In a thermal head using discrete-element control, each element has its own discrete clock, latch, and switching circuits. Each element also receives the strobe signal.
CPU FCU
24V Heating Element Circuit Element
Latch
Shift Register STROBE LATCH DATA CLOCK
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Standard Components
Other Electrical Components
In a block control type thermal head, driver ICs control a group of elements. For example, one driver IC may control 64 elements. The decoder sends a clock, latch, and strobe signal to each driver IC. Each driver IC contains shift register, latch, and switching circuits for the elements that it controls. A good thermal head will have a conductive cover that is grounded to prevent build-up of static, which would damage the driver ICs inside the thermal head.
1728 Heating Elements (27 driver ICs, 64 elements/driver IC) Block 0 7 Driver ICs Block 1 7 Driver ICs Block 2 7 Driver ICs Block 3 6 Driver ICs
24V
CPU FCU
Driver IC 64 Heating Elements LATCH STROBE
Latch CLOCK
DATA
Shift Register
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Standard Components
Other Electrical Components
LCDs
LCD is an abbreviation for Liquid Crystal Display. An LCD is a digital display that consists of two sheets of glass separated by hermetically sealed liquid crystal material. The liquid crystal is normally transparent. The outer surface of each glass sheet has a transparent conductive coating, forming front and back electrodes. On the viewing side, the conductive coating is arranged as either a matrix of dots (for example for a computer display) or character forming segments (for example the 7-segment display elements of a calculator). Leads at the edge of the display attach to the segments or the lines of the matrix. A voltage applied between the front and back electrodes, causes the liquid crystal molecules to change alignment and thus become reflective. The reflectivity of the liquid crystal segments can vary depending on the amount of voltage applied. Some LCDs depend on the reflection of ambient light for viewing. However, most larger displays use a backlight. The illustrations to the right show LCD displays used on model A201 (upper picture) and model A246 (lower picture).
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Standard Components
Other Electrical Components
Characteristics
· Lightweight and thin construction · Not naturally radiant, a light source is required. · More expensive than CRTs (Still true ... but prices are dropping.)
Applications
LCDs are used as display screens.
For More Information
For more information on LCD theory, operation, and design, we suggest you reference the following web pages: LCD Frequently Asked Questions. (http://margo.student.utwente.nl/el/misc/lcd_faq.htm)* Liquid Crystal And Other Non Emissive Displays (http://itri.loyola.edu/displays/c3_s1.htm)* *We have no control over these web pages. The content or location may change at any time.
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Standard Components
Consumables
Consumables
Photoconductors
The photoconductor--a photoconductive drum or belt is the heart of most imaging processes. The photoconductor's surface is where the latent image is formed and then developed. Photoconductors have the following characteristics: · · · They are able to accept a high negative electrical charge in the dark. (The electrical resistance of a photo-conductor is high in the absence of light) The electrical charge dissipates when the photoconductor is exposed to light. (Exposure to light greatly increases the conductivity of a photoconductor.) The amount of charge dissipation is in direct proportion to the intensity of the light. That is, where stronger light is directed to the photo-conductor surface, a smaller voltage remains.
Our products use two types of photoconductors. One type is a selenium based inorganic photoconductor. That type was used in the past for analog copiers. The other type is an organic photoconductor (OPC) that is used for analog and digital copiers, plain paper facsimiles, and laser printers. Recently, all such products use OPCs instead of inorganic photoconductors.
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Standard Components
Consumables
Organic Photoconductors (OPC)
An OPC consists of a CTL (charge transfer layer), CGL (charge generation layer), electrode layer, and a substrate to which the layers are bonded. (The electrode layer is also called the under layer.) Ricoh made OPCs have charge generation pigments and charge transfer compounds imbedded in the charge generation layer. These materials greatly improve the response characteristics of the OPC. For more information on OPCs, refer to Appendix 2-OPC.
CG material CT material Cross section of OPC layer Charge transfer layer
Charge generation layer
Electrode
Substrate
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Standard Components
Consumables
Selenium
Many of the copiers in the field use selenium drum photoconductors. These drums consist of a layer of selenium or a selenium alloy bonded to an aluminum base. Selenium drums have gone through several generations of development. However, the only types that you are likely to encounter in the field at present are types H and F. Type H has a layer of selenium-tellurium alloy bonded to an aluminum core. Type F has a layer of selenium-arsenic (actually Arsenic-Triselenide) bonded to an aluminum core. The F type drum is more durable and has greater spectral sensitivity. However, it is more expensive to make.
Selenium photoconductor types
Se-Te Layer
Type H
Al Sî`Ì Al Core (Base)
Se-As Layer
Type F
Al Core
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Standard Components
Consumables
The sensitivity of selenium changes slightly with variations in the temperature around the drum. This is especially true of type F drums. Under cool conditions, the drum may be excessively charged, resulting in drum has an internal over-toning of the copy image. To prevent this, many machines have a heater to warm the drum if it becomes too cool.
Selenium drum with a heater
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Standard Components
Consumables
Toner (Black)
Toner is a combination of plastic resins, dyes, waxes, flow agents, charge agents, and particles with magnetic characteristics (if magnetic toner). The plastic resins are the base ingredients of toner. They combine with some or all the other parts (sometimes with other additives) in a precise mixture with the proper charge, transfer, and fusing characteristics required for each type of toner.
Pigment and resin mixed together to form non-magnetic monocomponent toner
Non-Magnetic Monocomponent
All-in-One toner that contains blackened pigments for printing in a matrix of resin. This kind of toner usually comes in a cartridge and is used with nonmagnetic rollers. For this type of toner, a static charge picks up and holds the toner on the roller surface.
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Standard Components
Consumables
Magnetic Monocomponent
Similar to the non-magnetic toner, this type has iron oxide particles encapsulated in the resin matrix of each individual particle of toner. The toner itself isn't actually magnetic, but the iron particles in the toner make it possible for magnetic rollers to easily pick up and hold the toner particles. All monocomponent systems that use magnetic rollers must use this type of toner.
Pigment and resin
Particles of iron oxide
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Standard Components
Consumables
Dual Component
The toner used in dual component development systems is similar to the non-magnetic type monocomponent toner. This type of toner works with a separate particle known as a carrier. The mixture of toner and carrier is known as developer. The toner and carrier particles are held together by triboelectric charges. They develop opposite triboelectric charges due to mixing action in the development unit. The carrier rides on magnetic rollers and carries the toner with it to the photoconductor. The carrier itself is not transferred to the photoconductor, but merely releases the toner onto the photoconductor (which the toner is electrostatically more attracted to) and then returns to the hopper to pick up more. The carrier is normally an iron or iron oxide particle with a coating to improve durability. The illustration to the right shows the toner and developer particles used in F-type developer.
Toner and carrier of F developer Toner
Charge control material
Pigment Plastic resin base Coat layer (About 1µm thick)
Carrier
Core material (diameter of about 100µm)
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Standard Components
Consumables
Characteristics
There are three main characteristics of toner: its charge properties, fusing ability, and image capabilities.
Charge Properties
The charge is what enables toner to transfer from its container to the drum. If the toner is not charged properly, dirty background, toner blasting, or light prints may occur. The characteristics of toner charge depend on the toner particle size, shape, and composition. Friction generates a triboelectric charge on the toner particles. The charge generated for each particle depends on the surface area to mass ratio of each particle. This is determined by the size and shape of the particle. The smaller the particle the larger the ratio. The result is a stronger triboelectric charge for smaller particles. Particle sorting or printing defects can occur if toner particles are not uniformly sized. Therefore, the toner requires sifting several times after it is ground into a powder. Charge control material or "charging agents" are also important in that they help determine how well particles charge and if that charge is negative or positive.
Fusing Ability
Fusing requires very specific adhering and melting properties. Toner must melt at the correct temperature to be compatible with the fusing system it is in. The fusing rate is also an important part of fusing.
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Standard Components
Consumables
Toner must fuse quickly for high speed printers and slowly for lower speed ones. If the toner cannot meet these standards cold or hot offset may occur. This is a ghost image picked up on the fusing rollers. The plastic resins and various additives determine the fusing properties of the toner. Flow rate is also important because it determines the density of print. A toner that flows well produces higher density copies. Therefore, an optimum flow rate, where the toner is neither too much nor insufficiently fluid, is necessary. Toner composition, particle size and additives determine this rate.
Image Capabilities
If all of the previous characteristics are correct, a problem may still occur. This problem concerns resolution. High-resolution printers require micro fine toner, usually around 6 microns or less. If the toner particles are larger than this, the resulting image will not have the razor-sharp quality the user desires from their high-resolution printer. The size of the particle will also effect the density of the image and limit the number of shades the printer can produce. Printing black dots in white areas produces shades. The blackness of the dots is always the same; they appear darker or lighter depending on how closely grouped. For example, if the user selects 100 dpi as the desired shading, but the particles are too large, the toner will not stay within the boundaries of the dot size. This results in an overflow past the boundaries, filling in more of the area. Consequently, this produces a shade darker than desired by the user. This is how large sized toner particles limit the shading spectrum of high-resolution printers. The production of smaller, micro fine particles create new challenges. The smaller particles will have different charge and flow characteristics that must be handled properly.
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Standard Components
Consumables
Paper
Paper isn't a consumable part of office machines, but as copiers, printers, and fax machines all have to handle paper in various ways, paper is an integral part of their operating processes. In this section we will take a look at the properties of paper that effect the operation of our machines. Except where stated otherwise, we will use the term copier paper to include paper for plain paper faxes and office printers.
Summary
Properties important in copier papers include weight, size, stiffness, smoothness, electrical resistivity, porosity, coefficient of friction, and moisture content. Some properties are important to copy quality others affect paper handling reliability. Image density and fusing are improved on smoother papers. Paper handling reliability and less background toning are obtained with rougher papers. Increasing resistivity improves density but also increases the tendency toward static, background toning, and feathering.
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Standard Components
Consumables
Paper Weight
There are three commonly used systems for classifying paper weight. They are summarized in the following table. Papers with weights at the extreme low and extreme high levels of a machine's specified tolerance range will tend to jam more frequently. System International (ISO) system US (lb) system Japan (kg) system Paper weight definition The weight in grams of a single one square meter sheet of paper. The units are grams per square meter (g/m2) The weight of 500 17" x 22" sheets of paper. The units are pounds (lb).* The weight in kilograms of 1000 788 mm x 1091 mm sheets of paper. The units are kilograms (Kg). Where it is used Most of the world
USA Japan
*This applies to Bond paper only. See the discussion of US paper weights below. Since the paper weights are defined differently, you cannot convert directly between them. The conversion factors are as follows: lb " g/m2 lb " Kg x 3.760 x 3.233 g/m2 " Kg g/m " lb
2
x 0.860 x 0.266
Kg " g/m2 Kg " lb
x 1.163 x 0.309
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Standard Components
Consumables
Paper Weights in the United States
In the United States, paper weight specification is a real dog's dinner. Weight depends on classification. Sheets of paper that are actually exactly the same can have different weight specifications if they are from the different classes. The problem is that paper weight is measured by weighing 500 full sheets of paper. This is referred to as the "standard ream weight". So far so good, but now the fun begins. The size of a full sheet of paper is different for different types of paper! Some commonly used paper types are bond paper, book paper, card stock (or index stock), and cover stock. Lets take for example bond paper and book paper. A full sheet of bond paper is 17 x 22 inches. (A full sheet of bond is the equivalent of four sheets of 8½ x 11 inch paper.) A full sheet of book paper is 25 x 38 inches. So if you took 500 full sheets of book paper that was the equivalent of 20 lb Bond paper, it would weigh more. Standard 20 lb bond paper is actually the same as 50 lb book paper. For copiers, paper specifications are written in bond weights. So, if a machine can copy on 14 to 42 lb bond paper, it will accept from 40 to 100 lb book paper. Confusing isn't it?
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Standard Components
Consumables
Paper Sizes
International Paper Sizes (ISO)
The ISO (International Organization for Standardization) paper sizes, which were based on the earlier DIN (Deutsche Industrie Norm) sizes, are commonly used everywhere in the world except Canada and the United States. The following table lists the sizes that can commonly be expected to be used in copiers.
ISO A Series A0 A1 A2 A3 A4 A5 A6 A7 841 x 1187 594 x 841 420 x 594 297 x 420 210 x 297 148 x 210 105 x 148 74 x 105 B0 B1 B2 B3 B4 B5 B6 B7 ISO B Series 1000 x 1414 707 x 1000 500 x 707 353 x 500 250 x 353 176 x 250 125 x 176 88 x 125 ISO C Series C0 C1 C2 C3 C4 C5 C6 C6 917 x 1297 648 x 917 458 x 648 324 x 458 229 x 324 162 x 229 114 x 162 81 x 114
For More Information
For a detailed discussion of the concepts behind ISO paper sizes refer to Markus Kuhn's web page on international standard paper sizes. (http://www.cl.cam.ac.uk/~mgk2 5/iso-paper.html)* *As we have no control over this web page, The
content or location may change at any time.
Sizes are in millimeters
Multiplying the 0 sizes creates large format sizes. For example, 2A0 = 1189 x 1682 and 4A0 = 1682 x 2378
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Standard Components
Consumables
Paper Sizes in the USA
Many paper sizes are in use in the United States. Copy paper sizes are defined in inches; the most commonly used sizes also have a name (letter, ledger, etc.). US paper sizes are also used in Canada; however, there they are usually defined in millimeters. The table to the right gives the copier paper sizes most commonly used in the USA. Size in Inches 4¼ x 5½ 5½ x 8½ 8 x 10½ 8 x 13 8½ x 11 8½ x 14 11 x 14 11 x 17 17 x 22 22 x 34 34 x 44 Size in mm 108 x 140 140 x 216 203 x 267 203 x 330 216 x 279 216 x 356 280 x 356 279 x 432 432 x 559 559 x 864 864 x 1118 Statement Government letter Government legal Letter Legal Computer Ledger Common Name
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Standard Components
Consumables
Japan JIS B Sizes
Japan has developed its own standards for paper sizes. While the JIS (Japan Industrial Standard) A series of sizes is identical to the ISO A series of sizes, the JIS B series is not. Also, Japan has no series of envelope sizes comparable to the ISO C series.
JIS B Series B0 B1 B2 B3 B4 B5 B6 B7 1030 x 1456 728 x 1030 515 x 728 364 x 515 257 x 364 182 x 257 128 x 182 91 x 128
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Consumables
Paper Characteristics
The following table summarizes the most important paper characteristics (other than weight and size). Brightness The brightness of a paper is a measure of its light reflectivity. A high grade paper usually has a brightness in the 85 ~ 90% range. Low grades would be in the 70 ~ 75% range. A high grade looks bright (white) and a low grade dull (gray). This is a measurement of the incident light that is reflected from the paper's surface. The coefficient of friction directly affects the efficiency of paper feeding. It must be high enough that the feed and transport rollers can get a good grip. However, it must be low enough that the sheets of paper slip over each other. Also, the coefficient of friction should not vary from sheet to sheet as variations in friction could cause multi-feeds and jams. Curl in paper is a major cause of transport problems resulting in misfeeds. Basically, copier paper should be manufactured to remain as nearly flat as possible while It is subjected to varied temperatures and humidity changes as it proceeds through the copy making process. Paper in a copier's paper tray tends to curl as it picks up moisture from the air. Some machines, especially higher speed models, have heaters in the paper trays to prevent such curling. If paper resistivity is too high it can cause static build-up that results in double feeding and jams. Too low an electrical resistivity (= higher conductivity) can cause image deletion (blank areas) as well as jams. Resistivity is affected by moisture and paper composition.
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Coefficient of friction
Curl
Electrical Resistivity
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Standard Components
Consumables
Moisture content
Opacity
Porosity Shade
Smoothness
Moisture content directly affects paper transport, copy quality, and curl. The generally acceptable range is 4 ~ 6 percent moisture. A higher moisture content will cause curl, a higher jam rate, poor image transfer (due to lower resistivity), and poorer image fusing. A lower moisture content causes static that results in misfeeds and double sheet feeding. Paper must be sufficiently opaque to prevent image show through. This is especially important in paper used for duplexing. Most brands of paper use some kind of filler to enhance opacity. The composition of the filler can affect copier performance and durability of parts. Some common fillers are clay, chalk, and marble. Mottling and smearing can result from excess porosity. Low porosity paper tends to have more curl and is prone to image smearing. Shade will vary from a pure white to tints in the blue, pink, or yellow ranges. Shade is a personal preference but also may vary between lots of paper or within a brand. Close control of shade is most important for papers used in color printing and copying. Smoother papers increase electrostatic adhesion at the image transfer step. This is because closer contact with the photoconductor makes the paper more difficult to strip from the photoconductor. Smoother papers are also more likely to have background toning. Too rough a paper may cause image mottling, poor image fusing, and high toner consumption.
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Standard Components
Consumables
Stiffness
Surface condition
Thickness
Paper stiffness is classified by cross grain and with grain. The stiffness is a result of the orientation of the fibers within the paper. In most copier papers, the fibers are orientated in the length direction of the paper Stiffness affects paper feeding and transport in copiers and laser printers. Paper is generally two or three times stiffer in the with grain direction than in the cross grain direction. Paper finishing and surface properties have an impact on long-tern satisfactory performance of copier equipment. Copier papers should be tightly controlled to eliminate such problems as: · Dirt and dust--which can cause reduced machine reliability, misfeeds, and copy quality defects. · Surface inclusions--which can result in poor copy quality, sheet weakness, and transport problems. · Torn and wrinkled sheets--which can cause poor transport, misfeeds, and machine damage. Paper thickness is measured in micrometers. Typical copy paper has a thickness of about 95 micrometers. For copy paper, thickness is a direct function of paper weight; so, for our products, generally only paper weight is specified.
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Standard Components
Consumables
The following table gives Ricoh Standards (= ideal paper) for some selected paper characteristics. (Not all possible paper characteristics are included.) Item Weight Thickness Stiffness Brightness Smoothness Ash content Moisture Resistivity Units g/m2 µm -- % S % % cm Standard B/W 69.5 ±4.0 92 ±6 Color 80.0 ±4.0 95 ±6
With grain: 55 With grain: 55 Cross grain: 28 Cross grain: 28 80 Front: 60 ±20 Back: 50 ±20 1~5 4.0 ~ 6.0 8 x 10 ~2 x 1011
9
82 120 +40/-35 (front and back) -- 4.0 ~ 6.0 8 x 109 ~6 x 1010
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