GB2066737A - Copying apparatus - Google Patents

Abstract

Copying apparatus includes a processing unit for forming a picture on a copy material, a process control for operatively controlling the processing unit, a manual power switch unit 39 for supplying power to electric loads of the processing unit and the process control, the manual power switch unit including a handle 201 to hold an On condition during the time from the beginning of manual turning on to the activation of manual turning off and a coil 207, 208 to release the On condition of the handle before the activation of the manual turning off, and a power control for driving the coil to release the handle from the On condition to the Off condition after a predetermined time has elapsed since a completion of copying operation, the power control including a timer controlled by the process control for driving the coil. Alternatively or additionally the power control may drive the coil upon reception of a signal indicating a fault or malfunction e.g. overheating of a fuser, overcurrent in the circuitry. <IMAGE>

Description

SPECIFICATION Image forming apparatus This invention relates to an image forming apparatus, such as a copying apparatus and is more particularly concerned with means provided in such apparatus for switching the power supply.

In addition to a copy start switch, a conventional copying apparatus normally has a main switch for the supply of power to the various different electric loads for performing such processes as charging or exposing and to control unit which is provided to effect a timing control for the loads. Various other electric loads are normally activated by the main switch to operate a cooling fan or set a copying apparatus in a ready condition for "copy start".

However, those electric loads are frequently deenergized automatically after completion of copying so as to minimize noise caused by the fan and to reduce power consumption. The main switch is therefore so constructed to be activated only by the operation of a manually operable element, such as a button, and thereafter a relay holds a power line which is shut off by releasing the relay after the completion of copying.

The state of the power supply to the apparatus is commonly assessed visually by an operator by noting the position of the manually operable element (hereinafter referred to as the handle) of the main switch. The operator would therefore be uncertain of the power supply state if the handle position did not indicate definitely one or other of the on and off states. However, the provision of an additional "manual off" switch for the manual release of the relay would make the apparatus construction complex. Certain conventional forms of apparatus include an exclusive safety circuit or a protection circuit to avoid malfunction in the apparatus and to suppress overcurrent on the AC line.

It is an aim of the invention to alleviate the above-mentioned drawbacks in an image forming apparatus having a manual power switch.

In one aspect the invention provides a copying apparatus adapted for automatic shut off or manual off control by using a timer after completion of copying without mounting thereon ga manual power switch for off only.

In another aspect the invention provides an image forming apparatus adapted for power autoshut control by controlling a manual power switch and for protecting the control means from being overheated.

In a further aspect the invention provides an apparatus adapted for manual power on-off and auto-shut control by means of a power switch unit including a handle and control coil therein.

In yet another aspect the invention provides an auto-shut mechanism responsive to a malfunction that occurs therein.

In a further aspect, the invention provides an image forming apparatus having a power switch unit including a first coil and second coil and operable to achieve power-off in response to the coil current in one of such coils.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings, in which: FIGURE 1 is a sectional view of a copying apparatus according to the invention; FIGURE 2 is a plan view of the control section illustrated in Figure 1; FIGURE 3 is a control circuit diagram of the copying apparatus; FIGURE 4 is an operation time chart of the apparatus illustrated in Figure 1; FIGURES 5 through 7 are other control circuit diagrams of the apparatus; and FIGURE 8 is a sectional diagram of the power switch unit illustrated in Figures 1, 3 and 5 through 7.

A copying apparatus according to the invention is illustrated in Figure 1 and comprises a reciprocable platen 1 for supporting thereon an original to be copied, a rotatable drum 2 having a sensitive film coated on its peripheral surface, a lamp 3 for illuminating the original so as to expose the drum 2 to an image thereof, a corona charger 5 mounted to provide a positive charging for the surface of the sensitive film, another corona charger 6 adapted to provide a negative charging for the surface of the sensitive film simultaneously with the image exposure, a developing device 8 provided to develop a static, latent image, a charger 9 provided to effect the transfer of the developed images to a copy paper 10, a removable cassette 11 provided to accommodate therein a multiplicity of copy sheets 10, a feed frame 12 for permitting manual feeding of the copy sheets 10 into the apparatus, a roller 13 adapted to feed the copy papers from the cassette, a roller 14 adapted to feed the copy sheets from the manual feed frame 12, microswitches 1 5 and 16 provided to detect the manually feed copy sheets, a registration roller 1 7 mounted to align the front end of the copy paper with the edge of a drum, a roller 18 provided to separate the copy paper from the drum, a belt 19 adapted to convey the copy paper, a fixing roller 20, a roller 21 mounted to discharge the copy paper to a tray 22, a blade cleaner 23 for removing the toner remaining on the drum, a magnet roller 4 adapted to collect the toner being removed with the blade 23, a container 7 provided to accommodate therein the toner collected by the roller 4, a negative corona charger 24 mounted to remove the residual charge on the drum, a shutter 25 adapted to permit direct exposure of the drum surface to the light from the exposure lamp 3 during a predetermined period, mirrors 26 and 28 mounted to reflect the light from the lamp 3 directly to the drum surface and a selhock lens 27 provided to focus the reflective light from the manuscript exposed to the lamp 3 on the drum surface.

When the main switch is turned on, a motor for driving the drum 2 also is turned on, the lamp 3 is energized the shutter 25 is opened and the drum 2 is driven while turning the corona charger 6 on.

The drum surface is thereby cleaned of residual toner, residual charge and any conductivity pattern remaining memorized thereon. A fixing roller 20 generates a recopy start signal as the temperature of the fixer reaches an appropriate level by utilizing an internal heater. The drum continues to rotate unless a copy switch is turned on, and the rotation of the drum is suspended when the pulses from a rotary encoder provided in a drum driving system to generate n units of pulses every one rotation of the drum are counted by a predetermined number. The drum rotation as described above is termed "first prerotation".

When the copy switch is turned on during the rotation or suspension of the drum, the shutter 25 is closed, the drum 2 resumes its rotation, the platern 1 advances after substantially one rotation (hereinafter is termed "second prerotation") to provide for the manuscript loaded on the platen 1 slit exposure. The reflecting picture due to the lamp 3 is slit-exposed through the Selhock lens on the drum. The sensitive film coated on the drum 2 includes the upper insulation layer, the intermediate photo conduction layer and the bottom conduction layer and, when the surface charged with the charger 5 reaches the exposure surface, the positive charging may be electrically cancelled by the negative charger 6 and photo picture.When the full surface of the sensitive film meets with the exposure face, a static latent image having a high contrast is formed on the drum surface by the light from the mirror 26. The latent image appears as a positive image in the developing section by receiving the toner. The positive image is transferred in the transfer section to the recopy paper in accordance with the positive potential level of the transfer charger. The copy paper is separated from the others in the cassette 10 by the timing operation of the paper feeding roller 1 3 to be fed as desired and passes through the transcription section at the same speed as the drum rotation by the registration roller 1 7. The transfer paper is separated in the roller 18, is fed from the belt 19 to the roller 20 for image-fixing and is discharged by the roller 21 to the tray 22.After completion of the transfer operation, the drum surface is cleaned continuously by the blade 23, is electrically cancelled by the charger 24 and is memoryremoved by the light from the lamp 3 through the mirror 28. In order to effect continuous recopying from the same original, the reciprocal movement of the platen 1 is repeated according to the number set by a ten key array 42 in the operating section of the apparatus.

Figure 4 is a time chart showing the timing relationships between the actuation of the various components in a copying operation of the apparatus.

Referring now to Figure 2 illustrating the operation section of the recopying apparatus, there is provided an electric source switch 39 (main switch), a key switch 40 for copy start, a stop key switch 41 for interrupting a continuous copying, a ten key array 42 for entering the copy number when multiple copying is required, this copy number to be stored in a memory, a clear key 43 for clearing the number stored in the memory, a lever 44 for setting the density of the copying, a 7 segment indicator 45 for displaying the memorized copy number, a wait lamp 46 for indicating whether or not the fixing roller has reached a predetermined fixing temperature, a lamp 47 for displaying the absence of the cassette or the sheet therein and a lamp 48 for indicating that the container 7 for collecting toner is full. A lamp 49 is turned on when the copying sheet causes jamming.When jamming occurs, the clear key and keys 42 cannot be operated, but they can be operated in the waiting period while the fixing roller heats up.

The segment indicator 45 is so constituted that one suppressed by a zero can be indicated independently of the waiting duration by turning on the electric source switch 39, and further, a number reduced by one from the setting number is indicated every completion of one copying and when a preset number of copyings have been completed, the indication of the preset number is resumed, whereby gaining a desired number of copyings without supplying of the power to the ten key. If thirty seconds have passed without starting the copying thereafter, the numeral one is indicated on the indicator 45. By the method as described above, the operation can resume the copying without presetting a predetermined number of the ten key and accordingly the resumption of the smooth copying can be expected.When the standby time of thirty minutes has elapsed after the thirty seconds stated above, the main switch 29 is automatically shut off as described later.

The wait display unit 46 blinks by turning on the source switch 39, but when the temperature of the fixing roller is not lowered below a fixing possible level, namely in a short time after the operator has turned the source switch 39 off, the display unit is statically lighted. On the other hand, the unit 46 would blink at a temperature lower than the fixing possible level. It is to be noted that the display unit 46 is lighted stably also when the temperature of the fixing roller is increased up to the fixing possible level and the wait time has passed.

When the source switch 39 is turned off, the display unit displays only an off-condition of the power source without displaying a lighting or blinking condition.

An overflow indicator 48 is used for performing a significant display by detecting the overflow condition in the container 7 and for achieving a static lighting display by detecting shortage of the toner in the container 33 for developer. It is however understood that in the former case, the lamp can be turned on or off, while in the latter it can be statically lighted. A no paper display unit 47 can also be turned on or off in the absence of paper, while it can be statically lighted in case of no cassette.

If shortage of the toner in a hopper 33 or overflow of the collecting container 7 may be detected, the copying is continued until a preset number of copyings will be completed when the continuous copyings of the number preset by the ten key are executed, and thereafter the resumption of the copying is prevented. Such an operation is performed to cover the weak point in that an alarming is issued, but a substantial eopying speed may be decreased because a series of copying operations are disturbed by instant interruption thereof.

Figure 3 is a control circuit diagram of the copying apparatus, in which the main switch 39 is a unit including the switch contacts and various windings. The unit 39 has an overcurrent detecting winding 1 50 and switch contact 1 52 and is so operated that the contact 1 52 is forcibly opened by excitation of the coil 1 50 (first coil) when the overcurrent greater than a predetermined level may be applied thereto. The main switch unit 39 has also a function of breaker therefor. The main switch unit 39 additionally has a winding 151 for external trip, being excited as by the winding 1 50 by supplying the current to the winding 151 and the switch contact 152 can be forcibly opened before the manual off operation.

Therefore, the main switch can be automatically cut off. However, the switch contact 1 52 also is actuable by manual operation, a manually operable element being accessible from the exterior of the apparatus housing.

HVT indicates a high tension transformer for impressing a high voltage onto the chargers necessary for the copying operation, L101 through Ln indicate such the load as a main motor or a fan motor for driving the drum and/or roller. LVT indicates a low tension transformer for reducing the voltage of 50 He/100 V, CV is a stabilized electric source for constituting various D.C. source Vb, Vc and Vcc obtained by regulating stabilizing the voltage from the LVT, rectified by a recitifier Rec and CPU is a central control unit having a known microcomputer COM, which is provided to achieve the timing control of the loads to promote the copying action as shown in the time chart of Figure 4 and store in a memory a key signal entered from the operation unit 102 illustrated in Figure 2.CNT is a counter for counting a clock pulse CL impressed from the CPU thereto through a line 121 and serves to set the counter during the time at which a signal is being applied to a reset terminal RST. The clock pulse CL frequency demultifies a pulse from an oscillator of 1,usec for promoting running of the microcomputer ,uCOM and thereafter is issued from the same. Q1 01 is a driver having an amplifier, for driving the winding 151.

However, the microcomputer ,uCOM is provided with a memory ROM in which are stored a program for achieving the time control of sequence in Figure 4, a key entry program and a program for controlling the start and completion of the sequence by using an entry signal. A power source for the COM is indicated at Va.

When the main switch contact 1 52 is turned on, to throw the power source to the LVT, D.C.

source Vc, Va and Vcc generated through the stabilizing source CV are applied to the CPU, counter CNT and operating unit 102.

Subsequently when an active copy key 40 is turned on, an on signal is applied to the CPU which discriminates the on signal to be processed to supply a control signal for cycle start to the loads desired through the lead 120 and copying operation starts by turning on a lamp 101, main motor My 01, high voltage output components. A copy signal CPS is applied through the lead 122 to the reset terminal of the counter CNT, together with the output signal of the lead 120 to reset the counter CNT in an initial condition.

During the copying operation or the main motor is driven, the copy signal CPS is applied to the reset terminal RST and during that period the counter CNT holds a reset condition.

When the copying has been completed and the main motor is turned off after passage of a standby mode T1, the said copy signal CPS is turned off. After that time, the counter CNT begins counting of the clock pulse CL. After completion of the copying, in not resuming the copying, when the counting number of the counter becomes equivalent to the count number corresponding to a preset time, a count-up signal is applied from the counter CNT to the driver Q101 to turn on the tripping winding 151 and cut off the contact 152 of the main switch 39. Therefore, it is to be noted that the apparatus can contribute to energy saving by turning off the power for the fan or the heater and remove the noises due to the fan or the like.

When the power source is thrown in by turning the switch 152 on again, the copying can be resumed because the main motor is driven and the counter CNT is reset by the RST. However, when the copy key 40 is not turned on as shown in Figure 4, the main motor is automatically suspended after passage of a predetermined time T2. Therefore, the counting starts because the resetting of the counter CNT is released and the counter effects the auto-off control of the switch 1 52 as described above.

However, the resetting of the counter CNT can be performed by a key input signal of the operation unit even during counting of the clock CL. The circuit for the above resetting can be established by applying a key input signal KIS according to the ten key and copy key through the lead 123 to the reset terminal as shown in the dotted line of Figure 3. The power source is cut off as in not turning the copy key on for a predetermined time after activation of the ten key.

According to such a processing, the operative characteristics can be further improved in that even when the copying is not effected, the counter can be reset by the key activation and the counting starts when the machine may be completely free from the operation by an operator, When the main motor is suspended to interrupt the copying because of the jamming or the absence of a copy paper, the resetting condition can be maintained because the copy signal CPS has still remained resided. The preset copying number can be held also when the operator would want to preferentially copy a specific paper sheet in the course of the copying, but the counter remains reset because the signal CPS is not cancelled in the case described above.After releasing of the jamming or release of the CPS due to a clear key during interruption of the copying, however, a counting of the timer CNT starts and the aforementioned auto-shut is established by count up.

In this apparatus as described above, the main switch is automatically cut off directly without using any relay. Therefore, the performance having a high reliability can be obtained with cheap components. It is also noted that the power supply to the control coil 151 in the main switch is automatically cut after turning off of the auto-shut to prevent heat generation of the coil.

A circuit illustrated in Figure 5 is provided to excite the winding for forcibly opening the main switch by detecting a rising of the source voltage and includes a rectifier Rec 2, fault detecting resistor R1 and R2, a constant diode Q104 used for standard voltage source, a comparator Q1 03 and an or gate 0102.

A circuit illustrated in Figure 6 is utilized to excite the winding for forcibly opening the main switch by detecting rising temperature of the fixing roller and has a thermistor provided close to or in contact with the first roller to detect a temperature of the fixing roller as shown in Figure 1 and a control circuit TC for controlling a heater provided in the roller at a predetermined temperature level.

A desirable objective can be established by replacing the circuit shown in Figures 5 and 6 with a circuit X of Figure 3 and the safety characteristic of the apparatus can be remarkably improved by connecting all the components to be detected to the or gate 0102.

Referring now to Figure 5, when the source voltage may be over a predetermined voltage level, the comparator Q103 recognizes that the divided voltage due to the resistor R1 and R2 may be higher than the voltage across the diode 0104 and the power is supplied to the or gate Q102 to forcibly cut off the main switch 1 52. After the cut off of the main switch, if the voltage is not returned to a normal level, the main switch remains cut off in spite of its throwing. If the voltage level may be at the normal level, the main switch can be thrown in. When the stabilizing circuit CV may vary over a stabilization controllable region, therefore, a protection for the circuit can be achieved and the circuit becomes more safe.

In Figure 6, with the thermistor 200 positioned near the lamp 5 or platen glass 1 to detect the temperature of the platen raised by the heat from the lamp, it is possible to protect the glass from being broken down by opening the main switch.

A circuit illustrated in Figure 7 is different from that shown in Figure 3 and is constructed so that the power source Va for the CPU can be obtained from the component other than the main switch unit 39, taking into consideration its position to maintain the active condition of the CPU regardless of the cut off of the main switch.

Therefore, the measurement or display on the operation suspending time of a machine, for example, even during interruption of the copying can be performed and the resumption of the operation be executed more smoothly. DSW is, used for a door switch to turn the machine off in opening the side plate of the machine and can cut off the power source provided in the machine when the jamming is removed. Though it is dangerous that the door switch DSW is interposed between the HVT and LVT2, it can be only used to turn the power supply off.

Figure 8 is a sectional detailed diagram of the typical power switch unit 39 illustrated in Figures 3 and 5 through 7. However, the power switch unit 39 in the same figure is in a power off condition and the machine is turned on by operating a handle 201 to an arrow mark direction.

A ring 221 is provided to make a rotation by action of the handle 201, a contact 217 is operated by the revolution of the ring, a contact 218 is used for a contact for performing power supply in contact with the contact 217, and the power switch unit 39 includes additionally the first coil 207 (151), the second coil 208 (150), a movable core 209 and an armature 204. When the handle 201 is moved to the arrow mark direction, the core 209 is elevated upward by the drive current of the coil 207 and the over current of the coil 208, as a result of the inductance is therethrough increased and the exciting force due to the coils also increases. The armature 204 is attracted to drive the ring 221 and contact 217 to a direction opposite the arrow mark. Accordingly, the handle 201 is returned to a position illustrative and the A.C. line is shut off. Because no current is applied to a control port Y by interruption of the power supply to the A.C. line, the excitation due to the coil 207 and 208 may be faded away from the armature 204 is returned to the position illustrative. It is therefore possible to protect the coils from being over-heated. And also the contact 217 and 218 can be freely switched on or off by the action of the handle 201 indepedently of the armature. The handle 201 can also be constructed in a momental button type.

Claims (10)

1. A copying apparatus comprising a process means for forming an image on a copy medium, a process control means for operatively controlling said process means, a manual power switch unit for supplying the power to the electric loads of said process means and said process control means, said manual power switch unit including a manually operable element arranged to hold an on condition during the time from the beginning of manual turning on to the activation of manual turning off and a coil arranged to release the on condition of said element before the activation of the manual turning off, a power control means for driving said coil to release said element from the on condition to the off condition after a predetermined time with completion of copying operation and said power control means including a timer means controlled by said process control means for driving said coil.

2. A copying apparatus as claimed in claim 1 including a process of preventing the operation of said timer means during interruption of copying operation.

3. A copying apparatus as claimed in claim 1 wherein said process control means has a clock pulse generating means and said timer means counts a clock pulse from said pulse generator to drive said coil.

4. A copying apparatus as claimed in claim 1 wherein said power switch unit has a second coil additionally to shut out said handle automatically by the overcurrent passing through said second coil.

5. An image forming apparatus comprising a process means to form an image on a copying medium, a process control means for operatively controlling said process means, said process control means including a microcomputer for achieving a timing control for said process means, a manual power switch unit for supplying the power to the electric loads of said process means, said manual power switch unit including a means responsive to manual activation, a first and second coil for releasing said response means, said second coil responsive to the overcurrent on A.C.

line and a power control means for driving said first coil to release said handle automatically after completion of picture forming process or after occurrence of malfunction.

6. An image forming apparatus as claimed in claim 5 wherein said process control means includes a microcomputer and a power supplying to said computer is continued independently of driving said coils.

7. A copying apparatus comprising a process means for forming an image on a copying medium, a process control means for operatively controlling said process means, a manual power switch unit for supplying the power to the electric loads of said process means and said process control means, said manual power switch unit including a manually operable element arranged to hold an on condition during the time from the beginning of manual turning on to the activation of a manual turning off and a coil to release the on condition of said element before the activation of the manual turning off and a power control means for driving said coils to release said element from the turning on to the turning off by detection of a malfunction occurring in said apparatus.

8. A copying apparatus as claimed in claim 7 wherein the occurrence of said malfunction is caused by an abnormal rising of the temperature in an exposure means or a fixing heater.

9. A copying apparatus as claimed in claim 7 wherein said power switch unit includes a second coil to shut off said handle automatically by the overcurrent passing through said second coil.

10. An image forming apparatus substantially as hereinbefore described with reference to the accompanying drawings.