Patent Publication Number: US-6334719-B1

Title: Stencil printer having a power saving mode

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a stencil printer capable of printing an image on a paper or similar recording medium with a master wrapped around its ink drum. More particularly, the present invention relates to a stencil printer including a power save mode for saving power when it is not used. 
     A digital stencil printer is conventional which uses a laminate thermosensitive stencil made up of a thermoplastic resin film and a porous support adhered to each other. The printer includes a thermal head for selectively perforating, or cutting, the resin film of the stencil with heat in accordance image data. After the perforated stencil or master has been wrapped around an ink drum, ink feeding means arranged in the drum feeds an adequate amount of ink to the inner periphery of the drum. A press roller, press drum or similar pressing member presses a paper or similar recording medium against the ink drum so as to transfer the ink from the drum to the paper via the porous portion of the drum and the perforations of the master. As a result, an image represented by the image data is printed on the paper. A modern stencil printer is capable of performing a continuous sequence including master making, used master discharging, paper feeding and printing steps. This, coupled with the increasing resolution and reducing performance cost, has recently motivated users of the kind producing, say, ten or more copies at a time to use the stencil printer in place of a copier. 
     Now, it is not unusual that a stencil printer or a copier is simply left unused over a long period of time with its power switch turned on, meaning that the actual operation time thereof is short. Even when the printer or the copier is unused, power is wastefully fed to its various drivelines, sensors, and a control panel. To solve this problem, the power switch may be turned off while the printer or the copier is not used. However, a heater for fixing a toner image is essential with the copier. Should power supply to the heater be turned off, it would take several minutes for the heater to be again warmed up to its operative temperature, delaying the first print time. 
     In light of the above, Japanese Patent Publication No. 5-31141, for example, discloses a copier having a power save mode for saving power when it is not used. 
     On the other hand, it is a common practice with a stencil printer, which does not need the above heater, to turn off its power switch when the printer is unused. This, however, brings about the following problem to be solved. In a stencil printer capable of continuously performing master making, used master discharging, paper feeding and printing steps, sections for executing such steps include a plurality of sensors for monitoring, e.g., the size of documents and that of papers, the position of the leading edge of a master, the position of an ink drum, and the position of a compresser for compressing a used master removed from the ink drum. It follows that every time the power switch is turned on, various members including the ink drum and compressor must be returned to their home positions all over again, delaying the first print time by about several ten seconds. 
     A section included in the stencil printer for feeding papers has traditionally been implemented by a fixed size system or a cassette system. Likewise, a section for discharging the paper or printing has conventionally included side fences which are moved by hand in matching relation to a paper size. Japanese Patent Laid-Open Publication No. 5-124737, for example, proposes a paper feeding system capable of sensing the size and the remaining amount of papers and automatically replenishing and feeding the papers. Also, Japanese Patent Laid-Open Publication No. 10-1254, for example, teaches a paper discharging section capable of automatically moving the side fences in matching relation to a paper size. These automatic paper feed and paper discharge schemes, however, aggravate power consumption when the stencil printer is not used. 
     Further, a personal computer, sorter or similar peripheral unit is often connected to the stencil printer for causing the printer to operate by sending image data via the peripheral unit. In this condition, maintaining the power switch of the printer turned off is not practical, and a configuration for saving power in the stand-by state of the printer is desired. 
     Technologies relating to the present invention are also disclosed in, e.g., Japanese Patent Laid-Open Publication Nos. 6-293175, 7-143746, 7-186492, and 8-251317. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a stencil printer having a power save mode for saving power when it is in a stand-by state, and preventing the first printing time from being delayed when it recovers from the power save mode. 
     In accordance with the present invention, a stencil printer for printing an image on a recording medium with a master wrapped around its ink drum and having a power save mode for saving power when it is not used includes a storing section for storing the conditions of the printer when the power save mode is selected. When the power save mode is selected, a comparing section compares the conditions stored in the storing section and the current conditions of the printer. 
     Also, in accordance with the present invention, a printing method for causing a stencil printer to print an image on a recording medium with a master wrapped around an ink drum, and including a power save mode for saving power when the printer is not used includes the steps of storing the conditions of the printer when the power save mode is selected, and comparing, when the power save mode is cancelled, the conditions stored and the current conditions of the printer. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description taken with the accompanying drawings in which: 
     FIG. 1 is a view showing a stencil printer embodying the present invention; 
     FIG. 2 is a plan view showing a specific configuration of a control panel included in the illustrative embodiment; 
     FIG. 3 is a block diagram schematically showing a control system also included in the illustrative embodiment; 
     FIG. 4 is a schematic block diagram showing electric circuitry of the illustrative embodiment more specifically; and 
     FIG. 5 is a view showing a sorter or peripheral unit applicable to an alternative embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to FIG. 1 of the drawings, a stencil printer embodying the present invention is shown and generally designated by the reference numeral  1 . As shown, the stencil printer includes a casing  9  accommodating an image reading section  2 , a paper feeding section  3  or multistage paper feeding device  3 , a master making section  4 , a printing section  5 , a paper discharging section  6 , a master discharging section  7 , and a control section  8 . 
     An image reading section  2  is mounted on the top of the casing  9  and includes a glass platen  10  on which a document is to be laid. A document feed tray  11  is used to lay a desired document or documents. A roller pair  12  and a roller  13  convey a document. Guides  14  and  15  respectively adjoin the roller pair  12  and roller  13  for guiding a document being conveyed. A belt  16  conveys a document along the glass platen  10 . A flat direction selector  17  switches a direction in which a document read by the reading section  2  should be discharged. A document discharge tray  18  receives a document driven out via the direction selector  17 . Mirrors  19  and  20  and a fluorescent lamp  21  scan a document. A lens  22  focuses the resulting reflection or image light to a CCD (Charge Coupled Device) image sensor or similar image sensor  23 . 
     Among the above constituents of the image reading section  2 , the document feed tray  11 , roller pair  12 , roller  13 , guides  14  and  15 , belt  16 , direction selector  17  and document discharge tray  18  are mounted on a conventional cover plate, not shown, constituting an ADF (Automatic Document Feeder) unit  24 . The ADF unit  24  may be angularly moved toward and away from the glass platen  10  by hand. The ADF unit  24  additionally includes a document sensor  25 , a document size sensor  26 , and a cover plate sensor  27 . The document sensor  25  is responsive to a document laid on the document feed tray  11  and the size of the document. The document size sensor  26  is responsive to the size of a document laid on the glass platen  10 . The cover plate sensor  27  is responsive to the absence of the ADF unit  24  (cover plate not shown) on the glass platen  10 . 
     The paper feeding section  3  arranged in the lower portion of the casing  9  has a configuration taught in Japanese Patent Laid-Open Publication No. 5-124737 mentioned earlier. Specifically, the paper feeding section  3  includes a first tray  28 , a second tray  29 , and a third tray  30  each constituting a paper stocking portion. The first and second trays  28  and  29  allow papers P 1  and P 2  of the same size to be stacked thereon. The third tray  30  allows papers P 3  of relatively large size to be stacked thereon. A paper shifter  31  shifts the entire paper stack P 2  from the tray  29  to the tray  28  when the papers P 1  on the tray  28  are used up. Pick-up rollers  32  and  33  respectively feed the papers P 1  and P 3  one by one. Pressers  34  and  35  press the papers P 1  and P 3  against the pick-up rollers  32  and  33 , respectively. A first paper sensor  36  senses the papers P 1  stacked on the first tray  28  when contacting the papers P 1  pushed up by the presser  34 . Separation roller pairs  39  and  40  are respectively associated with the pick-up rollers  32  and  33 , and each separates the top paper from the underlying papers. Additionally included in the paper feeding section  3  are roller pairs  39  and  40  and a group of rollers  41  for conveyance, and a registration roller pair  42 . The second tray  29  may be pulled out of the casing  9  while the printer  1  is in operation, as desired. A pair of side fences, not shown, are mounted on each of the trays  28 - 30  for guiding the papers P 1 -P 3  in the widthwise direction of the papers. 
     In the paper feeding section  3 , a second paper sensor  43  senses the papers P 2  stacked on the second tray  29  while a third paper sensor  44  senses the papers P 3  stacked on the third tray  30 . A first paper size sensor  45 , a second paper size sensor  46  and a third paper size sensor  47  are used to determine the sizes of the papers P 1 , P 2  and P 3 , respectively. A first residual paper sensor  57  determines the amount of papers P 1  remaining on the first tray  28  in terms of the amount of elevation of the tray  28  caused by the presser  34 . Likewise, a third residual paper sensor  58  determines the amount of papers P 3  remaining on the third tray  30  in terms of the amount of elevation of the tray  30  caused by the presser  35 . A jam sensor  86  determines that a jam has occurred when any one of the papers P 1 -P 3  fails to reach the registration roller pair  42  within a preselected period of time. 
     The master making section  4  arranged above the paper feeding section  3  includes a support member  49  supporting a stencil  48  in the form of a roll  48   a.  A thermal head  50  perforates, or cuts, the stencil  48  by heating it. A platen roller  51  presses the stencil  48  against the thermal head  50  while conveying the stencil  48 . Cutting means  52  cuts the stencil  48  at a preselected length. Roller pairs  53  and  54  convey the stencil  48 . The master making section  4  is constructed into a unit removable from the casing  9 . 
     Specifically, the stencil roll  48   a  includes a core  48   b  rotatably supported by the support member  49 . A stepping motor, not shown, causes the platen roller  51  to rotate while moving means, not shown, selectively moves the platen roller  51  to a first position indicated by a solid line in FIG. 1 or a second position indicated by a dash-and-dots line. At the first position, the platen roller  51  is pressed against the thermal head  50  by a preselected pressure. At the second position, the platen roller  51  is spaced from the thermal head  50 . The cutting means  52  has a conventional configuration in which an upper edge  52   a  is rotatable or movable up and down relative to a lower edge  52   b.    
     The master making section  4  additionally includes a stencil roll sensor  59  responsive to the stencil roll  48   a,  a platen roller sensor  55  responsive to the platen roller  51  brought to the pressing position, and a leading edge sensor  56  responsive to the leading edge of the stencil  48  brought to an initial position to be cut by the cutting means  52 . 
     The printing section  5  is arranged at the left of the master making section  4 , as viewed in FIG.  1 . The printing section  5  includes an ink drum  60 , ink feeding means  61 , and a press roller  62 . The ink drum  60  is made up of a hollow cylindrical, porous support member and a laminate of mesh screens covering the outer periphery of the support member and formed of resin or metal. The ink drum  60  is affixed to flanges, not shown, rotatably mounted on a shaft  63  which plays the role of an ink feed pipe at the same time. Drum drive means, not shown, causes the ink drum  60  to rotate in synchronism with the registration roller pair  42 . The ink drum  60  is removably mounted on the casing  9 . A damper  64  is mounted on the outer periphery of the ink drum  60  for clamping the leading edge of the perforated part of the stencil  48  (master  48  hereinafter). Opening/closing means, not shown, causes the damper  64  to open and then close when the ink drum  60  reaches a preselected angular position. 
     The ink feeding means  61  disposed in the ink drum  60  includes an ink roller  65  and a doctor roller  66  in addition to the shaft  63 . The ink droller is rotatably supported by side plates, not shown, affixed to the shaft  63 . Drive transmitting means, not shown, including gears and a belt transfers a driving force to the ink roller  65  and causes it to rotate clockwise, as viewed in FIG.  1 . The doctor roller  66  adjoins the ink roller  65  such that the outer periphery of the roller  66  is parallel to the outer periphery of the roller  65 . The ink roller  65  and doctor roller  66  form a generally wedge-shaped ink well  67  therebetween. Ink in the ink well  67  is drawn out while passing through a gap between the two rollers  65  and  66 , forming a thin film on the roller  65 . An ink sensor  68  is positioned in the ink well  67  for determining the amount of ink existing in the ink well  67 . 
     The press roller  62  is positioned beneath the ink drum  60  and supported by opposite side walls, not shown, of the casing  9  in such a manner as to be rotatable and angularly movable. A cam, for example, causes the press roller  62  to angularly move into and out of contact with the ink drum  60 , although not shown specifically. A spring or similar biasing means, not shown, constantly biases the press roller  62  toward the ink drum  60 . When the press roller  62  is moved away from the ink drum  60 , locking means, not shown, locks the roller  62  in a spaced position shown in FIG.  1 . 
     The printing section  5  additionally includes an right-and-left image position adjusting mechanism (see Japanese Patent Laid-Open Publication No. 6-293175 mentioned earlier) and a top-and-bottom image position shifting mechanism. The right-and-left image position adjusting mechanism shifts the ink drum  60  in the axial direction of the shaft  63  for shifting the image of a document to be printed on a paper fed from the paper feeding section  3  in the widthwise direction of the paper. The top-and-bottom image position shifting mechanism moves the ink drum  60  in its circumferential direction so as to bring the drum  60  out of synchronism with the registration roller pair  42 , thereby shifting the position of an image to be printed on a paper in the direction of paper conveyance. Two drum sensors  69  and  70  are arranged around the ink drum  60 . The drum sensor  69  is responsive to the axial position of the ink drum  60  while the drum sensor  70  is responsive to the circumferential position of the same and includes, e.g., an encoder. The drum sensors  69  and  70  each sense the displacement of the ink drum  60  from a particular home position. A master absence sensor  87  is responsive to the absence of the master  48  on the outer periphery of the ink drum  60 . 
     The paper discharging section  6  arranged at the left of the printing section  5 , as viewed in FIG. 1, includes a peeler  71 , guides  72  and  73 , a conveyor  74 , and an electrically driven rack  75 . The peeler  71  peels off the paper or printing P (any one of the papers P 1 -P 3 ) wrapped around the ink drum  60 . The peeler  71  is pivotally supported by the sidewalls, not shown, of the casing  9  such that the edge thereof is movable toward and away from the ink drum  60 . The guides  72  and  73  are affixed to the sidewalls of the casing  9  for guiding the printing P separated from the ink drum  60  by the peeler  71 . The conveyor  74  is made up of a drive roller  76 , a driven roller  77 , an endless belt  78  passed over the two rollers  76  and  77 , and a suction fan  79 . While the suction fan  79  sucks the printing P onto the belt  78 , the belt  78  is driven by the drive roller  76  to convey the paper P in the direction indicated by an arrow in FIG.  1 . 
     The paper P conveyed by the conveyor  74  is discharged to the electrically driven rack  75 . The rack  75  includes a tray  80  to be loaded with the papers or printings P, a pair of side fences  81  and  82 , and an end fence  83 . The rack  75  locates each of the side fences  81  and  82  and end fence  83  at a particular position in accordance with a paper size signal output from the paper feeding section  3 . 
     The paper discharging section  6  includes a paper jam sensor  84  responsive to a paper jam and a fence sensor  85  responsive to the positions of the side fences  81  and  82  and end fence  83 . The paper jam sensor  84  determines that a jam has occurred when the paper P has failed to reach the conveyor  74  within a preselected period of time. 
     The master discharging section  7  is located above the paper discharging section  6  and includes an upper discharge member  88 , a lower discharge member  89 , a box  90  for collecting used masters, and a compressor  91 . The upper discharge member  88  is made up of a drive roller  92 , a driven roller  93 , and an endless belt  94  passed over the two rollers  92  and  93 . The drive roller  92  rotates clockwise, as viewed in FIG. 1, causing the belt  94  to move in the direction indicated by an arrow. Likewise, the lower discharge member  89  is made up of a drive roller  95 , a driven roller  96 , and an endless belt  97  passed over the rollers  95  and  96 . The drive roller  95  rotates counterclockwise, as viewed in FIG. 1 to move the belt  97  in the direction indicated by an arrow. Moving means, not shown, selectively moves the lower discharge member  89  to a position shown in FIG. 1 or a position where the circumference of the drive roller  95  contacts a used master  98  wrapped around the ink drum  60 . Lowering means, not shown, selectively lowers the compressor  91  into the box  90  for compressing the used master  98  collected in the box  90 . The two discharge members  88  and  89 , box  90  and compressor  91  are constructed into a unit removable from the casing  9 . 
     The master discharging section  7  additionally includes a compressor home position sensor  99  responsive to the home position of the compressor  91 , a full sensor  100  responsive to the full state of the box  90 , and a jam sensor  101  responsive to a jam of the used master  98 . The box  90  is determined to be full when the compressor  91  does not move downward when applied with a preselected torque. 
     Further, a body door sensor  102  and a paper feed door sensor  103  are mounted on the casing  9 . The body door sensor  102  is responsive to the opening of a body door, not shown, which is opened and closed at the time of replacement and the initial setting of the stencil roll  48   a,  mounting and dismounting of the ink drum  60 , mounting and dismounting of the box  90 , etc. The paper feed door sensor  103  is responsive to the opening of a paper feed door, not shown, which is opened and closed at the time of replenishment of the papers P. 
     FIG. 2 shows a specific arrangement of a control panel  104  mounted on the front part of the top of the stencil printer  1 . As shown, the control panel  104  includes a perforation start key  105  for starting a master making operation, a print start key  106 , a proof print key  107 , a stop key  108 , numeral keys  109 , an enter key  110 , a clear key  111 , a program key  112 , a mode key  113 , a mode clear key  114 , enlarge/reduce keys  115 , print speed keys  116 , right-and-left image position keys  117 , top-and-bottom image position keys  118 , a display  119  implemented by seven-segment LEDs (Light Emitting Diodes), an error display  120  for displaying, e.g., a jam and implemented by LEDs, and a display  121  implemented by an LCD (Liquid Crystal Display). Also arranged on the control panel  104  are a power save mode key  122  and power save mode indicating means  123  indicative of a power save mode selected on the key  122  and implemented by an LED. Operation commands input on the control panel  104  are sent to the control section  8 , FIG.  1 . The control section  8 , in turn, sends display signals to the displays  119 ,  120  and  121  and power save mode indicating means  123 . 
     FIG. 3 shows control means  124 , an output OFF device  130  and a PWB (Printed Wiring Board)  145  (see FIG. 4) constituting the major part of the control section  8 , FIG.  1 . As shown, the control means  124  is implemented by a conventional microcomputer including a CPU (Central Processing Unit)  125 , a RAM (Random Access Memory)  126 , a ROM (Read Only Memory)  127 , and an I/O (Input/Output) expander  128 . The control means  124  is mounted on the PWB  145  disposed in the control section  8 . As shown in FIG. 4, the control means  124  controls the entire printer  1  with power fed from a PSU (Power Supply Unit)  129  via the output OFF device  130 . 
     The CPU  125  receives the output signals of the various sensors and control panel  104 . The image reading section  2 , paper feeding section  3 , master making section  4 , printing section  5 , paper discharging section  6  and master discharging section  7  each are connected to the CPU  125  via a respective driver. The CPU  125  performs, based on a program stored in the ROM  127  beforehand, operations with the signals input from the sensors and control panel  104  and sends a particular control signal to the driver of each of the above sections  2 - 7 . At the same time, the CPU  125  sends display signals to the control panel  104 . 
     The CPU  125  temporarily writes the program read out of the ROM  127  in the RAM  126 . The program written to the RAM  126  may be rewritten via the control panel  104 , as needed. Further, only when the operator selects the power save mode on the power save mode key  122 , a power save mode program is written to the RAM  126 . A back-up battery is associated with the RAM  126  so as to hold the programs written to the RAM  126  even when the main power supply of the printer  1  is turned off. 
     The ROM  127  stores a plurality of different programs for operating various actuators included in the printer  1 . Particularly, when the operator selects the power save mode on the key  122 , the power save mode program causes the positions of various portions determined by the displacements of the actuators to be written to the RAM  126  and causes the output OFF device  130  to turn off the outputs of various sections. 
     As shown in FIG. 4, the PWB  145  includes a plurality of connection terminals. Power output from the PSU  129  is input to the PWB  145  via the output OFF device  130  in the form of four different voltages of +24 V, ±12 V, +5 V and +5 VE. The voltage of +24 V drives motors, solenoids and fans included in the printer  1  as actuators while the voltage of ±12 V drives, e.g., the image sensor  23  of the image reading section  2 . The voltage of +5 V is applied to the control means  124  and the power save mode indicating means  123  of the control panel  104 . Further, the voltage of +5 VE is applied to the sensors of the printer  1  and the display means of the control panel  104  other than the power save mode indicating means  123 . 
     The output OFF device  130  is connected between the PSU  129  and the PWB  145  and includes a switching circuit implemented by, e.g., FETs (Field Effect Transistors). The output OFF device  130  selectively sets up or interrupts the supply of +24 V, ±12 V and 5 VE in accordance with an output ON/OFF signal fed from the control means  124 . 
     The printer  1  having the above construction will be operated as follows. When the main power supply of the printer  1  is turned on, the control means  124  causes the ink drum  60  to move axially to its axial home position. The drum axial position sensor  69  senses the drum ink  60  reached the axial home position and then sends its output to the control means  124 . In response, the control means  124  causes the ink drum  60  to move circumferentially to its circumferential home position. The drum circumferential position sensor  70  senses the ink drum  60  reached the circumferential home position and sends its output to the control means  124 . As a result, the ink drum  60  is held at a preselected master feed position. Ink is fed to the ink well  67  within the ink drum  60  until the ink sensor  68  senses the ink. 
     At the same time, the control means  124  causes the compressor  91  to be lowered past the full sensor  100  and then located at a home position to which the compressor home position sensor  99  is responsive. If the compressor  91  cannot be lowered past the full sensor  100 , a suitable message representative of the full condition of the box  90  appears on the control panel  104 . 
     Further, the control means  124  causes the pressers  34  and  35  of the paper feeding section  3  to be raised until the paper stacks P 1  and P 3  contact the pick-up rollers  32  and  33 , respectively. At this instant, the presence/absence of each paper stack P and the remaining amount of the same are determined. Specifically, if the paper stack P 3  is absent, the presser member  35  is returned to its initial position shown in FIG. 1 while the absence of the paper stack P 3  is displayed on the control panel  104 . Likewise, if the paper stacks P 1  and P 2  are absent, the presser  34  is returned to its initial position while the absence of the paper stacks P 1  and P 2  is displayed on the control panel  104 . Assume that the paper stack P 1  is absent, but the paper stack P 2  is present. Then, after the return of the presser  34  to the initial position, the paper shifter  31  shifts the entire paper stack P 2  to the first tray  28  while a message representative of the absence of the stack P 2  appears on the control panel  104 . 
     In parallel with the above operation of the paper feeding section  3 , the paper discharging section  6  locates the side fences  81  and  82  of the rack  75  at their home positions and then move them to positions matching with the size of the papers P sensed by any one of the paper size sensors  45 - 47 . The side fences  81  and  82  are accurately located on the basis of the output of a fence sensor  85 . At the same time, the suction fan  79  is caused start operating. 
     In the master making section  4 , the stencil roll sensor  59  determines whether or not the stencil roll  48   a  is present, while the platen roller sensor  55  determines whether or not the platen roller  51  and thermal head  50  are held in contact with each other. If the stencil roll  48   a  is absent, a message representative of the absence appears on the control panel  104 . Likewise, if the platen roller  51  is not in contact with the thermal head  50 , a message representative of such an erroneous position of the roller  51  appears on the control panel  104 . If the sensors  59  and  55  both turn on, but the leading edge sensor  56  does not turn on, the platen roller  51  is driven to convey the stencil  48  until the sensor  56  turns on. 
     Further, if one or more of the cover plate sensor  27 , paper discharge jam sensor  84 , paper feed jam sensor  86 , master discharge jam sensor  101 , body door sensor  102  and paper feed door sensor  103  remain in an ON state, a message representative of such a condition appears on the control panel  104 . 
     As stated above, the printer  1  is ready to make a master (stand-by state) only if the ink drum  60  is located at its axial and circumferential home positions, if the ink sensor  68  senses the ink in the ink well  67 , if the compressor  91  is located at its home position with the empty box  90 , if the paper feeding section  3  is loaded with papers to use, if the stencil roll  48   a  is set on the support member  49 , if the platen roller  51  is in contact with the thermal head  50  with the leading edge sensor  56  sensing the leading edge of the stencil  48 , and if all the sensors  27 ,  84 ,  86 ,  101 ,  102  and  103  are in an OFF state. 
     Assume that the operator lays one or more documents on the document feed tray  11 , sets desired master making conditions on the various keys of the control panel  104 , and then presses the perforation start key  105 . In response, the image reading section  2  reads the document brought to the glass platen  10  while sending an image data signal representative of the document to the control means  124 . 
     In parallel with the operation of the image reading section  2 , the master discharging section  7  removes the used master  98  from the ink drum  60 . Specifically, drum drive means, not shown, causes the ink drum  60  with the used master  98  wrapped therearound to rotate counterclockwise, as viewed in FIG.  1 . When the control means  124  determines that the trailing edge of the used master  98  has reached a preselected discharge position corresponding to the drive roller  95 , the control means  124  causes the drive means and moving means to rotate the drive rollers  92  and  95  and move the lower discharge member  89  toward the ink drum  60 . At the time when the drive roller  95  contacts the used master  98 , the ink drum  60  is rotating counterclockwise. Therefore, the used master  98  picked up by the drive roller  95  is nipped by the upper discharge roller  88  and lower discharge roller  89  and peeled off from the drum  60  thereby. Thereafter, the used master  98  is conveyed to the box  90  by the discharge members  89  and  88  and compressed in the box  90  by the compressor  91 . 
     After the used master  98  has been fully removed from the ink drum  60 , the ink drum  60  is further rotated to the previously mentioned master feed position. Subsequently, the control means  124  causes the opening/closing means to open the damper  64 . In this condition, the ink drum  60  waits for a new master. This is the end of the master discharging operation. 
     The above master discharging operation is followed by a master making operation. Specifically, after the ink drum  60  has been brought to the master feed position, the control means  124  causes the stepping motor to rotate the platen roller  51  and roller pairs  53  and  54  with the result that the stencil  48  is paid out from the roll  48   a.  The thermal head  50  selectively perforates the stencil  48  with heat in accordance with the image data output from the image reading section  2 . 
     The perforated part of the stencil, i.e., the master  48  is conveyed toward the damper  64 . When the control means  124  determines that the leading edge of the master  48  has reached a preselected position to be clamped by the damper  64  in terms of the number of steps of the stepping motor, it cause the opening/closing means to close the damper  64 . As a result, the leading edge of the master  48  is retained on the ink drum  60 . 
     Subsequently, the ink drum  60  is caused to rotate clockwise at a peripheral speed equal to the speed at which the master  48  is conveyed, sequentially wrapping the master  48  therearound. When the control means  124  determines that a single master  48  has been completed, it causes the platen roller  51  and roller pairs  53  and  54  to stop rotating and causes the upper edge  52   a  of the cutting means  52  to move and cut off the master  48 . The master  48  pulled out by the ink drum  60  in rotation is fully wrapped around the drum  60  when the drum  60  again reaches its home position. The ink drum  60  is caused to stop rotating on reaching the home position. 
     After the master  48  has been wrapped around the ink drum  60 , a trial printing step is executed. After the ink drum  60  has been stopped at the home position, the control means  124  causes the drum  60  to start rotating at a low speed and causes the pick-up roller  32  (or  33 ), separation roller pair  37  (or  38 ) and roller pairs  39 - 41  to start rotating. The pick-up roller  32  (or  33 ) and separation roller pair  37  (or  38 ) cooperate to pull out the top paper P from the first tray  28  (or third tray  30 ). The registration roller pair  42  nips the leading edge of the paper P fed from the tray  28  (or  30 ). 
     When the leading edge of the image area of the master  48  wrapped around the ink drum  60  reaches a position corresponding to the press roller  62 , the control means  124  causes the registration roller pair  42  to start rotating and driving the paper P toward the gap between the ink drum  60  and the press roller  62 . The control means  124  actuated the registration roller pair  42 , as stated above, causes the locking means to unlock the press roller  62 . As a result, the press roller  62  is angularly moved toward the ink drum  60 . 
     The press roller  62  presses the paper P fed from the registration roller pair  42  against the master  48  existing on the ink drum  60 . Consequently, the paper P and master  48  are pressed between the press roller  62  and the ink drum  60 . Ink fed to the inner periphery of the ink drum  60  by the ink roller  65  penetrates through the porous support and mesh screens of the ink drum  60  and then fills the interstice between the ink drum  60  and the master  48 . Finally, the ink is transferred from the ink drum  60  to the paper P via the perforations of the master  48 . 
     The peeler  71  peels off the paper P carrying the ink thereon from the ink drum  60  while introducing it into the gap between the guides  72  and  73 . The paper P is conveyed to the left, as viewed in FIG. 1, by the belt  78  while being held on the belt  78  by the suction of the suction fan  79 . As a result, the paper or trial printing P is driven out to the tray  80 . Thereafter, the printer  1  waits for an actual printing operation. 
     In the above condition, the operator presses the proof print key  107 . In response, another paper P is fed from the paper feeding section  3  and nipped by the registration roller pair  42  in the same manner as the first paper P. At the same time, the ink drum  60  is caused to rotate at a high speed at the same timing as in the trial printing procedure. The registration roller pair  42  drives the paper P toward the gap between the ink drum  60  and the press roller  62 . The paper P is pressed against the master  48  present on the ink drum  60  by the press roller  62  with the result that the ink is transferred to the paper P for forming an image. The peeler  71  removes the paper P from the ink drum  60 , and the conveyor  74  conveys the paper P to the tray  80 . As soon as the ink drum  60  is returned to the circumferential home position, the proof printing procedure ends. 
     The operator watching the proof printing determines whether or not it is acceptable. If the proof printing P is not acceptable, the operator readjusts the image by operating the print speed key  116 , right-left image position key  117  and top-bottom image position key  118  and produces another proof printing. If the resulting proof printing is acceptable, the operator inputs a desired number of printings on the numeral keys  109  and then presses the print start key  106 . The number of printings input on the numeral keys  109  appears on the display  119 . The paper feeding section  3  continuously feeds the same number of papers P as the desired number of printings. While the ink drum  60  again returns to its home position after the printing operation, this home position includes the shift in the right-and-left direction and the shift in the top-and-bottom direction. 
     The printer  1  performs the following operation when the power save mode key  122  unique to the illustrative embodiment is pressed. Assume that the operator completed the above printing operation with the printer  1  will not use it for more than a preselected period of time. Then, the operator presses the power save mode key  122 . In response to the resulting signal output from the control panel  104 , the CPU  125  calls the power save mode program stored in the ROM  127 , writes data in the RAM  126 , and sends a signal to the control panel  104  to turn on the power save mode indicating means or LED  123 . This allows the operator to confirm the power save mode. In the power save mode, the RAM  126  plays the role of printer status storing means. 
     The above data written to the RAM  126  include the outputs of the paper sensors  36 ,  43  and  44 , the outputs of the paper size sensors  45 - 47 , the outputs of the residual paper sensors  57  and  58 , the output of the platen roller sensor  55 , the output of the leading edge sensor  56 , the output of the stencil roll sensor  59 , the output of the ink sensor  68 , the output of the drum axial position sensor  69 , the output of the drum circumferential position sensor  70 , the output of the fence sensor  85 , and the output of the full sensor  100 . 
     Further, the CPU  125  sends an output OFF signal to the output OFF device  130  in order to interrupt the supply of the voltages other than the voltage of +5 V. As a result, all the outputs other than the output of the power save mode indicating means  123  are turned off, i.e., power supply to the circuitry other than the power save mode indicating means  123  is interrupted in order to save power. 
     When the operator selected the power save mode again presses the power save mode key  122 , the CPU  125  sends, in response to the resulting signal from the control panel  104 , an output ON signal to the output OFF device  130 . In response, the output OFF device  130  again sets up the supply of the voltages of +24 V, ±12 V and +5 VE and thereby turns on all of the outputs of the printer  1 , so that the power save mode is cancelled. At this instant, the CPU  125  reads the data stored in the RAM  126  at the beginning of the power save mode operation and compares them with current data. In this sense, the CPU  125  serves as comparing means at the time of recovery from the power save mode. 
     If the stored data and current data compare equal, the printer  1  is immediately brought to its stand-by state, skipping the steps to be executed at the time of the turn-on of the main power supply. If any one of the current data differs from corresponding one of the stored data, the printer  1  is brought to the stand-by state after causing only a portion relating to the different data to operate or after varying the display. It should be noted that the printer  1  neglects the above difference if it is derived from a change in the status of the full sensor  100  from ON (at the beginning of the power save mode) to OFF (at the time of cancellation of the power save mode). 
     As stated above, when the printer  1  is not used, the power save mode is set up to obviate wasteful power consumption. In addition, at the time of cancellation of the power save mode, the printer  1  skips needless steps in order to prevent the first print time from being delayed. 
     The illustrative embodiment may be modified as follows. In a first modification, in the power save mode, power is fed to the entire control panel  104 , i.e., the voltage of +5 V is continuously applied not only to the power save mode indicating means  123  but also to the other constituents; the power save mode is cancelled when the operator presses any one of the keys on the control panel  104 . In a second modification, in the power save mode, power supply to the body door sensor  102  and paper feed door sensor  103  is not interrupted; the power save mode is cancelled when the operator opens the body door or the paper feed door. In a third modification, in the power save mode, power supply to the document sensor  25  and cover plate sensor  27  is not interrupted; the power save mode is cancelled when the operator lays a document or documents on the document feed tray  11  or opens the ADF unit  24  away from the glass platen  10 . In a fourth modification, in the power save mode, power supply to the paper sensors  36  and  44  is not interrupted; the power save mode is cancelled when the status relating to the papers P changes from “absence” to “presence”. In a fifth modification, a human body sensor, not shown, is positioned in the upper portion of the casing  9 , so that the power save mode is cancelled when the sensor senses a human body. In a sixth modification, a sensor, not shown, is located in the vicinity of the master making section  4 ; the power save mode is cancelled when the master making section  4  is pulled out of the casing  9 . In a seventh modification, a sensor, not shown, is located in the vicinity of the ink drum  60 ; the power save mode is cancelled when the ink drum  60  is pulled out of the casing  9 . In an eighth modification, a sensor, not shown, is located in the vicinity of the box  90 ; the power save mode is cancelled when the box  90  is pulled out of the casing  9 . 
     The power save mode operation may begin on the elapse of a preselected period of time since the operator has pressed the power save mode key  122  or since the printer  1  has been operated last time. 
     An arrangement may be made such that the power save mode is inhibited when any one of the jam sensors  84 ,  86  and  101  and leading edge sensor  56  senses a jam or when a serviceman call occurs (indicated by the display  120  of the control panel  104 ), thereby promoting rapid jam processing or repair. This is also true when the master absence sensor  87  does not sense the master  48  expected to be present on the ink drum  60 ; the master  48  is not present on the drum  60  at the time of delivery to the user&#39;s station or is removed from the drum  60  at the time of a jam. The sensor  87  therefore prevents the ink from being evaporated from the surface of the ink drum  60  and rendering printings to be produced later defective. Further, the power save mode may be inhibited during master making operation, master discharging operation, printing operation and so forth; otherwise, the printer  1  would stop operating halfway and would need a substantial period of time for recovery. 
     Referring to FIG. 5, a sorter, or peripheral unit, with which an alternative embodiment of the present invention is practicable is shown. As shown, the sorter, labeled  131 , is connected to the printer  1  in place of the electrically driven rack  75 . The sorter  131  includes a sorter body  132 , bins  133  movable up and down, a mechanism  134  for moving the bins  133  up and down, and a conveyor  135  for conveying the papers P sequentially driven out of the printer  1  toward the bins  133 . The operation of the sorter  131  is dependent on the power supply of the printer  1 . 
     Each bin  133  is bent substantially vertically upward at its upstream end in the direction of paper conveyance. A roller, not shown, is mounted on the underside of each bin  133 . The lowermost bin  133  is affixed to a bracket, not shown, included in the mechanism  134 . The uppermost bin  133  has its bent end extended more than the other bins  133  and serves as a non-sort tray. 
     The mechanism  134  includes a lead cam  136  having a spiral groove in its circumference and drive means, not shown, in addition to the above bracket. When the roller of any one of the sort bins  133  is received in the groove of the lead cam  136 , the cam  136  is rotated to move the bin  133  upward or downward. This kind of configuration of the mechanism  134  is conventional. 
     The conveyor  135  includes a conveyor body  137 , a drive roller  138 , a driven roller  139 , a plurality of parallel endless belts  140  passed over the drive roller  138  and driven roller  139 , and a suction fan  141  positioned below the belts  140 . Opposite edges of a top plate, not shown, forming part of the conveyor body  137  are bent upward at the downstream end in the direction of paper conveyance, forming jump lugs  142 . A sort jam sensor  143  senses a jam when the paper P driven out of the printer  1  fails to reach any one of the bins  133  within a preselected period of time. A sort position sensor  144  senses the position of the bin  133  in terms of the amount of rotation of the lead cam  136 . 
     The operation of the printer  1  with the sorter  131  is as follows. When the main power supply of the printer  1  is turned on, the printer  1  executes the previously stated sequence of steps and waits in the stand-by state ready to make a master, as in the previous embodiment. At the same time, the control mans  124  sends a signal to the sorter  131  to cause the lead cam  136  to rotate. In response to an output of the sort position sensor  144 , the uppermost bin or non-sort tray  133  is brought to a position where it faces the conveyor  135 . If the sort jam sensor  143  is in an ON state, then a message representative of a jam appears on the operation panel  104 . 
     The printer  1  and sorter  131  can be used only if the printer  1  is in its stand-by state, if the uppermost bin  133  is located at the above posit ion, and if the sort jam sensor  143  is in its OFF state. 
     Subsequently, when the operator lays a document on the document feed tray  11  and then presses the perforation start key  105 , the printer  1  performs the image reading operation, master discharging operation, master making operation, master wrapping operation and trial printing operation and then waits for an actual printing operation, as in the previous embodiment. 
     Assume that the operator selects the sorter  131  on a suitable key provided on the control panel  104 , e.g., the mode key  113  and then presses the print start key  106 . In response, the papers P are sequentially fed from the paper feeding section  3  while the lead cam  136  is rotated to sort the resulting printings P in accordance with a desired number of copies (sets). 
     After the papers P have been sorted by the sorter  131 , the operator presses the power save mode key  122 . In response, the previously stated data are written to the RAM  126  while power supply to all of the constituents other than the power save mode indicating means  123  is interrupted in order to save power. In the illustrative embodiment, bin position data output from the sort position sensor  144  is written to the RAM  126  in addition to the above data. 
     When the operator selected the power save mode again presses the power save mode key  122  for canceling it, a signal output from the key  122  is sent to the CPU  125  included in the control means  124 . In response, the CPU  125  delivers an output OFF signal to the output OFF device  130 . In response, the output OFF device  130  again supplied power to all of the constituents, so that all the outputs of the printer land sorter  131  are turned on. At this time, the CPU  125  reads the data written to the RAM  126  at the beginning of the power save mode and compares them with current data output at the time of recovery from the power same mode. 
     If the stored data and current data compare equal, CPU  125  directly brings the printer  1  and sorter  131  into their ready states, skipping the steps to be executed at the time of turn-on of the main power supply. If any one of the recovered data differs from corresponding one of the stored data, the CPU  125  brings the printer  1  or the sorter  131  to the stand-by state after causing only a portion relating to the different data to operate or after varying the display. 
     As stated above, when the printer  1  and sorter  131  are not used, the power save mode is set up to obviate wasteful power consumption. In addition, at the time of cancellation of the power save mode, the printer  1  and sorter  131  skip needless steps for thereby preventing the first print time from being delayed. 
     The modifications of the previous embodiment are also applicable to the above alternative embodiment. Further, the power save mode may be cancelled in response to a signal output from the sorter  131 . If desired, a personal computer may be connected to the printer  1 , in which case the power save mode will be cancelled in response to a signal received from the personal computer. 
     In the embodiments shown and described, among the four different voltages of +24 V, ±12 V, +5 V and +5 VE, only the voltage of +5 V is continuously applied to the control means  124  and power save mode indicating means  123 . If desired, the voltage of +5 V may be connected to necessary sensors in the same manner as to the sensors  102  and  103  from the convenient operation standpoint. In addition, voltages of +24 VE and ±12 VE may be used in addition to the voltages of +24 V and ±12 V, so that any desired unit can operate even in the power save mode. 
     In summary, it will be seen that the present invention provides a stencil printer capable of being held in a power save mode for saving power when it is not used. In addition, the printer can recover from the power save mode without any wasteful step so as to prevent the first print time from being delayed. 
     Various modifications will become possible for those skilled in the art after receiving the teachings of the present disclosure without departing from the scope thereof.