Abstract:
An optional apparatus for an image forming apparatus which forms an image on a print medium, which is detachably connected to the image forming apparatus and performs predetermined optional processing for a print medium supplied from the image forming apparatus, is provided. The optional apparatus includes a storage battery which can be charged/discharged, an optional processing unit configured to execute the predetermined optional processing upon receiving supply of power at least from the image forming apparatus or from the storage battery, and a switch unit configured to cut off supply of power from the storage battery to the optional processing unit when the optional apparatus is detached from the image forming apparatus or a door of the optional apparatus is opened.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to an optional apparatus for an image forming apparatus, which performs predetermined optional processing for a print medium supplied from the image forming apparatus.  
       BACKGROUND OF THE INVENTION  
       [0002]     Recently, the market has demanded more that new values, such as option expandability and energy saving, be added to image forming apparatuses. In addition, it has been required to supply power from an image forming apparatus to an optional apparatus so as to improve the design of the optional apparatus when it is mounted and allow a user to easily detach/attach it.  
         [0003]     When, however, power is to be supplied from the image forming apparatus body to, for example, an optional apparatus designed to perform stapling processing, since high power is required for stapling operation, a large-capacity power supply circuit must be prepared for the image forming apparatus body in expectation of the maximum load on the optional apparatus. This leads to an unnecessary increase in cost for a user who uses only the image forming apparatus. It has therefore been required to minimize an increase in the cost of the image forming apparatus body by reducing the maximum power consumed by the optional apparatus itself.  
         [0004]     In addition, a demand has arisen for a means for reducing the maximum powers of an image forming apparatus and optional apparatus to prevent the maximum power of the system from exceeding the maximum power that can be supplied from a one-system commercial power supply so as to prevent a protective means such as the circuit breaker of the commercial power supply from activation.  
         [0005]     On the other hand, an image forming apparatus or an optional apparatus individually having a power supply uses an arrangement designed to cut off, for safety, power supplied to a driving means, heating means, or the like placed at a position where a user can touch when the user opens the image forming apparatus in case of paper jam.  
         [0006]     When a storage battery is provided for an optional apparatus which receives power from an image forming apparatus, the following problem arises. Although power from the image forming apparatus to the optional apparatus is cut off when the optional apparatus is detached from the image forming apparatus or the optional apparatus is opened, electric charge remaining in the storage battery may allow a driving means of the optional apparatus to operate.  
       SUMMARY OF THE INVENTION  
       [0007]     In view of the above problems in the conventional art, the present invention has an object to take measures for safety in an optional apparatus which receives power supplied from an image forming apparatus and including a storage battery when the optional apparatus is detached from the image forming apparatus or the optional apparatus is opened.  
         [0008]     According to one aspect of the present invention, an optional apparatus for an image forming apparatus which forms an image on a print medium, which is detachably connected to the image forming apparatus and performs predetermined optional processing for a print medium supplied from the image forming apparatus, is provided. The optional apparatus includes a storage battery which can be charged/discharged, an optional processing unit configured to execute the predetermined optional processing upon receiving supply of power at least from the image forming apparatus or from the storage battery, and a switch unit configured to cut off supply of power from the storage battery to the optional processing unit when the optional apparatus is detached from the image forming apparatus or a door of the optional apparatus is opened.  
         [0009]     The above and other objects and features of the present invention will appear more fully hereinafter from a consideration of the following description taken in connection with the accompanying drawing wherein one example is illustrated by way of example. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.  
         [0011]      FIG. 1  is a block diagram showing the arrangements of an image forming apparatus and sheet processing apparatus according to the first embodiment;  
         [0012]      FIG. 2  is a graph for explaining an output voltage from a storage battery in this embodiment;  
         [0013]      FIG. 3  is a flowchart showing sheet processing operation by power supply from the storage battery in this embodiment;  
         [0014]      FIG. 4  is a block diagram showing a case wherein the sheet processing apparatus is detached from the image forming apparatus in the first embodiment;  
         [0015]      FIG. 5  is a block diagram showing the arrangements of an image forming apparatus and sheet processing apparatus according to the second embodiment;  
         [0016]      FIG. 6  is a block diagram showing a case wherein the sheet processing apparatus is detached from the image forming apparatus in the second embodiment;  
         [0017]      FIG. 7  is a block diagram showing the arrangements of an image forming apparatus and sheet processing apparatus according to the third embodiment;  
         [0018]      FIG. 8  is a block diagram showing a case wherein the sheet processing apparatus is detached from the image forming apparatus in the third embodiment;  
         [0019]      FIG. 9  is a block diagram showing the arrangements of an image forming apparatus and sheet processing apparatus according to the fourth embodiment; and  
         [0020]      FIG. 10  is a block diagram showing a case wherein the sheet processing apparatus is detached from the image forming apparatus in the fourth embodiment. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]     Preferred embodiments of the present invention will be described in detail in accordance with the accompanying drawings. The present invention is not limited by the disclosure of the embodiments and all combinations of the features described in the embodiments are not always indispensable to solving means of the present invention.  
       First Embodiment  
       [0022]      FIG. 1  is a block diagram showing the arrangements of an image forming apparatus  301  and a sheet processing apparatus  302  as an optional apparatus according to this embodiment. The sheet processing apparatus  302  is designed to be detachable with respect to the image forming apparatus  301 . When the sheet processing apparatus  302  is mounted on the image forming apparatus  301 , they are electrically connected to each other.  
         [0023]     The image forming apparatus  301  comprises a power supply circuit  401 , an image forming apparatus control circuit  402  which controls image forming processing, and a switch press member  412  which presses a switch  420  of the sheet processing apparatus  302 . Power is supplied from a commercial power supply (not shown) to the power supply circuit  401  through a power cord  411 . As other constituent elements of the image forming apparatus  301 , known elements can be used. An illustration of these elements is omitted because they are not significantly relevant to the present invention.  
         [0024]     The sheet processing apparatus  302  in this embodiment staples a bundle of a predetermined number of printing media (to be referred to as sheets hereinafter) upon image formation, thus executing an optional function for the image forming apparatus  301 . Reference numeral  312  denotes a stapler which binds a plurality of sheets discharged from the image forming apparatus  301 ;  403  and  404 , diodes;  405 , a storage battery which can charge and discharge;  406 , a charging circuit which charges the storage battery  405 ;  407 , a battery voltage detecting circuit which detects the output voltage of the storage battery  405 ;  408 , a constant-voltage control circuit which controls the output voltage from the storage battery  405  to a predetermined voltage;  409 , a sheet processing apparatus control circuit which controls the conveyance of sheets and stapling operation;  410 , a staple driving unit which drives the stapler  312 ;  420 , the switch which is turned on by being pressed by the switch press member  412  only when the sheet processing apparatus  302  is connected to the image forming apparatus  301 ; and  413 , a switch which is turned on/off in accordance with an instruction from the sheet processing apparatus control circuit  409 .  
         [0025]     The operation of the sheet processing apparatus  302  will be described next.  
         [0026]     The power supply circuit  401  of the image forming apparatus  301  applies a predetermined voltage to the image forming apparatus control circuit  402  and applies a predetermined voltage Va to the sheet processing apparatus  302  set as an option through a connector. The image forming apparatus control circuit  402  also communicates with the sheet processing apparatus control circuit  409  in the sheet processing apparatus  302  through a connector to perform timing control to smoothly convey sheets and perform stapling operation.  
         [0027]     The charging circuit  406  receives the voltage Va applied from the power supply circuit  401 , and applies a predetermined voltage Vb (Va&lt;Vb in this case) to the storage battery  405  including, for example, a plurality of electric double layer capacitor in accordance with a charge instruction from the sheet processing apparatus control circuit  409 , thereby charging the storage battery  405  to a predetermined voltage Vc Vc (≈Vb). Note that an electric double layer capacitor is an element attracting a great deal of attention in many fields because it has as large as a capacitor of several F or more, charging efficiency better than a secondary battery, and long service life.  
         [0028]     The battery voltage detecting circuit  407  detects the charged voltage of the storage battery  405 , and transmits the detection result as, for example, an analog signal to the A/D port of a CPU (not shown) in the sheet processing apparatus control circuit  409 . The sheet processing apparatus control circuit  409  issues a charge instruction to the charging circuit  406  in accordance with the detection result from the battery voltage detecting circuit  407 .  
         [0029]     The constant-voltage control circuit  408  controls a charged voltage Vc for the storage battery  405  to a voltage Vs (Vs≈Va−Vf, Vs&lt;Vc, forward voltage Vf of diode  403 =about 0.6 V) necessary for stapling operation, and applies the voltage Vs to the staple driving unit  410  through the switches  413  and  420 , thereby driving the stapler  312 .  
         [0030]     As described above, the switch  420  is designed to be turned on by being pressed by the switch press member  412  only when the sheet processing apparatus  302  is connected to the image forming apparatus  301 . As the switch  413 , a semiconductor switch such as an FET is preferably used in consideration of on/off durability. If, however, no problem arises in terms of service life associated with an on/off count, a mechanical switch such as a relay may be used.  
         [0031]     The diode  403  serves to prevent an output from the power supply circuit  401  from being applied to the staple driving unit  410  when the voltage Vs is applied from the storage battery  405  through the constant-voltage control circuit  408  and to prevent power from the storage battery  405  from being supplied to the image forming apparatus  301 .  
         [0032]     Stapling operation by power supply from the storage battery  405  will be described next with reference to  FIGS. 2 and 3 .  FIG. 2  is a view for explaining an output voltage from the storage battery  405 .  FIG. 3  is a flowchart showing sheet processing operation (stapling operation) by power supply from the storage battery  405 .  
         [0033]     When a predetermined number N of sheets are placed on a stack tray (not shown), the sheet processing apparatus control circuit  409  monitors the charged voltage Vc from the storage battery  405  (step S 701 ), and checks whether the voltage Vc falls within a voltage range of Vc1&gt;Vc&gt;Vc2 between a maximum charged voltage Vc1 and a charging start voltage Vc2 (step S 702 ). If the voltage Vc falls within the predetermined range, the sheet processing apparatus control circuit  409  applies the voltage Vs to the staple driving unit  410  through the switch  420  by turning on the switch  413  in accordance with the timing of image forming operation (step S 703 ). The staple driving unit  410  drives the stapler  312  by using the supply voltage Vs and staples the sheet bundle (step S 704 ). Since stapling operation is performed by the energy stored in the storage battery  405 , the maximum consumption current in the sheet processing apparatus  302  which flows from the power supply circuit  401  to the sheet processing apparatus  302  for a short period of time at the time of stapling operation is reduced. That is, since the maximum current (maximum consumption power) flowing in the sheet processing apparatus  302  is reduced, the maximum consumption current of the system formed when the sheet processing apparatus  302  is connected to the image forming apparatus  301  can be reduced.  
         [0034]     After the stapling operation, the switch  413  is turned off (step S 705 ). It is then determined whether the job is complete (step S 706 ). If the job is complete, the process is terminated. If the job is not complete, the storage battery  405  is charged to prepare for the next stapling job (step S 707 ). If the charged voltage Vc falls within the predetermined voltage range of Vc1&gt;Vc&gt;Vc2 at this time, the storage battery  405  need not necessarily be charged in advance, and the switch  413  need not be turned off either. It suffices to turn off the switch  413  and start charging when the charged voltage Vc becomes lower than charging start voltage Vc2.  
         [0035]     If it is determined in step S 702  that the charged voltage Vc is lower than the charging start voltage Vc2, the necessary voltage Vs may not be applied to the staple driving unit  410  depending on conditions such as a printing speed and the number of sheets to be stapled. That is, since stapling may not be done, image forming operation is temporarily stopped (step S 708 ). The flow then advances to step S 707  to ensure a charging time by which the storage battery  405  is charged to the maximum voltage Vc1.  
         [0036]      FIG. 4  shows a case wherein the sheet processing apparatus  302  is detached from the image forming apparatus  301 . When the sheet processing apparatus  302  is detached from the image forming apparatus  301 , power supplied from the power supply circuit  401  to the staple driving unit  410  is cut off. In addition, when the switch press member  412  is detached from the switch  420 , the switch  420  is opened to cut off the power supplied from the storage battery  405  to the staple driving unit  410 .  
         [0037]     As described above, in the image forming apparatus designed to supply power from the power supply circuit  401  in the image forming apparatus  301  to the storage battery  405  in the sheet processing apparatus  302  as the optional apparatus, the amount of power supplied from the power supply circuit  401  at the time of stapling operation can be reduced. In addition, when the sheet processing apparatus  302  is detached from the image forming apparatus  301 , the supply of power from the power supply circuit  401  is cut off. In addition, since the switch  420  between the storage battery  405  and the staple driving unit  410  is turned off, the supply of power from the storage battery  405  to the staple driving unit  410  can be reliably cut off. This makes it possible to ensure high safety.  
       Second Embodiment  
       [0038]      FIG. 5  is a block diagram showing the arrangements of an image forming apparatus and sheet processing apparatus according to the second embodiment.  
         [0039]     A sheet processing apparatus  302  in this embodiment performs trimming processing of cutting a bundle of a predetermined number of sheets after image formation as an optional function for an image forming apparatus  301 . The same reference numerals as in  FIG. 1  denote the same parts in  FIG. 5 , and a description thereof will be omitted. In addition, a description of the output voltage of a storage battery and operation based on the supply of power from a storage battery are the same as those described with reference to  FIGS. 2 and 3 , and a description thereof will be omitted (this also applies to the following embodiments).  
         [0040]     The arrangement and operation of the sheet processing apparatus  302  in this embodiment shown in  FIG. 5  will be described below.  
         [0041]     Reference numeral  501  denotes a trimmer which cuts sheets;  502 , a trimming driving unit which drives the trimmer  501 , and  503 , a relay.  
         [0042]     A power supply circuit  401  of the image forming apparatus  301  applies a predetermined voltage to an image forming apparatus control circuit  402 , and also applies a predetermined voltage Va to the sheet processing apparatus  302  set as an option through a connector. The image forming apparatus control circuit  402  communicates with a sheet processing apparatus control circuit  409  in the sheet processing apparatus  302  through a connector, and performs timing control to smoothly convey sheets and smoothly perform trimming operation.  
         [0043]     A charging circuit  406  receives the voltage Va from the power supply circuit  401 , and applies a predetermined voltage Vb (Va&lt;Vb in this case) to a storage battery  405  in accordance with a charge instruction from the sheet processing apparatus control circuit  409 , thereby charging the storage battery  405  to a predetermined voltage Vc (≈Vb).  
         [0044]     A battery voltage detecting circuit  407  detects the charged voltage of the storage battery  405 , and transmits the detection result as, for example, an analog signal to the A/D port of a CPU (not shown) in the sheet processing apparatus control circuit  409 . The sheet processing apparatus control circuit  409  issues a charge instruction to the charging circuit  406  in accordance with the detection result from a battery voltage detecting circuit  407 .  
         [0045]     A constant-voltage control circuit  408  controls the charged voltage Vc of the storage battery  405  to a voltage Vs (Vs≈Va−Vf, Vs&lt;Vc, forward voltage Vf of diode  403 =about 0.6 V) necessary for trimming operation, and applies the voltage Vs to the trimming driving unit  502  through a switch  413  and the relay  503 , thereby driving the trimmer  501 .  
         [0046]     The relay  503  is designed to be turned on by the supply voltage Va from the power supply circuit  401  only when the sheet processing apparatus  302  is connected to the image forming apparatus  301 .  
         [0047]     The diode  403  serves to prevent an output from the power supply circuit  401  from being applied to the trimming driving unit  502  when the voltage Vs is applied from the storage battery  405  through the constant-voltage control circuit  408  and to prevent power from the storage battery  405  from being supplied to the image forming apparatus  301 .  
         [0048]      FIG. 6  shows a case wherein the sheet processing apparatus  302  is detached from the image forming apparatus  301 . When the sheet processing apparatus  302  is detached from the image forming apparatus  301 , the supply of power from the power supply circuit  401  to the trimming driving unit  502  is cut off. In addition, the supply of power to the relay  503  is cut off and the relay  503  is opened, thereby cutting off the supply of power from the storage battery  405  to the trimming driving unit  502 .  
         [0049]     With the above arrangement, effects similar to those of the first embodiment can be obtained. That is, in the image forming apparatus designed to supply power from the power supply circuit  401  in the image forming apparatus  301  to the storage battery  405  in the sheet processing apparatus  302 , the amount of power supplied from the power supply circuit  401  at the time of trimming operation can be reduced. In addition, when the sheet processing apparatus  302  is detached from the image forming apparatus  301 , the supply of power from the power supply circuit  401  is cut off. In addition, since the relay  503  provided between the storage battery  405  and the trimming driving unit  502  is opened, the supply of power from the storage battery  405  to the trimming driving unit  502  can be reliably cut off. This makes it possible to ensure high safety.  
         [0050]     As compared with the first embodiment, the path from the storage battery  405  to the trimming driving unit  502  can be shortened, and the sheet processing apparatus  302  can be reduced in size.  
       Third Embodiment  
       [0051]      FIG. 7  is a block diagram showing the arrangements of an image forming apparatus and sheet processing apparatus according to the third embodiment. Assume that a sheet processing apparatus  302  in this embodiment performs stapling processing in the same manner as in the first embodiment.  
         [0052]     The arrangement and operation of the sheet processing apparatus  302  in this embodiment will be described below.  
         [0053]     Reference numerals  601  and  602  denote drawer connectors for supplying power from a storage battery  405  to a staple driving unit  410  through an image forming apparatus  301 .  
         [0054]     A power supply circuit  401  of the image forming apparatus  301  applies a predetermined voltage to an image forming apparatus control circuit  402 , and also applies a predetermined voltage Va to the sheet processing apparatus  302  set as an option through a connector. The image forming apparatus control circuit  402  also communicates with a sheet processing apparatus control circuit  409  in the sheet processing apparatus  302  through a connector and performs timing control to smoothly convey sheets and smoothly perform stapling operation.  
         [0055]     A charging circuit  406  receives the voltage Va from the power supply circuit  401 , and applies a predetermined voltage Vb (Va&lt;Vb in this case) to the storage battery  405  in accordance with a charge instruction from the sheet processing apparatus control circuit  409 , thereby charging the storage battery  405  to a predetermined voltage Vc (≈Vb).  
         [0056]     A battery voltage detecting circuit  407  detects the charged voltage of the storage battery  405 , and transmits the detection result as, for example, an analog signal to the A/D port of a CPU (not shown) in the sheet processing apparatus control circuit  409 . The sheet processing apparatus control circuit  409  issues a charge instruction to the charging circuit  406  in accordance with the detection result from the battery voltage detecting circuit  407 .  
         [0057]     A constant-voltage control circuit  408  controls the charged voltage Vc of the storage battery  405  to a voltage Vs (Vs≈Va−Vf, Vs&lt;Vc, forward voltage Vf of diode  403 =about 0.6 V) necessary for stapling operation, and applies the voltage Vs to the staple driving unit  410  through a switch  413  and the drawer connectors  601  and  602 , thereby driving a stapler  312 .  
         [0058]     The drawer connectors  601  and  602  are designed to be rendered conductive only when the sheet processing apparatus  302  is connected to the image forming apparatus  301 . The diode  403  serves to prevent an output from the power supply circuit  401  from being applied to the staple driving unit  410  when the voltage Vs is applied from the storage battery  405  through the constant-voltage control circuit  408  and to prevent power from the storage battery  405  from being supplied to the image forming apparatus  301 .  
         [0059]      FIG. 8  shows a case wherein the sheet processing apparatus  302  is detached from the image forming apparatus  301 . When the sheet processing apparatus  302  is detached from the image forming apparatus  301 , the supply of power from the power supply circuit  401  to the staple driving unit  410  is cut off. In addition, when the drawer connectors  601  and  602  are detached, the supply of power from the storage battery  405  to the staple driving unit  410  is also cut off.  
         [0060]     With the above arrangement, effects similar to those of the first embodiment can be obtained.  
       Fourth Embodiment  
       [0061]      FIG. 9  is a block diagram showing the arrangements of an image forming apparatus and sheet processing apparatus according to the fourth embodiment. Assume that a sheet processing apparatus  302  in this embodiment performs so-called booklet processing, i.e., binding a bundle of a plurality of sheets after image formation.  
         [0062]     The arrangement and operation of the sheet processing apparatus  302  in this embodiment will be described below.  
         [0063]     Reference numeral  701  denotes a booklet processing unit which bends supplied sheets and pastes cover sheets by using a heating unit (not shown);  702 , a booklet processing driving unit which drives the booklet processing unit  701 ;  703 , a switch which is turned on by a switch press member  704  only when the sheet processing apparatus  302  is connected to an image forming apparatus  301 ; and  705 , a switch which is turned on by a switch press member  706  only when the door of the sheet processing apparatus  302  is closed.  
         [0064]     A power supply circuit  401  of the image forming apparatus  301  applies a predetermined voltage to an image forming apparatus control circuit  402  and applies a predetermined voltage Va to the sheet processing apparatus  302  set as an option through a connector. The image forming apparatus control circuit  402  also communicates with a sheet processing apparatus control circuit  409  in the sheet processing apparatus  302  through a connector to perform timing control to smoothly convey sheets and perform booklet processing operation.  
         [0065]     A charging circuit  406  receives a voltage Va applied from the power supply circuit  401 , and applies a predetermined voltage Vb (Va&lt;Vb in this case) to a storage battery  405  in accordance with a charge instruction from the sheet processing apparatus control circuit  409 , and charges the storage battery  405  to a predetermined voltage Vc (=. Vb).  
         [0066]     A battery voltage detecting circuit  407  detects the charged voltage of the storage battery  405 , and transmits the detection result as, for example, an analog signal to the A/D port of a CPU (not shown) in the sheet processing apparatus control circuit  409 . The sheet processing apparatus control circuit  409  issues a charge instruction to the charging circuit  406  in accordance with the detection result from the battery voltage detecting circuit  407 .  
         [0067]     A constant-voltage control circuit  408  controls the charged voltage Vc for the storage battery  405  to a voltage Vs (Vs≈Va−Vf, Vs&lt;Vc, forward voltage Vf of diode  403 =about 0.6 V) necessary for booklet processing operation, and applies the voltage Vs to the booklet processing driving unit  702  through a switch  413  and the switches  703  and  705 , thereby driving the booklet processing unit  701 .  
         [0068]     The diode  403  serves to prevent an output from the power supply circuit  401  from being applied to the booklet processing driving unit  702  when the voltage Vs is applied from the storage battery  405  through the constant-voltage control circuit  408  and to prevent power from the storage battery  405  from being supplied to the image forming apparatus  301 .  
         [0069]      FIG. 10  shows a case wherein the sheet processing apparatus  302  is detached from the image forming apparatus  301 . When the sheet processing apparatus  302  is detached from the image forming apparatus  301 , the switch  703  is opened, and power supplied from the power supply circuit  401  and storage battery  405  to the booklet processing driving unit  702  is cut off. Likewise, when the door of the sheet processing apparatus  302  is open, the switch  705  is opened to cut off the power supplied from the power supply circuit  401  and storage battery  405  to the booklet processing driving unit  702 .  
         [0070]     With the above arrangement as well, effects similar to those of the first embodiment can be obtained.  
         [0071]     Note that this embodiment has exemplified the arrangement comprising the switch which is turned on by the switch press member  704  only when the sheet processing apparatus  302  is connected to the image forming apparatus  301  and the switches  703  and  705  which are turned on by the switch press member  706  only when the door of the sheet processing apparatus  302  is closed. However, one switch may be used instead of these switches, and may be designed to be turned on only when the sheet processing apparatus  302  is connected to the image forming apparatus  301  and the door of the sheet processing apparatus  302  is closed.  
         [0072]     The above first to fourth embodiments each have exemplified the arrangement using a plurality of electric double layer capacitors for a storage battery. However, the present invention is not limited to the electric double layer capacitor and, for example, a secondary battery or capacitor may be used.  
         [0073]     In addition, the above first to fourth embodiments each have exemplified the optional function of the sheet processing apparatus  302 , and the sheet processing apparatuses in the respective embodiments may be obviously exchanged between them.  
         [0074]     As many apparently widely different embodiments of the present invention can be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments thereof except as defined in the appended claims.  
       CLAIM OF PRIORITY  
       [0075]     This application claims priority from Japanese Patent Application No. 2004-324077 filed on Nov. 8, 2004, the entire contents of which are hereby incorporated by reference herein.