Patent Publication Number: US-9889683-B2

Title: Sheet cutting apparatus and image forming apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Division of application Ser. No. 14/288,645 filed May 28, 2014, the entire contents of all of which are incorporated herein by reference. 
    
    
     FIELD 
     Embodiments described herein relate to a technology in which the occurrence of a defect caused by the falling of a cutter in a guillotine type sheet cutting apparatus from a specific standby position as time goes by is prevented. 
     BACKGROUND 
     For example, in a guillotine type sheet cutting apparatus carried in a printer, a sheet is cut by a cutter which is driven in a vertical direction by a motor. 
     In the guillotine type sheet cutting apparatus, the cutter waits at a home position when carrying out no cutting operation and falls to a sheet below to cut the sheet by a guillotine operation when carrying out a cutting operation. 
     After cutting the sheet, the cutter is lifted to the home position again to wait for a next cutting operation. 
     However, in the guillotine type sheet cutting apparatus, the cutter, if made to wait at the home position for along time, may fall slowly in a direction of gravity under the effect of a vibration applied to the sheet cutting apparatus and the holding torque of a motor for driving the cutter. 
     The cutter, which falls slowly from the home position as time goes by as stated above, projects into a conveyance path for conveying a sheet to be cut, thus, the sheet cutting apparatus hinders the conveyance of a sheet conveyed to a position below the cutter to be cut, which may lead to the occurrence of a sheet block (the called jam). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view illustrating a constitution of an image forming apparatus; 
         FIG. 2  is a perspective view of a sheet cutting apparatus; 
         FIG. 3  is a back view illustrating a sheet cutting apparatus the cutter of which is at a home position; 
         FIG. 4  is a back view illustrating a sheet cutting apparatus the cutter of which is at a cutting completion position; 
         FIG. 5  is a block diagram illustrating a constitution of an image forming apparatus; 
         FIG. 6  is a flowchart illustrating operations of a sheet cutting apparatus; 
         FIG. 7  is a schematic diagram illustrating a sheet cutting apparatus the cutter of which is at a home position; 
         FIG. 8  is a schematic diagram illustrating a sheet cutting apparatus cutting a sheet; 
         FIG. 9  is a schematic diagram illustrating a sheet cutting apparatus the cutter of which falls; 
         FIG. 10  is a schematic diagram illustrating a sheet cutting apparatus which causes a sheet jam; 
         FIG. 11  is a flowchart illustrating operations of a sheet cutting apparatus; 
         FIG. 12  is a diagram exemplarily illustrating an accumulated printing times of an image forming apparatus; and 
         FIG. 13  is a diagram exemplarily illustrating the relation between an accumulated printing times and elapsed time X. 
     
    
    
     DETAILED DESCRIPTION 
     Generally, in accordance with one embodiment, a sheet cutting apparatus includes a cutting position, a cutter, a motor, a drive mechanism, a drive control section, a determination section and a return control section. 
     A sheet is cut at the cutting position 
     The cutter, which is of a guillotine type, moves between the cutting position and a home position above the cutting position. 
     The drive mechanism transfers a drive force from the motor to the cutter to move the cutter between the home position and the cutting position. 
     The drive control section enables the cutter to fall from the home position to the cutting position when cutting a sheet by the cutter and then return the cutter to the home position. 
     The determination section determines whether or not a given period of time elapses from the last return completion of the cutter to the home position. 
     The return control section returns the cutter to the home position if the determination section determines that a given period of time elapses from the last return completion of the cutter to the home position. 
     A First Embodiment 
     A first embodiment is described first with reference to accompanying drawings. 
       FIG. 1  is a sectional view illustrating a constitution of an image forming apparatus. As shown in  FIG. 1 , an image forming apparatus  100  of the present embodiment comprises a recording medium conveyance mechanism  113  configured to convey a roll recording medium  111 ; a head  114  configured to form an image on the recording medium  111 ; a platen  115  configured at a position opposite to the head  114  across a recording medium conveyance path; a sheet cutting apparatus  200  configured at a position more downstream than the head  114  along the recording medium conveyance direction; and a control section  118  configured to control operations of the sheet cutting apparatus  200 . 
     When the recording medium  111  is label paper, the image forming apparatus  100  may comprise a gap sensor  112  for detecting the gap between labels. 
     The control section  118  further controls operations of the recording medium conveyance mechanism  113  and the head  114 . 
       FIG. 2  is a perspective view illustrating a drive mechanism of the cutter  205  in the sheet cutting apparatus  200 . Further,  FIG. 3  is a back view illustrating the sheet cutting apparatus  200  the cutter  205  of which is at a home position, and  FIG. 4  is a back view illustrating the sheet cutting apparatus  200  the cutter  205  of which is at a cutting completion position (the lowest position in a cutting operation). Further, for the sake of convenience of description, a gear  201 A and a cutter drive section  201  which will be described later are saved in  FIG. 4 . 
     In the present embodiment, the sheet cutting apparatus  200  is described as an example which cuts a recording medium by displacing the cutter  205  in a vertical direction towards the recording medium, however, the sheet cutting apparatus  200  may not be an apparatus of this type. 
     As shown in  FIG. 2 - FIG. 4 , the sheet cutting apparatus  200  comprises an elastic body  204  locked to a frame  203 ; a cutter  205  connected with the elastic body  204 ; a cutter drive section  201  for driving the cutter  205 ; a gear  201 A driven to rotate by the cutter drive section  201 ; a pin  201 B arranged on the radius of the gear  201 A; a lever  206  which has a pin inserting hole  206 B on one end into which the pin  201 B is inserted and a drive hole  206 C in the center part into which a drive pin  205 A of the cutter  205  is inserted, and is rotationally supported by the frame  203  through a fulcrum  206 D on the other end; a home position sensor  202  for detecting a detection hole  205 B of the cutter  205 ; and fixed teeth  207  fixed on the frame  203 . 
     The elastic body  204  consisting of a spring urges the cutter  205  away from the recording medium  111 . 
     The cutter drive section  201  may be a DC motor, a stepping motor and the like. 
     The home position sensor  202  detects whether or not the cutter  205  is at the home position, that is, a position furthest from the fixed teeth  207  (e.g. the state shown in  FIG. 3 ), by detecting the light through the detection hole  205 B. Further, the home position sensor  202  is exemplarily described as an optical sensor herein, however, it is not limited to this, it may also be, for example, a mechanical sensor. 
     If the cutter drive section  201  carries out a drive operation, then the gear  201 A mounted on a rotation shaft of the cutter drive section  201  rotates. If the gear  201 A rotates, then the pin  201 B rotates and the lever  206  is displaced downward. The lever  206  rotates downward by taking the fulcrum  206 D as a fulcrum, in this way, the pin inserting hole  206 B becomes a force point and the drive hole  206 C becomes an action point, thereby displacing the cutter  205  downward to the cutting completion position. 
     The recording medium  111  is conveyed between the cutter  205  and the fixed teeth  207 . Therefore, the recording medium  111  is cut by the cutter  205  and the fixed teeth  207 . At this time, the cutter  205  is at the position shown in  FIG. 4 . 
     If the cutter drive section  201  further carries out a drive operation, then the pin  201 B moves upwards to lift the lever  206 . The lever  206  rotates upwards by taking the fulcrum  206 D as a fulcrum, then the drive pin  205 A is lifted and the cutter  205  is returned to the home position. 
       FIG. 5  is a block diagram illustrating a constitution of the image forming apparatus  100 . As shown in  FIG. 5 , the image forming apparatus  100  comprises a CPU  118  serving as a control section; a gap sensor  112 ; a recording medium conveyance mechanism  113 ; a head  114 ; a control panel  301  serving as an input/output apparatus; a communication interface  302  (hereinafter interface is referred to as I/F) communicating with an external apparatus; a memory  303 ; a cutter drive section  201 ; a home position sensor  202 ; and a storage apparatus  309  consisting of a hard disc drive. 
     The control section  118  communicates with a host computer  220  (hereinafter referred to as a HOST) through the communication I/F  302 . 
     The control section  118  acquires, for example, the detection signals in the gap sensor  112  and the home position sensor  202  and controls the recording medium conveyance mechanism  113 , the head  114  and the cutter drive section  201 . The various processing carried out by the control section  118  herein can be realized by executing various programs loaded in the memory  303  using the control section  118  serving as a CPU. Part of or all the various programs that should be executed in the sheet cutting apparatus may be stored in, for example, the storage apparatus  309 . 
       FIG. 6  is a flowchart illustrating the operations of a cutter apparatus. 
     After the former printing operation is ended, if the image forming apparatus  100  receives a printing job in ACT  601  (YES in ACT  601 ), the flow proceeds to ACT  605 . On the other hand, the flow proceeds to ACT  602  if no printing job is received (NO in ACT  601 ). 
     In ACT  602 , the control section  118  (determination section) starts to count up the elapsed time X elapsing from the ending time of the former printing operation. 
     In ACT  603 , if the control section  118  (determination section) determines that the counted time is longer than the elapsed time X (YES in ACT  603 ), the flow proceeds to ACT  604 . The elapsed time X may be set to, for example, 60 min. On the other hand, the flow returns to ACT  601  if the control section  118  (determination section) determines that the counted time is shorter than the elapsed time X (NO in ACT  603 ). 
     In ACT  604 , the control section  118  sets a flag and then the flow returns to ACT  601 . 
     In ACT  605 , the control section  118  clears the time counted up from ACT  602 , and then the flow proceeds to ACT  606 . That is because if the count of the timer is not reset, the operation in ACT  608  (the return operation of the cutter to the home position) is carried out every time the image forming apparatus carries out a printing operation. If the cutter is initialized every time a printing operation is carried out, then it will take a long time from the moment a printing job is received to the moment the printing job is finished. 
     In ACT  606 , the control section  118  determines whether or not a flag is set in ACT  604 , if a flag is set in ACT  604 , the flow proceeds to ACT  607 . On the other hand, if no flag is set, the control section  118  makes the flow proceed to ACT  609 . 
     In ACT  607 , the control section  118  resets the flag set in ACT  604 . That is because if the flag is not reset, then the cutter initialization in ACT  608  is carried out every time a printing operation is carried out. 
     In ACT  608 , the control section  118  (return control section) initializes the cutter. Specifically, the cutter  205  in the sheet cutting apparatus  200  is lifted and returned to the home position. In this way, it is prevented that the cutter  205  falling from the home position as time goes by contacts with a sheet conveyed as a target to be cut. The initialization of the cutter is carried out immediately before the sheet is cut, therefore, the contact between the cutter and the sheet is surely prevented. That is because if the cutter is initialized immediately before the sheet is cut, then the possibility is reduced that the cutter falls again after returned to the home position and contacts with the sheet. 
     In ACT  609 , the control section  118  controls to form an image on the sheet. 
     In ACT  610 , the control section  118  (drive control section) drives the cutter drive section  201  to cut the conveyed sheet at a cutting position. 
     The cutter initialization operation in ACT  608  shown in  FIG. 6  is described below in detail. As shown in  FIG. 7 , a sheet  701  serving as a printing medium moves in a sheet conveyance path  702  and stops at a cutting position, and the cutter  205  falls vertically. Then, the sheet  701  is cut, as shown in  FIG. 8 . However, as shown in  FIG. 9 , if the cutter  205  falls as time goes by or falls due to other reason, the contact between the conveyed sheet  701  with the fallen cutter  205  causes a jam, as shown in  FIG. 10 . 
     In ACT  602  shown in  FIG. 6 , the elapsed time X serving as a trigger for the cutter initialization may not be counted up based on the printing completion. For example, the moment when the cutter  205  returns to the home position last time may be taken as the trigger. Further, for example, the moment the former printing job is received maybe taken as the trigger to count up the elapsed time X. 
     The count of the timer described in ACT  605  shown in  FIG. 6  is not necessarily to be cleared after the printing job is received in ACT  601  and before the flag determination in ACT  606 , it can be cleared at any action after a printing job is received and before a printing operation is ended. 
     The flag reset in ACT  607  shown in  FIG. 6  is not necessarily to be carried out after the flag determination in ACT  607  and before the cutter initialization in ACT  608 , it can be carried out at any action after the flag determination in ACT  606  and before the flag setting in ACT  604 . 
     A Second Embodiment 
     Next, a second embodiment is described with reference to accompanying drawings. As a modification of the first embodiment, the basic apparatuses constitution in the second embodiment is the same as that in the first embodiment. A member having the same function as one described in the first embodiment is hereinafter denoted by the same reference sign and is therefore not described repeatedly. 
     The motor and the drive mechanism, after being used for many times, will deteriorate as time goes by. The deterioration of such a drive mechanism will make it easy for the cutter waiting at the home position to move downward or contrarily make it hard for the cutter at the home position to move. 
     Therefore, due to the deterioration state of the motor and the drive mechanism, it is necessary to control the return operation of the cutter to the home position after a given time X elapses. 
       FIG. 11  is a flowchart illustrating the operations of a sheet cutting apparatus according to the second embodiment. Further, a case where a cutter waiting at a home position falls easily since a drive mechanism is deteriorated after repeating a cut operation in a sheet cutting apparatus is listed herein as an example. 
     After the printing operation in ACT  609  is ended, a printing times counter counts the printing times of the image forming apparatus  100  in ACT  1101 . The printing times refers to an accumulated printing times carried out in the image forming apparatus.  FIG. 12  is a table illustrating an accumulated printing times. 
     In ACT  1102 , the control section  118  (timer control section) changes, according to the printing times counted in ACT  1101 , the elapsed time X, which serves as a trigger for the cutter initialization in ACT  609 , elapsing from the completion of the former printing operation. 
     Herein, if the elapsed time X elapsing from the former printing operation and serving as a trigger for the cutter initialization is specified, then the cutter  205  falls to a height (the height of the front end of the cutter in the sheet conveyance path), which may cause a sheet jam, before the elapsed time X elapses, which may lead to a contact with the conveyed sheet  701 . Thus, in order to prevent the contact between the cutter  205  which is likely to fall as deteriorated after being used for a long time with a conveyed sheet  701 , the elapsed time is shortened corresponding to an increase in printing times. The relation between the printing times and the elapsed time X is presented by, for example, a table shown in  FIG. 13 . The value of the elapsed time X decreases as the printing times increases. 
     Further, it is preferred that the printing times are reset after the motor and the drive mechanism used in the sheet cutting apparatus  200  are replaced or maintained. The elapsed time X is changed because the deterioration of the motor and the drive mechanism occurring as time goes by is taken into consideration. 
     Further, a case where the repeated cutting operation of the sheet cutting apparatus makes it easy for a cutter waiting at a home position to fall is exemplarily illustrated herein, on the contrary, in a case where the deterioration of a drive mechanism due to the repeating of the cutting operation makes it hard for the cutter waiting at the home position to move, the given time X may be increased in response to an increase in a printing times (that is, the cutting times by the cutter). 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the invention. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the invention. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention.