Abstract:
A sheet cutting device utilizing cutter blades as a position detection mechanism and a method of reporting cutter malfunctions is provided. The sheet cutting device including a cutter having a pair of cutter blades, one of the blades connected to a cutter driving mechanism for moving the blade through a cutting cycle, a power source is connected to one of the blades so that a circuit is closed when the blades contact one another, and a current sensing device in connection with the circuit to identify when the blades are in physical contact.

Description:
TECHNICAL FIELD 
   The present invention relates in general to utilizing cutter blades in a printer for identifying the position of the blades and for reporting cutter failures; and in particular, to utilizing cutter blades as an electrical switch to indicate when the cutting blades are in the fully open position and operating properly or malfunctioning and to a method of reporting the malfunction. 
   BACKGROUND INFORMATION 
   Many devices such as facsimiles and printers utilize continuous rolls of paper which require cutters. Some of these devices have a separate monitoring device to indicate when the blades are fully open and paper may be fed through the cutters. However, these cutter position devices do not indicate to an operator where in the cutting cycle the blades may not be closing or opening properly to allow an operator to accurately identify and correct malfunctions. 
   Various malfunctions may occur in the cutting process resulting in failure to cut, failure to completely cut material, and resulting in jamming of paper in the device. These failures can cause printer failure and loss of time and possibly sales for an operator of the printer. For example, it is very common to have point of sale (POS) printers for use with cash registers and check card/credit card printers. When the printer fails customers are forced to wait often resulting in loss of sales for the operator. Heretofore the printer operators only know when the cutters fail due to the fact that they have to manually cut the receipt from the paper roll, or there is a paper jam shutting down the printer. When there is a paper jam the operator may not realize that the jam is caused by the cutters failing to open completely, as opposed to a failure or malfunction in the printing system. 
   Several common types of cutter failures may appear random, but they indicate a problem which if addressed early will prevent any undue loss of time or operation of the printer. Other malfunctions may result in failure of the printer. If these symptoms of cutter blade wear, damage, or improper function of blades during the cutting process are noted and identified to the operator, the cutter may be disabled and service provided without excessive loss in time and operation of the printer. 
   It would be a benefit, therefore, to utilize the cutter blades as a switch to indicate when the cutter blades are fully open. It would be a further benefit to have a cutter blade position switch and a method which indicates when within a cutting cycle the cutter is malfunctioning. It would be a still further benefit to utilize the cutter blades to indicate when the cutter blades are malfunctioning and warn an operator or another of the malfunction. 
   SUMMARY OF THE INVENTION 
   It is thus an object of this invention to provide a cutter blade position switch utilizing the cutter blades to indicate when the blades are fully open. 
   It is a further object of this invention to provide a method of indicating when cutters are malfunctioning utilizing the cutter blades to indicate when fully open. 
   Accordingly, a sheet cutting device utilizing cutter blades as a position detection mechanism and a method of reporting cutter malfunctions is provided. The sheet cutting device includes a cutter having a pair of cutter blades, one of the blades connected to a cutter driving mechanism for moving the blade through a cutting cycle, a power source connected to one of the blades so that a circuit is closed when the blades contact one another, and a current sensing device in connection with the circuit to identify when the blades are in physical contact. 
   The cutter driving mechanism may include a pulse generator, a stepper motor drive, and a stepper motor. A pulse counter may be utilized to track the cutting cycle. By comparing the stage of the cutting cycle in which the blade switch opens and closes it can be determined if the cutter is performing properly. 
   The cutting device may include a processing unit for stopping and starting the cutter drive mechanism and monitoring the blade switch and counting the pulses to determine the position in the cutting cycle. By monitoring the switch positon and the pulse count compared to known data it can be determined if the cutter is working properly. If the cutter is not working properly the cutter motor drive may be stopped and an error message sent to a display unit. The processor may send a signal to restart the motor drive and attempt to correct the problem before sending an error message. 
   The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which: 
       FIG. 1  is a perspective view of a continuous paper roll printing device, with the cover removed, utilizing the cutter blades as a cutter blade position detection switch. 
       FIG. 2  is a block diagram showing electrical circuitry of a printing device of the present invention utilizing the cutter blades as a position detection mechanism. 
       FIG. 3  is a representative plot of motor pulse steps during a full cutting cycle. 
       FIG. 4  is a representative plot of the physical position of the cutter blades as they proceed through a full cutting cycle resulting in a successful cut of paper. 
       FIG. 5  is a representative plot of the switch signal formed by the blades opening and closing in a complete, successful cut of paper. 
       FIG. 6  is a representative plot of the opening Sw 1  and the closing Sw 2  of the switch at a position indicative of an incomplete cut of paper. 
       FIG. 7  is a representative plot of the opening Sw 1  and the closing Sw 2  of the switch at a position indicative of blade lock. 
       FIG. 8  is a representative plot of the opening Sw 1  and the closing Sw 2  of the switch at a position indicative of incomplete blade opening. 
       FIG. 9  including  9 A is a flowchart of the invention as shown in  FIGS. 1 through 8 . 
   

   DETAILED DESCRIPTION 
   Refer now to the drawings wherein depicted elements are not necessarily shown to scale and wherein like or similar elements are designated by the same reference numeral through the several views. 
     FIG. 1  is a perspective view of a continuous paper roll printing device  10 , with the cover removed, utilizing cutter blades  12  and  14  as a cutter blade position detection switch. Printer  10  includes a continuous roll of paper  16 , first blade  12 , second blade  14 , printer frame  18 , and stepper motor  20 . 
   As shown in  FIG. 1 , first blade  12  is a stationary blade and second blade  14  is a shear blade, each constructed of an electrically conductive material. In this embodiment, cutter blade  12  is connected to frame  18  with non-conductive bushings  22 . Blade  14  is movably connected to frame  18  which is ground. A power source  24 , such as but not limited to a DC source, is connected to first blade  12 . A resistor  26  may be connected between power source  24  and blade  12 . A non-conductive material  28  may be connected between a portion, or bonded to a portion of blade  12  or blade  14  to prevent conductive contact when the blades are not in a cutting position, but, the blades  12  and  14  are loaded against each other. When blades  12  and  14  are in the fully open position, as shown, there is no electrical contact between blade  12  and  14 . When blades  12  and  14  contact during the cutting cycle a current will flow which can be detected. 
   Stepper motor  20  is operationally connected to blade  14  by gears  21   a ,  21   b , and  21   c  to move blade  14  through a cutting cycle. When a cutting cycle is initiated, blades  12  and  14  contact one another along the conductive and cutting portion thereof, closing the circuit between power source  24  and frame ground  18  providing an indicating current. 
     FIG. 2  is a block diagram showing electrical circuitry of printing device  10  of the present invention utilizing cutter blades  12  and  14  as a position detection mechanism. As shown, cutting blades  12  and  14  are fully open to pass paper  16  ( FIG. 1 ) therebetween. Paper  16  is fed through printer  10  and cutter blades  12 ,  14  by a motor (not shown) connected to CPU  30 . CPU  30  includes a read only memory (ROM) storing programs for control by CPU  30  and stores constants, such as but not limited to pulse and time information for completing a cutting cycle, and current detection positions. CPU  30  may further include a random access memory (RAM) for storing variables and downloaded printing information and the like. 
   To initiate the cutting process a cutter driving mechanism  32  is activated by CPU  30 . Cutter driving mechanism  32  includes a stepper motor pulse generator  34 , a stepper motor driver  36 , and stepper motor  20 . Stepper motor  20  is mechanically connected  21  to blade  14  to move blade  14  in incremental steps through the cutting cycle. For each step, stepper motor pulse generator  34  generates an electrical step pulse signal. Stepper motor driver  36  receives the electrical step pulse signals from pulse generator  34  and activates stepper motor  20 . A pulse or step counter  38  receives the electrical step pulse signals from stepper motor pulse generator  34 . Step counter  38  counts these step pulse signals as part of the cutting cycle and in combination with signals from blades  12  and  14  it can be determined precisely when blades  12 ,  14  are fully opened or closed. Pulse counter  38  may be reset to zero after each cutting cycle. 
   When the cutting cycle begins, blades  12  and  14  should contact one another along a conductive portion closing the circuit between voltage source  24  and blade  14  which is connected to frame  18  ground (FIG.  1 ), thus performing as an electric switch. A current detection device  40  may be connected to the line between voltage source  24  and blades  12 ,  14  and to CPU  30  or a direct connection to CPU  30  for receiving a signal when blade switch  12 ,  14  is closed or opened, may be used. 
   CPU  30  may be connected to a display unit  42  for displaying operating information such as cutter malfunction determined from the opening and closing of blades  12 ,  14  in relation to the timing of the occurrence within the cutting cycle. Display unit  42  includes a LED (light-emitting device), a LCD (liquid crystal display) or the like, and displays information such as that there is incomplete cutting, blade lock, or that blades  12 ,  14  are not fully open. Error codes and or recommendations such as “call a service representative,” “disconnect cutters,” may be displayed. 
   CPU  30  may also be connected to a network  44  such as the Internet, in a manner well known in the art, which connects to the repair service provider  46 . In this manner, an error message may be sent to service provider  46  for prompt response. 
   With reference to  FIGS. 1 through 9 ,  FIGS. 3 through 8  are representative plots of pulse step counts and current detection indicating when blades  12 ,  14  are fully open or in contact with one another.  FIG. 3  is a representative plot of pulse signals sent to stepper motor  20  to move blade  14  through a complete cutting cycle. Point “A” represents the approximate point at which the signal is sent and blade  14  begins to move. Point “B” is the approximate point at which blades  12 ,  14  should be in contact and the circuit across blades  12 ,  14  is closed. Point “C” is the approximate point at which cutter blades  12 ,  14  begin to move apart. Point “D” is the approximate point at which blades  12 ,  14  are approaching fully open. Point “E” is the point at which blades  12 ,  14  should be in the fully open position, and thus the circuit is open. As shown in  FIGS. 3 through 8 , points “A” through “E” are approximate points, however, the number of pulses and the incremental movement of blade  14  for each step may be accurately calculated through the cutting cycle. 
     FIG. 4  is a representative plot of the physical position of cutter blades  12 ,  14  as they go through a full cutting cycle in a successful cut of the paper.  FIG. 5  is a representative plot of the switch signal formed by blades  12  and  14  opening and closing. The switch being open (Sw 1 ) when blades  12  and  14  are not in electrical contact and the switch being closed (Sw 2 ) when blades  12  and  14  are in electrical contact.  FIG. 5  represents a complete and successful cut wherein blades  12 ,  14  contact between points “A” and “B”, designated by P 1 , closing the circuit, and wherein blades physically open between points “D” and “E”, designated by P 2 , opening the circuit. 
   The closing and opening of the switch in relation to the pulse position at the time of switch operation can be utilized to properly diagnose a problem and predict and prevent failures. One malfunction, “cutter drive failure”, which is not shown graphically is if the switch fails to close P 1  between points “A” and “B”. This malfunction can be immediately addressed by disabling the cutter drive and manually tearing the paper until the problem can repaired. 
     FIG. 6  is a representative plot of the opening Sw 1  and the closing Sw 2  of the switch in a position indicative of in an incomplete cut. In an incomplete cut, the switch opens Sw 1  at P 2  which is before point “C”, indicating that blades  12  and  14  are no longer in contact before reaching point “C.” This is indicative of worn blades  12 ,  14  which may be replaced before the problem worsens. 
     FIG. 7  is a representative plot of the opening Sw 1  and the closing Sw 2  of the switch at a position indicative of blade lock. As shown, blades  12 ,  14  contact and the switch closes Sw 2  at P 1  between points “A” and “B” which is proper operation. However, the switch opens Sw 1  at P 2  which is after point “C” but before point “D.” This is commonly caused by a burr or wear point on blades  12 ,  14  that causes the blades to hang on each other and open too soon in the cutter open sequence resulting in an incomplete cut. 
     FIG. 8  is a representative plot of the opening Sw 1  and the closing Sw 2  of the switch at a position indicative of incomplete blade opening. Incomplete blade opening results when blades  12 ,  14  remain in contact after the cutting cycle is completed and is indicated by the switch remaining closed Sw 2  or opening Sw 1  after point “E.” This malfunction can be catastrophic in that it can cause a paper jam. When this malfunction is detected, the printer logic  30  may disable the cutter and instruct the operator to manually open the cutter and to use the tear bar. A service call to the repair service provider should be made. 
     FIGS. 9 and 9A  are flowcharts of the system of  FIGS. 1 through 8 . When the paper driving motor (not shown) is stopped the cutting cycle is started. A recycle counter step S 1  may be set for a predetermined number of times that the system will try to correct an error. In step S 2  pulse counter  30  is reset to zero. Simultaneously, stepper motor  20  is engaged in step S 3  and pulse counter  30  is started in step S 4 . Each pulse is tested in step S 5 , to determine if the switch formed by blades  12 ,  14  is in the proper position, either open or closed, as predetermined for each pulse. In step S 6 , the test for each pulse begins, for example at point “A” shown in  FIGS. 1 through 8 , the switch should be open, in step  9  the switch would be tested and if the switch is open the process would continue for the next pulse, if the switch is closed, CPU  30  in steps S 10  through S 16  determines whether to attempt to open and close blades  12 ,  14  and begin the cycle at step S 2  or to display an error S 16  and stop motor  20 , step S 12 , and counter  30 , step S 13 . In step S 6 , if the switch is supposed to be closed at that particular pulse, for example at point “C” shown in  FIGS. 1 through 8 , the circuit is tested in step S 7 , if the circuit is open, CPU  30  in steps S 10  through S 16  determines whether to begin the cutter cycle again or display an error S 16  and stop motor  20 , step S 112 , and counter  30 , step S 113 , if the circuit is closed. 
   Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations, such as but not limited to, changing which blade is hot and which is grounded, can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.