A control system for a printer

Abstract: A control system for controlling the movement of a cutting device (74) mounted on a carriage (52) in a printer (10) between a home position to a record media cut position. The carriage (52) has photosensing means (80) secured thereto which is operably associated with a first reflecting member (82) at the home position of the carriage (52) and with a second reflecting member (84) at the record media cut position of the carriage (52). The second reflecting member (84) is operably associated with the photosensing means (80) for partial cut or for full cut of record media by the cutting device (74). The movement of the carriage (52) is controlled by the output of the photosensing means (80) coupled to control means (160,162,164) responsive to the different intensities of the reflected light received by a light receiving element of the photosensing means (50) from the first and second reflecting members (82,84).

Description: The present invention relates to a control system for a printer and more particularly to a control system for controlling the movement of a cutting device mounted on a carriage in the printer. In a dot matrix printer which is used for receipt, slip and journal printing operations, the receipt paper from a supply roll thereof is cut after each receipt printing operation and a receipt is given to the customer. The mechanism for cutting the receipt paper has commonly been a tool, a blade or a cutter wheel. An arrangement of a cutting mechanism in a conventional printer includes a motor which drives a carriage by means of a belt and a lead screw . The cutting mechanism is a blade carried by the carriage and cooperates with a fixed blade for cutting the receipt paper and providing a receipt. The carriage has a light shielding plate attached thereto which is operable with three light transmission type photosensors. The light transmission type photosensors each include a light emitting element and a light receiving element which is positioned in facing relationship with the light emitting element. The photosensors are located in the home position, and partial cut position and the full cut position of the cutting mechanism. The latter position being disposed at the end of the paper cutting operation. The light shielding plate is provided on the carriage for shielding the light of the respective photosensor. The position of the carriage is sensed in the manner of presence or absence of an output from the respective photosensor for controlling the movement of the cutting blade. At least two photosensors are required to provide a cutting operation for either a partial cut or a full cut of the receipt paper (e.g. US-A-4 693 151). If both a partial cut and a full cut are desired, the operation requires all three photosensors. In this regard and using the cutting mechanism in a conventional printer, the number of components is increased and the manufacturing and assembling steps are complicated so that a reduction in cost cannot be attained. An object of the present invention is to provide a control system for controlling the movement of the cutting mechanism whereby the number of components can be reduced, the assembling operation can be facilitated and the manufacturing cost can be reduced. Accordingly, the present invention provides a control system for controlling the movement of a cutting device mounted on a carriage in a printer including drive means for moving said carriage in a reciprocal manner along a rectilinear guide path, characterized by photosensing means secured to said carriage and having a light emitting element and a light receiving element, a first reflecting member fixed relative to said guide path and arranged, when said carriage is at a first position in said guide path,to receive light from said light emitting element and to reflect light back to said light receiving element, the light received by said light receiving element from said first reflecting member being of a first intensity, a second reflecting member fixed relative to said guide path and spaced from said first reflecting member, said second reflecting member being arranged, when said carriage is at a second position in said guide path, to receive light from said light emitting element and to reflect light back to said light receiving element, the light received by said light receiving element from said second reflecting member being of a second intensity different from said first intensity, and control means responsive to the reflected light received by said light receiving element from said first and second reflecting members for controlling the movement of said carriage along said guide path. An embodiment of the present invention will now be described by way of example with reference to the accompanying drawings, in which:- Fig. 1 is a perspective view of a dot matrix printer incorporating the subject matter of the present invention; Fig. 2 is a right side elevational view in diagrammatic form showing the arrangement of certain elements of the printer; Fig. 3 is a left side elevational view in diagrammatic form showing the arrangement of such certain elements of the printer; Fig. 4 is an elevational view showing the arrangement of the cutting mechanism and the photosensor with the reflecting elements; Fig. 5 is a perspective view of a preferred embodiment of the structure shown in Fig. 4; Figs. 6A, 6B and 6C are diagrams showing the relationship between the positions of the reflecting elements and the magnitudes of the output voltages of the photosensor; Figs. 7A and 7B are diagrams showing the relationship between the photosensor and the magnitudes of the voltages of the photosensor in two positions thereof; Figs. 8, 9A, 9B and 10, taken together, constitute a flow chart of instructions for controlling the movement of the cutting mechanism; Fig. 11 is a diagram of the control circuit for the cutting mechanism; and Fig. 12 is a perspective view showing an arrangement of sensors and a reflecting element of a conventional printer. Referring now to Fig. 1, a printer 10 is designed as a two station, receipt/slip and journal printer. The receipt/slip printing station occupies a front portion 12 and the journal printing station occupies a rearward portion 14 of the printer. A slip table 16 is provided along the left hand side of the printer 10. A front cover 17 swings toward the right to expose certain operating parts of the printer 10. Figs. 2 and 3 are right and left side elevational views and show certain elements of the printer 10 in diagrammatic form. The receipt/slip portion 12 and the journal portion 14 include individual print wire solenoids (not shown) along with a ribbon cassette 18 for the receipt/slip printing operation and a ribbon cassette 20 for the journal printing operation. A roll 22 of receipt paper is journaled at the front of the printer 10 and the receipt paper 24 is driven and guided by appropriate pairs of rollers, as 26, 28, 30 and 32 in a path past the receipt/slip printing station for printing operation and for issuance of a receipt 33 after cutting thereof from the receipt paper 24. A supply roll 34 of journal paper is positioned in a cradle at the rear of the printer 10 and the journal paper 36 is driven and guided by appropriate pairs of rollers, as 38 and 40, in a path from the supply roll 34, past the journal printing station, and onto a take-up roll 42. A timing plate 43 (Fig. 2) is provided at the receipt/slip printing station for positioning the receipt/slip feed rolls. Fig. 4 is an elevational view and Fig. 5 is a perspective view of the receipt cutting mechanism according to a preferred embodiment of the present invention. Prior to describing the invention in detail, it is convenient to mention certain aspects of a receipt cutting operation. A first check in such operation is made as to whether or not the carriage for the cutting knife or blade is at the home position. If the carriage is not at the home position, the control mechanism or other means moves the carriage to such home position. After a printing operation is completed, the carriage is moved or driven to the cutting position to cut a receipt from the receipt paper. The cutting operation may be one of partial cut or full cut dependent upon the desires or requirements of the business. At the completion of the cutting operation, the carriage is returned to the home position. Referring now to Fig. 4, a right side plate 44 and a left side plate 46 provide support for the receipt cutting mechanism. The right side and the left side notations are provided for description of the arrangements illustrated in Figs. 4 and 5. A pair of shafts 48 and 50 are secured to the side plates 44 and 46 and provide support for a carriage 52 that is slidably moved along the shafts 48 and 50 in transverse direction on the printer 10. The carriage 52 is driven in such transverse direction by means of a reversing-type motor 54 which is suitably supported by the left side plate 46. A toothed belt 56 is trained around a pulley 58 on the end of a motor shaft 60 and around a pulley 62 on the end of a lead screw-type drive shaft 64. The drive shaft 64 is coupled by means of a threaded hub 65 associated with the carriage 52 for driving thereof across the printer 10. A knob 66 is secured to the end of the shaft 64 to be used for turning the shaft in case of a jam or for manually moving the carriage 52 to a desired position. A belt or like resilient member 68 (Fig. 5) with teeth 70 is stretched across the printer parallel to the shafts 48 and 50 and is secured to the side plates 44 and 46 by suitable means. A bracket 72 provides support for drive mechanism associated with the lead screw drive shaft 64 for driving the carriage 52 across the printer 10. A circular cutting knife or blade 74 is rotatably carried by the bracket 72 of the carriage 52 and is operably associated with a knife edge 75 of a fixed blade 76. The fixed blade 76 is suitably secured to structure between the side plates 44 and 46 of the printer 10. Rotation of the cutting blade 74 along the knife edge 75 of the fixed blade 76 operates to cut a receipt 33 from the receipt paper 24 (Fig. 5). A light reflecting type photosensor 80 is positioned above and secured to the top of the carriage 52 and is operably associated with a first light reflective plate 82 positioned in the home position of the carriage 52 and is operably associated with a second light reflective plate 84 positioned in the cutting position of the carriage 52. The photosensor 80 includes a light emitting element (not shown) facing the reflective plates 82 and 84. The plate 82 has a reflecting face or surface 86 (Fig. 4) opposed to the photosensor 80 and the plate 84 has a reflecting face or surface 88 also opposed to the photosensor 80. Figs. 6A, 6B and 6C show the relationship between the positions of the reflective plates 82 and 84 and the magnitudes of the output voltages of the photosensor 80. The reflective plate 82 is positioned at a distance d₁ of four millimeters from the face of the photosensor 80 and the reflective plate 84 is positioned at a distance d₂ of two millimeters from the face of the photosensor 80. Since the photosensor 80 is mounted on the carriage 52 and moves therewith across the printer 10, the photosensor 80 scans the reflecting surface 86 (Fig. 4) of the plate 82 and scans the reflecting surface 88 (Fig. 4) of the plate 84. As seen in Fig. 6A, the first light reflective plate 82 includes an edge 81 with the home position of the carriage 52 being represented in the area to the left of the edge 81 or location L₁. The second light reflective plate 84 includes one edge 83 thereof representing the location of a partial cut position or location L₂ and another edge 85 thereof representing the location of a full cut position or location L₃ of the carriage 52 and the cutting blade 74. The cutting operation for partial cut of the receipt paper 24 takes place from edge 81 of reflective plate 82 to edge 83 of reflective plate 84. The cutting operation for full cut of the receipt paper 24 takes place from edge 81 of reflective plate 82 to edge 85 of reflective plate 84. The edges 81, 83 and 85 provide photosensor read locations for output voltages. Figs. 7A and 7B show the relationship between the photosensor 80 and the magnitude of the output voltages in the two positions of the photosensor 80. In the arrangement of the reflective plates 82 and 84, as shown in Figs. 4 and 6A, the voltage signal detected by the photosensor 80 is proportional to the amount of light received by the light receiving element of the photosensor 80 after reflection of the light emitted by the light emitting element of the photosensor 80 off the surface of the respective reflective plate 82 or 84. The photosensor 80 detects the reflective output voltage V₁ in the home position of the carriage 52 and the reflective output voltage V₂ in the cutting position, as shown in Fig. 7B, wherein output voltage V₁ is indicated as being less than output voltage V₂. Fig. 7A illustrates a variable distance d between a photosensor 80 and a reflecting plate (82 or 84) and Fig. 7B shows a variation in the relative output voltage (V₂ greater than V₁) in accordance with the change in the distance d at the respective locations when the photosensor 80 is moved horizontally across the printer 10. The higher output voltage V₂ is generated by the greater amount of light reflected through the lesser distance d2 from the reflective plate 84 (Fig. 6A). Referring back to Figs. 6A, 6B, and 6C, a threshold voltage, designated as V TH1 (Fig. 6B), is always lower than output voltage V₁ and is higher than a voltage V₀, the latter being the case wherein no reflection plate is in the path of the light emitted from the photosensor 80. A threshold voltage, designated as V TH2 (Fig. 6B), is always higher than output voltage V₁ and is lower than output voltage V₂. Accordingly, when the output voltage V OUT of the photosensor 80 is lower than threshold voltage V TH1 , the cutting blade 74 is in an intermediate position between the home position or location L₁ and the cutting position or location L₂ or L₃. It is further noted that when the output voltage V OUT is at a value between threshold voltage V TH1 and threshold voltage V TH2 , the cutting blade 74 is in the home position, and when the output voltage V OUT is higher than threshold V TH2 , the cutting blade 74 is in the cutting position. In an alternative arrangement, a similar effect and result can be obtained when the light reflective characteristics of the reflective plates 82 and 84 are different from each other rather than having the distances d₁ and d₂ different. Fig. 6B shows such relationship between the output voltage V OUT of the photosensor 80 and the threshold voltages V TH1 and V TH2 . Fig. 6C shows the relationship between the photosensor 80 and the position of the cutting blade 74 wherein a high digital output V H is generated when the blade 74 is in the position of either one of the reflective plates 82 or 84. It is seen from Fig. 6A that the photosensor 80 receives a reflected signal from the face 86 of the reflective plate 82, and that the photosensor 80 does not receive a reflected signal, indicated at V L , from the time of passing edge 81 of the plate 82 until the photosensor 80 sees the edge 83 of the reflective plate 84. The photosensor 80 receives a reflected signal from the face 88 of the reflective plate 84 at the time of passing edge 83 thereof indicating a partial cut position of the cutting blade 74 on the carriage 52 and at the time of passing edge 85 of the reflective plate 84 indicating a full cut position. The processing of the output voltage of the photosensor 80 as detected by signals from the reflective plates 82 and 84 in the control system of the present invention is illustrated in the flow charts of Figs. 8, 9A, 9B and 10. Fig. 8 shows the initial processing steps, as started at block 90, when the printer 10 is turned on for printing operation. When the digital output of the photosensor 80 is "0" or low level, the cutting blade 74 is not in the home position, so the process makes a decision as to the logic level and goes through the steps of block 92 and of block 94 to move the cutting blade to the home position. When the digital output of the sensor 80 is "1" or high level, the process makes a decision and goes through step 92 and the motion of the cutting blade 74 is stopped (block 96). The level of the output voltage V OUT (Fig. 6B) of the photosensor 80 (hereafter sensor analog output) is determined and the process makes a decision regarding such sensor analog output (block 98). If the sensor analog output (V OUT ) is of the value of V₁ in the home position, the cutting blade 74 is not moved as the blade 74 is indicated as already being in the home position (block 100). If the sensor analog output (V OUT ) is of the value of V₂ in the cutting position, the cutting blade 74 is moved to the home position (block 94). Figs. 9A and 9B show the steps of a full cut processing, as started at block 102, and wherein the cutting blade 74 is moved from home position L₁ to the read end position, as indicated at location L₃ in Fig. 6A. The operation is that of moving the cutting blade 74 from the home position to the cutting position (block 104) to fully cut the receipt paper 24 (Fig. 5). During the time that the cutting blade 74 is being moved to the full cut position, the receipt paper 24 is being cut and during such time the sensor digital output changes in the order of "1" to "0" to "1". When the sensor digital output changes for the first time from "0" to "1" (block 106), the process is checked to see whether or not the sensor analog output is V₂ (block 108). If the sensor analog output is not V₂, the operation is in error and the movement of the cutting blade 74 is stopped to correct the error in operation (blocks 110 and 112). If the sensor analog output is V₂, the process continues to block 114. When the sensor digital output changes from "1" to "0" (block 114), the cutting blade 74 is stopped (block 116) indicating that the receipt paper 24 is fully cut. The cutting blade 74 is then returned to the home position (block 118). After the cutting blade 74 has returned to the home position (block 118), the changing of the sensor digital output from "0" to "1" (block 120) indicates that the cutting blade 74 is in the L₃ location or full cut position (Fig. 6A). The process of cutting blade 74 movement is then checked to see whether or not the sensor analog output is V₂ (block 122). If the sensor analog output is not V₂, the operation is in error and is stopped to correct the error (block 130). If the sensor analog output is V₂, the process continues to block 124. When the sensor digital output changes from "1" to "0", the cutting blade 74 is in the L₂ location or partial cut position (Fig. 6A). When the sensor digital output changes from "0" to "1", the cutting blade 74 is at the home position (block 124), and operation of the blade 74 is stopped (block 126). If the sensor digital output does not change from "0" to "1", the process continues in a loop until such change occurs. The process is then checked to confirm that the sensor analog output is V₁ (block 128) which is the indication of completion of the paper cutting operation. In the course of going through the various steps of the process in the full cut operation, if the sensor analog output is not V₂ (block 122) or if the sensor analog output is not V₁ (block 128), operations are performed to correct the error (blocks 130 and 132). Fig. 10 shows the steps of a partial cut processing, as started at block 134, and wherein the cutting blade 74 is moved from home position L₁ to read end position, indicated at location L₂, for the partial cutting operation. As in the case of the full cut operation, after the completion of the partial cut, the cutting blade 74 is returned to the home position. The movement of the cutting blade 74 is started (block 136) toward the partial cut position. When the sensor digital output changes from "0" to "1" (block 138), the movement of the cutting blade 74 is stopped (block 140) and the process is checked to see whether or not the sensor analog output is V₂ (block 142). If the sensor analog output is V₂, the blade 74 is returned to the home position (block 144). When the sensor digital output changes from "0" to "1" (block 146), operation of the cutting blade 74 is stopped (block 148). The process is then checked to confirm that the sensor analog output is V₁ (block 150) and, if so, the cutting blade 74 is in the home position (block 152). In the course of going through the various steps of the process in the partial cut operation, if the sensor analog output is not V₂ (block 142), or if the sensor analog output is not V₁ (block 150), operations are performed to correct the error (blocks 154 and 156), in similar manner as indicated by blocks 130 and 132 in Fig. 9B for the full cut operation. Fig. 11 shows an arrangement of the control circuit for the drive mechanism for the cutting blade 74. The reflex type photosensor 80 is carried on the carriage 52 for the cutting blade 74. The photosensor 80 generates a sensor analog output V OUT in accordance with a difference in the amount of reflected light from the surface or face 86 of reflective plate 82 or from the surface or face 88 of reflective plate 84. The sensor analog output V OUT is sent to an analog-to-digital converter 160 which determines whether such output is of the magnitude V₁ or V₂. The output V OUT from the photosensor 80 is also sent to a comparator 162. The output of comparator 162 is used as an interruption signal, designated as V HL , to a central processing unit (CPU) 164 which includes the programs of the steps of operation shown in Figs. 8, 9A, 9B and 10. The signal V HL is shown as being and can be either a low output voltage V L or a high output voltage V H , as indicated in Fig. 6C. A motor rotating/reversing circuit 166 is controlled by the central processing unit 164 for operating the motor 54. A light emitting diode current correcting circuit 170 is connected to the CPU 164 and to the photosensor 80 which detects signals from reflecting face 86 or 88. A resistor 172 is connected to the output of the photosensor 80 and to ground. Fig. 12 shows an arrangement of a cutting mechanism in a conventional printer which used some of the same parts as described above. The motor 54 drives a carriage 174 by means of the belt 56 and the lead screw 64. The cutting blade 74 is carried by the carriage 174 and cooperates with the fixed blade 76 for cutting the receipt paper 24 and providing a receipt 33. The carriage 174 has a light shielding plate 176 attached thereto which is operable with a plurality of light transmission type photosensors 178, 180 and 182. The light transmission type photosensors 178, 180 and 182 each include a light emitting element and a light receiving element which is positioned in facing relationship with the light emitting element. The photosensors 178, 180 and 182 are located in the home position and in the paper cutting position, the latter position being disposed at the end of the paper cutting operation. The light shielding plate 176 is provided on the carriage 174 for shielding the light of the respective photosensor 178, 180 or 182. The position of the carriage 174 is sensed in the manner of presence or absence of an output from the respective photosensor 178, 180 or 182 for controlling the movement of the cutting blade 74. The photosensor 178 is located at the home position, the photosensor 180 is located at the partial cut position and the photosensor 182 is located at the full cut position of the cutting mechanism. It is thus seen that at least two photosensors, 178 and 180 or 178 and 182, are required to provide a cutting operation for either a partial cut or a full cut of the receipt paper 33. If both a partial cut and a full cut are desired, the operation requires all three photosensors 178, 180 and 182. In this regard and using the cutting mechanism in a conventional printer, the number of components is increased and the manufacturing and assembling steps are complicated so that a reduction in cost cannot be attained. In the operation of the present invention, it is seen that when the cutting blade 74 is in the home position or location L₁, the photosensor 80 on the carriage 52 receives a lower level or lesser amount of light from the reflective plate 82 by reason of the longer distance d₁ from the photosensor 80 to the face of the reflective plate 82. The control apparatus and circuitry recognizes that the cutting blade 74 is currently in the home position by reason of the lesser light-lower output voltage signal. When the cutting blade 74 is in the cutting position, the photosensor 80 receives a higher level or greater amount of light from the reflective plate 84 due to the shorter distance from the photosensor 80 to the face of the reflective plate 84. The control apparatus and circuitry recognize that the cutting blade 74 is currently in the cutting position by reason of the greater light-higher output voltage signal. The result of this arrangement is that the operation of the cutting blade 74 is controlled by the single photosensor 80. The present invention provides the single light reflecting photosensor 80 secured on the carriage 52 of the cutting blade 74. The light reflecting plates 82 and 84 are located in home and cutting positions and are at different distances from the photosensor 80 to enable sensing of the current position of the cutting blade 74 by a single photosensor for accurately controlling the movement and operation of the cutting blade. As a result of this arrangement, the number of components can be reduced, the assembling operation can be facilitated and the manufacturing cost can be reduced. It is thus seen that herein shown and described is a compact dot matrix printer that includes control apparatus for a receipt cutting mechanism, wherein the cutting blade is caused to be rotated by the external driving force that is used to move the cutting blade carriage across the printer. The control apparatus includes a single photosensor element operating with one reflective plate at one distance therefrom for indicating the home position of the cutting blade and operating with another reflective plate at a different distance from the photosensor for indicating the cutting position of the cutting blade.

Claims: A control system for controlling the movement of a cutting device (74) mounted on a carriage (52) in a printer (10) including drive means (64) for moving said carriage (52) in a reciprocal manner along a rectilinear guide path, characterized by photosensing means (80) secured to said carriage (52) and having a light emitting element and a light receiving element, a first reflecting member (82) fixed relative to said guide path and arranged, when said carriage (52) is at a first position in said guide path, to receive light from said light emitting element and to reflect light back to said light receiving element, the light received by said light receiving element from said first reflecting member (82) being of a first intensity, a second reflecting member (84) fixed relative to said guide path and spaced from said first reflecting member (82), said second reflecting member (84) being arranged, when said carriage (52) is at a second position in said guide path, to receive light from said light emitting element and to reflect light back to said light receiving element, the light received by said light receiving element from said second reflecting member (84) being of a second intensity different from said first intensity, and control means (160,162,164) responsive to the reflected light received by said light receiving element from said first and second reflecting members (82,84) for controlling the movement of said carriage (52) along said guide path. A control system according to claim 1, characterized in that the distance between said first reflecting member (82) and said photosensing means (80) when said carriage (52) is at said first position is different from the distance between said second reflecting member (84) and said photosensing means (80) when said carriage (52) is at said second position. A control system according to claim 1, characterized in that the distance between said first reflecting member (82) and said photosensing means (80) when said carriage (52) is at said first position is equal to the distance between said second reflecting member (84) and said photosensing means (80) when said carriage (52) is at said second position, and said first and said second reflecting members (82,84) differ from each other in light reflection characteristics. A control system according to any one of claims 1 to 3, characterized in that said drive means (64) includes a lead screw (64) coupled to said carriage (52) for moving thereof along said guide path across said printer (10). A control system according to any one of claims 1 to 4, characterized in that said printer (10) includes a fixed blade (75) engageable by said cutting device (74) for cutting record media. A control system according to any one of claims 1 to 5, characterized in that said first reflecting member (82) is a first plate (82) located at a home position of said carriage (52). A control system according to claim 6, characterized in that said second reflecting member (84) is a second plate (84) located at a record media cut position of said carriage (52). A control system according to claim 7, characterized in that said first plate (82) has an edge (81) which when sensed by said photosensing means (80) indicates the home position of said carriage (52) and said second plate (84) has a first edge (83) which when sensed by said photosensing means (80) indicates a record media partial cut position of said cutting device (74) and said carriage (52) and having a second edge (85) which when sensed by said photosensing means (80) indicates the record media full cut position of said cutting device (74) and said carriage (52). A control system according to any one of claims 1 to 8, characterized in that said control means (160,162,164) includes a comparator (162) and an analog-to-digital converter (160) responsive to output voltage signals dependent on the different intensities of reflected light received by said light receiving element, and a central processing unit (164) for receiving output signals from said comparator (162) and from said converter (160) for controlling the operation of said drive means (64) for moving said cutting device (74) across said printer (10). A control system according to claim 9, characterized by a motor control circuit (166) responsive to the output of said central processing unit (164) for controlling the movement of said cutting device (74) across said printer (10).

Inventors: KOBAYASHI TAKEMI, KOBAYASHI, TAKEMI
Applicants: NCR INT INC, NCR INTERNATIONAL INC.
Application year: 1989
Main classification: B41J11
IPC codes: B41J11