REGISTRATION CONTROL

Abstract: A device for synchronizing the timing of a regularly occurring event includes a digital control circuit which generates two error signals. Timing for the device is provided by a rotating cylindrical cam (76) having alternating reflective and non-reflective areas (78) and (80) which are detected by photo-electric sensors (12) and (14). Relays (52) and (54) are provided for adjusting the timing of the event when an error signal (40) or (42) is received from the control circuit (11). In a preferred embodiment, the registration device is applied to properly position a cutter for cutting a web of moving material into predetermined lengths.

Description: REGISTRATION CONTROL DESCRIPTION TECHNICAL FIELD The present invention, a registration control, relates generally to registration and synchronization systems and more specifically to a device for properly positioning a cutter for cutting a moving web of material into pre¬ determined lengths. BACKGROUND ART Moving webs of material such as paper must often be cut into regular lengths to be used in forming paper bags and other articles. The moving web of paper is separated without stopping its movement by a high speed cutting device. Often there is printed information on the surface of the paper, and it is important that the cut be positioned accurately. There are many reasons why a cut may be improperly positioned. These include stretching and slipping of the paper itself. Also, vibrations of the machinery can force the cutter itself out of alignment. Even though the positioning difference between each cut and the next is generally very small, after a period of time of high speed operation the errors become cumulative, often causing the position of the cut to be displaced by a great amount which makes the resulting goods worthless. The present invention is unique among registration controls in the precision of control provided and economy of manufacture. DISCLOSURE OF INVENTION It is therefore an objective of the present invention to provide a device for automatically repositioning a cutter when necessary. It is a further objective that the device can also be used to synchronize any regularly occurring event. It is another objective of the present invention that the device employs solid state components to minimize size and cost and to increase reliability. OMPI It is yet another objective to provide for the use of infrared optics so that operation of the device is unaffected by ambient visible light levels. Therefore, one aspect of the present Invention provides means for generating first and second temporally 5 overlapping synchronization pulses which indicate the proper timing of the recurring event. Another electrical pulse Is generated upon each occurrence of the event. If the event pulse occurs during the overlap time of the synchronization pulses, the event is considered to be 0 synchronized. If a portion- of the event pulse occurs outside of the overlapping area, a signal is generated to adjust the timing of the event. The invention is adapted to position a cutter used to separate a moving web of paper into predetermined lengths. 5 T e event pulse can be the optical registration of a guide mark printed on the surface of the paper. The novel . features which characterize the present invention are defined by the appended claims. The foregoing and other objects and advantages of the invention 0 will hereinafter appear, and for purposes of illustration, but not of limitation, a preferred embodiment is shown in the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS FIGURE 1 is a block diagram of a registration and 5 synchronization device; FIGURE 2 is a perspective and diagramatic view of a preferred means for generating synchronization pulses; FIGURE 3 Is a diagramatic view of a cam surface; and, FIGURE 4 is a diagram of a preferred scanner assembly. 30 BEST MODE FOR CARRYING OUT THE INVENTION The present invention includes a discriminator which is adaptable to a wide variety of applications. In a preferred embodiment, the discriminator is used with automatic machinery for cutting a moving web of material * --5 into a series of identical lengths. One application of the preferred embodiment is the cutting into regular lengths of paper to be used in constructing paper bags. A discriminator has two inputs which generate synchron¬ ization pulses in phase with the operation of a cutter. A scanner input generates pulses which indicate the position of the web of paper. The discriminator has a unique and simplified logic system for generating a first and a second error pulse which indicate that the cutter is positioned ahead of or behind the proper position. The discriminator can reposition the cutter by driving a position control device to insure that the material is cut in the proper place. The term "low level" or "low logic level" as used here¬ in refers to a predetermined voltage, usually zero volts with reference to the ground potential of the system. The term "high level" or "high logic— level" refers - to a positive voltage higher with respect to ground than that of the low level. This preferred embodiment uses a high level of twelve volts. A relatively large high voltage helps to eliminate logic errors due to noise in the system. The high level is used in this description as a logical "1", and the low level as a "0", defining a system using positive logic. It will be appreciated by those skilled in the art that the high and low level voltages can be interchanged, and devices which operate using negative logic substituted. Referring to FIGURE 1, a preferred embodiment of the present invention is a device, designated generally by the reference numeral 10, for positioning a cutter (not shown) used to separate a continuous, moving web of paper or other material into substantially identical lengths. The logic functions of the device are contained in a discriminator 11. The discriminator 11 includes a first synchronizing input device 12 and a second synchronizing input device 14. The outputs of the first and second synchronizing inputs 12, 14 consists of a low logic signal with a high logic level pulse as later described in connection with FIGURE 3. The timing of the first and second synchronizing pulses are such that they overlap for a predetermined period of time as will also be discussed in connection with FIGURE 3. A first synchronizing (or sync) signal 16 from the first synchronizing input 12 is coupled to the input of a first inverter 20. The output of the first inverter 20 is the logical negation of the first sync signal 16. That is, a low- first sync signal 16 gives rise to a high output from the first inverter 20. A second synchronizing signal 18 is likewise coupled to a second inverter 22. The first sync signal 16 and the output from the second inverter 22 are coupled to the inputs of a first logical OR gate 24. The second sync signal 18 and the output from the first inverter 20 are coupled to the input of a second OR gate 26. The output from the first OR gate 24 is coupled to one input of a third OR gate, and the output of the second OR gate 26 is coupled to one input of a fourth OR gate 30. A scanner input device 32 Is coupled to a third inverter 34 in the .discriminator 11. The third inverter output 36 is the logical negation of the voltage from the scanner 32. The third inverter output 36 can be used to drive an event indicator 38, which indicates to an operator that an event has occurred. The event indicator 38 can be, for example, an LED. The event indicator 38 gives an operator a visual check that the scanner 32 is properly registering events as they occur. In this preferred embodiment, the apparatus 10 is used to position a conventional cutting device (not shown) which separates a moving web of paper into substantially identical lengths for use in the construction of paper bags and the like. The events which are sensed are the movement of marks on the paper past a certain point. These marks indicate the desired position of the cuts. The marks may be positioned so that the cuts are always through the markes themselves, or the cuts may always be made a consistent predetermined distance from the marks. The position of the cutter is adjustable in both directions along the line of movement of the paper. A two directional motor (not shown) is used to properly position the cutter. Referring to FIGURE 1, means are shown for driving the positioning motor in the proper direction. The output from 5 the third OR gate 28 defines a retard error signal 40. The output from the fourth OR gate 30 defines an advance error signal 42. The- output of the third OR gate is coupled to a first output timer 44, and the output from the fourth OR gate is coupled to a second output timer 46. A pulse in 0 the retard error signal 40 acts as a trigger for the timer 44, which generates a pulse having a width controlled by the setting of a first width control 48. The second output timer 46 generates an output pulse having a width controlled by a second width control 50 when a trigger 5 pulse is received from the advance error signal 42. Solid state relays 52, 54 operate the positioning motor when a pulse is received from the first or second output timer 44, 46. The duration of the pulses of the timers 44 and 46, as controlled by the controls 48, and 50, determine the length -0 of time the positioning motor will operate, which in turn determines how far the cutting mechanism will be moved when an error signal is received. A preferred embodiment for the scanner 32 is shown in FIGURE 4. A moving web of paper 56 has positioning marks 3 58 spaced to indicate the proper cutting locations. The paper 56 may be cut at the location of the positioning mark 58, or at a predetermined distance therefrom. A reading head 60 supports first and second optical fibers 62, 64. The use of optical fibers 62, 64 allows the electronic 0 circuitry of the scanner 32 to be operated in a convenient location, and the reading head 60 to be located at a removed location. The reading head 60 supports the optical fibers 62, 64 so that light is emitted from the first fiber 62 and reflected into the second fiber 64 when a 5 positioning mark 58 is directly adjacent to the head 60. (No light from the fiber 62 is reflected into the second fiber 64 when there is not a positioning mark 58 underneath the head 60. ) The light transmitted to the reading head 60 by the first optical fiber 62 is supplied by an LED 66. The LED 66 preferrably produces light in the infrared region. Sensing of infrared light allows the ambient visible light intensity to fluctuate without affecting the operation of the scanner 32. The intensity of the infrared light emitted by the LED 66 is controlled by adjustable resistor 68. It may be necessary to match the frequency of the radiation from the LED 66 with the properties of the paper 56 so that the radiation is not reflected into the second fiber 64 when no positioning mark 58 is present. The positioning marks 58 are printed with a material which is a good reflector of infrared radiation. The reflected infrared light is picked up In the second fiber 64 and transmitted to an optical sensor 70. The optical sensor 70 is of a type which will be triggered by electro¬ magnetic radiation of the same wavelength as that emitted by the LED 66. The scanner signal voltage 33 is low when no light of the proper wavelength is being transmitted to the sensor 70. When a positioning mark 58 passes underneath the reading head 60, the light carried to the sensor 70 by the second fiber 64 causes the transistors located therein to be turned on. This causes a positive pulse to be generated in the scanner signal 33. Infrared radiation has been used in the preferred scanner, but other frequencies can work equally well. It is only important that care be taken that the optical sensor 70 is triggered only when a positioning mark 58 passes underneath the reading head 60. A preferred apparatus for generating the first and second synchronization signals 16, 18 is shown in FIGURE 2. The first and second synchronization Inputs 12, 14 are each comprised of a photo-transistor. A light source (not shown) is located near the photo-transistors 12, 14. The light emitted by the source is also preferrably infrared, so that it is not necessary to optically isolate the apparatus of FIGURE 2 to ensure accurate operation. When light of the proper wavelength impinges on the base of 5 either photo-transistor 12, 14, current flows through that transistor and generates a positive synchronization signal 16, 18, across input resistors 72, 74. A cylindrical cam 76 has a surface comprising alternating reflective areas 78 and non-reflective areas 10 80. The cam 76 rotates so that reflective and non-- reflective areas 78 and 80 alternately appear beneath the photo-transistors 12 and 14. The relationship between the reflective and non-reflective areas 78, 80 will be discussed, in connection with FIGURE 3. 15 The rotation of the cam 76 is linked to the movements of the cutter. In the preferred embodiment, the cutting mechanism includes a shaft which rotates an integral number of times for each cutting cycle. The cam 76 is coupled to this shaft through appropiate gearing so as to rotate in phase with the cutting cycle. In the preferred embodiment, the cam 76 rotates once for each cycle of the cutter. The cam 76 can also be moved along its axis, and fixed in the desired position. This changes the relative timing of the reflecting areas 78 as seen by the photo-transistors 5 12 and 14. A two dimensional view of the cam 76 as seen by the first and second synchronizing inputs 12, 14 is shown in FIGURE 3. In this embodiment, the greater part of the cam 76 is non-reflective area 80, with two reflective areas 78. The inputs 12, 14 scan only a small area, and the motion of the cam 76 causes the first photo-transistor 12 to trace out a first scan line 82 and the second photo-transistor 14 to trace out a second scan line 84 with respecc to the surface of the cam 76. Movement of the cam 76 with respect ' •3 to the sync inputs 12, 14 causes them to trace out scan lines 82, 84 which track over different portions of the cam 76. Close inspection of FIGURES 2 and 3 will reveal that the geometry of the cam surface 76 shown in FIGURE 2 is slightly different from that shown in FIGURE 3. However, FIGURE 3 represents the cam surface 76 as seen by the inputs 12, 14 with respect to time, due to the rotation of the cam 76. When the cam surface 76 of FIGURE 3 is viewed as a model of what is sensed by the photo-transistors 12, 14, it will be seen that the actual surface as shown in FIGURE 2 and the model surface as shown in FIGURE 3 are identical. Different arrangements of the reflective and non- reflective areas 78, 80 will generate different relation- ships between the sync signals 16 and 18. The explanation which follows will allow those skilled in the art to devise different patterns if necessary to create different timing relationships. When a non-reflective surface 80 is immediately adjacent to a sync input 12 or 14, the sync signals 16 or 18 remain in a logical off, or low voltage, state. When a reflecting area 78 passes underneath a photo-transistor 12 or 14, a positive pulse is generated in the sync signal 16 or 18. Referring to FIGURE 3, the reflecting area 78 passes underneath the second sync input 14 between times Tl and T3. The reflective area 78 passes underneath the first input 12 between times T2 and T4. An overlap zone 90 occurs while both signals 16 and 18 are high, between T2 and T3. The width of the overlap zone 90 can be adjusted by repositioning the cam 76 in relation to the sync inputs 12, 14. In FIGURE 3, if the cam 76 is moved down in relation to the scan lines 82 and 84 the second sync pulse 88 is advanced in time while the first sync pulse 86 is delayed in time. This decreases the width of the overlap zone 90. Moving the cam 76 up with respect to the scan lines 82, 84 broadens the overlap zone 90 by advancing the first sync pulse 86 and retarding the second sync pulse 88. The overlap zone 90 defines the area in which the timing of the event, in this case the passage of the positioning mark 58, is synchronized. If a scanner pulse 92 occurs in the scanner signal 33 during the overlap zone 90, no synchroni¬ zation correction is needed. However, when the scanner pulse 92 occurs partially or totally outside the overlap zone 90 the event is out of sync and must be corrected. An example of a scanner pulse 92 indicating that the event is out of synchronization is shown in FIGURE 3. The scanner pulse 92 begins at time T5, and the difference between the leading edge of the scanner pulse 92 and the beginning of the overlap zone 90 can be called a synchronization error time 94. Adjusting the width of the overlap zone 90 changes the positioning error that can be tolerated. If highly accurate cut placement is desired, the overlap zone 90 should be narrowed. It is important to note that the scanner pulse.-92 must be narrower than the overlap zone 90. If the overlap zone 90 is too narrow, the scanner pulse 92 may extend on both sides of the overlap 90, and the control system will operate as if the event must be both advanced and retarded. The discriminator 11 will work properly when the scanner pulse 92 is narrower than that shown in FIGURE 3. It is not necessary that the scanner pulse 92 be wide enough to extend into the overlap zone 90 when it begins at time T5. Operation of the positioning device 10 will now be explained primarily with relation to FIGURES 1 and 3. In this example, the scanner pulse 92 arrives too early in time, indicating that the paper to be cut is moving beyond the proper point before the cut takes place. That is, the proper cutting point is moving downstream beyond the cutter before the cutter goes into operation. To correct this, the cutter must be moved downstream with respect to the moving paper. Before any pulses are received by the discriminator 11, all inputs are in a logical low state. Therefore, logical OR gates 24 and 26 each have one low and one high input. Therefore, the outputs from the OR gates 24 and 26 are high. The third inverter output 36 is high, so that both inputs to both OR gates 28 and 30 are high. Therefore, the retard error signal 40 ' and the advance error signal 42 are both high. When the second sync pulse 88 begins at time Tl, the second sync signal 18 goes high causing the output of the second inverter 22 to go low. This gives two low inputs to the first OR gate 24 causing its output to go low. However, the retard error signal 40 remains high because the third inverter output 36 is still high. When the scanner pulse 92 begins at time T5, the scanner signal 33 goes high causing the third inverter out¬ put 36 to go low. At this time, the retard error signal 40 goes low triggering the first output timer 44. At time T2 the first synchronization signal 16 goes high. At this time, both synchronization signals 16 and 18 are high, which causes the output of both OR gates 24 and 26 to go high. Therefore, the advance error signal 42 remains high and the retard error signal 40 returns to the high state. When the scanner signal 33 returns to the low state, the third inverter output 36 goes high again, forcing the error signals 40 and 42 to remain high no matter what the state of synchronization signals 16 and 18. The first output timer 44 has been triggered by the low pulse of the retard error signal 40. This triggers the solid state relay 52 as earlier described and drives the positioning motor for a period of time determined by the first control 48. The solid state relay 52 is coupled to the positioning motor to move it downstream with respect to the moving sheet of paper 56. The discriminator circuit 11 is symecrical, so that a delayed scanner pulse 92 which occurs so that a portion of OMPI ~ the pulse 92 occurs after the overlap zone 90 will cause the solid state relay 54 to be operated in a manner similar to that just described. The relay 54 is coupled to the positioning motor to advance the motor. 5 If the scanner pulse 92 is completed before time Tl or begins after time T4, no error signal will be generated. If the scanner pulse 92 is likely to move more than a small distance in' time between events, the width of the sync pulses 86, 88 may be increased by enlarging the reflective 10 area 78 of the cam 76. The feature of non-response by the discriminator 11 outside of the action zone occurring between time Tl and T4 may be used to good advantage. The cam 76 can be geared to rotate once for each 2 or 3 cycles of the cutter. When operating the cam 76 so that it 15 rotates at 1/2 or 1/3 of the speed of the cutter as described in the above preferred embodiment, position error detection will only occur during every second or third event. This provides for slower movement of mechanical parts and less frequent repositioning by the positioning 20 motor, which can increase the life of various components in the system. The described embodiment of the present invention has described an apparatus having only one moving part. Optical coupling of the control circuitry and the use of 25 solid state devices causes the reliability of this apparatus to be extremely high. The use of infrared optics allow the apparatus to be used under a wide variety of ambient light conditions without the necessity for extensive optical Isolation. 30 Although a preferred embodiment has been described in detail, it should be understood that various substitutions, alterations, and modifications may become apparent to those skilled in the art. These changes may be made without departing from the spirit and scope of the invention as J J defined by the appended claims. OMPI , vri p o

Claims: CLAIMS 12 1. An apparatus for determining if a regularly occurring event is out of synchronization, comprising: means for generating first and second synchronization pulses which overlap in time for a period shorter than the duration of either pulse; means for generating an event pulse for each occurrence of the event; and, logic means coupled to said synchronization generating means and said event generating means for indicating when the event is out of synchronization. 2. The apparatus of Claim 1 for synchronizing a regularly occurring event, further comprising means for adjusting the timing of the event. 3. An apparatus for positioning a cutter to correctly locate the cut in a moving web of material, comprising: a rotating cylindrical cam having alternating reflecting and non-reflecting regions; first and second optical synchronization inputs which generate pulses when reflecting regions on said cam are detected, wherein said synchronization inputs are positioned so that the first synchronization pulse and the second synchronization pulse overlap; a scanner which generates a pulse when a positioning mark is detected on the moving web of material; logic means coupled to said scanner and to said selector inputs for generating at least one error pulse if the cutter is Improperly positioned; positioning means coupled to the output of said logic means for repositioning the cutter when an error pulse is received. 4. The apparatus of Claim 3 further including means coupled to said positioning means for controlling the distance which the cutter is repositioned when an error pulse is received by said positioning means. 5. The apparatus of Claim 3 wherein said logic means comprises: OMPI a first logical inverter coupled to the output of said first synchronization input; a second logical inverter coupled to the output of said second synchronization input; 5 a third logical inverter coupled to said scanner for inverting the scanner pulses; a first logical OR gate coupled to the outputs of said first synchronization input and said second logical inverter; 0 second logical OR gate coupled to the outputs of said second synchronization input and said first logical inverter; a third logical OR gate coupled to the outputs of said first OR gate and said third inverter, wherein the output 5 defines a first error pulse; and, a fourth logical OR gate coupled to the outputs of said second OR gate and said third inverter, wherein the output defines a second error pulse. 6. The apparatus of Claim 3 wherein said scanner comprises: a light source; a first optical fiber optically coupled to said source so that light is picked up in a proximate end and transmitted through said first fiber to a remote end; - 5 a second optical fiber; a remote head for supporting said first and second fibers so that light emitted from the remote end of said first fiber will be reflected into a remote end of said second fiber when a positioning mark passes adjacent to said head; and, a sensor optically coupled to a proximate end of said second fiber, wherein said sensor generates a pulse when light is transferred from the proximate end of said second fiber. 7. The apparatus of Claim 6 wherein said light source emits infrared light. "BUREA OMPI 8. An apparatus for positioning a cutter to properly locate a cut in a moving web of paper, comprising: a plurality of reflective marks positioned on the paper to indicate the proper cutting location; 5 an infrared light source removed from the cutter; first and second optical fibers, wherein the first fiber is optically coupled to said infrared source, said fibers each having a remote end located near the paper so that the presence of a reflective mark causes infrared 10 radiation to be reflected from the first fiber remote end into the second fiber remote end; a ' scanner sensor optically coupled to a proximate end of said second fiber, wherein said scanner sensor generates a pulse when infrared light is transmitted through said l- 3 second fiber; a rotating cam having alternating reflective and non- reflective regions; first and second optical synchronization sensors positioned adjacent to said cam, wherein said _ synchroni- 20 zation sensors emit pulses when a reflective region is beneath them; logic means coupled to said first and second synchron¬ ization sensors and to said scanner sensor for generating a first error signal If the cutter is operating too early, 25 and for generating a second error signal of the cutter is operating too late; and, means for repositioning the cutter when an error signal is generated, so that the cutter operates at the correct time. 30 9. A method for determining when a regularly occurring event is out of synchronization, comprising the steps of: generating first and second synchronizing pulses which have a temporal overlap less than the width of either pulse; 35 generating an event pulse each time an event occurs; and, OMPI vri p o generating an error signal if at least a portion of the event pulse occurs outside the temporal overlap of the synchronizing pulses. 10. The method of Claim 9 for synchronizing a regularly occurring event, further comprising the step of adjusting the timing of the event so that the event pulse occurs during the temporal overlap of the synchronizing pulses . 11. The method of Claim 9 further comprising the step of adjusting the timing of the event by a predetermined amount each time. an error signal' is generated.

Inventors: FOOTE DONALD R
Applicants: FOOTE DONALD R
Application year: 1981
Main classification: B26D5
IPC codes: B26D5, B65H23