Automatically guiding workpieces through a machine

Abstract

Automatic guiding apparatus has first and second drive wheels which are driven from a common source for effecting feeding of a workpiece in a straight line through a machine. For effecting steering of the workpiece along a line parallel to the edge, a sensor senses the edge, a computer calculates the speed differential required to be imparted to the two drive wheels for steering about the center of curvature of the edge, and an adding device superimposes additional positive or negative speed on one of the drive wheels. The adding device can be mechanical, such as a differential gearbox, where the wheels are driven from a common motor, or a frequency shifter where the wheels are driven by separate stepper motors supplied with pulses from a common oscillator. Automatic speed control is incorporated for negotiating sharp corners. The drive wheels are parallel to each other. In an alternative embodiment, a pair of drive wheels feed the material through the machine with one edge in engagement with a stop and an auxiliary wheel, controlled by a servo and edge sensor, is driven in opposite directions transverse to the direction of feed for effecting steering.

What we claim.]. .Iadd.What is claimed .Iaddend.is: .[.1. Apparatus for guiding a workpiece through a machine to present to a work station successive portions of the workpiece located along a curved path, comprising drive means for imparting motion to the workpiece to advance said portions of said workpiece through said work station in a substantially constant direction, means for providing a signal dependent upon the radius of curvature of said curved path to be followed by the workpiece, and control means responsive to said signal for controlling said drive means to cause the workpiece to rotate the workpiece so as to steer the workpiece substantially about the center of curvature of said 
     
        curved path..]. .[.2.  Apparatus according to claim 1, wherein said drive means comprises first and second drive members adapted to engage the workpiece at spaced positions, and said control means is operative to cause said first and second drive members to be driven at speeds appropriate for effecting said steering about substantially said centre of curvature..]. .[.3. Apparatus according to claim 1, wherein said signal providing means comprises a sensor operable to sense a predetermined line on the workpiece and to generate said signal such as to cause said control means to drive said drive means such that said predetermined line is followed..]. .[.4. Apparatus according to claim 1, wherein said drive means comprises at least one drive member disposed immediately adjacent said work station and arranged to frictionally engage said workpiece to impart motion thereto..]. .[.5. Apparatus for guiding a workpiece through a machine, comprising drive means for imparting motion to the workpiece, means for providing a signal dependent upon the radius of curvature of a curved path to be followed by the workpiece, control means responsive to said signal for controlling said drive means to cause the workpiece to be steered substantially about the center of curvature of said curved path, said drive means comprising first and second drive members adapted to engage the workpiece at spaced positions, said control means being operative to cause said first and second drive means to be driven at speeds appropriate for effecting said steering about substantially said center of curvature, said drive members are operative to impart motion to said workpiece in parallel directions..]. .[.6. Apparatus according to claim 5, wherein said drive means comprises common means operable for driving said drive members at speeds for effecting feeding of the workpiece along a substantially straight line and means interposed between said common drive means and at least one of said drive members for superimposing an additional positive or negative speed on said at least one member in response to said signal produced by said control means to effect said steering..]. .[.7. Apparatus according to claim 6, wherein said common means comprises a motor, and said interposed means comprises a 
     
     
        transmission device..]. 8. Apparatus .[.according to claim 7, wherein.]. .Iadd.for guiding a workpiece through a machine, comprising first and second drive members adapted to engage the workpiece at spaced positions for imparting motion to the workpiece in parallel directions; a motor for driving said drive members at speeds for effecting feed of the workpiece along a substantially straight line; means for providing a signal dependent upon the radius of curvature of a curved path to be followed by the workpiece; control means responsive to said signal for controlling said drive members to cause the workpiece to be steered substantially about the center of curvature of said curved path, said control means including means for producing a control signal representative of the speeds at which said drive members are to be driven to effect said steering about substantially said center of curvature; a transmission device interposed between said motor and at least one of said drive members for superimposing an additional positive or negative speed on said at least one drive member in response to said control signal to effect said steering, .Iaddend.said transmission device .[.comprises.]. .Iadd.comprising .Iaddend.a differential gear mechanism having first and second inputs, a first of said inputs being connected to said motor to be driven thereby; and .[.including.]. a servo motor responsive to .[.the.]. .Iadd.said control .Iaddend.signal .[.produced by said control means for rotation.]. .Iadd.adapted to rotate .Iaddend.in opposite directions, said servo motor being connected to the second said input of said differential gear mechanism, said differential gear mechanism having an output 
     
     
        connected to said at least one drive member. 9. Apparatus .[.according to claim 6, including.]. .Iadd.for guiding a workpiece through a machine, comprising first and second drive members adapted to engage the workpiece at spaced positions for imparting motion to the workpiece in parallel directions; common means for driving said drive members at speeds for effecting feed of the workpiece along a substantially straight line; means for providing a signal dependent upon the radius of curvature of a curved path to be followed by the workpiece; control means responsive to said signal for controlling said drive members to cause the workpiece to be steered substantially about the center of curvature of said curved path, said control means including means for producing a control signal representative of the speeds at which said drive members are to be driven to effect said steering about substantially said center of curvature; interposed means interposed between said common means and at least one of said drive members for superimposing an additional positive or negative speed on said at least one drive member in response to said control signal to effect said steering, and .Iaddend.first and second electric motors for driving said respective drive members, .[.and wherein.]. said common means .[.comprises.]. .Iadd.comprising .Iaddend.a power supply circuit for 
     
     
        supplying electric power to said motors. 10. Apparatus according to claim 9, wherein said interposed means is between said power supply circuit and .[.a.]. .Iadd.one of .Iaddend.said .[.motor.]. .Iadd.motors. .Iaddend. 
     
     
            Apparatus according to claim 10, wherein said motors are stepper motors, said power supply circuit comprises an oscillator for producing pulses for supply to said stepper motors, and said interposed means comprises frequency shifting means responsive to .[.the.]. .Iadd.said control .Iaddend.signal .[.produced by said control means.].. .[.12. Apparatus according to claim 6, wherein said common means is operable at a variable speed for varying the speed at which the workpiece is fed through 
     
     
        the machine..]. 13. Apparatus .[.according to claim 12, including.]. .Iadd.for guiding a workpiece through a machine, comprising first and second drive members adapted to engage the workpiece at spaced positions for imparting motion to the workpiece in parallel directions; common means for driving said drive members at speeds for effecting feed of the workpiece along a substantially straight line, said common means being operable at a variable speed for varying the speed at which the workpiece is fed through the machine; signal generating means for providing a signal dependent upon the radius of curvature of a curved path to be followed by the workpiece; control means responsive to said signal for controlling said drive members to cause the workpiece to be steered substantially about the center of curvature of said curved path, said control means including means for producing a control signal representative of the speeds at which said drive members are to be driven to effect said steering about substantially said center of curvature; interposed means interposed between said common means and at least one of said drive members for superimposing an additional positive or negative speed on said at least one drive member in response to said control signal to effect said steering, and .Iaddend.means for automatically varying the speed of said common means in dependence upon the magnitude of the signal provided 
     
     
        by said signal generating means. 14. Apparatus according to claim 13, including a variable speed operating mechanism of said machine, said common means also providing drive to said operating mechanism. .[.15. Apparatus according to claim 6, wherein said common means is operable to drive said members intermittently and simultaneously..]. .[.16. Apparatus according to claim 15, wherein said control means receives a signal from said common means such that, in the periods between which intermittent drive is applied to said drive members, the speed to be superimposed on said at least one drive member is zero..]. .[.17. Apparatus according to claim 5, wherein said signal providing means comprises a sensor operable to sense a predetermined line on the workpiece and to generate said signal such as to cause said control means to drive said drive members such that 
     
     
        said predetermined line is followed..]. 18. Apparatus .[.according to claim 5, wherein.]. .Iadd.for guiding a workpiece through a machine, comprising first and second drive members adapted to engage the workpiece at spaced positions for imparting motion to the workpiece; signal providing means for providing a signal dependent upon the radius of curvature of a curved path to be followed by the workpiece; control means responsive to said signal for controlling the speeds at which said first and second driven members are driven to cause the workpiece to be steered substantially about the center of curvature of said curved path, .Iaddend.said control means .[.includes.]. .Iadd.including .Iaddend.computing means, means to supply said signal to said computing means, and means to supply to said computing means a further signal representative of the speed of feeding the workpiece through the machine, said computing means being operable to effect a computation on said signals and to produce an output signal which is representative of the required angular velocity to be imparted to the workpiece to effect said steering correctly, and means for supplying said output signal to said 
     
     
        drive  .[.means.]. .Iadd.members. .Iaddend. 19. Apparatus according to claim 18, wherein said drive members are operable to impart motion to said workpiece in parallel directions, and wherein said output signal thereby represents the required speed difference to be imparted to said drive 
     
     
        members. 20. Apparatus according to claim 19, wherein said drive members are disposed on a common line upon which the centres of curvature about 
     
     
        which the workpiece can be steered are also located. 21. Apparatus according to claim 20, wherein said signal providing means comprises a sensor to sense a physical line on said workpiece, said sensor being located in advance of said common line and being adapted to produce a signal representative of the magnitude and direction of deviation of said physical line from a straight line normal to said common line and intersecting the point of intersection of said common line and said physical line, and said computing means being operative to compute the equation: ##EQU7## where: d is the distance (measured along said common line) between the drive members,   q is the deviation sensed by the sensor,   v 2  is the speed at which .[.one of.]. said drive .[.members.]. .Iadd.member nearer to said intersection of said common line and said physical line .Iaddend.is driven and represents said speed of feeding .[.of feeding.]. of the workpiece,   v 1  is the speed at which the other said drive member is to be driven to effect said steering,   .[.p.]. .Iadd.a .Iaddend.is the spacing between the intersection of said common line and said physical .Iadd.line .Iaddend.and the drive member nearer thereto,   .[.a.]. .Iadd.p .Iaddend.is the distance from said sensor to said common   
     
     
        line. 22. Apparatus according to claim 21, wherein said control means is 
     
     
        operable to compute an approximation of said equation. 23. Apparatus according to claim 22, wherein said approximation comprises ignoring 
     
     
        q 2 . 24. Apparatus according to claim 20, wherein said machine 
     
     
        includes a work station disposed on said common line. .[.25.  Apparatus for guiding a workpiece through a machine to present to a work station successive portions of said workpiece located along a curved path, comprising drive means operable for advancing said workpiece intermittently through the machine such that said successive portions of said workpiece move through said work station in a substantially constant direction, and control means for rotating said workpiece simultaneously with said intermittent advances thereof to effect steering of the workpiece along said path during said intermittent advances of said portions of said workpiece in said substantially constant direction..]. .[.26. Apparatus according to claim 25, wherein said signal providing means comprises a sensor operable to sense a predetermined line on the workpiece and to generate said signal such as to cause said control means to drive said drive means such that said predetermined line is followed..]. .[.27. Apparatus according to claim 25, wherein said drive means comprises at least one drive member disposed immediately adjacent said work station and arranged to frictionally engage said workpiece to impart motion thereto..]. .[.28. Apparatus for guiding a workpiece through a machine to present to a work station successive portions of said workpiece located along a curved path, comprising a plurality of drive members engageable with the workpiece at spaced apart positions for imparting motion thereto, common means for driving said drive members at speeds for effecting feeding of the workpiece substantially in a straight line of constant direction, and means for superimposing additional speed on at least one of said drive members to cause the workpiece to rotate for effecting steering of the workpiece..]. .[.29. Apparatus according to claim 28, wherein said signal providing means comprises a sensor operable to sense a predetermined line on the workpiece and to generate said signal such as to cause said control means to drive said drive means such that said predetermined line is followed..]. .[.30. Apparatus according to claim 28, wherein said drive members are disposed closely adjacent said work station..]..Iadd. 31. Apparatus for feeding a workpiece through a machine to present to a work station successive portions of the workpiece located along a curved path, comprising: engaging means adapted to engage said workpiece;   drive means connected to said engaging means to cause said engaging means to feed portions of the workpiece engaged by the engaging means past said engaging means to advance said successive portions of said workpiece through the work station in a substantially constant direction;   computer means for receiving a signal which changes in accordance with changes in the radius of curvature of successive portions of said path and operable to derive therefrom a control signal representative of the velocity to be imparted to said engaged portions of said workpiece by said engaging means for effecting said presentation of said successive portions of said workpiece to said work station by rotating said workpiece substantially about the center of curvature of each said successive portion of said path; and   control means responsive to said control signal for controlling said drive means in accordance with said control signal..Iaddend..Iadd. 32. Apparatus according to claim 31, wherein said engaging means comprises first and second drive members adapted to engage the workpiece at spaced positions..Iaddend..Iadd. 33. Apparatus according to claim 32, wherein said drive means comprises common means operable for driving said drive members at speeds for feeding the engaged portions of the workpiece at pre-determined relative velocities and said control means includes interposed means interposed between said common means and at least one of said drive members for superimposing an additional velocity on said at least one drive member in response to said control signal. .Iaddend..Iadd. 34. Apparatus according to claim 33, wherein said common means comprises a motor, and said interposed means comprises a transmission device. .Iaddend..Iadd. 35. Apparatus according to claim 34, wherein said transmission device comprises a differential gear mechanism having first and second inputs, said first input being connected to said motor to be driven thereby; and wherein said control means further includes a servo motor responsive to said control signal for rotation in either direction, said servo motor being connected to said second input of said differential gear mechanism, said differential gear mechanism having an output connected to said at least one drive member. .Iaddend. .Iadd. 36. Apparatus according to claim 33, wherein said drive means includes first and second electric motors for driving said respective drive members, and wherein said common means comprises a power supply circuit from which electric power for each of said motors is derived. .Iaddend..Iadd. 37. Apparatus according to claim 36, wherein said interposed means is interposed between said power supply circuit and one of said motors. .Iaddend..Iadd. 38. Apparatus according to claim 37, wherein said motors are stepper motors, said power supply circuit comprises an oscillator for producing pulses for supply to said stepper motors, and said interposed means comprises frequency shifting means responsive to said control signal. .Iaddend..Iadd. 39. Apparatus according to claim 33 wherein said common means includes means for varying the speed at which the workpiece is fed through the machine. .Iaddend..Iadd. 40. Apparatus according to claim 39, wherein said means for varying said speed is operable automatically in dependence upon said changes in said signal received by said computer means. .Iaddend..Iadd. 41. Apparatus according to claim 40, including a variable speed operating mechanism for said machine, said common means also providing variable speed drive to said operating mechanism. .Iaddend..Iadd. 42. Apparatus according to claim 33 wherein said common means is operable to provide continuous drive to each of said drive members. .Iaddend..Iadd. 43. Apparatus according to claim 33 wherein said common means is operable to cause said members to be driven intermittently and simultaneously. .Iaddend..Iadd. 44. Apparatus according to claim 43 wherein said control means receives a signal from said common means such that, in the periods between which intermittent drive is applied to said drive members, the velocity to be superimposed on said at least one drive member is zero. .Iaddend. .Iadd. 45. Apparatus according to claim 33, wherein said drive members are operative to impart motion to said workpiece in parallel directions and wherein said common means drives said drive members at equal driving velocities. .Iaddend..Iadd. 46. Apparatus according to claim 45, wherein said control signal represents the velocity difference to be imparted to said drive members. .Iaddend..Iadd. 47. Apparatus according to claim 32, wherein said drive members are operative to impart motion to said workpiece in parallel directions. .Iaddend..Iadd. 48. Apparatus according to claim 47, wherein said drive members are disposed on a common line upon which the centers of curvature about which the workpiece can be steered are also located. .Iaddend..Iadd. 49. Apparatus according to claim 48, including a sensor to sense a physical line on said workpiece, said sensor being located in advance of said common line and being adapted to produce a deviation signal representative of the magnitude and direction of deviation of said physical line from a straight line normal to said common line and intersecting the point of intersection of said common line and said physical line, and wherein said computer means is operative to derive said control signal as a function of:   the distance "d" (measured along said common line) between the drive members, the deviation "q" sensed by the sensor, the spacing "a" between the intersection of said common line and said physical line and one of said drive members and the distance "p" from said sensor to said common line. .Iaddend. .Iadd. 50. Apparatus according to claim 49, wherein said computer means is operative to define the relationship between v 1  and v 2  by the expression ##EQU8## where: v 2  is the speed at which said one of said drive members is driven, said one drive member being the drive member nearer to said intersection of said common line and said physical line and represents said speed of feeding of the workpiece, and   v 1  is the speed at which the other of said drive members is to be   
     
     
        driven to effect said steering. .Iaddend..Iadd. 51.  Apparatus according to claim 50, wherein said computer means is operable to compute an approximation of said expression. .Iaddend..Iadd. 52. Apparatus according to claim 51, wherein said approximation comprises ignoring q 2 . .Iaddend..Iadd. 53. Apparatus according to claim 49, wherein said sensor comprises a member displaceable in either direction from a position aligned with said straight line so as to follow said physical line when deviating from said straight line, and means to produce said displacement signal in response to said displacement of said sensor. .Iaddend..Iadd. 54. Apparatus for feeding a workpiece through a machine to present to a work station successive portions of the workpiece located along a curved path, comprising: first and second drive members located at spaced apart positions on a common line substantially transverse to the direction in which said successive portions are to be fed to the work station, said drive members being movable parallel to said direction and being engageable with the workpiece so as to feed the portions of the workpiece engaged by the drive members past the respective drive members when moved to advance said successive portions of said workpiece through the work station in a substantially constant direction;   means for driving said drive members;   a sensor for sensing a physical line on said workpiece representative of said curved path and operable to produce a signal dependent upon deviations of said physical line from a straight line substantially normal to said common line, and intersecting the point of intersection of said common line and said physical line, said sensor being positioned in advance of said common line (considered in said direction); and   means for defining the relationship between the velocities v 1  and v 2  at which said drive members are driven by said drive means, by the following equation: ##EQU9## where: q is the deviation sensed by said sensor,   a is the distance (measured along said common line) from the intersection of said common line and said physical line, and said drive member to be driven at the velocity of v 2 ,   d is the distance (measured along said common line) from said drive member to be driven at the velocity of v 2  to the other of said drive members,   p is the distance from said sensor to said common line. .Iaddend..Iadd.   
     
     
             Apparatus according to claim 54, wherein said drive means comprises first means operative for applying drive to said first and second drive members at said velocity v 2 , and summing means for adding to one of said members a velocity v 1  -v 2 . .Iaddend. .Iadd. 56. Apparatus according to claim 54, wherein the sensor is close to said intersection such that q 2  is negligible, and the relationship between v 1  and v 2  is defined by an approximation of said equation, said approximation comprising ignoring q 2 . .Iaddend..Iadd. 57. Apparatus according to claim 54, wherein said sensor comprises a member displaceable in either direction from a position aligned with said straight line so as to follow said physical line when deviating from said straight line, and means to produce said signal in response to said displacement of said sensor. .Iaddend..Iadd. 58. Apparatus according to claim 57, wherein said sensor is operable to sense an edge of said workpiece. .Iaddend..Iadd. 59. Apparatus according to claim 58, wherein said sensor comprises a probe for sensing said edge. .Iaddend..Iadd. 60. Apparatus for guiding a workpiece through a machine to present to a work station successive portions of the workpiece located along a curved path, comprising: a plurality of drive members engageable with the workpiece at spaced apart positions for feeding the engaged portions of the workpiece past the drive members to advance said successive portions of said workpiece through the work station in a substantially constant direction;   common means for driving said drive members at pre-determined relative velocities for feeding the workpiece through the machine, said common means being adjustable to vary the speed of feeding;   signal producing means for producing a control signal which is a function both of the speed of feeding and of the curvature of the path to be followed; and   means for superimposing on at least one of said drive members a variable additional velocity dependent upon said control signal for effecting   
     
     
        steering of the workpiece. .Iaddend..Iadd. 61.  Apparatus according to claim 60, wherein said common means comprises a motor, and said superimposing means includes a transmission device. .Iaddend..Iadd. 62. Apparatus according to claim 61, wherein said transmission device comprises a differential gear mechanism having first and second inputs, said first input being connected to said motor to be driven thereby; and said superimposing means further includes a servo motor connected to said second input of said differential gear mechanism, said differential gear mechanism having an output connected to said at least one drive member. .Iaddend..Iadd. 63. Apparatus according to claim 60, including first and second electric motors for driving said respective drive members, and wherein said common means comprises a power supply circuit for supplying electric power to said motors. .Iaddend..Iadd. 64. Apparatus according to claim 63, wherein said superimposing means is interposed between said power supply circuit and one of said motors. .Iaddend..Iadd. 65. Apparatus according to claim 64, wherein said motors are stepper motors, said power supply circuit comprises an oscillator for producing pluses for supply to said stepper motors, and said superimposing means comprises frequency shifting means responsive to control signal. .Iaddend..Iadd. 66. Apparatus according to claim 60, wherein said common means is operable to vary the speed at which the workpiece is fed through the machine. .Iaddend. .Iadd. 67. Apparatus according to claim 66, including means for automatically varying the speed of said common means in dependence upon said curvature of said path. .Iaddend..Iadd. 68. Apparatus according to claim 67, including a variable speed operating mechanism of said machine, said common means also providing drive to said operating mechanism. .Iaddend..Iadd. 69. Apparatus according to claim 60, wherein said common means is operable to drive said members intermittently and simultaneously. .Iaddend..Iadd. 70. Apparatus according to claim 69, wherein said superimposing means receives a signal from said common means such that, in the periods between which intermittent drive is applied to said drive members, said additional velocity imposed on said at least one drive member is zero. .Iaddend..Iadd. 71. Apparatus according to claim 60, wherein said drive members are operative to impart motion to said engaged portions of said workpiece in parallel directions. .Iaddend..Iadd. 72. Apparatus according to claim 71, wherein said drive members are disposed on a common line transverse to the direction in which said engaged portions of said workpiece are fed by said drive members. .Iaddend..Iadd. 73. Apparatus according to claim 60, wherein said signal producing means includes a sensor operable to sense a physical line of the workpiece and to generate a sensor signal dependent upon the curvature of said line, and means for controlling said superimposing means in accordance with said sensor signal. .Iaddend..Iadd. 74. Apparatus according to claim 73, wherein said sensor is located in advance (considered in the feeding direction) of said common line and wherein said sensor signal is representative of the deviation of said physical line from a straight line normal to said common line and intersecting the point of intersection of said common line and said physical line. .Iaddend..Iadd. 75. Apparatus according to claim 74, wherein said sensor comprises a member displaceable in either direction from a position in alignment with said straight line so as to follow said physical line when deviating from said straight line, and means to produce said sensor signal in response to said displacement of said sensor. .Iaddend..Iadd. 76. Apparatus according to claim 73, wherein said sensor is operable to sense an edge of said workpiece, said edge constituting said physical line. .Iaddend..Iadd. 77. Apparatus according to claim 75, wherein said displaceable member comprises a probe for sensing the edge of said workpiece, said edge constituting said physical line. .Iaddend. .Iadd. 78. Apparatus for feeding a workpiece through a machine to present to a work station successive portions of the workpiece located along a curved path, comprising: first and second drive members located at spaced apart positions on a common line substantially transverse to the direction in which said successive portions are to be fed to the work station, said drive members being movable parallel to said direction and being engageable with the workpiece so as to feed the portions of the workpiece engaged by the drive members past the respective drive members when moved to advance said successive portions of said workpiece through the work station in a substantially constant direction;   means for driving said drive members;   a sensor for sensing a physical line on said workpiece representative of said curved path and operable to produce a signal dependent upon deviations of said physical line from a straight line substantially normal to said common line and intersecting the point of intersection of said common line and said physical line, said sensor being positioned in advance of said common line (considered in said direction); and   computer means defining the relationship between the velocities at which said drive members are driven by said drive means, as a function of the deviation sensed by said sensor, the distance from said sensor to said common line, the spacing between said drive members and the distance thereof (measured along said common line) from the intersection of said common line and said physical line. .Iaddend.