Centering sensor and controller

• US 3,908,881 A
• Filed: 03/14/1974
• Issued: 09/30/1975
• Est. Priority Date: 03/21/1973
• Status: Expired due to Term

• Current Assignee: Gary D. Mccann
• Original Assignee: Gary D. Mccann
• Inventors: McCann, Gary D.
• Primary Examiner(s): Schacher, Richard A.
• Application Number:
  US05/451,221
• Time in Patent Office: 565 Days
• Field of Search: 242/57.1 226/15,17,18,19,20,21,22,23
• US Class Current: 226/19
• CPC Class Codes: B65H 23/0208 with an element engaging the edge of the web
• CPC Class Codes: B65H 23/0326 by moving the unwinding device
• CPC Class Codes: D05B 29/06 Presser feet
• CPC Class Codes: D05B 35/102 Edge guide control systems with edge sensors
• CPC Class Codes: D05C 15/00 Making pile fabrics or articles having similar surface features by inserting loops into a base material layered products B32B; non-woven pile fabrics D04H11/00
• CPC Class Codes: D05D 2303/30 Fibre mats

Abstract

A system for sensing and controlling the centering of a sheet continuously fed through a machine includes a pair of laterally spaced apart sensing arms spring biased into contact with the opposite edges of the sheet as the sheet is being fed through the machine. Separate transducers responsive to movement of the sensing arms produce electrical signals representing the actual position of each edge of the sheet. The signals from both transducers are compared with input signals representing the known centered position of the sheet to provide an error signal for continuously indicating the magnitude and direction of the deviation from center independently of variations in the width of the sheet or any desired lateral shifting of the sheet as it travels through the machine. A controller responsive to the error signal produces control signals for driving a servo motor which moves the sheet laterally to keep it on center.

Claims

1. In a machine for operating on work having a desired centered position in the machine, the work being fed along a longitudinal path and being in contact with positioning means for adjusting the lateral position of the work relative to the desired centered position, the work being defined by spaced apart first and second longitudinal edges, apparatus for controlling the centering of the work in the machine independently of the width of the work or any lateral movement of the desired centered position of the work as it travels through the machine, the apparatus comprising first and second sensing means to sense the corresponding positions of the first and second longitudinal edges of the work;

means coupled with the first sensing means to produce a first output representing the instantaneous position of the first longitudinal edge;

means coupled with the second sensing means to produce a second output representing the instantaneous position of the second longitudinal edge;

means responsive to the first and second outputs for producing an error signal indicating a deviation of the work from its centered position; and

closed loop feedback means for controlling the centered position of the work, the closed loop feedback means including means responsive to the error signal indicating that the first edge of the work deviates a predetermined distance from the desired centered position for producing a first correction signal, means responsive to the error signal indicating that the second edge of the work deviates a predetermined distance from the desired centered position for producing a second correction signal, and means responsive to either the first or second correction signal for adjusting the work positioning means to automatically move the work back toward its desired centered position, the first or second correction signal being periodically produced by a corrective timer responsive to the presence of an existing error signal to move the work positioning means for a selected time period in a direction which moves the work back toward its centered position.

2. Apparatus according to claim 1 in which the plane where the sensing means are located is spaced longitudinally from the plane where the work positioning means is located, and in which the closed loop feedback means includes means for controlling the lateral adjusting means by periodically sampling the existing error signal and producing a corresponding adjustment of the work positioning means.

3. Apparatus according to claim 2 in which the feedback control means includes means for producing a time delay after each adjustment of the work positioning means.

4. Apparatus according to claim 3 including means for adjusting the length of the time delay.

5. Apparatus according to claim 1 in which the time period of the corrective timer is adjustable.

6. In a machine for operating on work fed through the machine along a longitudinal path, the work having a width defined by a pair of spaced apart first and second longitudinal edges, and in which the machine inCludes lateral shifting means for moving the work laterally back and forth relative to an imaginary longitudinal axis through the machine as the work travels along said longitudinal path, the work having a desired on-center position which moves laterally back and forth relative to said imaginary axis in response to lateral shifting of the work, apparatus for maintaining the work on its desired on-center position as the work shifts laterally and moves longitudinally through the machine, the apparatus comprising means for continuously sensing movement of the actual position of each longitudinal edge of the work relative to said imaginary axis, independently of variations in the width of the work, as the edges are shifted laterally back and forth by the lateral shifting means, means responsive to movement of the lateral shifting means for sensing lateral movement of the desired on-center position of the work relative to said imaginary axis as the work is shifted laterally back and forth, means responsive to the sensed actual position of each longitudinal edge for comparing the actual position of the work with the sensed desired on-center position of the work to produce an error signal representing the lateral deviation of the work from its desired on-center position, and feedback control means responsive to the error signal and operative independently of movement by the lateral shifting means for adjusting the lateral position of the work to move the work toward the desired on-center position.

7. Apparatus according to claim 6 including work positioning means spaced longitudinally from the lateral shifting means and movable independently of the lateral shifting means for adjusting the lateral position of the work relative to said imaginary axis, and means responsive to the error signal for adjusting the lateral position of the work positioning means to automatically move the work back toward its on-center position.

8. Apparatus according to claim 7 in which the plane where the sensing means are located is spaced longitudinally from the plane where the work positioning means is located, and in which the feedback means includes means for controlling the work positioning means to periodically sample the existing error signal and produce a corresponding adjustment of the work positioning means.

9. Apparatus according to claim 8 in which the feedback control means includes means for producing a time delay after each adjustment of the work positioning means.

10. Apparatus according to claim 9 including means for adjusting the length of the time delay.

11. Apparatus according to claim 9 in which the feedback control means includes means responsive to the error signal indicating that one longitudinal edge of the work deviates a predetermined distance from the desired on-center position for producing a first correction signal, means responsive to the error signal indicating that the other longitudinal edge of the work deviates a predetermined distance from the desired on-center position to produce a second correction signal, means responsive to either the first or second correction signal for adjusting the lateral position of the work positioning means, and a corrective timer responsive to the presence of an existing error signal for periodically producing either the first or second correction signal to move the work positioning means for a selected time period in a direction which moves the sheet laterally toward its on-center position.

12. Apparatus according to claim 11 including means for adjusting the time period of the corrective timer.

13. Apparatus for centering a continuous work sheet fed along a longitudinal path through a machine for working on the sheet and in which the sheet is continuously being shifted laterally back and forth as it travels longitudinally through the machine, the sheet having a desired on-center position with respect to the machine and a width defined by laterally spaced apart first and second longituDinal edges, the apparatus comprising first and second sensing arms continuously held in contact with the first and second longitudinal edges, respectively, of the sheet and being movable to follow the actual lateral movement of the first and second edges as the sheet is being shifted laterally back and forth during its travel through the machine, means responsive to movement of the first sensing arm for producing a first input representative of the actual position of the first edge of the sheet, means responsive to movement of the second sensing arm for producing a second input representative of the actual position of the second edge of the sheet, means for sensing the desired on-center position of the sheet as the sheet is being shifted laterally back and forth during its travel through the machine, means responsive to the first and second inputs for comparing the actual position of the work sheet with the sensed desired on-center position of the sheet to produce an error signal representing the lateral deviation of the sheet from its desired on-center position, and feedback control means responsive to the error signal for adjusting the lateral position of the sheet to move the sheet toward the desired on-center position.

14. Apparatus according to claim 13 including laterally movable work positioning means in contact with the sheet for adjusting the lateral position of the sheet to move the sheet toward the desired on-center position, and means responsive to the error signal for adjusting the lateral position of the work positioning means to automatically move the sheet laterally toward its on-center position.

15. Apparatus according to claim 14 in which the plane where the first and second sensing arms are located is spaced longitudinally from the plane where the work positioning means is located, and in which the feedback control means includes means for periodically sampling the existing error signal to produce a corresponding adjustment of the work positioning means.

16. Apparatus according to claim 15 in which the feedback control means includes means for producing a time delay after each adjustment of the work positioning means.

17. Apparatus according to claim 16 in which the feedback control means includes means responsive to the error signal indicating that the first edge of the work deviates a predetermined distance from the desired on-center position for producing a first correction signal, means responsive to the error signal indicating that the second edge of the work deviates a predetermined distance from the desired on-center position to produce a second correction signal, means responsive to the first and second correction signals for producing the error signal for adjusting the lateral position of the work positioning means, and a corrective timer responsive to the presence of an existing error signal for periodically producing either the first or second correction signal to move the work positioning means for a selected time period in a direction which moves the sheet laterally toward its on-center position.

18. Apparatus according to claim 17 in which the length of the time delay period is selectively adjustable independently of the time period of the corrective timer.

19. Apparatus according to claim 13 including first and second electrical elements movable in response to the first and second sensing arms, and third and fourth electrical elements movable in response to lateral shifting of the sheet to indicate the desired on-center position of the sheet, the relative movement of the first and third electrical elements cooperating to produce a first electrical output, the relative movement of the second and fourth electrical elements cooperating to produce a second electrical output, the first and second electrical outputs being compared to produce an electrical output signal representing the lateral deviation of the sheet from its desired on-center position.

20. Apparatus acCording to claim 19 in which the lateral shifting means includes a laterally extending, elongated step-over bar having means on it for engaging the continuous sheet, drive means engaged with the step-over bar for shifting the bar to move the work sheet laterally back and forth as it travels longitudinally through the machine, the third and fourth electrical elements being connected to the step-over bar so the third and fourth electrical elements follow the lateral shifting movement of the bar, the first and second sensing arms being adapted to drive the first and second electrical elements, respectively, so they follow the lateral shifting positions of the longitudinal edges of the sheet.

21. Apparatus for sensing the centered position of a web of varying width traveling along a longitudinal path through a machine for working on the web, the web having a width defined by laterally spaced apart first and second longitudinal edges, the apparatus comprising a. a lateral shifting device engaged with the continuous web for shifting the web laterally back and forth as it travels longitudinally through the machine, b. first and second sensing devices held in continuous contact with the first and second longitudinal edges and being movable to continuously follow lateral movement of the edges of the web as it travels longitudinally through the machine. c. means responsive to movement of the first sensing device for continuously providing a first indication representing lateral movement of the first edge, d. means responsive to movement of the second sensing device for continuously providing a second indication representing lateral movement of the second edge, e. means responsive to movement of the lateral shifting device to sense lateral movement of the desired on-center position of the web, and f. means for comparing the first and second indications with the sensed on-center position of the web to produce an output representing the lateral deviation of the web from its desired on-center position.

22. Apparatus according to claim 21 in which the means for sensing lateral movement of the on-center position of the web comprise means connected to the lateral shifting device for providing third and fourth indications each representing the lateral shifting movement of the desired on-center position of the web;

an electrical bridge circuit in which the first, second, third, and fourth indications comprise respective electrical circuit elements balanced so that the first and second electrical elements provide a first electrical output and the third and fourth electrical elements provide a second electrical output; and

means for comparing the first and second electrical outputs to produce said output representing the lateral deviation of the web from its desired on-center position.

23. Apparatus according to claim 21 including feedback control means responsive to the output representing said lateral deviation of the web for adjusting the lateral position of the web to move the web toward its desired on-center position.

24. Apparatus according to claim 23 including lateral position adjusting means engaged with the web and spaced longitudinally from said lateral shifting device, the position adjusting means being responsive to the output representing said lateral deviation to move the web toward its desired on-center position.