Controlled spacing induction

• US 5,341,916 A
• Filed: 07/22/1993
• Issued: 08/30/1994
• Est. Priority Date: 02/16/1989
• Status: Expired due to Term

• Current Assignee: Dematic Corporation (KION GROUP AG)
• Original Assignee: Rapistan Corp.
• Inventors: Doane, Martin R., Khodor, Ahmad, Kohls, James P.
• Primary Examiner(s): DAYOAN, DARRELL G
• Application Number:
  US08/095,933
• Time in Patent Office: 404 Days
• Field of Search: 198/459-461, 198/572
• US Class Current: 198/460.1
• CPC Class Codes: B65G 2203/042 Sensors
• CPC Class Codes: B65G 2203/044 Optical
• CPC Class Codes: B65G 43/08 Control devices operated by article or material being fed, conveyed or discharged and controlling the discharging devices B65G47/42
• CPC Class Codes: B65G 47/31 by varying the relative speeds of the conveyors forming the series
• CPC Class Codes: B65G 47/681 from distinct, separate conveyor lanes
• CPC Class Codes: B65G 47/70 with precedence controls among incoming article flows

Abstract

A conveyor system including an induction subsystem for producing a desired spacing between packages as they are discharged from a single induction line. The induction line includes a conveyor and a speed controller for controlling the running speed of the conveyor in a manner that discharges a package as close as possible to a time necessary to provide a desired gap with a previously-discharged package. A control monitors movement of packages on the conveyor and includes a device for determining a speed adjustment required for each speed controller to cause the packages on the line to reach the discharge conveyor as close as possible to the desired time. Speed adjustments include a constant acceleration to a higher discrete speed or deceleration to a lower discrete speed from a nominal discrete speed with a return to the nominal speed prior to discharging the package. In one embodiment, the induction line is operated by two servo-controlled motors, with the speed of the downstream motor being controlled in a manner that will provide desired spacing between inducted packages and with the speed of the upstream motor being controlled in o proportion to the speed of the downstream motor. This provides an initial controllable gap between packages to reduce the range of gaps experienced by the induction control.

Claims

1. A method of inducing single-file product in order to provide desired spacing between product comprising:

conveying product through a control zone that is of a length to include more than one product at a time in said control zone;

monitoring movement of a product through said control zone and determining an estimated time of arrival of that product at a discharge portion of said control zone if that product is conveyed at a present speed;

for a product closest to said discharge portion determining a desired time of arrival at said discharge portion in order for that product closest to said discharge portion to be optimally spaced from a downstream product;

effecting a speed change of product in said control zone in order to cause the estimated time of arrival of that product closest to said discharge portion to approach the desired time of arrival of that product; and

adjust the estimated time of arrival of other product in said control zone as a function of speed changes that have occurred while that other product is in said control zone.

2. The method of claim 1 wherein said monitoring product includes detecting leading and trailing edge of product.

3. The method in claim 2 wherein said monitoring product further includes determining a centerline of product in said control zone in the direction of product movement.

4. The method in claim 3 wherein a product is deemed to arrive at said discharge portion when the centerline of that product in the direction of product movement reaches said discharge portion.

5. The method in claim 1 further including monitoring incremental movement of product in said control zone.

6. The method in claim 1 wherein said effecting a speed change includes determining a desired speed change that would cause said estimated time of arrival of that product closest to said discharge portion to be the same as the desired time of arrival of that product closest to said discharge portion and limiting said speed change to that portion of said desired speed change which can be effected including returning the speed to the said present speed before a following product reaches said discharge portion.

7. The method in claim 1 wherein said monitoring includes detecting product i said control zone only when product enters said control zone.

8. A method of inducting single-file product in order to provide desired spacing between product comprising:

conveying product trough a control zone at a controlled speed, said control zone having an entry portion and a discharge portion;

sensing leading and trailing edges of packages in said control zone;

monitoring linear movement of packages through said control zone;

tracking the centerline of a package in said control zone as a function of the leading and railing edges of that package and the linear movement of that package in said control zone;

determining the amount of adjustment of the controlled speed in order to provide a desired gap between a pair of product in said control zone; and

adjusting said controlled speed only when the centerline of the first and said pair of product reaches said discharge portion.

9. The method in claim 8 wherein said adjusting includes changing between a nominal speed and one of a speed higher than said nominal speed and a speed lower than said nominal speed.

10. The method in claim 9 wherein said changing includes accelerating and decelerating between said nominal speed and one of said other speeds at a substantially constant rate.

11. The method in claim 8 wherein said sensing is performed at said entry portion of said control zone.

17. The method in claim 8 wherein said sensing is performed at said entry portion of said control zone.

12. A method of inducting single-file product in order to provide desired spacing between product comprising:

conveying product through a control zone at a controlled speed, said control zone having an entry portion and a discharge portion;

sensing leading and trailing edges of product in said control zone;

monitoring linear movement of product through said control zone;

determining the estimated time of arrival of a product at said discharge portion as a function of the leading and trailing edges of that product and linear movement of that product in said control zone;

determining a desired time of arrival of a product at said discharge portion as a function of the time that a previous product was at said discharge portion in order to adjust the estimated time of arrival of that product toward the desired time of arrival of that product;

limiting said speed adjustment as a function of the distance of that product from said discharge portion so that the controlled speed can be returned to a predetermined speed before that package reaches said discharge portion; and

adjusting said controlled speed by the limited speed adjustment.

13. The method in claim 12 including limiting said speed adjustment as a function of the distance of the centerline of that product from said discharge portion.

14. The method in claim 12 wherein said adjusting includes changing between a nominal speed and one of a speed higher than said nominal speed and a speed lower than said nominal speed.

15. The method in claim 14 wherein said changing includes accelerating and decelerating between said nominal speed and one of said other speeds at a substantially constant rate.

16. The method in claim 12 including adjusting said controlled speed only when the centerline of the first of a pair of product reaches said discharge portion.

18. An induct control conveyor adapted to providing controlled spacing between single-file product comprising:

a metering conveyor that is of a size to include more than one product at a time;

a speed control for said metering conveyor;

a product monitor for monitoring movement of product on aid metering conveyor;

a computer that is responsive to said product monitor and is programmed to determine an estimated time of arrival o a product at a discharge portion of said metering conveyor if that product is conveyed at a present speed and a desired time of arrival at said discharge portion of the product closest to said discharge portion in order for that product closest to said discharge portion to be optimally spaced from a downstream product;

said computer further being programmed to control said speed control in order to cause the estimated time of arrival of that product closest to said discharge portion to approach the desired time of arrival of that product; and

said computer further being programmed to adjust the estimated time of arrival of other product on said metering conveyor as a function of speed changes that have occurred while that other product is on said metering conveyor.

19. The induct control conveyor in claim 18 wherein said product monitor includes a detector for detecting leading and railing edges of product.

20. The induct control conveyor in claim 19 wherein said product monitor further includes a tracker for tacking linear movement of said metering conveyor.

21. The induct control conveyor in claim 19 wherein said product monitor includes a said detector only at said a product entry portion of said metering conveyor.

22. The induct control conveyor in claim 18 wherein said computer is programmed to determine a centerline of product on said metering conveyor in the direction of product movement.

23. The induct control conveyor in claim 18 wherein said computer is programmed to determine a desired speed change that would cause said estimated time of arrival of that product closest to said discharge portion to be the same as the desired time of arrival of that product closest to said discharge portion and limit said speed change to that portion of said desired speed change which can be effected including returning the speed to said present speed before a following product reaches said discharge portion.

24. An induct control conveyor adapted to providing controlled spacing between single-file product comprising:

a metering conveyor that is of a size to include more than one product at a time;

a speed control for said metering conveyor;

a product monitor for monitoring movement of product on said metering conveyor;

a computer that is responsive to said product monitor and is programmed to determine an amount of adjustment of said speed control in order to provide a desired gap between a pair of product discharged from said metering conveyor and to adjust the speed of said speed control only when the centerline of the first of said pair of product is discharged from said metering conveyor.

25. The induct control conveyor in claim 24 wherein said speed control is adapted to controlling the speed of said metering conveyor and one of a nominal speed, a speed higher than said nominal speed and a speed lower than said nominal speed and wherein said computer adjusts the speed of said speed control by changing between said nominal speed and one of said other speeds.

26. The induct control conveyor in claim 25 wherein said speed control is adapted to accelerate and decelerate between said nominal speed and one of said other speeds at a substantially constant rate.

27. The induct control conveyor in claim 24 wherein said product monitor includes a detector for detecting leading and trailing edges of product.

28. The induct control conveyor in claim 27 wherein said product monitor further includes a tracker for tracking linear movement of said metering conveyor.

29. The induct control conveyor in claim 27 wherein said product monitor includes a said detector only at said a product entry portion of said metering conveyor.

30. An induct control conveyor adapted to providing controlled spacing between single-file product comprising

a metering conveyor that is of a size to include more than one product at a time and having a product entry portion and a product discharge portion;

a speed control for said metering conveyor;

a product monitor for monitoring movement of product on said metering conveyor;

a computer that is responsive to said product monitor and is programed to determine the estimated time of arrival of a product at said discharge portion as a function of the leading and trailing edges of that product and linear movement of that product in said control zone and to determine a desired time of arrival of a product at said discharge portion as a function of the time that a previous product was at said discharge portion;

said computer being programmed to determine an amount of speed adjustment that will cause the estimated time of arrival of that product to approach the desired time of arrival of that product and to limit said speed adjustment as a function of the distance of that product from said discharge portion so that said speed control can return said metering conveyor to a predetermined speed before that package reaches said discharge portion; and

said speed control being responsive to said computer to control the speed of said metering conveyor to the limited speed adjustment.

31. The induct control conveyor in claim 30 wherein said speed control is adapted to controlling the speed of said metering conveyor at one of a nominal speed, a speed higher than said nominal speed and a speed lower than said nominal speed and wherein said computer adjusts the speed of said speed control by changing between said nominal speed and one of said other speeds.

32. The induct control conveyor in claim 31 wherein said speed control is adapted to accelerate and decelerate between said nominal speed and one of said other speeds at a substantially constant rate.

33. The induct control conveyor in claim 30 wherein said product monitor includes a detector for detecting leading and trailing edges of product.

34. The induct control conveyor in claim 33 wherein said product monitor further includes a tracker for tracking linear movement of said metering conveyor.

35. The induct control conveyor in claim 33 wherein said product monitor includes a said detector only at said a product entry portion of said metering conveyor.