Accumulating conveyor with self-propelled pallets

• US 4,987,834 A
• Filed: 06/20/1989
• Issued: 01/29/1991
• Est. Priority Date: 10/23/1986
• Status: Expired due to Fees

• Current Assignee: Roberts Sinto Corp. (Sintokogio Limited)
• Original Assignee: Roberts Sinto Corp. (Sintokogio Limited)
• Inventors: Foster, James F., Pol, Kenneth J., Peck, Glenn L. Jr.
• Primary Examiner(s): Pedder, Dennis H.
• Assistant Examiner(s): Pape, Joseph D.
• Application Number:
  US07/370,141
• Time in Patent Office: 588 Days
• Field of Search: 104/127-129, 104/287, 104/288, 104/295, 104/299-301, 104/27, 104/249, 104/250-252, 104/88, 246/167 D, 246/182 R, 246/186, 246/174, 246/184, 246/187 B, 246/187 R, 246/187 A, 198/341, 198/464.4, 198/460, 180/169
• US Class Current: 104/300
• CPC Class Codes: B23Q 7/1436 using self-propelled work holders

Abstract

An accumulating conveyor formed by a series of self propelled pallets (18) running on a track (20), with non-contacting proximity detectors (24A, 24B) located on the front and rear of each pallet (18), and an on board control circuit (26) causing deenergization of the drive motor (22) when a stopped pallet (18) is detected ahead, or when barrier members (28, 30) are positioned ahead. Slow down, stopping and reversing of the drive may be controlled by side mounted photo detector switches (40A, 40B, 52A, 52B) activated by photo emitter devices (42A, 42B, 54A, 54B) mounted along the path of the pallets (18). A bilevel feed and return track (20A, 20B) may be traversed by the pallets (18), reversed to be driven in either direction, and either the forward or rear proximity switch (24A or 24B) activated by the control circuit (26) depending on the direction of travel of the car. Elevator mechanisms (48, 50) are located at either end of the bilevel track (20A, 20B) for raising and lowering the pallets (18) between levels.

Claims

1. An accumulating conveyor (10) including a track (20), one or more stations (14) arranged along said track (20), a plurality of pallets (18) greater in number than said one or more stations (14) whereby said pallets (18) are accumulated upstream from each of said one or more stations (14, 16), an operation performed on each of said workpieces (W) at said one or more stations (14);

each of said plurality of pallets (18) having a propelling drive motor (22), each of said plurality of pallets (18) disposed on said track (30) in a series for self propelled movement along said track (20), said track (20) directing said self propelled pallets (18) into each of said one or more stations (14,

     16);

station control means (40a, 40b, 42a, 42b, 24,

     30) for causing stopping of each of said pallets (18) in each of said stations (14,

     16) by discontinuing propelling drive thereof;

accumulating control means (24,

     26) carried by each pallet (18) in which said pallets (20) are able to be queued one behind the other upstream at one or more of said stations (14,

     16), said accumulating control means including reflective photoelectric sensor means (24) carried by each pallet (18) sensing the approach of said pallet (18) to the next ahead pallet (18) in said series, by optically detecting an object directly in the path of movement of said pallet at a predetermined substantial distance therefrom;

said accumulating control means further including means (26) responsive to said reflective photoelectric sensor means (24) sensing the approach of said pallet (18) to a next ahead pallet (18) but not responsive to the approach of another pallet (18) to the rear, the discontinue the propelling drive of said pallet (18) by said drive motor (22) as said pallet (18) approaches the next ahead pallet (18) so as to stop said pallet (18) in a position spaced behind the next ahead pallet (18), said predetermined substantial distance is greater enough to insure stopping of said pallet (18) with no contact with the next ahead pallet (18) but is small enough to result in closely spaced queued pallets when a series of pallets (18) are stopped, said accumulator control means again causing initiation of propelling drive to each pallet (18) upon movement of the next ahead pallet (18) away therefrom beyond said predetermined substantial distance;

said accumulating control means characterized by readiness barrier (28) movably mounted to be selectively positioned upstream of at least one of said stations located at a height to be detected by said photoelectric sensor means to cause stopping of said pallet without a collision therewith, said barrier configured to physically prevent propulsion of a pallet therepast in the event said accumulator control means fails, whereby said pallets (18) may be queued behind each other, closely spaced and upstream of each of said stations (14,

     16) behind said readiness barrier and are automatically moved ups step by step as each pallet (18) is propelled into each of said stations (14,

     16) after removal of said readiness barrier.

2. The accumulating conveyor (10) according to claim 1 wherein said station control means includes a locator barrier member (30) positionable in said station (14, 16) to properly locate each of said pallets in said station by being detected by said reflective photoelectric sensor means (24) to discontinue propelling said pallet (18) so as to bring said pallet (18) to rest at a predetermined location in said station (14, 16).

3. The accumulating conveyor (10) according to claim 1 including first and second main tracks (20a, 20b) disposed at different vertical levels, one (20a) above the other (20b), and wherein each of said pallets (18) are propelled in opposite directions on respective first and second main tracks (20a, 20b), said electric drive motor (22) on each of said pallets (18) comprising a reversible electric drive motor (22) and including switching means (52, 54) causing said electrical control circuit (26) to power said drive motor (22) so as to propel said pallet (18) in opposite directions on the respective first and second main tracks (20a, 20b).

4. The accumulating conveyor according to claim 3 wherein a pair of reflective photoelectric sensor means (24a, 24b) are provided on each pallet (18), located on either end of said pallet (18), and wherein said electrical control circuit (26) causes deenergization of said drive motor (22) in response to activation of only one or the other of said pair of photoelectric sensors means (24a, 24b), depending on the direction of propulsion of said pallet (18).

5. The accumulating conveyor (10) according to claim 1 further including a battery (32) carried by each pallet (18) connected to said power control circuit (26) and to said electric drive motor (22) on said pallet (18).

6. The accumulating conveyor (10) according to claim 5 further including a pair of charging conductor bars (34) mounted alongside said track (20), immediately upstream of said station (14, 16), and a pair of charging contacts (108) carried by each of said pallets (18) located to move into engagement with a respective charging conductor bar (34), said contacts (108) connected to said battery (32) to enable an electric charging voltage to be applied thereto upon movement of said pallet (18) to a region immediately upstream of said station (14, 16).

7. The accumulating conveyor (10) according to claim 1 wherein said track (20) comprises parallel, spaced, track members and each of said pallets is supported on three rollers (65, 67, 69) two (65, 67) located to ride on one of said track members, the other (69) on the other track member.

8. The accumulating conveyor (10) according to claim 7 further including a plurality of pairs of guiding rollers (74, 76) carried by each pallet (18) engaging the opposite edges of at least one of said track members.

9. The accumulating conveyor (10) according to claim 8 further including a precision locating and clamping mechanism (315) located in said station (14) comprising a pair of oppositely disposed clamping assemblies (316) each adapted to be successively moved to engage each end of a pallet (18) positioned in said station (14) to position said pallet (18) therebetween.

10. The accumulating conveyor (10) according to claim 3 wherein a readiness barrier member (28) is positioned adjacent each of said stations (14, 16) in the path of pallets (18) in each station (14, 16), lift-lower mechanism (48, 50) at each station, each having an auxiliary track 56 positioned to receive and carry each pallet 18 between said first and second main tracks (20a, 20b), and wherein each of said readiness barrier members (28) is moved to block entry of a succeeding pallet (18) whenever said respective auxiliary track (56) is not aligned with respective first or second main track (20a, 20b) on which each of said pallet (18) approaches, whereby propelling of the next succeeding pallet (18) is prevented by operation of said photoelectric sensor means (24) whenever said auxiliary track (56) is not aligned with said one of said track section (20a, 20b).

11. The accumulating conveyor (10) according to claim 10 further including a locator barrier member (30) attached to the advanced end of said auxiliary track (56) whereby a pallet (18) advancing onto said auxiliary track (56) is stopped upon sensing of said locator barrier member (30) to locate said pallet (18) in said station (14, 16) on said lift-lower means (48, 50).

12. The accumulating conveyor (10) according to claim 1 further including a side mounted photoelectric switch (40b) mounted to the side of each pallet (18) connect to said control circuit (26) to cause deenergization of said electric drive motor (22), and also including a photo emitter device (42b) mounted on said conveyor (12) to come into registry with said side mounted photo electric switch (40b), whereby activation of said photo emitter device (42b) causes stoppage of a pallet (18) moving to bring said side mounted photo electric switch (40b) into registry therewith.

13. The accumulating conveyor according to claim 12 further including a second side mounted photoelectric switch (40a) mounted to he side of each of said pallets spaced from said other side mounted photo electric switch (40b), and a second photo emitter device (42a) located to move into registry with said photoelectric switch (40a) as said pallet (18) advances along said track (20), said second photoelectric switch (40a) connected to said control circuit (26) to cause a reduced speed of said electric drive motor (22), whereby activation of said second photo emitter device (42a) and said second photoelectric switch (40a) causes a reduced speed propulsion of the pallet (18).

14. The accumulating conveyor according to claim 10 wherein said switching means comprises a reversing photo emitter device (52a, 52b) mounted at each lift-lower mechanism (48, 50) and also includes a reversing photo electric switch (54a, 54b) mounted to each pallet (18) located to come into registry with each of said reversing photo emitter device (52a, 52b) after said pallet (18) has been moved to another level by each of said lift-lower mechanisms (48, 50), said reversing photo electric switch means (54a, 54b) connected to said control circuit (26) to cause reversing of the electric drive motor (22) upon excitation by either of said photo emitter devices (52a, 52b)