CA1218326A - Conveyor system - Google Patents

Abstract

CONVEYOR SYSTEM

Abstract of the Disclosure A conveyor system comprising a track, a carrier movable along the track, and a tractor for moving the carrier along the track past a station. The carrier includes an extendible-retractible coupling connecting the tractor and the carrier such that when the carrier is stopped at a station, the coupling can be actuated to precisely locate the carrier at the station.

Description

~Z~326 This invention relates to conveyor systems and particularly conveyor systems wherein a carrier is moved by a power device along a track to a work station.

Background and Summary of the Invention In certain types of conveyor systems, it is customary to provide a motor power unit that is movable along a track for moving load carriers along the track. In a typical arran~e--ment, the track is mounted overhead and the carrier supports loads and is moved by a tractor. With the advent of automatic devices and machines including robotic type machines, it has become essential to be able to stop the load carrier in a precise position or location at a work station for the performance of work on the load. Heretofore controls for the motor power units have been unable to provide accurate positioning in a precise manner, for example, on the oraer of plus or minus one milli-meter.
Accordingly, among the objectives of the present invention are to provide a conveyor system which will effectively move a load carrier into a station and position the load carrier in a precise position at the work station; which system is rel-atively simple and economical to rnanufacture, install and maintain.
In accordance with the invention, an extendible-retractible coupling is provided between the motor power unit and the carrier such that when the carrier is stopped at a station, the coupling can be actuated to precisely locate the carrier at the station.

'121~326 Description of the Drawings FIG. 1 is a fragmentary side elevational view of a conveyor system embodying the invention.
FIGo 2 is a diagram showing the manner in which the carrier is positioned.
FIG. 3 is a diagram showing the manner in which the extendible-retractible coupline functions.
FIG. 4 is an electrical schematic view o~ the c~r circuit.

12~326 Description Referring to FIG. 1, the invention is shown as applied to a monorail tractor conveyor which comprises a rnonorail 10 defining a track, a carrier 11 having wheels 12 engaging the track 10 and a motor power unit in the form of a tractor 13 that includes an electrie motor-brake that rotates a drive wheel 14 whieh frietionally engages the underside of the traek 10 and move the power unit along the track 10. 'rhe earrier 11 is adapted to earry a load and also carries a power unit 15 having controls for sensors as presently described.
Sueh an arrangement is known in the art.
In accordance with the invention, a retractible-extendible coupling 16 is provided on the carrier 11 between the motor power unit 13 and carrier 11 and comprises an electrie motor 17 that reeiprocates a shaft 18 through a gear box 19.
The end of the shaft 18 is pivotally connected to the motor power unit 13.
The carrier 11 supports a photocell #1 and photocell #2 which projeet beams of radiant energy sueh as visible light horizontally toward reflectors positioned alongside the path of the carrier at a station.
In normal station-to-station transport the coupling is fully retracted. As the traetor 13 and earrier 11 approach a work station, a signal from photocell #l causes the tractor 13 to reduce its speed from fast to slow and to stop.
Referring to FIG. 2, the signal to stop always places the centre position of the stop station between the centre posi-3.

121832t~

tion of the carrier and the tractor drive in the area represented by band A. When the tractor has completely stopped a signal is given to extend shaft 18 of the coupling 16 pushing the carrier towards its final required stopping position. As the centre line of the load reaches the required centre line of the stop position of the station, a signal from highly sensitive photocell #2 causes the coupling 16 to cease motion. This distance of possible movement of the carrier is represented by the band B. The centre line of the load is now located accurately within plus/minus 1 mm. of the predestinated point along the track. On start-up to exit the station, the coupling 16 is retracted to its minimum length in readiness in the next station.
The length of stroke to the coupling is related to the required stopping distance after receipt of the final signal to stop. The speed of the stroke of the coupler has a relationship to the accuracy of final positioning. However, with additional contro]s, the speed of the coupler can be changed for the last several millimeters of travel by inserting additional detectors and controls.
Referring to FIG. 4, the schematic of the control circuit, as the tractor 13 with the carrier 11 enters the work station to which it has been programmed to stop, photocell ~PC-l) is energized causing a time relay (TD-l) to be energized which causes the tractor motor to stop. Due to the coasting of the tractor, time delay TD-l is sealed in by its own contact since the tractor will move beyone the reflective signal causin~
photocell PC-l to be energized. Time relay TD-l provides a ~Z~3326 time delay to allow for stopping and/or reduction in load sway.
After the time delay, the coupling 16 is energized (MFL) causing the load carrier to be moved in a direction toward the center line of station. At the center line of the station, second photocell (PC-2) is energized causing the load carrier to accuately stop (PC-2 energizes CR-2). Once the tractor is ready to depart the station, a relay (CR) causes CR-2 to drop out and other controls will cause the tractor motor to be energized. Once the tractor motor is energized the coupling 16 is reversed, causing the load carrier to move to a home position in readiness for next station entry. Should a malfunction occur and the second photocell (PC-2) is not energized, the coupling 16 extenas to its extreme position, tripping LS-2.
This stops the forward motion of the coupling 16 as well as energizes a relay (CR-l) which will prevent the tractor from moving and also sound an alarm.
As shown in FIG. 3, limit switches LS-l and LS-2 are associated with the coupling 16 to limit the extent of movement of the shaft 18.
Although the invention has been described as preferably being applied to an overhead tractor ana carrier system, it can also be applied to other motor power unit and carrier systems such as driverless vehicles and carriers.
It can thus be seen that there has been provided a conveyor system wherein a load carrier driven by a motor power unit can be positioned at a station in a precise position.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1.
A conveyor system comprising means defining a track, a carrier movable along said track, power means for moving said carrier along said track, said track extending past a station, an extendible-retractible coupling connecting said power means and said carrier such that when the carrier is stopped at a station, said coupling can be actuated to precisely locate the carrier at the station.

2.
The conveyor system set forth in claim 1 including means at the station for sensing the approach of the carrier to the station and actuating the power means to stop the power means.

3.
The conveyor system set forth in claim 2 including means operated upon stopping of the power means for actuating said coupling to move said carrier relative to said power means and precisely locate said carrier at the station.

6.

4.
The conveyor system set forth in claim 3 including sensing means operable to stop operation of the coupling means when the carrier reaches the precise position at the station.

5.
The conveyor system set forth in claim 4 wherein said first sensing means comprises a first photo sensor.

6.
The conveyor system set forth in claim 5 wherein said second sensing means comprises a second photo sensor.

7.
A conveyor system comprising an overhead track, a carrier movable along said track, a tractor movable along said track for moving said carrier along said track, said track extending past a work station, an extendible-retractible coupling connecting said tractor and said carrier such that when the carrier is stopped at a work station, said coupling can be actuated to precisely locate the carrier at the work station.

7.

8.
The conveyor system set forth in claim 7 including means at the station for sensing the approach of the carrier to the station and actuating the power means to stop the power means.

9.
The conveyor system set forth in claim 8 including sensing means operated upon stopping of the power means for actuating said coupling to move said carrier relative to said power means and precisely locate said carrier at the work station.

10.
The conveyor system set forth in claim 9 including sensing means operable to stop operation of the coupling means when the carrier roaches the precise position at the work station.

11.
The conveyor system set forth in claim 10 wherein said first sensing means comprises a first photo sensor.

12.
The conveyor system set forth in claim 11 wherein said second sensing means comprises a second photo sensor.

8.