GB2188014A

GB2188014A - Materials handling system

Info

Publication number: GB2188014A
Application number: GB08607109A
Authority: GB
Inventors: Charles Edward Revell
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1986-03-21
Filing date: 1986-03-21
Publication date: 1987-09-23
Also published as: GB8607109D0; GB2188014B

Abstract

A materials handling system which can be used for transferring components to be machined from one machine A,B,C,D,E to another uses a carriage 14 which is guided by an embedded track 16 in the floor. The carriage moves past a docking station 20 associated with each machine, and the docking station allows a small stock of parts awaiting machining and of machined parts to be held. A gantry 22 transfers parts between the machine and the docking station. The carriage 14 is electrically driven from a mains supply and can be controlled to visit the machines adjacent its track in any desired sequence. <IMAGE>

Description

SPECIFICATION Materials handling system This invention relates to a materials handling system for handling workpieces which are to be operated on by a number of different machines (generally machine tools). One example of workpieces which could be handled by this system is the steel blanks from which vehicle transmission gear shafts are to be formed, but the invention is not restricted to such an application.

It is known to mount a fixed conveyor so that it extends past a number of machines, and then to have a gantry associated with each machine which picks a workpiece from the conveyor and returns it to the conveyor after it has been operated on by the machine.

In this system, the order in which the workpiece passes through the machines is preordained by the routing of the conveyor; the whole line has to work at the speed of the slowest machine and the whole line is stopped if one machine should be stopped for any reason. Furthermore, the presence of the fixed conveyors restricts flexibility and obstructs access to the machines such that it is necessary either to construct a bridge over the line or to walk around the end of the line to get to all sides of the machine.

According to the invention, there is provided a materials handling system comprising a number of machines arranged to perform sequential operations on a workpiece, a docking station associated with each machine for holding a stock of workpieces, means for loading and unloading workpieces between the tool and the docking station, an embedded rail running in the floor past all the docking stations, a carriage guided by the rail for movement past each docking station and arranged so that workpieces can be transferred from the carriage to the docking station and vice versa, and control means for controlling movement of the vehicle so that it can visit the docking stations in any desired sequence.

The docking stations and the carriage preferably have locating means which provide signals to the control means to stop the carriage in a precise position relative to each docking station to allow workpiece transfer. The locating means may include a mechanism which physically locks the carriage in position relative to the docking station during workpiece transfer.

Preferably the carriage is electrically driven, with the electricity supply being fed to the carriage from an overhead busbar. The power supply could alternatively come from batteries within the carriage.

It is a major advantage of the invention that there need be no fixed installation which would prevent access to the machine from all sides. Service personnel can walk all round each machine without obstruction.

The carriage will be provided with the necessary safety equipment to ensure that it stops very quickly if it should hit an obstruction. Also, the use of a carriage guiding rail embedded in the floor means that no fixed guards around the track of the carriage will be required.

The machines are preferably arranged in a straight line so that the the rail on which the carriage is guided also lies in a straight line.

The invention will now be further described, by way of example, with refernce to the accompanying drawings, in which: Figure 1 is a schematic plan view of a materials handling system according to the prior art; Figure 2 is a schematic plan view of a materials handling system according to the invention; Figure 3 is a plan view of a docking station; Figure 4 is a side view of a carriage; Figure 5 is a plan view of the carriage; Figure 6 is an underneath view of the carriage; Figures 7 and 8 are respectively plan and fragmentary sectional views of the floor track for the carriage; and Figure 9 shows an alternative rail design.

Figure 1 shows a processing line with five sequentially arranged machines A,B,C,D and E.

A conveyor 10 runs alongside the line of machines and conveys a continuous stream of workpieces, and a gantry 12 is provided for each machine to feed workpieces between the machine and the conveyor.

With this arrangement, an operator standing on the right-hand side of the line, monitoring operation of the line generally, cannot easily cross the conveyor to attend to a problem on a particular one of the machines. He will have to walk around one end of the line, or a bridge will have to be built across the conveyor.

Because there is no provision for workpieces moving other than in the sequence A B-C-D-E, a workpiece can only move on to machine B when the operations to be performed on it by machine A have been properly completed. This situation is repeated all along the line with the result that the whole line must work at the speed of its slowest operation. If one machine is down for any reason the whole line stops.

In Figure 2 however, the conveyor 10 is replaced by a carriage 14 guided by a rail 16.

A control box 18 controls the movement of the carriage, and can be programmed so that the carriage visits the machines in any desired order and moves either forwards or backwards. The rail 16 is embedded in the floor so that it presents no obstruction to people working on the floor, and does not prevent people moving from one side of the rail to the other. To feed the machines, a short length of conveyor 20 is arranged adjacent each, and a gantry 22 straddles the conveyor and the associated machine to feed workpieces from the conveyor to the machine.The carriage 14 docks against one end of the conveyors 20 so that workpieces (normaliy on pallets) can be transferred, with workpieces to be operated on by the machine being taken from the carriage on to the conveyor and the workpieces with which the machine has finished being offloaded from the conveyor onto the carriage.

With this arrangement, the machines can be approached from all sides. The rail guiding the carriage presents no impediment to movement across the path of the carriage. If one of the machines is down, it can be bypassed, and the sequence of machining operations can be changed. If one particular operation is slow, two machines can be placed in the line to perform that operation and the carriage can move workpieces between the two, parallel machines and the preceding and subsequent machines as necessary.

The conveyor 20 (also called a docking station) is shown in more detail in Figure 3. It comprises two parallel tracks 24 and 26 with chain or powered and free conveyors on which pallets 28 move in opposite directions.

The gantry 22 provided with guarding 23 picks components from a load position situated either on the "in" track 24 or the "out" track 26. The gantry may pick components directly from a pallet 28 or from a lift unit, provided to lift parts from the pallet and to elevate them to a load height comparable to the gantry 22. The lift unit may also rotate components through 90 or 180 degrees to suit machine orientation. If necessary, pallets can be manually removed from the end of the conveyor at 30. The carriage 14 will dock against the end of the conveyor which is lowermost in the Figure.

The carriage 14 has a number of platforms 32 for receiving pallets 28. These platforms have load-carrying surfaces formed by chains or rollers, at least some of which are powered. Wheels 34 run on the floor 36 and soft safety bumpers 38 are fitted at each end for safety of operators and to avoid any damage should the carriage run into an obstruction.

The carriage is electrically powered from a remote supply, and power reaches the motor through overhead conductors 40 and a mast 42. Control signals from the control box 18 are passed to the carriage 14 by an inductive loop communication system buried in the floor. A control panel 44 is provided on the carriage for operating a drive to the powered rollers for discharging or taking on pallets.

The running gear of the carriage comprises a wheel at each corner. The rear wheels 46 are driven and the front wheels 34 are free.

Guide probes 50 are mounted at both ends.

The guide probes 50 enter a rail in the form of a channel 52 embedded in the floor (Figures 7 and 8). The wheels should be nonmetallic. Figure 9 shows an alternative guide mechanism with a grooved wheel 54 running on a sunken rail 56.

As the carriage approaches one of the docking stations, sensors mounted on the carriage (or on the docking station) intiate a slowing down. The maximum speed of the carriage between stations can be 30 m/min, and the docking approach speed can be 6 m/min or less. As the carriage reaches its docked position, a bolt 56 (Figure 4), or a comparable mechanism, is extended into a corresponding bore on the docking station to provide exact location during docking. It may be possible to dispense with the bolt or other mechanism to ensure accurate docking if the control is sufficiently accurate itself.Either one of the platforms 32 may register with either of the tracks 24 or 26, and the carriage can have facilities for locating itself at either track and for indexing between the tracks.

The carriage can move in either direction.

The use of a rail to guide the carriages means that they can be accurately and reliably positioned.

Because of the easy access to the machine, in the event of breakdown of a gantry the machine could be hand fed by an operator working from the position 30.

If the carriage 14 should break down, it can be replaced until back in operation by a manually propelled trolley.

In operation, the presence of the "stockpile" at the docking station means that each machine has up to four pallets full of workpieces ready to be worked on. Up to four pallets of machined workpieces can also be stored before they have to be collected. This allows considerable operating flexibility.

Claims

1. A materials handling system comprising a number of machines arranged to perform sequential operations on a workpiece, a docking station associated with each machine for holding a stock of workpieces, means for loading and unloading workpieces between the tool and the docking station, an embedded rail running in the floor past all the docking stations, a carriage guided by the rail for movement past each docking station and arranged so that workpieces can be transferred from the carriage to the docking station and vice versa, and control means for controlling movement of the vehicle so that it can visit the docking stations in any desired sequence.

2. A materials handling system as claimed in Claim 1, wherein the docking stations and the carriage have locating means which provide signals to the control means to stop the carriage in a precise position relative to each docking station to allow workpiece transfer.

3. A materials handling system as claimed in Claim 2, wherein the locating means includes a mechanism which physically locks the carriage in position relative to the docking station during workpiece transfer.

4. A materials handling system as claimed in any preceding claim, wherein the carriage is electrically driven.

5. A materials handling system as claimed in Claim 4, wherein the electricity supply is fed to the carriage from overhead.

6. A materials handling system as claimed in Claim 4, wherein the electricity supply is fed to the carriage from batteries housed within the carriage.

7. A materials handling system as claimed in any preceding claim, wherein the carriage is provided with the necessary safety equipment to ensure that it stops very quickly if it should hit an obstruction.

8. A materials handling system as claimed in any preceding claim, wherein the machines are arranged in a straight line so that the the rail on which the carriage is guided also lies in a straight line.

9. A materials handling system as claimed in any preceding claim, wherein the carriage is provided with roller tables for receiving workpieces, the roller tables having powered and free rollers.

10. A materials handling system as claimed in any preceding claim, wherein the docking station is able to hold a stock of workpieces waiting to be operated on by the machine and a stock of workpieces which have been worked on.

11. A materials handling system as claimed in any preceding claim, wherein the docking stations include conveyors for conveying workpieces to and from a position where they can be picked up and fed to the machine.

12. A materials handling system as claimed in Claim 11, wherein the conveyor includes a location where workpieces are accessible to an operator.

13. A materials handling system as claimed in any preceding claim, wherein the embedded rail is a groove in the floor, and the carriage has a depending pin which follows the groove.

14. A materials handling system as claimed in Claim 13, wherein the carriage is supported on wheels which run on the floor.

15. A materials handling system as claimed in any preceding claim, wherein the carriage has safety bumpers around it.

16. A materials handling system as claimed in any preceding claim, wherein the ccontrol means for controlling movement of the vehicle comprises an inductive loop communication system buried in the floor.

17. A materials handling system substantially as herein described, with reference to Figures 2 to 8 of the accompanying drawings.