GB2279324A

GB2279324A - Pallet locator for fork lift

Info

Publication number: GB2279324A
Application number: GB9411031A
Authority: GB
Inventors: Stephen John Bridge
Original assignee: British Nuclear Fuels PLC
Current assignee: Sellafield Ltd
Priority date: 1993-06-29
Filing date: 1994-06-02
Publication date: 1995-01-04
Anticipated expiration: 2014-06-02
Also published as: GB9313374D0; GB2279324B; GB9411031D0

Abstract

A safety device for preventing excessive movement of a load supported by a fork-lift truck, comprises a spring-operated linkage system 14 movable between inoperative and operative positions figs 4 and 5 respectively. The linkage system includes an operating lever 24 which is connected to a latch 21 by a link 25. A spring 26 acts on the latch 21 so as to continually bias the linkage system to the inoperative position (fig 4). When the lifting apparatus is supporting a load 4, the linkage system is moved to the operative position (fig 5) by engagement of the operating lever 24 with the load 4. In this position the latch 21 prevents excessive movement of the load. The safety device may be positioned between two load-supporting prongs on the lifting apparatus, the prongs being insertable into guides provided on the load. <IMAGE>

Description

Safety Device for Lifting APparatus The present invention relates to mechanical handling apparatus for lifting and transporting loads. More particularly, the invention relates to a safety device for use withmechanical handling apparatus, for example, a fork-lift truck, to facilitate the lifting and transporting of loads in a safe manner.

In one known situation, fork-lift trucks are used to lift and transport stillages or pallets supporting a number of nuclear fuel rods from one location to another.

The stillages stand on four legs so that there is sufficient ground clearance to enable the two prongs of the fork-lift truck to be inserted beneathtit. On occasions, the prongs have been incorrectly positioned beneath the stillage by the fork-lift truck operator, resulting in an unbalanced load. During transport, this can result in excessive slippage of the load or possibly in the load falling off the prongs. It will be apparent that such an occurrence can lead to damage of the fuel rods, which is very costly, or to possible serious injury to personnel.

It is an object of this invention to provide a safety device for use with mechanical handling apparatus which overcomes the aforementioned disadvantages.

According to the invention there is provided a safety device adopted for use with apparatus for lifting and transporting a load, the safety device comprising a linkage system movable between an inoperative position and an operative position which the linkage system occupies when the apparatus is supporting a load and in which the system serves to prevent excessive movement of the load, the linkage system comprising a pivotably mounted operating lever and a spring, said spring acting on the linkage system so as to bias the system towards the inoperative position, whereby the linkage system is retained in the operative position by engagement of the operating lever with the load.

The linkage system preferably includes a pivotably mounted latch adapted to prevent excessive movement of the load when the linkage system is in the operative position.

Preferably, the operating lever is pivotably mounted at a position intermediate its two ends, one of the said ends being connected to a link which connects said operating lever with the latch, wherein the spring acts on the latch so as to exert a force on said one end of the operating lever through the link, whereby the other of the said ends of the operating lever is pressed into engagement with the load.

In a preferred arrangement the safety device is operated by raising said device so that the other of said ends of the operating lever engages with the load, whereby the resulting pivotal movement of the operating lever causes the linkage system to move to the operative position.

The apparatus for lifting and transporting the load is preferably of the type which includes two load supporting prongs, the safety device being located at a position between the two prongs.

Preferably the safety device and the two prongs are attached to a vertically movable member of the lifting and transporting apparatus.

Desirably, the other of said ends of the operating lever extends above a plane coinciding with the upper surface of the two prongs. Thus, on raising the movable member of the lifting and transporting apparatus the other of said ends first contacts the load, thereby causing the linkage system to move to the operative position followed by contact of the two prongs with the load to provide support therefor.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a front elevation of a stillage which constitutes a load to be moved; Figure 2 is a plan view of the stillage; Figure 3 is a plan view showing the stillage in chaindot lines in position on a lifting and transporting apparatus; and Figures 4 and 5 show the latch mechanism of a safety device in the inoperative and operative positions, respectively.

Figures 1 and 2 illustrate a load, in the form of a stillage 1 supporting a number of nuclear fuel rods 2, which is to be transported by a mechanical handling apparatus, such as a fork-lift truck, to a desired location. The stillage 1 includes a platform 3 which is generally in the form of a tray having box-sectioned side members 4, end plates 5 and an underside surface 6. The stillage 1 is supported on legs 7 which extend upwardly through the platform 3 to provide four pillars 8. Welded to the pillars 8 are two transverse frame members 9 and two longitudinal frame members 10. In this example the fuel rods 2 are supported by the two transverse frame members 9. For clarity reasons, the fuel rods are not shown in Figure 2. Welded to the underside surface 6 of the platform 3 are two guides 11, each of which forms a rectangular recess 12 for receiving a prong of a fork-lift truck.The guides 11 are positioned at equal distances along the underside of the platform on either side of the centre of the stillage.

As seen in Figure 3, two prongs 13 of a fork-lift truck have been inserted in the guides 11. Thus, by raising the prongs 13 into engagement with the underside surface 6, the stillage 1 can be transported by the truck to the desired location. To prevent excessive movement of the stillage during transport, the rork-lift truck is equipped with a safety device 14 which is attached to the truck by an extension piece 15. The extension piece 15, which is positioned centrally between the prongs 13, is fixed to a vertically movable, load-bearing cross member 16 of the truck. Since the prongs 13 are also connected to the cross member 16, raising and lowering ofthis member cause simultaneous vertical movement of the prongs and the safety device.

The safety device 14 comprises a latch mechanism which is shown in Figures 4 and 5. Figure 4 shows the latch mechanism in an inoperative position, which is occupied when not in use, and Figure 5 shows the latch mechanism following activation to an operative position, which is occupied during lifting and transporting of the stillage.

The latch mechanism generally comprises a springoperated linkage system. It includes two side plates 17 between which a support block 18 is located for attaching the mechanism to the extension piece 15. The linkage system comprises a latch 19 which is pivotably mounted on a pivot pin 20 supported by the side plates 17. At the end remote from the pivot point the latch 19 is provided with a projection 21. An operating lever 22 is pivotably mounted at a position intermediate its two ends on a pivot pin 23, also supported in the side plates 17. At its forward end the operating lever 22 has a rounded protuberance 24 which, in the inoperative position of the latch mechanism, extends above a horizontal plane coinciding with the upper surfaces of the prongs 13. At its other end the operating lever 22 is pivotably attached to one end of a link 25, the other end of which is pivotably attached to the latch 19. An extension spring 26 is fixed at one end to a pin 27 on the latch 19 and is anchored at the other end to a pin 28 fixed to the side plates 17. The spring 26 exerts a force on the latch 19 so that the latch mechanism is biased towards its inoperative position. In this position the latch 19 is pulled against a stop 29, also fixed to the side plates 17.

In a procedure for lifting and transporting the stillage, the safety device operates in the following manner. An operator manoeuvres the fork-lift truck in front of stillage 1 so as to position the prongs 13 adjacent to the entrance of the prong guides 11. The operator then adjusts the position of the prongs 13 in the vertical direction, by movement of the cross member 16, and in the horizontal direction until they align with the recesses 12 in the guides 11. On forward movement of the truck the leading ends of the prongs 13 enter and move along the recesses 12 until the position as shown in Figure 3 is reached. The extension piece 15 enables the operator to view the safety mechanism 14 so that it can be positioned correctly in relation to the side member 4 of the stillage 1.At this stage of the procedure, the safety mechanism linkage system is in the inoperative position shown in Figure 4.

The prongs 13 are then raised so that they move towards the underside surface 6 of the stillage platform 3. Since the safety device 14 is raised together with the prongs 13, the protuberance 24 on the operating lever 22 comes into contact with the underside surface 6. This causes the operating lever 22 to turn about the pivot pin 23 in a clockwise direction, as viewed in Figure 5. The operating lever 22 moves the link 25 in an upwards direction so that, in turn, the latch 19 rotates about the pivot pin 20, also in a clockwise direction, in opposition to the force exerted by the spring 26. The linkage system attains the operative position, as seen in Figure 5, when the upper surfaces of the two prongs 13 contact the underside surface 6 of the platform 3. In this position, the latch 19 extends horizontally above the side member 4 with the projection 21 located beyond the side member.

After ensuring that the safecy mechanism 14 has achieved its operative position, the operator initiates raising of the prongs 13 so as to lift the stillage 1. By moving the truck the stillage 1, together with the fuel rods 2, can now be transported to the desired location without any danger of excessive movement by the stillage.

Excessive forward movement of the stillage on the prongs is prevented by the latch projection 21. Since the two prong guides 11 are symmetrically positioned on either side of the centre of the stillage, and the safety device linkage mechanism operates correctly only when the prongs extend beneath the stillage by a certain amount, safe balancing of the load during transport is ensured.

After placing the stillage on the ground, the prongs 13 are lowered away from the underside surface 6 of the stillage platform 3. Since the operating lever 22 is now free to pivot, the pressure exerted by the spring 26 causes the latch 19 to pivot about the pin 20 and move into contact with the stop 29. Thus, the linkage system of the safety device 14 returns to the inoperative position, as shown in Figure 4. The prongs 13 are then withdrawn from the guides 11.

Claims

1. A safety device adapted for use with apparatus for lifting and transporting a load comprises a linkage system movable between an inoperative position and an operative position which the linkage system occupies when the apparatus is supporting a load and in which the system serves to prevent excessive movement of the load, the linkage system comprising a pivotably mounted operating lever and a spring, said spring acting on the linkage system so as to bias the system towards the inoperative position, whereby the linkage system is retained in the operative position by engagement of the operating lever with the load.

2. A safety device according to Claim 1, wherein the linkage system includes a pivotably mounted latch adapted to prevent excessive movement of the load when the linkage system is in the operative position.

3. A safety device according to Claim 1 or Claim 2 wherein the operating lever is pivotably mounted at a position intermediate its two ends, one of the said ends being connected to a link which connects said operating lever with the latch, and wherein the spring acts on the latch so as to exert a force on said one end of the operating lever through the link, whereby the other of the said ends of the operating lever is pressed into engagement with the load.

4. A safety device according to Claim 3, wherein the safety device is operated by raising said device so that the other of said ends of the operating lever engages the load, whereby the resulting pivotal movement of the operating lever causes the linkage system to move to the operative position.

5. A safety device as claimed in any one of Claims 1 to 4, wherein the lifting and transporting apparatus includes two prongs for supporting the load, the safety device being located at a position between the two prongs.

6. A safety device as claimed in Claim 5, wherein the safety device and the two prongs are attached to a vertically movable member of the lifting and transporting apparatus.

7. A safety device as claimed in Claim 6, wherein the other of said ends of the operating lever extends above a plane coinciding with the upper surfaces of the two prongs, whereby on raising the movable member of the lifting and transporting apparatus the other of said ends of the operating lever first contacts the load so as to cause the linkage system to move to the operative position and then the two prongs contact the load so as to provide support therefor.

8. A safety device substantially as hereinbefore described with reference to Figures 3, 4 and 5 of the accompanying drawings.