GB2210854A - Pivotable bucket attachment for fork-lift truck - Google Patents

Abstract

An attachment for a fork-lift truck comprises a receptacle such as a bucket (3) mounted over a pivoting linkage supported by a sub-frame (4) comprising sleeve sections (5) which fit over the forks. The bucket may be tilted from a rest, or loading, position either rearwardly about a first fulcrum (19) to a load-carrying position without passing below the level of the forks or forwardly about a second fulcrum (18) to an unloading position. The preferred linkage is a quadrilateral linkage in which the two fulcra (18, 19) are defined by adjacent corners of the quadrilateral with a fixed distance between them, as provided by a connecting rod (20), with a variable distance between the remaining two corners during movement of the linkage, as provided by hydraulic piston (7) which is actuated to pivot the bucket, such that the bucket is attached to the linkage by means of bearings (17, 18) at the forwardmost corners of the quadrilateral. <IMAGE>

Description

Mortimer O'Keeffe A Fork-lift Attachment The present invention relates to a fork-lift attachment.

There are many instances in which it is useful to adapt a fork-lift device for lifting and loading bulk materials1 particularly fluent materials, such as grain, granular fertiliser, etc. Hitherto, bucket attachments have been devised which fall into three categories depending upon the mode of attachment.

Firstly, the bucket attachment may be attached to the masts of the fork-lift device, once the forks have been removed. Such buckets are not fully satisfactory for loading high hoppers or trucks because they unload by tilting downwards around a fulcrum positioned close to the mast. This allows very little forward reach, so that the truck has tobe loaded from both sides. Also when the level of material in the truck rises to within approximately 2ft. of the top, it becomes impossible for the bucket to tilt downwards enough to dispense its load. There is also the inconvenience of detaching the forks from the mast.

Secondly, the bucket attachment may be attached with the forks in place, wherein the bucket may be tilted or swung rearwardly so as to drop between the forks during a loading operation, as described, for example in GB-2055750A. Once loaded, the mast must be raised by about 3 ft. so as to raise the bucket from ground level to allow it to tip back into a load holding and transport position. This may cause practical problems as more headroom is required. Also, two hydraulic operations are involved to lift and tilt the bucket. The bucket in its tilted position depends below the level of the forks and may hit off the ground.

Thirdly, the bucket attachment may be attached directly to the outermost ends of the forks, for example as described in GB-1,357,295.

Such a bucket gives a good reach and may be tilted forwardly over the tips of the forks to discharge. However, the mechanism does not allow for a rearward tilting motion to tip the bucket from a scoop position into a load-holding and transport position, with the consequent likelihood of spillage when transporting fluent materials, from the front of the bucket. Also, because of the distance of the centre of gravity from the mast, when the bucket is loaded, there tends to be an unnecessarily excessive weight transfer away from the rear fork-lift wheels thus making the fork-lift possibly unstable and dangerous.

According to the present invention there is provided an attachment for a fork-lift device comprising an open load-carrying receptacle, a sub-frame adapted for support by the forks of the device, means for pivoting the receptacle with respect to the sub-frame about a linkage comprising a first fulcrum which is defined closely adjacent to the distal ends of the forks so as to tilt the receptacle forwardly from a rest position to an unloading position, and a second fulcrum towards the proximal ends of the forks so as to tilt the receptacle rearwardly from a rest, or loading, position to a load-carrying position without the receptacle passing below the level of the forks.

Preferably the linkage comprises a quadrilateral linkage wherein the first and second fulcra are defined by points at adjacent corners of the quadrilateral. The distance between the first and second fulcra is preferably fixed, while the distance between the remaining corners of the quadrilateral may be varied, during movement of the linkage.

The pivoting means is most preferably provided by a hydraulic ram located between the receptacle and the sub-frame, connecting the said remaining corners of the quadrilateral linkage.

The sub-frame advantageously comprises spaced apart rigid sleeve - or channel - section members, adapted to fit over the forks, with means to secure the sub-frame to the forks in use.

The first and second fulcra may be joined by a rigid connecting bar, adapted to lie over the sleeve - or channel - section members of the sub-frame when the receptacle is pivoted between the loading and unloading positions.

A fork-lift bucket attachment in accordance with a preferred embodiment of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a sketch of the attachment in use in a rest, or loading, position on a fork-lift truck, Figure 2 is a sketch of the attachment in use in a load-carrying position, Figure 3 is a sketch of the attachment in use in an unloading position, Figure 4 is a front elevation of the bucket attachment with one arch cover cut away and in partial cross-section, (when viewed on section line B-B of Figure 5), Figure 5 is a side elevation of the bucket attachment, when viewed on section line A-A of Figure 4, in a rest, or loading, position, Figure 6 is a side elevation of the bucket attachment, when viewed in the plane of section line A-A of Figure 4, in a rearwardly tilted, or load-carrying position, and, Figure 7 is a side elevation of the bucket attachment, when viewed in the plane of section line A-A of Figure 4, in a forwardly tilted, or unloading position.

Referring firstly to Figures 1 to 3 of the drawings, a bucket attachment 1 for a fork-lift truck 2 comprises a bucket 3 which may be mounted on a sub-frame 4 which may be supported by the forks 2a of the fork-lift truck 2. The sub-frame 4 is made from two sleeve or channelsections 5 which fit over the forks, joined by a cross-bar 6. The bucket 3 may be tilted from a rest, or loading, position (see Figure 1) either rearwardly to a load-carrying position (see Figure 2), or forwardly to an unloading position (see Figure 3) with respect to the sub-frame 4.

The tilting mechanism is provided by a pair of hydraulic rams 7, both connected to the hydraulic circuit of the fork-lift truck 2, and pivotally attached to upstanding mountings 8 fixed to the sleeve or channel sections 5 of the sub-frame 4 at the cylinder end of the ram, and pivotally attached at the piston end to the inside of a respective enclosed arch 9 forming an integral part of the bucket 3. The arches 9 are streamlined at their forward ends, which may protrude beyond the rim of the bucket, so as to minimise any obstruction of the material to be loaded in the bucket 3.The bucket attachment 1 may, for example, be quickly secured to the forks 2a of the fork-lift truck 2 by driving the truck with forks fully lowered towards the rear of the attachment, engaging the forks in the sleeve or channel sections 5 of the sub-frame 4, and then securing locating pins 10 at the rear of the sub-frame.

The fork-lift truck 2 may then be used for a variety of purposes, for example, for loading and unloading grain or other granular or fluent materials. The bucket 3 has a capacity of, for example, 50 cubic feet, which is equivalent to one ton of grain.

The tilting mechanism of the device will now be described in further detail with reference to Figures 4 to 7. The bucket 3 comprises a front wall 11, a base 12, a rear wall 13 and sides 14. The leading edge of the front wall 11 is strengthened by a wedge-shaped bar 15 in the conventional way, or may even include detachable teeth. The bucket 3 conceals, but is secured to, the tilting mechanism by means of the enclosed arches 9. The mounting 8 supports a pivot pin 16 which serves as a first point of pivotal attachment for the hydraulic ram 7, preferably at its cylinder end. The piston end of the ram 7 is pivotally attached to a pivot pin or bearing 17 mounted across the front end of the arch, near to the top of the arch.A third pivot pin or bearing 18 across the front of the arch, near to the bottom, is provided, which is linked to a fourth pivot pin 19 located across the mounting 8, near the bottom of the mounting 8, by means of a rigid connecting rod 20. Thus, there are only two points of pivotal attachment of the bucket 3 to the tilting mechanism, i.e. the pivot pins or bearings 17 and 18. It will be seen, however, that the pivots 16-19 define the corners of a quadrilateral linkage.

In the rest, or loading position as illustrated in Figure 5, the bucket 3 rests on the sub-frame 4 by means of stops provided by pads 21 held by angle irons 22 which are secured to the insides of the arches 9.

These pads rest on a cross bar 23 secured to the top of connecting rod 20 so that the front wall 11, which is the floor of the bucket in this position, does not drop below the level of the undersides of the sleeves 5. In this position, the piston of the hydraulic ram 5 is partially extended, but may still be completely housed within the space defined by the enclosed arch 9. The hydraulic ram 5, connecting rod 20, and sleeve sections 5 are all approximately parallel in this position. When the forks of the fork-lift truck have been lowered to ground level, the bucket may be driven forwardly so as to scoop up a load of material.

Once material has been loaded into the bucket 3, to prevent material spilling forwardly out of the bucket, it may be tilted rearwardly by the tilting mechanism to the load-carrying position, through an angle of 300 to 600, but generally approximately 450, most preferably 0 48 , as shown in Figure 6. The rearward tilting motion is brought about by fully retracting the piston of the hydraulic ram 5 so as to reduce the distance between the leading edge 26 of the bucket and the pivot pin 16 at the top of the mounting 8. During this movement the bucket rests on the stops 21,23 on the connecting rod 20 which itself tilts rearwardly through an arc about pivot pin 19 at the bottom of the mounting 8, which serves as the fulcrum for this movement. The rear wall 13 of the bucket comes to rest approximately perpendicular to the forks 2a.

In order to unload the material inside the bucket 3, the forks 2a are usually raised up the masts of the fork-lift truck as illustrated in Figure 3. The bucket 3 is then tilted forwardly with respect to the sub-frame 4, about bearing 18 which is the fulcrum for this movement, passing through the rest position shown in Figure 5, so as to arrive at a forwardly tilted, or unloading, position as shown in Figure 7. This is brought about by fully extending the piston of the hydraulic ram 5, such that when the rest position has been exceeded, the bushing of bearing 18 comes to rest on cam plates or front stops 25 which extend from the foremost ends of the sleeve sections 5. The rear end of the bucket 3 then moves forwardly through an are with bearing 18 providing the fulcrum.The leading edge 26 of the bucket is adapted to travel to a small extent around the front ends of the sleeve sections 5 as shown in Figure 7. Thus, the full length of the forks 2a is utilised to obtain "reach" during unloading.

In order to prevent grain or other material lodging on top of the sleeve sections 5, which might cause an obstruction to the bucket and the connecting rod 20 as it is lowered to a rest position (see Figure 5), the upper surfaces of the sleeve sections are preferably raised or convex. For instance, Figure 4 shows clearly how this may be achieved by using an angle iron 24 welded to the top of a box section 27. This has the desired effect of shedding grain or other material to each side of the forks and ensuring that no obstruction builds up. The connecting rod 20 must then accommodate the raised secLion of the sleeves 5 when the bucket is in a rest position, as shown in Figure 5 or, when in an unloading position, as shown in Figure 7.

In an alternative embodiment of the present invention, arches 9 may be dispensed with by locating connecting rods 20 beside the sleeve sections 5, and by locating either one or a pair of hydraulic rams 7 behind the bucket 3, with pivots 16 located on the sleeve sections 5, or on a rearward extension of the sub-frame 4, and pivots 17 located mid-way along rear surface 12 of the bucket 3. It would be necessary to place the bucket 3 more forwardly on the sub-frame 4 to give more space behind the bucket to accomodate the ram(s) 7 which would operate to tilt the bucket forwardly over the ends of the forks1 or rearwardly to a load-carrying position without falling below the forks, as described above, more in the manner of a conventional tipping truck.

Claims (9)

1. An attachment for a fork-lift device comprising an open loadcarrying receptacle a sub-frame adapted for support by the forks of the device, means for pivoting the receptacle with respect to the sub-frame about a linkage comprising a first fulcrum which is defined closely adjacent to the distal ends of the forks so as to tilt the receptacle forwardly from a rest position to an unloading position, and a second fulcrum towards the proximal ends of the forks so as to tilt the receptacle rearwardly from a rest1 or loading position to a loadcarrying position without the receptacle passing below the level of the forks.

2. An attachment as claimed in Claim 1 wherein the linkage comprises a quadrilateral linkage wherein the first and second fulcra are defined by points at adjacent corners of the quadrilateral.

3. An attachment as claimed in Claim 2 wherein the distance between the first and second fulcra is fixed, while the distance between the remaining corners of the quadrilateral may be varied, during movement of the linkage.

4. An attachment as claimed in Claim 3 wherein the pivoting means is provided by a hydraulic ram located between the receptacle and the sub frame connecting the said remaining corners of the quadrilateral linkage.

5. An attachment as claimed in any of Claims 1 to 4, wherein the sub-frame comprises spaced apart rigid sleeve- or channel-section members1 adapted to fit over the forks, with means to secure the sub-frame to the forks in use.

6. An attachment as claimed in Claim 5 wherein the first and second fulcra are joined by a rigid connecting bar adapted to lie over or beside the sleeve - or channel - section members of the sub-frame when the receptacle is pivoted between the loading and unloading positions.

7. An attachment as claimed in any one of the preceding claims wherein the receptacle is d bucket adapted to accomodate a linkage mechanism.

8. An attachment as claimed in any one of the preceding claims, wherein the receptacle is adapted to be tilted rearwardly from the rest position to the load-carrying position through an are subtending an angle of from 300 to 600.

9. A fork-lift bucket attachment, substantially as described herein with reference to and as shown in Figures 1 to 7 of the accompanying drawings.