GB2090225A - Improvements relating to lifting devices - Google Patents

Abstract

A lifting device attached to the three-point linkage of a tractor comprises a rod 2 pivotally connected to the upper connector 10 and a triangular frame 1 formed by a pair of arms 3 whose ends 6 are joined to the lower linkage rods 7. The other ends of the arms 3 are joined to a bracket 4 which can be positioned at a desired point along a T-piece 15. When the tractor rams 18 are operated to raise the linkage rods 7 the rod 2 will be caused to rise thus lifting any load attached to a hook 14. An arm 11 carrying the hook is telescopically engaged at a desired position within the rod 2. <IMAGE>

Description

SPECIFICATION Improvements relating to lifting devices This invention relates to lifting devices which may be used by farmers to lift heavy loads. A farmer may often need to lift loads such as sacks and bales and structures can be applied to the front of a tractor which can be raised by the existing hydraulic equipment to lift loads from the ground. Such structures are however relatively large and expensive.

According to the present invention there is provided a lifting device for a tractor comprising a lifting arm and interconnecting parts enabling the device to be connected to a standard tractor three-point linkage such that the lifting arm can be raised and lowered as the hydraulic rams connected to the lower linkage rods of the tractor three-point linkage are operated.

This lifting device therefore employs the standard equipment already present and provided for the tractor three-point linkage and provides means whereby loads may be lifted simply and effectively.

In a more detailed aspect of the invention, the lifting arm can comprise a rod having a carrying member at one end, a pivotal connecting point at the other end for attachment to the upper connector of the tractor three-point linkage, and a pivotal interconnection member at an intermediate position connecting with the one ends of a pair of arms, the other ends of the arms having pivotal connecting points for attachment to the pair of lower linkage rods of the three-point linkage of the tractor.

Such a device may readily be interconnected with the three-point linkage of a tractor and the hydraulic rams operating on the lower linkage rods will be used to alter the attitude of the rod of the lifting device so that any load attached to the carrying member will be raised or lowered.

Ideally the other ends of the two arms will be interconnected by a tie-bar to form a triangle and thus prevent the tendency for the arms to spread, which could damage the lower linkage rods. Also the one ends of the two arms are desirably interconnected at or near their ends. Adjustable interconnection of the rod with the two arms may readily be achieved by attachment of the one ends of the two arms in relation to one of an array of holes provided along the length of the rod. It is also preferred that the carrying member should be mounted on an arm which is adjustably telescopically supported by the one end of the rod.

Advantageously, the free end of the rod may incorporate a cross-piece generally forming an L-shape or a T-shape. This cross-piece can be made to be movable between a variety of fixed positions with respect to the main part of the rod to provide for flexible lifting ability. If desired also the crosspiece could be pivotally connected to the end of the main part of the rod and the lifting device could further include a ram interconnected between intermediate portions of the cross-piece and the main part of the rod, to enable two stage lifting to be performed.

The invention also extends to the combination of a tractor with the lifting device of this invention hereinbefore defined attached to the three-point linkage.

The invention may be performed in various ways and preferred embodiments thereof will now be described with reference to the accompanying drawings, in which: Figure 1 is a side view of a lifting device of this invention and the essential parts of a three-point linkage of a tractor; Figure 2 is a perspective view of another form of lifting device of this invention; Figure 3 is an end view of parts of the lifting device shown in Figure 2; and Figure 4 illustrates a modification to part of the lifting device shown in Figure 1 or Figure 2.

The lifting device shown in Figure 1 and the generally similar arrangements of Figures 2 and 3 essentially comprise a triangular frame 1 (similar to that of Figure 2) and a rod 2. The triangular frame is formed by a pair of arms 3 whose upper ends are joined together and welded to a piece of channel section 4. The lower ends of the arms 3 are welded to a tie-bar 5 from whose ends project pins 6 which will pass through the holes in the ends of the lower linkage rods 7 of a tractor threepoint linkage. The rod 2 is formed from a box section and at one end has a pivoting member 8 provided with a hole through which will pass a pin which also passes through one of the holes 9 in the upper connector 10 of the three-point linkage.

The other end of the rod 2 has an L-shaped arm 11 telescopically received therein. This arm 11 is provided with a number of holes 12 which will receive a pin also passing through a hole 13 in the rod 2 so that the effective length of the arm 2 in combination with the arm 11 may be varied. The arm 11 carries a lifting hook 14. Welded below the arm 2 is a piece of T-section 15 provided with a series of holes 1 6. The channel section 4 is also provided with a pair of holes 1 7 which may be aligned with any one of the holes 1 6 and be attached thereto by a pin so as to interconnect the frame 1 with the arm 2.

When the hydraulic rams 1 8 associated with the lower linkage rods 7 are actuated this will cause the arm 2 to be raised or lowered so that any load carried by the hook 14 will also be lifted or lowered. The height to which any load may be raised may be modified by repositioning the channel section 4 with respect to the array of holes 16, and altering the degree of insertion of the telescopic arm part 11 into the rod 2.

In the arrangement shown in Figures 2 and 3 the main features are essentially identical to those shown in Figure 1. The basically triangular frame 1 is of slightly modified construction in that it incorporates a connecting piece 1 9 joining the upper ends of the two arms 3 which between them leave a small gap to receive the T-section piece 1 5. An additional strengthening bar 20 is also shown. The pivoting member 8 is held within the rod 2 by means of a pin passing through aligned holes 21. At the other end of the rod 2 an L-shaped member 22 is telescopically received within the rod and can be mounted at any one of the three alternative positions indicated by the holes 12 and 13.The end of the L-shaped member 23 is hollow and receives a bar 23 which incorporates three holes 24 which can be aligned with a hole 25 thus adjusting the position of the bar 23 relative to the L-shaped member 22. A hole 26 provides a mounting for a hook or shackle.

Another modification is illustrated in Figure 4 where the rod 2 is provided with an extension piece 27 which is pivotally connected thereto by a pivot pin 28. A ram 29 acts between the rod 2 and the extension piece 27 to control the relative positions of these two parts. The hole 30 in a plate 31 provides a mounting for a hook or shackle. The provision of the ram acting on the pivot mounted extension piece 27 allows for a two-stage lifting of loads, Thus initially the arm 2 is raised by the three-point linkage of the tractor and subsequently the ram 29 is operated to cause the extension piece 27 to swing upwardly. This arrangement enables the arm 2 to be of a shorter length than for the arrangement shown in Figure 2, whilst still providing for the same ultimate lifting height.

Shortening of the arm reduces the cantilever effect during the initial stage of lifting of the rod.

Claims (11)

1. A lifting device for a tractor comprising a lifting arm and interconnecting parts enabling the device to be connected to a standard tractor three-point linkage such that the lifting arm can be raised and lowered as the hydraulic rams connected to the lower linkage rods of the tractor three-point linkage are operated.

2. A lifting device according to claim 1, wherein the lifting arm comprises a rod having a carrying member at one end, a pivotal connecting point at the other end for attachment to the upper connector of the tractor three-point linkage, and a pivotal interconnection member at an intermediate position connecting with the one ends of the pair of arms, the other ends of the arms having pivotal connecting points for attachment to the pair of lower linkage rods of the three-point linkage of the tractor.

3. A lifting device according to claim 2, wherein the other ends of the two arms are interconnected by a tie-bar to form a triangle.

4. A lifting device according to claim 2 or claim 3, wherein the one ends of the two arms are interconnected at or near the ends.

5. A lifting device according to any one of claims 2 to 4, wherein the carrying member is mounted on an arm which is adjustably telescopically supported by the one end of the rod.

6. A lifting device according to any one of claims 2 to 5, wherein an adjustable interconnection of the rod with the two arms is achieved by attachment of the ends of the two arms in relation to one of an array of holes provided along the length of the rod.

7. A lifting device according to any one of claims 2 to 6, wherein the free end of the rod incorporates a cross-piece generally forming an L-shape or a T-shape.

8. A lifting device according to claim 7, wherein the cross-piece is movable between a variety of fixed positions with respect to the main part of the rod.

9. A lifting device according to claim 7, wherein the cross-piece is pivotally connected to the end of the main part of the rod and a ram is interconnected between intermediate portions of the cross-piece and the main part of the rod.

1 0. A lifting device for a tractor substantially as herein described with reference to the accompanying drawings.

11. The combination of a tractor with a lifting device as claimed in any one of claims 1 to 10 attached to the three-point linkage of the tractor.