GB2087838A - A lifting mechanism - Google Patents

Abstract

A lifting mechanism makes use of a pair of pivoted linkages (14). The linkages are of a type which can be actuated to increase the distance between two points (22,26). One of these points (22) will be fixed and the other (26) will be attached to a load (10), so that the load can be lifted by actuating the linkages. One of the points attached to the load will be constrained by a guide (38), so that it can only move in a substantially straight line. <IMAGE>

Description

SPECIFICATION A lifting mechanism Field of the invention This invention relates to a lifting mechanism for raising and lowering loads. In one particularapplica- tion, the mechanism can be used to raise and lower and to alterthe angle of inclination of a core barrel above a bed of a coring machine. However the invention can be applied in a large number of other diverse fields.

Summary of the invention According to the present invention, there is provided a lifting mechanism for raising and lowering a load relative to a base, the lifting mechanism comprising at least two pivoted linkages spaced from one another and supporting the load above the base, means for independently actuating the linkages, and guide means mounted at a point on the load to prevent movement of that point otherwise than in a substantially straight line.

Toggle linkages are frequently used to raise a load about a pivot axis. In this case the linkage is spaced from the pivot axis, and the existence of a fixed pivot axis prevents instability of the load. Toggle linkages are used because they allow extremely high forces to be applied. However in situations where it is necessary to raise or lower both ends of a load, with there being no direct connection between the load and the base above which it is being raised, toggle linkages cannot normally be used because the raised load will be unstable, there being no constraint on those links of the toggle linkage to which the actuating force is not applied.

With the guide means of the present invention where the pivoted linkages are a form of toggle linkage, this disadvantage is overcome and a pair of spaced linkages can be used to raise a load.

Preferably the guide means is a wheel mounted for free rotation of the axis of a pivot pin between the linkage and the load. The wheel can run between spaced vertical guide plates.

Brief description of the drawing The invention will now be further described, by way of example, with reference to the accompanying drawing, in which: Figure 1 is a side view of a lifting mechanism according to the invention; Figure2 is a perspective view of one end only of the mechanism shown in Figure 1; and Figure 3 is a perspective exploded view of another mechanism in accordance with the invention.

Description ofa preferred embodiment In Figure la a load 10 is supported above a base 12.

The load 10 is only shown schematically but could take any form. Thus any type of apparatus or any load of goods could be supported at 10.

At each end between the load 10 and the base 12, a tandem linkage 14 is provided. The linkages 14 are the same and are arranged back-to-back. The linkage shown on the left-hand side in Figure 1 however is provided with a guide, and the linkage and the guide will be described in more detail with reference to Figure 2.

Each side of the linkage 14 has a lower link 16 and an upper link 18. The links 16 and 18 are pivotally connected to one another by pins 20. The bottom end of the lower link 16 is pivoted at 22 to a bracket 24 fixed to the base 12. The upper link 18 is pivoted at 26 to a beam 28 which supports the load 10.

The two sides of the tandem linkage 14 are connected by means of a torsion bar 30. This bar is fixed to both lower links 16 and to actuatipg links 32.

Hydraulic jacks 34 are connected to the actuating links 32 so that when the pistons of the jacks 34 are extended, the links 16 are raised. As already mentioned, the linkage 14 shown in Figure 2 includes a guide. The guide comprises a roller 36 which is mounted for free rotation on the pivot 26, and a pair of fixed guide rails 38. The guide rails 38 are fixed to a base 12 or to any part which is stationary relative to the base 12.

As the linkage 14 is extended, the pivot point 26 is therefore constrained to move in a vertical path.

In use, both linkages can be extended by the same amount as shown in Figure 1 to raise the load 10 to a position above and parallel to the base 12. However by extending the pistons of the jacks 34 by different amounts at the two linkages, the positions of the load 10 can be infinitely varied in angle of inclination. For example, one inclined position of the load 10 is shown in dotted lines in Figure 1.

Without the guide 36,38 there would be no constraint on the upper links 18, and therefore the load 10 would be unstable when supported only by two spaced linkages.

Figure 3 shows a mechanism in accordance with the invention applied to a coring machine. The machine has a bed 40 arranged between housings 42 for the tracks on which the machine moves. The lifting mechanism to be applied to this machine is very similar to that shown in Figures 1 and 2, and the same reference numerals will be used for corresponding parts. Note however that in Figure 3, for the sake of clarity, the actual pivot axle between the various parts are not shown.

In Figure 3, the fixed guide rails 38 are secured to the track housings 42 on either side of the bed 40 which performs the same function as the bed 12 shown in Figures 1 and 2. Rollers 36 are mounted for rotation at the tops ofthe links 18, to run in the guides 38.

Figure 3 shows clearly the lower link units 16,30, 32. These units shown in Figure 3 have an additional member to the corresponding units shown in Figures 1 and 2, viz. a bar 31 which assists in preventing relative rotation between the links 16 and 32. These units 16,30,31,32 which are shown on their own in Figure 3 form a rigid construction which is mounted for rotation at each end in bearing blocks 44.

The cylinder ends of the piston/cylinder units 34 are supported in bearing blocks 46. Bearing plates 48 are mounted at the top ends of links 18, to support a load 10 which in the case of Figure 3 will be a coring barrel.

Claims (8)

1. A lifting mechanism for raising and lowering a load relative to a base, the lifting mechanism comprising at least two pivoted linkages spaced from one another and supporting the load above the base, means for independently actuating the linkages, and guide means mounted at a point on the load to prevent movement of that point otherwise than in a substantially straight line.

2. A mechanism as claimed in Claim 1,wherein the guide means includes a wheel mounted for free rotation on the axis of a pivot pin between the linkage and the load, and fixed spaced vertical guide plates between which the wheel is arranged to run.

3. A mechanism as claimed in Claim 1 or Claim 2, wherein each linkage has two links pivoted to each other, the opposite end of one of the links being pivioted on the base and the opposite end of the other of the links being pivoted on the load.

4. A mechanism as claimed in Claim 3, wherein the actuating means is arranged to turn an axle by means of which said other of the links is pivoted on the base, the axle and said other of the links being rigidly connected to one another.

5. A mechanism as claimed in any preceding claim, wherein the actuating means comprises hydraulic piston/cylinder units.

6. A mechanism as claimed in any preceding claim, wherein four pivoted linkages arranged in pairs are provided, the linkages of each pair having common pivot axes, and one pair of linkages being spaced from the other pair.

7. A coring machine having a lifting mechanism as claimed in any preceding claim arranged between the machine bed and the core barrel.

8. A lifting mechanism substantially as herein described with reference to Figures 1 and 2 or Figure 3 of the accompanying drawings.