GB2024141A

GB2024141A - Adjustable torsion bar counterbalancing

Info

Publication number: GB2024141A
Application number: GB7920498A
Authority: GB
Original assignee: Ratcliff Tail Lifts Ltd
Current assignee: Ratcliff Tail Lifts Ltd
Priority date: 1978-06-26
Filing date: 1979-06-13
Publication date: 1980-01-09
Also published as: GB2024141B

Abstract

The object of the invention is to provide an adjustable counterbalancing assembly for load lifting and lowering apparatus of the type comprising a pair of parallel spaced apart, upright, rigid guide members and a platform pivotally mounted on a pair of runners each movable up and down an associated guide member. The counterbalancing assembly comprises a first torsion bar locating block (16) secured to part of a runner to prevent rotation of a torsion bar (21) relative to the runner and a second torsion bar locating block (22) slidable on the torsion bar (21) and positionable in one of several positions axially along the torsion bar (21) by engagement of the second block (22) with a castellated bar (23) secured to the platform (10) for preventing rotation of the torsion bar (21) relative to the platform (10). By moving the second block (22) to a position closer to the first block (16) a greater counterbalancing effect is achieved. <IMAGE>

Description

SPECIFICATION Improvements in or relating to load lifting and lowering apparatus The invention relates to load lifting and lowering apparatus of the kind comprising a pair of parallel, upright, rigid spaced apart guide members and a load carrier pivotally mounted on a pair of spaced apart runners, each runner being movable up and down an associated one of the guide members to raise and lower the load carrier. The load carrier is rotatable between a load carrying position and an upright stowed position. Such apparatus is well known and will hereinafter be referred to as "load lifting and lowering apparatus of the kind described". More particularly but not exclusively the invention relates to load lifting and lowering apparatus of the kind described for use in a vehicle.

According to the invention there is provided load lifting and lowering apparatus of the kind described comprising adjustable counterbalancing means for biasing the load carrier towards an upright position, the adjustable counterbalancing means comprising one or more torsion bars extending substantially parallel to the axis of rotation of the load carrier, first locating means fixed relative to the runners for locating the or each torsion bar to prevent relative rotation of the or each torsion bar relative to the runners, second locating means spaced apart from the first locating means and fixed relative to the load carrier for locating the or each torsion bar to prevent relative rotation of the or each torsion bar relative to the load carrier, and means to vary the spacing between the first and second locating means to adjust the biasing force applied to the load carrier.

The second locating means preferably comprises block means slidable on the or each torsion bar and mountable on block carrier means secured to the load carrier in one of a plurality of discrete positions axially along the or each torsion bar.

The block carrier means preferably comprises a castellated bar extending substantially parallel to the or each torsion bar, the slidable block means comprising lug means engageable with castellations of the castellated bar such that the slidable block means is positionable in a plurality of discrete positions on the castellated bar.

The first locating means preferably comprises block means secured to one of the runners having holes engageable by one end of the or each torsion bar.

Stop means are preferably provided to prevent the torsion bar or bars sliding out of engagement with the locating means. The torsion bar or bars may be of square cross section.

By way of example, one embodiment of load lifting and lowering apparatus according to the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a sectional view from the rear of part of a load lifting and lowering apparatus with the load carrier in a vertical position; Figure 2 is a sectional view on the line ll-ll of Figure 1; and Figure 3 is a sectional view along the line Ill-Ill of Figure 1.

Load lifting and lowering apparatus comprises a pair of upright, parallel spaced apart rigid guide members (not shown), a pair of runners each being movable up and down an associated guide member and a platform 10 pivotally mounted on the two runners. Each runner has two parallel flanges 11,12 through which a hinge pin 13 passes, the hinge pin being retained in position relative to the flanges 11, 12 by a spring pin 14. A platform support member 15 is pivotally mounted on the hinge pin 13 for rotation about the associated runner, the platform support member 15 being secured to the platform 10.

A torsion bar locating block 16 is secured to the runnerflange 12 via an intermediate ring 17. As shown in Figure 2 the block 16 is formed with three square holes 18,19,20 each suitable for locating an end of a torsion bar of square cross section to prevent rotation of that end of the torsion bar relative to the runner. The sides of the holes are angled at 20 to the vertical or horizontal respectively.

Located in the hole 18 is one end of a torsion bar 21 6f square cross section, the torsion bar 21 extending substantially parallel to the axis of rotation of the platform about the runners. A second torsion bar block 22 is slidable on the torsion bar 21 and axially located by engagement with one of a plurality of castellations of a castellated bar 23 which is secured to a platform cross member 24 by welding. The block 22 is formed with three holes 25, 26,27 of square cross section, and as shown in Figure 3, with the platform 3 in a vertical position, the sides of the holes 25,26,27 are horizontal or vertical respectively. The block 22 engages a castellation in the castellated bar 23 by means of a lug 28 formed by cutting away part of the block 22.The block 22 prevents the part of the torsion bar 21 extending from the block 22 away from the block 16 from rotating relative to the platform 10, To prevent the torsion bar 21 or other torsion bars if present, from sliding out of engagement with the blocks 16 and 22, a stop member in the form of an angle iron 29 is secured to the castellated bar 23. It will be appreciated that for torsion bars of different length to that shown in Figure 1, the stop member 29 will be positioned differently on the castellated bar 23. It will also be appreciated that more than three torsion bars may be used if further holes are provided on the torsion bar blocks 16 and 22.

The platform 10 in Figure 1 is shown in a vertical closed position, in which the platform 10 lies parallel to the guide members (not shown). It will be appreciated that, due to the holes of the block being angularly offset relative to the holes of the block 22, the torsion bar 21 exerts a moment on the platform urging the platform towards the guide members. As the platform is rotated away from the guide members towards a horizontal position, the moment exerted by the torsion bar 21 increases.

The counterbalancing moment exerted by the torsion bar or bars may be adjusted by movement of the block 22 to engage a different castellation of the castellated bar 23. The arrangement is such that the closer the block 22 is to the block 16, the shorter the effective length of the or each torsion bar, and the greater the counterbalancing moment exerted by the torsion bar or bars at a given angular position of the platform.

It will be appreciated that the number of castellations of the castellated bar may be varied, but a preferred number of castellations is ten.

Claims

1. Load lifting and lowering apparatus ofthe kind described comprising adjustable counterbalancing means for biasing the load carrier towards an upright position, the adjustable counterbalancing means comprising one or more torsion bars extending substantially parallel to the axis of rotation of the load carrier, first locating means fixed relative to the runners for locating the or each torsion bar to prevent relative rotation of the or each torsion bar relative to the runners, second locating means spaced apart from the first locating means and fixed relative to the load carrier for locating the or each torsion bar to prevent relative rotation of the or each torsion bar relative to the load carrier, and means to vary the spacing between the first and second locating means to adjust the biasing force applied to the load carrier.

2. Load lifting and lowering apparatus as claimed in claim 1 wherein the second locating means comprises block means slidable on the or each torsion bar and mountable on block carrier means secured to the load carrier in one of a plurality of discrete positions axially along the or each torsion bar.

3. Load lifting and lowering apparatus as claimed in claim 2 in which the block carrier means comprises a castellated bar extending substantially parallel to the or each torsion bar, the slidable block means comprising lug means engageable with castellations of the castellated bar such that the slidable block means is positionable in a plurality of discrete positions on the castellated bar.

4. Load lifting and lowering apparatus as claimed in any preceding claim in which the first locating means comprises block means secured to one ofthe runners having holes engageable by one end of the or each torsion bar.

5. Load lifting and lowering apparatus as claimed in any preceding claim comprising stop means for preventing the or each torsion bar from sliding out of engagement with the locating means.

6. Load lifting and lowering apparatus as claimed in any preceding claim in which the or each torsion bar is of square cross section.

7. Load lifting and lowering apparatus substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

8. A vehicle comprising load lifting and lowering apparatus as claimed in any preceding claim.