WO1987006202A1

WO1987006202A1 - Jacking system

Info

Publication number: WO1987006202A1
Application number: PCT/GB1987/000232
Authority: WO
Inventors: William Nevil Heaton Johnson
Original assignee: Gunnar Limited
Priority date: 1986-04-17
Filing date: 1987-04-02
Publication date: 1987-10-22
Also published as: AU7209087A; GB8609436D0

Abstract

A jacking system for supporting the front end of the trailer of an articulated truck when uncoupled from a tractor unit comprises an externally screw-threaded inner jack member (16) and nut segments (18), capable of cooperating with the screw thread on member (16). The nut segments (18) are mounted on a tubular outer member (14) mounted on the underside of the trailer bed (10) for rotation about a vertical axis by means of a handle (44). The nut segments (18) are movable on member (14) between operative positions in which they engage the screw thread on member (16), to inoperative positions in which they do not. When the trailer is coupled to a tractor unit, the member (16) is held in a raised position. When it is desired to uncouple the trailer unit, the segments (18) are moved to their inoperative positions and the member (16) is allowed to drop onto the road surface. The nut segments are then re-engaged with the member (16) and the member (14) rotated by the handle (44) to jack up the front end of the trailer. When the trailer is to be coupled up to a tractor unit again, these operations are reversed, rapid raising of the member (16) being achieved by a cable (20) and winch (24).

Description

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Title: "Jacking system"

THIS INVENTION relates to a jacking system and particularly, but not ex¬ clusively to a trailer jacking system for supporting, when uncoupled from a tractor unit, a truck trailer of the kind comprising a body having road wheels towards the rear end thereof and which, in use, is detachably coupled at its 5 front end to a coupling and supporting arrangement at the back of a tractor unit, for pivoting about a vertical axis relative to the tractor unit to form a so- called "articulated truck". Such a trailer is herein referred to, for convenience, as being "of the kind specified".

10 When it is desired to uncouple a trailer of the kind specified from a tractor unit, conventionally, supporting legs adjacent the front end of the trailer are extended to engage the ground or road surface to support the front end of the trailer, whereafter the trailer is uncoupled from the tractor unit and the latter is driven away from the trailer. The reverse procedure is followed

15 when it is desired to couple up a tractor unit to a trailer of the kind specified to tow the trailer away. It is of course desirable that the operation of raising and lowering the supporting legs should be capable of being carried out quickly and easily by one man (normally the driver of the tractor unit). Usually, the supporting legs are lowered and raised by a mechanical jacking arrangement

20 requiring the operator to turn a winding crank in order to raise or lower the supporting legs and this operation is arduous and time consuming. There have been proposed supporting leg systems which are hydraulically operated and coupled with the trailer's braking system but such systems are complex and expensive in construction.

25

It is an object of the present invention to provide an improved jacking system.

According to one aspect of the invention, there is provided a jacking 30 system including a jack having a first member mounted for movement towards aπd away from a second member and means for moving said first member relative to said second member with a relatively high velocity ratio and a relatively low mechanical advantage in relation to an actuating means, and means for moving said first member relative to said second member with a relatively low velocity ratio and a relatively high mechanical advantage in relation to an actuating means.

According to another aspect of the invention there is provided a trailer jacking system for supporting, when uncoupled from a tractor unit, a truck trailer of the kind specified and including at least one jack according to the first-noted aspect of the invention.

An embodiment of the invention is described below by way of example with reference to the accompanying drawings in which:-

FIGURE 1 is a diagrammatic side view, partly in vertical section, showing a trailer jacking system embodying the invention, and

FIGURE 2 is a schematic plan view showing part of the system of Figure 1.

Referring to the drawings, a trailer of the kind specified has a chassis, indicated only in part at 10, to the underside of which a jacking system embodying the invention is secured adjacent the front end of the trailer. The jacking system illustrated incorporates a fixed housing 12, an outer tubular member 14 extending vertically downwardly from the housing 12 and rotatable therein about a vertical axis and an inner member 16 fitted closely within the tubular member 14 and provided on its outer surface with a screw thread. The tubular member 14 is substantially smooth internally, so that when nut segments 18, described in greater detail below, are withdrawn radially from the member 16, the latter is free to slide vertically in the tubular member 14.

The nut segments 18, as illustrated in Figure 2, have each a surface 28 extending over part of the arc of a circle about a vertical axis and which is formed with the corresponding part of an internal screw thread complementary with that on the exterior of the member 16. Each nut segment 18 is mounted at the lower end of member 14 for movement in a horizontal plane towards and away from the surface of member 16 but is restrained against vertical movement relative to the member 14 and is constrained, when the member 14 is rotated relative to the housing 12 and member 16, to rotate with the member 14. In the arrangement shown in Figure 2, the two nut segments 18 are of arcuate form and each is pivoted, at one end, on a vertical pivot pin 30 fixed in a bracket 32 integral with the lower end of the sleeve 14. The nut segments 18 may thus be swung horizontally, in directions indicated by arrows 34, towards and away from the member 16.

With the nut segments 18 withdrawn from member 16, the member 16 can be raised and lowered rapidly relative to the tubular member 14 by means of any suitable manual actuating arrangement, which, since only the weight of member 16 requires to be lowered or raised, does not have to provide any substantial mechanical advantage and may thus have a relatively high velocity ratio. In Figure 1, this actuating arrangement is represented by a simple cable 20 which is connected at one end to the upper end of member 16, passes upwardly within the tubular member 14, over a pulley 22 and thence to a relatively large-diameter drum 24 rotatable, in a bracket secured to chassis 10, by means of a winding handle 26.

Assuming the member 16 to be initially fully raised relative to the member 14, with the nut segments 18 in their inner positions engaging the screw thread on member 16, so that the jack is raised and inoperative, the jack is deployed as follows. The nuts segments 18 are moved to their outer positions, away from the member 16 and the member 16 is lowered by means of the actuating arrangement 20, 22, 24, 26 until the base plate 17 secured to the lower end of the member 16 engages the road surface. The nut segments 18 are then swung inwardly, about pivot pin 30, to bring their screw-threaded surfaces into engagement with the screw thread on member 16 and are fixed in their inner positions. The member 14 is then rotated about its vertical axis relative to housing 12 and member 16, by means of a further actuating arrangement, for example by means of a worm 40 and gear 42 operated by means of a second actuating handle 44. The nut segments 18 effectively form a terminal screw threaded part of the member 14 which, due to its rotation, is screwed progressively up the screw thread on the member 16, to raise the chassis 10 and support the front part of the trailer, whereafter the tractor unit can be uncoupled from the trailer and driven away. When the trailer has been coupled to a tractor unit once more and it is desired to raise the jack, the handle 44 is again operated to screw the member 14 and nut segments 18 down the screw thread on member 16 until the load on member 16 is relieved, whereupon the nut segments 18 are swung into their outer positions, clear of the screw thread on member 16 and member 16 raised by means of the drum 24 and handle 26 to Its raised position, whereupon the nut segments 18 are moved to their inner positions once more to hold the member 16 in its raised position.

The nut segments 18 have upper surfaces which bear upon lower faces of the member 14 during jacking, thereby transmitting the vertical forces exerted on the nut segments directly to the member 14.

The mechanism used for opening and closing the nut segments preferably comprises an appropriate toggle arrangement, indicated schematically at 48 in

Figure 2, and which is operable readily manually and yet ensures that, when appropriate, the nut segments 18 are held reliably in their closed or their opened positions as the case may be.

It will be appreciated that the high velocity ratio actuating system 20,

22, 24, 26 and the high mechanical advantage actuating system 44, 40, 42 may each be replaced by appropriate equivalents. Thus, for example, the system 20, 22, 24, 26 might be replaced by a simple lever system whereas the system 40, 42, 44, 14 might be replaced by a hydraulic jack arrangement with the nut segments 18 being replaced by simple mechanically actuated dogs or the like.

Claims

1. A jacking system including a jack having a first member mounted for movement towards and away from a second member and means for moving said first member relative to said second member with a relatively high velocity ratio and a relatively low mechanical advantage in relation to an actuating means, and means for moving said first member relative to said second member with a relatively low velocity ratio and a relatively high mechanical advantage in relation to an actuating means.

2. A trailer jacking system for supporting , when uncoupled from a tractor unit, a truck trailer of the kind specified, and including at least one jack according to claim 1.

3. A jacking system substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.