GB2204024A - Lifting legs - Google Patents

Abstract

A lifting leg (10) for use in raising and lowering large loads, such as mobile offices and freight containers comprises a first leg portion (11) to be supported by the ground, a second leg portion (12) which is telescopically slidable relative to the first leg portion (11), a lift hitch (13) secured to the second leg portion (12) and projecting laterally therefrom, and a reaction hitch (14) secured to the first leg portion (11) and projecting laterally therefrom. A lever-operated ratchet device (17) controlled by a lever (18) can be operated in either direction, in order to lengthen or shorten a length of chain between its hooked ends (16) which are attached to respective ones of the hitches (13, 14). A slot (19) is formed in the wall of the outer tubular leg portion (12), and the hitch (14) provided on the inner first leg (11) extends through the slot and is movable relatively along the slot during relative movement of the leg portions (11, 12) during raising and lowering operations. A pin (20) can be used to lock the leg portions in any required position, and a shear pin (21) can be used to arrest downward movement of leg portion (12) in the event of failure of the ratchet device. <IMAGE>

Description

LIFTING LEGS This invention relates to lifting legs for use in raising and lowering large load-s of high inertia, such as mobile offices and cabins, and freight containers.

It is well known that jack legs are used to facilitate the loading and unloading of cabins and containers with respect to a loading platform, and also in the case of cabins to be used in the tempo-rary installation on site, and subsequent uplifting for transport to store or to a further site.

Jack legs are usually positioned one at each corner of the load to be raised or lowered, and are securely anchored by any suitable means to strong points at the upper and lower ends of the load at each corner.

Each leg comprises a telescopic arrangement of tubes, a lower one of which is supported by the ground and the upper one of which is raised, by a suitable powered device, relative to the lower tube.

One powered device which is used to raise the upper tube comprises a so-called "bottle jack", which is operated so as to lift the movable tube of each leg through relatively short increments. However, at the end of each increment of movement, it is necessary to insert a loading pin to hold the tubes in their new position of adjustment, and then to lower the bottle jack and insert a platform below it, before a further increment of lifting can take place. This is necessarily a time consuming and tedious process, bearing in -mind that this has to be carried out on each leg and, if only one bottle jack is available, it will be necessary to carry out these short increments in a cycle around the legs.

-This known system is very slow, taking about 45 minutes to lift a cabin t'nrough about 5 foot, after considerable effort with a bottle jack (and lowering is also a tedious and lengthy task), but in addition it is prudent for the task to be given to an experienced operator only.

There are also known complicated constructions of jack leg which have built-in lifting systems, but these are expansive to purchase, and are normally permanently attached to the sides of cabins, so that they represent a considerable proportion of under-utilised capital for most of their working life. Furthermore, on site the complicated internal workings of the lifting mechanism are exposed to all adverse weather conditions prevailing, and therefore deteriorate while out of use.

There is therefore a clear need to provide a construction of leg which is reliable,. and which can be operated more readily than the existing arrangements using bottle jacks, but in such a way that the component parts of the leg which remain in use for extended periods to support a load can be obtained more cheaply than jack leg constructions with built-in lifting mechanisms.

According to the invention there is provided a lifting leg for use in raising and.lowering a large.load when attached thereto, in which the leg comprises: a first leg portion which is positionable so as to be supported by the ground; a second leg portion slidable relative to the first leg portion and having means for attaching the second leg portion to anchor points provided on the load, the second leg portion being movable along the first leg portion in order to raise or lower the load; a lift hitch secured to the second leg portion and projecting laterally therefrom; and, a reaction hitch secured to the first leg portion and projecting laterally therefrom, a manually operable tensile device being attachable at each end to a respective one of said hitches and being operable to raise or lower the lifting hitch relative to the reaction hitch; in which: the fir.st and second leg portions form a telescopic assembly having an inner. leg portion and an outer tubular leg portion; and, a slot is formed in the outer tubular leg portion and the hitch provided on the inner leg portion extends through said slot and is movable relatively-along the slot during relative movement of the leg portions during raising and lowering operations.

The manually operated tensile lifting device which is attachable at each end to the lifting hitch and the reaction hitch may take any suitable form, and conveniently comprises-a ratchet-operated lifting chain. A suitably long lever arm may be coupled with the ratchet device, to permit relatively easy operation by a single operative, in -order to exert-the necessary lifting action on the second leg portion, the-reby to lift the corresponding corner of the load. to which it is attached.

The manually operated tensile lifting device is aseparate component which is attached to each lifting leg which requires raising .or lowering, and which can then be removed for use with further le.gs. Therefore, the lifting device does not form part of the capital cost of thelifting legs, neither is it required to remain on site on a particular leg when the latter is carrying out its normal supporting function.

Preferably, the first leg portion comprises the inner leg portion dnd the second leg portion comprises the outer tubular leg portion, in which case the slot is formed in the wall of the second leg portion and the hitch whichextends through the slot comprises the reaction hitch. However, it is within the scope of the invention for the first leg portion to comprise the outer tubular leg portion and for the second leg portion to comprise the inner leg portion, in which case the slot is formed in the wall of the first leg portion, and the hitch which extends through the slot comprises the lifting hitch.

Conveniently, both leg portions of each leg is tubular in construction, and preferably of square or rectangular cross-section.

A supporting foot may be provided on the lower end of the first leg portion, to spread the bearing pressure on the ground.

While the manually operated tensile lifting device will be of robust construction, and designed to have a breaking load considerably in excess of the maximum envisaged load which will be borne by each leg, it may be desirable to provide a safety pin arrangement which can restrain downward movement of the second leg portion in the event of failure of the tensile lifting device. The safety pin arrangement may comprise a sturdy shear pin which can be entered through a selected one of a series of vertically spaced aligned holes in the first leg portion, and in the path of downward movement of the second leg portion, so as to arrest downward movement of the latter in the event of failure of the tensile lifting device.

One embodiment of lifting leg according to the invention will now be described in detail, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is an end view of a lifting leg in accordance with the invention, with the leg portions thereof in a lowered and retracted position; Figure 2 is an end view, similar to Figure 1, but showing the leg portions in an extended and load-supporti-ng position; Figure 3 is a side view of the lifting leg in the lowered position; Figure 4 is a side view of the leg portions in an extended position; Figure 5 is a side view of a manua-lly operable tensile lifting device for use in raising and lower the leg portions of the lifting leg; Figure 6 is a diagramatic illustration of a lifting opera.tion on a lifting leg according to the invention;; Figure 7 is a diagrammatic view of a further stage in the lifting operation; and, Figure 8 is a diagramatic illustration of a final stage of the lifting operation.

Referring now to the drawings, a lifting leg according to the invention is designated generally by reference 10 and is intended for use in raising and lower large-loads, such as mobile offices and cabins, and freight containers.

The leg I0 can be attached to suitable anchor or strong points on the side of the load in any of the known techniques-.

The leg 10 comprises a first leg portion 11 which will be positioned to be supported by the ground, and a second leg portion 12 which is slidable relative to the first leg portion 11 and which has means (not shown) for attaching the second leg portion to anchor points provided on the load. The second leg portion 12 is movable along the length of the first leg portion 11 in order to raise-or lower the load.

A lift hitch 13 is secured to the second leg portion 12 and projects laterally therefrom, and a reaction hitch 14 is secured to the first leg portion 11 and projects laterally therefrom. A manually operable tensiledevice, as shown generally by reference numeral 15 in Figure 5, can be attached at each of its hooked ends 16 to a respective one of the hitches 13 and 14, the device 15 being operable to raiser lower the lift hitch 13 relative to the reaction hitch 14 in order to raise or lower the second leg portion 12. The device 15 comprises a lever-operated ratchet device 17, controlled by a suitably long lever 18, and which can be operated in either direction, in order to lengthen or shorten the length of chain between the hooked ends 16, depending upon whether the leg is to be raised or lowered.

As can be seen from Figures 1 to 4, the leg 10 comprises a telescopic assembly of an inner leg and an outer tubular leg and, in the illustrated embodiment, the inner leg forms the first or fixed leg 11. A slot 19 is formed in the wall of the outer tubular leg portion 12, and the hitch 14 provided on the inner first leg 11 extends through the slot and is movable relatively along the slot during relative movement of the leg portions during raising and lowering operations.

However, although not shown, it should be understood that the role of the leg portions of the leg could be reversed, whereby the first and fixed leg comprises the outer tubular leg portion and the second (movable) leg portion comprises the inner leg portion, in which case the slot is formed in the wall of the first leg portion and the hitch which extends through the slot comprises the lifting hitch.

A carry pin 20 is provided, in order to lock the leg portions in any required position of vertical adjustment in any substantially permanent position, after being taken through aligned holes in the leg portion. However, as a safeguard against any failure of the lifting device during operation, a safety pin arrangement is provided which comprises a sturdy shear pin 21 which can be taken through any selected one of aligned and vertically spaced pairs of holes in the fixed leg portion, so as to be in-the path of downward movement of the movable leg portion, and thereby arrest the movement of the latter, in the event of a failure -of the lifting device. It is recommended that the safety pin should always be inserted at a vertical spacing below the lo-wer edge of the movable leg portion which is not more than 4 inches-, at any one time.

By the use of the detachable lifting device 15, each leg can readily be raised or lowered by required amounts, and then locked in position, and the lifting device can then be remov-ed for- application to a further leg.

The operation of the lifting device is reversible, so that ratchet-controlled- descent of each corner of a load can ta-ke place via appropriate downward adjustment of the movable leg portions. In use of lifting legs according to the invention, it has been found that the entire lifting, and lowering operation of large loads can be substantially reduced, in that the lift from ground to vehicle can take place within 15 minutes for one man, and 10 minutes for two man operation. The entire operation is very simple, and does not require the constant lining up of holes through the inner and outer- leg portions.

The user -of the lifting legs has a choice of either using four lifting devices or "pull lifts" to complete the lift, or topurchas.e one or two, by lifting each leg in turin, and then securing with the holding pin to complete the height required.

Lifting legs can be made to lift any size or weight of container or cabin, and any suitable- means may be adopted to attach the legs to cabins or containers, though this is not shown in the drawings.

Claims (11)

1. A lifting leg for use in raising and lowering a large load when attached thereto, in which the leg comprises: a first leg portion which is positionable so as to be supported by the ground; a second leg portion slidable relative to the first leg portion and having means for attaching the second leg portion to anchor points provided on the load, the second leg portion being movable along the first leg portion in order to raise or lower the load; a lift hitch secured to the second leg. portion and projecting laterally therefrom; and, a reaction hitch secured to the first leg portion and projecting laterally therefrom, a manually operable tensile device being attachable at each end to a respective one of said hitches and being operable to raise or lower the lifting hitch relative to the reaction hitch; in which: the-first and second leg portions form a telescopic assembly having an inner leg portion and an outer tubular leg portion; and, a slot is formed in the outer tubular leg portion and the hitch provided on the inner leg portion extends through said slot and is movable relatively along the slot during relative movement of the leg portions during raising and lowering operations.

2. A lifting leg according to claim l and in combination with said manually operated tensile lifting device.

3. A lifting leg according to claim 2, in which the manually operated tensile lifting device comprises a ratchet-operated lifting chain.

4. A lifting leg according to claim 3, in which a long lever arm is coupled with the ratchet device.

5. -A lifting leg according to any one of claims 1 to 4, in which the first leg-portion comprises the inner leg portion and the second leg portion comprises the outer tubular leg portion, in which case the slot is formed in the wall of the second leg portion and the hitch which extends through the slot comprises said reaction hitch.

6. A lifting leg.according. to any one of claims 1 to 4, in which the first leg portion comprises the outer tubular leg portion and the second leg portion comprises the inner leg portion, in which case the slot is formed in the wall of the first leg portion, and the hitch which extends through the slot comprises the lifting hitch.

7. Lifting leg according to any one of the preceding claims, in wh.ich both leg portions of each leg are tubular in construction.

8. A lifting leg according to any one of the preceding claims, including a supporting foot provided on the lower end of the first leg portion, to spread the bearing pressure on the ground.

9. A lifting leg according to any one of the preceding clams, including a safety pin arrangement operable to restrain downward movement operable to restrain downward movement of the second leg portion in the event of failure of the tensile lifting device.

10. A lifting leg according to claim 9, in which the safety pin arrangment -comprises a shear pin which can be entered through a selected one of a series of vertically spaced aligned holes in the first leg portion, and in the path of downward movement of the second leg portion, so as to arrest downward movement of the latter in the event of failure'of the tensile lifting device.

11. A lifting leg according to claim l and substantially as hereinbefore described with reference to, and as shown in the accompanying drawings.