GB2467035A

GB2467035A - Lifting device with pivotally mounted bearer and attachment means

Info

Publication number: GB2467035A
Application number: GB201000186A
Authority: GB
Inventors: Steven John Thorpe
Original assignee: RYEDALE ENERGY Ltd
Current assignee: RYEDALE ENERGY Ltd
Priority date: 2009-01-07
Filing date: 2010-01-07
Publication date: 2010-07-21
Anticipated expiration: 2030-01-07
Also published as: GB201000186D0; GB2467035B; GB0900160D0

Abstract

A deice for lifting an object comprises an elongate lifting arm 1a, 1b pivotally mounted on a fulcrum 3, and a bearer 6 pivotally mounted to the arm for holding attachment means. Bearer 6 may be elongate and transverse to arm 1a, 1b or may extend in the same direction as arm 1a, 1b, and may comprise slot 8. Attachment means and bearer 6 may be separable or integral, and may be threaded lifting keys or shackles. There may be two arms 1a, 1b, which may be co-extensive. Arm 1a, 1b may be extendable, and the distance of the bearer pivot from the arm pivot 3 may be altered. The arm may have hinge 16a, 16b for folding, and may be biased into an unfolded position. Rollers or wheels 4a, 4b may be provided, and may be removable. The axle of wheels 4a, 4b may form the fulcrum 3 of lifting arm 1a, 1b.

Description

Device This invention relates to a lifting device, and the structure of such a lifting device, which are adapted to lift and hold objects of widely varying shape and size easily, safely and securely without damage or snagging, whilst ensuring that the object is readily released when necessary. The device of the present invention may be used as a static and/or movable (including portable) lifting and/or transport device.

In industrial and commercial premises, and domestic premises, covers for manholes, trenches, ditches, channels, and other watercourses, cabling, piping and pipeline channelling and conduits, air ducting and access ducting and shafts to tunnels, subways and passageways, and bores and wells are often held in place by a lip on the covered structure, configured and adapted to releasably engage or lock and hold them in position.

Such lips may e.g. wholly or partly house the cover, e.g. such a cover may be of a complementary shape to, and fit within the lip, or the cover may fit over the lip, which will engage with the underside of the cover, e.g. in a recess, indentation, groove or channel.

Such covers are often heavy and/or cumbersome, to the extent that they are not easily manually lifted off the covered structure, in particular by one or two persons without further mechanical aid.

Simple cover lifting and transport devices are known, e.g. lifting keys with lifting handles and lifting lugs designed to be of a shape and size that is complementary to a recess in the cover, or with threaded shanks designed to screw into blind threaded holes in the cover, all of which are often specific to a given manhole cover; or lifting eyes with lifting handles, the eyes being designed to be of a shape and size that is complementary to the neck of a mushroom stud set in the cover.

Additionally, there is a need to lift and move items of widely varying shape and size, e.g. heavy stones of an irregular shape, such as those which may be used in the construction of a rock layer in civil engineering or a garden rockery.

Known devices therefore include linked pairs of calliper lifting arms, in which two pairs of downwardly pointing claw arms engage the item, and on lifting close on the item under its own weight.

Such devices do not provide means for one person to lift the item readily or safely, especially in the case of large rocks, which it may be required to lift and manoeuvre. This can lead to emergency and/or accident situations.

Other devices, which provide mechanical advantage, are known, e.g. a crow bar applied to a recess in a manhole cover. Such devices, whilst they provide means for one person to lift the cover, do not lift the cover vertically, and in the case of covers which engage with a lip on the covered structure, can lead to snagging of the cover on the lip.

An object of the present invention is to provide a device for lifting and holding an object, such as (but not limited to) covers as mentioned above, which provides mechanical advantage on the lifting process.

Another object of the present invention is to provide a device for lifting an object vertically, so that in the case of objects which may snag on a housing or engaging integer, such snagging is avoided.

Another object of the present invention is to provide a device that is towable or pushable, such as a trolley, such that it is safe for easy movement by an individual.

It is also an object of the present invention to provide a lifting device, in which the object is securely lifted and held by the device, but is readily released when necessary.

It is yet another object of the present invention to provide a foldable, and therefore more portable, device.

Therefore, according to the present invention there is provided a device for lifting an object, having at least one elongate lifting arm pivotally mounted on a fulcrum, characterised by a bearer for attachment of the object to the lifting device, pivotally mounted on the elongate lifting arm on a pivot transverse to the lifting arm, and comprising at least one attachment means on the bearer, which attaches the object to the bearer, such that in use of the device, when the lifting arm over the object is raised to lift and support the object, it causes the bearer to pivot on the lifting arm.

The device of the present invention offers a significant advantage over lifting devices used hitherto, in that it can provide a mechanical advantage which enables one person easily to lift a cumbersome, heavy or otherwise unwieldy object, and it provides as nearly vertically as possible a lift of the object that is lifted, so that the object does not snag, for example in the case of housed or engaged cover on any housing or engaging lip on the covered structure.

The device may be a static lifting device or form part of a mobile structure, so that the object once lifted may be readily transported and laid down elsewhere.

The or each lifting arm and the bearer, which is pivotally mounted on the lifting arm, may take a variety of forms dependent on the particular features of the device.

One or more lifting arms may be present in the device of the present invention.

Each such arm usually extends longitudinally and generally horizontally within the overall assembly of the device. Such arms may each comprise a rigid member, such as a bar, rod or rail, which may be round or rectangular-section tubular, A less preferred device has a single arm with a single pivot, e.g. mounted on a single trunnion or bracket, or between a pair of such integers, on the rest of the device.

A preferred device has two or more lifting arms, which more preferably are so configured as to be elongate in the same direction, coterminous and pivoted about the same fulcrum.

In particular, such arms may be spanned by and connected to two or more stout rigid members, such as bars, rods, rails or rungs. These form a generally flat, generally quadrilateral or rectangular bodywork, preferably a skeleton framework, such as a lifting chassis or scaffold in the device. These may also be round or rectangular-section tubular.

Each lifting arm may be pivotally mounted directly, or on a single trunnion or bracket, or between a pair of such integers, on the rest of the device.

A preferred lifting device has two identical lifting arms which are pivoted to rotate on the same fulcrum, and are spanned by and connected to two or more transverse members, as described above.

The latter may be mounted in a permanent position in the lifting chassis, as rungs between the longitudinal arms in the chassis. This may be achieved by conventional means, e.g. by welding.

Alternatively, it may be desired that the longitudinal lifting arms and the two or more transverse members may engage releasably and be held in place, e.g. by bolts and nuts or set pins passing into and/or through holes formed in the arms and members, optionally with locking washers and/or nuts.

The device of the present invention may be static, i.e. installed permanently for recurrent removal and/or replacement of an integer of a static external structure.

In such an embodiment, the device may be mounted on am upright pivot, so that it may be slewed to relocate the lifted object.

Preferably, the device of the present invention is mounted on, or more preferably is, a mobile structure.

In the former case, the device may be mounted on a towable/pushable structure that has at least three rolling means, such as castors, rollers or wheels.

Alternatively, in the latter case, where it is a mobile structure, the lifting chassis or scaffold in the device may have at least two rolling means, such as rollers or wheels, rotatably mounted on it, either permanently or demountably, e.g. on axles or spindles.

The rolling means preferably then consist of one pair of rollers or wheels. They may be directly or indirectly mounted, e.g. each lifting arm may have an axle mounted directly on it, or on a single trunnion or bracket, or between a pair of such integers.

If the lifting device has two identical lifting arms which are pivoted to rotate on the same fulcrum, and that is the axle of a pair of rolling means, as described above, the rolling means should be installed sufficiently far apart to minimise lateral rotation of the device on lifting.

In general, however, the structure in use should desirably be compact with little or nothing projecting, such as the rolling means should not then hamper the movement and manoeuvring of the device to and from the object. Thus, it may be preferred that any such rolling means do not extend beyond the device at its widest point by much. For reasons of stability, in particular when the load is wide, it may be preferred that the rolling means are further apart than the points of attachment on the object.

Where the device has two identical lifting arms which are pivoted to rotate on the same fulcrum, and are spanned by and connected to two or more transverse members, as described above, the transverse member which is furthest from the fulcrum may conveniently extend transversely beyond the lifting arms and/or any rolling means to form a towing handle.

Alternatively, the device may be provided with a separate handle, which may be a straight or U-bar, rod or tube. It may be advantageous that it is provided with an extendable and retractable handle, e.g. one movably mounted on the device or a fixed telescopic round or rectangular-section tubular handle, each of which may be held in its extended use position by sliding friction or locking means.

The or each lifting arm generally comprises a first part on which the bearer is mounted, and a second part, usually integral with the second part of the lifting arm, to which force is applied in use of the lifting device to rotate the lifting arm(s) to lift and hold the desired object.

The device may be adapted for manual or powered (e.g. hydraulic) operation.

In particular for lighter objects, such as manholes, trench covers, etc., manual operation is preferred. For manual operation it is preferred that the first and second parts of the lifting arms should be so configured as to confer sufficient mechanical advantage on the device, that device, irrespective of its weight lifting capacity may be easily operated by one person, e.g. a 70 kg adult.

A less preferred device has the first and second parts of the or each lifting arm on the same side of the fulcrum. The second part may be further from the fulcrum than the first, in which case, the device still has mechanical advantage, and can be operated manually. The second part will of course have to be raised to raise the first part, and that may gives rise to disadvantageous loss of visibility of the object, which may be inconvenient in the operation of the device.

In an even less preferred device, the second part may be closer to the fulcrum than the first, in which case, the device has no mechanical advantage, and is not adapted to be operated manually. The second part will in general then have to be raised with power, e.g. hydraulic power.

A preferred device has the first and second parts of the or each lifting arm on opposite sides of the fulcrum. The second part extends further from the fulcrum than the first, in which case, the device has mechanical advantage, and can be operated manually. The second part will of course have to be lowered to raise the first part, and this gives rise to advantageous better visibility of the object, which is convenient in the operation of the device.

The lifting capacity of the device that can be operated manually will depend on the practical mechanical advantage from the lever arm about the fulcrum (i.e. the ratio of the length of the lifting arm between the fulcrum and the point at which the operator applies force to the lifting arm to the length of the lifting arm between the fulcrum and the bearer) that can be obtained when the second part of the lifting arm extends further from the fulcrum than the arm to the bearer on the first.

It will also be commensurate with adequate strength of the materials that components of the device are made of.

For manual lifting devices, the first and second parts of the lifting arm should be on opposite sides of the fulcrum, and the second part longer than the first.

They are thus embodiments where the second part is lowered to raise the first part.

For such devices, suitable mechanical advantages lie in the range of 2 to 5, e.g. 2.5 to 4.

Manual device lifting capacities lie in the range of up to 500kg, such as up to 300kg, e.g. 80 to 200kg. It will be appreciated that for the range of mechanical advantages in the device mentioned above, a device with a lifting capacity towards the higher end of the above ranges may require two or more persons or mechanical assistance to operate it in lifting and/or transporting the lifted object.

The mechanical advantage of the device may be adjusted for a given lever arm of the first part. This gives rise to advantageous flexibility in the lifting capacity of the device, which is important in the manual operation of the device. Ways in which such adjustment may be made include adjusting the length of the lever arm of the second part, and preferably adjusting the position of one or more counterweights along the lever arm of the second part.

The length of the lever arm of the second part of the or each lifting arm may be adjusted by providing a second part which comprises two or more mutually retractable units, whereby the length of the lifting arm may be adjusted. These may be cooperating units which are adapted to engage with and slide or run past each other, or one unit may be a cooperating sleeve for the other. The units may be mutually located in use by the mounting and/or locating means described below in relation to adjustable counterweights.

Where the adjustment is made by counterweights, each lifting arm may be provided with a series of separate apertures, gaps, openings, slots, slits or cavities at a number of locations along its length, or a single longitudinal channel, slot or slit, to receive locating parts of the counterweights.

The counterweights may be mounted on the arm by conventional means. For example, they may comprise at least one threaded captive bolt adapted to be received in the apertures or slot in the lifting arm, and be held there by locking nuts. Alternatively each may be held in place by means of one or more threaded set-pins engaging with threaded holes in the beam and passing through holes or short slots in the means; locating pins passing through holes in the beam and held in place by cotter pins or spring clips in annular grooves; mushroom pegs engaging in respective keyhole slots formed in the arm; or bolts each with a head which engages with two inwardly projecting flanges or lips on each side of a longitudinal channel, and with a threaded shank passing through a hole in the counterweight, and held in place by a locking nut.

In a preferred device according to the invention, the or each lifting arm is provided with an attached or integral track or channel on or in which a slider, roller, wheel or runner attached to or integral with a counterweight runs.

The track or channel may be provided at intervals with locating means for the counterweights, such as transverse indentations, e.g. notches or grooves adapted to engage a spring-biased tongue on the counterweight; or serrations adapted to engage an indentation in a spring-biased tongue on the counterweight. Alternatively, such a tongue may be provided with a quick release locking nut to lock it in position.

Another preferred embodiment of the device has manual or (e.g. electrically) powered winching means for winding a cable for moving the counterweight along the or each lifting arm. This may be mounted on part of the lifting are at a suitable position, and the direction of pull of the winching means should preferably be aligned with the direction of the track or channel for the counterweight.

The counterweight may be located along the lifting arm by the position of the cable on the winch drum or spindle or the above means may be used to attach the counterweight to the lifting arm in any of several pre-set positions.

To minimise lateral rotation of the device on lifting where there are more than two lifting arms, it is preferred that the counterweights and any winching means are symmetrically disposed in the device. Thus, with a pair of lifting arms, each may be provided with identical counterweights on identical tracks or channels, and both may be mounted on a slider, roller, wheel or runner which spans the two lifting arms.

Alternatively, a single counterweight may be mounted at or near the centre of the slider or runner. Where such a device has winching means it Is preferably mounted at or near the centre of a transverse member mounted on and spanning the two lifting arms.

Thus the positions where counterweights on the lifting arm may be secured can be adjusted as desired or necessary.

It is preferred that the members of the lifting chassis are not too dense (commensurate with adequate strength) and may thus be made of higher-tensile aluminium alloys, such as duralumin, or mild steel, e.g. as round or rectangular-section tubular rod, or engineering plastics -carbon fibre composites, as each offer good strength to weight ratios.

For protection of the chassis materials, e.g. against corrosion, they are preferably covered with a protective layer or have a modified surface layer.

Suitable layers include powder coatings, anodised surface films, electroplate and galvanised covering layers, paint, in particular anti-corrosion paint, coats, and relatively thick thermoplastics casings, jackets and sheathing.

The ends of the lifting arms in the chassis which are closest to the operator, in particular in a manual device may extend into projections which form lifting handles and/or pushing/towing handles in corresponding movables devices as described above, and which may be provided with textured elastomeric sheathing or covering to provide a better grip.

Preferably, the bearer that is pivoted to rotate on the lifting arm is elongate. In its simplest form the bearer may comprise a single rigid beam, girder, bar, pole, rail, or rod or a generally flat plate, preferably of a size defined by the object, which is pivoted to rotate about a position on the or each lifting arm, and In particular, such that it may span the attachment points on the object to be lifted.

A less preferred device has a bearer which is elongate longitudinally in the device, as is the lifting arm, and is e.g. pivoted at its mid-point. Such an embodiment can be configured to span the attachment points on the object, and will lift and support the object, and it causes the bearer to pivot on the lifting arm.

It thus offers the significant advantage of the present invention that it provides as nearly vertically as possible a lift of the object that is lifted, so that the object does not snag, for example in the case of housed or engaged cover on any housing or engaging lip on the covered structure.

This embodiment of the device in which the bearer extends longitudinally generally may have disadvantage of a relatively large moment of inertia about the bearer pivots, which may favour oscillation of the object in lifting, but plain bearings may be used to reduce this tendency.

They have the advantage that sufficient sliding friction between the axles and the bearing surfaces occurs on rotation of the axles in the bearings in use to dampen oscillations, or other conventional dampening means may be used.

A preferred device has a bearer which is elongate transversely in the device, and is e.g. pivoted at each end. Such an embodiment can be configured to span the attachment points on the object, and will lift and support the object, and it causes the bearer to pivot on the lifting arm.

This embodiment of the device in which the bearer extends longitudinally generally has the disadvantage of a relatively small moment of inertia about the bearer pivots, which minimises oscillation of the object in lifting, but plain bearings may again be used.

The bearer pivots may be movably mounted on the first part of the or each elongate lifting arm, whereby the distance of the bearer pivots from the lifting arm pivots, and the hence the mechanical advantage of the device, may be adjusted for a given lever arm of the second part.

This gives rise to advantageous flexibility in the lifting capacity of the device.

This may be important in the manual operation of the device.

Where the bearer is mounted in trunnions, the or each lifting arm may be provided with a series of separate apertures, gaps, openings, slots, slits or cavities at a number of locations along its length, or a single channel, slot or slit, to receive locating parts of the trunnions.

The bearer trunnions may be mounted on the arm by conventional means, e.g. they may comprise at least one threaded captive bolt adapted to be received in the apertures or slot in the lifting arm, and be held there by locking nuts.

Alternatively they be held in place by means of threaded set-pins engaging with threaded holes in the beam and passing through holes or short slots in the means; locating pins passing through holes in the beam and held in place by cotter pins or spring clips in annular grooves; mushroom pegs engaging in respective keyhole slots formed in the bearer; or bolts each with a head which engages with two inwardly projecting flanges or lips on each side of a longitudinal channel, and with a threaded shank passing through a hole in the counterweight, and held in place by a locking nut.

In one device according to the invention, the or each lifting arm is provided with an integral track or channel on or in which a slider, roller, wheel or runner attached to or integral with a bearer trunnion runs.

The track or channel may be provided at intervals with locating means for the trunnion, such as transverse indentations, e.g. notched or grooves adapted to engage a spring-biased tongue on the counterweight; or serrations adapted to engage an indentation in a spring-biased tongue on the trunnion. Alternatively, such a tongue may be provided with a quick release locking nut to lock it in position.

To minimise lateral rotation of the device on lifting where there are more than two lifting arms, it is preferred that the bearer trunn ions are symmetrically disposed in the device.

Thus, with a pair of lifting arms, each may be provided with identical trunnions on identical tracks or channels, and both may be mounted on a slider or runner Thus the positions where the trunnions on the lifting arm may be secured can be adjusted as desired or necessary.

It is preferred that the bearer or members of the bearer are not too dense (commensurate with adequate strength) and may thus be made of higher-tensile aluminium alloys, such as duralumin, or mild steel, e.g. as round or rectangular-section solid or tubular rod, or engineering plastics -carbon fibre composites, as each offer good strength to weight ratios.

For protection of the materials, e.g. against corrosion, they are preferably covered with a protective layer or have a modified surface layer. Suitable layers include powder coatings, anodised surface films, electroplate and galvanised covering layers, paint, in particular anti-corrosion paint, coats, and relatively thick thermoplastics casings, jackets and sheathing.

It is preferred that the present device comprises at least two attachment means, to lift and hold the object more stably than, e.g. by a single such means.

It is therefore useful if the bearer in the device has two attachment means mounted in parallel on it, towards or at opposite ends of the bearer, and particularly so if the object comprises at least two attachment points also towards or at opposite ends of it, e.g. a pair of shaped recesses or mushroom studs or equivalent thereof, or points on a stone.

The attachment means for lifting and holding the object may be separate integers from the bearer, or the bearer may be integral with any attachment means.

It is preferred that any attachment means in the device according to this embodiment are characterised by having much the same distance between them as the attachment points on the object.

Thus, in use, the bearer spans the object, such as a cover in a housing lip or on an engaging lip, and any lift on the attachment means is essentially as nearly vertically as possible.

This arrangement provides better balance, especially when the device Is a towable or pushable structure, as described hereinafter.

In such an embodiment of the device of the present invention, where the attachment means are separate integers from the bearer, it may be desired that they are configured to be demountable but locked in a use position, and this may be achieved in a variety of ways.

Where the bearer is elongate, e.g. a beam, it may be provided with a series of separate apertures, gaps, openings, slots, slits or cavities at a number of locations along its length, or a single channel, slot or slit, to receive the attachment means.

The attachment means may be mounted on the bearer, by conventional means, e.g. they may comprise at least two lifting keys each adapted to engage in recesses or apertures in the object, and having a shank adapted to be received and retained in the apertures or slot in the bearer and to pass through a plate which spans the bearer and has two flanges which engage with two opposing faces of the bearer, and optionally having cooperating threaded locking nuts adapted to releasably hold the attachment means in place; at least two threaded lifting shackles adapted to engage around mushroom studs on the object and each having shanks adapted to be received and retained in the apertures or slot in the bearer as recited for lifting keys immediately above, and having cooperating threaded locking nuts adapted to releasably hold the attachment means in place; or at least two callipers so constructed and arranged that in use of the device, when the lifting arm rotates about its fulcrum, the object is urged under gravity to cause the callipers to close and grip the object, also being threaded and having cooperating threaded locking nuts adapted to releasably hold the attachment means in place, Each of these may alternatively be held in place by means of threaded set-pins engaging with threaded holes in the beam and passing through holes or short slots in the means; locating pins passing through holes in the beam and held in place by cotter pins or spring clips in annular grooves; or mushroom pegs engaging in respective keyhole slots formed in the bearer.

Thus the positions where the attachment means on the bearer can be secured can be adjusted as desired or necessary.

In a less preferred device according to the invention, the bearer is integral with the attachment means.

Another less preferred embodiment of the device has only one attachment means for lifting and holding an object. The means may be mounted on a suitable part of the bearer at a single position, which should preferably be aligned with the centre of gravity of the fully laden device to minimise lateral rotation of the device on lifting. The means may be adapted to attach to the object in one or several positions, eg. it may be bifurcated. In either case, the point of attachment to the bearer should be as nearly above the centre or gravity of the object as possible.

In one embodiment, the bearer may be mounted between the first parts of a pair of lifting arms, which may also extend transversely of the device, to form a transverse base frame, e.g. a generally flat generally rectangular C-shaped transverse base frame (19) forming part of, and projecting at right angles to the rest of, the lifting chassis. In use, raising of the first part past the point at which the lifted object will clear, e.g. any housing or engaging lip takes the base frame slightly upwardly past horizontal, causing the object to be in abutment with part of the base frame, preventing its further rotation, and steadying it for transport.

The lower face of such a base frame may be provided with one or more projections, points or ridges such that the lower face of the base frame is held away from the lifted object, while still providing an abutment for it.

The present device is on most occasions very stable when in use.

However, it may be desirable that the device structure be provided with appropriate stabilising means, if the surface on which it is used is a slanting, uneven or rough surface, e.g. when it in use for lifting one or more covers for manholes, trenches, ditches, channels, and other watercourses, or bores or wells which are not surrounded by level hard standing; where the device is to be used for lifting heavy objects near its maximum lifting capacity; and/or where it is a towable or pushable structure.

These may take a variety of forms, depending on the weight that the device may have to bear, and the slant or unevenness of any surface. Thus the structure may be provided with stabilising means mounted to act on the ground on each side of the device in line with the fulcrum of the lifting arms.

They may, e.g. be jacks or other movable integers, similar to those described above for the adjustment of the lever arms of the first ands second parts of the lifting arms, mounted on transverse sliding, e.g. telescopic, or flip-up or flip-down arms, e.g. housed in complementary recesses in the lifting device. The supports may also be configured to be demountable.

It is advantageous that the two parts of the lifting arms are arranged to define a shallow upward V in the in the shape of the lifting arm around the fulcrum at the junction of the first and second parts of the lifting arms, so that in use the first part may be conveniently held in a generally horizontal fashion above the object to be raised, before the lifting arms are rotated about the fulcrum, and the outer end of the second part may be held at a convenient height for towing or pushing.

It is advantageous that, once used and once the object has been removed, the device can collapse into a relatively small volume for lifting. Thus, the second parts of the longitudinal lifting arms may be interrupted by a hinged joint, which may be formed by two pairs of cooperating trunnions with common pivot pins, extending generally upwardly of, often at right angles to, the lifting arms of the device.

The device, when out of use, may be folded into a stowage position, by means of this hinge.

When the device is unfolded into a use position, the two elongate lifting arms are held in its extended use position by the abutment of the two parts under gravity.

Each may alternatively or additionally be held in position, e.g. with a strong spring bias and/or each may be locked in its use position by latches or pins retained by cotter pins or spring clips in annular grooves.

A lifting device in accordance with this invention is described and illustrated with reference to the drawings, showing embodiments by way of example only.

Figures la, lb and lc show respectively a side view of a lifting device at rest, a side view of the lifting device, when folded in a stowage position, and a top plan view of the device.

Referring to Figures la to lc of the drawings, the lifting device comprises a pair of co-extensive elongate lifting arms (la, lb), each pivotally mounted on a lifting arm fulcrum (3) common to both.

Here, the latter is a fixed axle for a pair of wheels (4a, 4b) that spans and extends beyond the lifting arms (la, lb), and on which the wheels (4a, 4b) are rotatably mounted.

The device depicted is thus a towable or pushable structure, here such a trolley, raised off the ground and clear of the object to be lifted by the pair of wheels (4a, 4b) mounted in a permanent position on the elongate lifting arms (la, lb).

The lifting arms (la, lb) comprise a first part (5a, 5b) on one side of the fulcrum (3), on which a bearer (6) is pivotally mounted, and a second part (9a, 9b) on the other side of the fulcrum (3), integral with the first part (5a, 5b) and on which downward force is applied in use to raise the first part (5a, 5b) on the other side of the fulcrum (3).

The two parts are arranged to define a shallow upward V in the in the shape of the lifting arm around the fulcrum (3) at the junction of the first (5a, 5b) and second (9a, 9b) parts of the lifting arms (la, lb).

In use the first part (5a, 5b) may be conveniently held in a generally horizontal fashion above the object to be raised, before the lifting arms (la, ib) are rotated about the fulcrum (3), and the outer end of the second part (9a, 9b) may be held at a convenient height for towing or pushing.

In the device depicted, the bearer (6) is a slotted beam. It is elongate in a direction transverse to and pivotally mounted between the longitudinally elongate lifting arms (la, ib). The bearer (6) is configured to at least partly span the object to be lifted.

Two attachment means (7) (not shown in Figs 1) for attaching and holding an object to the device are adapted to engage with recesses or indents in or studs on the object to be lifted, and to be received and releasably held in the slot (8) in the bearer (6). They may e.g. be conventional lifting keys or shackles held in a use position by locking nuts on threaded shanks passing through the slot (8) on the bearer (6). and through a plate (21) which spans the bearer (6) and has two flanges which engage with two opposing faces of the bearer (6).

In more detail, the device comprises a pair of longitudinal members (la, ib).

These comprise a first part (5a, 5b) on one side of the fulcrum (3) , and a second part (9a, 9b) on the other side of the fulcrum (3), integral with the first part (5a, 5b).

Three transverse members, here each a bar (11, 12, 13) are permanently mounted respectively in a position one towards the outer ends and two towards the inner ends of the second part (9a, 9b) of the longitudinal arms (la, ib) to form a generally flat generally rectangular part of a lifting chassis.

Near where outer (12) of the pair of members (12, 13) is mounted towards the outer end of the lifting arms (1 a, 1 b, the second parts (9a, 9b) of the longitudinal lifting arms (la, ib) are interrupted by a hinged joint (16a, 16b). This is formed by two pairs of cooperating trunnions, extending generally upwardly of, often at right angles to, the lifting arms (1 a, 1 b) of the device.

The device, when out of use, may be folded into a stowage position, by means of this hinge (16a, 16b) as depicted in Figure lb. When the device is unfolded into a use position, the two elongate lifting arms (la, ib) are held in its extended use position by the abutment of the two parts under gravity.

(Each may alternatively or additionally be held in position, e.g. with a strong spring bias and/or each may be locked in its use position by latches or retained pins or split pins.) The bar (11) that is mounted towards outer end of the longitudinal lifting arms (la, ib) extends beyond the lifting arms (la, ib), and the wheels (4a, 4b) are which are rotatably mounted thereon, to form a handle that is at or is in a position that is extendible to a convenient towing or pushing height.

The first part (5a, 5b) of the on the other side of the fulcrum (3), and integral with the second part (9a, 9b) lifting chassis comprises a pair of longitudinal members (1 a, 1 b) which are an extension of the a second part (9a, 9b) on the other side of the fulcrum.

It also comprises a pair of longitudinal members (15a, 15b) which are integral with a transverse member (17), also a bar, in turn permanently mounted in a position at the outer ends of the extension of the second part (9a, 9b) of the longitudinal arms (la, ib).

These integers form a generally flat generally rectangular C-shaped transverse base frame (19) forming part of, and projecting at right angles to the rest of, the lifting chassis.

The transverse elongate bearer (8) is pivotally mounted between the inner faces of the longitudinal members (1 5a, 1 5b) by way of two short axles housed in plain bearings. Plain bearings have the advantage that sufficient sliding friction between the axles and the bearing surfaces occurs on rotation of the axles in the bearings in use to dampen any oscillation from lifting an object with a relatively high moment of inertia.

The fulcrum (3) common to both lifting arms (la, ib), is a fixed axle for a pair of wheels (4a, 4b) through the junction of the first (5a, 5b) and second (9a, 9b) parts of the arms.

It is preferred that such an axle on which the wheels (4a, 4b) are rotatably mounted is mounted in a pair of trunnions mounted on and extending downwardly from the two lifting arms (la, ib), as this raises the device to a position when in use which clears the substrate ground, and better holds any lifted object clear of the ground.

The two parts (5a, 5b) and (9a, 9b) meet at an angle to define a shallow upward V in the in the shape of the lifting arms around the fulcrum (3). Here the angle is about 160 to 175 degrees. The second part (9a, 9b) of the arms is two to four times as long as the first part (5a, 5b).

We have found that, for the depth and weight of cover for which this embodiment is designed, the length of the second parts (9a, 9b) give sufficient leverage for one person to lift the cover comfortably.

The angle between the parts ensures that when the second part is depressed to a convenient position for the operator to be able to handle the device and the cover, the base frame is generally slightly upwardly past horizontal, causing the cover to be in abutment with part of the base frame (19), preventing its further rotation, and steadying it for transport.

In use, the device is unfolded into a use position, with the two elongate lifting arms (la, ib) held in the extended use position. The device is then towed or pushed on its wheels (4a, 4b) by the handle (11) until the elongate bearer spans the object, and the slot (8) on the bearer (8) is aligned with and directly above the attachment points on the object.

A pair of conventional lifting keys or shackles, configured to be demountable but locked in a use position on the bearer (6) by locking nuts on threaded shanks, each has the shank fed through the slot (6) and pass through a plate (21) which spans the bearer (6) and has two flanges (22, 22) which engage with two opposing faces of the bearer, and optionally are engaged with recesses or indents in or studs on the object to be lifted as appropriate.

These are then releasably held in the slot (8) in the bearer (6), directly mounted above the attachment points on the object by torquing down the locking nuts onto the bearer (8).

Pushing down on the handle (11) causes the first part (5a, 5b) of the longitudinal members (1 a, 1 b) to rise, and raise the cover.

The bearer (6) rotates about its pivots, so that the pull on the lifted cover is generally vertically and is directly above the attachment points on the cover, and the cover is lifted without snagging on any housing or engaging lip.

Further raising of the first part (5a, 5b) takes the base frame slightly upwardly past horizontal, causing the cover to be in abutment with part of the base frame, preventing its further rotation, and steadying it for transport.

The device is then towed or pushed on its wheels using the handle away from the lift site.

The cover may if desired be laid down and released by reversing the above steps, and repaired or replaced, or the cover may be left in its position in the device, the covered structure repaired or replaced, the device wheeled back and to position the bearer (6) directly above the attachment points on the object, and the cover replaced by reversing the above steps.

Claims

Claims 1. A device for lifting an object, having at least one elongate lifting arm pivotally mounted on a fulcrum, characterised by a bearer for attachment of the object to the lifting device, pivotally mounted on the elongate lifting arm on a pivot transverse to the lifting arm, and comprising at least one attachment means on the bearer, which attaches the object to the bearer, such that in use of the device, when the lifting arm over the object is raised to lift and support the object, it causes the bearer to pivot on the lifting arm.
2. A device according to claim 1, characterised in that the bearer is elongate, and comprises at least two attachment means to attach the bearer to the object.
3. A device according to claim 2 characterised in that the bearer is elongate in a direction transverse to the elongate lifting arm.
4. A device according to claim 1 characterised by at least two elongate lifting arms which are pivotally mounted on the same fulcrum and an elongate bearer which spans, and is pivotally mounted on each of, the lifting arms.
5. A device according to claim 4 characterised in that the lifting arms are exactly or roughly co-extensive.
6. A device according to claim 1 characterised in that the bearer and the attachment means are separable integers.
7. A device according to claim 6 characterised in that the bearer is adapted to receive the attachment means.
8. A device according to claim 6 characterised in that the attachment means comprise at least two threaded lifting keys adapted to engage in recesses or apertures in the object or at least two shackles adapted to engage around mushroom studs on the object.
9. A device according to claim 1 characterised in that the bearer is integral with the attachment means.
1O.A device according to claim 2 characterised by a pair of attachment means, one mounted towards one end of the elongate bearer and the other towards the other end of the elongate bearer.
11.A device according to claim 1, 2 or 4 to 15, characterised in that the bearer and the lifting arm are elongate in the same direction.
12.A device according to claim 1 characterised in that the lifting arm and the bearer mounted thereon are so constructed and arranged that in use of the device, when the lifting arm rotates about its fulcrum sufficiently to lift the object clear of its location, the object is urged under gravity to be located in contact with a lower face of the device.
13.A device according to claim 1 characterised in that the device is provided with fastening means to hold the lifted object in place on the device
14.A device according to claim 1 characterised in that the bearer pivots are movably mounted on the elongate lifting arm, whereby the distance of the bearer pivots from the lifting arm pivots may be adjusted.
15.A device according to claim 1 characterised in that the elongate lifting arm has a first part on one side of the lifting arm fulcrum, on which the bearer is mounted, and a second part on the other side of the fulcrum.
16.A device according to claim 1, characterised by a shallow upward V in the in the shape of the elongate lifting arm at or above the fulcrum.
17.A device according to claim 1 characterised in that the elongate lifting arm comprises two or more mutually retractable units, whereby the length of the lifting arm may be adjusted.
18. A device according to claim 17 characterised in that one of a pair of mutually retractable units is a cooperating sleeve for the other.
19.A device according to claim 1 characterised in that the lifting arm is hinged for folding.
20.A device according to claim 19 characterised in that the lifting arm is so constructed and arranged that in use of the device the lifting arm is held in an unfolded configuration under gravity.
21.A device according to claim 19 characterised in that the lifting arm is biased into an unfolded configuration.
22.A device according to claim 19 characterised in that device has latching means to hold the lifting arm in a folded configuration.
23.A device according to claim 1 characterised in that it is adapted for manual operation.
24.A device according to claim 15 characterised in that the minimum length of the second part is at least three times that of the first part.
25.A device according to claim 1 characterised in that it is a towable or pushable structure.
26.A device according to claim 1 characterised in that it is provided with at least one rolling means.
27.A device according to claim 1 characterised in that it is provided with at least two rolling means.
28.A device according to claim 1 characterised in that it is provided with one pair of rolling means.
29.A device according to claim 1 characterised in that it is provided with one pair of rollers or wheels.
30.A device according to claim 1 characterised in that it is provided with one pair of rollers or wheels mounted on or in the junction of the first and second parts of the elongate lifting arm.
31.A device according to claim 1 characterised in that rolling means are installed in a fixed position.
32.A device according to claim 1 characterised in that the rolling means are removable.
33.A device according to claim 1 characterised in that it is provided with an axle on which the pair of rollers or wheels is mounted.
34.A device according to claim 33 characterised in that the axle is the fulcrum of the lifting arm.