GB2289037A - Access cover lifting tool - Google Patents

Abstract

A lifting tool comprises a rectangular bar with wheels 3 and mounting two laterally movable forks 4 which can be located above the cover lifting holes to engage the cross pieces 9 of two self-supporting, spring-loaded, height-adjustable keys 8 which lock securely into the cover's lifting holes and incorporating at its centre a socket which takes a four foot steel lever bar which the operator pulls down to apply pressure on the lifting keys. The forks 4 may each have a cradle 7 to support a cross piece 9 (Fig. 1, not shown) or each support a pillar 22 and beam 23 with a slot 26 for a cross piece 9. <IMAGE>

Description

DEVICE FOR HFflNG MANHOLE COVERS Field of the Invention This invention relates to a device for lifting and moving manhole covers or the like.

Background to the Invention Inspection pits or manholes are provided in roads and pavements for a wide range of services, from drainage to water and electricity supplies and telecommunications. To withstand traffic passing over, and to ensure that they are not readily removable by unauthorised persons, the covers to such manholes are typically manufactured in cast iron or other heavy materials. When they need to be lifted for inspection or maintenance work, the covers require at least two workers to move them, and the larger covers may require four workers, or mechanised lifting gear such as a small crane, mechanical digger or fork-lift truck.

The covers are not only heavy to lift, but also become bedded in to their locating frame and sealed with dirt and rust, for example. To break the seal, it is necessary to strike the cover with a heavy hammer or the like, while levering it up at one side with a pinch bar. Thus, two or more men are required to move the cover, since one has to hold on to the pinch bar while another hammers, and then two or more are required to lift the cover away.

Summarv of the Invention The invention provides a device for lifting manhole covers, comprising a main support member mounting a pair of wheels, at least one lever extending forwardly of the main support member, a lifting key engageable with the manhole cover and mountable on the lever, and an operating handle extending rearwardly of the main support member and arranged such that downward pressure on the handle rotates the or each lever upwardly, lifting the lifting key or keys and thereby lifting the manhole cover engaged by the key or keys.

Preferably, the or each lifting key is mountable on its lever in such a manner as to ensure that a small degree of downward movement of the handle takes place before force is transmitted via the key or keys to the manhole cover. This ensures that an upwardly-directed blow is delivered to the cover through the key or keys before lifting commences in order to free the cover from its seating.

The or each lever is preferably slidably mounted on the main support member so as to be positionable at the correct lateral position for engagement of the key or keys with the holes in the manhole cover. For smaller covers, the device preferably comprises two levers, each engageable with a single key, and each being slidable laterally. For covers having only one hole for engagement of a key, only one of the levers is used, positioned as near as possible to the centre of the main support member. In a version of the device for use with larger covers, each lever is provided with a mounting which is rotatable in a vertical plane and on which is pivotally mounted a cross-beam in which two of the keys may be slidably mounted.

Thus, four keys can engage in the four holes provided in larger manholes, the lateral sliding of the levers and the sliding mount of the keys in the cross-beams, together with the rotating and swivelling mount of the beams on the levers, permits the keys to be lifted vertically wherever the holes are located in the cover.

The axis of the main support member is preferably offset vertically and horizontally, suitably at approximately 45" in a vertical plane, from the axis of rotation of the wheels, so that the leverage is magnified during lifting.

The handle is preferably formed of a slightly springy steel so as to enhance the effect of the blow struck to the cover, and so as to reduce the shock transmitted to the user.

The device is simple and rugged in construction, and permits a single operator to lift and move a manhole cover whose weight would conventionally require two or even four men to lift and move. The device is readily portable, and can be transported in the boot of a car or in a small van and carried from there to where it is needed by one man.

Brief Description of the Drawings In the drawings, which illustrate exemplary embodiments of the invention: Figure 1 is a perspective view of a device according to a first embodiment of the invention, in use; Figure 2 is a perspective view of a device according to a second embodiment of the invention, being prepared for use; and Figure 3 is a diagrammatic side elevation of the device shown in Figure 2.

Detailed Description of the Illustrated Embodiments Referring first to Figure 1, the device comprises a main support bar 1 welded at each end to a wheel mounting member 2 (see Figs 2 and 3) providing an offset mounting for the wheels 3. Two levers 4 are slidably mounted on the bar 1, while a handle 5 of bright steel extends from a drawn steel socket 6 welded to the centre of the bar 1. The handle 5 is removable from the boss 6 to permit the device to be more readily transported.

Each lever 4 is provided at its free end with a cradle 7 formed of metal tabs welded on to it, the end of each lever being split to permit introduction of a lifting key 8. The keys 8 are threaded along their lengths, and each carries a threaded boss 9 which can locate in the cradle 7, and a threaded cap 10 in which is seated a helical spring 11. At its upper end, each key has a cross grip 12, while at the lower end it is provided with a formation 13 (see Figs 2 and 3) for engagement in the socket in the cover 14 to be lifted.

In use, the keys 8 are first located in the lifting holes in the cover 14, the springs 11 serving to hold the end formations on the keys firmly in place in the lifting holes. The device is then positioned over the cover so that the levers 4 can be aligned with the keys, sliding the levers 4 along the bar 1 as necessary. The metal tabs forming the cradle 7 are of such a height as to ensure that there is a small clearance between the bosses 9 and the levers 3 as the bosses are located over the tabs and into the cradles, so that, as downward force is applied to the handle 5, the levers 3 strike a blow to the undersides of the bosses 9. The blow is transmitted through the keys 8 to the lifting holes in the cover 14, again as an upward force, tending to loosen the cover from its seating 15.Continued downward force on the handle 5, following immediately from the blow on the cover, causes the cover to lift out of its seating, and it can then be wheeled to one side of the manhole, for replacement after the inspection or work in the manhole has been completed In this way, a single worker can lift and move the cover.

Referring now to Figures 2 and 3, a modified version of the device is used to handle heavier covers, for example those which normally require four workers to lift, each with a separate key. The device is generally the same as that described with reference to Figure 1, and corresponding parts bear the same reference numerals. Each cradle 7 has a short tube 20 welded therein, the tubes 20 carrying between them a rotatable shaft 21 from which extends a second shaft 22. A cross-beam 23 has a socket 24 welded thereto at its mid-point, the socket containing a short compression spring (not shown) in its base to provide a small clearance 25 (Fig 3) at rest. This clearance ensures the hammer effect when the handle 5 is pushed down at the start of the lifting operation, as hereinbefore described with reference to Figure 1. The cross-beam 23 is slotted and a pair of lifting keys 8 are slidably mounted in the slot 26 (only one being shown in Figure 2 for the sake of clarity), with the bosses 9 located in the slot by means of a shaped tab to prevent rotation.

In use, the device is wheeled over the cover, and the keys 8 are then positioned over the lifting holes in the cover, sliding the levers 3 along the bar 1 and the keys along the cross-beams 23 to achieve this. The keys are engaged in the lifting holes, the springs 11 again serving to hold the keys in place. A sharp downward movement on the handle 5 serves to strike an upward blow on the cover through the four keys 8, and the continued downward movement of the handle 5 brings the cover out of its seating, enabling it to be wheeled away. Replacement of the cover is essentially the reverse of this operation, but without the sharp hammer-blow movement being necessary.

It will be appreciated that the device described with reference to Figures 2 and 3, while having four keys, can be used for covers having only two lifting holes, by using only one of the cross-beams, moved to a generally central position.

Claims (1)

1. A self-supported rectangular wheeled bar incorporating two laterally movable forks which can be located above the cover lifting holes, and which have two specially machined grooves at their leading edge to cradle the cross pieces of two self-supporting, spring-loaded, height-adjustable keys which lock securely into the cover's lifting holes and incorporating at its centre a socket which takes a four foot steel lever bar which the operator pulls down to apply pressure on the lifting keys.