GB2311055A - Manhole cover lifting devices - Google Patents

Abstract

A device for lifting socketed manhole covers comprises at least one socket engaging key and a wheeled trolley 4, 5 with a lever arm 7 extending rearwardly and an attachment device 9, 10 for a key extending forwardly. The attachment device may comprise two spaced plates 9 terminating in hooks 10 which engage a threaded bar of a lifting key. Alternatively, the attachment device may comprise a bar (110, Figure 11) lying parallel to a rotational axis of the trolley and hooks on the lifting key are adapted to engage the bar. In a further embodiment, the lifting key may lie at one end of a framework (41, Figure 9) which also forms the lever arm handle. The device may be used in conjunction with a separate device (Figure 13) for breaking the seal about a manhole cover, the seal breaking device including at least one jacking screw for engagement with the ground adjacent the cover. A hydraulically powered lifting unit may assist in the lifting operation (Figure 15).

Description

A MANHOLE COVER LIFTER The present invention relates to manhole cover lifters.

The term "manhole cover" is a term used in this specification to encompass what are often referred to conventionally as manhole covers, but also junction box and access covers such as are used by telephone, electricity and other service companies and indeed any cover for a unit which is generally mounted flush in the ground and which has to be removed from time to time for inspection, filling or other work on the equipment stored in the manhole itself. Such manhole covers generally have lifting sockets which can be formed by protuberant lugs having holes, crossbars, lips, or other engagement means to permit them to be lifted out of their framework. Generally, however the lifting sockets are flush with the upper surface of the manhole covers and usually are provided by a re-entrant socket or sockets formed in the upper face thereof into which a key may be placed and rotated therein to allow a lifting force to be applied to the cover. Hereinafter in the specification, all these lifting means and lifting sockets are generally referred to as "sockets".

Accordingly, the present invention is concerned with a socketed manhole cover lifter of the type comprising a wheeled trolley adapted to engage a socket in a manhole cover for removal of the manhole cover.

With the advent of new Health and Safety regulations, there is increased emphasis on safety due to the knowledge that incorrect manual handling causes 25% to 30% of all industrial accidents. Injuries are generally caused to users' backs in particular and these are, in some ways, the most serious of all accidents, often not life threatening but considerably serious and in many cases incapacitating workers for years, if not for life.

This is exacerbated when manhole covers are being handled as they are generally heavy objects. Additionally, a manhole cover often remains in situ for many years so that it has become firmly fixed within its surrounding frame thus requiring considerable force to break the "seal". Very often, they can be leveraged upwards but unfortunately this well known way of lifting a manhole frequently causes back strain.

A number of devices and lifters have been developed which in some way have overcome some of the problems. These are often very elaborate lifters such as four-wheel manhole cover lifters whereby the device is wheeled over the manhole cover and the manhole cover is secured to the device. The manhole cover is then raised upwards and may be wheeled away from the manhole.

Another type of lifter comprises a cranked lever having gripping means which are attachable to the manhole cover, the lever is supported by wheels and a handle controls the leverage. Unfortunately, these are not particularly efficient in use. Superficially, they look as if they would handle the problem but in practice there are considerable difficulties.

What is needed is a manhole cover lifter that will be ergonomically designed on the fulcrum principle to reduce effort and energy needed for the removal, replacement and transporting away of the manhole cover. Unfortunately, not enough attention has been paid to these problems.

The present invention is directed towards providing an ergonomically sound manhole cover lifter of the aforesaid type which will be relatively effortless in use, safe and which will ensure that there is no risk of painful back strain for the user. Ideally, such a manhole cover lifter should be easily transportable, adaptable to a wide range of construction of manholes, and be easily operated.

Also an object of the invention is to provide a lifter which is easy to manipulate and engage with lifting keys attached to a manhole cover.

Statements of Invention The invention is defined in the appended claims which are incorporated into this description by reference thereto.

According to the present invention, there is provided a socketed manhole cover lifter of the type comprising a wheeled trolley adapted to engage a socket in a manhole cover characterised in that the lifter comprises a lever arm mounted on the trolley and terminated in an attachment device for engagement with a separate socket engaging lifting key.

Ideally, the lever arm carries a transverse support bar substantially parallel to the wheel axis on which the attachment devices are mounted. Ideally, the attachment devices are slidable towards and away from each other on the support bar. The advantage of this construction is that a plurality of lifting devices may be mounted on the lever arm and additionally, by varying the spacing, it is possible to accommodate different sizes and constructions of manhole cover. The support bar may conveniently form the wheel axis.

In one embodiment of the invention, the socket engaging portion of the lifting key is spring biased into engagement with the socket. The advantage in this is that when the lifting key is placed in position, it will stay in position until the manhole cover lifter is offered up to it.

Ideally, the lifting key comprises a base sleeve having a bar slidably mounted therein, carrying on one side of the sleeve a socket engaging portion and on the other side engagement means for the attachment device, the socket engaging portion being spring biased towards contact with the sleeve. This particular construction is particularly effective and efficient in use. In the latter type of lifting key, the bar may be threaded and a spring mounted thereon to embrace the bar between the sleeve, and a threaded nut on the bar between the engagement means and the sleeve. This allows the spring force to be varied at will.

In another aspect of the invention, there is provided a manhole cover lifter for manhole covers having a re-entrant socket of the type adapted to receive a lifting key in the form of a Tee shaped bar and to engage the lifting key on rotation of the bar within the socket, the manhole cover lifter being of the type comprising a wheeled trolley carrying a lever arm characterised in that the lever arm terminates in a lifting key.

The present invention further provides a socketed manhole cover lifter of the type comprising a wheeled trolley adapted to engage a socket in the manhole cover characterised in that the lifter comprises a lever arm mounted on the trolley and terminating in a lifting rod which is parallel to the rotational axis of the trolley, the lifting bar being adapted to engage a socket engaging lifting key.

Advantageously, the socket engaging lifting key has a hooked end remote from the socket engaging end, the hooked end being adaptable to be engaged by the lifting bar of the trolley. Thus, once the hooked end of the keys face towards the trolley, it is a relatively simple matter for the lifting bar to engage with the hooks.

Conveniently, a jacking screw is provided on the lifter for use as a seal breaking device for a manhole cover.

The invention also provides a manhole cover seal breaking device for use in conjunction with a manhole cover lifter comprising an elongate support having a slidably mounted socket engaging key, the key being lockable in position on the support and having means for securing the support against the surface of the manhole cover, and a jack means being provided on the support remote from the key, the jack means being engageable against a surface adjacent the manhole cover so that as force is applied by the jack means, the manhole cover is slowly moved from it seating so as to break the "cover seal".

Detailed Description of the Invention The invention will be more clearly understood from the following description of some embodiments thereof, given by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a socketed manhole cover lifter according to the invention about to be offered up to a manhole cover; Figure 2 is a perspective view of a separate socket engaging lifting key and portion of a manhole cover; Figure 3 is a side view of the lifter of Figure 1 in engagement with the lifting key of Figure 2; Figure 4 is a side view similar to Figure 3 showing the manhole cover lifted; Figure 5 is a perspective view similar to Figure 1 of an alternative construction of lifter according to the invention; Figure 6 is a perspective view of a socket engaging lifting key used with the lifter of Figure 5; Figure 7 is a perspective view of the lifter of Figure 5 in the partly disassembled position; Figure 8 is a perspective view of an alternative construction of lifter according to the invention being offered up to a manhole cover; Figure 9 is a perspective view of the lifter of Figure 8 engaged in a manhole cover; Figure 10 is a perspective view of the lifter of Figures 8 and 9 transporting a manhole cover; Figure 11 is a perspective view from the front of another embodiment of the socketed manhole cover lifter attached to a manhole cover for a lifting operation with a pair of socket engaging lifting keys engaged with the cover; Figure 12 is a perspective view of one of the lifting keys shown in Figure 1 1; Figure 13 is a perspective view from the rear of the manhole cover lifter with a seal breaking element fitted to the lifter; Figure 14 is a perspective view of a separate seal breaker which can be used in conjunction with the lifter; and Figure 15 is a perspective view of a hydraulically powered embodiment of manhole cover lifter and seal breaker.

Referring to the drawings and initially to Figures 1 to 4 thereof, there is illustrated a socketed manhole cover lifter, indicated generally by the reference numeral 1, and a manhole cover 2 having a socket 3 formed from a transverse slot. The lifter 1 comprises a transverse support bar 4 of square cross section carrying a pair of ground engaging wheels 5. Mounted intermediate the wheels 5 on a fixed sleeve 6 is a cranked lever arm 7 terminating in a transverse handle 8. Mounted on the support bar 4 are a pair of attachment devices formed from two spaced-apart plates 9 terminating in hooks 10. The attachment devices are slidable transversely on the support bar 4.

Referring specifically to Figure 2, there is illustrated a separate socket engaging lifting key, indicated generally by the reference numeral 20 which comprises a threaded bar 21 terminating in a socket engaging Tee piece 22 and having a handle 23. Mounted on the bar 21 is a sleeve 24 carrying a collar 25. The exterior of the sleeve 24 carries a spring 26 and thus only portion of the sleeve 24 can be seen in Figure 2. A spring stop formed from a threaded collar 27 is mounted on the threaded bar 21. Above the threaded collar 27 is a further transverse hook engaging bar 28 which has a threaded bore 29 so that it may be adjusted in height on the threaded bar 21.

In use, the lifting keys 20 are inserted into the sockets 3. It will be seen from Figure 2 that before being inserted into the socket 3, the spring 26 is relatively loose on the lifting key 20.

When the Tee piece 22 is inserted into the socket 3, the handle 23 is pushed downwards and rotated so that the Tee piece 22 projects through the socket 3 and then beneath the cover 2.

This causes the spring to bear against the threaded collar 27 and thus the Tee piece 22 is secured in position in the manhole cover 2 and will stand upright as illustrated in Figure 1.

Then the attachment devices are moved transversely on the support bar 4 so that the hooks 10 can engage on either side of the threaded bar 7 of each lifting key 20. This is illustrated quite clearly in Figure 3. Pivoting downwards of the handle 8 will cause the hooks 10 to pivot upwards lifting the manhole cover 2 upwards. Then the manhole cover 2 can be transported to a suitable rest position.

Referring to Figures 5 to 7, there is illustrated a socketed manhole cover lifter indicated generally by the reference numeral 30. Parts similar to those described with reference to the previous drawings are identified by the same reference numerals. In this embodiment, there is illustrated a rectangular manhole cover 31. In this embodiment, there is a straight lever arm 32 of two piece construction as shown by the screw-socket connector 33 which allows disassembly of the lever arm 32 which facilitates transporting.

Referring to Figures 8 to 10, there is illustrated an altemative construction of manhole cover lifter, indicated generally by the reference numeral 40. This manhole cover lifter 40 is specifically designed for manhole covers having a re-entrant socket of the type adapted to receive a lifting key in the form of a Tee shaped bar, such as illustrated already with respect to the previous embodiments. These are adapted as already described to engage the lifting key on rotation of the bar within the socket. In this embodiment, the manhole lifter 40 comprises a framework 41 forming a lever arm mounted on a pair of wheels 42 terminating at one end in a handle 43 and at its other end in a lifting key formed from a Tee shaped bar 44.

In use, to lift a manhole cover 45 having sockets 46, the lifter 40 is wheeled over the manhole 45 as illustrated in Figure 8, and the handle 43 is pivoted upwards about the wheels 42 to engage the Tee shape bar 44 in a socket 46. As the handle 43 is pivoted, the Tee shape bar 44 penetrates the socket 46 and may then be rotated therein possibly with the wheels lifting slightly to the position illustrated in Figure 9. In the position illustrated in Figure 9, as can be seen from Figure 10, the handle may then be pivoted downwards and the manhole cover 45 lifted. This lifter, according to the invention, may be particularly useful for breaking the seal on light manholes which are not difficult to transport but are often heavily sealed into the ground.

It will be appreciated that while in all the embodiments above, the lifting keys have been illustrated as being of one particular construction, that any suitable construction of lifting key may be used and that the lifter according to the invention can be easily adapted to engage them.

Referring to Figures 11 to 13, there is illustrated a socketed manhole cover lifter, indicated generally by the reference numeral 101, and a manhole cover 102 having a socket 103 formed from a transverse slot. The lifter 101 comprises a transverse support bar 104 of square cross section carrying a pair of ground engaging wheels 105. Mounted intermediate the wheels 105 on a socket 106 is a cranked lever arm 107 terminating in a transverse handle 108. Mounted on the support bar 104 are three arms 109 which support a lifting bar 110 which is parallel to the rotational axis of the wheels 105. The end 107a of the handle 107 engages with the socket 106 by a bayonet connection 111. A spring 112 and a retaining ring 113 are fitted on the handle to maintain the bayonet connection. The handle 107 is removable from the socket 108 to facilitate storage and transportation of the lifter when not in use.

Referring specifically to Figure 12, there is illustrated a separate socket engaging lifting key, indicated generally by the reference numeral 120 which comprises a threaded barrel 121 terminating in a lifting hook 122. Engaging the barrel 121 is a threaded rod 124 which carries a lock nut 125. The exterior of the rod 124 carries a spring 126 and the rod 124 has a locating key element 128. The barrel 121 can be screwed relative to the rod 124 to adjust the height of the key 120.

In use, the lifting keys 120 are inserted into the sockets 103. Before being inserted into the socket 103, the spring 126 is relatively loose on the lifting key 120. When the locating key element 128 is inserted into the socket 103, the barrel 121is pushed downwards and rotated so that the key element 128 projects through the socket 103 and then beneath the cover 102. This causes the spring to bear against the lock nut 125 and thus the key element 128 is secured in position in the manhole cover 102 and will stand upright as illustrated in Figure 11. Then the lifting rod 110 of the lifter is engaged with the two hooks 122. This is illustrated quite clearly in Figure 11. Pivoting downwards of the handle 108 will cause the lifter rod 110 to pivot upwards lifting the manhole cover 102 upwards about the rotational axis of the wheels 105. The wheels 105 can be provided with stops (not shown) if necessary to facilitate this levering action. Then the manhole cover 102 can be transported to a suitable rest position.

In the modification shown in Figure 13, ajacking screw 115 is fitted in a threaded lug 116 fixed to one of the arms 109. With the keys 120 in position in sockets 103, the jacking screw 115 is screwed downwardly until it contacts the ground adjacent the manhole cover.

Further tightening of the jacking screw 115 will cause breakage of the seal surrounding the manhole cover. After the seal has been broken, the manhole cover can be removed by the lifter.

Seal breaker 130 is shown in Figure 13 and comprises a support 131, a jacking screw 132 and a slidable socket engaging lifting key 133. The support 131 has a pair of bars 134 spaced apart by two blocks 135. The jacking screw 132 is in screw threaded engagement with one of the blocks 135 and has a T-shaped handle 136. The key 133 has a socket engaging element 137, a T-shaped handle 138 and is in screw threaded engagement with a lug 139 which can be moved along the upper surface of bars 134 to allow alignment with the socket of a manhole cover. When the key is secured in the socket, the jacking screw 132 is tightened against the ground or surface adjacent the manhole until the seal of the manhole is broken. A seal invariably forms about a manhole cover which has not have been lifted for some time. After the seal has been broken, the manhole cover lifter 101 is then used to lift the cover.

Referring to Figure 15, the hydraulically powered unit 150, comprises a hydraulic cylinder 151, a pivot lifting bar arrangement 152 and a solid lifting bar 153 which is engageable with hooks 154 provided on manhole cover lifting bars 155. Each of the manhole cover lifting bars 155 is provided with two cover lifting keys 156. The unit 150 is mounted on a pair of wheels 157 and a central arm 158 having a leading wheel 159.

It will of course be understood that the invention is not limited to the specific details described herein, which are given by way of example only, and that various modifications and alterations are possible within the scope of the invention as defined in the appended claims.

Claims (10)

CLAIMS:

1. A socketed manhole cover lifting device comprising at least one socket engaging lifting key, a wheeled trolley adapted to be positioned adjacent a manhole cover, a lever arm mounted on the trolley and extending rearwardly therefrom, a separate attachment device for each key mounted on the trolley and extending forwardly therefrom, each attachment device being formed from two spaced apart plates terminating in hooks.

2. A socketed manhole cover lifting device as claimed in Claim 1, in which the trolley comprises a transverse support bar which is substantially parallel to the wheel axis of the trolley, with the transverse support bar carrying the lever arm and attachment devices.

3. A socketed manhole cover lifting device as claimed in Claim 2, in which the attachment devices are slidably mounted on the support bar so that they may be moved towards or away from the centre of the support bar.

4. A socketed manhole cover lifting device as claimed in Claim 2 or Claim 3, in which the support bar forms the wheel axis.

5. A socketed manhole cover lifting device comprising at least one socket engaging lifting key, a wheeled trolley adapted to be positioned adjacent a manhole cover, a lever arm mounted on the trolley and extending rearwardly therefrom, an attachment lifting bar for the socket engaging lifting keys extending forwardly of the trolley, the lifting bar being parallel to a rotational axis of the trolley with each socket engaging lifting key having a socket engaging end and hooked end remote from the socket engaging end, with the hooked end being adapted to be engaged by the lifting bar of the trolley.

6. A socketed manhole cover lifting device as claimed in any one of the preceding claims, in which the lever arm is removably engageable with the trolley.

7. A socketed manhole cover lifting device as claimed in Claim 6, including a bayonet connection between the lever arm and the trolley.

8. A socketed manhole cover lifting device as claimed in any one of the preceding claim, which includes a separate device for breaking the seal about a manhole cover, the seal breaking device including at least one jacking screw for engagement with the ground adjacent the manhole cover.

9. A socketed manhole cover lifting device as claimed in any one of the preceding claims, including a hydraulically powered lifting unit operable to assist in the lifting operation.

10. A socketed manhole cover lifting device substantially in accordance with any of the embodiments as herein described with reference to and as shown in the accompanying drawings.