Lifting device

Abstract

A lifting device 100 has a lifting beam 120 with legs 130, 135 at each end and an attachment means, possibly hooks 110, to attach to an article, such as a manhole cover. An elongate support 140 is piv

Description

Field of the Invention The present application relates to lifting devices, such as lifting devices for lifting manhole covers. Background to the Invention Manhole covers are often made of heavy cast iron or steel and can weigh between 25 and 150 kilograms, making them difficult and potentially dangerous to lift manually. As such, manhole lifting devices are widely used to facilitate safe lifting of such covers out of manholes when access is required, for example by utility workers, construction crews or municipal maintenance teams. These lifters include simple handle or lever based lifting tools as well as more advanced hydraulic manhole lifters, which may be preferred, particularly for heavier manhole covers. Hydraulic lifting devices for manhole covers typically comprise supports that are arranged in contact with the ground adjacent a manhole to be opened, one or more hooks for engaging 'pick holes' or 'rungs' on a cover of the manhole and a hydraulic piston configured to elevate the hooks relative to the supports, thereby lifting a manhole cover secured to the hooks. UK patent GB2370560B describes an example of such a lifting device, comprising a lifting beam with attachment means for engaging a manhole cover and a pump piston means, wherein in a first position of the pump piston means the attachment means is located for attachment to a manhole cover, and in a second position the attachment means is remote from the attachment position. Hydraulic manhole cover lifting devices will often utilise conventional hydraulic pump pistons, rams or jacks, with analogue controls such as relief valves. If these analogue controls are tampered with by an inexperienced user, or are inadvertently disturbed during rough handling of the lifting device, this can result in dangerous or sub-optimal performance of the lifting device. For example, a user might improperly modify a maximum pressure setting setting of a hydraulic jack such that it can generate greater force and lift heavier loads, but this can cause excess strain on the hydraulic components, potentially leading to failures such as ruptured seals, damaged cylinders, or even failure of the jack itself. This could result in the sudden dropping of a manhole cover, potentially causing serious injury. An aim of the present invention is to provide an improved means for lifting manhole covers which addresses the problems outlined above. Summary of the Invention According to a first aspect of the invention, there is provided a lifting device comprising: a lifting beam; means to attach an article for lifting to the lifting beam; a pair of legs extending from the lifting beam adjacent opposite ends thereof; an elongate support with a first end pivotably engaging a flat face of the lifting beam; a pump piston means with a piston body connected to the elongate support and a piston shaft pivotably engaging the flat face of the lifting beam such that extending the piston shaft upon actuation of the pump piston means rotates the elongate support relative to the flat face of the lifting beam and the pair of support legs so as to lift the lifting beam and the means to attach an article in use; and a pair of side walls extending from the elongate support on opposite sides of the pump piston means, the piston body being connected to the elongate support by the pair of side walls, wherein at least one of the pair of side walls extends from the elongate support and beyond the piston body so as to cover an adjacent portion of the piston body. In use, such a lifting device - and the lifting beam thereof - may be supported by the pair of legs and the elongate support, which together may define at least three points of contact with the ground. Extending the piston shaft rotates the elongate support relative to the flat face of the lifting beam and the pair of support legs, thereby lifting the lifting beam and attachment means thereon, allowing a manhole cover or other article attached to the lifting beam to be lifted by extending the pump piston means. Controlled, reliable and safe operation of the lifting device may depend upon controls on the piston body being correctly set during use. If these controls are incorrectly set - for example, due to a user tampering with the controls, or the controls being inadvertently disturbed when knocked during handling of the lifting device - this can result in sub-optimal or even dangerous performance of the pump piston means, and by extension of the lifting device in its entirety. Embodiments described herein comprise a pair of side walls which connect the piston body to the elongate support and at least one of which extends beyond the piston body so as to cover an adjacent portion of the piston body. At least one of the pair of walls extending beyond the piston body blocks access to the body and any controls thereon from that side of the piston body. Additionally, in order to prevent such controls could being mis-set in use if the side wall was removed - for example by a user tampering with the device or by damage inflicted on the device - the pump piston body is connected to the elongate support via the pair of side walls, therefore if this side wall was removed, the pump piston body would be disconnected from the elongate support thereby preventing operation of the lifting device. The device comprises a lifting beam with at least one flat face. In some embodiments, the lifting beam may have a polygonal cross section, such as a square cross section. Such a shape may facilitate the attachment of other elements - such as the lifting means and the legs - to the lifting beam, for example by allowing them to be connected thereto by corresponding polygonal collars fitted over the lifting beam. A polygonal cross section of lifting beam may also facilitate the application of a rotational torque to the beam by the extending piston pump means, in order to rotate the lifting beam and legs connected thereto relative to the elongate support. The lifting beam may be hollow. The device comprises means to attach an article for lifting to the lifting beam, which may be means to attach a manhole cover to the lifting beam. The attachment means may comprise one or more hooks, which may be configured to engage with 'pick holes' or 'rungs' on a manhole cover, and / or may be configured to engage with 'keys' inserted into corresponding holes in a manhole cover. Keys inserted into corresponding holes in the manhole cover may be attached thereto, for example by inserting a T-shaped end into a socket on the manhole cover and twisting it therein. Different keys may be used with different corresponding manhole covers. The attachment means may extend from the at least one flat face of the lifting beam. The attachment means may be a pair of attachment means, such as hooks, which may be provided on the lifting beam on opposite sides of the points where the elongate support and the piston shaft pivotably connect to the lifting beam, such that an article connected to both attachment means may be balanced when being lifted by rotation of said elongate support. The device comprises a pair of legs extending from the lifting beam adjacent opposite ends thereof. The legs may be parallel and may comprise wheeled ends to facilitate movement of the device in use. The legs may extend from the lifting beam at an angle approximately 135° to the at least one flat face of the lifting beam. The pair of legs may be separated by one meter or more along the length of the lifting beam, which may provide space for a manhole and manhole cover to fit beneath the lifting beam between the pair of legs in use. The pair of legs may comprise wheeled ends which may facilitate moving and positioning the lifting device. The device comprises an elongate support with a first end pivotably engaging a flat face of the lifting beam. The elongate support may define a third contact point of a tripod arrangement supporting the lifting device in use. The elongate support may comprise a second end configured to contact the ground or may comprise a third leg extending from at or adjacent to its second end. The second end of the elongate support, or the end of a third leg extending therefrom may be wheeled. Such a wheel may be a caster wheel to facilitate positioning of the device in use. In some embodiments the lifting device may further comprise a pulley handle or lanyard which may be connected to the second end of the elongate support, with which the lifting device may be pulled along a surface in use. The elongate support may consist of a single elongate strut or member or may be defined by a frame of multiple members such as a pair of members in a V-shaped arrangement with the two spaced apart ends defining the first end of the elongate support engaging the lifting beam and the two meeting ends defining the second end distal end of the elongate support. The device further comprises a pump piston means with a piston body connected to the elongate support and a piston shaft pivotably engaging the flat face of the lifting beam. In use, when the piston extends or retracts, the distance between where the piston body connects to the elongate support and where the piston shaft pivotably engages the flat face lifting beam lengthens or shortens relative to the fixed distance between where the piston body connects to the elongate support and where the elongate support pivotably engages with the flat face of the lifting beam, thereby rotating the lifting beam relative to the elongate support. Therefore, extending the shaft upon actuation of the pump piston means rotates the elongate support relative to the flat face of the lifting beam (about the pivotable connection therebetween). When the lifting device is arranged such that it is supported on a surface by the pair of support legs and the second end of the elongate support, this lifts the lifting beam relative to that surface. The piston shaft may pivotably engage the flat face of the lifting beam at a point offset from where the elongate support pivotably engages said face (or axis thereof) in a direction perpendicular to the length of the lifting beam. The elongate support and / or the piston shaft may pivotably engage the flat face of the lifting means with one or more hinges, such as hinges provided on a collar fitted over the lifting beam. In some embodiments, the elongate support and piston shaft may be disconnect-able from the lifting beam, which may facilitate disassembly of the lifting device for transport or storage. The piston pump means may be a hydraulic piston pump means such as a hydraulic jack. The piston pump means may be arranged above the elongate support in use. The piston pump means may further comprise a pump handle, or socket for insertion of a handle or other elongate implement with which the piston pump means may be pumped to extend the piston shaft. Such a pump handle or socket may pivotably connect to the piston body, for example on an opposite side from elongate support, and / or above the piston body. The device may further comprise a socket or other means for holding an insertable pump handle when it is not inserted into pumping socket. The lifting device further comprises a pair of side walls extending from the elongate support on opposite sides of the pump piston means and connecting the piston body to the elongate support. At least one of the pair of side walls extends from the elongate support and beyond the piston body so as to cover an adjacent portion of the piston body. As described above, such side walls may block access to the body and any controls thereon and prevent the piston pump means from operating if said side walls are removed to provide access to the body and any controls thereon. In some embodiments, the at least one of the pair of side walls that extends beyond the piston body may extend laterally at least partially over the piston body of the pump piston means. Such an arrangement may further block access to the portion of pump body and any controls thereon from above in addition to from its side. In some embodiments, the piston body of the pump piston means is connected to the elongate support by a bar extending through the pair of side walls and through an aperture through the piston body of the piston pump means. Such an arrangement may ensure that the piston body is connected to the elongate support by both side walls and will not be secured to the elongate support if either side wall is removed. In some embodiments, the lifting device further comprises a handle connected to the pair of side walls. Such a handle may be used to carry or reposition the lifting device in use. In some embodiments, the handle is pivotally connected to the pair of side walls. Pivotably connecting the handle may allow it to fall or be lowered when not in use so that it does not obstruct actuation of the pump piston means by a user. Additionally, folding the handle down may allow the lifting device to occupy less space when not in use. In some embodiments, the handle is connected to the pair of side walls. Preferably, such a handle is connected to the pair of side walls by the bar connecting the pump piston body to the elongate support, wherein the handle is configured to rotate about an axis of the bar. Connecting the handle to the lifting device using the same bar that secures the piston body to the elongate support may simplify and / or accelerate construction of the lifting device by reducing a number of components necessary to provide all the necessary features. In some embodiments, the sole connection of the piston pump means to the elongate support is via the side walls. This may ensure that the piston pump means is disconnected if the side walls are removed, preventing them from being removed to expose access to the piston body and any controls thereon. In some embodiments, at least one of the pair of side walls is configured to block access to at least one control comprised by the piston body of the pump piston means. Access may be blocked to the controls along an axis parallel to the lifting beam of the device. In some embodiments, the lifting device further comprises a tamper proof cap on at least one control comprised by the piston body of the pump piston means. This may provide additional protection against tampering of the at least one control on the piston body, and / or may enable a user to observe when the at least one control has been moved from a default or initial setting. In some embodiments, the at least one control comprises a set screw. The at least one control may comprise a pressure regulator control, which may set a maximum pressure of the pump piston means. Above this pressure, hydraulic fluid may be recirculated by the piston pump means without exerting any further force. Setting such a maximum pressure may prevent overstressing of the pump piston means. For example, a pump piston means may utilise a hydraulic jack capable of exerting a pressure of up to two tonnes, but may be set to a maximum pressure of 800kg to prevent damage to the device and / or reduce risk of injury to a user. This maximum pressure control may be or may comprise a set screw. In some embodiments, the side walls are formed integrally with the elongate support. This may prevent them from being removed to expose the piston body. Brief Description of the Drawings Exemplary embodiments of the invention will now be described in detail with reference to the accompanying figures, in which: Fig. la shows an overall view of an embodiment of a lifting device in a first lowered arrangement; Fig. lb shows an overall view of the lifting device of Fig. la in a second raised arrangement; Fig. 2 shows a top-down view of the lifting device of Fig. la in the first lowered arrangement; Fig. 3 shows the lifting device of Fig. la partially disassembled; Fig. 4 shows a detailed side view of the piston pump means and the connections between the lifting beam and the elongate support and the piston pump means; Fig. 5 shows a detailed end view of piston pump means and the connection between the piston pump means and the elongate support provided by the side walls; Fig. 6 shows an alternative cross-sectional view of a piston body secured to an elongate support by a pair of side walls and a bolt extending therethrough; and Fig. 7 shows an alternative lifting device with a longer lifting bar. Detailed Description Referring to the figures generally, there are shown embodiments of a device 100 for lifting manhole covers. The device comprises a pair of spaced apart hooks 110 for attaching to keys which engage with the manhole cover. The hooks 110 are supported on a lifting beam 120 which is raised and lowered in use. The lifting beam 120 is supported by first and second legs 130, 135 which extend from points adjacent its two ends and by an elongate support 140, a first end of which pivotably connects to a midpoint of the lifting beam 120 and a second end of which has a third leg 150 extending therefrom. The first, second and third legs 130, 135, 150 together define a triangular base of support for the device 100 and the lifting beam 120 thereof. The first, second and third legs 130, 135, 150 are wheeled to facilitate movement and positioning of the lifting device 100. In use, as the elongate support 140 rotates relative lifting beam 120, it also rotates relative to the first and second legs 130, 135, thereby displacing the lifting beam 120 relative to a surface supporting the device 100. Figs, la and lb show the device 100 with the lifting device in a first lowered and second raised arrangements respectively. Fig. 2 shows a top-down view of the lifting device in the lowered arrangement. In the raised arrangement, the lifting beam 120 is elevated by approximately 0.34 meters from a ground surface supporting the lifting device, resulting in sufficient clearance between the base of a manhole cover secured to the hooks 110 via keys and the ground surface to allow the manhole cover to be moved away from the manhole and then lowered to the ground surface. It will be appreciated that in order to attach to a recessed manhole cover below ground level, the elongate support may be rotated further from the raised arrangement than is shown in Fig. la, in order to lower the hooks 110 below a ground surface supporting the three legs 130, 135, 150. The device 100 comprises a pump piston means 160 for rotating the elongate support relative to the lifting beam 120 and thereby raising the lifting beam 120 and any manhole cover secured thereto by the hooks 110. The pump piston means 160 is connected to the elongate support by a pair of side walls 170, 175, one of which extends above a body of the pump piston means to obstruct access thereto. The device further comprises a T-shaped handle 180 rotatably connected to the second end of the elongate support 140 for pulling the lifting device 100 across a surface, and a looped handle 185 rotatably connected to the side walls 170, 175 for carrying the lifting device. Fig. 3 shows the lifting device 100 partially disassembled, with the first and second legs 130, 135, the hooks 110, the elongate support 140 and the pump piston means 160 disconnected from the lifting beam 120. The lifting beam 120 has a hollow square cross-section. The first and second legs 130, 135 are each detachably secured adjacent opposite ends of the beam by means of a square sleeve portion that fits over the lifting beam and a screw clamp that tightens said sleeve onto the lifting beam. Each of the first and second legs 130, 135 comprises a pair of parallel lengths which extend from the sleeve portion and a wheel between said lengths at their ends distal from the sleeve portion. When secured to the lifting beam 120, the wheels of the legs 130, 135 rotate about an axis parallel thereto. The two hooks 110 which are each provided on an associated square sleeve which fits over the lifting beam 120 between the sleeve of one of the first and second legs 130, 135 and a sleeve for connecting the elongate support 140 and pump piston means 160 to the lifting beam 120. The hooks are arranged to extend from a first flat face of the lifting beam 120, to which the elongate support 140 and a shaft of the pump piston means 160 are also connected. The elongate shaft 140 and the piston pump means 160 are also connected to the first flat face of the lifting beam 120. Fig. 4 is a detailed side view of the piston pump means 160 and the connections 122, 124 between the lifting beam 120 and the elongate support 140 and the piston pump means 160. The first end of the elongate support 140 is connected the first face of the lifting beam 120 by a first hinge 122, allowing the elongate support to rotate relative to lifting beam 120 and the first and second legs 130, 135 connected thereto, such that the lifting device 100 moves between the lowered and elevated arrangements shown in Figs, la and lb respectively. The second distal end of the elongate support supports the third leg 150, which is defined by a caster wheel to facilitate movement and positioning of the lifting device, and the T-shaped handle 180 with which the lifting device may be pulled into position. The piston pump means 160 comprises a piston body 162, a piston shaft 164, and a pump handle socket 166. The piston body 162 is connected to the elongate support 140 by a bolt 172 that extends through the first side wall 170, through the piston body 162 and through the second side wall 175. An end of the piston shaft 164 distal from the piston body 162 is connected to the first face of the lifting beam 120 by a second hinge 124. The second hinge 124 is offset from the first hinge 122 in a direction perpendicular to the lifting beam 120. As such when piston shaft 164 extends from or retracts into the piston body 162, the second hinge 124 is displaced, causing the second hinge 122, the lifting beam 120, and the hooks 110 and legs 130, 135 connected thereto to rotate relative to the elongate support 140 about the axis of the first hinge 122. Extending the piston shaft 164 thereby moves the lifting device 100 from the lowered arrangement shown in Fig. la towards the raised arrangement shown in Fig. lb and retracting the piston shaft 164 does the opposite. The first and second hinges 122, 124 are provided on a square sleeve which fits over the lifting beam 120 between the two hooks 110. The piston shaft 164 may be extended by inserting a pump handle or other suitable elongate element into the pump handle socket 166, which is provided on the exterior of the piston body 162 and pumping said handle or elongate element. When the pump handle is not inserted into the pump handle socket 166 it may be stowed adjacent the elongate support 140 by inserting it into a receiving socket thereon, as shown in Fig. 2. Fig. 5 is a detailed end view of the piston pump means 160 and of the connection between the piston pump means 160 and the elongate support provided by the side walls 170, 175, as viewed from an end opposite the piston shaft 164. The device comprises a first side wall 170 and a second side wall 175 which extend upwards from the elongate support adjacent the end of the piston body 162 opposite the piston shaft 162. The piston body 162 is connected to the elongate shaft via bolt 172 which extends through the first side wall 170, through the piston body 162 and through the second side wall 175. The first and second side walls 170, 175 are welded to the elongate support 140 such that they are not removable therefrom. The first sidewall 170 extends from the elongate support beyond the piston body 162 such that it covers a portion of the piston body 162 when viewed along an axis parallel to the lifting beam 120. An upper portion of the first sidewall further extends laterally partially over the piston body 162. In other embodiments, both sidewalls may extend from the elongate support beyond the piston body so as to cover a portion of the piston body 162 on both its sides. Moreover, one or both of such sidewalls may extend laterally partially over the piston body 162 and a set screw 168 thereon. The portion of the piston body 162 covered by the first sidewall 170 comprises a set screw control 168 for a maximum pressure of the piston pump means 160, provided on a side of the piston body 164 covered by the first sidewall 170. This set screw sets a maximum pressure of the piston pump means, and by extension a maximum lifting force of the lifting device. The first sidewall acts to restrict a user from easily tampering with the set screw control 168 and / or to prevent the set screw control 168 from being accidentally disturbed from a desired position by contact with an object in the environment. The pump piston means 160 is connected to the elongate support 140 via the first sidewall such that it cannot be removed to expose the set screw control 168 without preventing the lifting device 100 from functioning. The set screw 168 has a rubber tamper proof cap glued thereon which allows a user to observe if the set screw 168 has been moved from its default setting. The rear of the piston body 162 comprises a pressure relief valve 169 which may be turned by a user in use to release pressure from the piston pump means and thereby lower the lifting beam 120, the hooks 110 thereon and any manhole cover being lifted by the device 100. In some examples, the pump handle for inserting into the socket 166 may also be configured to fit onto the pressure relief valve 169 to turn it and release pressure in use. The looped handle 185 is rotatably connected to the lifting device using the same bolt 172 as the piston body 162, thereby simplifying manufacturing of the lifting device 100. Fig. 6 shows an alternative cross-sectional view of a piston body 162 secured to an elongate support 140 by a pair of side walls 170, 175 and a bolt extending therethrough. 5 Fig. 7 shows an overall view of an alternative lifting device with a longer lifting beam 120 than the device shown in Figs. 1 to 5. It will be appreciated that the other components of these lifting devices may be interchangeable, and a single lifting device may be used with various lifting beams 120 of different lengths, which may enable it to be used with different sized manhole covers. 10 It will be appreciated that variation may be made to the illustrated embodiments described above without departing from the scope of the invention as defined by the claims.

Claims

1. A lifting device comprising:a lifting beam;means to attach an article for lifting to the lifting beam;a pair of legs extending from the lifting beam adjacent opposite ends thereof;an elongate support with a first end pivotably engaging a flat face of the lifting beam;a pump piston means with a piston body connected to the elongate support and a piston shaft pivotably engaging the flat face of the lifting beam such that extending the piston shaft upon actuation of the pump piston means rotates the elongate support relative to the flat face of the lifting beam and the pair of support legs so as to lift the lifting beam and the means to attach an article in use; anda pair of side walls extending from the elongate support on opposite sides of the pump piston means, the piston body being connected to the elongate support by the pair of side walls, wherein at least one of the pair of side walls extends from the elongate support and beyond the piston body so as to cover an adjacent portion of the piston body.

2. A lifting device according to claim 1 wherein the at least one of the pair of side walls extends laterally at least partially over the piston body.

3. A lifting device according to any preceding claim wherein the piston body is connected to the elongate support by a bar extending through the pair of side walls and through an aperture through the piston body.

4. A lifting device according to any preceding claim further comprising a handle connected to the pair of side walls.

5. A lifting device according to claim 4 wherein the handle is pivotally connected to the pair of side walls.

6. A lifting device according to claim 5 when dependent on claims 3 and 4 wherein the handle is connected to the pair of side walls by the bar connecting the piston body to the elongate support, wherein the handle is configured to rotate about an axis of the bar.

7. A lifting device according to any of claims 3 to 6 wherein sole connection of the piston pump means to the elongate support is via the side walls.

8. A lifting device according to any preceding claim wherein at least one of the pair of side walls is configured to block access to at least one control comprised by the piston body.5 9. A lifting device according to any preceding claim further comprising a tamper proofcap on at least one control comprised by the piston body.

10. A lifting device according to either claim 8 or claim 9 wherein the at least one control comprises a set screw.

011. A lifting device according to any preceding claim wherein the side walls are formed integrally with the elongate support.

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