GB2060557A - Lifting device - Google Patents

Abstract

A lifting device, particularly for manhole covers, comprises a trolley (1) having a transverse member (10) supported by two cantilever arms (8, 9) from a frame (2, 3, 4) mounted on two wheels (5, 6), the member being parallel to the wheel axis (7). Two lifting hooks (11) are adjustable along the transverse member for engaging a load and a lever arm (12) projects upwardly at substantially 35 DEG from the opposite side of the trolley from the hooks such that pressure applied to the free end thereof pivots the trolley about the wheel axis to lift the load and allow its transportation. <IMAGE>

Description

SPECIFICATION Lifting device This invention relates to lifting devices, with particular reference to devices for lifting manhole covers and inspection plates.

The lifting of heavy manhole covers is a task which can impose a heavy strain on inspection workers, and in most cases would require at least two men to accomplish. A device for the singlehanded lifting of heavy manhole covers has been developed and is described in U.K. Patent Specification No. 1 268352. This device consists essentially of a three wheeled lifting frame incorporating a manually pumped hydraulic actuator by means of which lifting attachments can be raised to lift a manhole cover and consequently transport it.

Although the known hydraulically operated cover lifting devices are satisfactory, they are nevertheless cumbersome and expensive. An object of the present invention is to provide a lifting device which is of much simpler construction.

According to the invention there is provided a lifting device comprising a trolley having two coaxial ground wheels supporting a transverse frame member parallel to and spaced from the wheel axis, at least one lifting attachment carried by the frame member and a lever arm projecting from the trolley such that a downward force exerted at the free end of the lever arm, in use of the device, applies a lifting force to the lifting attachment, using the trolley wheels as a fulcrum.

Since the device has only two wheels and relies upon mechanical leverage rather than hydrauiic power to effect lifting of an object, such as a manhole cover, the device is essentially simpler in construction than the previously known lifting device referred to above. In use of the device, the wheels act as a fulcrum and, when the or each lifting attachment has been attached to the object to be lifted, downward pressure on the handle will exert a lifting force on the object. By providing a sufficiently long and rigid handle a sufficiently high mechanical advantage can be achieved to enable heavy objects such as manhole covers to be lifted by one man.Once the cover has been lifted it can be moved by the wheeled trolley away from the manhole by application of continuous downward pressure to the lever arm, the arm also being used to guide the movement of the trolley. The cover may be lowered to the ground at a convenient point to await replacement by means of the same lifting device.

The lifting device may have a single lifting attachment for lifting objects with a single central lifting point, but for the purpose of lifting manhole covers and inspection covers the trolley preferably has two lifting attachments which are adjustable in position along the transverse frame member.

For example one or both of the lifting attachments may be slidable along the transverse frame member to enable the lifting attachments to be aligned with two lifting points of a manhole cover.

Thus in one embodiment of the invention each lifting attachment comprises a hook for engagement with a lifting ring or bar of a manhole cover.

The transverse frame member of the device may be supported by a cantilever arm or arms projecting from a frame on which the trolley wheels are mounted. Preferably the said frame member is supported from a second transverse frame member parallel to and spaced from the wheel axis. The cantilever arm or arms would have sufficient length to enable the lifting attachment or attachments to engage a manhole cover or other object to be lifted while the wheels remain on the ground.

To facilitate carriage and storage of the device, the lever arm may be releasably attached to the trolley and/or collapsible; for example, it may fold, be formed in several releasable parts or be telescopic.

Two embodiments of the invention are illustrated, by way of example, in the accompanying purely diagrammatic drawings, in which: Figure 1 is a perspective view of a lifting device according to the invention, and Figure 2 is a side elevation of a lifting device similar to that of Figure 1, shown in use for the lifting of a manhole cover.

The lifting devices shown in Figures 1 and 2 are substantially identical apart from the construction of a lever arm 12 forming part of the device, which will be described in greater detail below. The devices comprise a trolley 1 constructed from rigid, steel, square-section tube and having a frame incorporating a transverse member 2 and two pairs of legs 3, 4 projecting downwardly from the ends thereof. Respective wheels 5, 6 are freely rotatably mounted between each pair of legs 3, 4, the wheel axes being co-axial with each other: the common wheel axis is indicated by a broken line 7 in Figure 1.

The two wheels 5, 6 may be fabricated in nylon.

Two cantilever arms 8, 9 project from opposite ends of the frame member 2 and support at their free ends a second transverse frame member 10 extending parallel to the member 2 and to the wheel axis 7.

Two lifting attachments 11 are carried on the second transverse frame member 10 and are slidable along the frame member 10. Each lifting attachment 11 comprises a hook or lifting key and may incorporate a swivel. Many known types of conventional lifting attachment may be used for engagement with the lifting rings or sockets of a manhole cover.

The lever arm 12 is rigidly attached to the trolley 1 by an end portion 1 2B and projects from the trolley, on the opposite side of the wheel axis 7 from the lifting attachments 11, at an upward inclination of 20--300, preferably 35 , to the horizontal when the cantilever arms 8, 9 are horizontal. The arm 12 is braced, in the embodiment of Figure 2, by a bracing member 13 connected to the frame 2 and a strut extending between the frame member 2 and the transverse member 10; in the embodiment of Figure 1 it is braced by a triangular steel plate 1 5.

The cantilever arms 8, 9 have a length which is slightly greater than the radius, or width, of the largest size of manhole cover which it is desired to lift by means of the device. The device is used very simply, as shown in Figure 2, by positioning the second transverse frame member 10 above the centre of a manhole cover C to be lifted and sliding the lifting attachment 11 along the transverse frame member 10 until the attachments 11 are aligned vertically with the lifting rings or sockets of the manhole cover C. The lifting attachments 11 are then engaged with the lifting rings or sockets of the manhole cover C, as shown diagrammatically in Figure 2 and, with the wheels 3, 4 resting on the surrounding ground, a downward pressure is applied to the lever arm 12, as indicated by the arrow F in Figure 2.The lever arm 12 and the elements 3,4 and 13 of the trolley frame act as a lever arm having as a fulcrum the wheel axis 7. The device rotates about this wheel axis, lifting the two lifting attachments 11 and the manhole cover C to which they are attached.

Once the manhole cover C has been lifted clear of the ground, the trolley is moved away from the manhole, downward pressure on the arm 12 being maintained; the manhole cover C is then carried to a convenient position where it may be lowered to the ground to await its replacement.

Since the lifting device according to the invention operates on the simple lever principle it is essentially simple in construction and is much more compact than the previously known hydraulic lifting devices referred to earlier.

To facilitate transportation of the lifting device the lever arm 12 is formed in two parts, a longer part 1 2A fitting into and being removable from the part 1 2B. The arm part 1 2A of the embodiment of Figure 1 is also formed in two portions 1 2C and 1 2D which are hinged together. A sleeve 14 carried by the part 1 2D is slidable between two positions, shown in broken outline and full outline respectively; in the position shown in broken outline in the sleeve surrounds the hinged joint to lock the two arm portions 12C, 12D together in their position of use in which they are coaxial.

With the sleeve in its position shown in full outline, the two arm portions may be folded together about the hinge for storage and, when removed from the part 1 2b can be attached to the frame member 2 by straps not shown.

A releasable pin 16 is also provided which seats in cooperating throughbores in the lever arm parts 1 2B and 1 2C to lock the parts together for use of the device. The free end of the lever arm 12 is also provided with a transverse hand grip 1 7.

Claims (7)

1. A lifting device comprising a trolley having two coaxial ground wheels supporting a transverse frame member parallel to and spaced from the wheel axis, at least one lifting attachment carried by the frame member and a lever arm projecting from the trolley such that a downward force exerted at the free end of the lever arm, in use of the device, applies a lifting force to the lifting attachment, using the trolley wheels as a fulcrum.

2. A lifting device as claimed in Claim 1, in which the or each lifting attachment is adjustable in position along the frame member.

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3. A lifting device as claimed in Claim 1 or Claim 2, in which the transverse frame member is supported by at least one cantilever arm from a second transverse frame member parallel to and spaced from the wheel axis.

4. A lifting device as claimed in Claim 2 or Claim 3, in which the lever arm projects upwardly from the trolley, in its position of use, at an angle of from substantially 200 to 300 to a plane containing the two transverse frame members.

5. A lifting device as claimed in any preceding claim in which the lever arm is releasably attached to the trolley.

6. A lifting device as claimed in any preceding claim in which the lever arm is collapsible.

7. A lifting device substantially as herein described with reference to, and as shown in, Figure 1 or 2 of the drawings.