GB2133444A

GB2133444A - Lifting manhole covers

Info

Publication number: GB2133444A
Application number: GB08331734A
Authority: GB
Inventors: Derek Ferns
Original assignee: SELFLEVEL COVERS AG
Current assignee: SELFLEVEL COVERS AG
Priority date: 1982-11-27
Filing date: 1983-11-28
Publication date: 1984-07-25
Also published as: SE8306559D0; DK152989B; AU557084B2; JPH0317006B2; SE8306559L; AU2173283A; GB8331734D0; CH655751A5; NL8304077A; NO834373L; SE449763B; DK152989C; IE832784L; IE54783B1; DE3343003A1; JPS59150833A; GB2133444B; DK543183A; DK543183D0

Abstract

In a manhole or access cover having at least one recess into which a key or other implement can be inserted to enable the cover to be lifted or levered from its frame, the recess comprises two undercut apertures 16, 17 of different depth with a step 14 between them, and a crossbar 15 extending across the mouth of the recess at a location spaced above the step. The crossbar 15 has a rebate on its underside. The specification illustrates a variety of known lifting tools for which the recess is suitable-namely (a) a rod having opposed rectangular ears for quarter-turn interlock; (b) the hooked bar 24 shown; (c) a pair of inter-pivoted caliper arms; (d) two forms of lifting lever or handle which are clamped to the cover by screw- threaded means; (e) a pick-axe head. <IMAGE>

Description

SPECIFICATION Improvement in or relating to manhole or access covers The invention relates to manhole or access covers. The invention is particularly applicable to covers formed from cast-iron, but it is not limited to such covers.

Manhole covers are normally provided with a number of keyholes into which a key or similar implement may be inserted for the purpose of lifting or levering the cover from its frame.

Although there is a British Standard for keys and keyholes for manhole covers this is often not adhered to by manufacturers and a cover supplied by a particular manufacturer will often require a deisgn of key which is exclusive to that type of cover. Consequently, users of large quantities of covers, such as local authorities and water boards, usually require to provide each of their operatives with a multitude of different keys so that they will have a suitable key for each type of cover which they may encounter. In some cases, however, the operative may not have a particular key and may have to improvise means for lifting the cover, for example by inserting the end of a pickaxe into the keyhole.

The present invention provides a design of keyhole, for a manhole or similar access cover, with which may be used any of a number of different types of keys currently employed so that an operative having any one of a number of different available keys will still be able to lift the cover. At the same time, the design is such that even if no particular key is available it will still be possible to lift the cover using pickaxe if required.

According to the invention there is provided a manhole or access cover having at least one keyhole into which an implement can be inserted for the purpose of levering the cover from its frame, wherein the keyhole comprises a recess in the upper surface of the cover, which recess comprises two portions of different depth with a step between them and a crossbar extending across the mouth of the recess at a location spaced above the step.

It is found that a suitably sized keyhole of this configuration will co-operate with a number of different currently available keys to enable the cover to be lifted.

The keyhole may be provided with a number of further specific features to increase the number of available keys with which it may be used. The crossbar may be formed with a rebate along one lower edge thereof which faces into one portion, preferably the shallower portion, of the recess.

The lower edge of the crossbar which faces away from the rebate is preferably smoothly curved.

Preferably part of the crossbar projects into each portion of the recess. In the case where the cross-bar is formed with a rebate, the rebate preferably lies substantially wholly within the portion of the recess into which it faces.

The shallower portion of the recess may be narrower and/or shorter than the deeper portion.

The mouth of either or each recess portion may be defined by an aperture which is narrower in one dimension than the recess portion so that the aperture is bounded, on opposite sides thereof, by flanges which partly overlie the recess portion.

Each said aperture is preferably elongate with straight parallel sides and rounded ends.

The following is a detailed description of a preferred embodiment of the invention, by way of example, reference being made to the accompanying drawings in which: Figure 1 is a plan view of one corner of a castiron manhole cover showing a keyhole at that corner, Figure 2 is a longitudinal section through the keyhole showing a British Standard key cooperating therewith, Figure 3 is a section along the line 3-3 of Figure 2, Figure 4 to 7 are similar views to Figure 2 showing the application of various currently available types of lifting key to the keyhole, and Figure 8 is a similar view to Figure 2 showing how a pickaxe might be used to lift the cover when a suitable key is not available.

Referring to Figures 1 and 2, a keyhole 10 is integrally cast in each corner of a cast-iron manhole cover 11. The keyhole comprises a recess in the upper surface of the cover comprising two portions 12 and 1 3 of different depths with a step 14 between the two portions.

A crossbar 1 5 extends across the mouth of the recess at a location above the step 1 5 so as to provide on either side of the crossbar 1 5, apertures 1 6 and 17 leading to the portions 12 and 13 of the recess respectively. The apertures 16 and 17 are parallel sided with rounded ends and are narrower than their respective recess portions so that, as best seen in Figure 3, there are provided two inwardly turned flanges 1 8 overlying the larger recess portion 1 3 and similar flanges overlying the sides of the smaller recess portion 12.

The crossbar 15, which also has rounded sides as viewed in plan is formed on its underside with a rebate 1 9 facing towards the smaller recess portion 1 2 and is smoothed curved, as indicated at 20, on the portion thereof facing the larger recess portion 1 3. The rebate lies substantially wholly within the smaller recess portion 12.

Figures 2 and 3 show a British Standard key 21 which comprises a cylindrical metal rod 22 to one end of which are welded diammetrically opposed rectangular ears 23. The dimensions of the ears 23 are such that the end of the rod carrying the ears can be inserted in the aperture 1 7 with the ears extending longitudinally of the aperture. The key is then rotated through 900 to the position shown in Figures 2 and 3 where the ears 23 extend beneath the flanges 18, whereupon the corner of the cover can be lifted by lifting the rod.

Figure 4 shows a conventional hook-like lifting key 24. This may be inserted through the aperture 1 6, as shown in Figure 4, or through the aperture 17, and hooked beneath the crossbar 1 5. It is preferable for the hook to be inserted through the smaller aperture 1 6 as shown in Figure 4 since the key may then be wedged against the step 1 4 as shown. The key will then extend at an angle from the manhole cover so that it may be lifted by a levering operation rather than by a straight lift.

Figure 5 shows a caliper type lifting key 25 in which two substantially horizontal arms 26 and 27 are pivotally connected together by a bolt 28.

The arms 26 and 27 are integrally formed with limbs 29 and 30 respectively. One of the limbs, 30, of the key is plain whereas the other limb 29 is formed with a hooked portion 31 at its extremity.

The key is operated by lowering the extremities of the limbs 30 and 29 through the apertures 16 and 17 respectively and then closing the limbs towards one another by puiling upwards on the arms 26 and 27. The crossbar 1 5 is then trapped between the limbs 29 and 30 and hooked portion 31 so that the cover can be lifted.

Figure 6 shows a type of key known as a "Gloster" key. This comprises a bar 32 formed with a socket 33 at one end and a shoulder 34 at the other end. A hook 36 extends downwardly from the middle of the bar 32 and threaded eyebolts 37 and 38 pass transversely through the bar 32.

In operation the hook 36 is lowered through the larger aperture 1 7 and engaged beneath the crossbar 1 5. The eye-bolt 37 is then screwed down until a plug portion 39 thereon enters the smaller aperture 16 bringing an adjacent flange 40 into abutting engagement with the upper surface of the cover on either side of the apperature 1 6. As the eye-bolt 37 is screwed down further the shoulder 34 is brought into contact with the surface of the manhole cover and the hook 36 is levered upwardly firmiy into engagement with the crossbar 1 5 until the bar 32 is locked solidiy onto the manhole cover.

The eye-bolt 38 can be screwed down until its end engages a portion of the frame adjacent the edge of the cover. This applies upward leverage to the device to lever up the manhole cover. An extension arm (not shown) to give added leverage is inserted in the socket 33.

Figure 7 illustrates co-operation with the keyhole of a key known as a "Gatic" key. This consists of a thick steel plate 41 to which is welded a looped handle 42. Passing downwardly through the plate 41 is a bolt 43 carrying at its lower end a shaped key portion 44. In operation the key portion 44, suitably orientated, is lowered through the smaller aperture 1 6 into the shallower recess 12 and is secured within the recess by rotation of the bolt 43. A locking nut 45 encircles the bolt 43 above the plate 41 to prevent further rotation thereof. The manhole cover may then be lifted by lifting the handle 42.

Figure 5 shows how the end of a pickaxe, indicated at 46 or 47, may be inserted through either of the apertures 1 6 and 1 7 to provide leverage for lifting the manhole cover. In the case of the pickaxe head indicated at 46, it becomes wedged between the shoulder 14 and one end of the aperture 17, whereas in the case where the pickaxe is indicated at 47 it becomes wedged between the bottom corner of the recess portion 12 and the crossbar 15.

Claims

1. A manhole or access cover having a number of keyholes into which a key or other implement can be inserted for the purpose of levering the cover from its frame, wherein the keyhole comprises a recess in the upper surface of the cover, which recess comprises two portions of different depth with a step between them and a crossbar extending across the mouth of the recess at a location spaced above the step.

2. A manhole or access cover as claimed in claim 1 wherein the crossbar is formed with a rebate along one lower edge, the rebate facing into one portion of the recess

3. A manhole or access cover as claimed in claim 2 in which the rebate faces into the shallower recess portion.

4. A manhole or access cover as claimed in claim 2 or claim 3 in which the rebate lies substantially wholly within the portion of the recess into which it faces.

5. A manhole or access cover as claimed in any one of claims 2 to 4 in which the lower edge of the crossbar which faces away from the rebate is smoothly curved.

6. A manhole or access cover as claimed in any one of the preceding claims in which the crossbar extends into each portion of the recess.

7. A manhole or access cover as claimed in any one of the preceding claims in which the shallower portion of the recess is narrower and/or shorter than the deeper portion.

8. A manhole or access cover as claimed in any one of the preceding claims in which the mouth of at least one of the recess portions is provided with a mouth defined by an aperture narrower in one dimension that the recess portion, the aperture being thus bounded on opposite sides thereof by flanges which partly overlie the recess portion.

9. A manhole or access cover as claimed in claim 8 in which the aperture is elongate with straight parallel sides and rounded ends.

10. A manhole or access cover substantially as hereinbefore described with reference to and as shown in the accompanying drawings.