GB2192654A

GB2192654A - Hinged manhole cover having spring means to facilitate opening

Info

Publication number: GB2192654A
Application number: GB08617696A
Authority: GB
Inventors: Ivan Lee Robins
Original assignee: BRICKHOUSE DUDLEY Manufacturing
Current assignee: BRICKHOUSE DUDLEY Manufacturing
Priority date: 1986-07-19
Filing date: 1986-07-19
Publication date: 1988-01-20
Anticipated expiration: 2006-07-19
Also published as: GB2192654B; GB8617696D0

Abstract

A manhole cover and frame assembly comprises a frame (11) and a cover (12) receivable by the frame, the cover (12) being hinged relative to the frame (11) for movement between an open condition and a closed condition, a torsion spring acting between the cover and frame normally to bias the cover to an open condition, releasable locking means to maintain the cover in a closed condition against the face of the torsion spring (40), the longitudinal axis of the spring (40) being coincident with the hinge axis and the locking means being readily releasable from inside the assembly. <IMAGE>

Description

SPECIFICATION Improvements in or relating to manhole and like covers This invention relates to a cover and frame assembly hereinafter referred to as being "of the kind specified" comprising a frame adapted to be positioned above a manhole, sump, sewer, access opening or the like, and a cover receivable by the frame to close an opening afforded by the frame, the assembly in use lying in a horizontal or substantially horizontal orientation.

The cover and/or the frame may have an aperture or apertures in the side or upper surface or surfaces thereof to permit of drainage of water through the cover and/or frame into the opening, such as where the cover comprises a grating, or may be unapertured to completely close the opening and/or be in sealing engagement with the frame, such as where the cover comprises a manhole cover.

Cover and frame assemblies of the kind specified are known in which the cover is counterweighted so that on release of a latch, the cover is opened without effort being required.

Such assemblies are particularly used as escape hatches and the like where a man in an access opening beneath the cover, by releasing the latch, can escape from the opening without having to lift the cover from the frame.

Such conventional manhole cover and frame assemblies have been in use for about 50 years. However during that entire time a problem has arisen in that the counterweight mechanism takes up space within the manhole thereby requiring the cover and frame assembly and the manhole, to be enlarged to accommodate the counterweight mechanism.

Further, the counterweight of the mechanism needs to move downwardly under gravity in order to open the cover, which moving part can be hazardous to a man within the access opening, and of course any resistance to movement of the counterweight would hinder opening of the cover.

Accordingly it is an object of the present invention to provide a new or improved cover and frame assembly which overcomes or reduces the above mentioned problems.

According to one aspect of the invention we provide a cover and frame assembly of the kind specified, the cover being hinged relative to the frame for movement between an open condition and a closed condition, spring means acting between the cover and frame normally to bias the cover to an open condition, releasable locking means to maintain the cover in a closed condition against the force of the spring means.

Such a sping means can be accommodated in a very much smaller space than known counterweight mechanisms. There is no moving counterweight and thus the problems with assemblies having counterweight mechanisms are entirely overcome.

Preferably, the spring means is a torsion spring, one end of which may bear on the cover and the other end of which may bear on the frame. The torsion spring may be wound around a former, the axis of the spring coinciding with the hinge axis. For example, one end of the torsion spring may be received by a receiving means of the frame on which the end bears, for example in a base wall of the frame, whereas the other end of the torsion spring may simply bear on the underside of the cover.

In a preferred embodiment, a pair of torsion springs are provided at opposite positions of the assembly. Where the assembly is rectangular in plan view, a torsion spring may be provided at two opposite corners of one side of the assembly.

In this case, the or each forms may comprise a bar around which the or each torsion spring is wound. Means may be provided to secure the bar or bars to the cover and to provide a hinge for the cover to the frame.

For example the frame may have an upstanding flange with passages to receive ends of the bars which can rotate in the passage to provide a hinge.

Preferably, the frame provides a clear opening with a minimum dimension of at least 500 mm preferably at least 600 mm in order to provide room for a large man. Where the cover is rectangular, this minimum dimension may comprise the inside length of the sides, or the shortest sides of the cover, or where the assembly is circular this minimum dimension may be the inner diameter of the frame.

The frame may have a channel around at least part of its periphery in which the spring means is accommodated, which channel may have drainage apertures so that water does not collect in the channel.

The locking means may be readily releasable from the inside of the assembly so that a man within a manhole or access opening over which the assembly is positioned, can release a latch so that the cover can be opened by the spring means. Preferably, the locking means are also releasable from the top of the assembly but only using a special tool or tools which can pass through the cover to release the latch below.

If desired, security means may be provided so that an unauthorised user cannot open the cover from the top side.

According to a second aspect of the invention we provide an installation comprising a manhole or access opening large enough for a man to pass through, a cover and frame assembly according to the first aspect of the invention over the manhole or access opening.

The invention will now be described with the aid of the accompanying drawings in which: Figure 1 is a plan view of a cover and frame assembly in accordance with the first aspect of the invention, the left half of the drawing showing the cover in position, and the cover being removed in the right half of the drawing to reveal the constructional features of the assembly beneath.

Figure 2 is an enlarged cross sectional view taken along the lines 2-2 of Fig. 1.

Referring to the drawings, a manhole cover and frame assembly 10 comprises a frame 11 and a cover 12, the frame 11 defining an opening 13 which in use gives access to an access opening beneath.

The frame 11 has an outer upstanding peripheral flange 15. which extends around the entire frame, which in the present example, is substantially rectangular.

An inner peripheral flange 16 is also provided, so that the periphery of the frame 11 provides a,channel 18.

The frame is made up of four sides with mitred corners which are welded together.

A further channel 19 is provided on the inner side of the inner peripheral flange 16, which channel 19 in use, accommodates a sealing means such as an 0 ring or the like (not shown) to provide a seal between the cover 12 and the frame 11.

The cover 12 comprises a plate 20 with reinforcing ribs 21 beneath, which extend across the opening 13 defined by the frame 11 and add rigidity to the plate 20.

The cover 12 is hinged to the frame 11 for movement between a closed condition as seen on the left hand side of Fig. 1, and an open position in which the cover 12 would extend generally upright and permit access to be gained to and from the opening beneath the assembly.

The hinges are provided by bars 25 (only one of which can be seen on the right hand side of Fig. 1 of the drawings), which each have end parts 26 which extend through passageways 27 in the puter peripheral flange 15 of the frame 11, at-two opposite corners of a side 28 of the frame.

The ends 26 of the bars 25 may extend outwardly of the frame 11, and be closed by a cap 29 as shown, or may be threaded and have a nut received thereon as required.

Thus the cover may pivot about a hinge axis A between open and closed conditions.

The bars 25 at each corner of the side 28 of the assembly, are secured to the underside 30 of the cover 12. The underside 30 of the cover 12 has blocks 32 welded thereto which each have a threaded opening 33. The bars 25 have flattened regions 36 which bear on the blocks 32, so that passages 37 within the bars 25 are aligned with the passageways 33 of the blocks 32. Thus bolts 38 are passed through the bar 25 into the blocks 33.

Wound around the bars 25 between the blocks 32 on the underside 30 of the cover 12, are torsion springs 40. One end 41 of each of the torsion springs bears on the underside 30 of opposite sides of the cover 12, whilst the other end of the torsion springs indicated at 42, are each received in an opening 43 in a base 44 of the peripheral channel 18 of the frame 11, and extend into a support or bearing block 45 provided on the underside of the base 44. Thus the torsion springs 40 at each corner of the side 28 of the assembly act between the cover and the frame, to normally bias the cover 12 to an open condition.

To maintain the cover 12 in a closed condition, a suitable locking means is provided along a side 46 of the assembly opposite to side 28. To provide access to the locking means, the cover 12 has an opening 47.

Preferably, the locking means includes a latch which is readily releasable from the underside of the assembly 10 so that a man within the opening 13 defined by the frame 11, can release the latch to open the cover 12 and hence escape from the opening 13.

Preferably the latch means is only releasable through opening 47 from the top side of the assembly, by the use of a special tool or tools so as to provide security against unauthorised opening.

Preferably the base 44 of the peripheral channel of the frame 11, has drainage openings (not shown) so that water does not collect in the channel 18.

The frame 11 and cover 12 may each be made for example of steel, suitably formed, although of course may be fabricated or cast in other materials and in any other manner.

Instead of two torsion spring 40 acting between the cover and the frame, any other spring means may be provided, although for particularly heavy covers 12, torsion springs are the preferred way of providing adequate force to open the cover 12, particularly where the cover is heavy.

Typically, a cover would weigh in excess of 50 pounds, possibly in excess of 100 pounds and thus the spring means needs to exert a considerably force between the cover and the frame.

In the present example, the minimum dimension of the opening 13 defined by the cover 11 is 500 mm although preferably, each of the sides of the rectangular frame define an opening having a minimum dimension of at least 600 mm.

As described, a hinge has been provided between the cover and the frame by the bars 25 at each opposite corner of the side of the assembly. If desired, hinge means may otherwise be provided if required.

Further, although as described a spring means has been provided at each of two opposite corners of one side of the assembly, if desired, a single spring means may be provided, for example, centrally of one side of the assembly, or only one spring means may be provided at one corner.

The features disclosed in the foregoing description, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method of process for attaining the disclosed result, or a class or group of substances or compositions, as appropriate, may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

1. A cover and frame assembly of the kind specified the cover being hinged relative to the frame for movement between an open position and a closed condition, spring means acting between the cover and frame normally to bias the cover to an open condition, releasable locking means to maintain the cover in a closed condition against the force of the spring means, the spring means comprising a torsion spring, a longitudinal axis of the spring being coincident with the hinge axis.

2. An assembly according to claim 1 wherein the one end of the spring bears on the cover and the other end of which bears on the frame.

3. An assembly according to claim 2 wherein the one end of the torsion spring is received by a receiving means of the frame on which the end bears, whereas the other end of the torsion spring bears on the underside of the cover.

4. An assembly according to any one of the preceding claims wherein the assembly is rectangular in plan view.

5. An assembly according to any one of the preceding claims wherein a pair of torsion springs are provided at opposite positions of the assembly.

6. An assembly according to claim 5 where appendant to claim 4 wherein a torsion spring is provided at two opposite corners of one sideof the assembly.

7. An assembly according to any one of the preceding claims wherein the or each torsion spring is wound around a former.

8. An assembly according to claim 7 wherein the or each former comprises a bar.

9. An assembly.according to claim 7 or claim 8 wherein means are provided to secure the bar or bars to the cover and to provide a hinge for the cover to the frame.

10. An assembly according to claim 9 wherein the frame has an upstanding flange with passages to receive ends of the bar or bars which can rotate in the passages as a hinge.

11. An assembly according to any one of the preceding claims wherein the frame provides a clear opening with a minimum dimension of at least 500 mm in order to provide room for a large man to pass through the opening.

12. An assembly according to claim 11 where appendant to claim 4 wherein the minimum dimension comprises the inside length of the sides or the shorter sides of the cover.

13. An assembly according to any one of the preceding claims wherein the frame has a channel around at least part of its periphery in which the spring means is accommodated.

14. An assembly according to claim 13 wherein the channel has drainage apertures so that water does not collect in the channel.

15. An assembly according to any one of the preceding claims wherein the locking means is readily releasable from the inside of the assembly.

16. An assembly according to claim 15 wherein the locking means are also releasable from the top of the assembly but only using a special tool or tools which can pass through the cover to release the locking means below.

17. An assembly according to claim 16 wherein security means are provided so that an unauthorised user cannot open the cover from the top side.

18. A cover and frame assembly of the kind specified, the cover being hinged relative to the frame for movement between an open condition and a closed condition, spring means acting between the cover and frame normally to bias the cover to an open condition, releasable locking means to maintain the cover in a closed condition against the force of the spring means, the locking means readily releasable from the inside of the assembly.

19. An assembly according to claim 18 having any of the features of the assembly according to any one of claims 1 to 17.

20. A cover and frame assembly substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

21. An installation comprising a manhole or access opening large enough for a man to pass through, a cover and frame assembly according to any one of claims 1 to 19 over the manhole or access opening.

22. An installation substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

23. Any novel feature or novel combination of features disclosed herein and/or shown in the accompanying drawings.