GB2257735A

GB2257735A - Keyhole unit for an access cover

Info

Publication number: GB2257735A
Application number: GB9214497A
Authority: GB
Inventors: Ivan Lee Robins
Original assignee: Glynwed Consumer and Building Products Ltd
Current assignee: Glynwed Consumer and Building Products Ltd
Priority date: 1991-07-09
Filing date: 1992-07-08
Publication date: 1993-01-20
Anticipated expiration: 2012-07-08
Also published as: GB9114821D0; GB2257735B; GB9214497D0

Abstract

In order to prevent its being filled with undesirable matter, or, for example, presenting a trap for shoe heels, a keyhole aperture (1') of an access cover (14) is obstructed by a blanking piece (34) which is resiliently urged to the obstructing position but can be moved against the biasing means (13) to a position which enables a key to be inserted into the aperture for lifting the cover. Preferably the blanking piece fits into the aperture in the obstructing position. The aperture is in a plate (1) which may be an integral part of the upper surface of the access cover, or may be a separate piece which secures to the upper surface. In the latter arrangement the plate can be part of a keyhole unit which secures to an access cover and contains the blanking piece and resilient biasing means. <IMAGE>

Description

IMPROVEMENTS RELATING TO ACCESS COVERS The present invention relates to access covers.

There are many situations\ where access ways must be provided through floors, pavements and roads, and many other surfaces to spaces below such as sewers, electrical cable junctions, ventilation shafts etc. If pedestrian or vehicular traffic must pass over these access ways, or where weatherproofing is required, an access cover may be provided.

Access covers are often heavy and flush fitting so that tools (commonly known as keys) are required to remove them. Such keys are normally in the form of an elongate bar with a handle at one end and lugs projecting radially from the bar at the other end, the lugs being diametrically spaced from one another. The access cover has a keyhole which comprises a void covered with a plate having an elongate aperture. The end of the key is inserted into the keyhole with its lugs aligned with the aperture and the key is then turned axially through 900 so that the lugs engage with the underside of the plate. The tool can then be used to lift the cover.

Problems arise because the keyholes can fill up with mud, grit, rock salt and litter and this can become compacted to a hard mass which can be very difficult to clear out in order to insert the key.

Also, the tip of the heel of a high-heeled shoe can enter the keyhole, possibly causing the wearer of the shoe to stumble or causing damage to the shoe.

One proposal to overcome these disadvantages is that a plastic plug should be inserted into the hole.

However, it has been found that these plugs are often omitted when a cover is replaced or are removed by children.

The present invention consists in, from a first aspect, a keyhole unit adapted for incorporation into an access cover, comprising a keyhole plate containing a keyhole aperture, a blanking piece movable between a first position in which it obstructs the keyhole aperture and a second position in which a key may be inserted into the keyhole aperture, and resilient biasing means arranged to urge the blanking piece into its first position.

From a second aspect, the invention consists in an access cover incorporating a keyhole nut according to the first aspect of the invention set forth.

From a third aspect, the invention consists in an access cover including a keyhole plate having a keyhole aperture therethrough, a blanking piece movable between a first position in which it obstructs the keyhole aperture and a second position in which a key may be inserted into the keyhole aperture, and resilient biasing means arranged to urge the blanking piece into its first position.

The blanking piece preferably fits within the keyhole aperture while in its first position (a close fit being most effective) or else it could be made larger than the aperture to close the aperture from one side.

In the third aspect of the invention set forth the keyhole plate may be an integral part of an upper surface of the access cover or, preferably, it may be a separate piece secured to the upper surface of the access cover.

In a preferred embodiment the keyhole plate is fixed to one end of a tubular body. The tubular body receives the blanking piece, arranged for axial movement relative thereto, and contains the resilient biasing means. Conveniently the resilient biasing means comprises a helical compression spring which acts on the blanking piece to bias the blanking piece towards the keyhole plate. Adjustment means is also preferably included to limit adjustably the travel of the blanking piece in the direction of the keyhole plate.The adjustment means may comprise an externally threaded elongate member which carries the blanking piece at one end and is threadedly engaged with an internally threaded member, such as a nut, which bears on an abutment spaced from the keyhole plate and, between the blanking piece and internally threaded member, a helical spring forming the resilient biasing means being located on the elongate member and acting between the blanking piece and a bearing at a fixed position intermediate the keyhole plate and the abutment, thereby to urge the blanking piece towards the keyhole plate. The threaded engagement of the elongate member with the internally threaded member enables the elongate member to be moved axially relative to the keyhole plate to adjust the extent of the travel of the blanking piece away from the bearing under the action of the spring.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawing in which the sole figure is a sectional view of a keyhole unit for insertion into an access cover.

The keyhole unit, as shown in. the drawing, comprises a keyhole plate 1 fixed to the top end of a cylindrical tubular body 2. The keyhole plate 1 has an elongate keyhole aperture 1' adapted to receive and locate the operative end of a key, not shown, of a known form. The centre of the keyhole aperture 1' is coincident with the central axis of the tubular body 2, the internal diameter of the tubular body being greater than the length of the keyhole aperture.

A blanking assembly is located within the tubular body 2. The blanking assembly comprises a blanking piece formed from a punching 3 and a first washer 4 welded together. The punching 3 is shaped and dimensioned to fit within the keyhole aperture 1' with a small peripheral clearance. The first washer 4 is chosen to have an outer diameter slightly less than the internal diameter of the tubular body 2, but its diameter is too great to allow it to pass through the keyhole aperture.

A length of bar 5, threaded along its length, is welded to the first washer 4 and extends perpendicularly from it. The bar 5 is slightly longer than the tubular body 2. A self-locking nut 6 and second washer 7 are fitted to the end of the bar 5, beyond the end of the tubular body. The second washer 7 has an external diameter approximately equal to that of the tubular body 2, and is arranged to abut against the free end of the tubular body 2.

A third washer 8 is fitted over the bar 5 and has an external diameter slightly smaller than the internal diameter of the tubular body 2. The third washer 8 is located within the tubular body 2 and is retained in position approximately one third of the way down the tubular body from its top end by a pair of pins 9, conveniently Bissel Pins, extending chordally across the tubular body, parallel to one another, against parallel flats 11 formed in the bar 5. The engagement of the pins 9 with the flats\11 restrains the bar 5 from turning in the tubular body. Chorded shoulders 12 presented on the bar at the upper ends of the flats 11 serve as stops to limit downward movement of the bar, and hence of the punching 3, by abutment against the pins 9.

A helical compression spring 13 surrounds the bar 5 and bears on and is constrained, under compression, between the first washer 4 and the third washer 8.

In use, the spring 13 biases the blanking assembly towards the keyhole plate 1 so that the punching 3 fits into the keyhole aperture 1', substantially closing it. Upward travel of the blanking assembly is limited by the bar 5, the second washer 7, and the nut 6. As the blanking assembly moves upwards, the second washer 7 makes contact with the bottom end of the tubular body 2 so preventing further movement. The final height of the blanking assembly can be set by adjusting the position of the nut 6 on the bar.

The keyhole unit is fitted for use to an access cover 14 at a hole 15 in the cover, the keyhole plate 1 being welded to the cover at the hole with the tubular body 2 depending below the cover.

To use the keyhole aperture 1', the operative end of the key is placed onto the top of the punching 3 and the key is pressed downwards to depress the punching from the aperture sufficiently to enable the operative end of the key to be engaged with the underside of the keyhole plate 1. Rotation of the key then locates its operative end in position under the keyhole plate in the normal way. The pins 9 prevent the bar 5 from turning with the key, and thev first washer 4 of the blanking assembly holds the bar 5 co-axial with the tubular body 2 when the punching 3 is depressed out of the keyhole aperture 1.

The level at which the pins 9 are positioned is determined by the depth of the operative end of the key to be engaged in the keyhole unit.

The rate of the spring 13 is chosen so that a person using the key must put a substantial part of their weight onto the handle of the key to force the operative end of the key into the aperture 1'. In this way, the heel of a shoe making brief contact with the punching 3 will not normally cause it to depress significantly.

It will be appreciated that if the spring should break or become weakened with use the blanking assembly can be readily removed from the tubular body to replace the spring when the pins 9 have been withdrawn from the body, the nut 6 and washers 7, 8 being removed to enable the spring to be drawn off the bar for replacement.

Claims

1. A keyhole unit adapted for incorporation into an access cover, comprising a keyhole plate containing a keyhole aperture, a blanking piece movable between a first position in which it obstructs the keyhole aperture and a second position in which a key may be inserted into the keyhole aperture, and resilient biasing means arranged to urge the blanking piece into its first position.

2. A keyhole unit according to Claim 1 wherein the blanking piece fits within the keyhole aperture in its first position.

3. A keyhole unit according to Claim 1 or Claim 2 including a tubular body to one end of which the keyhole plate is fixed and which receives the blanking piece and contains the resilient biasing means, the blanking piece being movable axially of the tubular body between its first and second positions.

4. A keyhole unit according to any preceding claim wherein the resilient biasing means comprises a helical compression spring which acts on the blanking piece to bias the blanking piece towards the keyhole plate.

5. A keyhole unit according to any preceding claim wherein adjustment means is included to limit adjustably the travel of the blanking piece in the direction of the keyhole plate.

6. A keyhole unit according to Claim 5 as dependent from Claim 4 wherein the adjustment means comprises an externally threaded elongate member which carries the blanking piece at one end and is threadedly engaged with an internally threaded member which bears on an abutment spaced from the keyhole plate and between the blanking piece and the internally threaded member, the helical spring being located on the elongate member and acting between the blanking piece and a bearing at a fixed position intermediate the keyhole plate and the abutment, thereby to urge the blanking piece towards the keyhole plate, and the threaded engagement of the elongate member with the internally threaded member enabling the elongate member to be moved axially relative to the keyhole plate to adjust the extent of the travel of the blanking piece away from the bearing under the action of the spring.

7. A keyhole unit according to Claim 3 and Claim 6 wherein the bearing comprises a washer supported in the tubular body by pins retained to the tubular body and engaging with opposed flats formed in the elongate member to restrain the elongate member from turning relative to the tubular body.

8. An access cover incorporating a keyhole unit according to any preceding claim.

9. An access cover including a keyhole plate having a keyhole aperture therethrough, a blanking piece movable between a first position in which it obstructs the keyhole aperture and a second position in which a key may be inserted into the keyhole aperture, and resilient biasing means arranged to urge the blanking piece into its first position.

10. An access cover according to Claim 9 wherein the keyhole plate is an integral part of an upper surface of the access cover.

11. An access cover according to Claim 9 wherein the keyhole plate is a separate piece from, and is secured to, an upper surface of the access cover.

12. An access cover according to any of Claims 9 to 11 wherein the blanking piece fits within the keyhole aperture in its first position.

13. An access cover according to any of Claims 9 to 12 wherein the keyhole plate has fixed to it one end of a tubular body which receives the blanking piece and contains the resilient biasing means, the blanking piece being movable axially of the tubular body between its first and second positions.

14. An access cover according to any of Claims 9 to 13 wherein the resilient biasing means comprises a helical compression spring which acts on the blanking piece to bias the blanking piece towards the keyhole plate.

15. An access cover according to any of Claims 9 to 14 wherein adjustment means is included to limit adjustably the travel of the blanking piece in the direction of the keyhole plate.

16. An access cover according to Claim 15 as dependent from Claim 14 wherein the adjustment means comprises an externally threaded elongate member which carries the blanking piece at one end and is threadedly engaged with an internally threaded member which bears on an abutment spaced from the keyhole plate and between the blanking piece and the internally threaded member, the helical spring being located on the elongate member and acting between the blanking piece and a bearing at a fixed position intermediate the keyhole plate and the abutment, thereby to urge the blanking piece towards the keyhole plate, and the threaded engagement of the elongate member with the internally threaded enabling the elongate member to be moved axially relative to the keyhole plate to adjust the extent of the travel of the blanking piece away from the bearing under the action of the spring.

17. An access cover according to Claim 13 and Claim 16 wherein the bearing comprises a washer supported in the tubular body by pins retained to the tubular body and engaging with opposed flats formed in the elongate member to restrain the elongate member from turning relative to the tubular body.

18. A keyhole unit substantially as described herein with reference to the accompanying drawing.

19. An access cover substantially as described herein with reference to the accompanying drawing.