GB2158134A

GB2158134A - Duct or manhole access cover

Info

Publication number: GB2158134A
Application number: GB08510149A
Authority: GB
Inventors: Rolfe Lionel Hancher
Original assignee: Duct & Access Covers Ltd
Current assignee: Duct & Access Covers Ltd
Priority date: 1984-04-25
Filing date: 1985-04-20
Publication date: 1985-11-06
Also published as: GB8510149D0; GB2158134B

Abstract

A duct or manhole access cover suitable for use in a duct or manhole opening 19 provided with a generally channel-form cover support frame 18 having a lower height at its radially inner side 16 than its radially outer side 17, comprises a main generally strip- form outer frame 2 having radially inwardly depending therefrom an infill support frame 3 for supporting a substantially hard setting infill material 10 across the cover. A plurality of circumferentially spaced bearing pads 12 is disposed in the vicinity of the radially inward side 4 of said outer frame 2 at its underside 11, for supporting said cover on the radially inner side 16 of said cover support frame 18 and resisting rocking of said cover thereon. <IMAGE>

Description

SPECIFICATION Duct or manhole access cover This invention relates to duct or manhole access covers and in particular to load-bearing covers suitable for use on support frames of the type which are generally channei-form and lower at their inward edges.

Duct and manhole access covers were for many years made of cast iron and used with support frames of the above mentioned type.

Over the years many such covers have become broken and required replacement. In practice this has generally required complete removal of the existing support frame and installation of new cover and support frame combinations. Since support frames of the abovementioned type are very heavy and permanently set in the surrounding carriageway this replacement can be a very time consuming and costly business.

It is an object of the present invention to avoid or minimize one or more of the above disadvantages.

The present invention provides a duct or manhole access cover suitable for use in a duct or manhole opening provided with a generally channel-form cover support frame having a lower height at its radially inner side than its radially outer side, said cover comprising a main generally strip-form outer frame having radially inwardly depending therefrom an infill support frame for supporting a substantially hard setting infill material across the cover substantially inside of said outer frame and substantially below the upper surface of said outer frame, a plurality of circumferentially spaced bearing pads being disposed in the vicinity of the radially inward side of said outer frame at its underside for supporting said cover, in use thereof, on the radially inner side of said cover support frame and resisting rocking of said cover thereon.

Thus by means of the present invention it is possible to replace the old cast-iron type of cover with a new cover in a simple and economic manner without the need for replacing the fixed cover support frame.

Further preferred features and advantages of the invention will appear from the following detailed description given by way of example of a preferred embodiment illustrated with reference to the accompanying drawings in which: Figure 1 is a general perspective view of a cover of the invention but with the infill material absent; Figure 2 is a bqttom view of the structure of Fig. 1;and Figure 3 is a vertical cross-section through the complete cover of Fig. 1 in use.

Fig. 1 shows a cover skeleton 1 comprising a substantial structural outer frame 2 of che r ar rwr rl(rhor nlotp etPPI snarl sn infill port frame 3 depending from the radially inner edge 4 of the outer frame 2. The infill support frame 3 is made up of a sheet steel angle with a generally upright web 5 inclined downwardly and inwardly from the outer frame inner edge 4 (see Fig. 3) and a horizontal web 6 extending further inwardly. A mesh reinforcement 7 with downwardly turned outer edge portions 8 is supported on the horizontal web 6 of the infill support frame 3 to extend across the opening 9 of the latter.

The opening 9 of the support frame is infilled with a substantially hard-setting infill material 10 such as concrete, the base of the opening being closed by suitable temporary shuttering until the material has substantially set.

At the underside 11 of the outer frame 2 towards the inner edge 4 thereof is provided a plurality of circumferentially spaced apart bearing pads 1 2 in the form of small ribs or the like. These are conveniently disposed at the corners 1 3 of the frame and at the centres 14 of their longer sides 1 5. Thus in the case of a polygonal cover the number of bearing pads would generally correspond to at least the number of corners. In the case of a circular or rounded cover at least 3 spaced apart pads would be required.

The support bearing pads 1 2 are dimensioned so as to have a thickness slightly greater than the height-differential between the inner and outer limbs 16, 17 of a channel-form cover support frame 1 8 set into the opening 1 9 of a manhole 20. Thus in use, as may be seen in Fig. 3, the cover is supported on the cover support frame 1 8 substantially only at a plurality of spaced apart points on the inner limb 1 6 through the bearing pads 1 2 at the underside 11 of the outer frame 2 whereby the cover may be stably supported in position above the manhole against rocking even where the cover support frame has suffered some damage over the years.

By this means it will be appreciated that many broken manhole covers may be readily replaced without the need for replacement of the cover support frame. It will of course also be appreciated that the cover of the invention may be used with various cover support frame designs other than that specifically illustrated.

The cover skeleton including the reinforcing mesh and bearing pads may be made of any suitable shock resistant structural material, such as for example steel, preferably galvanized and/or otherwise protected against corrosion.

In other respects the cover is generally conventional including inter alia lifting holes in the outer frame for use in lifting the cover in known manner.

1. A duct or manhole access cover suit ehle for use in a duct or manhole opening

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Duct or manhole access cover This invention relates to duct or manhole access covers and in particular to load-bearing covers suitable for use on support frames of the type which are generally channei-form and lower at their inward edges. Duct and manhole access covers were for many years made of cast iron and used with support frames of the above mentioned type. Over the years many such covers have become broken and required replacement. In practice this has generally required complete removal of the existing support frame and installation of new cover and support frame combinations. Since support frames of the abovementioned type are very heavy and permanently set in the surrounding carriageway this replacement can be a very time consuming and costly business. It is an object of the present invention to avoid or minimize one or more of the above disadvantages. The present invention provides a duct or manhole access cover suitable for use in a duct or manhole opening provided with a generally channel-form cover support frame having a lower height at its radially inner side than its radially outer side, said cover comprising a main generally strip-form outer frame having radially inwardly depending therefrom an infill support frame for supporting a substantially hard setting infill material across the cover substantially inside of said outer frame and substantially below the upper surface of said outer frame, a plurality of circumferentially spaced bearing pads being disposed in the vicinity of the radially inward side of said outer frame at its underside for supporting said cover, in use thereof, on the radially inner side of said cover support frame and resisting rocking of said cover thereon. Thus by means of the present invention it is possible to replace the old cast-iron type of cover with a new cover in a simple and economic manner without the need for replacing the fixed cover support frame. Further preferred features and advantages of the invention will appear from the following detailed description given by way of example of a preferred embodiment illustrated with reference to the accompanying drawings in which: Figure 1 is a general perspective view of a cover of the invention but with the infill material absent; Figure 2 is a bqttom view of the structure of Fig. 1;and Figure 3 is a vertical cross-section through the complete cover of Fig. 1 in use. Fig. 1 shows a cover skeleton 1 comprising a substantial structural outer frame 2 of che r ar rwr rl(rhor nlotp etPPI snarl sn infill port frame 3 depending from the radially inner edge 4 of the outer frame 2. The infill support frame 3 is made up of a sheet steel angle with a generally upright web 5 inclined downwardly and inwardly from the outer frame inner edge 4 (see Fig. 3) and a horizontal web 6 extending further inwardly. A mesh reinforcement 7 with downwardly turned outer edge portions 8 is supported on the horizontal web 6 of the infill support frame 3 to extend across the opening 9 of the latter. The opening 9 of the support frame is infilled with a substantially hard-setting infill material 10 such as concrete, the base of the opening being closed by suitable temporary shuttering until the material has substantially set. At the underside 11 of the outer frame 2 towards the inner edge 4 thereof is provided a plurality of circumferentially spaced apart bearing pads 1 2 in the form of small ribs or the like. These are conveniently disposed at the corners 1 3 of the frame and at the centres 14 of their longer sides 1 5. Thus in the case of a polygonal cover the number of bearing pads would generally correspond to at least the number of corners. In the case of a circular or rounded cover at least 3 spaced apart pads would be required. The support bearing pads 1 2 are dimensioned so as to have a thickness slightly greater than the height-differential between the inner and outer limbs 16, 17 of a channel-form cover support frame 1 8 set into the opening 1 9 of a manhole 20. Thus in use, as may be seen in Fig. 3, the cover is supported on the cover support frame 1 8 substantially only at a plurality of spaced apart points on the inner limb 1 6 through the bearing pads 1 2 at the underside 11 of the outer frame 2 whereby the cover may be stably supported in position above the manhole against rocking even where the cover support frame has suffered some damage over the years. By this means it will be appreciated that many broken manhole covers may be readily replaced without the need for replacement of the cover support frame. It will of course also be appreciated that the cover of the invention may be used with various cover support frame designs other than that specifically illustrated. The cover skeleton including the reinforcing mesh and bearing pads may be made of any suitable shock resistant structural material, such as for example steel, preferably galvanized and/or otherwise protected against corrosion. In other respects the cover is generally conventional including inter alia lifting holes in the outer frame for use in lifting the cover in known manner. CLAIMS

1. A duct or manhole access cover suit ehle for use in a duct or manhole opening provided with a generally channel-form cover support frame having a lower height at its radially inner side than its radially outer side, said cover comprising a main generally stripform outer frame having radially inwardly depending therefrom an infill support framefor supporting a substantially hard setting infill material across the cover substantially inside of said outer frame and substantially below the upper surface of said outer frame, a plurality of circumferentially spaced bearing pads being disposed in the vicinity of the radially inward side of said outer frame at its underside for supporting said cover, in use thereof, on the radially inner side of said cover support frame and resisting rocking of said cover thereon.

2. An access cover according to Claim 1 which cover is substantially rectangular and has at least 4 said bearing pads.

3. An access cover according to Claim 1 which cover is substantially circular and has at least three said bearing pads.

4. An access cover according to any one of Claims 1 to 3 for a said duct or manhole opening having a cover support frame with a predetermined height differential between the inner and outer sides wherein said bearing pads have a thickness slightly greater than said height differential whereby in use of said cover on said opening, the cover is supported on said cover support frame substantially only on said bearing pads.

5. An access cover according to any one of Claims 1 to 4 wherein said outer frame is of a generally "lazy-'Z' "-shaped section with a radially outwardly extending upper web, downwardly and radially inwardly inclined central web, and a radially inwardly extending lower web.

6. An access cover according to any one of Claims 1 to 5 wherein said infill support frame is generally mesh-form.

7. An access cover according to Claim 6 when dependent on Claim 5 wherein the outer edge of said mesh-form support frame is supported on said lower web of the outer frame.

8. An access cover according to Claim 5 or Claim 7 wherein said bearing pads are disposed on the underside of the upper web of said outer frame.

9. An access cover according to any one of Claims 1 to 8 wherein said infill material is concrete.

10. A duct or manhole access cover suitable for use in a duct or manhole opening provided with a generally channel-form cover support frame having a lower height at its radially inner side than its radially outer side which cover is substantially as described hereinbefore with particular reference to Figs. 1 to 3 of the accompapying drawings.