GB1600493A

GB1600493A - Access cover

Info

Publication number: GB1600493A
Application number: GB3010977A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1977-07-18
Filing date: 1977-07-18
Publication date: 1981-10-14
Also published as: BE869070A

Description

(54) ACCESS COVER (71) I, FRANCIS SIDNEY CLARK, of 293 Broadway, Yaxley, Peterborough, a British subject, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to access covers, by which is meant covers for items such as sewage manholes or inspection chambers, chambers for electrical gear, or chambers for waste cocks, which covers will normally but not essentially be roughly level with the surface of the ground. In particular, manhole covers have traditionally in the past been made from cast iron, but more recently techniques have been developed whereby such covers are formed by pressing from metal plate.

The present invention provides an access cover pressed from metal plate, the cover having a load bearing surface able to directly bear traffic loads and a lifting device in the form of a recess pressed in the plate and a lifting bar attached to the plate and extending across the recess.

Preferably the recess is of dished shape.

Preferably the plate has been pressed in a single pressing operation which included forming flanges around the cover, forming surface protuberances or depressions on the load bearing surface of the cover, and forming the recess.

If the cover has surface protuberances or depressions on its load bearing surface, the protuberances or depressions and the recess or recesses can be pressed in a single pressing operation between dies which are adjusted so that the approach of the dies is limited by a projection which forms the recess, the thickness of the metal itself and the backing part of the opposite die, and not by engagement on the flat surface of the plate.

There are preferably a pair of openings.

formed on either side of the recess, the lifting bar being inserted through the openings and secured in position, and the openings can also be formed in the single pressing operation referred to above. A lifting bar may be secured in position by pressing the metal adjacent the openings to grip the lifting bar in the openings. Each opening is preferably formed by punching out towards the lower side of the plate a tongue of metal which remains attached to the side wall of the recess and over which passes the lifting bar, the tongue being forced against the lifting bar to grip the lifting bar in the opening after insertion of the lifting bar. The lifting bar itself can be a piece of flat strip and the openings can be of correspondingly rectangular crosssection.

The use of the openings gives a secure attachment which is not so susceptible to corrosion or concealed weakness as say a welded or brazed attachment.

In general terms, the metal plate can be coated after pressing, for instance by hot dip galvanising or by painting if the plate had already been galvanised, and such coating can fill any small gaps that remain around the ends of the lifting bar and provide a stench-proof cover which will pass the standard smoke tests (or, with closer tolerances in the design of the lifting bar and of the openings, a stench-proof cover can be provided when the tongues have been forced against the lifting bar, as described above).

As an alternative, the lifting bar may be attached to the top of the plate and not passed through any openings in the plate, for example being welded or brazed in position. However, the use of the openings is particularly advantageous when the plate is provided with a protective coating before pressing, because in such circumstances special techniques would have to be used if the lifting bar were attached by welding or brazing.

The lifting bar may be completely straight, but preferably has its end portions aligned and the centre portion parallel thereto but at a slightly higher level, being connected to the end portions by step portions, as this gives more room for fingers to pass under the lifting bar. The arrangement can be such that the lifting bar still does not project above the top of the recess, and is preferably substantially coplanar with the top of the cover (ignoring any surface protuberances or any lip around the recess).

The invention will be further described, by way of example, with reference to the accompanying drawing, in which: Figure 1 is a perspective view of an inspection chamber cover in accordance with the invention, Figure 2 is a top view, on a larger scale, of one of the recesses in the cover of Figure 1; Figure 3 is a vertical section along the line III--III of Figure 2; and Figure 4 is a vertical section through parts of two dies for forming the cover of Figure 1.

As shown in Figure 1, the cover is of rectangular shape and is pressed from a metal plate 1 and includes two lifting devices in the form of dished recesses 2 in the plate 1 and a lifting bar 3 attached to the plate 1 and extending across each respective recess 2. As shown in Figure 1, the area of each recess 1 when viewed in plan is substantially less than the area of the cover when viewed in plan. The cover has surface protuberances in the form of small bulges 4, and can also have for instance a frame 5 for framing the maker's name.

As can be seen in Figure 3, the lifting bar 3 is formed from flat strip of rectangular cross-section, and its end portions pass through openings 6 of correspondingly rectangular cross-section whilst the top surface of its centre portion is substantially coplanar with the top surface of the plate 1. As can be seen in Figure 3, the openings are formed by punching out towards the lower side of the plate 1 small tongues of metal 7 which remain attached to the side wall of the recess 2 and over which passes the lifting bar 3.

The tongues are subsequently pressed against the lifting bar 3 to grip the lifting bar 3 in the openings 6. A lip 8 surrounds each recess 2.

The plate 1 is pressed in a single pressing operation which includes forming flanges 9 around the cover, the bulges 4, the frame 5, the recesses 2 and the lips 8, and at the same time, the openings 6 are punched. The dies 10 and 11 are shown in Figure 4, and in the pressing operation, the dies are brought together until their approach is limited by the cylindrical projection 12 bottoming against the base of the corresponding recess 13 with the intervention of the thickness of the metal plate 1. The projection 12 forms a recess 2 whilst pins 14 form the bulges 4 and lips 15 bend over the flanges 9. The tongues 7 are punched out by sharpened pieces 16.

After pressing, the lifting bars 3 are inserted and the cover is re-pressed to apply pressure to the bottom sides of the tongues 7 at the points indicated by the arrows in Figure 3.

Advantageously, a sealing fit is obtained between the material surrounding the openings 6 and adjacent portions of the lifting bars by the pressure applied to the tongue 7.

The plate 1 may be for instance about 3 mm thick.

The preferred material for the plate 1 is mild steel.

The metal plate may be provided with a protective coating before pressing and then be re-coated after pressing, or alternatively may simply be coated after pressing.

WHAT I CLAIM IS: 1. An access cover pressed from metal plate, the cover having a load bearing surface able to directly bear traffic loads and a lifting device in the form of a recess pressed in the plate and a lifting bar attached to the plate and extending across the recess.

2. The cover of claim 1, wherein the recess is of dished shape.

3. The cover of claim 1 or claim 2, wherein the plates has been pressed in a single pressing operation which included forming flanges around the cover, forming surface protuberances or depressions on the load bearing surface of the cover, and forming the recess.

4. The cover of any one of the preceding claims, and having surface protuberances or depressions on its load bearing surface which have been pressed with the recess in a single pressing operation between dies which are adjusted so that the approach of the dies is limited by a projection which forms the recess, the thickness of the metal plate and the backing part of the opposite dies, and is not limited by engagement of the flat surface of the plate.

5. The cover of any one of the preceding claims, wherein a pair of openings was formed on either side of the recess, the lifting bar having been inserted through the openings and secured in position.

6. The cover of claim 5 and also of either claim 3 or claim 4, wherein the openings were also formed in the single pressing operation.

7. The cover of claim 5 or claim 6, wherein the lifting bar was secured in position by pressing the metal adjacent the openings to grip the lifting bar in the openings.

8. The cover of claim 7, wherein each opening was formed by punching out towards the lower side of the plate a tongue of metal which remains attached to the side wall of the recess and over which passes the lifting bar, the tongues being pressed against the lifting bar to grip the lifting bar in the openings after insertion of the lifting bar.

9. The cover of any one of claims 5 to

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Claims

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gives more room for fingers to pass under the lifting bar. The arrangement can be such that the lifting bar still does not project above the top of the recess, and is preferably substantially coplanar with the top of the cover (ignoring any surface protuberances or any lip around the recess).

The invention will be further described, by way of example, with reference to the accompanying drawing, in which: Figure 1 is a perspective view of an inspection chamber cover in accordance with the invention, Figure 2 is a top view, on a larger scale, of one of the recesses in the cover of Figure 1; Figure 3 is a vertical section along the line III--III of Figure 2; and Figure 4 is a vertical section through parts of two dies for forming the cover of Figure 1.

As shown in Figure 1, the cover is of rectangular shape and is pressed from a metal plate 1 and includes two lifting devices in the form of dished recesses 2 in the plate 1 and a lifting bar 3 attached to the plate 1 and extending across each respective recess 2. As shown in Figure 1, the area of each recess 1 when viewed in plan is substantially less than the area of the cover when viewed in plan. The cover has surface protuberances in the form of small bulges 4, and can also have for instance a frame 5 for framing the maker's name.

As can be seen in Figure 3, the lifting bar 3 is formed from flat strip of rectangular cross-section, and its end portions pass through openings 6 of correspondingly rectangular cross-section whilst the top surface of its centre portion is substantially coplanar with the top surface of the plate 1. As can be seen in Figure 3, the openings are formed by punching out towards the lower side of the plate 1 small tongues of metal 7 which remain attached to the side wall of the recess 2 and over which passes the lifting bar 3.

The tongues are subsequently pressed against the lifting bar 3 to grip the lifting bar 3 in the openings 6. A lip 8 surrounds each recess 2.

The plate 1 is pressed in a single pressing operation which includes forming flanges 9 around the cover, the bulges 4, the frame 5, the recesses 2 and the lips 8, and at the same time, the openings 6 are punched. The dies 10 and 11 are shown in Figure 4, and in the pressing operation, the dies are brought together until their approach is limited by the cylindrical projection 12 bottoming against the base of the corresponding recess 13 with the intervention of the thickness of the metal plate 1. The projection 12 forms a recess 2 whilst pins 14 form the bulges 4 and lips

15 bend over the flanges 9. The tongues 7 are punched out by sharpened pieces 16.

After pressing, the lifting bars 3 are inserted and the cover is re-pressed to apply pressure to the bottom sides of the tongues 7 at the points indicated by the arrows in Figure 3.

Advantageously, a sealing fit is obtained between the material surrounding the openings 6 and adjacent portions of the lifting bars by the pressure applied to the tongue 7.

The plate 1 may be for instance about 3 mm thick.

The preferred material for the plate 1 is mild steel.

The metal plate may be provided with a protective coating before pressing and then be re-coated after pressing, or alternatively may simply be coated after pressing.

WHAT I CLAIM IS: 1. An access cover pressed from metal plate, the cover having a load bearing surface able to directly bear traffic loads and a lifting device in the form of a recess pressed in the plate and a lifting bar attached to the plate and extending across the recess.
2. The cover of claim 1, wherein the recess is of dished shape.
3. The cover of claim 1 or claim 2, wherein the plates has been pressed in a single pressing operation which included forming flanges around the cover, forming surface protuberances or depressions on the load bearing surface of the cover, and forming the recess.
4. The cover of any one of the preceding claims, and having surface protuberances or depressions on its load bearing surface which have been pressed with the recess in a single pressing operation between dies which are adjusted so that the approach of the dies is limited by a projection which forms the recess, the thickness of the metal plate and the backing part of the opposite dies, and is not limited by engagement of the flat surface of the plate.
5. The cover of any one of the preceding claims, wherein a pair of openings was formed on either side of the recess, the lifting bar having been inserted through the openings and secured in position.
6. The cover of claim 5 and also of either claim 3 or claim 4, wherein the openings were also formed in the single pressing operation.
7. The cover of claim 5 or claim 6, wherein the lifting bar was secured in position by pressing the metal adjacent the openings to grip the lifting bar in the openings.
8. The cover of claim 7, wherein each opening was formed by punching out towards the lower side of the plate a tongue of metal which remains attached to the side wall of the recess and over which passes the lifting bar, the tongues being pressed against the lifting bar to grip the lifting bar in the openings after insertion of the lifting bar.
9. The cover of any one of claims 5 to

8, wherein the lifting bar was formed from a piece of flat strip of rectangular crosssection, and the openings are of correspondingly rectangular cross-section.
10. The cover of any one of claims 5 to 9, wherein a sealing fit was obtained between the lifting bar and the openings by the application of pressure.
11. The cover of any one of the preceding claims, wherein the metal plate was coated after pressing.
12. The cover of claim 9, wherein the metal plate was provided with a protective coating before pressing and was re-coated after pressing.
13. The cover of any one of the preceding claims, wherein the cover is formed of mild steel.
14. The cover of any one of claims 1-3, wherein the lifting bar is attached to the top of the plate and does not pass through any openings in the plate.
15. The cover of any one of the preceding claims, wherein the lifting bar has its end portions aligned and the centre portion parallel thereto but at a slightly higher level, being connected to the end portions by step portions.
16. The cover of claim 14, wherein the top surface of the centre portion of the lifting bar is substantially coplanar with the top of the metal plate (ignoring any surface protuberances or any lip around the recess).
17. An access cover, substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.