Title:
MANHOLE COVER
United States Patent 3772828


Abstract:
A manhole cover including a main body dimensioned to fit in a manhole opening and rest on a ledge thereof, two locking members slidably mounted in the body for radial inward and outward movement between locking positions in which the locking members project under the ledge, in use of the cover, to prevent removal of the cover from the opening, and unlocking positions in which the locking members are withdrawn from beneath the ledge to permit removal of the cover from the opening, and operating mechanism in the body for actuating the locking members, the operating mechanism including means for locking the locking members against radial movement from the locking positions, and means for reciprocating the locking members between the locking and unlocking positions.



Inventors:
CHAHLEY W
Application Number:
05/204094
Publication Date:
11/20/1973
Filing Date:
12/02/1971
Assignee:
CHAHLEY W LTD,CA
Primary Class:
International Classes:
E02D29/14; (IPC1-7): E02D29/14
Field of Search:
94/34,35,36,37,38 52
View Patent Images:
US Patent References:
3263580Safety adaptor for manholes1966-08-02MacMillan
2391407Detachable port cover1945-12-25Funk
2363567Cover plate1944-11-28Blakeman
1400399Cistern-top1921-12-13Yaeche
1287290N/A1918-12-10Golden
1102422N/A1914-07-07McKeon
0811701N/A1906-02-06
0419903N/A1890-01-21



Foreign References:
AT191457B1957-08-26
Primary Examiner:
Frazier, Roy D.
Assistant Examiner:
Holko, Thomas J.
Claims:
I claim

1. A manhole cover including a main body dimensioned to fit in a manhole opening and rest on a ledge thereof, two locking members slidably mounted in the body for radial inward and outward movement between locking positions in which the locking members project under the ledge, in use of the cover, to prevent removal of the cover from the opening, and unlocking positions in which the locking members are withdrawn from beneath the ledge to permit removal of the cover from the opening, means for reciprocating the locking members between the locking and unlocking positions, said reciprocating means including a pinion rotatable about a vertical axis, said locking members having teeth in engagement with the pinion, and said pinion being shaped for engagement by a removable tool insertable downwardly through an aperture in the main body of the cover, whereby said tool can be operated to reciprocate said locking members, and means for locking the locking members against radial movement from the locking positions, said locking means including a locking dog carrier rotatable about said vertical axis concentrically with said pinion, said carrier having a locking dog engageable with the teeth of one of said locking members to lock said one locking member, the pinion and the other locking member against unlocking movement, said locking dog carrier also being shaped for engagement by a removable tool insertable downwardly through said aperture, whereby said last-mentioned tool can be operated to rotate said locking dog carrier between locking and unlocking positions.

2. A manhole cover according to claim 1 wherein the pinion and the carrier are shaped to require actuation by two substantially differently shaped tools.

3. A manhole cover according to claim 1 including a closing nut threadingly engaged in said aperture in the main body between the top thereof and the pinion and carrier, said nut being shaped for engagement by a tool substantially different from the pinion and carrier actuation tools.

4. A manhole cover according to claim 3 including a removable weatherproof plug between the closing nut and the upper end of the aperture in the main body.

5. A manhole cover according to claim 1 wherein said locking dog carrier is located below said pinion, and said pinion has an aperture through which said last-mentioned tool is insertable to engage said locking dog carrier.

6. A manhole cover according to claim 5 including a fixed annular wall within which the locking dog carrier is located, and wherein the locking dog carrier has an outer annular wall, a needle bearing arrangement being located between the outer annular wall of the locking dog carrier and the fixed annular wall.

7. A manhole cover according to claim 6 wherein the pinion has a lower annular wall extending downwardly within the outer annular wall of the locking dog carrier, a further needle bearing arrangement being located betwen the lower annular wall of the pinion and the outer annular wall of the locking dog carrier.

8. A manhole cover according to claim 7 wherein a thrust bearing is located between the bottom of the lower annular wall of the pinion and the locking dog carrier.

Description:
This invention relates to manhole covers.

Manhole covers frequently offer access to underground passages containing valuable installations, such as electrical communication systems and services such as electricity, water, fuel oil or natural gas. Although manhole covers are relatively difficult to remove because of their size and weight, they are however removable by readily available tools. It is therefore not particularly difficult for an unauthorized person to remove a manhole cover which simply rests on a ledge protruding in a frame surrounding a manhole opening.

It is therefore an object of the invention to provide a manhole cover which is relatively secure against unauthorized removal and which is therefore useful in closing manhole openings which give access to valuable installations.

According to the present invention therefore, a manhole cover includes a main body with two locking members slidably mounted in the body for radially inward and outward movement between a locking position in which the locking members can project under the ledge to prevent removal of the cover from the opening, and an unlocking position in which the locking members are withdrawn from under the ledge to permit removal of the cover from the opening. Operating mechanism within the body is operable to reciprocate the locking members between the locking and unlocking positions, and also to lock the locking members against radial movement from the locking and unlocking positions.

The operating mechanism may include a pinion rotatable about a vertical axis by a tool inserted downwardly through an aperture in the main body of the cover, the locking members having teeth in engagement with the pinion, such that rotation of the pinion reciprocates the locking members.

The operating mechanism may also have a carrier rotatable about a vertical axis by a tool inserted downwardly through the aperture in the main body, the carrier carrying a locking dog engageable with the teeth of one of the slides to lock the slide, the pinion and the other slide against unlocking movement. The pinion and the carrier are preferably shaped to only permit actuation by two substantially differently shaped tools.

The cover may also include a closing nut threadingly engaged in the aperture in the body below the top thereof and above the pinion and carrier, the nut being capable of actuation only by a tool shaped substantially differently from the pinion and carrier actuating tools.

One embodiment of the present invention will now be described by way of example, with reference to the accompanying drawings, in which,

FIG. 1 is a plan view of a manhole cover,

FIG. 2 is a bottom view of the manhole cover,

FIG. 3 is a diagrammatic sectional side view of the cover showing how the locking members operate to secure the cover in place,

FIG. 4 is a broken away plan view, with certain parts removed, showing how the locking members are locked in position,

FIG. 5 is a sectional side view of the operating mechanism for the locking members,

FIG. 6 is a plan view of a closing nut for the operating mechanism,

FIG. 7 is a similar view of a pinion retaining ring,

FIG. 8 is a similar view of the drive pinion,

FIG. 9 is a similar view of the locking dog carrier, and associated needle bearings, and

FIG. 10 is a diagrammatic plan view showing parts associated with the locking dog carrier.

Referring to the accompanying drawings, the manhole cover includes a circular main body 1 which in use sits on an inwardly projecting annular ledge 2 of a manhole frame 3. The body 1 carries a pair of oppositely directed, radially reciprocable latch slides 4 which form locking members.

FIGS. 1 to 3 show the latch slides 4 in their locking positions in which, when the cover is resting on the manhole frame 3, they project under the manhole frame ledge 2, thereby preventing removal of the manhole cover. The latch slides 4 are movable radially inwardly, by operating mechanism to be described later, to unlocking positions in which they are inwardly withdrawn from the annular ledge 2 to permit the cover to be removed.

Each latch slide 4 is slidably supported under the main body 1 by a supporting plate 5, one for each slide 4, secured by screws 6 to the underside of the body 1 near its outer edge. Each latch slide 4 is also slidably supported under the main body 1 by a central bottom plate 7 secured to the body 1 in a manner (not shown) similar to the supporting plates 5. The bottom plate 7 has an upstanding annular wall 8 spaced inwardly from the edge of the plate 7. (See FIG. 10 for explanation.)

The main body 1 has a central aperture 9 of substantially the same diameter as the internal diameter of the wall 8, and the operating mechanism for the slides 4 is located in the aperture 9 and within the wall 8. The upper end of the aperture 9 contains a rubber plug 10 which keeps dirt and moisture out of the aperture 9 to protect the operating mechanism below. The plug 10 has a circumferential rib 11 which fits into a corresponding recess in the wall of aperture 9 to give added protection from dirt and moisture.

A bronze closing nut 12 is screwed into an insert 13 secured in the aperture 9. The aperture 9 has an inwardly extending ledge 14 on which the insert 13 rests, insert 13 being a moderate press fit so as to be prevented from rotation in the aperture 9. The nut 12 has an annular groove 15 in its upper surface, and three equi-angularly spaced recesses 16 extend inwardly from the groove 15. Thus, a tool of a particular shape for engagement in the groove 15 and recesses 16 is required to rotate the nut 12.

Below the closing nut 12 is a retaining ring 18 also screwed into the insert 13, the function of the retaining ring 18 being to retain in place the operating mechanism now to be described. Retaining ring 18 has a wide central aperture 19 and two diametrically opposite holes 20 for receipt of an appropriately shaped tool for insertion and removal of the ring 18.

The operating mechanism includes a drive pinion 21 in engagement with teeth 22 on each slide 4. The pinion 21 has an outwardly directed flange 23 at its upper end which rests upon an inwardly directed flange 13a (see FIG. 5) at the lower end of the insert 13. The pinion 21 extends below the top of and within the wall 8 into engagement with the teeth 22 of the slides 4. Pinion 21 has a central aperture 21a, and three equi-angularly spaced recesses 23 extending outwardly from an upper portion of the aperture 21a. Therefore, another tool of a particular shape, for engagement in the aperture 21a and recesses 23, is required to rotate the pinion 21.

The operating mechanism also includes a locking dog carrier 24 within the wall 8 and resting on the top surface of the bottom plate 7. The carrier 24 has a pair of concentric annular walls 25, 26 joined by a bottom web portion 24a, the outer wall 25 extending upwardly nearly to the slides 4, and the inner wall 26 being of smaller height. An outer needle bearing 27 is located between the wall 8 and the outer wall 25 of the carrier 24, and an inner needle bearing 28 is located between the outer wall 25 and a downward extension 29 of the pinion 21 between the inner and outer wall 25, 26. A thrust bearing 17 is located between the bottom of the extension 19 and the web portion 24a. The inner wall 26 has a central aperture 30 of Y-shape, as shown in FIG. 9, for receipt of an appropriately shaped tool for rotation of the carrier 24.

The carrier 24 has a locking dog 31 at the upper end of the outer wall 25, the dog 31 being movable by rotation of the carrier 24 into and out of engagement with the teeth 22 of one of the slides 4. The wall 8 contains a spring-loaded catch in the form of a ball 32 and spring 33, the ball 32 being urged by spring 33 towards the side wall of the locking dog 31. The side wall of the locking dog 31 has two circumferentially spaced identations 34 which receive the ball 32 in the locking and unlocking positions respectively of the dog 31. Thus, the dog 31 will be held in the locking or unlocking position by the ball 32. The bottom of the wall 8 has a projection 35 in an arcuate slot 35a in the bottom plate 7, the arcuate extent of the slot 35a limiting angular movement of the projection 35, and hence of the carrier 24 and locking dog 31, to an appropriate range of angular movement sufficient to move the dog 31 between locking and unlocking positions.

When the manhole cover is locked in place, the slides 4 are in their laterally outermost positions, and the locking dog 31 is in engagement with the teeth 22 of one of the slide 4, preventing any radial movement of both slides, since locking one slide 4 locks the drive pinion 21 and hence also the other slide 4.

To remove the manhole cover, the rubber plug 10 is first removed by a prying action with a screw driver inserted between the plug 10 and the side wall of the aperture 9 in the body 1. The closing nut 12 is then removed by rotation with a special tool shaped to fit into the grooves 15 and recesses 16. Next the carrier 24 is rotated to move the locking dog 31 from the locking position in engagement with the teeth 22 of the slide 20 to the unlocking position in which the dog 31 is spaced from the teeth 22. The carrier 24 is then held in the unlocked neutral position by the ball catch 32. The required rotation of carrier 24 is effected by second tool shaped to engage in the Y-shaped aperture in the inner wall 26.

The pinion 21 can then be rotated to move the slides 4 radially inwardly from beneath the ledge 2 of the manhole opening. The pinion 21 is rotated by a third tool shaped to engage in the aperture 21a and recesses 23 of the pinion. The manhole cover is now in its unlocked condition, and can be removed from the manhole opening in the usual way.

Replacement and locking of the cover is effected by reversing the operation described above.

Thus, the described manhole cover can only be removed by the use of three substantially differently shaped tools to unlock and unlatch the slides 4. Therefore, the likelihood of unauthorized removal of the cover is much smaller than if no locking mechanism was provided. It will be noted that the dimensions of the tool-receiving portions of the closing nut 12, carrier 24 and pinion 21 are considerably different, thus requiring the use of three quite differently shaped tools. The tools may be designed to fit one within the other, to provide a compact tool assembly.

Any water seeping into the region of the operating mechanism can drain to the bottom plate 7 from which it can drain out through a central aperture 36 or side apertures 36a in the plate 7. Water collecting between the inner and outer walls 25, 26 of the carrier 24 can drain through holes 37 provided in the connecting web 24a. The top of the body 1 has four arcuate upwardly projecting segments 38 surrounding the central aperture 9 to protect the rubber plug 10.

The needle bearings 27, 28 and the carrier 24 are preferably lubricated with a lithium grease which performs effectively in sub-zero weather to ensure that the mechanism can be operated in winter conditions.

The locking of the slides 4 by the locking dog 31, besides functioning to reduce the likelihood of unauthorized removal of the cover, also serves to prevent the slides 4 being moved to the unlocking position by vibration, for example by traffic passing over the cover.