AU2019203012A1 - A Light Weight Lid Arrangement for a Manhole or Pit - Google Patents

Abstract

5590AC-AU A light weight lid arrangement for a security manhole or pit (1) is disclosed. The arrangement has a peripheral frame (12) with two similar lids (3, 4) each of which is pivotally mounted on the frame and movable between a first substantially horizontal 5 position and a second substantially vertical position. The lids have a complementary shape such that when both said lids are in the substantially horizontal position the central opening is closed, the central opening being open when both lids are in the substantially vertical position. The lid (4) has a projecting flange (8) which extends partially underneath the lid (3) when both lids are in the substantially horizontal 10 position; whereby the lid (3) must be raised before the lid (4), said lid (4) must be lowered before the lid (3), locking the lid (3) to said frame (12) locks both lids because of the engagement the flange (8) and the lid (4), and 15 each of the lids (3, 4) is of approximately the same surface area so that raising either one of said lids involves approximately half of the manual effort involved to substantially simultaneously manually raise both lids. ,1% /o

Description

A Light Weight Lid Arrangement for a Manhole or Pit

Field of the Invention

The present invention relates to lids or covers for manholes or pits.

Background Art

Manholes or pits have been used for many years to house infrastructure such as cables, pipes, municipal equipment, etc. which are normally buried below ground. Such manholes or pits are provided with a lid or cover to close the access opening into the manhole or pit. Hitherto it has been regarded as being advantageous if the lid or cover has been heavy since this discourages unauthorised opening and hence unauthorised access. Consequently, such lids or covers have hitherto been made of heavy materials such as cast-iron or concrete. In addition, such heavy covers are also desirable for manholes used for drains, since such heavy covers are able to resist opening pressures such as can arise in drains where the pressure created by upstream backed up water can be sufficient to raise downstream drain covers. Thus, hitherto weight has been a desirable feature of such covers or lids.

Genesis of the Invention

However, in recent times many jurisdictions have introduced regulations having an occupational health and safety aspect. In particular, maximum weights or loads which can be manually lifted are now prescribed and/or introduced as industry norms. Accordingly, there is now an incentive to reduce the weight of the lids or covers for manholes or pits without reducing their structural strength.

Summary of the Invention

In accordance with a first aspect of the present invention there is disclosed a light weight lid arrangement for a security manhole or pit, said arrangement comprising a peripheral frame having a central opening and having the same configuration as a rim of said manhole or pit which is to be installed substantially flush with a ground level, a first lid pivotally mounted on said frame and movable between a first substantially horizontal position and a second substantially vertical position, a second lid pivotally mounted on said frame and movable between a first substantially horizontal position and a second substantially vertical position, said first and second lids having a

5590AC-AU complementary shape such that when both said lids are in said substantially horizontal position said central opening is closed, said central opening being open when said first and second lid is are both in said substantially vertical position, and one of said lids having a projection which extends partially underneath the other of said lids when both said lids are in said substantially horizontal position; whereby the other of said lids must be raised before said one lid, said one lid must be lowered before the other of said lids, locking said other lid to said frame locks both lids because of said engagement of said projection and said other lid, and each of said lids is of approximately the same surface area whereby raising either one of said lids involves approximately half of the manual effort involved to substantially simultaneously manually raise both said lids.

Brief Description of the Drawings

Two embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Fig. 1 is a schematic perspective view from above showing the twin manhole lids of both embodiments,

Fig. 2 is a perspective view from the underside showing the twin manhole lids ofFig. 1,

Fig. 3 is a plan view showing the twin lids of Figs. 1 and 2 mounted in a steel frame which is encased in a concrete plinth,

Fig. 4 is a vertical cross-sectional view through a first embodiment of the hinge of one of the closed lids,

Fig. 5 is a vertical cross-sectional view showing the lid ofFig. 4 in the process of being opened,

Fig. 6 is a vertical cross sectional view showing the lid ofFig. 4 fully opened, Fig. 7 is a view similar to Fig. 4 but of a hinge of a second embodiment, Figs. 8 and 9 are views similar to Figs. 5 and 6 but of the hinge of the second embodiment,

Fig. 10 is a schematic plan view of a strip of sheet steel showing the twin lids being cut therefrom in a scrap less manner, and

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Fig. 11 is a plan view showing the lids cut from the strip of sheet steel of Fig.

10.

Detailed Description

As seen in Fig. 1, a square manhole 1 takes the form of a concrete plinth 2 within which are located twin lids 3 and 4. Each of the lids 3, 4 has an inverted U-shaped handle 6 and the same basic shape. The lids 3, 4 differ in that the lid 3 has a lock 7 and the lid for has a roughly S-shaped flange 8 which enables the lid 4 to support the lid 3. As schematically illustrated in Fig. 1 the upper surface of the lids 3, 4 is provided with an anti-slip checker plate pattern 10.

Turning now to Fig. 2, the underside of the lids 3, 4 are reinforced with a multiplicity of ribs 12. The layout of the ribs 12 is the same for both lids 3, 4 and thereby simplifying the construction of the lids 3, 4. As seen in Fig. 3, the twin lids 3, 4 are mounted within a square frame 12 which is connected with reinforcing steel 13 which not only strengthens the frame 12 but reinforces the concrete of the plinth 2.

Because of the flange 8, it is necessary that the lid 3 be opened or raised first, and thereafter the lid 4 the opened or raised second. This order is reversed during closing so that the lid 4 is lowered or closed first, and then the lid 3 is lowered or closed second. In the closed condition, the flange 8 of the lid 4 partially supports the lid 3. Furthermore, the lock 7 by locking the lid 3, also effectively locks the lid 4 since the flange 8 does not permit the lid 4 to be raised past the lid 3.

The details of the first embodiment of the mounting of the lids 3, 4 within the steel frame 12 are illustrated in Figs. 4-6. The frame 12 is provided with two longitudinally extending hinge pins 14, one of which extends along the length of the two opposite sides 15, 16 (Fig. 3) of the frame 12. Only one of the hinge pins 14 is illustrated in Figs. 4-6. Rotatably mounted on the hinge pin 14 are a number of generally U-shaped brackets 18. One arm 21 of each bracket 18 is able to rotate around the stationary hinge pin 14. In a first embodiment, the other arm 22 of each bracket is fixed to the corresponding lid 3, 4. As a consequence, the corresponding lid 3, 4 is able to rotate from the closed position illustrated in Fig. 4, through the partially open position

5590AC-AU illustrated in Fig. 5, and into the substantially vertical open position illustrated in Fig. 6 as a consequence of the rotation of the arm 21 relative to the stationary frame 12 and hinge pin 14. Fixing the arm 22 to the lid 3, 4 restricts the opening of the lid to just past the vertical. That is, the angle Θ is approximately 80°. In this position, the centre of gravity of the lid 3, 4 lies to the outside of the hinge pin 14 and so the lid 3, 4 remains open due to the gravitational force it experiences.

In a second embodiment, illustrated in Figs. 7-9 the brackets 18 are fabricated from two pieces. The arm 22 is connected to the lid 3, 4 by means of a second hinge pin 24. In addition, the two arms 21 and 22 are hinged together by means of a third hinge pin 34. As a consequence of this construction, the lid 3, 4 is able to rotate around the second arm 22 of the bracket 18 so as to reduce the angle Θ illustrated in Fig. 9 to essentially zero. That is, each of the lids 3, 4 is able to be rotated into a substantially horizontal position.

Furthermore, as best seen in Fig. 2, each of the lids 3, 4 has a pair of protruding fingers 25 each of which is engageable with a corresponding recess 26 (Fig. 6) in order to strengthen the lids 3, 4 in the region of the hinge pins 14 and the sides 15,16 of the frame 12. In particular, this means that the weight of a motor vehicle, for example, is not required to be supported by the hinge arrangement.

Turning now to Figs. 7 and 8, it will be seen that the complementary shapes of the twin lids 3, 4 enable them to be cut from a strip 28 of checker plate steel in an essentially scrap less arrangement thereby contributing to the low manufacturing cost for the twin lids. So not only is an occupational health and safety advantage achieved in that the weight of any one of the lids 3, 4 is only about 11 kg, but the cost of manufacturing the lids 3, 4 is relatively low.

The foregoing describes only one embodiment of the present invention and modifications, obvious to those skilled in the manhole arts, can be made thereto without departing from the scope of the present invention.

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The term “comprising” (and its grammatical variations) as used herein is used in the inclusive sense of “including” or “having” and not in the exclusive sense of “consisting only of’.

Claims (7)

1. A light weight lid arrangement for a security manhole or pit, said arrangement comprising a peripheral frame having a central opening and having the same configuration as a rim of said manhole or pit which is to be installed substantially flush with a ground level, a first lid pivotally mounted on said frame and movable between a first substantially horizontal position and a second substantially vertical position, a second lid pivotally mounted on said frame and movable between a first substantially horizontal position and a second substantially vertical position, said first and second lids having a complementary shape such that when both said lids are in said substantially horizontal position said central opening is closed, said central opening being open when said first and second lid is are both in said substantially vertical position, and one of said lids having a projection which extends partially underneath the other of said lids when both said lids are in said substantially horizontal position; whereby the other of said lids must be raised before said one lid, said one lid must be lowered before the other of said lids, locking said other lid to said frame locks both lids because of said engagement of said projection and said other lid, and each of said lids is of approximately the same surface area whereby raising either one of said lids involves approximately half of the manual effort involved to substantially simultaneously manually raise both said lids.

2. The arrangement as defined in claim 1 wherein said first and second lids are cut from a strip of sheet material in a substantially scrap less configuration.

3. The arrangement as defined in claim 2 where in each of said lids comprises a long rectangular portion and a short rectangular portion, said two portions being joined by an intermediate portion having a complementary profile, and the width of said strip of sheet material comprises the length of said long rectangular portion plus the length of said short rectangular portion.

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4. The arrangement as defined in claim 3 wherein said complementary profile is a straight line angled to the longitudinal axis of said strip of sheet material.

5. The arrangement as defined in any one of claims 1-4 wherein each of said lids includes an over centre hinge means which permits each of said lids in said substantially vertical position to be tilted during raising beyond the vertical, whereby gravity holds each of said lids in said substantially vertical position.

6. The arrangement as defined in any one of claims 1-4 wherein each of said lids includes a double hinge means which permits each of said lids to be opened and moved beyond the substantially vertical position.

7. The arrangement as defined in claim 5 or 6 wherein said hinge means includes a pair of fingers each engageable with a corresponding stationary recess associated with said frame.