AU4888000A - Lid for service pits - Google Patents

Description

P/00/011 Regulation 3.2

AUSTRALIA

Patents Act 1990 ooo ooo

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT Invention Title: "LID FOR SERVICE PITS" The following statement is a full description of this invention, including the best method of performing it known to us:

TITLE

LID FOR SERVICE PITS FIELD OF THE INVENTION This invention relates to lids for pits of the kind provided for containing distribution components of utility networks. This invention is particularly although not exclusively concerned with rotationally moulded plastics lids suited to closing subterranean service pits, such as those for housing junctions of telecommunications cables.

BACKGROUND TO THE INVENTION Existing lids for service pits are typically constructed of steel reinforced concrete. In view of typical installation locations for pits, the lids S.are generally required to comply with the relevant standard for footpaths.

15 The Australian Standard for footpath structures includes a one tonne top load test, which results in a bulky design for concrete lids. Concrete lid members are also prone to catastrophic failure when top loads exceed the test load, as might be experienced when a heavy vehicle such as a concrete agitator traverses the pit. Such a failure generally necessitates replacement of the concrete lid.

There are also a number of health and safety issues associated with ::lid members made of concrete or cast from metal. One issue is the risk of skeleto-muscular injuries to service personnel when manually lifting such heavy lids. Accordingly, a lid of reduced weight suited to ease of removal by one person is desirable. Typically conventional lid members include an aperture or apertures allowing insertion of tooling to facilitate lifting and removal of the lid from the service pit. From time to time service personnel have discovered sharps which have been inserted into the pit via such apertures, risking needle stick or similar injuries and possible infection.

Spiders and insects sometimes inhabit service pits posing further problems for personnel. Fireworks have also been known to find their way into service pits. Thus a lid devoid of apertures and generally resistant to entry of foreign bodies is advantageous.

Unauthorised access to service pits by removal of their lids also poses problems for utility operators. The problems include both damage which may be caused to the network or its components and the risk of injury to persons particularly children who might come into contact with energised electrical conductors or the like. Consequently, it would advantageous to discourage unauthorised access by securing the lid member in position closing the service pit.

OBJECT OF THE INVENTION It is an object of the present invention to provide a lid for service pits which ameliorates or overcomes at least some of the problems associated with the prior art.

15 It is another object of the invention to provide a lid of reduced weight *and of enhanced load bearing capabilities.

It is yet another object of the present invention to provide a lid that provides a continuous closure and may be secured in a closed position on a service pit.

Further objects will be evident from the following description.

DISCLOSURE OF THE INVENTION In one form the invention resides in a lid for a service pit, said lid comprising: a moulded plastics body including an upper wall and a reinforcing structure extending below the upper wall; the reinforcing structure having at least one region of intersecting webs including a first series of substantially parallel webs and a second series of substantially parallel webs that intersect with said first series of webs; and retaining means operable to retain the lid in a closed position in relation to the service pit.

The moulded plastics body is preferably formed by a rotational moulding process.

If required, the moulded plastics body may be formed by an injection moulding process.

Alternatively the moulded plastics body may be formed by a blow moulding process.

The moulded plastics body may be either hollow or filled with a low density polymeric foam.

Preferably, the moulded body includes an upright peripheral outer wall extending from the upper wall to the reinforcing structure.

The upright peripheral outer wall of said moulded body suitably includes a seating shoulder adapted in use to engage a support shoulder associated with an inner upright wall of a pit body.

•Preferably the reinforcing structure extends partially over a lower wall S 15 of the moulded plastics body, desirably at least in a central region thereof.

*Suitably the reinforcing structure is integrally formed with said upright peripheral outer wall and said upper wall of the lid.

In preference, said first series of webs intersect with said second S "series of webs at an acute angle.

oooo Preferably said first series of webs and said second series of webs form a regular array.

If required, the intersections of the webs of said first series and said second series are tied by a third series of webs extending transversely of the moulded plastics body.

The webs of said reinforcing structure are preferably formed by an array of upright pyramidal recesses.

Preferably the upright pyramidal recesses are of substantially triangular configuration.

Most preferably the apices of said upright pyramidal recesses are integral with said upper wall of the lid.

If required, said webs are defined between adjacent recesses with upwardly convergent walls forming a buttressed reinforcing structure whereby the webs are resistant to bucking under load.

The retaining means suitably includes at least one movable rod member adapted for selective engagement with a respective socket associated with said pit body.

In use, said rod member(s) may preferably be extended and retracted from the upright outer peripheral wall adjacent said seating shoulder.

Preferably, the retaining means comprises a pair of elongate rod members coupled by a bridge member, which bridge member may be actuated via an aperture in said upper wall to selectively extend and retract said rod members.

The retaining means may include biassing means, such as a coil spring, for biassing said rod members towards an extended position.

S 15 Suitably, the bridge member includes a wall with an oblique portion and a curved portion forming a recess for engagement by a lug to retract said rod members.

If required, the bridge member and rod members act as load bearing members in said reinforcing structure.

Preferably the rod members include chamfered ends for ease of removing or replacing the lid.

Most preferably a cap member is resiliently engageable in the aperture of said upper wall.

The retaining means may include a locking means for securing rod member(s) as required.

BRIEF DETAILS OF THE DRAWINGS To assist in understanding the invention preferred embodiments will now be described with reference to the following figures, in which: FIG. 1 is a perspective view of the top of a service pit fitted with the lid of a first embodiment; FIG. 2 is a perspective view of the bottom of the lid of the first embodiment; FIG. 3 is a top plan view of the lid of the first embodiment; FIG. 4 is a partial sectional front elevational view A-A of the lid shown in FIG. 3; FIG. 5 is a partial sectional end elevational view B-B of the lid shown in FIG. 3; FIG. 6 is a bottom plan view of the lid of the first embodiment; FIG. 7 is a top plan view of the lid of a second embodiment; FIG. 8 is a partial sectional front elevational view C-C of the lid shown in FIG. 7; FIG. 9 is a partial sectional end elevational view D-D of the lid shown in FIG. 7; FIG. 10 is a partial sectional end elevational view showing insertion of an actuating key for opening the lid of the second embodiment; FIG. 11 is a partial sectional end elevational view showing operation of the actuating key; and FIG. 12 is a partial sectional end elevational view showing removal of the lid of the second embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawings of preferred embodiments, like reference numerals refer to like parts. Referring to FIG 1, there is shown a plastic pit 15 of the standard "P5" size, fitted with a lid 10 of a first embodiment of the present S 25 invention. The surface of the upperwall 11 of the lid incorporates an anti-slip surface in the form of a plurality of button-like projections 12. The upper wall 11 includes an aperture 13 through which a portion of a bridge member 14 is visible. It will be appreciated that a conventional concrete pit body may also be fitted with a lid constructed in accordance with the invention.

The underside of the lid 10 is shown in FIG. 2, exposing a reinforcing structure which extends below the upper wall 11 and is bounded by an outer peripheral wall 16. The reinforcing structure includes several regions in the embodiment, namely two end regions 17 and 18, and a centre region 19.

The centre and end regions of the reinforcing structure comprise a plurality of webs, including a first series of webs 20 and a second series of webs 21. The first and second series are disposed at, preferably opposite acute, angles to one another so as to intersect with one another. The intersections 22 of the oppositely angled webs are tied together in the embodiment by a third series of webs 23 which extend laterally of the lid.

The lid 10 includes a moulded plastics body, suitably of polyethylene, which is formed by a rotational moulding process. The upper wall 11, peripheral outer upright walls 16 and the webs 20, 21 and 22 of the reinforcing structure are integrally formed during the moulding process.

Turning to FIGS. 3, 4 and 5, there is shown a plan view and partial sectional views of the moulded plastics' body of the lid 10 to assist 15 understanding of its configuration. The outer walls 16 include a seating **shoulder 24 which is adapted to engage with a support shoulder associated with an inner upright wall of the pit body 15, partially shown in phantom in FIG. 4. It will be appreciated that plastics construction allows improved manufacturing tolerances, thereby facilitated an improved fitting of the lid which minimises ingress of dirt and other foreign matter when the lid is secured.

It can be seen from FIGS. 2 and 4 that the reinforcing structure incorporates arrays of upright pyramidal recesses 26; whereby the webs (such as the webs 23 of the third series) are defined between adjacent S" 25 recesses. The upwardly convergent walls 27 of the hollow webs form buttresses in the reinforcing structure, such that the webs are resistant to bucking under load. The voids 28 in the hollow webs may be filled with a low density polymeric foam in other embodiments for enhanced rigidity. Filling may be achieved via the vents 29 shown in FIG. 2 which are an artifact of the rotational moulding process. The pyramidal recesses 26 are of triangular configuration in the present embodiment, although other embodiments may employ a variety of polygonal configurations or perhaps frustroconical.

FIG. 6 shows the underside of the lid with a retaining means 30, in the form of a pair of rod members 31, for securing the lid in a closed position.

The rods 31 are slidably mounted in openings 33 (see FIG. 4) suitably provided in the webs of the reinforcing structure. The rods 31 are coupled via the bridge member 14, a portion of which may be grasped via aperture 13 in the upper wall 11 enabling the rods to be extended and retracted as desired. The rods and bridge member of the retaining means 30 may accordingly augment the reinforcing structure in regions which do not incorporate webs. In particular the bridge member assists in carrying the tensile stresses delivered to the bottom portion of the moulded body. A portion 34 of the outer peripheral wall 16 in the vicinity of the openings 33 is also enlarged for this purpose.

The rods 31 are shown in the secure position in FIG. 6 wherein the ends thereof would be engaged in cooperating sockets 35 provided in the 5 inner walls of the pit body 15. The rods are shown in the release position in *.FIG. 2, whereby the lid 10 may be subsequently tilted upwardly and moved transversely to effect removal from the pit body. The rods are metallic tubes in the embodiment, although any plate or bar configuration constructed of suitable strength material, including plastics, may be suitable. The securing means also prevent the lid from floating off the pit body and being lost during heavy rainfall or flood conditions. It will be appreciated that, for smaller pits single rod may constitute the retaining means and a cross-bar provided on the rod to facilitate actuation.

A plug member 36, arranged to be resiliently retained within the 0* S 25 aperture 13, may also be provided. The plug is provided with a similarly "buttoned" surface finish to disguise the aperture from the casual observer.

The arrangement suitably requires a tool such as a lever in order to dislodge the plug member. The retaining means most suitably includes a structure which provides for optional locking, such as via a padlock or integral key locking mechanism, as required.

A lid 40 of a second embodiment of the invention is illustrated in FIGs.

7, 8 and 9 of the drawings. The second embodiment includes an aperture 41 of reduced size suitable for receiving an industry standard pit key 37, as depicted in fragmentary form in FIG. 10. A cooperating resilient plug member (not shown) may be provided for closing the aperture, if required.

The retaining means consist of a pair of solid, fibre reinforced plastics rods 42 each removably secured to a bridge member 43, as shown in FIG.

9. The pair of rods 42 are provided with biassing means, in the form of a pair of coil springs 44. The coil springs 44 are disposed between the bridge member 43 and an inner wall 45 of the reinforcing structure of the lid This arrangement biases the rods 42 towards an extended position relative to one side of the moulded body of the lid 40. The ends 46a, 46b of the rods are arranged to engage in sockets 51a, 51 b provided in the inner walls of a service pit 50, here of concrete construction.

The bridge member 43, suitably composed of a wear-resistant plastics material, includes a wall having an oblique portion 47 and a curved portion 15 forming a recess 48. The actuation of the retaining means will now be described with reference to FIGS. 10, 11 and 12. These drawings show a sequence of steps for the release of the retaining means and removal of the lid 40 from pit 50. The moulded plastics lid 40 of the second embodiment is arranged to be released and removed with the aid of a standard pit key 37.

The pit key includes a transverse lug 38 at one end and a handle 39 at an opposite end. As shown in FIG. 10, the lug end of the pit key 37 is inserted through the aperture 41 in the lid 40 (in the orientation allowed by the elongate shape of the aperture). The lug 38 engages the oblique wall 47 such that further insertion causes a partial retraction of the bridge member S0 25 43 and alignment of the lug 38 with recess 48, simultaneously compressing coil springs 44. The pit key 37 is then turned 52 through about 900 to the orientation shown in FIG. 11.

As shown in FIG. 11, the turning of pit key 37 causes further retraction of one end 46a of the rods 42 from their corresponding sockets 51 a whilst the shoulders of the lug 38 engage the recess 48 and a lower wall 49 of the lid The opposite ends 46b of the rods 42 engage deeper in their corresponding sockets. When the pit key 37 is then lifted 53, the lid 40 tends to pivot 54 around the opposite sockets 51b until clearance allows the opposite ends 46b of the rods 42 to disengage from the opposite sockets 51b, as depicted in FIG. 12.

Both ends 41a, 41b of the rods 42 are provided with chamfers. The chamfers allow early disengagement of the rod ends 46 from sockets 51 during pivoting of the lid during removal. It will also be appreciated that, subsequent to the removal of the pit key 37, a lid 40 of the second embodiment positioned on the mouth of the pit 50 may be simply pushed home if two rod ends 46 are first aligned with a set of co-operating sockets 51.

Moulded plastics lids constructed in accordance with the invention have been found, during testing, to withstand up to two tonnes of top load before significant deformation occurs. Unlike concrete lids, the plastics lids 0*00 o. are able to undergo resilient recovery upon removal of extreme top loads.

S 15 This characteristic allows much of the original shape of the lid to be 0 recovered. Typical damage to the plastics lid may include failure of some of o" •,the reinforcing webs, leaving the top wall closure intact. In contrast, concrete lids typically crack and sag, thus breaching the closure and facilitating &see.

::accelerated ingress of water, dirt and otherforeign matter. This performance is coupled with significant weight savings, for example a plastics lid made in accordance with the invention weighs some 5 to 6 Kg, whereas the equivalent size concrete lid weighs from around 30 to 40 Kg.

It will be appreciated that other embodiments may employ injection •°*moulding techniques to form a suitable body for the lid. Tests have shown S. t S06 25 that a foamed plastics construction, achieved by incorporating a blowing agent in the raw plastics prior to moulding can deliver similar performance.

Throughout the specification the aim has been to describe the preferred embodiments of the invention without limiting the invention to any one embodiment or specific collection of features, other than those falling within the scope of any of the appended claims.

Claims (27)

1. A lid for a service pit, said lid comprising: a moulded plastics body including an upper wall and a reinforcing structure extending below the upper wall; the reinforcing structure having at least one region of intersecting webs including a first series of substantially parallel webs and a second series of substantially parallel webs that intersect with said first series of webs; and retaining means operable to retain the lid in a closed position in relation to the service pit.

2. The lid of claim 1 wherein the moulded plastics body is formed by a S. rotational moulding process.

3. The lid of claim 1 wherein the moulded plastics body is formed by an injection moulding process.

4. The lid of claim 1 wherein the moulded plastics body is formed by a blow moulding process.

The lid of any one of claims 1 to 4 wherein the moulded plastics body S. is either hollow or filled with a low density polymeric foam.

6. The lid of any one of claims 1 to 5 wherein the moulded body includes an upright peripheral outer wall extending from the upper wall to the reinforcing structure.

7. The lid of claim 6 wherein the upright peripheral outer wall of said moulded body includes a seating shoulder adapted in use to engage a support shoulder associated with an inner upright wall of a pit body.

8. The lid of either claim 5 or 6 wherein the reinforcing structure is integrally formed with said upright peripheral outer wall and said upper wall of the lid.

9. The lid of any one of claims 1 to 5 wherein the reinforcing structure extends partially over a lower wall of the moulded plastics body, at least in a central region of the lid.

The lid of any preceding claim wherein said first series of webs intersect with said second series of webs at an acute angle.

11. The lid of any preceding claim wherein said first series of webs and said second series of webs form a regular array.

12. The lid of any preceding claim wherein the intersections of the webs of said first series and said second series are tied by a third series of webs extending transversely of the moulded plastics body.

13. The lid of any preceding claim wherein the webs of said reinforcing *structure are preferably formed by an array of upright pyramidal recesses.

14. The lid of claim 13 wherein the upright pyramidal recesses are of *substantially triangular configuration.

The lid of either claim 13 or claim 14 wherein apices of said upright pyramidal recesses are integral with said upper wall of the lid.

16. The lid of any preceding claim wherein said intersecting webs are defined between adjacent recesses with upwardly convergent walls forming a buttressed reinforcing structure whereby the webs are resistant to bucking under load. 13

17. The lid of any preceding claim wherein the retaining means include at least one movable rod member adapted for selective engagement with a respective socket associated with said service pit.

18. The lid of claim 17 wherein, in use, said at least one rod member may be extended and retracted from the upright outer peripheral wall adjacent said seating shoulder.

19. The lid of any preceding claim wherein the retaining means comprises a pair of elongate rod members coupled by a bridge member, which bridge member is actuated via an aperture in said upper wall to selectively extend and retract said rod members.

20. The lid of any preceding claim wherein the retaining means includes biassing means, such as a coil spring, for biassing said rod members towards *an extended position. 0

21. The lid of either claim 19 or claim 20 wherein the bridge member includes a wall with an oblique portion and a curved portion forming a recess for engagement by a lug to retract said rod members. oooo

22. The lid of any one of claims 19 to 21 wherein the bridge member and rod members act as load bearing members in said reinforcing structure.

23. The lid of any one of claims 19 to 22 wherein the rod members include chamfered ends for ease of removing or replacing the lid.

24. The lid of any one of claims 19 to 23 wherein a cap member is resiliently engageable in the aperture of said upper wall.

The lid of any one of claims 19 to 24 wherein the retaining means may include a locking means for securing said at least rod member. 14

26. A lid for a service pit, said lid being substantially as hereinbefore described with reference to FIGS. 1 to 6 of the accompanying drawings.

27. A lid for a service pit, said lid being substantially as hereinbefore described with reference to FIGS. 7 to 12 of the accompanying drawings. Dated this Twenty-seventh day of July 2000 LINPAC ROTATIONAL MOULDINGS PTY LTD by its Patent Attorneys FISHER ADAMS KELLY