This invention relates to a trenchcover intended for use in covering a trench, hole, cavity or the like formed in a footpath or road surface, and in particular to a trenchcover with a retainer operable to resist sliding movement of the trenchcover relative to the ground surface once positioned over such a trench, hole, cavity or the like.

GB2476873 describes a trenchcover arrangement in which a series of covers are arranged to be positioned side-by-side so as to cover an elongate trench. The underside of each trenchcover, or at least some of the trenchcovers, is provided with a retainer arrangement operable to resist movement of the cover relative to the ground surface upon which the trenchcovers are supported. The retainer arrangements comprise pins or fingers moveable between raised or retracted positions in which they are located within, and do not project from the underside of, the trenchcovers, and lowered or extended positions in which they project from the underside of the trenchcovers.

In use, a trenchcover with the retainer arrangement fitted thereto is positioned over part of a trench to be covered. Those of the pins or fingers which overlie the trench move under the action of gravity to their extended positions, whilst those over the ground surface remain in substantially their retracted positions. The extended pins or fingers closest to the sidewalls of the trench are able to bear against the adjacent sidewall, thereby resisting longitudinal movement of the trenchcover.

Whilst the arrangement described in GB2476873 operates effectively, providing resistance to undesired movement of the trenchcover without requiring a significant amount of work on the part of the operator as the appropriate pins or fingers move automatically to their operative positions upon positioning of the trenchcover, the arrangement does have the disadvantage that the resistance to movement is directional in the sense that only longitudinal movement of the trenchcover is resisted. Lateral movement is not resisted. In the event that the trenchcover covers the entire trench, cavity, hole or the like, then it would be desirable to resist lateral movement as well as longitudinal movement of the trenchcover.

One solution may be to provide the trenchcover with additional retainer arrangements orientated to resist such movement. However, the additional retainer arrangements would add to the cost and complexity of the trenchcover and so this solution may not always be appropriate. It is an object of the invention, therefore, to provide a trenchcover with a retainer arrangement in which at least some of the disadvantages associated with known arrangements are overcome or are of reduced effect.

According to the present invention there is provided a trenchcover comprising a panel adapted to extend over a trench, hole, cavity or the like, in use, the panel being of substantially square or rectangular shape defining longitudinal and lateral axes, and a plurality of retainer arrangements secured to the panel, wherein each retainer arrangement comprises a housing holding captive a row of retainer pins each of which is moveable between a retracted position and an extended position, each pin projecting from the underside of the panel when in its extended position, the row of retainer pins being angled to both the longitudinal axis and the lateral axis of the panel.

By arranging the pins to form a row that is angled to both the longitudinal axis and the lateral axis, it will be appreciated that the pins can serve to resist movement of the trenchcover in both of these directions.

Conveniently, the housing can be retrofitted to a trenchcover panel. Accordingly, it can be offered as an optional feature for new panels, and existing panels can be easily modified to permit movement thereof to be resisted. By way of example, the housing may be secured in position by being screwed to the panel.

The panel conveniently comprises an upper wall formed integrally with a plurality of reinforcing ribs. Some of the ribs conveniently extend in the longitudinal direction and others conveniently extend in the lateral direction, the ribs intersecting with one another to form a series of substantially square or rectangular pockets in the underside of the panel. Each housing conveniently extends across substantially the entire diagonal dimension of an associated one of the pockets. It will be appreciated that as a consequence, movement of the housing relative to the panel is resisted.

The housing is conveniently of molded plastics form. The pins are conveniently of steel form, each pin conveniently including an outwardly extending projection or flange whereby the pin is held captive to the housing.

The invention will further be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a view illustrating a trenchcover with a retainer in accordance with an embodiment of the invention;

Figures 2 and 3 are views to an enlarged scale illustrating part of the trenchcover and retainer; and

Figure 4 is a diagrammatic sectional view illustrating part of the trenchcover and retainer. Referring to the accompanying drawings, a trenchcover is illustrated. The trenchcover comprises a panel 10 of generally rectangular shape, the panel 10 including an upper wall 12 reinforced by an array of reinforcing ribs 14. The panel 10 defines a longitudinal axis 16 and a lateral axis 18. Some of the ribs 14 extend substantially parallel to the longitudinal axis 16, the remaining ones of the ribs 14 extending substantially parallel to the lateral axis 18. The ribs 14 intersect with one another to define a series of generally rectangular pockets 20 in the underside of the panel 10. The upper surface of the panel 10 is of arcuate or curved form, the thickness of the panel 10 tapering from a minimum adjacent the edges of the panel 10 to a maximum adjacent the centre of the panel 10. The ribs 14 are of correspondingly tapered shape, and it will be appreciated that the depths of the pockets 20 also vary accordingly.

The ribs 14 and upper wall 12 are conveniently of molded plastics form, the ribs 14 being molded integrally with the upper wall 12 during the manufacture of the panel 10. If desired, metallic reinforcing members (not shown) may be provided within the ribs 14, enhancing the load bearing capacity of the panel 10.

Within some of the pockets 20 are provided retainer arrangements 22. Each retainer arrangement 22 comprises a plastics molded housing 24 comprising a base 26 carrying a plurality of generally cylindrical bosses 28. Ribs 30 are provided to enhance the rigidity of the housing 24, resisting movement of the bosses 28 relative to the base 26. The bosses 28 are arranged in a single row.

Each boss 28 defines a passage 32 which extends completely though the housing 24, the passages 32 each being of stepped form, defining a reduced diameter region 32a at the end thereof remote from the base 26. Within each passage 32 is provided a respective retainer pin 34. The retainer pins 34 are of solid steel construction, the pins 34 being of stepped cylindrical shape including an increased diameter region 34a at one end thereof. As the bosses are arranged in a row, it will be appreciated that the pins 34 are likewise arranged in a single row.

At its ends, the base 26 is of tapering width, tapering to a point, the point being provided with an opening 36 whereby, in use, a screw 38 can be used to secure the housing 24 to the adjacent ribs 14 of the trenchcover.

As illustrated, the housing 24 of each retainer arrangement 22 is arranged to extend along the diagonal dimension of the associated pocket 20, extending along substantially the full length of the diagonal so that each end of the housing 24 bears against the intersection of a pair of the ribs 14. In order to accommodate any variations in the depth of the pocket 20 adjacent the ribs 14, the base 26 of the housing 24 is conveniently shaped such that it is spaced from the upper wall 12 in this region. As mentioned above, the housing 24 is secured in position by screws 38 which extend through the openings 36 and into the adjacent ribs 14. The screws 38 are conveniently of the self-tapping type.

In use, when the trenchcover is positioned over a hole, trench, cavity or the like in a footpath or roadway with part of each retainer arrangement 22 located over the trench and part located over the adjacent ground surface, it will be appreciated that those of the pins 34 located over the trench will tend to drop under the action of gravity to an extended position in which they project from the underside of the trenchcover, projecting out of the associated pocket 20. The interaction between the regions 34a of the pins 34 and the reduced diameter parts 32a of the passages 32 ensures that the pins 34 are held captive within the passages 32, limiting the distance through which the pins 34 can move. Those of the pins 34 located over the adjacent ground surface will be unable to move to their extended positions, remaining substantially in their retracted positions, as the interaction between the ends of these ones of the pins 34 and the ground surface resists such movement.

It will be appreciated that once so positioned, movement of the trenchcover in both the longitudinal direction and the lateral direction will be resisted by the interaction between those of the extended pins 34 closest to the side walls of the trench with the trench wall. Loads experienced by the pins 34 are transmitted to the housing 24 and trenchcover via the interaction between the ends of the housing 24 and the ribs 14.

In accordance with the invention, the pins 34 are arranged in a row, the row being angled to both the longitudinal axis and the lateral axis. In the present embodiment, the row extends along the diagonal of the associated one of the pockets 20. By orientating the row to be angled to the longitudinal and lateral axes, it will be appreciated that the movement of the pins 34 between their extended and retracted positions as the trenchcover is positioned over the trench automatically adjusts the retainer arrangement to both the width and the length of the hole, trench or the like, and so resists movement of the trenchcover in both the longitudinal direction and the lateral direction. The provision of additional retainer arrangements to resist movement in both directions is thus avoided.

It will be appreciated that installation of the retainer arrangement 22 to the trenchcover panel 10 is straightforward, and that with an appropriate design of the housing 24, the retainer arrangement 22 can be retrofitted to existing panels 10, if desired. As mentioned above, in use of the trenchcover, the pins 34 move automatically under the action of gravity as the trenchcover is moved into position, and so no subsequent step of adjusting a retainer has to be conducted for the retainer to operate. In the arrangement illustrated, the housing 24 is of symmetrical shape, and as a result, the retainer arrangement can be installed along either diagonal of the associated pocket 20.

As shown in Figure 1 , the diagonally arranged retainer arrangements 22 may be spaced apart from the centre of the trenchcover panel. In that case the panel may be provided with a marking indicating the minimum trench size for which the trenchcover is intended to be used. For instance, the retainer arrangements 22 may diagonally extend from a 200mm x 350mm rectangular area and the panel may be marked on its underside to indicate a minimum trench size of 220mm by 350 mm.

Whilst the description hereinbefore is of one specific embodiment of the invention, it will be appreciated that a wide range of modifications and alterations may be made thereto without departing from the scope of the invention. Whilst the description is of a trenchcover of generally rectangular shape, it will be appreciated that the invention is also applicable to other shapes of trenchcover.