GB2249114A

GB2249114A - Trench box for shoring

Info

Publication number: GB2249114A
Application number: GB9022910A
Authority: GB
Inventors: John Collins
Original assignee: Mabey Hire Co Ltd
Current assignee: Mabey Hire Co Ltd
Priority date: 1990-10-22
Filing date: 1990-10-22
Publication date: 1992-04-29
Anticipated expiration: 2010-10-22
Also published as: GB2249114B; GB9022910D0

Abstract

A trench box for shoring comprises two panels (10) interconnected by four extendable and retractable struts (30, 32) in two pairs. Between each pair of struts (30, 32) is a multi-leaf spring (38), which is connected at mutually opposite &cirf& nds (40, 42) of the leaf spring (38) to the end parts (26, 28) of the two struts (30, 32). The connection of the leaf spring (38) 12 to each strut (30, 32) is rigid, so that where the leaf spring (38) adjoins the struts (30. 32) it extends perpendicularly to the strut. Since the pair of struts (30, 32) are always parallel, bending stress induced in the leaf spring (38) due to pivoting of either strut (30, 32) is transmitted through the leaf spring (38) to the other strut (32, 30) so as to effectively stiffen the pivotal connections of the struts (30, 32) to the panels (10). <IMAGE>

Description

TRENCH BOX FOR SHORING This invention relates to a trench box for shoring, comprising a plurality of selectively extendable and retractable structs extending between and connected pivotally to two mutually opposite panels, to vary the spacing between the panels for shoring, and a plurality of leaf springs connected to the struts so as to damp pivotal movement of the struts relative to the panels.

Such a trench box may be used, for example, in shoring up an excavation.

The invention provides a trench box as claimed in each of the claims, to which reference is directed.

The invention will be described by way of example with reference to the accompanying drawings, wherein: Fig. 1 illustrates part of a trench box embodying the invention, showing one panel with a post at the back of the panel, two ends of struts connected to the post and a leaf spring which is connected at mutually opposite ends of the leaf spring to the two struts; and Fig. 2 illustrates diagramatically the deflection of the leaf spring with pivotal deflection of the struts.

Referring to the drawings, the trench box embodying the invention comprises two panels 10, figure 1 showing a part of one of the panels 10 only. Each panel 10 comprises an array of horizontal members 12 arranged one on top of another and welded together. Each horizontal member comprises a base element 14, two upstanding elements 16, 18 extending upwardly from inside and outside edges of the base element 14 respectively, and two flange elements 20, 22 extending towards each other from top edges of the two respective upstanding elements 16, 18. The flange elements 20, 22 of each lower one of two adjacent horizontal members 12 are welded to the base element 14 of the upper horizontal member 12.

A vertical post 24 is welded to at least some of the horizontal members 12 at the back of the panel.

Four selectively extendable and retractable struts there being shown only end parts 26, 28 of only two struts 30, 32 - extend between and are connected pivotally to the two mutually opposite panels 10, to vary the spacing between the panels 10 for shoring.

Figure 1 shows the ends 26, 28 of the two struts 30, 32 connected to the post 24 via two respective rocker units 34, 36 which permit pivoting of the struts 30, 32 relative to the panel 10. Since the struts 30, 32 are both connected at opposite ends to the two panels 10, they remain substantially mutually parallel at all times, disregarding non-parallelism caused by the struts 30, 32 being possibly of slightly non-equal lengths in a particular situation.

A (multi-leaf) leaf spring 38 is connected to the end parts 26, 28 of the two struts 30, 32 so as to damp pivotal movement of the struts 30, 32 relative to the panels 10. More particularly, the leaf spring 38 is connected at mutually opposite ends 40, 42 of the leaf spring to the end parts 26, 28 of the two struts 30, 32 and extends perpendicularly to each strut where it adjoins the strut. More particularly, the connection of the leaf spring 38 to each strut 30, 32 is rigid, so that where the leaf spring 38 adjoins the strut 30, 32 it extends perpendicularly to the strut.Since the struts 30, 32 are constrained, by virtue of their connections between the two panels 10, to be always mutually parallel, any pivotal movement of either strut 30, 32 relative to the panel 10 is accompanied by similar pivotal movement of the other strut 32, 30 in the same direction, and since the leaf spring 38 is connected rigidly to the two struts 30, 32, so as to extend perpendicularly to each strut where it adjoins that strut, the result of pivotal deflection of the two struts 30, 32 is to deform the leaf spring 38 in the manner illustrated in figure 2, from which it will be apparent that bending stress induced in the leaf spring 38 due to pivoting of either strut 30, 32 is transmitted through the leaf spring 38 to the other strut 32, 30, in such a manner as to effectively stiffen the pivotal connections of the struts 30, 32 to the panels 10.

The above description, of the two struts 30, 32 and the interconnecting leaf spring 38, also applies to another two struts (not shown) with their similarly interconnecting leaf spring (also not shown), since the panel is interconnected by four struts and not just by two struts. It will be appreciated that the leaf spring (not shown) between the other two struts (not shown) will similarly stiffen their pivotal connections to the panels.

Claims

Claims:-

1. A trench box comprising a plurality of selectively extendable and retractable struts extending between and connected pivotally to two mutually opposite panels, to vary the spacing between the panels for shoring, and a plurality of leaf springs connected to the struts so as to damp pivotal movement of the struts relative to the panels, characterised in that each leaf spring is connected to a plurality of said struts so that bending stress induced in the leaf spring due to pivoting of one strut is transmitted through the leaf spring to another strut, so as to effectively stiffen the pivotal connections of the struts to the panels.

2. A trench box as claimed in claim 1, wherein each leaf spring is connected at mutually opposite ends of the leaf spring to two struts.

3. A trench box as claimed in claim 1 or 2, wherein each leaf spring extends perpendicularly to each strut.

4. A trench box as claimed in claim 1, 2 or 3, wherein each panel comprises an array of horizontal members arranged one on top of another and welded together, each horizontal member comprising a base element, two upstanding elements extending upwardly from inside and outside edges of the base element respectively, and two flange elements extending towards each other from top edges of the two respective upstanding elements, the flange elements of each lower one of two adjacent horizontal members being welded to the base element of the upper horizontal element.

5. A trench box as claimed in claim 4 dependant from at least claim 2, wherein a vertical post is welded to at least some of said horizontal members and wherein said two struts and said leaf spring are connected to said post.