GB2217750A - Trench shoring plates and struts with leaf springs - Google Patents

Description

2217750 1 M&C FOLIO: 230P56333 WANGDOC: 0483L "APPARATUS FOR SUPPORTING

THE WALLS OF TRENCHES" This invention relates to apparatus for supporting the walls of trenches. or other excavations, and of the kind generally designated as a trench shoring box and comprised of two opposed shoring panels provided with vertically directed support members to which struts of adjustable length extending substantially normally to the shoring panels are horizontally pivotally attached so that the shoring panels and struts can be relatively displaceable in the vertical direction as excavation progresses.

It has been appreciated that during normal handling of a fully assembled trench shoring box there is considerable differential movement between each of the shoring panels and due to the weight of the assembly unless some damping restraint is provided considerable shock forces are applied at the limits of angular movement between the struts and the panels. Various damping assemblies for this purpose have hitherto been employed, such as for instance hydraulically operating dampers or by the provision of two helical springs positioned equally one each side of each strut centre line, but these have not proved entirely satisfactory.

2 For instance with a damping system embodying two helical springs. one spring only at a time can contribute to the damping suction. Also in this damping system the stiffness of the damper is fixed by the geometry of the spring which cannot easily be changed to accommodate extremes of use.

The present invention has been devised with the general object of providing a damping system which does not have the above mentioned disadvantages.

The present invention has also been devised to provide an improved form of adjustable length strut which permits rapid adjustment of length and which being self-contained is resistant to deterioration in extreme environmental conditions.

In accordance with the invention, apparatus of the kind referred to is characterised in that end elements of each strut are additionally resiliently coupled to the shoring panels by leaf springs in order to dampen angular movement between the struts and the panels.

In order however that the invention may be more readily understood reference should be made to the following description of a preferred embodiment which is illustrated in the accompanying drawings. In these drawings:- 3 Fig. 1 is a side elevation, partly in section, of an adjustable length strut for attachment between opposite shoring panels; Fig. 2 is a plan view of a shoring panel end post showing the mode of connection of an adjustable length strut thereto; Fig. 3 is an elevation view on the inside of a shoring panel; and Fig. 4 is a section on line X-X of Fig. 3.

Referring now to the drawings, Fig. 1 shows a heavy duty strong box strut which comprises a central cylinder 1 formed in two half sections A, B, with abutting flanges 2, 3 secured together by bolts 4 and nuts 5 and each formed from end to end internally with a quick feed screw thread 6. Retained within the cylinder parts A and B, are the correspondingly screwthreaded cylindrical heads 7, 8 of a pair of thrust rods 9, 10. Attached to the outward end of each of these thrust rods 9, 10 is a perpendicular plate 11 which supports a central part of a multi-leaf spring 12 which is clamped thereto by a second plate 13 by means of bolts 14 and nuts 15. Attached to the outward side of each plate 11 is a U-shaped saddle 16 by which the strut is swivelably 4 mounted on an horizontal pin 17 which, as shown in Fig. 2, extends between a pair of end post plates or brackets 18 which project at right angles from, and which are secured to, an end post 19 fixed to a shoring panel 20 5 as shown in Fig. 2.

The ends of each leaf spring are located in slotted tubes 21 which are welded between the end post plates or brackets 18 of the side panel 20, these details being shown more clearly in Fig. 2, and also in Figs. 3 and 4, 10 wherein the centre lines C of the struts are indicated.

Rapid extending or retracting of each strut is effected by turning the cylinder 1 in a clockwise or counter-clockwise direction by use of any suitable tool such as for instance a lever arm inserted into one or other of four radial openings in a collar 22 which is welded to the cylinder half section B. In Fig. 1 there is also illustrated by a chaindashed line a lifting bracket 10 which is attached only to the topmost extension strut.

It will be appreciated that adjustment of the length of a strut is based on the turnbuckle or bottlescrew principle but it is a requirement that strut release should be rapid. A satisfactory screw thread pitch for the elements A, B, 7, 8 would be one which alters the 9.

strut length by 48 mm for each revolution of the cylinder A, B. The construction is of course such that none of the screw-threading is exposed in use to the environment in which the shoring box operates. Also, in the formation of the screw threading, the minimum amount of metal is removed from the cylinders A, B consistent with the maximum designed loadcarrying capacity of the strut. This should provide greater local strength which will minimise the possibility of dents being formed in the cylinders during normal use of the struts.

It is characteristic of the invention, and advantageous that:

a) Any angular movement of the strut results in a reaction from each leaf of the spring at both ends of the strut; b) The stiffness of each spring is easily changed by the addition or reduction of the number of leaves; c) The spring as drawn will give for each leaf the maximum stiffness, but if the shape is changed to approach the configuration of constant 6 strength a much reduced stiffness can be obtained where necessary for the same thickness.

d) To guard against the spring leaves breaking a guard leaf of a ductile, steel may be fitted on the clear side of the assembly to prevent a piece of the more elastic and brittle steel spring from flying out and causing personal injury.

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Claims (6)

1. Apparatus of the kind referred to for supporting the walls of trenches or other excavations charactered in that end elements of each strut are additionally resiliently coupled to the shoring panels by leaf springs in order to dampen angular movement between the struts and the panels.

2. Apparatus as claimed in Claim 1 in which the central part of each leaf spring is secured to an end element of a strut and the ends of the leaf springs are coupled to the shoring panels.

3. Apparatus as claimed in Claim 1 or Claim 2 wherein at least some of the leaf springs are comprised of a plurality of leaves of varying length and/or thickness.

4. Apparatus as claimed in any of Claims 1 to 3 in which the ends of the leaf springs are received within, and located by, slotted tubes which are fixed indirectly to the shoring panels.

5. Apparatus as claimed in any of Claims 1 to 4 wherein each strut comprises a central internally screw-threaded cylinder and a pair of thrust rods which project one from each end of the cylinder and each having, within 8 the cylinder, an externally screw-threaded head which engages the screw threads of the cylinder, whereby rotation of the cylinder in one direction or the other causes extension or retraction of the thrust rods relative thereto in order to vary the overall length of the strut.

6. Apparatus for supporting the walls of trenches or other excavations substantially as hereinbefore described with reference to, and as shown in, the 10 accompanying drawings.

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