GB2115857A

GB2115857A - Improvements in or relating to drag shields

Info

Publication number: GB2115857A
Application number: GB08303006A
Authority: GB
Inventors: Richard Martin; Frank Craig Woolley
Original assignee: ALLPIPE CONSTRUCTION EQUIPMENT
Current assignee: ALLPIPE CONSTRUCTION EQUIPMENT
Priority date: 1982-02-23
Filing date: 1983-02-03
Publication date: 1983-09-14
Also published as: GB8303006D0

Abstract

The invention relates to a drag shield or drag box which comprises two walls (10) arranged in a parallel spaced-apart manner by means of a plurality of transverse members (26,28) each wall being of sheet material formed into a plurality of lengthwise-extending corrugations so as to provide longitudinal grooves or channels (12), a leading edge (16) of the sheet material providing a cutting edge to facilitate passage thereof when towed immediately at the rear of earth excavating equipment. The walls may be constructed of a number of lengthwise extending preformed corrugated panels 14 and are secured to a plurality of upright members (22,24) spanned by the transverse members (26,28). The shield may be towed by a hawser (4) behind the excavating equipment, which may for example be forming a trench, and assists in the shaping and stability of the trench walls to prevent collapse. <IMAGE>

Description

SPECIFICATION Improvements in or relating to drag shields The invention is concerned with improvements in or relating to drag shields.

A drag shield is used in the construction of a trench or other earth excavation where it is necessary to prevent the collapse of newly excavated earth workings, for example including a trench. A drag shield is conventionally of box-like construction and is pulled along by the excavating equipment so as to provide a measure of protection for operators working with the equipment. A drag shield is also known as a drag-box.

The invention provides a drag shield comprising two walls arranged in a parallel spaced-apart manner by means of a plurality of transverse members, each wall being of sheet material formed into a plurality of lengthwise-extending corrugations so as to provide longitudinal grooves or channels, a leading edge of the sheet material providing a cutting edge to facilitate passage thereof when towed immediately at the rear of earthexcavating equipment.

Advantageously, the cutting edges are reinforced at lower end portions thereof. Conveniently, the walls are each formed from a plurality of lengthwise extending panels secured together along lengthwise edge portions thereof in an interlocked side-by-side arrangement.

Preferably the shield arrangement includes a transverse member in the form of a jacking beam adapted to assist in pushing pipe-work together within a newly-formed trench so that the pipe sections may be secured and sealed in position and subsequently buried when the trench is re-closed.

There will now be described an example of a drag shield arrangement according to the invention. It will be understood that the description is given by way of example only and not by way of limitation.

In the drawings: Figure 1 is a perspective view of a drag shield assembly according to the invention; Figure 2 is a fragmentary view of one end elevation of the assembly; Figure 3 is a fragmentary view of the opposite end elevation thereof.

In Fig. 1, a trench 2 is shown having been cut in grassland for the purposes of laying pipe-work. The trench has been formed by conventional excavating equipment (not shown) not forming part of the present invention. A hawser 4 is secured to a drag shield assembly indicated at 6, each of two ends of the hawser being secured to one of two brackets 8, one adjacent each of two walls 10 of the assembly 6. The assembly is thus towed by engaging a portion of the excavation equipment (for example the excavator arm or bucket) with the hawser.

The assembly 6 comprises the two walls 10 arranged in a parallel spaced-apart manner, each wall being corrugated sheet material so as to provide longitudinally extending grooves or channels 1 2. The walls are each constructed from a plurality of preformed panels 14 secured together along edge portions. In the present example the panels are welded for strength in the region of the leading edge 1 6 of each wall 10. Moreover, welded seams prevent any unwanted relative movement between the panels 14 in a direction lengthwise of the shield assembly. The leading edge 1 6 of each wall is arranged to provide a cutting edge which assists in the shaping of the trench after it is cut by the excavation equipment.

Supporting the walls in the manner described are two frame portions each comprising two upright members 22, 24 and a plurality of transverse members 26, 28, respectively. The forward one of the two frame portions includes the brackets 8 each secured to one of the upright members 22. An additional transverse member 27 of the forward frame portion is used as a jacking beam in association with a jack 30 which is capable of applying a horizontally directed thrust for forcing a pipe section into proper contact with its neighbouring pipe section to ensure a satisfactory joint. If desired, the mounting of the jack 30 may be adjustable in a heightwise manner to facilitate accurate alignment of the direction of thrust with the longitudinal centre line of the pipe section.Thus the positioning of the pipe sections in the trench is facilitated, as the sections may be secured and pushed home with the assistance of the shield assembly. It will be observed that the lower portions of the upright members 24 of the rearward frame portions are of slimmer construction to avoid impeding operations when the shield is dragged forward.

It will be apparent that the use of the shield assembly described above is advantageous in several aspects. Firstly, the contour of the cutting edge which is formed by the leading edges of the several pre-formed panels 14 is considerably stronger than would be the case, say, with a straight leading edge. Thus the non-linear edge assists in the progress of the assembly through the earth and tends to dissipate the compressive force from the surrounding earth which might distort a flat surface. Nevertheless, if desired from the point of view of visual appearance, metal sheeting may be welded to the outside surface of the preformed panels 1 4 rearwardly of their leading edge in the position indicated at 32 in Fig. 3.

Secondly the provision of the jacking beam is of considerable benefit, not only in imparting rigidity to the assembly but also in assisting the pipe-laying operation. Thirdly, besides providing protection for operators working in the trench against possible trench collapse or landslip, the wall structure permits of each repair and replacements of component panels.

To facilitate handling and positioning of the shield assembly, the upright members may be provided with lifting brackets or eyes.

It will also be appreciated that the assembly allows for the provision of an access ladder, supports for pipe-laying equipment and materials, or the like received with the interior of the assembly.

In other examples of the invention, not illustrated, the front and/or rear upright members (22 and/or 24) are received in a recess cut into the adjacent region of the inner surface of the walls 10. This arrangement results in an improvement in the amount of clear space within the area occupied by the shield assembly. However, in order to maintain the strength of the walls 10, care must be taken to weld the upright members into the recesses in an adequate manner.

Various modifications may be made within the scope of the invention as defined in the following claims.

Claims

1. A drag shield comprising two walls arranged in a parallel spaced-apart manner by means of a plurality of transverse members, each wall being of sheet material formed into a plurality of lengthwise-extending corrugations so as to provide longitudinal grooves or channels, a leading edge of the sheet material providing a cutting edge to facilitate passage thereof when towed immediately at the rear of earth-excavating equipment.

2. A drag shield according to claim 1, wherein the walls are each formed from a plurality of lengthwise extending panels secured together along lengthwise edge portions thereof.

3. A drag shield according to claim 2, wherein the panels are secured in an interlocked side-by-side arrangement.

4. A drag shield according to either one of claims 2 or 3, wherein the panels are secured together by welding at least in the region of the leading edge of the sheet material.

5. A drag shield as claimed in any one of the preceding claims wherein the cutting edges are reinforced at lower end portions thereof.

6. A drag shield as claimed in any one of the preceding claims wherein a jacking beam is mounted to support a pipe-inserting jack device.

7. A drag shield as claimed in claim 6, wherein means are provided to adjust the height of the mounting of the jack device.

8. A drag shield as claimed in claim 1 wherein the two walls are provided with recesses which receive upright members linked by said transverse members, said upright members being welded into said recesses to maintain the structural strength of the wall.

9. A drag shield as claimed in any one of the preceding claims, wherein metal sheeting is provided as cladding upon the outwardlyfacing surface of each wall, rearwardly of the cutting edge.

10. A drag shield constructed and arranged substantially as hereinbefore described with reference to and as shown in the drawings.