GB1573268A

GB1573268A - Drive shield for driving trneches

Info

Publication number: GB1573268A
Application number: GB4730977A
Authority: GB
Original assignee: Gewerkschaft Eisenhutte Westfalia GmbH
Current assignee: Gewerkschaft Eisenhutte Westfalia GmbH
Priority date: 1976-11-17
Filing date: 1977-11-14
Publication date: 1980-08-20
Also published as: ES457658A1; FR2371553B1; JPS5363724A; DE2652327A1; JPS5527958B2; FR2371553A1

Description

(54) DRIVE SHIELD FOR DRIVING TRENCHES (71) We, GEWERKSCHAFT EISENHUTTE WESTFALIA, a body corporate and existing under the laws of the Federal Republic of Germany, of 4670 Lunen, Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement-: This invention relates to a drive shield for use in driving trenches, and in particular for driving trenches for pipe-laying operations.

One known type of drive shield for use in driving trenches for pipe-laying operations is constituted by a pair of knife shields. Each knife shield comprises a plurality of elongate members (planks or knives) which are mounted in parallel, sideby-side relationship on a support frame.

Each plank is provided with a doubleacting hydraulic ram which is disposed between the support frame and the plank in question. The planks of each knife shield can be advanced relative to their frame either singly or in groups by means of their hydraulic rams. In this type of drive shield, the two support frames are coupled together.

In use, the front knife shield supports the trench walls in the region close to the working face, whereas the rear knife shield supports the trench walls in a rear working area in which pipe sections are lowered into the trench and joined up to the pipeline already laid. With this type of drive shield, both support frames are advanced together after all the planks of both shields have been advanced. This advance of the support frames is carried out by subjecting the hydraulic rams, which are interposed between the planks and the support frame of the front knife shield, to pressurised hydraulic fluid in the reverse direction to that in which pressurised hydraulic fluid is applied to these rams to advance the associated planks. The planks of the knife shields themselves form the abutment for the advance of the support frames owing to their frictional contact with the trench walls.Unfortunately, it is possible for the force required to advance the support frames to exceed the frictional force between the planks and the trench walls. In such cases, the support frames cannot be advanced by the full length of the working stroke of the hydraulic rams because the planks slip by a certain amount.

The present invention provides a drive shield for use in driving trenches, the drive shield being constituted by a plurality of elongate members mounted in a parallel, side-by-side relationship on a support frame, each of the elongate members being movable relative to the support frame, wherein at least part of the support frame is mounted on skids along which it can slide or roll in the direction of trench advance.

The invention also provides a drive shield for use in driving trenches, the drive shield being constituted by first and second knife shields positioned one behind the other, each knife shield having a plurality of elongate members mounted in a parallel, side-by-side relationship on a respective support frame, each of the elongate members being movable relative to its support frame, and the two support frames being coupled together, wherein one of the support frames is mounted on support means relative to which it is movable in the direciton of trench advance.

Preferably, the second, rear support frame is said one support frame. In view of the fact that the rear support frame can be advanced in a sliding or rolling manner relative to the support means, the power which would otherwise be required for this advancing movement is substantially reduced, so that, as a result of the considerably more favourable distribution of forces, the front support frame and the rear support frame can be advanced jointly by means of hydraulic rams acting between the elongate members of the front knife shield and its support frame. This advance of the support frames is accomplished without any risk that the frictional force between the elongate members and the trench walls will be exceeded and so there is no danger of the elongate members slipping.

Advantageously, the support means is constituted by skids along which said one support frame can slide or roll. Each skid may be coupled, preferably pivotally, to a respective one of the elongate members of the other knife shield. This pivoted connection permits the shields to adapt to any unevenness of the trench floor.

Preferably, there are two skids, one skid being located at each lateral edge of the drive shield. This has the advantage that the trench floor is largely totally unblocked in the region where pipe sections are lowered into position.

Advantageously, each skid is provided with a profiled guide rail which co-operates with correspondingly shaped guide elements provided on said one support frame. Each guide rail may have a guide surface of part cylinderical configuration and each guide element has a correspondingly shaped concave guide surface. In this case, each guide element may be a shoe which, in use, slides along the corresponding guide rail. Alternatively, each guide element is a roller which, in use, rolls along the corresponding guide rail.

One form of trench drive shield constructed in accordance with the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a part-sectional side elevation of the drive shield; Figure 2 is a cross-section taken on the line II--II of Figure 1; and Figures 3 and 4 are side elevations, on an enlarged scale, of alternative supports for the drive shield.

Referring to the drawings, Figure 1 shows a drive shield constituted by a front (or leading) knife shield 10 and a rear (or following) knife shield 11. The front knife shield 10 has a support frame 12 constituted by spaced frame members 13 and 14 which are held together by means of braces 15. The frame 12 supports a plurality of steel knives (or planks) 16 which in turn support the two side walls 17 and 18 of the trench. Double-acting hydraulic rams 19 are provided for advancing the planks 16, a ram being pivotally connected between each plank and the frame member 14.

The front knife shield 10 also has base plates 20 which rest on the trench floor 21.

These plates 20 can also be advanced by means of hydraulic rams 20' which are supported on the frame 12.

The rear knife shield 11 is similar to the front knife shield 10 in that it has a support frame 22 formed from frame members 23, 24 and 25 which are rigidly connected to one another. The frame members 23, 24 and 25 are pivotally connected, at their upper ends to bars 26 which are connected, by means of universal joints 26', to the support frame 12 of the front knife shield 10. The two support frames 12 and 22 thus form a compact frame structure which can be advanced in the trench advance direction V as a unit.

The rear knife shield 11 also has steel planks 27 which secure the trench walls 17 and 18 in the region where pipe sections are lowered and joined up to pipe line already laid. The planks 27 form tails or rear extensions of the planks 16 of the front knife shield 10, and are preferably pivotally connected to the planks 16.

The support frame 22 of the rear knife shield 11 is advanced in a sliding or rolling manner on a pair of skids 28 which are mounted on the trench floor 21 adjacent to the side walls 17 and 18. Each of the skids 28 carries a profiled guide rail 29 on which the support frame 22 is supported and guided by means of guide elements 30. In the embodiment of Figures 1 to 3, these guide elements 30 are rollers, and they are mounted at the base of the frame members 23, 24 and 25. As can be seen in Figure 1, each of the skids 28 is connected by means of a universal joint 31 to the base plates 20 of the support frame 12 of the front knife shield 10.

In use, the planks 17 and 27 are all advanced, either singly or in groups, in the direction V by pressurising the rams 19. As soon as all the planks 16 and 27 have been advanced, the support frames 12 and 22 are advanced by subjecting the rams 19 to pressure in the reverse direction. During this advance of the frame structure, the rear support frame 22 rolls forward on the skids 28, whereas the front support frame 12 is guided slidingly on the planks 16 and the base plates 20. It will be apparent that, on advancing the frame structure 12, 22, the rams 19 are supported by the steel planks 16 which in turn are held against the trench walls 17 and 18 by friction.As a result of the sliding and rolling contact between the frame structure 12, 22 and the skids 28, planks 16 and plates 20, the frictional force between the planks and the trench walls cannot be overcome and so trouble-free advance of the heavy frame structure is ensured.

The profiled guide rails 29 are constituted by cylindrical half-pipes 29' (see Figure 3), in which case the rollers 30 are formed with a concave groove 32. This configuration helps to prevent fouling or blocking of the guides. Instead of rollers 30, sliding shoes 30' (see Figure 4) may constitute the guide elements. These shoes 30' may also be formed with concave grooves so as to mate with rails such as 29'. Alternatively, they may slide directly on the skids 28 (see Figure 4).

WHAT WE CLAIM IS: 1. A drive shield for use in driving trenches, the drive shield being constituted by first and second knife shields positioned one behind the other, each knife shield having a plurality of elongate members mounted in a parallel side-by-side relationship on a respective support frame, each of the elongate members being movable relative to its support frame, and the two support frames being coupled together, wherein one of the support frames is mounted on support means relative to which it is movable in the direction of trench advance.

2. A drive shield as claimed in claim 1, wherein the second, rear support frame is said one support frame.

3. A drive shield as claimed in claim 1 or claim 2, wherein the support means is constituted by skids along which said one support frame can slide or roll.

4. A drive shield as claimed in claim 3, wherein each skid is coupled to a respective one of the elongate members of the other knife shield.

5. A drive shield as claimed in claim 4, wherein each skid is pivotally coupled to a respective one of the elongate members of the other knife shield.

6. A drive shield as claimed in any one of claims 3 to 5, wherein there are two skids, one skid being located at each lateral edge of the drive shield.

7. A drive shield as claimed in any one of claims 3 to 6, wherein each skid is provided with a profiled guide rail which cooperates with correspondingly shaped guide elements provided on said one support frame.

8. A drive shield as claimed in claim 7, wherein each guide rail has a guide surface of part cylindrical configuration and each guide element has a correspondingly shaped concave guide surface.

9. A drive shield as claimed in claim 7 or claim 8 wherein each guide element is a shoe which, in use, slides along the corresponding guide rail.

10. A drive shield as claimed in claim 7 or claim 8, wherein each guide element is a roller which, in use, rolls along the corresponding guide rail.

11. A drive shield as claimed in any one of claims 1 to 10 wherein each elongate member of the first knife shield is pivotally connected to the aligned elongate member of the second knife shield.

12. A drive shield as claimed in any one of claims 1 to 11, wherein each elongate member is a steel plank.

13. A drive shield substantially as hereinbefore described with reference to, and as illustrated by, Figures 1 to 3, or Figures 1 and 2 as modified by Figure 4 of the accompanying drawings.

14. A drive shield for use in driving trenches, the drive shield being constituted by a plurality of elongate members mounted in a parallel, side-by-side relationship on a support frame, each of the elongate members being movable relative to the support frame, wherein at least part of the support frame is mounted on skids along which it can slide or roll in the direction of trench advance.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. trouble-free advance of the heavy frame structure is ensured. The profiled guide rails 29 are constituted by cylindrical half-pipes 29' (see Figure 3), in which case the rollers 30 are formed with a concave groove 32. This configuration helps to prevent fouling or blocking of the guides. Instead of rollers 30, sliding shoes 30' (see Figure 4) may constitute the guide elements. These shoes 30' may also be formed with concave grooves so as to mate with rails such as 29'. Alternatively, they may slide directly on the skids 28 (see Figure 4). WHAT WE CLAIM IS:

1. A drive shield for use in driving trenches, the drive shield being constituted by first and second knife shields positioned one behind the other, each knife shield having a plurality of elongate members mounted in a parallel side-by-side relationship on a respective support frame, each of the elongate members being movable relative to its support frame, and the two support frames being coupled together, wherein one of the support frames is mounted on support means relative to which it is movable in the direction of trench advance.