Trenching apparatus

Abstract: A trenching apparatus is provided having a base support which mounts a boom structure carrying a digger arm operative to form a trench alongside the base support along a trenching line. The base support includes a pair of longitudinally spaced sleeve members connected to a first track assembly which slidably receive a pair of longitudinally spaced slider members connected to a second, wider track assembly. An adjustment mechanism is provided to move the slider members, and, in turn, the second track assembly, laterally within the sleeve members between a retracted, transport position in which the first and second track assemblies are spaced relatively close to one another and readily fit upon a trailer commonly used to transport heavy equipment along roads and highways, and an extended, operating position in which the first and second track assemblies are relatively widely spaced from one another to provide the apparatus with acceptable stability during a trenching operation.

Description: This invention relates to apparatus for forming trenches, and, more particularly, to an apparatus for digging a longitudinally extending trench suitable for the formation of an inground retaining wall at an excavation site. The erection of above-ground structures, particularly in relatively sandy soil, often requires the formation of inground retaining walls for use as a load-bearing foundation or as a barrier to prevent the collapse of soil into the excavated area. Where such excavations are made adjacent an existing structure, the retaining wall along the excavation line adjacent the existing structure is necessary to resist soil pressures established beneath the adjoining structure. If no retaining wall is formed, the soil beneath the adjoining structure can collapse outwardly into the excavation and/or damage the existing structure. In addition to retention of soil, retaining walls of this type are often constructed to block the flow of ground water into the excavated area. A number of methods have been employed to form retaining walls around an excavation site or adjacent structures which adjoin such site. One method has been to employ piles formed of wood or steel which are driven along the excavation line to form the retaining wall. Alternatively, a roll of bored holes are formed along the excavation line which receive reinforced concrete piles to form the retaining wall. Both of these methods produce retaining walls which are not water-tight, and which may require substantial horizontal strengthening to maintain the desired alignment along the excavation line. Trenching apparatus such as disclosed in U.S. Patent No. 4,843,742 to Camelleri have been proposed as an alternative to the methods and apparatus of forming retaining walls mentioned above. In trenching apparatus of this type, a supporting base capable of being moved in a longitudinal direction along an excavation line carries an elongated trench digger arm supported on one side thereof by a boom structure. The support base is drivingly connected to skids or track assemblies of the type employed in conventional bulldozers which are effective to move the support base and digger arm along the trench line to form a trench of the desired depth. Concrete is poured into the trench immediately behind the moving trenching apparatus, into which appropriate reinforcing bars are inserted, so that an essentially continuously formed, reinforced concrete retaining wall is provided at the excavation site. One problem with trenching apparatus of the type described in Patent No. 4,843,742, particularly in trenching operations performed in sandy soils, involves cave-in of the trench as it is being formed. The boom structure mounted to the support base carries the heavy digger arm alongside the support base, thus creating a substantial force on the skid or track assembly located closest to the trench. It has been found that the pressure exerted by such track assembly can cause the adjacent soil to cave into the trench at the same time or immediately after the trench is dug. A second problem with trenching apparatus of the type disclosed in Patent No. 4,843,742 is instability during a trenching operation. Because the digger arm is heavy, unless the track assemblies mounted on opposite sides of the support base have substantial lateral spacing therebetween, the apparatus tends to tip over. The extent of lateral spacing between the track assemblies is limited, however, because the trenching apparatus must be narrow enough to load onto conventional trailers for transport on roads and highways. There has therefore been a need to provide a trenching apparatus having acceptable stability, but which can also be readily transported on commercially available trailers or other heavy equipment hauling devices. U.S. Patent 2410271 describes vehicles for carrying a trench excavator of the type comprising a main frame and, connected thereto by an extensible outrigger, an auxiliary frame, the frames being positionable either side of a channel being dug or cleaned. The main and auxiliary frames are carried on creeping traction mechanisms. The traction mechanism for the main frame is depicted as being wider than that for the auxiliary frame but there is no discussion of this. The Patent proposes that the outrigger include a frame which can be locked at various angular positions relative the telescopic beam thereof to thereby expand or contract the beam. U.S. Patent 3205961 describes a device for varying the width between transversely adjacent endless tracks of vehicles especially mobile working machines which in use are positioned either side of a trench. The device comprises a bearing box for both tracks sliding moveable in opposite directions relative an axle box in which they are located side by side but in separate chambers. The bearing boxes are moved by piston and cylinder devices provided therein. The tracks have equal widths. It is among the objectives of this invention to provide a trenching apparatus for digging a longitudinally extending trench along a trench line which substantially eliminates cave-in of the trench as it is being formed, which has acceptable stability during operation and which is readily transported over roads and highways using conventional heavy equipment trailers. Apparatus for digging a trench, in accordance with the invention, comprises a base support having opposed sides, a digger arm for digging a trench along a trench line, means for mounting the digger arm to the base support, a first track assembly and a second track assembly, the first track assembly having a greater width than the second track assembly, characterised in that the first track assembly is mounted on the side of the base support and located in use closest to the trench line to provide an expanded load bearing surface closest to the trench for the weight formed by the digger arm to prevent collapsing of soil into the trench, the second track assembly being mounted on the opposite side of the base support and both track assemblies in use being on the same side of the trench line. In a preferred embodiment, the trenching apparatus has a base support which mounts a boom structure carrying a digger arm operative to form a trench alongside the base support following a trenching line. The base support includes a pair of longitudinally spaced sleeve members connected to one crawler or track assembly, and a pair of longtudinally spaced slider members connected to a second crawler or track assembly. Each of the slider members is slidably received within a sleeve member to permit relative movement therebetween. An adjustment mechanism, such as one or more cylinders, is effective to move the slider members, and, in turn, the second track assembly, laterally within the sleeve members between a retracted, transport position and an extended, operating position. In the retracted, transport position, the first and second track assemblies are spaced relatively close to one another and readily fit upon a trailer commonly used to transport heavy equipment along roads and highways. In the extended, operating position, the first and second track assemblies are relatively widely spaced from one another providing the apparatus with acceptable stability to perform a trenching operation. In the presently preferred embodiment, each sleeve member of the support base comprises a rectangular-shaped frame connected at one end to the first track assembly and having an open second end. Preferably, wear plates formed of a low friction, wear resistant plastic or similar material line the interior of each sleeve member to reduce wear and facilitate movement of the slider members therein. Each slider member is formed in a correspondingly shaped rectangular configuration having one end attached to the second track assembly and an opposite end insertable through the open end of a sleeve member and into the interior thereof. In response to operation of the adjustment cylinders, the slider members and second track assembly connected thereto are moved inwardly and outwardly relative to the sleeve members to vary the lateral spacing between the first and second track assemblies from a retracted, transport distance of about 3.0 m (9.7 feet) to an extended, operating distance of about 3.8 m (12.5 feet). Each of the track assemblies are of the same type commonly employed in bulldozers and other types of heavy construction equipment. But the grouser plates forming the outermost, earth-engaging surface of the first track assembly are preferably about 50 cm (20 inches) in width, whereas the grouser plates forming the outermost surface of the second track assembly are preferably about 90 cm (36 inches) in width. The wider, second track assembly is located on the side of the support base closest to the trench, i.e., on the same side where the boom structure carries the digger arm. These wider grouser plates distribute the force exerted by the weight of the boom structure and digger arm over a comparatively large surface area thus reducing the pressure on the soil beneath. As a result, the problem of cave-in of soil immediately surrounding the trench being dug is substantially reduced. The invention will now be further described by way of example only with reference to the accompanying drawings in which:- Figure 1 is a schematic view of a trenching apparatus of this invention; and Fig. 2 is a schematic, cross sectional view taken generally along line 2-2 of Fig. 1. Referring now to the Figs., the apparatus 10 comprises a support base 12 which mounts a fixed hitch 14 connected to a pivotal hinge 16. An outer boom 18 is pivotally mounted to the hinge 16 by a bracket 20 and this outer boom 18 slidably receives an inner boom 22. One end of the inner boom 22 is connected to a boom extension cylinder 24 which mounts a digger arm manipulator head 26 having a bracket 28 carrying a digger arm 30. The digger arm 30 is operative to form a trench 31 in a manner such as disclosed in U.S. Patent No. 4,843,742 to Camelleri. A lift cylinder 32 is connected by a bracket 34 to the outer boom 18 and is effective to angularly raise and lower the outer boom 18, which, in turn, raises and lowers the digger arm 30. The foregoing construction of apparatus 10 forms no part of this invention of itself and is therefore discussed only briefly herein for purposes of defining the overall construction of apparatus 10. With reference to the bottom of Fig. 1 and Fig. 2, the support base 12 includes a pair of sleeve members 36 and 38. Each of the sleeve members 36, 38 are rectangular in shape having hollow interiors 40 and 42, respectively, lined with wear pads 44 preferably formed of any suitable low friction, wear resistant material such as Nylatron which is a registered trademark of The Polymer Company. The sleeve member 36 has an open end 46 which is adapted to receive a slider member 48. The slider member 48 is a rectangular-shaped member having an exterior dimension which is slightly less than the interior dimension of the sleeve member 36 including its wear plates 44. Similarly, a second slider member 50 is insertable through the open end 47 and into the interior 42 of sleeve member 38. The second slider member 50 has a rectangular-shaped, exterior surface having a slightly smaller dimension than the interior 42 of sleeve member 38 and the wear plates 44 therein. As shown in Fig. 2, the sleeve member 38 and slider member 50 are larger in width, i.e., from top to bottom as depicted in Fig. 2, than the sleeve member 36 and slider member 48, respectively. In the presently preferred embodiment, the sleeve members 36, 38 and slider members 48, 50 extend between a first track assembly 54 and a second track assembly 50. The first and second track assemblies 54, 52 are of the type conventionally utilized in excavation machinery such as bulldozers and the like, each including drive rollers and sprockets (not shown), and exterior, earth-contacting grouser plates 56 and 58, respectively. The details of the construction of track assemblies 52, 54 form no part of this invention and are not disclosed herein. For purposes of the present discussion, the second track assembly 52 carries a longitudinally extending beam 62 which fixedly mounts one end of each of the sleeve members 36 and 38 opposite their open ends 46 and 47, respectively. Similarly, the first track assembly 54 mounts a longitudinally extending beam 64 which fixedly mounts one end of each of the slider members 48, 50. As mentioned above, the opposite ends of such slider members 48, 50 are received within the sleeve members 36, 38, respectively. As viewed in the Figs., the width of the grouser plates 56 forming the outermost, earth-engaging surface of second track assembly 52 are preferably about 50 cm (20 inches) in width. The grouser plates 58 forming the outermost surface of first track assembly 54 are preferably about 90 cm (36 inches) in width. This difference in width is advantageous because the first track assembly 54 is located on the side of apparatus 10 along which the digger arm 30 is carried by booms 18, 22 to dig the trench 31. The weight of booms 18, 22, coupled with the weight of digger arm 30, create a moment or force about the support base 12 tending to tip the apparatus 10 in a clockwise direction as viewed in Fig. 1 which is only partially offset by counterweights (not shown) mounted adjacent track assembly 52. Additionally, substantial retraction forces can be generated in the clockwise direction in the course of pulling the digger arm 30 out of trench 31 if it becomes stuck or its motion restricted. In either instance, a substantial force is exerted on the first track assembly 54 which, in turn, exerts pressure on the ground beneath. The relatively wide grouser plates 58 of first track assembly 54 distributes this downward force or pressure over a wider area of the earth adjacent the trench 31 formed by the digger arm 30. This prevents or substantially reduces the problem of cave-in of the earth into the trench 31 as it is being formed by the digger arm 30. Additionally, the relatively wide first track assembly 54 enhances the stability of apparatus 10 in resisting a tendency of the apparatus 10 to tilt in a clockwise direction as viewed in Fig. 1. The stability of apparatus 10 is enhanced by the cooperating sleeve members 36, 38 and slider members 48, 50. In the presently preferred embodiment, a pair of longitudinally spaced, pneumatically or hydraulically operated cylinders 66 and 68 are connected between the beams 62 and 64 carried by the track assemblies 52 and 54 respectively. The cylinder housing 70 of each cylinder 66, 68 is mounted by a bracket 72 to the beam 62, and the cylinder rod 74 of each cylinder 66, 68 is mounted by a bracket 76 to the beam 64. These cylinder rods 74 are preferably enclosed in a protective cover or bellows 78 as schematically illustrated in Fig. 2. In response to operation of the cylinders 66, 68, the slider members 48, 50 are moved laterally within the sleeve members 36, 38, respectively. In turn, the first track assembly 54 is moved laterally relative to the second track assembly 52 between a retracted, transport position (not shown) and an extended, operating position. In the retracted, transport position, the slider members 48, 50 are substantially contained within the sleeve members 36, 38, thus moving the first track assembly 54 to a distance of about 3.0 m (9.7 feet) from the second track assembly 52. With the first and second track assemblies 54, 52 in this retracted, transport position, the apparatus 10 is easily loaded onto a trailer for transport along conventional roads and highways. In the extended, operating position, the slider members 48, 50 are moved outwardly from the sleeve members 36, 38 so that the lateral space between the first and second track assemblies 54, 52 is approximately 3.8 m (12.5 feet). In this extended position, the track assemblies 52, 54 provide good stability during operation of the apparatus 10 and resist tilting or pivoting in a clockwise direction under the weight of the booms 18, 22 and digger arm 30. Modifications may be made to the above-described preferred embodiment to adapt it for a particular situation or material. For example, the sleeve members 36, 38 and slider members 48, 50 have been illustrated with a rectangular cross-section but it should be understood that essentially any configuration could be utilized, e.g., round, square, hexagonal, etc., so long as sliding movement is permitted therebetween. Additionally, other actuators for moving the track assembly 54 relative to track assembly 52 can be used besides cylinders 66, 68 such as racks, cables, etc.

Claims: Apparatus (10) for digging a trench, comprising a base support (12) having opposed sides, a digger arm (30) for digging a trench (31) along a trench line, means (14, 16, 18, 20, 22, 24, 26, 28) for mounting the digger arm (30) to the base support (12), a first track assembly (54) and a second track assembly (52), the first track assembly (54) having a greater width than the second track assembly (52), characterised in that both track assemblies (52,54) in use are on the same side of the trench line, the first track assembly (54) being mounted on the side of the base support (12) located in use closest to the trench line to provide an expanded load bearing surface closest to the trench (31) formed by the digger arm (30) for the weight of the apparatus to prevent collapsing of soil into the trench (31) and the second track assembly (52) being mounted on the opposite side of the base support. Apparatus as claimed in Claim 1 further comprising adjustment means (36, 38, 48, 50, 66, 68) for adjusting the lateral spacing between the first and second track assemblies (54,52). Apparatus as claimed in Claim 2 wherein the adjustment means comprises at least one cylinder (66,68) connected between the first and second track assemblies (54,52) and operative to move the first track assembly (54) between an extended position and a retracted position relative to the second track assembly (52). Apparatus as claimed in any preceding Claim in which the base support (12) includes at least one sleeve member (36, 38) connected to the second track assembly (52) which has a hollow interior and at least one slider member (48, 50) connected to the first track assembly (54) and movable within the hollow interior of the sleeve member (36, 38). Apparatus as claimed in Claim 4 wherein a wear plate (44) is mounted on the hollow interior of the or each sleeve member (36, 38) and/or the exterior surface of the or each slider member (48, 50) to permit relative movement of the slider and sleeve members (36, 38, 48, 50). Apparatus as claimed in either Claim 4 or Claim 5 wherein two rectangular-shaped, longitudinally spaced sleeve members (36, 38) are provided, each of which has one end mounted to the second track assembly (52) and an opposite open end. Apparatus as claimed in Claim 6 wherein two rectangular-shaped, longitudinally spaced slider members (48, 50) are provided, each of which is mounted at one end to the first track assembly (54) and has an opposite end which is insertable through the open end of one of the sleeve members (36, 38). Apparatus as claimed in Claim 7 wherein at least one cylinder (66, 68) is connected between the track assemblies for moving the slider members (48, 50) along the sleeve members (36, 38) so that the first track assembly (54) moves between an extended position and a retracted position relative to the second track assembly (52). Apparatus as claimed in any preceding Claim wherein the first track assembly (54) is about 90 cm (36 inches) in width, and the second track assembly (52) is about 50 cm (20 inches) in width.

Inventors: HOLLOWAY RANDY J, MOORE BRUCE E, SHINN RONALD R, HOLLOWAY, RANDY J., MOORE, BRUCE E., SHINN, RONALD R.
Applicants: EAGLE PICHER IND INC, EAGLE-PICHER INDUSTRIES, INC.
Application year: 1992
Main classification: E02F9
IPC codes: E02F9, B62D55