GB2088930A

GB2088930A - Trenching Machine

Info

Publication number: GB2088930A
Application number: GB8129684A
Authority: GB
Original assignee: JI Case Co
Current assignee: Case LLC
Priority date: 1980-12-08
Filing date: 1981-10-01
Publication date: 1982-06-16
Also published as: DE3141247A1; JPS57108333A; FR2495660A1

Abstract

The invention relates to a trenching machine in which an endless conveyor type digging assembly is operable to dig a trench. According to the invention, the digging assembly comprises an adjustable parallelogram frame for enabling the operator to maintain a constant digging angle at variable digging depths. One corner of the frame is pivotally connected at (14) to a tractor (10), and a powered digging chain (18) is entrained around its periphery. An hydraulic cylinder (32) is connected between sections (22, 24) of the frame (12) for adjusting the orientation of the parallelogram sections (20, 22, 24, 26). With the digging angle of the frame (12) maintained substantially constant, the digging depth can be increased by collapsing the parallelogram frame (12) with the cylinder (32) and lowering the digging end of the frame (12). After the parallelogram frame (12) is initially positioned into the ground at the desired digging angle, the vertical and horizontal forces generated by the digging end and side sections tend to hold the frame at the desired digging angle, regardless of the ground contour encountered. A control device (38, 40) may also be provided for controlling extension and retraction of the hydraulic cylinder (32) when it is desired that the bottom of the trench (36) remains on a substantially straight line. <IMAGE>

Description

SPECIFICATION Trenching Machine The present invention relates to a trenching machine, and more particularly, to an endless conveyor type digging assembly having an adjustable polygonal frame for variable digging depths.

Trenchers are known which have a rearwardly projecting digging boom which is connected to a tractor for pivotal movement. The digging boom is pivotally mounted to the tractor in a cantilevered fashion above an auger which disperses the spoil which is dug during the trenching operation to the sides of the trench. A crumber can be attached to the digging boom for cleaning the bottom of the trench during the digging operation.

A problem with such known trenchers relates to the ability of the operator to maintain the digging boom at a constant digging angle.

Experience has shown that a digging angle of about 600 relative to horizontal is preferred for trenching operations. With trenching machines having relatively straight line digging booms, it is very difficult for the operator to judge whether the digging boom is at or near the preferred 600 digging angle because the boom is in the trench and the operator cannot judge the attitude of the boom. Thus, there is a need for a machine equipped with means to assist the operator in keeping the digging boom at the desired digging angle.

Another problem associated with known trenchers is that the pivotal digging boom is of fixed length which limits variable digging depths.

When digging a trench for a drainage type line, for example, it is normally desired that the bottom of the trench remains substantially on a straight line that may be slightly inclined to a horizontal reference plane. If the trencher is traversing a hilly terrain while digging a drainage type trench the bottom of the trench may become wavy, either because the operator cannot accurately judge the digging depth required to maintain a straight line trench bottom or because the fixed length digging boom is not able to reach the depths necessary to maintain the straight line trench bottom. Thus, there is also a need for an adjustable digging boom frame which permits varying digging depths and an associated means for controlling the digging depth when traversing uneven terrain.

The primary aim of the present invention is the provision of a trenching machine which enables the operator to maintain a constant digging angle at variable digging depths. To this end, a trenching machine according to the invention comprises a rearwardly projecting digging boom frame in the form of a collapsible parallelogram, one corner of which is pivotally connected to a tractor; and means for driving a digging chain mounted on said boom frame around the periphery of said parallelogram; the digging boom frame being movable into an operative position for digging a trench with adjacent sections of the parallelogram adjacent the bottom and a side of a said trench, and including an hydraulic piston cylinder mechanism for adjusting the orientation of the parallelogram sections to alter the digging depth while maintaining the digging angle of the frame.The hydraulic cylinder enables the operator to raise and lower the digging depth from the operator's seat. The frame will normally include a pair of equal length opposed digging and nondigging end sections and a pair of equal length opposed digging and non-digging side sections, with the end and side sections pivotally interconnected at their extremities to form a collapsible parallelogram. Alternatively, one pair of opposed side sections might be pivotally interconnected by links located inwardly from the extremities of the opposed side sections to define the parallelogram.

In the preferred embodiment, the hydraulic cylinder is connected between one of the side sections and an end section such that when the cylinder is fully extended, the lesser included angles of the parallelogram equal 600, the preferred digging angle. If the trencher is moving over even terrain and the hydraulic cylinder is fully extended, the digging side of the frame may be positioned at the desired 600 digging angle by lowering the digging frame into the ground until the non-digging end of the frame is observed by the operator to be parallel to the ground surface.

Under these conditions, the included angle between the digging side of the frame and the digging end of the frame equals 1200, and the digging end of the frame is parallel to the ground surface at the bottom of the trench. Thus, the present construction permits the operator to maintain the desired digging angle by visually observing and holding the non-digging end of the frame parallel to the ground surface when the machine is traversing relatively even terrain.

An advantage of the present construction, is that after the digging bottom is set into the ground at the desired digging angle, it tends to remain at that digging angle even though uneven terrain is subsequently encountered. This desirable feature results because the digging side and digging end of the parallelogram frame generate counteracting vertical and horizontal force components whereas conventional straight line digging booms only generate vertical or turning force components. The turning forces generated by the digging side of the frame are counterbalanced by the forces generated by the digging end of the frame, thereby holding the frame in place after it is initially set at the desired digging angle.Thus, the digging boom tends to remain at the desired digging angle after being positioned there, regardless of the evenness or unevenness of the terrain over which the machine moves.

When it is desired to increase the digging depth over even or uneven terrain, the hydraulic cylinder is retracted which collapses the parallelogram frame such that the included angle between the digging side of the frame and digging end of the frame is increased. This procedure is particularly useful when the terrain is uneven, and it is desired that the bottom of the trench remain substantially on a straight line.

Thus, the present construction enables the operator to raise and lower the digging depth by selectively extending or retracting the hydraulic cylinder. Further, it is not necessary to lengthen or shorten the digging chain for obtaining varying digging depths.

The present invention also mitigates the need for a crumber which is normally attached to the digging boom for cleaning the bottom of the trench during the digging operation. The digging end of the parallelogram frame performs the cleaning function normally performed by the crumber.

Preferred embodiments of the invention also include a control device such as a laser receiver unit which may be used in combination with a fixed transmitter to control the digging of a drainage type trench through uneven terrain where it is desired that the bottom of the trench remain on a substantially straight line. Laser and other similar control systems have been used in connection with devices such as road paving and grading machines for maintaining a substantially level surface. Such devices are adaptable to control the hydraulic cylinder in a machine according to the present invention for extending and retracting the cylinder as necessary to maintain a relatively straight line trench bottom.

One such arrangement for controlling the hydraulic cylinder includes a laser beam transmitter mounted on an adjustable tripod or the like at the end of a trench line. An adjustable receiving unit is mounted to a frame on the tractor that pivotally supports the parallelogram digging boom for receiving a transmitted laser beam. As the trenching machine moves along the trench line, the laser beam impinges on the receiving unit at different vertical locations depending upon the contour of the terrain over which the machine moves. The hydraulic cylinder is extended or retracted to either expand or collapse the digging frame in response to a corresponding signal from the receiving unit to thereby maintain the trench bottom substantially on a straight line.

The invention will now be described by way of example and with reference to the accompanying drawings wherein: Figure 1 is a side elevational view of an earthworking machine embodying the present invention.

Figure 2 is a side elevational view of the machine of Figure 1 with a control device therefor, illustrating the maintenance of a preferred digging angle at variable digging depths.

Figure 3 is a side elevational view of an earthworking machine embodying an alternative embodiment of the invention.

A trencher having the adjustable digging boom according to the present invention is illustrated in Figures 1-3. The tractor 10 includes a rearwardly projecting adjustable polygonal digging frame 12 which is pivotally attached at one of its corners by pin 14 to tractor frame 1 6.

The digging boom frame 12 is in the form of a parallelogram with an endless conveyor type digging chain 1 8 entrained around its periphery.

Digging frame 12, in a preferred embodiment as illustrated in Figure 1 includes a pair of equal length opposed digging and non-digging end sections 20, 22 and a pair of equal length opposed digging and non-digging side sections 24, 26. The end and side sections 20-26 are pivotally interconnected at their extremities by pins 14 and 28 to form a collapsible parallelogram. Pulleys 30 are attached to the corners of frame 12 for permitting chain 1 8 to be rotatably driven around the frame periphery. A conventional drive and lifting mechanism (not shown) is mounted within frame 1 6 for lifting and lowering frame 12 and for driving endless digging chain 18.

Referring to Figures 1 and 2, a hydraulic cylinder 32 is connected between one of the side sections 24 and an end section 22 for enabling the operator to raise and lower the digging depth of the frame from the operator's seat. When cylinder 32 is fully extended, as in Figure 1 , the lesser included angles of the parallelogram frame 12 equal 600, the preferred digging angle. If the trencher is moving over even terrain and cylinder 32 is fully extended, the digging side 24 of frame 12 may be positioned at the desired 600 digging angle by lowering frame 12 into the ground until the operator visually observes that the nondigging end 22 of frame 12 is parallel to ground surface 34.Under these conditions, the digging end 20 of frame 12 is also parallel to ground surface 34 at trench bottom 36, and the included angle between the digging side 24 and digging end 20 of frame 12 equals 1200.

Thus the present construction provides a means by which the operator can readily set the digging frame 12 at the desired digging angle of 600 when trenching over relatively even terrain.

The desired digging angle is maintained by the operator visually observing and holding the nondigging end 22 of frame 12 parallel to the ground surface 34 which necessarily means that the digging side 24 of the frame is positioned at the desired digging angle.

An advantage of the present construction is that after the digging boom 12 is set into the ground at the desired digging angle, it tends to remain at that digging angle even though uneven terrain is subsequently encountered. This feature results because the digging side 24 and digging end 20 of frame 12 generate counteracting vertical and horizontal force components during digging. The turning forces generated by the digging side 24 of the frame are counterbalanced by the forces generated by the digging end 20 of the frame thereby holding the frame in place after it is initially set at the desired digging angle. Thus, the digging boom 12 tends to remain at the desired digging angle after being positioned there, regardless of the evenness or unevenness of the terrain over which the machine moves.

When it is desired to increase the digging depth over even or uneven terrain, the hydraulic cylinder 32 is retracted which collapses the parallelogram frame 12 such that the included angle between the digging side 24 and digging end 20 exceeds 1200, as illustrated in Figure 2.

This procedure is particularly useful when the terrain is uneven, and it is desired that the bottom of the trench remain on substantially a straight line. Thus, the present construction enables the operator to raise and lower the digging depth by selectively extending or retracting hydraulic cylinder 32. Further, it is not necessary to lengthen or shorten the digging chain for obtaining varying digging depths.

The construction illustrated also eliminates the need for a crumber which is normally attached to the digging boom for cleaning the bottom 36 of the trench during the digging operation. The digging end 20 of the parallelogram frame 12 performs the cleaning function normally performed by the crumber.

A control device is shown in Figure 2 which may be used to control the digging of a drainage type trench through uneven terrain where it is desired that the bottom of the trench remain on a substantially straight line. Laser and other similar control systems have been used in connection with devices such as road paving and grading machines for maintaining a substantially level surface. Such devices are adaptable to control the hydraulic cylinder 32 which is connected to the parallelogram digging frame 12 of the present invention for extending and retracting cylinder 32 as necessary to maintain.a relatively straight line trench bottom.

The arrangement illustrated for controlling hydraulic cylinder 32 includes a laser beam transmitter 38 mounted on an adjustable tripod or the like at the end of a trench line. An adjustable receiving unit 40 is mounted to frame 16 for receiving a transmitted laser beam 42. The AccuSweep Model 721 automatic laser system manufactured by CLS Industries, Inc., is an example of one control device that is adaptable to control hydraulic cylinder 32 in the manner described herein. As the trenching machine moves along the trench line, laser beam 42 impinges on receiving unit 40 at different vertical locations depending upon the contour of the terrain over which the machine moves.The hydraulic cylinder 32 is extended or retracted to either expand or collapse digging frame 1 2 in response to a corresponding signal from receiving unit 40 to thereby maintain the trench bottom 36 substantially on a straight line.

An alternative form of the parallelogram digging frame 12 is illustrated in Figure 3. In this embodiment, the opposed digging and nondigging side sections 24, 26 are pivotally interconnected by links 46 which are connected to the side sections at a location inward from the extremities of the side sections. The hydraulic cylinder 32 is connected between the side sections for enabling the operator to raise and lower the digging depth from the operator's seat, as in the first embodiment illustrated in Figure 1.

The operation and advantages of the parallelogram digging boom illustrated in Figure 3 are the same as those for the digging boom illustrated in Figures 1 to 2.

Claims

1. A trenching machine comprising a rearwardly projecting digging boom frame in the form of a collapsible parallelogram, one corner of which is pivotally connected to a tractor; and means for driving a digging chain mounted on said boom frame around the periphery of said parallelogram; the digging boom frame being movable into an operative position for digging a trench with adjacent sections of the parallelogram adjacent the bottom and a side of a said trench, and including an hydraulic piston-cylinder mechanism for adjusting the orientation of the parallelogram sections to alter the digging depth while maintaining the digging angle of the frame.

2. A trenching machine according to Claim 1, wherein the piston-cylinder mechanism is coupled to the frame such that when it is fully extended, the lesser included angles of the parallelogram equal 600, the frame being mounted on the tractor with a longer side of the parallelogram extending below the contiguous shorter side adjacent said pivotal connection.

3. A trenching machine according to Claim 1 or Claim 2 including means for controlling the piston-cylinder mechanism to maintain a relatively straight line trench bottom.

4. A trenching machine according to Claim 3, wherein the controlling means comprises a laser beam receiving unit mounted on the tractor for receiving a laser beam from a fixed transmitter, the operation of the piston-cylinder mechanism being coupled to the receiving unit.

5. A trenching machine substantially as described herein with reference to Figures 1 and 2, or Figure 3 of the accompanying drawings.