AU594078B2 - Improvements to trench digging apparatus - Google Patents

Description

~of V Form COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952-62 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE: Application Number: Lodged: Class Int. Class Ccqmplet e Specification Lodged: tell Accepted: Published: Priority, RolatGe6 Art: L This dument con tailis the ame~dmntsmade under ion 49 and is correct for printing.

Nanfieldf Appi'lcant: Add ress of Applicant: TO BE COMPLETED BY APPLICANT JOHN CURTIS BAYLISS 5 Piquet Hill Road, Te Awamutu, New Zealand I I 4 I C Actual Inventor- Address for Service: JOHN CURTIS BAYLISS Care of R.K. D4ADDERN AS~SOCIATES, 345 King Willdan Stf-reet, Adelaide, State of South Australia, Commonwealth of Australia

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Completf, Specification for the invention entitled: "IMPROVEMENTS TI0TRI1,qCH DIGGING APPARATUS" The following statement a full description of this invention, including the best method of performing it known to me.

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FQ 42~ 2M r4 This invention concerns apparatus for mounting digging implements such as trench diggers and rotary cutters for such diggers.

In my New Zealand Patent 206363, there is described a mounting arm for a trench cutter which is fixed to one side of a tractor. The trench cutter had an associated boom, one end of 0 which was pivoted between the tractor wheels, the opposite end of which carried a rotary trench cutter and a roller assembly which supported the weight of the rotary cutter and ran in the trench dug by the rotary cutter. The cutter might be mounted on the left of the tractor so that the tractor wheels could run on the road, while the rotary cutter dug in the verge, a trench parallel to the edge of the road. A counterweight was hung on the opposite side of the tractor.

Although this geometry improved the steerability and ease of use in that the operator could view the progress of the trencher from his cab by looking sideways, the full potential of the machine was still not being realised.

The position of the cutter at the ids of the machine is not necessary for achieving optimum speed and a more compact, manageable machine would result if the centre of gravity of the trencher attachment could be brought within the tractor wheels instead of lying to one side such that the centre of gravity lies perhaps 700 mm laterally from the tractor chassis.

The progress of the tractor is also influenced by the rate of cutting. If a rotatable cutter having a ring of buckets or scoops revolving around a hub is used, the leading edge of each scoop must perform most of the trenching work, absorb most torque and suffer most wear. Consequently only tractors with a power take-off rating of an adequate size were available for 33 this work Q 6' This invention aims primarily to reduce the 1pjver necessary for a given trenching rate and secondly to improve the handling of the tractor to which the tzrncher is attached.

According to one aspect of the invention, a rotary trenching head comprises an annular array of scoops each of which has a leading edge and a trailing edge wherein part of the leading edge which is distal from the axis of rotation is constituted by a cutter, the free end of which lies across the mouth of the scoop and is raked such that said free end encounters progressive resistance as it enters the ground.

According to another aspect of the invention, a rotary trenching.head comprises an annular array of scoops about a centre hub and rotatable about an axis of rotation thereth3ough, and wherein each of said scoops incorporates a leading and trailing edge, and wherein the section of each leading edge distal to the hub comprises an L-section cutter with one end free, and wherein said free end lies in a plane substantially tangential to a circle centred about said axis of rotation and which is also substantially parallel to the feed direction of said cutter, and wherein penetration of the ground is primarily effected by said 'cutter.

The cutter may be a blade, the free end of which is raked such that the angle of rake is from 5-25' from the horizontal. This causes the blade to encounter progressive resistance as it S;enters the ground. Preferably the cutter is of constant thickness and is free of any protrusion or tapers which might increase the force necessary for ground penetration. The cutter may be integral with the scoop hiut for replacement '1 S purposes it is preferable to supply the scoop with a bolt-on cutter.

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r jl- -7 2 Preferably the part of the scoop's leading edge which is furthest from the axis of rotation is relieved and the cutter is located so as to substitute the relieved part and restore the working arc of the scoop.

The cutters' leading edge may be sharpened. I have found that plane of the free' end of the cutters need not be exactly tangential to the said circle. It may be some 5-15° either side of tangential. Both the free end and the captive end of the cutter are suibject to considerable wear but the wear does not reduce the thickness of the metal substantially. A thickness of the order of 10mm is used for cutting shallow draina-e trenches to assist removal of surface water -rom roads with no kerb.

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r i $;i 1 /1 -3a- -i'i r -'1 llrrr- Another apparatus aspect comprises a trenching head as described above in combination with a tractor and a mounting means which positions the trenching head in advance of the tractor's front wheels.

11 A shallow trench perhaps 200mm deep and about 450mm wide can be cut at walking pace. The spoil is distributed over the surrounding vegetation thinly enough to be unnoticeable after a few weeks. Such a trench is cheap to excavate and provides satisfactory drainage where there is a road camber to direct surface water toward the trench. Road drainage is enhanced by making inclined feeder trenches from the road edge across the verge to the drainage trench.

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0:000: 2 Q 4 0 0 *r 0 01'2 :2Q Preferably, at least two passes are made over the verge with a trenching machine whose head rotates about an axis parallel to the road direction wherein one pass cuts a trench of shallow arcuate section alongside the road edge and another pass cuts a trench of shallow section in the verge which lies directly adjacent the road creating a gravity assisted path for run off into the trench furthest from the road edge.

One embodiment of the invention is now described with reference to the accompanying drawings in which:- Fig. 1 is a perspective view of a bucket with a cutter, I1.

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Fig. 2 is a side view of the bucket of Fig. i, Fig. 3 is a front view of the bucket of Fig. 1, Fig. 4 is a front view of the trenching head and part of the supporting arms, -4- 7: Fig. 5 is a diagrammatic plan of the trenching head fitted to one end of a tractor, Fig. 6 is a section through part of a road and the accompanying verge showing the size of trench cut by the head, and Fig. 7 is a section through the same road with the verge skimmed.

5 -a4 4, -4a-: t Si i 1 L- 0 The rotary trenching head is as described in my co-pending application no: 206363.

Referring firstly to figures 1 and 2 the head comprises a hub 2 from which six identical scoops 4 radidte The scoops are made of thick steel plate and bring the diameter of the trenching head to about 1500mm. The head is lowered, into the ground when rotating, while the the tractor on which the head is mounted feeds forward slowly in the direction indicated by arrow F. This brings edge 6 of the scoop which is parallel to the feed direction into contact with the ground. It also brings the side wall edge 8 of the scoop into ground contact. This area on each scoop would wear rapidly if it were not for the provision of blade 10. This blade is 10mm thick and 90mm deep. The blade is of L-section, the part 12 connected to the scoop by bolts 14 being 150mm long, the free end 16 of which is parallel to the scoop edge 6 being 90mm long. The face of the free end lies on a tangent to the circle described 0 o by the free end as it rotates about hub centre 18. In use the blade wears to produce a S bevel 20 along the entire leading edge 22.

0 00 I The initial resistance of the cutter is modified from being sudden to progressive by mounting the cutter with a rake which is best seen in figure 3. The rake shown here is *about 15 degrees but 10 degrees and 5 degrees also give useful results.

S Figure 4 shows the side mounting of the trenching head in its position in relation to the road 24 and verge 26, A quadrant section sheet metal guard 28 with flexible rubber flap extensions 30 is mounted on the housing 32 which is suspended from the boom 34 and arm 36. The housing carries a .Skid 38 which works as a depth stop.

In fig!'re 5 a frame 40 is fixed to the tractor chassis. Boom 34 and arm 36 are pivoted to the frame such that tho centre of the trenching head hub 2 lies close to the longitudinal mid axis of the tractor 42. The blades 10 are indicated as is the direction of tractor progress. If the head is mounted on a tractor with equal sized wheels then it makes little difference whether the head is mounted at the front or rear because the driver can select his direction with almost equal ease.

Figure 6 Msows the profile of the trench 44 in relation to the verge 26 and road 24.

While the verge may present in some conditions an obstacle to road drainage, -Ir 1 4 i( 1 7 additional parallel cuts 46, 48 of shallower depth produce the profiles seen in figure 7 where there is an unbroken gravity fed slope to the trench 44.

I have found the advantages of the above embodiment to be that a substantial reduction in the horsepower required to drive the scoops is possible. My best result is o 50 per cent reduction over scoops fitted with a threaded bolt housed partly in the bend of the cutter and projecting from the cutter in order to engage a bore provided in the side wall of the scoop.

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Claims (11)

1. "I A rotary trenching head for digging trenches comprising, an annular array of scoops about a centre hub and rotatable about an axis of rotation therethrough, and wherein each of said scoops incorporates a leading and trailing edge, and whereirn -he section of each leading edge distal to the hub comprises an 'L'-section cutter with one end free, and wherein said free end lies in a plane substantially tangential to a circle centred about said axis of rotation and which is also substantially parallel to the feed direction of said cutter, an.- wherein penetration of the ground is primarily effected by said cutter. .9 o 0 0 .o o 9 o 9 ae o 0 6 Oo e 0 9 a 9e o 9 09 9

2. A rotary trenching head as claimed in claim 1 wherein the cutter is a blade, the free end of which is raked such that the blade encounters progressive resistance as it enters the ground.

3. A rotary trenching head as claimed in claim 2 wherein the angle of rake is between 5-250 from a plane in which the axis of rotation lies.

4. A rotary head as claimed in any one of claims 1 to 3 wherein the part of the scoops leading edge which is distal from the axis of rotation is relieved and the cutter is located so as to substitute the relieved part and restore the working arc of the scoop. A rotary trenching head as claimed in any one of claims 2 to 5 wherein the plane of the free end of the cutter is from 0-150 either sid f tangential to the said circle. C-la., s 3- =o 5

6. A rotary trenching head as claimed in any one oft: receod.i;g c laima wherein the blade is of substantially constant thickness throughout.

7. A rotary trenching head as claimed in aiy one of the preceding claims wherein the ground-engaging edge of the cutter is sharpened. >1 -7- I I ii ih

8. A rotary trenching head comprising an annular array of scoops each of which has a leading edge and a trailing edge wherein part of the leading edge which is distal from the axis of rotation is constituted by a cutter, the free end of which lies across the mouth of the scoop and is raked such that t4h ede-ncjunters progressive resistance as it enters the ground.

9. A rotary trenching head substantially as herein described with reference to' and as illustrated in the accompanying drawings. 0 o" 0 0 0 go o a to 0 00 0 00 0 00 0 o 00 o 0 0 0 0 A rotary trenching head as claimed in any one of claims 1 to 9 in combination with a tractor and a mounting means which positions the trenching head in advance of the tractors front wheels.

11. A rotary trenching head as claimed in any one of claims 1 through 9 in combination with a tractor and a mounting means wherein the working position of the trenching head is such that wv.hei the centre of gravity thereof is projected onto a line along the axis of the tractor's wheels nearest to said head, the projection will be between said wheels.

12. A trenching head substantially as herein described with reference to and as illustrated in the accompanying drawings.

13. A combination of a tractor and a trenching head substantially as herein described with reference to and as illustrated in the accompanying drawings. Dated this 26th V day of September, 1989 JOHN CURTIS BAYLISS, By his Patent Attorneys, R.K. MADDERN ASSOCIATES. -8- I: I *i\ j ii 51