GB2133436A - A boom type of trenching machine - Google Patents

Abstract

A boom type of trenching machine has a trenching boom 14 including an endless excavator chain 18 extending around a pair of sprockets 16 and 17, the boom 14 being mounted on a tractor 10 by means of a mechanism 15 including first and second arms 24 and 27. The arms are pivoted to a support 21 releasably secured to the tractor, and arm 24 is also pivoted to the boom 14. The arm 27 is connected to the boom by means of a sliding connection including a guide 33 of an empirically-determined profile. A tie bar 29 interconnects the two arms 24 and 27 and a ram 30 is arranged to effect movement thereof. The profile of the guide 33 is selected so that a required movement is imparted to the boom 14 on operation of the ram 30: for instance the lower end 35 of the boom may move substantially vertically from ground level downwards, and the boom as a whole may move forwardly and with a reducing angle to the horizontal from ground level upwards of the lower boom end 35. <IMAGE>

Description

SPECIFICATION A boom type of trenching machine This invention relates to a boom type trenching machine which includes a mechanism permitting the mounting of the machine on a vehicle such as a tractor. The invention further relates to the combination of such a trenching machine and a vehicle operatively carrying the trenching machine.

A boom type trenching machine is well known in the trenching art and comprises a boom having an excavating chain running around sprockets at or adjacent the ends of the boom, excavator blades being attached to the chain at spaced intervals and the chain being power-driven such that the blades may cut into the ground and raise spoil out of the trench being excavated, for depositing on the ground surface adjacent the trench. The boom typically is mounted on a vehicle by means of a mechanism which allows the boom to be raised clear of the ground, or lowered into the ground to a required depth during the initial stage of a trenching operation, whereafter the boom is maintained at that depth by the mechanism.

The mechanism connecting the boom to the vehicle must be capable of lifting the boom sufficiently clear of the ground to permit the transport of the trenching machine from place to place and yet also must permit the lower end of the boom to penetrate the ground to the required maximum trenching depth. In addition, the mechanism must be sufficiently strong to withstand the considerable strains which will be imparted thereto by the boom during a trenching operation.

There have been several proposals for mechanisms suitable for mounting the boom of a trenching machine to a vehicle which is to carry the machine, but in general these fall into three categories. In the first, a parallelogram-type of four-bar linkage is employed, in the second the boom is carried in guides provided on the vehicle and is arranged for linear sliding movement along the guides, at a constant angle relative to the ground; and in the third the boom is pivoted at its driven end coaxially at the drive shaft and is rotated about that shaft so that the lower end may be raised and lowered.The type of mechanism employed depends upon a variety of factors, including the scale of the trenching machine and hence the forces which are likely to be encountered, the type of vehicle which is to carry the machine, and in particular whether the vehicle is purpose-built or modified to carry the trenching machine.

Whichever type of mechanism is employed, a difficulty frequently arises when the back wall of a trench is to have a particular profile. For example in the case of a four-bar linkage mechanism, it may be difficult to give the back wall of the trench a specific profile. The vehicle may well have initially to be advanced and then retreated, until the boom has penetrated to the required depth, if for instance a trench with a vertical back wall is required. This problem may be overcome by a slide mechanism, but such an arrangement will suffer from the disadvantage discussed immediately beiow.

A further disadvantage of the above-described known mounting mechanisms is that when the boom is raised clear of the ground, it may project vertically to a great extent. As a result, it may be necessary to modify the mechanism so as to incorporate a further action, which serves to pivot the raised boom as a whole, thereby to lower the upper end thereof, to an acceptable height. The provision of a second action in the mechanism adds to the complexity and the cost of that mechanism, and moreover is likely to reduce its strength and reliability.Yet another disadvantage of the known mechanism, especially when used to mount a trenching machine a vehicle such as an agricultural tractor, is that when the boom is raised fully for transport of the machine the centre of gravity of the combined vehicle and trenching machine may be both relatively high and towards the rear of the vehicle to such an extent that the permissible speed of the vehicle over the ground must severely be limited for safety.

It is a principal object of this invention to provide a boom type of trenching machine having a mechanism suitable for mounting the machine on a vehicle, which mechanism allows the back wall of a trench excavated thereby to have a predetermined profile without the need to move the vehicle during the initial stage of trenching as the boom penetrates the ground. A further object is to provide a mounting mechanism for such a machine which is relatively simple to construct and permit mounting on the vehicle and which also may be configured to allow the trenching boom to be raised to such a disposition that the vehicle may travel safely at a relatively high speed.

Accordingly, this invention provides a boom type trenching machine having a mechanism arranged to permit the mounting of the machine on a vehicle, which mechanism comprises a first arm adapted for pivotal mounting about a first axis provided on the vehicle or on a support attached thereto, the first arm also being pivotally connected to the trenching boom, a second arm adapted for pivotal mounting about a second axis provided on the vehicle or on the support at a predetermined position relative to said first axis, the second arm being coupled to the boom by means of a sliding connection including guide means associated with the boom and defining a guide path of a pre-determined configuration, the sliding connection also including a slide member provided on the second arm and constrained by the guide means for movement along the guide path, the mounting mechanism further comprising a tie bar pivoted to both the first and second arms at points spaced from the first and second axes respectively, and lift means arranged to cause pivoting movement of the first and second arms about the first and second axes respectively whereby operation of the lift means causes the free end of the boom to be raised or lowered whilst describing a locus of pre-determined profile defined by the configuration of the first and second arms and axes, the tie bar and the sliding connection.

When the trenching machine is mounted on a vehicle by means of the mechanism defined above, by the pivotal connection of the first and second arms to the vehicle or to the support mounted thereon, the locus defined by the free (lower) end of the boom on operation of the lift means is a complex function of the precise configuration of the overall mounting mechanism, but of prime importance is the shape of the guide path. The shape of this path may be determined empirically after deciding upon the relative positions of the first and second axes, the shape and length of the first and second arms as well as the length and positioning of the tie bar, and so on, such that the free end of the boom describes the required locus.For example, once the abovementioned factors have been set, then the shape of the guide path may be determined to ensure that over a certain range of movement of the boom, the free end describes a substantially linear locus.

Moreover, appropriate selection of the various parameters will permit the linear locus to be substantially vertical, presuming that the vehicle is resting on horizontal ground.

The range of movement of the boom over which the pre-determined locus of the free end is achieved typically will be from ground level down to the maximum required trenching depth.

However, it is greatly preferred for the guide path to be configured so that when the lower end of the boom is raised from ground level upwards, the boom as a whole is moved forwardly and is also caused to lie at a lesser angle to the horizontal than when the boom is within a trench. Such an action will serve to move forwardly the centre of gravity of the trenching machine with respect to the vehicle on which it is mounted, and this in turn will permit the safer transport of the trenching machine from place to place.

It is greatly preferred for the mounting mechanism to include a support which provides the first and second axes to which the first and second arms are pivotally connected, the support being adapted for mounting on the vehicle which is to carry the trenching machine of this invention.

In this way, the relative position of the first and second axes may accurately be defined, so as to give the mechanism the required operating characteristics. Advantageously, there is provided means for mounting the support on a vehicle which means permits the pivoting of the support about a horizontal axis parallel to or coincident with the centre line of the vehicle when mounted thereon, such that the boom may at all times be maintained substantially vertical, notwithstanding the possibility of the vehicle standing on uneven or sloping ground. Such mounting means may include hydraulic rams adapted for appropriate interconnection between the vehicle and the support, to effect and control the pivoting action of the support about said horizontal axis.

In the preferred configuration of this invention, there is provided a pair of first arms held in a spaced-apart disposition and a pair of second arms similarly disposed, each of the pair of first arms being journalled about said first axis and each of the pair of second arms being journalled about said second axis. Similarly, a pair of tie bars should be provided respectively for each pair of the first and second arms. With such a configuration, the boom of the trenching machine preferably is mounted between the pairs of first and second arms in such a way as to impart adequate torsional rigidity to the entire trenching machine, including its mounting mechanism.

The lift means conveniently comprises a double acting hydraulic ram, disposed to operate between the or each first arm and a fixed part of the vehicle or the support carrying the trenching machine.

For the preferred trenching machine of this invention, there is provided a cross-flow conveyor mounted on the support and adapted to transfer spoil discharged from the chain of the trenching machine boom to one side of the vehicle carrying the trenching machine, whereby said spoil is deposited on the ground to one side of the other of the trench being excavated. Conveniently, all of the power-driven facilities provided on the trenching machine are hydraulically actuated, means being provided to connect such facilities to a control arrangement and pressurised fluid source provided as a part of the vehicle to which the trenching machine is to be connected.

This invention extends to the combination of a vehicle and a trenching machine of this invention as defined above.

By way of example only, one specific embodiment of this invention will now be described in detail, reference being made to accompanying diagrammatic drawings, in which: Figure 1 is a side view of a trenching machine constructed in accordance with this invention and mounted on a tractor, with the boom of the trenching machine in a lowered position; Figure 2 is also a side view of the trenching machine illustrated in Figure 1, but with the boom in a raised position; and Figure 3 iliustrates in plan the configuration of the mounting mechanism of the trenching machine.

Illustrated in outline only at 10 in Figure 1 is a four-wheel drive tractor including front driven ground wheels 11 and rear driven ground wheels 12. Mounted at the rear of the tractor 10 is a boom type of trenching machine 13, including a boom 14 and a mechanism 1 5 serving to mount the boom 14 on the tractor 10 in such a way that the boom may be raised and lowered between the positions illustrated in Figures 1 and 2.

Rotatably mounted on the boom 14 adjacent the two ends thereof are sprockets 1 6 and 17.

around which extends an excavator chain 18 carrying cutting blades 19, as diagrammatically illustrated in Figure 1. An hydraulic motor 20 is arranged adjacent the sprocket 1 6 to effect rotation thereof in a clockwise sense, whereby the chain 18 is caused to run around the sprockets so that the cutting blades 1 9 may effect excavation of the ground to cut a trench, when the boom 14 is lowered into the ground. Spoil excavated by the cutting blades 1 9 is lifted by the blades and then thrown off them as the blades commence to move around the sprocket 16, the spoil landing on a conveyor 20 mounted on the rear of the tractor 10 to extend transversely thereof. The conveyor serves to deposit the spoil to one side, but in front, of the trench being excavated.The conveyor 20 is appropriateiy mounted on the tractor 10 such that the conveyor may be extended to one side or the other of the tractor, or disposed centrally when no trenching is taking place. An appropriate drive arrangement (not shown) is provided for the conveyor 20, and similarly a control arrangement and fluid supply lines (also not shown) are provided for the hydraulic motor 20.

All of the components thus far described, with the exception of the mechanism 1 5, are known per sue in the trenching machine art, and will not therefore be described in any greater detail here, for they form no part of this invention. The invention is however concerned with the raising and lowering mechanism 15, which will now be described.

Mounted on the rear of the tractor 10 is a support member 21, carrying first and second shafts 22 and 23 at pre-determined spaced-apart locations. The support member 21 is mounted on the tractor in such a way that the member may be turned about a horizontal axis parallel to a longitudinal centre-line of the tractor 10, appropriate means - for example, hydraulic rams (not shown) - being provided to control and effect such turning movement about said horizontal axis. Thus, should the tractor 10 be standing on uneven ground or transversely across a slope, the boom 14 may be caused to lie in an essentially vertical plane.

Journalled on the first shaft 22 is a pair of spaced-apart first arms 24 (only one of which arms is visible in Figures 1 and 2), the two first arms 24 being rigidily interconnected by means of a torque tube 25 extending therebetween, partway between the ends of the arms. The boom 14 is provided at its upper end with a pair of brackets 26, to each of which is respectively pivoted the end of a first arm 24 remote from its connection to the first shaft 22.

A pair of spaced apart second arms 27 (again, only one of which arms is visible in Figures 1 and 2) is journalled on the second shaft 23, the second arms 27 being coupled to the boom 14 at their ends remote from the second shaft 23 by means of respective sliding connections 28, to be described in greater detail below. The first and second arms 24 and 27 are linked together by means of a pair of the bars 29 pivoted respectively at their one ends to lugs 30 attached to the first arms 24 and at their other ends of the second arms 27, adjacent the sliding connections 28.A double acting hydraulic ram 30 has the free end of its piston rod connected to a shaft 31 extending between the first arms 24, the cylinder 30 of the ram being mounted on the support member 21 such that expansion and contraction of the ram 30 causes the first arms 24 to pivot between the positions shown in Figures 1 and 2 respectively.

The ram 30 is provided with an appropriate control arrangement and hydraulic feed pipes (not shown) in a manner well known in the art.

Each sliding connection 28 (that is, one for each second arm 27) comprises a peg 32 projecting laterally of the end of the associated second arm 27 and carrying a rotatable roller (not shown) which is snug fit in an elongate profiled cam slot 33 cut in a plate 34 attached to or forming a part of the boom 14. The cam slot 33 has a pre-determined profile such that the free, lower end 35 of the boom 14 describes a predefined locus, on operation, of the mechanism 1 5 by expansion or contraction of the hydraulic ram 30.

In the example of this invention described with reference to the drawings, the mechanism 1 5 and in particular the profile of the cam slot 33 are configured such that the lower end 35 of the boom 14 describes a substantially linear and vertical locus on movement of the lower end 35 from a position where that end touches the ground down to the maximum trenching depth, which may typically be of the order of two metres.

However, on raising the boom further from a position where the lower end 35 is at ground level, the profile of the cam slot 33 is such that the boom is moved forwardly and caused to lie at a lesser angle to the horizontal, whereby when the boom is fully raised (as illustrated in Figure 2), the centre of gravity of the entire tractor and trenching machine combination is moved forwardly, nearer rear wheels 1 2 of the tractor.

The profile of the cam slot 33 is best determined empirically after certain other factors and parameters have been decided. For example, the positioning of the shafts 22 and 23 on the support member 21 is defined largeiy by the tractor 10 itself, for the support must lie between the rear wheels 12 of the tractor though the shafts 22 and 23 should be outside the periphery of those wheels 12, which wheels may in any event be provided with a suspension arrangement such that the wheels may move relative to the tractor chassis. Moreover, the wheels illustrated may be replaced by wheels of a different diameter.

Consideration must also be given to the possible turning action of the support member 21 about a horizontal axis, as described above, to ensure that the boom 14 may be maintained vertical notwithstanding the location of the tractor on a slope. The configuration of the first and second arms must take into account the loads to which the mechanism 1 5 will be subjected, both when the trenching machine is in operation and also to such accidental loads as may be encountered should for instance the lower end 35 of the boom 14 strike a solid object when the boom is raised fully and the tractor 10 is being manoeuvred. In addition, the first and second arms 24 and 27 as well as the tie bars 29 must be clear of the excavating chain 18, the drive arrangement therefor and the spoil discharge path from the chain 18.It is furthermore important that the trenching action itseif takes place as close as possible to the tractor 10, to minimise the loads on the tractor and that the overall centre of gravity of the tractor and trenching machine combination should be as far forward as possible specially when the boom is raised fully, in order to allow both safe operation of the trenching machine and the safe movement, possibly at relatively high speeds, of the tractor when carrying the trenching machine.

When all of the foregoing factors and parameters have been decided upon, then the profile of the cam slot 33 may be determined empirically, primarily to ensure that the back wall 36 of the trench being excavated by the trenching machine has the required shape. Though in the example described, the back wall has a substantially vertical and linear shape, it will of course be appreciated that the mechanism 1 5 may be configured differently, for example to give a linear back wall lying at some angle to the vertical.

Claims (13)

1. A boom type of trenching machine having a mechanism arranged to permit the mounting of the machine on a vehicle, which mechanism comprises a first arm adapted for pivotal mounting about a first axis provided on the vehicle or on a support attached thereto, the first arm also being pivotally connected to the trenching boom, a second arm adapted for pivotal mounting about a second axis provided on the vehicle or on the support at a predetermined position relative to said first axis and substantially parallel thereto, the second arm being coupled to the boom by means of a sliding connection including guide means associated with the boom and defining a guide path of a pre-detemrined configuration, the sliding connection also including a slide member provided on the second arm and constrained by the guide means for movement along the guide path, and the mounting mechanism further comprising a tie bar pivoted to both the first and second arms at points spaced from the first and second axes respectively, and lift means arranged to cause pivoting movement of the first and second arms about the first and second axes respectively whereby operation of the lift means causes the lower end of the boom to be raised or lowered whilst described a locus of pre-determined profile defined by the configuration of the first and second arms and axes, the tie bar and the sliding connection.

2. A boom type of trenching machine according to claim 1 , wherein the configuration of the guide path is selected so as to cause the lower end of the boom to describe a substantially linear locus over a range of movement thereof.

3. A boom type of trenching machine according to claim 1 or claim 2, wherein the configuration of the gudie path is selected such that the boom moves forwardly relative to the vehicle to which the machine is attached and also moves to reduce the included angle between the ground and the boom for movement of the lower end of the boom from ground level upwards.

4. A boom type of trenching machine according to any one of claims 1 to 3, wherein the configuration of the guide path is selected so that the lower end of the boom moves substantially vertically as the lower end is moved from ground level downwards.

5. A boom type of trenching machine according to any of the preceding claims, wherein there is provided a support which defines the first and second axes about which the first and second arms are respectively pivotally mounted, the support being adapted for releasable mounting on the vehicle which is to carry the trenching machine.

6. A boom type of trenching machine according to claim 5, wherein the support includes mounting means permitting the mounting of the support on a vehicle which mounting means is arranged to allow pivoting of the support about a horizontal axis parallel to or coincident with the centre line of the vehicle when mounted thereon.

7. A boom type of trenching machine according to claim 6, wherein the mounting means includes a hyraulic ram adapted for interconnection between the vehicle and the support, to effect and control the pivoting action of the support about said horizontal axis.

8. A boom type of trenching machine according to any of the preceding claims, wherein there is provided a pair of first arms held in a spaced-apart disposition and a pair of second arms also held in a spaced-apart disposition, each of the pair of first arms being journalled about said first axis and each of the pair of second arms being journalled about said second axis, and there is further provided a pair of tie bars, associated one with a first arm and a second arm respectively.

9. A boom type of trenching machine according to claim 8, wherein the trenching boom is mounted between the pairs of first and second arms.

10. A boom type of trenching machine according to any of the preceding claims, wherein the lift means comprises a double acting hydraulic ram, disposed to operate between the or each first arm and a fixed part of the vehicle or the support carrying the trenching machine.

11. A boom type of trenching machine according to any of the preceding claims, and in which there is provided a support for mounting on a vehicle, therebeing a cross-flow conveyor arranged on the support and adapted to transfer spoil discharged from the chain of the trenching machine boom to one side of the vehicle carrying the trenching machine.

12. A boom type of trenching machine according to claim 1 and substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

13. The combination of a boom type of trenching machine according to any of the preceding claims and a vehicle upon which the trenching machine is releasably mounted by means of the mounting mechanism.