GB2282950A - Hydraulic boom apparatus - Google Patents

Abstract

In hydraulic boom apparatus, such as a, flail trimmer a hydraulically-operated articulated boom arm 12, 15 has a trimming or cutting working head 13 attached to one end, the arm being pivotably connected at its other end between parallel wing extensions of the hydraulic fluid reservoir 2. The fluid circulates within the wings as well as within the main body of the reservoir, thereby being more effectively cooled. <IMAGE>

Description

FLAIL TRIMMER The present invention relates to flail trimmers of the type having a hydraulically-powered flail-type trimming or cutting working head attached to a boom arm assembly, the flail trimmer being generally fitted, in use, to the three point linkage of a tractor.

The invention will be described with particular reference to flail trimmers but is not intended to be strictly limited thereto, as the invention may have equal utility in other agricultural or construction equipment which use hydraulically-powered apparatus carried on boom arm assemblies.

Flail trimmers in general have a hydraulically operated boom arm as well as a hydraulically-powered working head. The hydraulic hoses for operating the working head and elements of the boom arm may be carried either on the outside or inside of the boom arm itself. The articulation of the boom arm allows the working head to adopt a range of operating positions the need for which arises from ' the variety of uses which the flail trimmers are required to perform, such as cutting hedgerows or steep grass verges. Thus, boom arms are usually required to have a long extended reach and yet should be compact when folded for transportation, for stability of the tractor and, in particular, for passage along narrow or winding roads. These requirements are difficult to reconcile, in terms of the geometry of the boom elements, and additional problems can arise from the hydraulic hoses which, when carried externally of the boom arm, may in certain boom configurations form depending loops which tend in use to become snagged on branches and the like, or become damaged by being pinched at an articulated joint.

Further problems arise with the hydraulic operating system itself, which tends to overheat due to the heat generated as a result of the high flow rate and high pressure applied to the hydraulic fluid. Heating of the hydraulic fluid causes the fluid to expand and thus the volume of fluid in the system increases, adversely affecting not only the operating pressures within the system, leading to leakage of fluid, but also the resistance to compression of the fluid itself, resulting in slower operation or, more seriously, a complete breakdown of the hydraulic system. The problems associated with overheating are aggravated at higher ambient temperatures, where evaporation of the hydraulic fluid may result.

To avoid the problems of externally-carried hoses, they may be disposed internally of the boom arm but this results in increased overheating of the hydraulic fluid, as heat can only be dissipated in the air within the arm and by radiation from the walls of the arm itself. This results in a very slow loss of heat when compared to the radiation of heat from the walls of an externally carried hose.

Attempts have been made, in the prior art, to solve the problem of overheating either by increasing the volume of oil in the system, thereby increasing the heat dissipation capacity of the oil itself, or by increasing the bore of the hydraulic hoses to dissipate heat more effectively; however, this solution adversely affects the flexibility of the hoses when under pressure.

Thus, it is an object of the invention to provide a flail trimmer which improves the cooling of the hydraulic fluid and which has a boom arm which has a long extended reach but is nevertheless able to close up neatly and compactly without affecting the stability of the tractor of damaging the hydraulic system.

Accordingly, the invention provides a flail trimmer comprising a hydraulically operable boom arm assembly having a trimming or cutting working head attached thereto and being pivotably connected to a reservoir for holding hydraulic fluid, in which the reservoir includes a pair of spaced-apart substantially parallel wings extending from a side thereof, the hydraulic fluid being able to circulate within the reservoir including the wings to improve the cooling effect on the fluid, and in which the boom arm assembly is pivotably connected to the reservoir between the wings thereof.

Preferably, the boom arm assemby includes articulatablyconnected inner and outer boom arms, the outer arm carrying the working head and the inner arm being connected to the wings of the reservoir preferably at an upper and forward portion thereof, to enable the assembly to adopt a more compact folded configuration, while extending the reach thereof. Such an arrangement allows the boom arm assembly to fold in a manner such that, when attached to a tractor in use, the side of the reservoir remote from the wings may be sited behind a wheel of the tractor and does not extend laterally beyond the side of the tractor, and the working head does not protrude beyond the other side of the tractor.

The pressure pump, hydraulic hoses, rams and other ancillary parts of the assembly are preferably attached to the reservoir and are disposed between the wings, and below the connecting axis of the boom arm assembly to the reservoir.

The reservoir is preferably provided with internal baffle means to perturb the fluid as it circulates within the reservoir, to increase the degree of contact between the fluid and the reservoir walls and thus to enhance the cooling effect.

Hot oil from the working head is preferably returned to the reservoir via a combined filler point/filter assembly chamber and is internally directed primarily into the wings of the tank before being re-circulated through the main body of the reservoir and eventual return to the pressure pump. The chamber is preferably in communication via an overflow weir with the main body of the reservoir and via internal pipes with the wings thereof, the internal pipes preferably being arranged to direct oil towards the remote ends of the wings.

The inner boom arm may be of the type which is attached directly at the proximal end to the reservoir, movement being controlled by a first hydraulic ram acting directly between the reservoir and the boom arm and movement of the outer boom arm, attached to the distal end of the inner arm, being controlled by a second ram acting between the inner arm and a bracket attached as an extension beyond the pivot point of the outer arm.

Alternatively, the proximal end of the inner boom arm may be attached to the reservoir indirectly via a rocker link member to which also is attached one end of a tie arm, the other end being attached to the bracket extension of the outer arm so that the inner arm, rocker link member, tie arm and bracket extension together form a four-bar linkage for control of the outer arm by means of a hydraulic ram acting between the pivot point of the rocker link member and the inner arm. Movement of the inner arm is controlled by a hydraulic ram acting between the reservoir and the rocker link member. According to either embodiment, however, the inner boom arm is preferably connected, directly or indirectly, to the upper forward portion of the reservoir wings.

Embodiments of the invention will now be described by way of example, with reference to the accompanying drawings, of which Figure 1 is a plan view of a reservoir for use with a flail trimmer according to the invention, with the upper wall removed to show the internal parts; Figure 2 is a side view of the reservoir shown in Figure 1 with the side wall removed; and Figure 3 is a side elevation of the flail trimmer in a folded configuration.

With reference to Figure 1, the reservoir, generally indicated 1, is generally U-shaped in plan with two wings 2 extending from a body 3. A pipe 4 extends from a filling chamber 5, beneath the filler cap/filter unit 6 and the return pipe 7, into a respective wing 2. The pipes 4 serve to direct oil returning through the pipe 7 into the wings 2 rather than allow it to overflow directly into the body 3 of the reservoir over the baffle wall 8.

A plate 9 separates each wing 2 from the body 3 and is provided with slots 10 such that flow of oil between the body 3 and the wings 2 is impeded to enhance the cooling of the oil.

Referring to Figure 3, the boom arm assembly consists essentially of an inner boom arm 11, an outer boom arm 12 and a cutting head 13. The inner arm 11 is attached to the wings 2 of the reservoir 1 via a rocker link 14; a tie arm 15 is also pivotably attached at the same location and connects to a bracket 16 formed at the inner end of the outer boom arm. The components form a four-bar linkage for operative control of the outer arm under power exerted from double-acting hydraulic ram 17; a further ram 18 acts on the rocker link 14 to control movement of the inner boom arm. As shown, the rocker link is pivotably journalled between the wings 2 of the reservoir 1 in bushes 19 (see also Figures 1 and 2) and the cylinder of ram 18 is connected to a mounting bracket 20 located between and towards the lower part of the reservoir. The compressor for the oil is also located in this region, together with associated pipework, control parts and the like ancillary equipment. The mounting of the boom arm assembly between the wings of the reservoir increases the overall reach of the boom without extending the length of the individual arms, while permitting the boom assembly to provide a compact folded arrangement for storage and transportation and also for use in the working mode, in confined spaces such as when trimming the front side of a high hedge or a bank in a narrow lane.

In use, oil is introduced into the system through the filler cap 6 to the filling chamber 5 directly below.

The oil flows from there to fill both of the wings 2 and the body 3. Oil leaves the tank 1 through a hose attached to pipe 21 and is pressurised in the compressor; it is then circulated through the operative parts of the system as required. Eventually the oil returns to the tank 1 through the return pipe 7 and is directed into the wings 2 by the pipes 4. The oil is cooled by contact with the surface of the wings 2 and is passed through the slots 10 in the plate 9, which acts as a further cooling surface, and enters the main body 3 of the reservoir for further cooling. The provision of the increased surface area of the tank available for cooling reduces the circulating temperature of the oil, in use, by up to about 200C when compared with known systems.

The flail trimmer as described may advantageously use hoses carried internally of the boom arms, especially for powering the hydraulic ram (not shown) controlling the disposition of the cutting head as well as the rotation of the cutter elements themselves.

Claims (11)

1. A flail trimmer comprising a hydraulically operable boom arm assembly having a trimming or cutting working head attached thereto and being pivotably connected to a reservoir for holding hydraulic fluid, in which the reservoir includes a pair of spaced-apart substantially parallel wings extending therefrom, the hydraulic fluid being able to circulate within the reservoir including the wings to improve the cooling effect on the fluid, and in which the boom arm assembly is pivotably connected to the reservoir between the wings thereof.

2. A flail trimmer according to Claim 1, in which the boom arm assembly includes articulatably-connected inner and outer boom arms, the outer arm carrying the working head and the inner arm being connected to the wings of the reservoir.

3. A flail trimmer according to Claim 1 or Claim 2, in which the inner arm is attached to the wings of the reservoir at an upper and forward position thereof.

4. A flail trimmer according to any one of Claims 1 to 3, in which the pressure pump, hydraulic hoses, rams and other ancillary parts of the assembly are attached to the reservoir and are disposed between the wings, below the connecting axis of the boom arm assembly to the reservoir.

5. A flail trimmer according to any preceding claim, in which the reservoir is provided with internal baffle means to perturb the fluid as it circulates within the reservoir.

6. A flail trimmer according to any preceding claim, in which the reservoir includes means to direct hot oil from the working head primarily into the wings, thence to the main body of the -reservoir and thence to the pressure pump.

7. A flail trimmer according to Claim 6, in which the reservoir is internally divided into a receiving chamber for fresh or recirculating oil which is in communication via an overflow weir with the main body of the reservoir and via internal pipes with the wings thereof.

8. A flail trimmer according to any preceding claim, in which the inner boom arm is attached directly at the proximal end to the reservoir, movement being controlled by a first hydraulic ram acting directly between the reservoir and the boom arm, movement of the outer boom arm, attached to the distal end of the inner arm, being controlled by a second ram acting between the inner arm and a bracket attached as an extension beyond the pivot point of the outer arm.

9. A flail trimmer according to any one of Claims 1 to 7, in which the proximal end of the inner boom arm is attached to the reservoir indirectly via a rocker link member to which also is attached one end of a tie arm, the other end being attached to a bracket extension of the outer arm so that the inner arm, rocker link member, tie arm and bracket extension together form a four bar linkage for control of the outer arm by means of a hydraulic ram acting between the pivot point of the rocker link member and the inner arm, movement of the inner arm being controlled by a hydraulic ram acting between the reservoir and the rocker link member.

10. A flail trimmer according to any preceding claim, in which the inner boom arm is connected directly or indirectly to the upper forward portion of the reservoir wings.

11. A flail trimmer substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.