GB2338393A

GB2338393A - Articulated arm for plant cutter

Info

Publication number: GB2338393A
Application number: GB9913344A
Authority: GB
Inventors: Jacques Bachmann
Original assignee: Noremat SAS
Current assignee: Noremat SAS
Priority date: 1998-06-17
Filing date: 1999-06-08
Publication date: 1999-12-22
Anticipated expiration: 2019-06-08
Also published as: GB2338393B; GB9913344D0; FR2779903B1; FR2779903A1

Abstract

The device comprises a frame (10) bearing an articulated arm (2) to which is coupled a machine (3) for cutting plants. The articulated arm (2) is formed of at least one lower segment (21), the lower end of which is mounted to be mobile in rotation in a point of articulation (12) of the frame, a lower piston-cylinder unit (41) being arranged between said frame (10) and said lower segment (21) in order to adjust the angle A formed by said lower segment (21) with the horizontal. According to the invention, the lower piston-cylinder unit (41) is a single-action piston-cylinder unit for the work of cutting grass or low hedges, and is a double-action piston-cylinder unit when working at a height for which the angle A is greater than a given value.

Description

2338393 1 SECURE DEVICE FOR CUTTING PLANTS The present invention relates

generally to devices used for cutting plants, and more particularly for tidying the verges of roads. These devices usually comprise a carrier vehicle, a lorry or tractor, on which is mounted an articulated arm to the free end of which there is fastened a machine called a hedger.

The articulated arm is formed of two segments, an upper and a lower one, articulated one on the other to form callipers; it is fastened so as to be mobile in rotation about a horizontal axis on a frame which itself is mounted to be mobile in rotation about a vertical axis on the carrier vehicle.

is A lower hydraulic piston-cylinder unit is arranged between the frame and a point close to the upper end of the lower segment in order to adjust the angle between said lower arm and the frame.

An upper hydraulic piston-cylinder unit is arranged between the lower and upper segments of the arm so as to adjust the angle between these segments.

During operation, the driver of the carrier vehicle adjusts the distance between the hedger and the vehicle and the cutting height by actuating the lower and upper piston-cylinder units.

The driver acts on the distributors supplying the lower and upper pistoncylinder units so as permanently to adapt the position of the machine relative to the terrain to be cut as a function both of the profile of the terrain to be cut and the profile of the zone on which the carrier vehicle advances.

So as to prevent the machine from butting against the ground and being damaged when the driver has been unable to raise it in time, it is necessary for the lower piston-cylinder unit to be such that its cylinder rod can return freely so as to permit the arm to be raised so that the machine follows the profile of the 2 ground.

For this to be possible, it is necessary for the lower piston-cylinder unit to be a single-action piston-cylinder unit, that is to say, a pistoncylinder unit in which the hydraulic liquid is taken into a single chamber, the chamber through which the cylinder rod passes, while the other chamber is open to the air.

The cutting machines are not used only for mowing plants in a substantially horizontal plane, but are also used for cutting hedges in a substantially vertical plane. During the hedge-cutting operation, the piston- cylinder units of the articulated arm are controlled so as to position the machine at the height at which it is desired to cut the plants.

When cutting has to be effected at a great height, the operator is obliged to bring the articulated arm into a position such that its centre of gravity approaches a position located vertically to its point of articulation on the frame of the carrier vehicle. It may then happen that a movement of the carrier vehicle causes the arm to oscillate until its centre of gravity is brought beyond its maximum position corresponding to the vertical to the point of articulation.

In this case, the weight of the arm and of the machine which it bears on the piston-cylinder unit, which, since said piston-cylinder unit is a single- action one, causes the rod thereof to withdraw and the arm to swing towards the side of the vehicle opposite the one where the work is normally carried out. This swinging offsets the weight of the machine and the arm to the side of the vehicle opposite the one where the work is supposed to be carried out, and may cause the vehicle to topple over because said vehicle is adapted to withstand overloading on the side intended for working, but is not adapted to withstand overloading on the opposite side.

The present invention aims to propose an arrangement which makes it possible to avoid this risk of toppling of the arm and the vehicle.

3 To this end, the invention relates to a secure device for cutting plants, of the type comprising a frame bearing an articulated arm to which is coupled a machine for cutting plants, in which the articulated arm is formed of at least one lower segment, the lower end of which is mounted to be mobile in rotation in a point of articulation of the frame, a lower piston-cylinder unit being arranged between said frame and said lower segment in order to adjust the angle A formed by said lower segment with the horizontal, characterised in that said lower piston-cylinder unit is a single-action piston-cylinder unit for the work of cutting grass or low hedges, and is a double-action piston-cylinder unit when working at a height for which the angle A is greater than a given value.

The device according to the invention is also notable in that:

is the lower piston-cylinder unit comprises two chambers supplied with hydraulic fluid by distributors, a first distributor is arranged on pipes connecting a first chamber of said lower piston-cylinder unit to a reservoir, said first distributor has two positions: a first position in which the hydraulic fluid can circulate from the first chamber of the piston- cylinder unit to the reservoir, and a second position in which the pipes are cut off, it comprises means for displacing the slide of said first distributor from 25 the first position to the second position when the angle A becomes greater than a given value, said means are formed by a cam arranged on the lower segment of the articulated arm so as to control the displacement of the slide of the first 30 distributor, a second distributor is connected firstly to the two chambers of the 4 piston-cylinder unit by pipes and secondly to a pump and to the reservoir by pipes, said second distributor has three positions:

a first position in which the angle of inclination A is increased by connecting the first chamber to the reservoir and by making the pump feed into the other chamber, a second position in which the communication between the pistoncylinder unit on one hand and the reservoir or the pump on the other hand is cut, a third position in which the angle of inclination A is reduced by making the pump feed into the first chamber and by connecting the second chamber to the reservoir, said second distributor is controlled by a lever made available to the driver of the carrier vehicle.

The invention will be better understood with reference to the following description, which is given by way of non-limitative example, with reference to the appended drawings, in which:

Figure 1 is a view of the rear of a vehicle equipped with an articulated arm bearing a cutting machine, Figure 2 is a partial view on a large scale of the foot of the articulated arm, Figure 3 shows the hydraulic control circuit for the lower piston- cylinder unit used in the device according to the invention.

Figure 1 shows a diagram of a carrier vehicle 1 equipped with a frame bearing an articulated arm 2 to which is fastened a machine 3 for cutting plants, for example a hedger.

The articulated arm 2 is, in known manner, formed of two segments, the lower segment 21 and the upper segment 23. These two arm segments are articulated to each other at a point 22 so as to form callipers.

The frame 10 is ordinarily mounted at the rear of the carrier vehicle, and is mounted to be mobile in rotation relative to a vertical axis so as to permit adjustment of the position of the cutting machine 3 in the axial direction of displacement of the carrier vehicle.

The lower end of the lower segment 21 of the articulated arm 2 is is mounted to be mobile in rotation about a horizontal axis at a point 12 of the frame.

Two hydraulic piston-cylinder units make it possible to adjust the configuration of the arm according to the work to be carried out, in order to position the cutting machine suitably relative to the carrier vehicle 1 and to the vegetation to be cut.

The lower piston-cylinder unit 41 is arranged between the frame 10 and the lower segment 21 of the arm in order to adjust the angle A formed by said lower segment 21 with the horizontal. In the example illustrated in the drawing, it is connected to the frame 10 by a support 46 and to the lower segment 21 of the arm by its cylinder rod 45.

The upper piston-cylinder unit 42 is located between the segments 21 and 23 of the articulated arm 2 so as to adjust the angle of the callipers.

The lower piston-cylinder unit 41 is usually a drawing single-action piston- 6 cylinder unit, that is to say, a piston-cylinder unit of which only the chamber through which the piston rod passes is supplied with hydraulic fluid, the other chamber remaining open to the air. Such an arrangement makes it possible to adjust the angle A by sending more or less hydraulic fluid into the chamber through which the cylinder rod passes, but to leave the arm free during movement aiming to increase said angle A so as to enable to the machine to be raised freely to follow the profile of the ground, for example when passing over bumps in the ground.

Figure 1 shows the position adopted by the articulated arm 2 when it is desired to cut a hedge at a height. The angle A between the lower segment 21 of the arm and the horizontal is very large, which brings said segment 21 into a position in which it is inclined towards the right relative to a vertical plane passing through the point of articulation 12 of the frame, whereas working is normally effected with said segment tilting towards the left in the example shown in the drawing.

The angle of opening of the articulated arm, that is to say, the angle between the two segments 21 and 23, is also very large.

Since the cutting machine 3 is a very heavy element of the articulated arm/machine assembly, the centre of gravity of this assembly is positioned at the level of said machine, so that in the position illustrated in the drawing this centre of gravity is still located to the left of the vertical line passing through the point of articulation 12.

The problem which sometimes arises during this type of work occurs when a movement of said vehicle causes the articulated arm to oscillate in a direction which tends to increase the angle A. Upon such oscillations of the articulated arm, the centre of gravity of the assembly which it forms with the machine 3 can be brought to the right of the vertical line V passing through the point of articulation 12. In this position, the weight of the articulated arm and 7 of the machine bears on the piston-cylinder unit 41 in the direction in which the latter is left free, and as a result the articulated arm 2 can then continue its rotational movement until the piston butts against the bottom of the pistoncylinder unit.

In this position, the arm and the machine are inclined towards the right in the example shown in Figure 1, and the carrier vehicle may no longer withstand this load and may keel over on its side, when the counterweight 13 provided on the right-hand side of the vehicle to stabilise said vehicle during operation on the left-hand side thereof is no longer useful and even accentuates the overloading.

In order to overcome this problem, the present invention proposes modifying the lower piston-cylinder unit 41 such that it is a singleaction piston cylinder unit for the work of cutting grass or low hedges, and is a double-action piston-cylinder unit when working at a height for which the angle A is greater than a given value.

According to the invention, the two chambers 43 and 44 of the piston cylinder unit are supplied with hydraulic fluid by using two distributors 5 and 6.

The first distributor 5 is arranged on the pipes 54, 57 connecting the first chamber 44, through which the piston rod 45 does not pass in the example of embodiment shown in the drawing, to a reservoir 7. This first distributor 5 has two positions, a first position 51 in which the hydraulic fluid can circulate from the piston-cylinder unit towards the reservoir, and a second position 511 in which the pipes 54, 57 are cut off.

The slide of this first distributor is connected to a lever 55 and elastic return means (not shown in the drawing) which return said slide into the first position 51.

8 The second distributor 6 is connected firstly to the two chambers 43, 44 of the piston-cylinder unit 41 via pipes 63 and 64, and secondly to a pump 8 and to the reservoir 7 via pipes 68 and 67.

This second distributor 6 is a distributor controlled by a lever 60 made available to the driver of the carrier vehicle which is similar to that commonly used to adjust the inclination of the lower segment 21: a driver used to driving a carrier vehicle for maintaining green spaces will come up with the same gestures to drive a vehicle equipped in accordance with the invention.

is The second distributor 6 has three positions:

a first position 61 in which the angle of inclination A is increased by interconnecting the pipes 63 and 68 on one hand and the pipes 64 and 67 on the other hand, which causes the pump 8 to feed into the second chamber 43, through which the piston rod 45 passes in the example of embodiment illustrated in the drawing, whilst the first chamber 44, through which the piston rod 45 does not pass, is connected to the reservoir 7, a second position 611 in which communication is cut between the pipes 63, 64 and the pipes 67, 68, in this position in which communication is cut between the piston-cylinder unit 41 and the reservoir 7 or the pump 8, a third position 6111 in which the angle of inclination A is reduced by interconnecting the pipes 63 and 67 on the one hand and the pipes 64 and 68 on the other hand, which causes the pump 8 to feed into the first chamber 44 and connects the second chamber 43 to the reservoir 7.

Return springs 61 bring the second distributor 6 towards the second position 611 when the driver does not act on the lever 60.

9 According to the invention, a cam 25 is arranged on the lower segment 21 of the articulated arm so as to be able to control the displacement of the slide of the distributor 5 when the angle A becomes greater than a given value. As can be seen in Figure 3, as long as the angle A is less than a given value, the slide of the distributor 5 is arranged such that said distributor is in its position 51.

The first chamber 44 of the piston-cylinder unit 41 is then connected to the reservoir and the piston-cylinder unit 41 controlled by the distributor 6 operates as a single-action piston-cylinder unit.

As soon as the predetermined angle A is exceeded (see Figure 2), the cam 25 bears on the lever 55 to displace the slide of the distributor 5 in order to bring it into its position 511.

In this position, communication is cut between the pipe 54 and the reservoir 7. The piston-cylinder unit is then controlled by the distributor 6 as a double-action piston-cylinder unit.

In position 611 during which work is carried out when the driver does not act on the lever 60, communication between the chambers 43, 44 of the piston- cylinder unit 41 and the reservoir or the pump is cut, which means that the piston-cylinder unit 41 is locked in the position which has been determined by the driver.

In so doing, the articulated arm cannot pivot about the point of articulation 12, and therefore cannot be caused to fold up unexpectedly, jeopardising the stability of the carrier vehicle.

As will have been understood from reading the above description, the device according to the invention solves a major safety problem for the operators during the cutting of roadside hedges.

According to one variant which has not been described, the angle of inclination can be determined by sensors which are other than mechanical ones, which control the displacement of the slide of the distributor 5.

Claims

1 A secure device for cutting plants, the device being a type comprising a frame bearing an articulated arm to which is coupled a machine for cutting plants, in which the articulated arm is formed of at least one lower segment, the lower end of which is mounted to be mobile in rotation in a point of articulation of the frame, a lower piston-cylinder unit being arranged between the frame and the lower segment in order to adjust the angle A formed by the lower segment with the horizontal, the lower piston-cylinder unit has a single-action piston-cylinder unit for the work of cutting grass or low hedges, and being a double-action piston- cylinder unit when working at a height for which the angle A is greater than a given value.

2.A device as claimed in Claim 1 in which the lower piston-cylinder unit comprises two chambers supplied with hydraulic fluid by one or more distributors.

3. A device as claimed in Claim 2 in which a first distributor is arranged in a conduit connecting a first chamber of the lower piston-cylinder unit to a reservoir.

A device as claimed in Claim 3 in which the first distributor has two positions:

a first position in which the hydraulic fluid can circulate from the first chamber of the piston-cylinder unit to the reservoir, and a second position in which that circulation is stopped.

5. A device as claimed in either Claim 3 or Claim 4 in which it comprises displacing means for displacing a slide of the first distributor from a first 12 position to a second position when the angle A becomes greater than a given value.

is 6. A device as claimed in Claim 5 in which the displaying means are formed by a cam arranged on the lower segment of the articulated arm so as to control the displacement of the slide of the first distributor.

A device as claimed in any of claims 2 to 6 in which a second distributor is connected firstly to the two chambers of the piston-cylinder unit by pipes and secondly to a pump and to the reservoir by pipes.

8. A device as claimed in Claim 7 in that the second distributor has three positions:

a first position in which the angle of inclination A is increased by connecting the first chamber to the reservoir and by making the pump feed into the other chamber, a second position in which the communication between the pistoncylinder unit on one hand and the reservoir or the pump on the other hand is cut, and a third position in which the angle of inclination A is reduced by making the pump feed into the first chamber and by connecting the second chamber to the reservoir.

9. A device as claimed in Claim 7 or Claim 8 in which the second distributor is controlled by a lever actuatable the driver of a carrier vehicle for the device.

10. A secure device for cutting plants substantially as herein described with reference to the accompanying drawings.