EP0354675A1

EP0354675A1 - Apparatus for connecting a towed implement to a tractor

Info

Publication number: EP0354675A1
Application number: EP89307352A
Authority: EP
Inventors: John D. Campbell
Original assignee: Rapitex Systems Ltd
Current assignee: Rapitex Systems Ltd
Priority date: 1988-07-20
Filing date: 1989-07-20
Publication date: 1990-02-14
Also published as: GB8817302D0

Abstract

Apparatus for connecting a towed implement, particularly a road maintenance implement (2) to a tractor comprises a frame (10) connected between the implement and the tractor and having drive wheels (14) driven by a hydraulic motor (20) mounted on the frame and supplied from the tractor hydraulics. The frame can be raised and lowered, for example by hydraulic rams (22), so as to apply downward pressure on the drive wheels (14) sufficient to lift the rear wheels (4) of the tractor from the ground. The tractor and towed implement can then be propelled by the drive wheels (14). The controls for the drive motor (20), and for the towed implement if it is powered, may be mounted on the tractor so that they can be operated from the drivers seat. The towed implement is detachable from the apparatus, so that different implements can be used with the same apparatus, avoiding the need for the separate drive motor, controls and steering gear used on conventional road maintenance equipment. The frame (10) can be raised to lift the drive wheels (14) from the ground, for transport by the tractor to the working location.

Description

This invention relates to apparatus for connecting a towed implement to a tractor.
More particularly, but not exclusively, the invention relates to apparatus for connecting a road maintenance implement to a tractor.
Road maintenance implements, such as planers for removing unwanted material from the surface of a road or pavement, and flail machines for grooving and texturing such surfaces, are usually in the form of self propelled machines. It would be desirable to provide such implements in the form of "function modules" which could be attached to a tractor, such as a conventional agricultural or industrial tractor. This would avoid the necessity of providing equipment such as a drive engine and steering gear for each implement. However, two problems arise. First, conventional tractors go too fast for many operations which are performed by road maintenance equipment. Second, the speed control of conventional agricultural or industrial tractors, employing discrete gear changes, is not adequate, compared with the continuously variable speed control used in self propelled road maintenance machines.
This invention consists in apparatus for connecting a towed implement to a tractor, the apparatus having drive wheels and means for lowering the drive wheels into engagement with the ground and for applying downward pressure on the drive wheels so as to lift the rear wheels of the tractor from the ground, and having drive means for driving the wheels of the apparatus to effect movement of the apparatus and the tractor.
Preferably, the apparatus comprises a frame adapted to be connected to the tractor, the towed implement being connected in use to the frame.
Preferably, the drive means on the apparatus has a continuously variable speed control. The drive means may, for example, be a hydraulic motor carried on the apparatus and connected in use to the hydraulic system of the tractor.
In accordance with the invention, a number of different implements may be provided for attachment to the apparatus. For example, different road maintenance implements could be provided. Each implement could be provided as a separate module, with a common form of attachment to enable the module to be readily attached to and detached from the apparatus. Power to the module, for example for driving planing cutters, can be supplied by an engine in the module, or, preferably, from the power take off shaft of the tractor. The speed of operation of the cutters, or other mechanisms of the implement, can therefore be controlled independently of the forward speed of the apparatus.
For some applications, such as planing a road surface, it is useful to be able to press the cutting heads hard down onto the road surface. To allow for this, the apparatus may be adapted to allow part of the weight borne by the drive wheels to be transferred to the implement. For example, means may be provided for adjusting the orientation of the frame of the apparatus relative to the tractor.
The invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which:

Figure 1 is a side elevation of apparatus and a towed function module in accordance with the invention, attached to a tractor,
Figure 2 is a plan view of the apparatus and module, with the module detached from the apparatus, and
Figure 3 is a rear elevation of the apparatus, with the module omitted.

Referring to the drawings, apparatus consisting of a mounting and propelling section 1 connects a function module 2 to a tractor 3. The mounting and propelling section 1 consists of a rigid frame 10 connected at points 12 to the lower links 13 of the three-point linkage of the tractor so that the frame can move vertically relative to the tractor. Two drive wheels 14, about 400mm in diameter, are carried on an axle 16 mounted in suitable bearings on the frame 10. The wheels are driven by a suitable transmission, such as a chain drive 18, from a hydraulic motor 20 carried on the frame 10 and connected to the hydraulic circuit of the tractor through a control valve (not shown).
The frame 10 can be raised and lowered by means of two double acting hydraulic rams 22 each connected between a fixed anchorage 23 on the tractor and a point 24 on a frame member 25 in the lower part of the frame 10. A third hydraulic ram 26 acts between a fixed point 27 on the tractor and the upper end of a frame member 28 pivoted at its lower end to the frame 10. The upper end of member 28 is connected to the upper part of the frame 10 by means of an adjustable link 30. A pair of tow bars 32 are connected between the tractor and the frame 10 to provide the principal means of traction. The hydraulic rams 22 and 26 are connected to the hydraulic circuit of the tractor through suitable control valves (not shown).
The function module 2 has a body 50 having a drum 52, for example with planing cutters, and a drive mechanism 53 coupled by a suitable shaft to the power takeoff shaft of the tractor. The body has pairs of upper and lower brackets 54 and 56 to attach the function module rigidly to the rear part of the frame 10, the upper brackets 54 being removable to enable the module to be attached to and detached from the frame 10. The module may be provided with rear wheels 58, the height of which can be adjusted by a suitable mechanism 60 to vary the depth of cut, and to enable the orientation of the module to be adjusted, for example to modify the camber of the surface on which the module is working.
Operation of the hydraulic rams 22 moves the frame 10 between a raised position in which the frame 10 and module 2 are lifted from the ground, for transport by the tractor to the working location, and a lowered position in which the drive wheels 14 engage the ground and the rear wheels 4 of the tractor are lifted clear of the ground. In this position, forward movement of the apparatus is effected by the drive motor 20 acting through wheels 14. The speed of forward movement is therefore governed by the speed of the hydraulic motor 20, which can be controlled using a conventional control valve, to give an infinitely variable forward speed. The front wheels of the tractor remain in contact with the ground, so that the tractor can be steered in the usual way.
The throws of rams 22 and ram 26 are selected in accordance with the geometry of the frame 10 so that the frame is kept in the same orientation as it is raised and lowered. The orientation of the frame 10 can be adjusted to a limited extent by adjusting the length of link for example to transfer some of the weight from the wheels 14 to the drum 52. The link 30 may, for example, be a threaded rod fixed at one end to the frame member 28 and extending through a hole in an upper member of the frame 10, with a nut 31 engaging the end of the rod and rotatable to adjust the effective length of the link. A compression spring 33 surrounding the threaded rod acts between the frame member 28 and the frame 10, to allow compression of the link to acommodate movements of the module 2 due to irregularities in the surface over which the module is moved. The up and down movement of the frame 10 relative to the tractor is effected by the double-acting rams 22, with the ram 26 maintaining the correct orientation of the frame. The lower links of the tractor three-point linkage are used only to provide the necessary vertical freedom of movement of the frame, the hydraulic system of the tractor being employed only to provide hydraulic pressure for the rams 22 and 26 and the hydraulic motor 20.
The control valves for the hydraulic rams 22 and 26 and for controlling the speed of the drive motor 20 may be grouped in a control module mounted on the tractor so that they can be operated from the driver's seat.
The described apparatus thus provides a means of attaching various function modulus to a tractor, whilst enabling the apparatus to be driven at a controllable low speed. In the described embodiment, the only modifications required to the tractor are the provision of a bracket to provide the anchorage for the hydraulic rams, and the mounting of the control valve module in a suitable position. The apparatus can therefore easily be connected to any conventional industrial or agricultural tractor.
It will be appreciated that the apparatus and function module could take forms different from those shown in the drawings. For example, the frame of the apparatus could be adapted to be connected in a fixed position to the tractor, and the drive wheels could be mounted so as to be movable relative to the frame.

Claims

1. Apparatus for connecting a towed implement (2) to a tractor (3) the apparatus (1) having drive wheels (14) and means (22) for lowering the drive wheels into engagement with the ground and for applying downward pressure on the drive wheels so as to lift the rear wheels (4) of the tractor from the ground, and having drive means (20) for driving the drive wheels (14) of the apparatus to effect movement of the apparatus and the tractor.

2. Apparatus as claimed in Claim 1, in which the drive means (20) of the apparatus has a continuously variable speed control.

3. Apparatus as claimed in Claim 2, in which the drive means (24) comprises a hydraulic motor carried on the apparatus (1) and connected in use to the hydraulic system of the tractor.

4. Apparatus as claimed in any one of Claims 1 to 3, in which the apparatus comprises a frame (10) adapted to be connected to the tractor (3) and the towed implement (2) is detachably connected to the frame (10).

5. Apparatus as claimed in Claim 4, and including a number of different implements each adapted to be detachably connected to the frame (10).

6. Apparatus as claimed in Claim 4 or Claim 5 in which means are provided for transferring part of the weight borne in use by the drive wheels (14) of the apparatus to the towed implement (2).

7. Apparatus as claimed in Claim 6, in which the means for transferring weight comprises means for adjusting the orientation of the frame (10) relative to the tractor (3).

8. Apparatus as claimed in any preceding claim, in which the apparatus includes a frame (10) connected to the tractor so as to be movable vertically relative to the tractor, the drive wheels (14) being mounted on the frame (10) and the means for lowering the drive wheels (14) comprises means for moving the frame (10) relative to the tractor (3).

9. Apparatus as claimed in Claim 8, in which the means for moving the frame (10) comprises hydraulic rams connected in use between the tractor (3) and the frame (10).

10. Apparatus as claimed in any preceding claim, in which the towed implement (2) comprises road maintenance equipment.