GB2029784A - Improvements in or Relating to Tractive Vehicles - Google Patents

Abstract

A tractive vehicle capable of operation in both directions of travel and capable of surmounting obstacles and of maintaining adhesion over a wide variety of surfaces comprises a frame, a plurality of oleo-pneumatic struts 5 mounted on the frame for rotation on their respective axes 6, a plurality of ground-engaging wheels 8 rotatably mounted on the struts at the lower ends thereof so that said rotation of the struts effects steering movement of the wheels, and a hydrostatic drive for the wheels including a prime mover on the frame and a plurality of hydrostatic motors on the respective struts at the lower ends thereof and drivingly coupled to the respective wheels. There is thus provided a vehicle with its wheels all driven, all steerable and all independently suspended. <IMAGE>

Description

SPECIFICATION Improvements in or Relating to Tractive Vehicles This invention relates to tractive vehicles, the chief object being to provide a versatile agricultural tractor capable of operating efficiently on and off the road irrespective of the surface conditions.

According to the present invention a tractive vehicle comprises a frame, a plurality of telescopic struts mounted on the frame, a plurality of ground wheels rotatably mounted on the respective struts at the lower ends thereof, a prime mover on the frame and a hydrostatic transmission connecting the prime mover to the ground wheels, wherein the struts are rotatable on their respective axes to effect steering movement of the respective ground wheels, and the hydrostatic transmission includes a plurality of hydrostatic motors mounted on the respective struts at the lower ends thereof and drivingly coupled to the respective ground wheels.

By virtue of the invention there is provided a vehicle which has a multiplicity of wheels all driven, all steerable, and all independently suspended, to enable highly efficient operation of the vehicle in both directions of travel over obstructions and over a wide variety of surfaces off and on the road, without loss of adhesion, and to enable highly effective dynamic braking at all wheels.

Advantageously, assemblies or modules each comprising a strut, a wheel and a hydrostatic motor, are rotatably mounted on the frame in constructing the vehicle. Thus, a range of vehicles can readily be produced by the selection of a number of modules appropriate to a prime mover of a particular power output. For example, a vehicle constructed with four modules is capable of converting to drawbar pull the output of a prime mover of 75 h.p.; a vehicle constructed with six modules is capable of converting into drawbar pull the output of a prime mover of 100 h.p.; and a vehicle constructed with eight modules is capable of converting to drawbar pull the output of a prime mover of 1 50 h.p.; and so on.

Of course, in each case the drawbar pull which can be derived from the prime mover will vary according to the surface conditions prevailing, maximum drawbar pull being obtainable on dry tarmac.

The hydrostatic motors of the modules are rated to develop at minimal wheel speed a maximum torque at the tread of the wheel and at increasing wheel speeds proportionally lower torques.

Preferably hydraulically actuable steering means are operatively connected to the struts at the upper ends thereof.

As each wheel is steerable, a vehicle incorporating four, six, eight or more wheel modules can have a very small turning circle.

Moreover, the steering geometry may readily be modified to provide for sideways travel-an important advantage in certain conditions of work, particularly in agriculture.

Preferably also the vehicle is provided with ballasting means including open-bottomed compartment means in the frame and hydraulically operable hoisting means associated with the compartment means to enable hoisting of ballast into stowed position in the compartment means following positioning of the vehicle with the compartment means disposed vertically over the ballast. In this way the vehicle is capable of operating with high efficiency over a wide variety of soils and surfaces.

Preferably also the struts of the modules are oleopneumatic struts interconnected in a hydraulic circuit in which the pressure is adjustable. Thus, following each loading or unloading of ballast, the pressure in the circuit may be adjusted to restore the struts to their midpositions to ensure optimum performance of the vehicle over undulating terrain.

An embodiment of the invention will now be described by way of example with reference to the accompanying diagrammatic drawings in which: Fig. 1 is a side elevation of an eight-wheel hydrostatic tractive vehicle.

Fig. 2 is a top plan view of the vehicle; Fig. 3 is a sectional top plan view on the line Ill-Ill of Fig. 1; Fig. 4 is a transverse sectional view on the line IV--IV of Fig. 3; Figs. 5 and 6 are respectively front and rear end elevational views of the vehicle, and Figs. 7 to 9 are plan views respectively illustrating three different steering modes selectively 'avaiiable to the driver.

A tractive vehicle for agricultural use comprises an elongate rectangular hull or frame 1, and two longitudinal rows 2 and 3 of frame-supporting assemblies or modules 4 mounted on the frame 1 respectively at opposite sides thereof, each row consisting of four equispaced assemblies or modules 4 whereof two are at opposite extremities of the frame.

Each frame-supporting assembly or module 4 comprises an upright telescopic nitrogen/oil suspension strut 5 mounted on the frame 1 for steering rotation on the strut axis 6, a radial stub shaft 7 on the strut 5 at the lower end thereof, a rubber-tyred ground wheel 8 rotatably mounted on the stub shaft 7, a hydrostatic motor 9 on the strut 5 at the lower end thereof and drivingly coupled to the wheel to form a hub, and a radial steering arm (not shown) on the rotatable strut 5 at the upper end thereof.

The frame 1 (Figs, 3 and 4) is in the form of an elongate box section beam 10 whereof the top flange 11 has lateral extensions 12 supported by laterally projecting strengthening plates 13 on the side webs 14 of the beam 10. Plates 15 and 16 close the ends of the frame whereof the lateral extensions 12 have depending flanges 17 at the outer edges. The beam has therein a pair of transverse partitions 18 and 19, forming a central compartment 20 and a pair of end compartments 21 and 22. The strengthening plates 13 are spaced longitudinally to form in the frame a series of open-bottomed boxes 23 in which are mounted the upper ends of the struts 5 of the assemblies 4. The frame has thereon hydrostatic and pneumatic systems serving the assemblies 4.

Thus, the central compartment 20 of the frame contains the following (not shown):-- a horizontal 150 h.p. air-cooled diesel engine and a pair of hydraulic oil pumps driven in tandem by the engine through a splitter gearbox. The pumps are drivingly connected to the eight hydrostatic motors 9 of the assemblies 4 through flexible pipes. The central compartment 20 also contains the following (not shown):- an oil reservoir, hydraulic valves, and a hydraulic oil cooler. Each hydrostatic motor has two oil circuits, the first providing for half torque and high rotational speed and the second providing for maximum torque and low rotational speed. The working pressure of the hydrostatic drive is 5000 p.s.i.The hydrostatic drive provides for fore-and-aft and transverse limited slip of the wheels 8, and the driving of all the hydrostatic motors simultaneously and selectively in either direction, that is, for ambidirectional travel, for control of the torque output and vehicle speed and for braking of the vehicle.

The frame 1 has thereon an auxiliary hydraulic circuit with a supply pressure of 1,000 p.s.i. The auxiliary circuit supplies hydraulic rams (not shown) disposed at the tops of the assemblies 4 and connected to the steering arms of the assemblies so that each assembly is steerable through a 60O arc (Fig. 7). A control system (not shown) for the steering is also provided on the frame 1 and includes an electric stepper motor operable by a three-position switch to meter oil to the rams of the assemblies 4.This control system provides for selection from the following three modes of steering of the vehicle:- (a) all wheel steering around the vehicle centre, as shown in Fig. 8,-the wheels adopt a geometry such that they run on inner and outer steering circles, (b) parallel or crab steering, as shown in Fig. 7-the wheels allow for sidewise travel of the vehicle the wheels running on a series of parallel lines and the angles of the wheels to the axis of the machine being variable under driver control, and (c) highway steering, as shown in Fig. 9,-the two pairs of wheels in the direction of travel of the vehicle steer on a circle whereof the centre is at the trailing end of the vehicle; this mode is adopted for road use and, in particular, for towing on tarmac surfaces.

The auxiliary hydraulic circuit also supplies oil to the struts 5 of the assemblies 4, providing for adjustment of the oil pressure in the struts so that the suspension is at substantially its mid position of travel irrespective of hereinafter described controlled variations in the loading of the frame.

Each strut 5 is capable of a totai vertical travel of 9 inches.

Apertured towing lugs 24 and 25 depend from the bottom flange 26 of the beam at opposite ends of the beam.

A pair of fore-and-aft power-operated threepoint hitch linkage systems 27 and 28 served by said auxiliary hydraulic circuit are mounted on the frame 1 at opposite ends thereof to enable two sets of implements or other attachments to be carried simultaneously and so enable the operator to utilise to the full the ability of the vehicle to perform equally in both directions of travel.

A hydraulic jacking system for the vehicle includes four jacks 29 (Fig. 3) mounted on the beam webs 14 at the ends of the beam and served by said auxiliary hydraulic circuit.

The end compartments 21 and 22 of the beam 10 have rectangular openings 30 and 31 (Figs, 3 and 4) in their floors 26, and the beam 1 0 carries adjacent the openings 30 and 31 a pair of hydraulic hoists (not shown) incorporated in the auxiliary hydraulic circuit of the vehicle. The hoists lift and lower cast-iron ballast blocks 32 and 33 through the openings 30 and 31 in the floors of the end compartments 21 and 22 to stow the blocks in the end compartments and deposit them on the ground. The vehicle is readiiy manoeuvred to a position in which the floor openings 30 and 31 are disposed directly over spaced blocks 32 and 33 on the ground, whereupon the hoists are operated, to stow the blocks in the beam. Thus, the vehicles loading can be varied to suit different ground conditions.

Steering means 34, controls (not shown) for the various systems, and an armchair 35 for the driver of the vehicle are provided on a platform 36 disposed above the central compartment 20 and mounted on the beam 10 for rotation through 1 80O to give the driver, selectively, three directions of vision whereof one is transverse of the vehicle axis and is particularly useful during ploughing with implements attached to the vehicle at the ends thereof. A driver's hood 37 of frusto-pyramidal shape encloses the platform and is hingedly mounted on the frame 1 at 38 for tilting to an open position as shown by broken lines in Fig. 1 to give the driver access to the platform 36. A wall 39 of the hood 37 is hingable to open position as indicated by broken lines in Fig. 2 to give the driver access to the hood. The sight lines of the driver are indicated at 40 and 41 in Fig. 1.

In operation of the vehicle, it performs equally well when travelling in either direction, and so is distinguished from the traditional vehicle which performs adequately in the forward direction but has only limited performance in the reversed direction. The vehicle has a very small turning circle, and the hydraulic system and independent suspension ensure that in the event of any wheel losing adhesion with the soil or road, the remaining wheels will maintain the tractive effort.

Moreover, the ease with which the ballast loading and strut pressure can be altered ensures that the loading and vertical reciprocation of the wheels are always optimal for a wide-range of ground conditions from undulating to flat and from very soft to very hard.

Claims (9)

Claims

1. A tractive vehicle comprising a frame, a plurality of telescopic struts mounted on the frame, a plurality of ground wheels rotatably mounted on the respective struts at the lower ends thereof, a prime mover on the frame, and a hydrostatic transmission connecting the prime mover to the ground wheels, wherein the struts are rotatable on their respective axes to effect steering movement of the respective ground wheels, and the hydrostatic transmission includes a plurality of hydrostatic motors mounted on the respective struts at the lower ends thereof and drivingly coupled to the respective ground wheels.

2. A vehicle according to claim 1, including hydraulically actuable steering means operatively connected to the struts at the upper ends thereof.

3. A vehicle according to claim 2, wherein the steering means are adjustable to give a wheel geometry providing for sidewise travel of the vehicle.

4. A vehicle according to claim 2 or 3, wherein the steering means are adjustable to give a wheel geometry providing for rotation of the vehicle about the centre thereof.

5. A vehicle according to any one of the preceding claims, including ballasting means comprising open-bottomed compartment means in the frame and hydraulically operable hoisting means associated with the compartment means to enable hoisting of ballast into stowed position in the compartment means following positioning of the vehicle with the compartment means disposed vertically over the ballast.

6. A vehicle according to claim 5, wherein the telescopic struts are oleo-pneumatic, and an hydraulic circuit interconnects the struts and is adjustable to restore the struts to their mid positions following each loading or unloading of the ballast.

7. A vehicle according to claim 5 or 6, wherein the frame comprises a box-section beam extending fore-and-aft and a pair of transverse partitions in the beam forming with the beam a central compartment and a pair of end compartments, the prime mover being housed in the central compartment and the end compartments constituting the compartment means for the ballast.

8. A vehicle according to claim 7, including a platform for the driver disposed over the central compartment and mounted on the beam for rotation through 1 800, and control means on the platform for actuation by the driver.

9. A vehicle according to claim 8, including a hood enclosing the platform and hingedly mounted on the beam for tilting to an open position to give the driver access to the platform.

1 0. A tractive vehicle substantially as hereinbefore described with reference to the accompanying drawings.