GB2138372A - A motor vehicle such as a tractor - Google Patents

Abstract

A tractor has a lifting device (46) which can be pressed downwardly into contact with the ground, either directly or through a trestle (47). This enables the adjacent wheels (3) to be raised from the ground for removal or replacement. An auxiliary wheel (60) can be added to the main wheel disc (58). A stub shaft (65) secured to the wheel disc (58) enters a hub (62) of the auxiliary wheel, the parts being secured in position by a special bolt (75) using a wrench (85). Torque is transmitted to the auxiliary wheel (60) by bosses (70). <IMAGE>

Description

SPECIFICATION A motor vehicle such as a tractor This invention relates to a motor vehicle and particularly, although not exclusively, to a tractor for agricultural purposes.

Agricultural tractors are frequently used for a variety of purposes, for example for working in row cultures and for preparing a seed bed. In the first case relatively narrow tractor wheels are usually advantageous, whereas in the second case broad wheels or several wheels arranged side by side having a broad ground contact surface are preferred in order not to adversely affect the soil structure with a view to the future growth of the plants. However, with known tractors, the fitting and removal of wheels are time-consuming operations.

According to the present invention there is provided a motor vehicle comprising a driving engine for powering ground wheels and a lifting device which is actuable by means of a hydraulic system and which can be forcibly moved downwards.

Such a construction makes it possible to exchange, fit or remove wheels of the vehicle rapidly without loss of time.

Other aspects of the present invention relate to the fixing of a wheel to the vehicle.

One further aspect of the present invention provides a bolt having a screwthreaded shank and a polygonal head, the head having a cavity for receiving part of a wrench by means of which the bolt can be turned. Another further aspect of the present invention provides a wrench for turning a bolt, the wrench having a polygonal wall and a central pin for fitting into a central part of the bolt.

For a better understanding of the present invention, and to show how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a side view of a tractor; Figure 2 is a front view taken in the direction of the arrow II in Figure 1; Figure 3 is a view of the front end of the tractor taken in the direction of the arrow Ill in Figure 1; Figure 4 is a view corresponding to Figure 2, but illustrates an alternative configuration; Figure 5 is a sectional view showing the mounting of a wheel of the tractor; and Figure 6 is a view taken in the direction of the arrow VI in Figure 5.

The tractor shown in Figure 1 is intended for agricultural purposes or the like and comprises a frame 1 having a substantially horizontal hollow frame beam 2 extending, as shown in Figure 1, from near the rear of the front wheels 3 to the front of the rear wheels 4 of the tractor. The hollow beam 2 is disposed symmetrically with respect to the vertical, longitudinal central plane 5 of the tractor indicated in Figure 3. Near the front end of the frame beam 2 there are upwardly extending plates 6 which are welded to the two vertical faces of the beam 2. These plates 6 slope forwardly and upwardly and lie on opposite sides of a hollow frame beam 7, which extends forwardly away from the plates 6. The plates 6 and the frame beam 7 constitute a swan-neck or goose neck extension of the frame beam 2, this extension extending to a position above the rotary axis of the front wheels 3.The underside of the horizontal frame beam 7 is spaced above the top of the frame beam 2.

Near its front end, the frame beam 2 supports on its top face a driving engine 8. The driving engine 8, which is a Diesel engine, has output shafts 9 and 10 projecting respectively to the front and to the rear.

The front output shaft 9 is coupled with an auxiliary shaft 11 which is aligned with the shaft 9 and extends in the intended direction of operative travel of the tractor, so indicated by an arrow A. The shaft 11 constitutes an input shaft for driving two hydraulic pumps 12 and 13 disposed one above the other substantially above the front wheel axle for supplying fluid under pressure to the drivable and steerable front wheels 3 and the drivable rear wheels 4.

The rear output shaft 10 of the engine 8 is connected by a clutch, which is actuable from the driver's cab 14, to a change-speed device 16, which can also be operated from the cab 14. The changespeed device 16 may be a manual gear box, but is may also be a hydrostatic change-speed device, the output speed of which is steplessly variable. The change-speed device 16 has a rearwardly extending shaft which forms an input shaft for a gear wheel transmission 17, the housing of which adjoins the rear of the housing of the change-speed device 16 and which extends downwardly to a position below the underside of the change-speed gear 16 and adjacent the top of the frame beam 2. The gear wheel transmission 17 has forwardly and rearwardly projecting output shafts, the latter being designated by reference number 18.Both output shafts of the gear wheel transmission 17, are situated lower than the underside of the housing of the change-speed device 16. The forwardly projecting shaft is connected by a coupling 19, which is actuable from the cab 14, to an auxiliary shaft 20 which is provided with two universal joints and is supported at its front end by a bearing 21 mounted on the top of the frame beam 2. The drive train including the auxiliary shaft 20 is continued ahead of the support 21 as a driving shaft 22, which, like the auxiiary shaft 20, is disposed symmetrically with respect to the plane 5. The driving shaft 22 terminates approximately below the front end of the frame beam 7 and ahead of the rotary axis of the front wheels 3, where it constitutes a power take-off shaft 23.The driving shaft 22 is supported at a short distance behind its front end by a triangular support plate 24 (see also Figure 4) which is fastened at the top to the front end of the frame beam 7 and which is rigidly secured along its horizontal lower edge to a hollow beam 25 extending at right angles to the plane 5 and constituting the front axle of the tractor. The vertical support plate 24 constitutes a front end partition for the frame beam 7 and covers part of the front face of the front axle 25.

The rear face of the front axle 25 is rigidly secured nearthe middle of its length to a support plate 26, which is fastened along its top edge to the underside of the frame beam 7. The top face of the hollow front axle 25 is disposed some distance below the underside of the frame beam 7, which is approximately at the same level as the underside of the driving engine 8. The driving shaft 22 extends between on the one hand the top of the frame beam 2 and the top of the front axle 25 and on the other hand the underside of the driving engine 8 and the frame beam 7.

The rear output shaft 18 of the gear wheel transmission 17' is extended rearwardlyas an auxiliary shaft 27 which has two universal joints and is supported at its rear end by a rear axle carrying the rear wheels 4. The rear wheels 4 together with the rear axle are pivotable together relatively to the frame beam 2 about a horizontal pivotal axis which lies in the plane 5. As a result, the four wheels of the tractor can bear uniformly on the ground under all conditions. A three-point lifting device 28 is fastened to the rear axle and so is pivotable during operation with the rear axle relatively to the frame beam 2 and the other parts of the tractor which are fastened to it.

The rear end of the auxiliary shaft 27 constitutes a rear power take-off shaft which is supported by the rear axle and is pivotable with the rear axle.

The two plates 6 extend for some distance above the top of the frame beam 7. Their top edges, which are horizontal, are interconnected by a hollow tie beam 29 disposed at right angles to the plane 5 and approximately at the same level as the tops of the front wheels 3. The beam 29 is symmetrical about the plane 5 and has an overall length which is equal to about 50 to 60% of the distance between the inner side walls of the front wheels. Near the two ends of the base 29, its front face is provided with fastening lugs 30 which support two aligned pivotal shafts 31 extending normal to the plane 5 (see also Figure 3).

The pivotal shafts 31 are situated to the rear of the rotary axis of the front wheels 3 and approximately at the same vertical level as the tops of the wheels. A forwardly extending, hollow beam 32, which is parallel to the plane 5, is mounted for pivotal movement about each pivotal shaft 31. Each of the two beams 32 extends forwardly away from its pivotal shaft 31 for a distance which is about 50 to 70% of the diameter of each front wheel 3 and terminates slightly to the front of the foremost point of the front wheels 3. A beam 33 is rigidly secured to the end of each beam 32. Each beam 33 slopes downwards at an angle of about 45C to the length of the beam 32. The length of the beam 33 is substantially equal to that of the beam 32.A beam 34 is rigidly secured to the lower end of each of the beams 33 and extends verticaily when the beam 32 is approximately horizontal as is assumed above. The length of each beam 34 is approximately equal to or larger than that of the beams 32 and 33. In the position shown in Figure 1, the beams 33 terminate short of the ground, but the beams 34 may have a length such that they extend to the ground when the beams 32 are approximately horizontal.

At the joints between the beams 32 and the beams 33, approximately midway along the beams 33, and at the joints between the beams 33 and 34, the beams are rigidly interconnected by tubular members 35 which are at right angles to the plane 5. The lower ends of the two beams 34 are rigidly interconnected by a rectangular, hollow beam 36. The tubular member 35 at the joint between the beams 32 and 33 and the adjacent tubular member 35 are provided near the plane 5 with upwardly directed plates 37 which interconnect these tubular members. The plates 37 are parallel to the plane 5 and are interconnected by a stiffening plate 38 which is at right angles to the plane 5. The two plates 37 arranged symmetrically about the plane 5 are provided with a pivotal shaft 39 at right angles to the plane 5.An end of the piston rod of a double-acting hydraulic cylinder 40 is pivotable about the shaft 39.

The other end of the hydraulic cylinder 40 is pivotally connected by means of a pivotal shaft 41 lying at right angles to the plane 5 with forwardly directed lugs 42 welded to the front of the supporting plate 24. The mid point of the pivotal shaft 41 as well as the centreline of the power take-off shaft 23 lie in the plane 5. The pivotal shaft 41 is thus situated very close to the pivotal shaft 23 and lies approximately perpendicularly above the end of the power take-off shaft. In the position in which the beams 32 are approximately horizontal, the centreline of the hydraulic ram 40 slopes forwardly and upwardly and lies in the plane of symmetry 5.

The tubular member fastened between the joints between the beams 33 and 34 has secured to it a forwardly projecting hook 43, which is open at the top and lies in the plane 5. The beam 36 extends for a short distance beyond the outer faces of the beams 34 and is provided near its ends with forwardly projecting hooks 44, which are open at the top.

The opening of each of the hooks 44 can be closed at the top by a heavy latch bolt 45, which is pivotable about a pivotal shaft normal to the plane 5 with respect to the associated hook 44 and which can be fixed in the position in which it closes the cavity of the hook 44, preferably from the driver's cab 14, by means of small hydraulic rams. The proportions of each of the latch bolts 45 are such that the latch bolt can withstand an upwards force approximately equal to at least one quarter of the tractor weight, and preferably to about half the weight of the tractor or more. The hooks 44 and the hook 43, together with the beam construction 32,33, 34 which is movable by means of the ram 40, constitute a three-point lifting device 46.

Figures 1 and 2 show a trestle 47 having the general shape of an inverted V, as viewed in the direction A. The trestle 47 has lugs 48 near the top in which isjournalled a pin 49 which is positioned above the top of the tubular material of the trestle.

About midway along each limb of the trestle 47 there are pins 50 which are rigidly secured to the trestle 47 and point towards each other. The relative disposition of the pins 49 and 50 is such that they are received in the hooks 43 and 44 of the lifting device 46. The trestle 47 provided with the pins 49 and 50 constitutes an accessory for the tractor. In the position shown in Figure 1 the trestle is fastened to the lifting device 46, the pins 50 being positioned in the hooks 44 and the pin 49 being positioned in the open hook 43. The lock bolts 45 are fixed in their closed positions.

The tractor has front and rear wheels all of the same diameter, preferably about 135 cms. As shown in Figures 1,2 and 3, the wheels 3 and 4 have low-pressure pneumatictyres having a width of about 60 cms. At each end of the front axle 25, which is mounted rigidly with respect to the frame 1, is secured a king pin 5 (see Figure 2), made from tubular material. The king pins 51 support the steerable front wheels 3. The centrelines of the king pins 51 are in this embodiment substantially vertical, but they could alternatively be inclined downwardly and forwardly. The king pins 51 are fastened to the respective ends of the front axle 25 by forks 52, which support the king pins 51 pivotally near their top and bottom ends. Neartheforks 52, each king pin has rigidly secured to it a horizontal extension plate 53, which extends outwardly from the king pin.

Each extension plate 53 is rigidly secured at its outer end to a vertical plate 54 (Figures 3,2). A cylindrical tube 55 is fastened to the outboard face of each plate 54, the centreline of each tube 55 being normal to the plate 54 and normal to the plane 5 in the straightahead position shown in Figure 3. A mounting plate 56 is secured to the outboard end of each tube 55, and a hydraulic motor 57 is releasably fastened to the mounting plate 56. The hydraulic motor 57 serves to drive the associated wheel. The central part of a wheel disc or body 58 is screwed to the outboard end face of each hydraulic motor 57. The wheel disc 58 is shaped in the form of a truncated cone having a half vertex angle of about 30". The centreline of each wheel disc 58 coincides with that of the hydraulic motor and that of the cylindrical tube 55.Each wheel disc 58 is disposed so that its conical boundary faces diverge inwardly towards the plane 5. The outboard end of each wheel disc 58 is closed by an end wall 59 which is screwed to the adjacent end of the hydraulic motor 57 (see also Figure 5). As viewed from the plane 5, the wheel disc 58 is concave. The inboard edge of the wheel disc 58 is provided with a flange by means of which a wheel flange of a wheel rim 3A of the tractor can be screwed onto the wheel disc 58 (see also Figure 4). In this way the front axle 25 can be provided with relatively narrow wheels having low-pressure tyres having a width of, for example, 30 cms as an alternative to the above-mentioned wider wheels. In the disposition indicated in Figure 4 by solid lines the tractor is equipped with narrow wheels so that the tractor is suitable for running between rows of plants.If the tractor subsequently has to be used for preparing a seed bed, when it is desirable to have a large ground contact surface in order to avoid deterioration of the soil sructure with a view to the future growth of plants, the narrow wheels can be suplemented by the wider wheels having a width of, for example, about 60 cms. The fitting of only a wider wheel to an end of the front axle 25 can, of course, be carried out in an analogous manner by means of the conical wheel disc 58.

In order to enable a second wheel to be fastened to one end of the front axle 25 in a manner such that fitting and removal can be performed within the shortest possible time, the construction shown in Figures 5 and 6 is employed. The wheel to be fitted or removed is provided with a rim 60 which is connected coaxiallyto a hub 62 by tubular spokes 61. The wheel hub 62 is connected by welding, through the intermediary of a polygonal plate 63, to the outboard side of the spokes 61, and through the intermediary of a polygonal plate 64 to the inboard side of the spokes 61. The wheel hub 62 is in the form of a cylindrical tube. The end wall 59 of the wheel disc 58 fastened to the wheel motor 57 is provided with a substantially solid carrier or stub shaft 65.The carrier 65 is rotationally symmetrical with respect to the rotary axis of the wheels and its outer portion tapers outwardly. The inner portion of the stub shaft 65 is cylindrical. The stub shaft 65 is integral with a flange 66 located on the end plate 59 and fastened at its circumference to an annular plate 67 having the same thickness as the flange 66.

Near its periphery, the plate 67 has openings 68.

(There are six openings 68 in the illustrated embodiment). At places corresponding to the openings 68 in the plate 67 the plate 64 also has openings 69, the edges of which taper slightly in the outboard direction, as viewed in a direction parallel to the rotary axis of the wheel . In the mounted state bosses 70 are received in the openings 69. The edges of the bosses are also slightly tapered to match the edges of the openings 69. The bosses 70 also have cylindrical projections on their inboard faces which fit in the openings 68 in the plates 67. The bosses 70 have tapped central holes which receive bolts 71.

The heads of the bolts 71 engage the outboard faces of the bosses 70, and the shank of the bolts are screwed into relatively heavy plates 72 engaging the inner face of the end wall 59. In this way the slightly tapered outer parts of the bosses 70 constitute extensions of the carrying structure 58,59,67 intended to transmit the torque of the wheel. The outboard end of the rotationally symmetrical stub shaft 65 is provided with a cylindrical recess 73 centred on the wheel axis, and a tapped hole 74 extends inwardly from the chamber 73. When the wheel is mounted part of a fastening bolt 75 is situated in the chamber 73 and in the tapped hole 74.

This single bolt enables the whole wheel with the rim 60 to be fastened to the wheel disc 58 and hence to the tractor. The bolt 75 has a polygonal (in this embodiment hexagonal) head 76 which is in contact with the annular outer face of the wheel hub 62. On the inboard side, the head 76 meets a cylindrical part 77 of the bolt, the cylindrical boundary face of which fits in the cylindrical inner boundary of the hub 62.

The cylindrical part 77 adjoins a conical part 78 located on the inboard side of the part 77, and the conical part 78 terminates at a cyindrical part 79, the diameter of which is significantly smaller than that of the part 77 and of the inboard face of the conical part 78. The cylindrical part 79 is a close fit in the cylindrical chamber 73 of the carrier 65. Finally the cylindrical part 79 has a screwthreaded shank 80, which is screwed into the tapped hole 74 in the carrier 65. The bolt 75 also has a cylindrical cavity 81, which is coaxial with the bolt 75 as a whole and which extends from the outboard face of the head 76 into the cylindrical part 79.

A wrench 82 is used for turning the bolt 75. The wrench has a head 83 which is integral with a rod 84.

The rod terminates at the end away from the head 83 at a lever 85 which is normal to the rod 84 and has a handle 86. The head 83 of the wrench 82 has a polygonal, in this case a hexagonal, wall 87 which defines a hollow cavity which is concave as viewed in the direction away from the plane 5. The cavity bounded by the wall 87 fits overthe polygonal head 76 of the bolt 75. In the centre of the cavity bounded by the wall 87 there is a central pin 88 which is integral with the head 83. This pin fits in the central hole 81 of the bolt 75. The pin 88 projects outwardly beyond the free edge of the wall 87. The lever 85 of the wrench 82 comprises two parts 89,91. The part 89 nearer the rod 84 is rigidly secured to the rod and is provided at the end away from the rod 84 with a pivotal shaft 90, which is at right angles to, and spaced from, the centreline of the rod 84.The second part 91 of the lever 85 is pivotable about the pivotal shaft 90. The length of the part 91 may be twice that of the part 89. The handle 86 is provided at the end of the part 91 away from the pivotal shaft 90, and can turn about a pivotal shaft 92 parallel to the pivotal shaft 90. The cylindrical rod 84 is surrounded by a sleeve 93, which can be turned relatively to the part of the rod rigidly secured to the head 83 and which constitutes a hand-grip for the wrench.

As shown in Figure 3, a control lever 94 is rigidly secured to the plate 54. The lever 94 is horizontal and slants inwardly and forwardly from the front of the plate 54. At its inner end, the control lever 94 has a forwardly extending portion which constitutes an end piece 95. At a position in front of the front axle 25 there is a substantially vertical pivotal shaft 96 which is fixed with respect to the frame 1. The centreline of the pivotal shaft 96 lies in the plane 5. A steering plate 97 is pivotable about the pivotal shaft 96, this steering plate 97, as viewed on plan, being symmetrical about the plane 5 in the straight-ahead position of the tractor wheels. The plate 97 has the shape of an isosceles triangle (Figure 3) with the pivotal shaft 96 at the vertex.Near the other two corners of the steering plate 97 are mounted steering rods 99 which are pivotable about pivotal shafts 98.

The ends of the rods 99 away from the plate 97 are pivotally connected by means of pivotal shafts 100 to the ends of the control levers 94. Approximately midway between each pivotal shaft 98 and the pivotal shaft 96, the ends of the hydraulic rams 101 are pivotally connected to the steering plate 97 near its edges by pivotal shafts 102. The ends of the piston rods of the rams 101 are pivotally connected by means of pivotal shafts 103 with the extremities of the end pieces 95. The pivotal shafts 98,100,102 and 103 are parallel to the pivotal shaft 96. The hydraulic rams 101 are actuable together or separately from the driver's cab 14.When the hydraulic rams 101 are actuated together, i.e. when they are hydraulically coupled to each other the wheels 3 turn about the king pins 51 in a mutually corresponding manner, each wheel performing an overall deflection of almost 90 from lock to lock. When the hydraulic rams 101 are separately actuated, the wheels can turn independently of each other about the king pins 51.

The hydraulic wheel motors of the tractor are fed from the hydraulic pumps 12 and 13 which are directly driven by the engine 8. The pump 12 supplies the hydraulic motors of the front wheels 3 and the pump 13 supplies those of the rear wheels 4.

The supply lines ofthe hydraulic motors ofthe wheels 3 are designated in Figures 2 and 3 by reference numeral 104. Each line 104 initially runs downwards from the pump 12, then outwards, and finally passes downwards again through the hollow king pin 51. Therefore, at the king pin, the supply line 104 and the king pin are coaxial. The line 104 can pass out of the lower end of the king pin 51 and though the cylindrical tube 55 to the associated motor. In this way the supply line 104 is fixed in position with respect to the steerable wheel by the king pin 51 rotating with the wheel. The return line 105 and, if any, a leakage line 106 also pass th rough the cylindrical tube 55 but are disposed eccentrically of the king pin 51.

During operation the tractor is powered by the driving engine 8. The front output shaft 9 drives the two hydraulic pumps 12 and 13 through the auxiliary shaft 11. The pressurized hydraulic fluid is fed from the pump 12 through the above-described supply lines 104 and the associatd king pins 51 to the hydraulic wheel motors of the front wheels 3. The drive of the rear wheels 4 through the supply and return lines from the pump 13 is also effected through flexible hoses since the rear wheels 4 together with the rear axle are pivotable with respect to the frame 1.

The mode offastening the rear wheels, using wheel discs 58, is fully identical to that of the front wheels 3 as described with reference to Figures 5 and 6. The wheel motors of the rear wheels 4 are fastened to cylindrical tubes corresponding to the cylindrical tubes 55 of the front wheels 3, although no provision is made for steering the rear wheels.

The rear output shaft 10 of the engine 8 drives the front power take-off shaft 23 and the rear power take-off shaft through the clutch 15 and the changespeed gear 16 and through the gear wheel transmission 17 and the auxiliary shafts 20 and 27. The drive to the two power take-off shafts can be connected or disconnected by means of the clutch 15. The clutch 19 makes it possible either to drive the rear power take-off shaft alone or to drive both the power take off shafts. The speed of rotation of the front and rear power take-off shafts is proportional to that of the output shaft of the driving engine 8, but the changespeed gear enables the speed ratio to be selected at will. If the change-speed mechanism 16 is a hydrostatic device, the speeds of rotation of the power take-off shafts may be steplessly varied.

The travel speed of the tractor is variable by altering the fluid displacement of the pumps 12 and 13, for example, by means of adjustable swashplates in the pumps which are actuable from the cab 14.

Such swashplates may, if desired, be provided in the wheel motors.

By control of the change-speed mechanism 16, the speed of rotation of the two power take-off shafts can be adjusted to match the travel speed of the tractor so that a soil cultivating machine attached to the lifting device 28 and/or 46 attains an effective driving speed (for example near the cultivating tines of the attached machine) which approximately cor responds to the travelling speed of the tractor. In this way the soil cultivating machine can supply part of the propelling force of the tractor.

The rear lifting device 28 in the illustrated embodi ment is constructed in the form of a conventional three-point lifting device, but the illustrated con struction of the front lifting device 46 may also be used at the rear of the tractor. By actuating the hydraulic ram 40 the lifting device 46 comprising the relatively rigidly secured parts 32, 33, 34,35,36,43, 44 can be forcibly moved up or down. The hooks 43 and 44 serve to fasten the coupling points of a machine or a tool to be attached.

In orderto enable removal and replacement of the front wheels 3 and rear wheels 4 (if a lifting device such as the device 46 is also arranged at the rear) or in order to enable an auxiliary wheel to be mounted beside an existing wheel, the trestle 47 is mounted on the hooks 43 and 44. The pins 50 of the trestle 47 are then held in the hooks 44 and are prevented from escaping upwardly by the heavy latch bolts 45 which are fixed in the locking psition. The pin 49 of the trestle 47 is received in the hook 43 and prevents the trestle 47 from toppling about the common centreline of the pins 50. By retracting the piston rod of the cylinder 40, the lifting device is forcibly moved downwards so that it bears either directly or through the trestle 47 on the ground.Thus the ajacent wheels (in Figure 1 the front wheels 3) are lifted from the ground so that they can be removed, replaced or supplemented. The required force to be exerted by the ram 40 can be obtained by using, at a conventional hydraulic pressure, a large effective diameter of the cylinder or a high ratio between the effective cylinder diameter and the piston rod diameter. In the embodiment shown, in which the piston rod is retracted, the latter ratio applies. The trestle 47 may, of course, also be employed for repair work.

When the undersides of the beams 34 already bear on the ground in the position shown in Figure 1 (as stated above) the lifting device itself can lift the adjacent wheels from the ground without the need for using the trestle 47.

Mounting an auxiliary wheel on the outboard side of the wheel disc 58 is performed as follows, reference being made to Figure 5.

Before the wheel is fitted, the stub shaft 65 and the bosses 70, secured by the bolts 71, protrude outwardly beyond the wheel disc 58. The stub shaft 65 is positioned, by means of the lifting device 46 in the manner described above, at a desired height above the ground, and then the hub 62 of the wheel to be mounted is slipped onto the stub shaft 65, whose outwardly tapering shape facilitates this operation.

Typically, the wheel will weigh about 150 kgs, but it need not be lifted off the ground. With the wheel hub 62 supported on the stub shaft 65, the wheel is then turned to bring the openings in the plate 64 into alignment with bosses 70. The wheel can then be pushed home towards the carrier 58, the outwardly slightly tapering bosses 70 entering the correspondingly shaped openings in the plate 64. Radial displacement of the wheel is not necessary because the hub 62 fits closely around the cyindrical part of the stub shaft 65 located near the flange 66 so that the bosses then are at the correct distance from the hub 62. When the bosses 70 are in the openings in the plate 64, it is necessary only to insert the bolt 75 to secure the whole wheel.The screwthreaded end 80 is screwed into the tapped hole 74, after which the cylindrical part 79 intimately fits in the cylindrical chamber 73 of the stub shaft 65. When the bolt 75 is inserted the conical part 78 serves as a locating part to guide the cylindrical part 77 and bears on the cylindrical inner wall of the hub 62. This insertion is carried out by means of the wrench 82, the wail 87 surrounding the bolt head 76 and the central pin 88 of the wrench 82 facilitating the positioning of the wrench and centering it by engagement with the central hole 81 in the bolt 75.

When the wrench is unfolded, so that the lever part 91 is approximately in line with the part 89, considerable leverage can be exerted on the hub bolt for loosening the bolt. As soon as the bolt has turned by one turn, the wrench can be folded into the position indicated by broken lines in Figure 5 so that the bolt can be very rapidly unscrewed from the hub (when removing a wheel) or screwed into the hub (when mounting a wheel). For tightening, the bolt the lever part 91 is brought into line with the part 89 in order to exert a high torque on the bolt, as when initially loosening the bolt. Since the wrench has a central pin and the bolt has a central opening, the bolt will not drop from the wrench after being removed from the hub. Since the lever part 91 is longer than the part 89 a lever arm is formed in the folded state of the lever as indicated by broken lines in FigureS, the length of which arm is equal to the difference between the two lengths.

After fitting or removing a wheel, the wrench 82 is removed and arranged as a tool in the tractor.

Whilst various features of the tractor that have been described, and that are illustrated in the drawings, will be set forth in the following claims as inventive features, it is to be noted that the invention is not necessarily limited to these features and that it encompasses all of the features that have been described both individually and in various combinations.

Claims (51)

1. A motorvehicle comprising a driving engine for powering ground wheels and a lifting device which is actuable by means of a hydraulic system and which can be forcibly moved downwards.

2. A motor vehicle as claimed in claim 1, in which the lifting device is pivotable about a single pivotal axis extending transversely of the intended direction of operative travel of the vehicle.

3. A motor vehicle as claimed in claim 2, in which, as viewed on plan, the pivotal axis is located on the side of the rotary axis of adjacent wheels of the vehicle which is opposite the coupling points of the lifting device.

4. A motor vehicle as claimed in claim 2 or 3, in which the pivotal axis is situated approximately at the same level as the top side of adjacent wheels of the vehicle.

5. A motor vehicle as claimed in any one of the preceding claims, in which the lifting device carries a trestle, which can bear on the ground.

6. A motor vehicle as claimed in claim 5, in which the trestle can be released from the lifting device.

7. A motor vehicle as claimed in claim 5 or 6, in which the trestle can be fastened to the coupling points of the lifting device.

8. A motor vehicle as claimed in any one of the preceding claims, in which the lifting device itself can bear on the ground.

9. A motor vehicle as claimed in any one of the preceding claims, in which the lifting device is a three-point lifting device.

10. A motor vehicle as claimed in any one of the preceding claims, in which, as viewed from the side, the lifting device has a generally curved shape.

11. A motor vehicle as claimed in any one of the preceding claims, in which the lifting device can be turned by means of a double-acting hydraulic ram.

12. A motor vehicle as claimed in any one of the preceding claims, in which the lifting device can be pressed down to the ground by at least one suitably proportioned hydraulic ram and in which ground wheels can be moved upwardly from the ground.

13. A motor vehicle as claimed in claim 11 or 12, in which the hydraulic ram is mounted at one end near a powr take-off shaft of the tractor.

14. A motor vehicle as claimed in claim 13, in which the power take-off shaft can be driven with different speeds of rotation by means of a changespeed device actuable from a driver's seat of the vehicle.

15. A motor vehicle as claimed in claim 14, in which the speed of rotation of the power take-off shaft is steplessly variable.

16. A motor vehicle as claimed in claim 14 or 15, in which the speed of rotation of the power take-off shaft can be adjusted from the driver's seat in a manner such that the effective speed of a soil cultivating machine attached to the vehicle is approximately equal to the travel speed of the vehicle.

17. A motor vehicle as claimed in any one ofthe preceding claims, in which at least one wheel is drivable by means of a hydraulic motor.

18. A motor vehicle as claimed in claim 17, in which a supply duct of the motor of a steerable wheel extends through a hollow king pin of the wheel and a return duct of the motor is disposed outside the king pin.

19. A motor vehicle as claimed in claim 18, in which the centreline of the supply duct coincides with that of the king pin.

20. A motorvehicle as claimed in anyone ofthe preceding claims, in which at least one wheel of the tractor is mounted to a stub shaft having a tapered end in which a tapped hole is provided.

21. A motor vehicle as claimed in claim 20, in which the tapped hole communicates with a cylindrical chamber in which fits a first cylindrical part of a fastening bolt of the wheel.

22. A motor vehicle as claimed in claim 21, in which the bolt has a second cylindrical part having a larger diameter than the first cylindrical part.

23. A motor vehicle as claimed in claim 22, in which the second cylindrical part fits in a tubular hub of the wheel.

24. A motor vehicle as claimed in claim 22 or 23, in which the head of the bolt is in contact with the second cylindrical part and projects all around beyond the second cylindrical part.

25. A motor vehicle as claimed in claim 24, in which the head of the bolt bears on an end face of the wheel hub.

26. A motor vehicle as claimed in claim 24 or 25, in which a screwthreaded shank provided at the end of the first cylindrical part away from the head and the second cylindrical part is screwed into the tapped hole.

27. A motor vehicle as claimed in any one of claims 21 to 26, in which the screwthreaded shank and the two cylindrical parts are coaxial with the stub shaft.

28. A motor vehicle as claimed in any one of claims 24 to 27, in which the head of the bolt has a central cavity.

29. A motor vehicle as claimed in any one of claims 21 to 28, in which the wheel is secured solely by the bolt.

30. A motor vehicle as claimed in claim 29, in which the wheel is rotationally fixed by one or more bosses.

31. A motor vehicle as claimed in claim 30, in which the wheel comprises a plate lying at right angles to the rotary axis of the wheel, the plate being fastened to the hub and being provided, at a distance from the hub, with at least one opening having a conical edge.

32. A motor vehicle as claimed in claim 31, in which the boss has a periphery which matches the edge of the opening.

33. A motor vehicle as claimed in any one of the preceding claims, in which all of the wheels of the vehicle have the same diameter which is about 135 cms.

34. A motor vehicle as claimed in any one of the preceding claims, in which the width of a pneumatic tyre of a tractor wheel is about 60 cms.

35. A motor vehicle as claimed in any one of the preceding claims, in which the driving engine has a power of about 60 KW.

36. A bolt having screwthreaded shank and a polygonal head, the head having a cavity for receiving part of a wrench by means of which the bolt can be turned.

37. A bolt as claimed in claim 36, in which the bolt has two cylindrical parts of different diameter disposed between the screwthreaded shank and the head.

38. A bolt as claimed in claim 37, in which a conical part adjoins the cylindrical part nearerthe head, this conical part being situated between the two cylindrical parts.

39. A bolt as claimed in claim 38, in which the screwthreaded shank, the two cylindrical parts, the conical part and the cavity are coaxial with each other.

40. A wrench for turning a bolt, the wrench having a olygonal wall and a central pin for fitting into a central part of the bolt.

41. A wrench as claimed in claim 40, in which the pin is surrounded by the wall and partly protrudes beyond the end face of the wall.

42. Awrench for turning a bolt, the wrench comprising a lever which can be folded to provide a larger and a smaller lever arm.

43. A wrench as claimed in claim 42, in which the lever is provided with a pivotal shaft which crosses the centreline of the operative head of the wrench at a distance.

44. A wrench as claimed in claim 42 or 43, in which a first handle is provided in line with the operative head of the wrench and at right angles to at least part of the lever.

45. A wrench as claimed in any one of claims 42 to 44, in which a second handle is pivotally connected with the outer lever part.

46. A wrench as claimed in claim 45, in which the second handle is pivotable about a second pivotal shaft extending parallel to the first pivotable shaft.

47. A wrench as claimed in any one of claims 42 to 46, in which the length of the outer lever part exceeds that of the inner lever part.

48. A motor vehicle as claimed in any one of claims 1 to 35, which is an agricultural tractor.

49. An agricultural tractor substantially as described herein with reference to, and as shown in the accompanying drawings.

50. A bolt substantially as described herein with reference to, and as shown in, Figures 5 and 6 of the accompanying drawings.

51. A wrench substantially as described herein with reference to, and as shown in, Figures 5 and 6 of the accompanying drawings.