Such a chassis is preferably applicable for a portal tractor, but is also applicable in other cross-country vehicles, where it is preferred to maintain a given orientation of chassis, irrespective of roughness or slope in the ground and where a four-point weight distribution is desired as well.

Portal tractors, which are built up as three-wheeled vehicles with stationary members so they follow the slope of the ground, are known. These are intended to be used with row crops with growth in the shape of trees and bushes. Such crops will grow verti- cally irrespective of slope of the ground. When the known portal tractors are used on sloping ground, they will run against trees as these grow vertically. The three-wheeled construction makes it difficult to drive on lying ground, as the centre of gravity must be kept within the triangle of the three wheels; also, optimal working conditions are not present between a tractor driving on sloping ground and trees or other growths growing vertically.

A chassis, with a construction where the wheels are individually adjustable, is also known. These are, however, technically complicated and expensive constructions.

It is the purpose of the present invention to show a chassis of the type mentioned in the beginning, which makes is possible to swing an upper part of the chassis sideways as well as back and forth in the direction of travel for a vehicle, for example a portal tractor, in such a way that a chassis member, for example a portal for supporting tools, can be adjusted to a preferred orientation, preferably vertically, and which at the same time makes a weight distribution on the wheels of the vehicle possible.

According to the present invention this is obtained with a chassis which is peculiar in that it includes two lower side members which at each end are equipped with one or more wheels or caterpillar tracks, that each lower side member between its front end and rear end include a first bearing with an axis of rotation substantially transversely of the longitudinal direction of the lower side member, that an upper side member is connected to each of these first bearings, and that each upper side member includes two other bearings at an upwards facing part at different distances from the lower side member and with axes of rotation oriented in the longitudinal direction of the lower side members, and that two parallel cross members are connected in pairs to these other bearings for forming a parallelogram connection between the upper side mem- bers and the cross members.

A chassis according to the invention, for example for a cross-country portal tractor, can be provided with four driving and/or steering wheels or caterpillar track. The chas- sis is built up so there is a lower side member between a front wheel and a rear wheel or caterpillar track, and there is such a lower side member at each side of the vehicle.

It is most common that the wheels are oriented for driving in the longitudinal direction of the side members ; but it is possible to have the wheels oriented for driving trans- versely to the lower longitudinal direction of the side members.

On the side member there is a horizontal bearing with the axis transversely to the di- rection of travel, at this bearing an upper side member is mounted, which preferably is a vertical member forming one side of the portal. This makes swinging back and forth in the direction of travel possible.

At the top in the upper side member there are two bearings, which preferably are hori- zontal bearings with their axis of rotation oriented in the longitudinal direction of the lower side member, i. e. with an orientation longitudinally of the direction of travel.

The opposite side of the chassis is built up in the same way, with lower side member and upper side member, and at an upwardly facing part of the other side members two cross members are disposed, forming a bottom and a top in an articulated parallelo-

gram. The two bearings at the top at each of the upper side members create corners in the articulated parallelogram formed between the upper side members and the cross members. This makes swinging back and forth transversely to direction of driving possible.

According to the invention, a portal tractor with a chassis may advantageously be used for maintenance of Christmas trees and other row cultures on even or broken ground as well as uneven area where other portal tractors cannot run.

A portal tractor according to the invention with a four-point chassis is advantageous by having four-point weight distribution and a regulation of the tilting of the portal in a construction with a technically simple construction based on application of two mu- tually connected side members, instead of an independent and individual suspension and regulation of each wheel.

The centre of gravity is not so difficult to keep within the four wheels. By means of the structuring of the portal's points of support and the way in which longitudinally adjustable mechanisms, preferably in the shape of hydraulic cylinders, are mounted, it is possible to distribute the weight of the machine on to all four wheels.

If, for example, the right front wheel travels down into a hollow, then the difference between the right side member and the left side member will be distributed with half the deflection of the portal member through the connected hydraulic cylinders.

Portal tractors can be tilted sideways and back and forth in relation to side mem- bers/direction of travel. This makes it possible to adjust the portal on the tractor, so it is always vertical. On the portal member tool for the maintenance of for example Christmas trees and other row cultures can be mounted, this creates optimal working conditions for vertical working devices for vertical trees.

According to a specific embodiment, the chassis according to the invention is peculiar in that between a third bearing on a lower cross member and a fourth bearing on an

upper cross member, a first longitudinally adjustable mechanism is arranged for ex- tending or reducing the distance between the third and fourth bearing.

According to a further embodiment, the chassis is peculiar in that between a fifth bear- ing on the lower side member and a sixth bearing on an upper side member, another longitudinally adjustable mechanism is arranged that can extend or reduce the distance between the fifth and sixth bearing. This is particularly anticipated that a double- acting hydraulic cylinder is provided between each lower side member and corre- sponding upper side member.

With these embodiments it becomes possible to regulate the inclination of chassis member in sideways direction and in longitudinal direction, respectively, by extending or shortening it or the relevant mechanisms. This may occur as a result of a signal, for example from an electronic control signal which receives a reference signal from an electronic level, whereby the arrangement of the wheels on a sloping or uneven ground is detected.

According to a further embodiment, the chassis is peculiar in that the two cross mem- bers include a seventh bearing and an eighth bearing, respectively, each with an axis of rotation oriented in the longitudinal direction of the lower side members, that be- tween these a central member is arranged; that at one of the cross members a further cross member is arranged about a ninth bearing with an axis of rotation oriented in the longitudinal direction of the lower side members, that at the ends of the further cross member there are tenth bearings with an axis of rotation oriented in the longitudinal direction of the lower side members, that each lower side member comprise an elev- enth bearing at a distance from the first bearing and with an axis of rotation oriented transversely to the longitudinal direction of the lower side member, and that at each side a connecting bar is arranged between the tenth and eleventh bearing. With this construction it is possible to create a technically simple chassis where the weight dis- tribution is established by the further cross member swinging about the ninth bearing.

The central member can be used for carrying tools and/or for carrying a driver's cab for the vehicle.

Hereby, a chassis member, for example the central member or a side member, can be kept in a preferred orientation, for example vertical, simultaneously with a difference of height between the wheel/side members of the portal frame is distributed by a sim- ple swinging movement without the need to use longitudinally adjustable mechanisms between lower and upper side members.

If the connecting rods are longitudinally adjustable mechanisms that can extend or reduce the distance between the tenth and eleventh bearing, it is possible to regulate the inclination of the chassis member in longitudinal direction by extending or short- ening the mechanism.

The shape of a chassis according to the invention is flexible, as it is anticipated that the longitudinally adjustable mechanisms are selected among hydraulic, mechanic, electrically activating actuators, for example single-or double-acting hydraulic cylin- ders, racks or electrical linear actuators. According to the invention, a chassis can hereby be established for vehicles irrespective of whether these are electrically driven or driven by an internal combustion engine as power source in order to power a hy- draulic pump. Thus, it is anticipated that the height adjustment means include a power source such as hydraulic pump, electric motor or the like as well as means for adjust- ing the orientation of the chassis member and which is connected to a power source in order to activate it for establishing a preferred orientation of the chassis member.

Alternatively, it is possible to use a pneumatic cylinder as longitudinally adjustable mechanisms even though it is preferred to use mechanisms with the possibility of a stationary longitudinal adjustment.

According to a further embodiment, the chassis is peculiar in that in a supply circuit to the hydraulic cylinders, there is inserted a regulating valve or a mechanism with the same function which by means of control signals from the height adjustment means can extend or shorten the hydraulic cylinders. Hereby, it is possible to establish the preferred displacements of the mutual chassis members by means of a control signal,

preferably electronic, for setting of the valves, so the preferred extensions/reductions of the used hydraulic cylinders are obtained.

According to the invention, the chassis can have different shapes depending on the application intended. For use as a portal tractor it is anticipated that it forms a largely U-shaped, L-shaped or H-shaped portal for supporting the processing tools in a chassis member for treating vertically oriented crops irrespective of slope of the ground where the crops grow.

Alternatively, the chassis can be used in other vehicles as for example combined har- vesters, tractors or contracting machines where it is preferred to maintain part of the vehicle or the chassis in a desired well-defined orientation irrespective of the character or slope of the ground.

In the following, the invention will be explained in more detail with reference to the schematic drawing enclosed, where: Description of the drawing Fig. 1 shows a first embodiment of a chassis seen from the side on horizontal ground, Fig. 2 shows the chassis shown in Fig. 1, seen from the side on rising ground, Fig. 3 shows the chassis shown in Fig. 1, seen from the side on falling ground, Fig. 4 shows the chassis shown in Fig. 1, seen from the end on horizontal ground, Fig. 5 shows the chassis shown in Fig. 1, seen from the end on sloping ground, Fig. 6 shows the chassis shown in Fig. 1, seen obliquely from the side, Fig. 7 shows the chassis shown in Fig. 1, seen obliquely from the side, on uneven ground, Fig. 8 shows a further embodiment of a chassis as seen tilted from the side on a horizontal ground, Fig. 9 shows the chassis shown in Fig. 8, seen from the side on rising ground, Fig. 10 shows the chassis shown in Fig. 8, seen from the side on falling ground, Fig. 11 shows the chassis shown in Fig. 8, seen from the end on a horizontal ground,

Fig. 12 shows the chassis shown in Fig. 8, seen from the end on a falling ground, and Fig. 13 shows the chassis shown in Fig. 8, seen from the end on an uneven ground.

In Fig. 1 to Fig. 7, a first embodiment is shown for a chassis in schematic drafts, where some components such as motor, control system and mountings for tools are omitted. According to the invention, only the essential elements which are necessary for the understanding of the fundamental structure are illustrated.

The chassis is constructed with four-point weight distribution and tilt control. It is constructed with two lower side members 1,2 which at each end are supplied with supports in the shape of wheels, which can be steering/driving wheels. Alternatively, single wheels, or boogie wheels, or caterpillar tracks can be used. Between the two ends of each of the two side members, the first horizontal bearing is 7,8 with an axis of rotation oriented transversely to the longitudinal direction of the side members, which is placed in the plane of the paper in Fig. 1 to Fig. 3.

To each of these first bearings 7,8 a vertical upper side member 3,4 is connected. At an upper end of these upper side members 3,4 two parallel cross members 5,6 are mounted 5,6. These are connected through other horizontal and longitudinal bearings 9,10 and 11, 12, respectively. Between the two cross members 5,6 a first longitudinally adjustable mechanism in the shape of a double-acting hydraulic cylinder 13 is ar- ranged. This one is suspended in a third bearing 17 on the lower cross member 5, and a fourth bearing 18 on the upper cross member 6 and can extend or reduce the distance between these two bearings 17,18 by means of a regulating mechanism (not shown).

Between each lower side member 1,2, and the corresponding vertical upper side mem- ber 3,4 another longitudinally adjustable mechanism in the shape of a double-acting hydraulic cylinder 14,15 is disposed. By means of a regulating mechanism (not shown), the latter can extend or reduce the distance between a fifth bearing 19,21 on the lower side member and a sixth bearing 20,22 on the upper side member 3,4.

The two hydraulic cylinders 14,15 may, as shown in Fig. 6, be interconnected as communicating vessels in such a way that the A sides of the cylinders 14,15 are con- nected and the B sides are also connected. Between the A sides and the B sides is in- serted a regulation valve 23 or a mechanism with the same function, whereby it is pos- sible to extend or reduce the distance between the two bearings 19,21 and 20,22 on the lower and upper side members.

A portal member 16 is formed by the upper side members and the cross members, and this one can be swung back and forth. This happens by activating the regulation valve 23 inserted on the hydraulic cylinders 14,15 between the A sides and the B sides, so that the portal member 16 is displaced back and forth about the first bearings 7,8 as illustrated in Figs. 2 and 3.

The portal member 16 can be swung back and forth in transverse direction in relation to the longitudinal direction of the chassis. This happens by a parallelogram being formed, consisting of the uppermost parts of the upper side members 3,4 and the two cross members 5,6. The double-acting hydraulic cylinder 13 suspended between the two cross members is connected with a regulating valve 24 or a mechanism with the same function. By activating the regulation valve 24 by means of a regulation mecha- nism (not shown), it is possible to extend or reduce the distance between the two bear- ings 17,18 and thereby bring about an tilting as illustrated in Fig. 5.

The construction, where the hydraulic cylinders between the lower and upper side members 1,2 as well as 3,4 have connected side A on the hydraulic cylinder 14 with side A on the hydraulic cylinder 15, and side B on the hydraulic cylinder 14 with side B on the hydraulic cylinder 15, has the effect that the weight of the vehicle will be distributed between the four wheels at the ends of the two lower side members 1,2.

This effect is illustrated in Fig. 7.

In Fig. 8 to Fig. 13, another embodiment for a chassis is shown in schematic drafts, where some components are also omitted, so that only the basic components necessary

for the understanding of the fundamental construction according to the invention are illustrated.

This embodiment differs from the first embodiment in that the two cross members 5,6 comprise a seventh respectively eighth horizontal bearing 25,26 and that a central member 27 is suspended in those two bearings. Furthermore, a further cross member 28 is suspended about a ninth horizontal bearing 29 on one of the cross members 6.

At each end of the further cross member 28, there are tenth horizontal bearings 30,31 oriented in the longitudinal direction of the chassis. In each lower side member 1, 2 there are eleventh horizontal bearings 32,33 oriented transversely to the longitudinal direction of the chassis. Between the tenth and eleventh bearings a connecting rod 34,35 is arranged, which in the embodiment shown comprises a hydraulic cylinder (omitted in Figs. 11-13 for the sake of clarity). Alternatively, this could be a rod with a fixed length. In the figures, the cross member 6 and the further cross member 28 are shown with a certain length away from the upper side members 3,4. Alternatively, these can be constituted by quite small beams, so that a triangle is largely formed by the connecting rod 34,35, the lower part of the upper side members 3,4 and the part of the lower side members 1,2 extending between the bearings 7 and 32,33.

This second embodiment works in the same way as explained above. However, with this embodiment a weight distribution by the swinging of the further cross member 28 about the ninth bearing 29 will be achieved.