The object of the invention is a device equipped with wheels for moving a wheeled vehicle on a base, the vehicle being for example a motor vehicle, a trailer, or an aircraft, and the base being, for example the ground, a road, an airfield, the floor of a building, a loading bay, the platform of a truck or railway wagon, the device including at least two pressure rollers attached to one another by an intermediate member, which can be moved to fit around the wheels of the vehicle, or one pressure roller to be placed between the two wheels of a bogie, and a pressure apparatus to press the rollers against the wheel of the vehicle to be moved, and in which at least one of the pressure rollers is a drive roller, which is driven by a motor thus moving the vehicle.

Usually tractors are used to move aircraft around an airfield, and these must be heavily constructed to give them sufficient traction.

As the size of aircraft increases so ever larger tractors are required with a heavy construction, large wheels, efficient brakes, and massive axles. In order to reduce the deadweight of the device for moving air¬ craft a system is used in which the device lifts the wheel of the air- craft completely off the ground, in which case the weight coming onto the wheel is also transferred completely to the wheels of the device. Devices of this kind are shown for example in the German application publications DE 3327628 and DE 3014767-

The weight of the transfer device can be substantially decreased if the turning force is transferred to the wheel of the aircraft from the drive wheel on the device. This presupposes that the drive wheel is pressed agaisnt the aircraft wheel with a force that is usually a few percent of the weight coming onto the wheel. The most usual solution in connexion with a transfer device of this kind is that the transfer device is attachedby means of a suitable member to the bogie of the aircraft or to the ends of the axle in order to achieve a counterforce to the pressure. A transfer device of this kind cannot be used to move any kind of aircraft whatever, for there must be corresponding members in the aircraft bogie in order to make the attachement of the transfer device possible. A construction for a light completely general purpose transfer device in shown in the Finnish patent application FI 833275 (partially corresponding to W085/01265). This requires no contact on

the aircraft bogie in order to press the drive roller against the wheel. The pressure is achieved by means of the mutual movement of two pressure rollers placed round the aircraft wheel and connected by an intermediate member. In the most general form the intermediate member pulls the two pressure rollers held by it together so that they are pressed against the wheel between them. At least one of the pressure roller is now a drive roller, which trans ers its turning force to the aircraft wheel.

It is the intention of this invention to achieve a transfer device, in which there is a new simple method of arranging the pressing of the drive roller against the aircraft wheel without fixed contact to the bogie or corresponding part of the frame. The characteristics of the invention can be seen in the accompanying Patent Claim 1. The main principle of the invention is to achieve the pressure referred to by the common move¬ ment or twisting of rollers a set distance apart, which is easier to achieve than their mutual movement. The counterforce is applied to the ground through the wheels of the transfer device. There may also be crawler tracks in place of rollers as such. In place of the wheel of the vehicle to be moved there may also be a group of wheels. The fixed dis¬ tance of the pressure and drive rollers must naturally be less than the diameter of the wheel of the vehicle to be moved or than the length of the corresponding group of wheels. When moving a vehicle with wheels in a bogie one drive roller is sufficient according to the invention, is this is wedged between the bogie wheels by lifting it by supporting it against the frame of the transfer device. What is then substantive is that the counterforce caused by the pressure is directed to the ground. By forming the drive and pressure roller in accordance with patent Claim the fact that the rollers remain stably round the wheel of the vehicle to be moved is achieved.

In what follows the invention is illustrated with the aid of examples by referring to the accompanying illustrations, in which

Figure 1 shows the transfer device being brought round a pair of wheels of an aircraft, seen from above Figure 2 shows the situation in Figure 1 seen from the side Figure 3 shows the transfer device in the operating position seen from above

Figure 4 shows the situation in Figure 3 seen from the side in part cross-section

Figure 5 shows one of the other operations of the transfer device Figure 6 shows the transfer device according to Figure 5 seen from above in part cross-section The transfer devices shown in Figures 1 -6 is intended to move air- craft 1 on airfield 2. In the illustrations only part of the landing gear and wheels 6 of aircraft 1 are shown. The transfer device is moved on wheels 11 and its principal components are the drive and pressure rollers 4, 8 attached to the frame 5 and the intermediate member 7. Each of the wheels 6 have their own pressure and drive rollers. The rear pressure rollers 8 can be turned to the side in which case the transfer device forms a U-fork, which is pushed around the pair of wheels of the aircraft, Figures 1 and 2. The movement of the transfer device takes place from the drawbar 10 which is jointed to the carrierifork>>_.6 oflii he steerable front wheel 11. The front end of the frame 5 is also jointed to this. Cylinder 9 is installed on top of the carrier fork 16 and the piston 17 of the cylinder is jointed to the bracket 18 attached to the front end of the frame 5-

The intermediate member 7 that keeps the drive and pressure rollers 4, 8 at a fixed distance is here formed as a part of frame 5 in such a way that it forms a telescopic part of the side beam of frame $ _> in which the length is varied by means of the U-pin 12. The variation is required on account of the various wheel diameters found in different aircraft. The turning of the rear pressure roller 8 is carried out by the turnable support arm 13, which is connected to the frame 5 by means of a joint 14- The locking of arm 13 into the operating position takes place by means of the U-pin 15. In addition to the aforementioned adjust¬ ment in length adjustment of the lateral spacing of the parallel pressure rollers 8 is required in accordance with the width of the pair of wheels of the aircraft. This is realized in such a way that the carrier forks of the drive and pressure rollers 4» 8 on one side are attached to slide sleeves 24 and 22, which can move to a limited extent on one of the turnable arms 13 and correspondingly on the guide formed by the transverse frame beam 25, Figure 3»

The transfer device in accordance with Figures 1 and 2 is pushed around the wheels 6 of the aircraft, after which the turnable arms 13 are turned to the crosswise position and locked by pin 15- The front pressure rollers 8 also operate as drive rollers 4 with the aid of the hydraulic motors 3«

The transfer of the turning force from the drive roller 4 to the wheel 6 now requires that these are pressed together. This is carried out by lifting the front part of the frame 5 by means of cylinder 9 when the drive roller 4 moves into sufficient contact with wheel 6, Figures 3 and 4« The rear pressure roller 8 is essential in order to achieve the counter- force. Drive roller turns by means of the hydraulic motor 3 _> which is permanently attached to it, and which is fed from power unit 26. This contains for example an internal combustion motor and a hydraulic pump. The hydraulic connections between the pump and the motor 3 are not shown. The transfer device also includes a control unit (not shown), which is most advantageously connected with the drawbar 10.

The drive and pressure rollers 4, 8 are formed in such a way that they automatically centre themselves on the aircraft wheel 6. The diameters of the edges of these rollers 4 ₃ 8 are greater than the diameter of their centres when lateral movement caused by some deviance cause the pressure to increase, which returns the roller to the central position.

The form of application in Figures 5 and 6 is closest to the transfer device that grasps bogie wheels shown in Figures 19 and 20 of publication W085/01265. In the-transfer device in accordance with the invention only one pressure roller 8 is required, however, this forming drive wheel 4 together with hydraulic motor 3« The frame 27 of the transfer device includes a vertical guide 29, along which sleeve 29 is fitted to move. Drive roller4 is thus free to move in a vertical direction by being at¬ tached to sleeve 29 and controlled by cylinder 30. When drive roller 4 is in the lowest position the entire transfer device can be brought side¬ ways around the bogie wheels 6 , this being made possible, by the turnable wheels 11, and the pressure roller 8 brought between the wheels 6. The situation shown in Figures 5 and 6 is achieved from this by raising the pressure roller 4 into contact with the wheels 6. The power unit 26 and control units can be the same as aforementioned. By turning the drive wheel 4 the wheels 6 are turned and thus the aircraft itself 1 is moved. The transfer device then moves in the direction determined by the bogie wheels 6. What is essential in this is that that counterforce caused by the pressure is led to the ground through the wheels of the transfer device. When the desired move has been made the pressure roller 8 is lowered, and then the transfer device can be pulled to the side.

The invention can be applied in many ways that deviated from what is stated above, for example as a similar variation to that presented in the aforementioned publication W085/01205« However, according tot his inven¬ tion the drive wheels are not pressed against the aircraft wheels with the aid of mutual movement, by by common movement or twisitng and by supporting the lift on the device's own frame and from that onto the ground. The number of wheels, the number of drive and pressure rollers, and the source of power of the motors of the device can be varied in different applications. In a transfer device in accordance with this invention, however, at least two bearing rollers or crawler tracks, which receive the counterforce caused by the. pressure, are required. The motor can also be located inside the drive wheels. Battery operated electric motors and correspondingly pressure reservoirs and compressed-air motors can be used for motive power. The length adjustment of the transfer device and the turning of the rear wheels can also be carried out with the aid of suitable operating equipment.