The object of the invention is a transfer device that grips a double wheel, and which is intended to move an aircraft or other device equipped with double wheels on a base, and which transfer device includes a fork-shaped frame and pairs of rollers located on each of the prongs of the fork and devices to revolve the rollers and devices to compress them, both pairs of rollers being able to be placed from the side in front and behind the wheel of the device to be moved, and in which by means of rotating the rollers pressed against the wheel, the wheel of the device to be moved is made to revolve and the entire device to move.

Here a double wheel also means the adjacent wheels of the wheels of a bogie. The transfer device is mainly intended to move passenger aircraft at an airport. Here the compression and friction rollers also mean sets of rollers formed by more than one roller close together. A track or similar may be used on top of the set of rollers.

The structure of a transfer device can be considerably lightened when the rotational force is transferred to the aircraft's own wheel from the operating wheels or friction rollers that form part of the transfer device. An entirely universably applicable light transfer device's construction is shown in Finnish Patent Application FI 833275 (partly corresponding to W085/01265) . This requires no contact with the bogie of the aircraft in order to press the drive wheel against the wheel of the aircraft. The compression is achieved by means of the mutual movement of the pressure rollers, connected by an intermediate device, which are placed round the wheel of the aircraft.

A transfer device, which grips a double wheel, especially the front undercarriage bogie of an aircraft, is shown in U.S. patent publication 3,005,510. In it the neighbouring bogie wheels are used by means of two friction tracks, which are wedged between consecutive bogie wheels. In the known transfer

devices that grip double wheels the problem is that they can only be used with some types of aircraft. The dimensions of double wheels is different aircraft vary greatly. The smallest wheel sizes have a diameter of only 80 cm, whereas the largest diameter is as large as 2 m. An even greater problem than this is the wide range of dimensions between the wheels. In the smallest aircraft the distance between the tracks of the wheels is only 80 cm and in the largest 1400 cm. In this case a transfer device with a U-shaped frame must be made very wide and the lateral adjustment of the rollers very long. Transfer devices with a U-frame are shown in, among others, WO publications 87/06542 (PCT/FI87/53) .

The intention of this invention is to achieve a transfer device that rotates double wheels and which can be used with double and bogie wheels of varying size. The characteristics of the invention appear in the accompanying Patent Claim 1. The main principle of the invention is to carry out the lateral movement of the rollers either entirely of partly by moves the side forks in their entirety by means of parallelogram arms. Firstly, these keep the forks always in one direction and secondly, the torque created by the compression is led through them to the rear frame, where the forces cancel1 out. In the application shown in Patent Claim 5 only the adjustment required by the double wheels of different aircraft is carried out by the lateral movement of the parallelogram arms. In this case the overall width of the device remains small. The change in direction of the front rollers and the compression movement can be achieved in some known manner.

The forms of implemention shown in Patent Claims 3 and 7 are, more easily dealt with than the former, because in them the forks always turn in the same relation to the frame part. By means of the methods according to Patent Claim 6 the problem of the locking of the front support wheels can be solved. These have to turn freely during the transfer of an aircraft, but should be locked when the transfer device itself is moved, when steering takes place with the rear wheels.

The form of application shown in Patent Claim 6 makes possible the maximum pushing and pulling ability. The optimum locations of the carrier wheels are at different places in pushing and pulling.

In what follows the invention is illustrated with the aid of examples by reference to the accompanying illustrations, which show various forms of application of the invention.

Figure 1 shows the transfer device being driven round a double wheel, seen from in front Figure 2 shows the transfer device seen from the side Figures 3 and 4 show the transfer device gripping a double wheel

Figure 5 shows the use of the transfer device in connection with large double wheels Figure 6 shows one other transfer device seen from above • Figure 7 shows the transfer device in Fibure 6 seen from the side

The transfer devices shown in Figures 1...7 are intended to move an aircraft 1 on an airfield. In the figures the aircraft 1 is shown by only a part of the landing gear and the wheels 8. The transfer device moves to the aircraft pulled by its front support wheels 12 and in addition to those its principal components are the friction rollers 3 and 4, which are supported by the front forks, their compression and rotation equipment, the power device unit, the parallelogram arms 5, the rear frame 7 and the steering device that turns the rear wheel 28. The front forks 2 of the frame are attached to the rear frame 7 by means of the parallelogram arms 5, which can be moved by means of the operating device 13. Two slides 9 are attached to each of the front forks 2, and the rollers 3 , 4 and their motors and gear-boxes are attached to them. The slides 9 are connected to one another by means of another operating device 10, by means of which they are the rollers 3,

4 with them can be moved longitudinally and the rollers be compressed against the wheel 8 of the aircraft 1.

Hydraulic cylinders are used as the operating devices 10 and 13.

In Figure 1 the transfer device has ben driven around the double wheel 6 of an aircraft 1. The movement of the transfer device itself also takes place by means of friction transmission. If there is no aircraft wheel between the rollers 3, A , the auxilliary friction rollers 11 on the opposite side of the slides 9 meet the support wheels 12, which can be rotated in a corresponding manner.

Figure 2 shows the principle of the lateral movement of the forks 2. The forks 2 include two tubes 8 and 14, along which the slides 9 move. -The support wheel 12 is supported by these tubes by means of the turning arm 13. This arm 16 can be turned and at the same time the support wheel 12 raised and lowered with the aid of a third operating device. When the support wheel 12 has been raised, the fork 2 descends onto the lateral auxialliary support wheel 15. After this the rollers 3 and 4 are pushed to their extreme positions and the forks 2 are drawn inwards, in order that the rollers are brought into line with the track of the double wheels 6, Figure 3. The support wheel 12 is lowered to the ground and the rollers 3 and 4 are raised along with the fork 2. Finally the rollers 3 and 4 are drawn inwards to grip the wheel 6 and its rotation begins, Figure 4. When the forks are being drawn open or closed it may happen that the second fork 2 does not begin to move at all. In that case the rollers 3, 5 of the fork 2 that has begun to move are brought round the corresponding wheel 6 and pressed tight, after which the rollers of the other fork 2 can also be brought into place. When moving in the opposite direction the support wheels 12 can be separately lowered to the ground.

The transfer device in Figure 5 is shown in connection with a large-wheeled bogie. In the case of the wheels of a bogie two

wheels next to each other form a double wheel, which is gripped by the transfer device. By turning the parallelogram arms 5 quite large differences in the sizes of double wheels can be dealt with. The movements of the parallelogram arms 5 can be synchronized by means of a transverse reaction rod 17.

The entire transfer device can form an extra implement to some suitable vehicle, for example a tractor, in which case it requires no separate power source. The vehicle is then technically regarded as being part of the transfer device.

In the transfer device shown in Figures 6 and 7 the lateral movement of the parallelogram arms is much less than in the former, this is because the front friction rollers 4 turn forwards and the lateral movement only adapts the transfer device to different kinds of bogies. In Figure 6 one fork is shown in partial cross-section, so that the mechanism used to move the front friction roller 4 is visible.

Here too the transfer device is formed princiaplly of a rear frame 7 and the forks 2, attached to it by means of the parallelogram arms 5, to which the rollers are attached. Freely turning wheels 12 are located at the front of the forks 2, but however these are locked in place when the transfer device is being moved by the front friction roller 4 (shown by broken lines) , which presses on a counter member 27 on the turning axle of the wheels 12. The transfer device then moves powered by the rotation device that belongs to the rear wheel 28.

The compression movement of the front friction rollers 4 takes place by means of turning the parallelogram arms 22 and 23. The compression is controlled with the aid of a hydraulic cylinder 25. The friction roller 4 is turned to the front in such a way that the triangular plate 24 carried by the rear parallelogram arm 23 is turned forwards when the entire parallelogram is turned through about 85° . The turning of this roller as such may be effected by also using other previously known mechanisms.

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When moving an aircraft the front support wheels 12 turn freely, which makes it possible for the aircraft to be turned sharply. In this the forks 2 are principally constructed round the tube 17 in such a way that suituble opening to permit the movements of the friction rollers 4 are made in the tube, and the tube 17 itself forms a support frame for the attachment of various components. Here all four friction rollers are equipped with a hydraulic motor-reduction gear unit 21.

In this the lateral movement of the fork parts 2 is carried out with the aid of a threaded rod 18, which pulls or pushes the counter members 20 in the fork parts. The rotation of the screw 18 takes place by means of a hydraulic rotation device 19, which is supported laterally from the rear frame 7. Two advantages are gained here through the use of screw members. Firstly the movement of both forks is synchronized and secondly the screw transmission is self-retaining.