WO1990011932A1

WO1990011932A1 - A transmission system for a transfer device gripping a double wheel

Info

Publication number: WO1990011932A1
Application number: PCT/FI1990/000081
Authority: WO
Inventors: Matti Sinkkonen
Original assignee: Tana-Jyrä Ky
Priority date: 1989-03-31
Filing date: 1990-03-28
Publication date: 1990-10-18
Also published as: FI891543A0; FI81533C; FI81533B

Abstract

The object of the invention is a transmission system of a transfer device gripping a double wheel, which transfer device is intended to move an aircraft (1) or other wheeled device over a base, which transfer device includes at least two friction rollers (3, 4) and motors (5) to drive them, i.e. one for each ground wheel (6) of the device (1) to be moved, and compression devices (2) to create the compression to press the friction roller (3, 4) against the ground wheel, and which system includes a power device and transmission devices to feed the operating power to the motors. The intention of the invention is to create a transmission for a transfer device that creates a steady push irrespective of a poor location of the pushing point, which is the main undercarriage. The system according to the invention includes devices to feed the operating power separately and independently of each other to each of the motors (5) driving the ground wheel (6).

Description

A Transmission System for a Transfer Device gripping a Double Wheel

The object of the invention is a transmission system for a transfer device gripping a double wheel, which transfer device is intended to move an aircraft or other device equipped with double wheels over a base, and which transfer device includes at least two friction rollers and motors to rotate them, that is, one for each wheel of the device to be moved, a friction roller to be pressed against this, and compression devices to create the pressure, and the system also includes a power device and power transmission devices to feed the driving force to the motors. Here the term double wheel also means the neighbouring wheels of a bogie.

The construction of a transfer device can be considerably lightened if the driving force is transferred to the wheel of the aircraft from a drive wheel or friction roller forming part of the transfer device. A construction for a transfer device that is universally applicable is shown in the Finnish Patent Application FI 833275 (partly corresponding to WO85/01265) . This does not require any contact with the undercarriage of the aircraft in order to press the drive wheel against the ground wheel. The compression is achieved by means of the mutual movement of compression rollers connected by an intermediate member.

In its most common form the intermediate member pulls the two compression rollers connected by. it towards one another, when they are pressed against the ground wheel between them. At least one of the compressed wheels is now a friction roller or drive wheel which transmits rotational force to the ground wheel of the aircraft. Other transfer devices belonging to the area of the invention are shown in Finnish Patent Applications FI861714, FI870313, and FI870710. In practice nearly all aircraft are equipped with either double wheels or even larger bogie wheels. It is therefore natural to make the transfer device such that it grips a double wheel, because then the force acting on the large tyre can be reduced. Transfer devices equipped with a so-called self-wedging friction roller are not advantageous in relation to this, because they stress the ground wheel of the aircraft considerably more than a transfer device that grips both wheels with two or more friction rollers. In any event this invention can also be applied for example to a transfer device in accordance with application FI870710, which shows a self-wedging transfer device that grips a double wheel, and in which both friction rollers are equipped with their own motor and gearbox.

A transfer device that grips double wheels, especially the nose ground wheels, is shown in US patent publication 3,005,510. In this neighbouring bogie wheels are driven by means of two friction tracks, which are wedged between the two in-line bogie wheels. The hydraulic transmission includes both a direction switch valve and a flow distribution valve, by means of which the flow going to the right and left side hydraulic motors can be adjusted.^" The adjustment takes place by means of two restriction"points that are connected to one another, so that when the one decreases in size the other increases. By means of this the nose bogie wheels can be made to turn by restricting the flow going to the hydraulic motors on one side at the same time as the restriction on the other side is lessened.

This invention is especially related to such transfer devices in which the transfer takes place only from one of the main undercarriage bogies. This in itself is something new, because in accordance with the state of the art the drive has always been symmetrical. Asymmetrical drive gives the aircraft a turning force, which normally is of no consequence as the aircraft can be steered in the desired direction by means of the nose wheels. Problems may appear in certain special circumstances. In terms of friction conditions an icy and snowy airfield in winter is totally different from a dry asphalt surface in summer. In addition a strong side wind may increase the force turning the aircraft. Practical experiments have shown that moving an empty aircraft on. a very slushy airfield is extremely difficult. One tyre of the double wheel may rise by itself to carry in which case the other is able to rotate freely. Another phenomenon of the same kind appears on an icy airfield when one of the wheels being driven begins to slip on the ice. All the hydraulic motors that are connected in the same circuit lose their feed pressure, because the flow leaks through the motors that are driving the slipping wheel. Another serious disturbance arises if the nose wheels begin to slide laterally. Twisting then takes place around the undercarriage beside that being pushed as it remains in place.

The intention of this invention is to achieve a transmission system for a transfer device driving double wheels that will create a stable push, even though the driving point used is the main undercarriage that is located in a difficult position to the side of the centre line of the aircraft. The characteristics of the invention appear in the accompanying Patent Claim 1. The main principle of the invention is to synchronize the operation of the various motors and corresponding friction rollers. This mainly means that the friction rollers are locked to the same phase and speed of rotation. If one of the wheels begins to slip, the friction roller of the wheel beside it continues to drive. This same locking also limits side slip in the nose wheels, because the neighbouring ground wheels have to turn at different rotational speeds.

The form of application in accordance with Patent Claim 2 is the simplest solution to the problem of creating locking in a hydraulic transmission. The distribution valves must absolutely be pressure compensated so that the flow is not able to escape through the motor of the wheel that is rotating freely. A more reliable locking operation that the above is achieved by implementing the system in accordance with Patent Claim 3, in which case the synchronization of the motors as realized through the operating components is considerably more precise than the former. The turning of the device to be moved while it is being moved is made possible by implementing the system in accordance with Patent Claim 4. This is especially important in connection with a transfer device equipped with two pumps and entirely separate circuits, but it is also useful in connection with hydraulic circuits created with flow distribution valves. The invention can also be adapted to operation with electric transmission. The control of electric motors is most advantageously based on frequency transformer technology and the entire system can be based on diesel-electric transmission.

The form of application in accordance with Patent Claim 7 makes it.possible for the turning moment created by the one-sided push of the new method to be cancelled. In addition to the pushing force a turning force is also developed by the transfer device, which cancels either entirely or in part the turning force given to the aircraft by the pushing force. A braking device is most easily created in a hydraulic system equipped with two pumps by setting the pumps asynchronously,, i.e. so that the output of the one pump is set to be less than that of the other.

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

Figure 1 shows the use of the transfer device in moving an aircraft Figure 2 shows the transfer device in the operating position seen from above Figure 3 shows the hydraulic transmission system of a transfer device in accordance with Figure 2 as a schematic diagram Figure 4 shows a flow distribution valve in cross-section Figure 5 shows another hydraulic transmission system as a schematic diagram

In the situation shown in Figure 1 the transfer device 20 is pushing aircraft 1 from the right-hand main undercarriage 21, in which there is a double wheel. The push causes a turning moment around the left-hand undercarriage, which moment is cancelled by the nose wheel 22 of the aircraft. Figure 1 includes an arrow showing the pushing force of the transfer device and a broken line showing the counter moment that arises in one form of application, which cancels the force turning the aircraft. During the transfer the aircraft 1 is steered by turning the nose wheel 22 in the desired direction.

In Figure 2 only the undercarriage and ground wheels 6 of the aircraft 1 are shown. The transfer device moves on its own wheels and in addition to them the principal components are friction rollers 3 and 4, the hydraulic motors 5 that drive them together with gearboxes and power unit, which includes a hydraulic pump unit driven by a diesel motor.

Both ground wheels 6 have their own friction rollers 3 and 4, both of which are driven by hydraulic motor 5. The front friction motors 4 are arranged, in a known manner, to be turned to the side, so that the transfer device can move around the ground wheels 6 of the aircraft 1. The support of the front roller 4 is arranged by means of sliding member 7, which is moved by means of hydraulic cylinder 7 and which in its extreme position is also allowed to turn. Figure 2 shows the same stage in pushing as Figure 1.

The principal components of the hydraulic transmission system in Figure 3 are the pump unit driven by diesel motor 8, the hydraulic motors 5, and pressure compensated flow distribution valves 10. The pump unit includes a high pressure pump 9 and its feed pump and lubricating oil system. Changes in direction and gearing take place by altering the stroke capacity of the high pressure pump 8 and the direction of the flow. The motors 5 are divided into two groups by means of the flow distribution valves 10. One group drives the right-hand and the other the left-hand ground wheel 6. The flow distribution valves 10 really only operate in one direction, in the reverse direction they permit a free flow. On account of this two of them are required, one for each direction.

Figure 4 shows the construction of a pressure-compensated flow distribution valve 10 in detail. The pipe coming from pump 9 is connected to connection 11 and the pipes coming from the motors 5 are connected to connections 12. The principal directions of flow are marked with arrows in Figure 4. Pressure compensation is arranged by the spindle 13, which is arranged to be moved. Reverse flow takes place with practically no obstacle through valves 14. In the system shown in Figure 3 one of the steady flow valvfes 10 divides the flow precisely into two parts and the other collects flows to pump 9.

More precise synchronization than the above is achieved by the two pump system shown in Figure 5. In this both of the aforementioned motor groups use their own pump 15. The speed of revolution of both is the same and the adjustment levers are combined to be turned synchronously in normal conditions. In good conditions valve 19 is kept open, so that there is no locking between the right and left-hand ground wheels. If the airfield is icy or in windy weather valve 19 is closed, when the synchronous operation of the motors 5 tries to keep the aircraft straight. By setting the adjustment levers of the aforementioned pumps 15 to different positions one begins to have a greater output than the other. The motors 5 in the circuit with the smaller flow begin to have a braking effect. If the braking circuit connects in the situation in Figure 1, i.e. in the situation of the transfer device pushing from the right-hand side, to the right-hand ground . wheel 6, the turning moment created by the pushing force created by the transfer device 20 cancels the moment. This kind of moment cancellation is necessary for example when moving relatively long types of aircraft on icy airfields and in windy weather.

Claims

Patent Claims

1. A transmission system for a transfer device gripping a double wheel, which transfer device is intended for moving an aircraft (1) or other wheeled device on a base, which transfer device includes at least two friction rollers (3, 4) and motors (5J to drive them, i.e. one for each ground wheel (6) of the device (1) to be moved, and a friction roller (3, 4) to be pressed against the ground wheel, compression devices (2) to create the aforementioned compression, and which system a power device (8) and transmission devices to feed the motive power to the motors, characterized in that the system includes devices (10) to feed operating power separately and essentially independently of each other to each of the motors (5) that drive the ground wheel (6) .

2. A hydraulic transmission system for a transfer device in accordance with Patent Claim 1, which includes one pump (9), which drives the aforesaid hydraulic motors (5) , characterized in that the system includes at least one pressure-compensated flow distribution valve (10) , which divides the volumetric flow fed by the pump (9) into two parts, to drive each ground wheel (6) separately in such a way that the use of the corresponding hydraulic motor (5) is not essentially dependent on the load of the motor (5) corresponding to the neighbouring ground wheel (6).

3. A hydraulic transmission system for a transfer device in accordance with Patent Claim 1, characterized in that the system includes two pumps (15) synchronously connected to the same power device, for example a diesel motor (8) , one of which drives the motors (5) driving the left-hand ground wheel (6) and correspondingly the other the motors driving the right-hand ground wheel (6) .

4. A hydraulic transmission system for a transfer device in accordance with Patent Claims 2 or 3, characterized in that the system includes separate pipe runs (18), equipped with valves (19) , which connect the high pressure sides and return sides of the hydraulic circuits (16, 17).

5. An electrical transmission system for a transfer device in accordance with Patent Claim 1, characterized in that the system includes a source of electricity, for example a battery, and at least two motors and current supply devices to operate them.

6. A transmission system in accordance with Patent Claims 2, 3, 4, or 5, which transmission system includes at least two compression rollers to be placed on opposite sides of each ground wheel (6) to be driven and pressing against it, at least one of which, most advantageously all, are friction rollers (3, 4) to drive the ground wheel (6) , characterized in that the motors (5) are arranged in two groups with respect to the operating power feed, one of which drives one or more left-hand and the other correspondingly right-hand ground wheels (6) .

7. A transmission system for a transfer device in accordance with one of Patent Claims 1 - 6, which transfer device is intended to push an aircraft especially from a double ground wheel or bogie of the main undercarriage, characterized in that the system includes devices to brake at least the outer wheel of one pair of wheels at the same time as at least one of the inner wheels is driven.