The present invention relates to a closed device for hydraulic power transmission in which the pressure of a hydraulic fluid is controlled at one or more points of a control system assisted by fluid pressure actuated members in which changes of the fluid pressure actuate one or more operative members of the control system. The device of the invention is intended mainly for applications where it is desirable to transfer power from one point to another, e.g. for brake systems on vehicles. It is in particular applicable for power transmission through walls, which separate for example gas and fluid from the environment, as for example, control valves in pipings and excess flow valves for the automatic closing of a tube for a gas or a fluid, for example in a position where the pipe has ruptured so that the contents can stream out into the environment and cause damage. TECHNICAL BACKGROUND

The use of hydraulics for power transmission has given easy controlled, flexible and still strong and robust results even with small devices. When making a comparison with mechanical power transmission the devices are not so heavy and bulky and the passability in small spaces and through walls is,much better. When comparing hydraulic systems to electric systems the passability is certainly ery good for the last mentioned process, but is often more expensive and detailed for corresponding powers and further when using hydraulics much better controllability with rather small devices obtained. The disadvantages when using hydraulic power transmission is mainly the leakage of hydraulic fluid, which demands supervision and filling. The leakage also causes environment inconveniences such as the danger of fire, slipping and odour. As a consequence hydraulics often demand overhauling of the system for tightening and exchange of worn out gaskets and diaphragms. To protect against contamination in the hydraulic fluid from water and worn out particles is difficult as well as oxidation of the fluid by the surrounding oxygen in the air. A complete closed hydraulic system without direct contact with the environment will often solve most of the problems.

Control valves and shut-off valves are generally provided with a control device in the form of a hand control, which is mounted directly on the valve spindle. A device for remote control operation can be entirely mechanical and for example, be formed of one or more shafts, which are connected to the valve spindle via a cardan joint or be electronic and be formed of an electric motor, which via a gear reduction is connected to the valve spindle, and the motor is controlled, for example, by electrical signals which, via a rel y closes the current to the motor. The remote control is actuated for example by the valve being located in a place which cannot be reached without great difficulty inter alia on pipes, located high above the ground and in closed spaces, as for example cisterns. It has also proven difficult to arrange remote controls with lead-ins in for example cisterns in which a fluid or a gas is under pressure. Quick closing valves to a certain extent have an outstanding position in the applications, where the present invention is advantageous. Quick closing can either be done manually or automatically, e.g. when damage has occurred and it is desired to immediately stop the gas or liquid flow. A complete mechanical excess flow valve is described in Swedish Patent 7413120 and comprises a valve body on a valve push rod mounted in a tube and movable in the longitudinal direction of the tube towards a ring-shaped seat. The push rod is in connection with a spring on the outside of the tube via a link mechanism, where one of the link arms extends through the wall of the tube via a sealing box. When there is a pipe rupture at a point downstream of the excess flow valves in the flow direction, the flow rate in the tube increases and a low pressure arises on the underside of the valve body. When the low pressure causes a force on the val e body, which via the link mechanism comprises the spring, the valve body is displaced towards the seat, and the tube is closed. The size of the spring force is adjustable and thus the excess flow valve can be closed at different flow rates.

A disadvantage with the excess flow valve is that the tightening box in the tube wall as time goes becomes worn and begins to leak. Another disadvantage is that there is no easy way to change the adjustment in the valve using remote control. A further disadvantage is that the valve cannot be opened without great difficulty if it has

been closed by mistake. Then the pressure in front of the valve has to be lowered, e.g. by using a special unloading valve before the excess flow valve can be opened again. In the same way another conventional excess flow valve works, which is not adjustable from the outside of the tube but is equipped with a spring, which directly works on the valve body inside the tube. SUMMARY

The present invention provides a closed hydraulic power transmission in which there is no risk for leakage and wear, which can especially be used to transfer a force from one point to another.

According to the present invention there is provided a hydraulic power transmission device adapted to form part of a control system at which the pressure of a hydraulic fluid is controlled at one or more points of the control system by fluid pressure actuated members and in which changes of the fluid pressure actuate one or more operative members of the control system which device comprises a plurality of tubular expandable bellows, which at one end are closed and at the other end are connected to each other by tubes or hoses, the closed space so obtained being filled with hydraulic fluid. Thus according to the present invention there is provided a hydraulic power transmission in which a hydraulic fluid is controlled at one or more points in a control system by using a fluid pressure actuated member and in which alteration of the fluid pressure actuates one or more of the operative members in the control system, in which the fluid pressure actuated as well as the operative members are tubular expanding bellows made of, for example, metal or rubber.

The present invention will be further illustrated by way of the accompanying drawings, in which:-

Figure 1 is a schematic section through a device according to one embodiment of the present invention;

Figure 2 is a longitudinal section through an excess flow valve; and

Figure 3 is a longitudinal section through a remote control device to the excess flow valve according to Figure 2. CLOSER DESCRIPTION OF THE INVENTION

Referring to Figure 1, the hydraulic power transmission device 1, comprises two or more tubular, expanding bellows 2, which at one URE

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end, the front end 3, are closed and at the other end, the rear end are connected to each other by tubes or hoses 5. The closed space is filled with a hydraulic fluid 6. The bellows 2, are manufactured for example of metal or rubber and the connecting tubes or hoses 5 should be made of materials, which do not change appreciably in volume, when the pressure rises in the device.

By pressing the bellows 2, in axial direction by an extended pressing member 7, the volume thereof is decreased. This causes some or all the other bellows 2, in the device to be extended to obtain the corresponding volume. The extension takes place in the axial direction which then affects other movement members in the receiving system 8. A condition for good operation is that the bellows 2, are operated in radial direction so that the movement of the bellows 2, are concentrated in the axial direction. Therefore a guide bushing 9, is usually disposed around the bellows 2, in which the bellows 2, are movable axially.

In the same way the rear part 4, of the bellows 2, to which the tubes 5 are connected is equipped with a fastening device 10, which is fixedly attached to the object to which the front part 3, of the bellows 2, moves in relation to. EXAMPLE

Referring to Figure 2, the excess flow valve comprises a cylindrical valve tube 11, having two end flanges 12, by which the valve can be connected to a tube system having substantially the same tube dimensions as the tube 11. A conical seat 13, is mounted at the one end of the valve tube 11, and extends around the inside of the valve tube 11. A conical valve body 15, adapted to fit against the seat 13, by the tightening ring 16, is mounted at the one end of a push bar 17, which bar is axially adjustable in a steering 14, attached on the seat 13, and supported by fins 19. The push bar 17, at its other end is fixedly attached to expansion bellows 2, made of steel and having a steering guide bushing 9, which surrounds the expansion bellows 2, and in which tubular bellows 2, are axially movable. The other end of the expansion bellows 2, are fixedly attached on a tube 5, which extends from the guide bushing 9, via a tube bend out through the wall of the valve tube 11, to which the tube 5, is welded. The guide bushing 9, also surrounds a part of the tube

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5, and is adjustable along the tube 5, which in turn is fixedly supported by a fastening device 10, which extends from the tube 5, to the inner surface of the valve tube 11, through which the axial forces in the tube 5, are taken up when there is movement in the expansion bellows 2. The tube 5, is via a reinforced hose 18, in connection with a similar expansion bellows 2, outside the valve tube 11.

The expansion bellows 2, outside the valve tube 11, is connected with a spring control device comprising a pressure limitation device 20, as shown in Fig. 3, which can be used to compress the expansion bellows 2. The pressure in the tube 5, can be read on a manometer 21, which is in connection therewith via a manometer tube 22. The manometer tube 22, may be closed by a shut-off valve 23.

The excess flow valve is adjusted so. that it closes at a certain flow rate of the valve tube 11, by adjusting a corresponding pressure on the manometer 21, by using the pressure limitation device 20. If the flow rate should increase in the valve tube 11, for example after a tube rupture, an increasing depression occurs at the rear of the valve body 15, seen from the flow direction, as shown by an arrow on Figure 2. The pressure on the valve body 15, in direction towards the expansion bellows 2, increases, and the power in the push rod 17, compresses the expansion bellows 2, so that the valve body 15 moves towards the seat 13 to effect closure. When the pipe rupture is repaired, the valve body 15, can again be influenced to open using the pressure limitation device 20. When having varying the flow rate in the valve tube 11, the manometer 21, shows a varying pressure in the tube 5. The reading on the manometer scale will thereby be proportional to the flow rate in the valve tube 11. The manometer 21, can be graduated in flow rate magnitudes. In an alternative embodiment of the invention, the manometer 21, can be connected to a registered member which integrates the flow in time and thus the excess flow valve also serves as a flow meter.

The pressure limitation device 20, includes in the example an air-operated membrane and thus this device can also be remotely controlled. At a quick cut-off air pressure is arranged on the side of the membrane, which provides for a compression of the pressure limitation spring in the pressure limitation device 20, while the air

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pressure is arranged on the opposite side of the membrane at the opening of the valve.