TECHNICAL FIELD This invention relates to an hydraulic device for use in multifunction exercise machines, which allows reversal of the direction of resistance and variation of the degree of resistance to movement by simple adjustment.

BACKGROUND ART Hydraulic devices that are double acting, that is, that allow flow through in a forward and reverse direction are known. Also known are devices which allow such forward and reverse flows to be independently regulated. However such devices have required complex and expensive machining in their production.

DISCLOSURE OF THE INVENTION The present invention therefore provides a double acting hydraulic valve for an exercise machine comprising:

- first and second manifolds, each having an inlet/outlet port;

- a passage, extending between the first and second manifolds;

- first and second valve members, each located in a respective manifold and independently moveable under high pressure at its port, relative to pressure at the other port, to allow flow from its respective port to the passage;

- first and second non-return valves, each associated with a respective manifold and arranged such that when there is flow from one port to the passage, the non-return valve associated with the other manifold allows flow from the passage to the other port and prevents backflow into the passage; wherein each non-return valve is positioned in its respective manifold.

Preferably the double acting hydraulic valve includes in each manifold, a stationary valve body with first and second longitudinal channels extending through it to provide a communication path between the respective port and the

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passage, and a non-return valve member. It is preferred that the first channel is associated with a valve member to selectively allow flow from its respective port to the passage, and that the second channel is associated with the non-return valve member to selectively allow flow from the passage to its respective port.

It is also preferred that the first channel is a cylindrical bore extending through the stationary valve body. In one embodiment, the valve member is a cylindrical spigot of diameter corresponding to the diameter of the cylindrical bore. Also the first channel can be oriented parallel to its respective manifold with each stationary valve body including a transverse aperture which opens between its first channel and the passage. The valve member can slidingly operate within the first channel to open and close the aperture.

In one form of the present invention, the pressure required for flow between each port and the passage is independently regulated by biasing means. In this form the biasing means may be a spring which biases a spigot to close the aperture. The spring resistive force may also be adjustable by a rotatable attenuator acting on the spring.

In a further preferred form of the present invention, the second channel is adjacent to and parallel with the first channel and extends between its respective port and the passage. The non-return valve member can selectively seal the port end of the second channel. Furthermore, the non-return valve member may be releasably retained on the stationary valve body by a spring. Preferably the second channel is a plurality of conduits extending through the stationary valve body. It is also preferred that the non-return valve member is annular, permitting flow through the first channel at all times.

In one embodiment of the present invention, the passage communicates with a reservoir. Bleed galleys may be provided in the valve to bleed pressure from behind each valve member into the reservoir.

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BRIEF DESCRIPTION OF THE DRAWINGS A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is an exploded sectional plan of the valve;

Figure 2 is an elevational view of the assembled valve;

Figure 3 is a plan sectional view of the assembled valve taken on the line III-III of Figure 2; Figure 4 depicts various views of a part of the valve of Figures 1 to 3.

BEST MODE FOR CARRYING OUT THE INVENTION Referring to Figure 1, the valve 1 comprises a block 2 with manifolds 3 and 3 '. Reservoir 4 interconnects the manifolds through passage 5.

The valve further comprises valve members 6 and 6', non-return valve members 7 and 7', valve bodies 8 and 8' , inlet/outlet ports 9 and 9' and rotatable attenuators 10 and 10A Referring to Figures 2 and 3, the valve is depicted as assembled. The valve comprises two identical halves. The following description of Figures 2 and 3 therefore refers to one half only.

Valve member 6 is a spigot attached to and biased by spring 33.

Stationary valve body 8 comprises a first channel 13 in the form of a cylindrical bore through the valve body and a second channel 15 in the form of a plurality of cylindrical conduits extending through the periphery of the valve body. The stationary valve body also comprises an aperture 17, which communicates with the passage 5. The valve member 6 slidingly operates within cylindrical bore 13. The valve body is best depicted in Figure 4.

Non-return valve member 7 is in the form of a valve seat and stem 11 which is removeably held against stationary valve body 8 by spring 19. An opening 20 communicates with the cylindrical bore 21 through stem 11 which extends

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through the non-return valve member 7.

Inlet/outlet port 9 is located at one end of manifold

3. The inlet/outlet comprises locking portion 25 and conduit connector 26. Washer 27 seals the manifold. A bore 28 extends through the inlet/outlet port and spring 19 is partially retained in this bore.

Rotatable attenuator 10 is an adjustment knob 30 containing a plurality of apertures 40 on a pitch circle.

The apertures 40 sequentially receive a spring-loaded plunger 31 biased by a spring 34, upon rotation of the adjustment knob 30. Each adjustment knob 30 is also provided with a stop pin 32 which inhibits rotation beyond one full revolution. The adjustment knob seals the manifold end opposite the inlet/outlet end via sealing ring 35. The adjustment knob 30 threadably engages the block 2 and bears against respective valve member 6 through spring

33.

A bleed galley 45 is provided for effective valve operation. This galley 45 bleeds pressure from behind the valve member 6 into reservoir 4. If this passage is not provided, pressure can build up behind the valve member and impede its opening movement.

In use, inlet/outlet ports 9 and 9' are connected to a fluid circuit and the double acting hydraulic valve contains an hydraulic fluid. Typically in series with the fluid circuit is an exercise machine.

Upon high pressure being applied to for example, fluid in the first inlet/outlet port 9, this pressure is transferred by the fluid located in bore 28 and cylindrical bore 21 onto the valve member 6.

As can be seen from Figure 3, non-return valve member

7 is sitting in contact with stationary valve body 8. This prevents the flow of fluid through conduits 15.

When the pressure is sufficiently high, valve member 6 is urged along cylindrical bore 13, compressing spring 33, until aperture 17 is exposed to fluid communication with cylindrical bore 13. Fluid can then pass from the

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inlet/outlet port 9 into passage 5.

Under normal operating conditions, the orifice size at the interconnection of cylindrical bore 13 and aperture

17 is relatively small. The valve member 6 remains at a substantially constant open position. This provides a specific resistance to the flow of fluid through the stationary valve body.

As valve member 6 is biased by spring 33, it therefore functions as a pressure regulating valve. The pressure required to open the cylindrical bore 13 to fluid communication with the passage 5 can be regulated by rotatable attenuator 10 which adjusts the resistive force in spring 33. The valve member 6 can also function as a non-return valve. After hydraulic fluid has passed into the passage 5 and reservoir 4, it passes through the plurality of conduits

15' that extend through the stationary valve body 8'.

Simultaneously, the fluid is blocked by the other valve member 6' (the lefthand side valve member of Figure 3) from passing up cylindrical bore 13A

The hydraulic fluid flowing through conduits 15' impinges upon non-return valve member 7' causing it to lift and compress spring 19' . The fluid then passes through opening 20' in non-return valve member 7', through cylindrical bore 21' and out of the valve through bore 28A

The reverse will happen if fluid pressure is applied to inlet/outlet 8'. Inlet/outlet 8 would then become a suction line.

Since the adjustment knobs 30 and 30' can be individually adjusted, the resistive pressures in the manifolds 3 and 3' can be set to correspond with flow rates which will offer the required resistance to, for example, a user of a hydraulic exercise machine. Thus different forces can be provided in alternative directions when the valve is connected to, for example the vane of a hydraulic pump in an exercise machine. This aspect of the valve is valuable in a wide range of exercises, including for example the

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strengthening of the biceps and triceps of the arms.

The valve can be designed to be accurately tuned for different exercise functions with each adjustment knob admitting independent minimum and maximum pressure adjustment within one 360° revolution for different muscle groups being exercised. The valve and associated pressure reading dials can be mounted on a valve bracket which can be independently located for easy access by for example a user of the exercise machine. It will be clear to one skilled in the art that the configuration of the bodies in the valve can be varied without departing from the invention. For example the valve bodies could be lineally opposed on opposite sides of the reservoir and the bleed galley achieved by a central bore through the pressure regulating and non-return valve. The fluid flowing through the valve could also be a gas, for example air.

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