Pressure regulator valve

A pressure regulator valve arrangement may include first and second regulator valves for closing a fluid passage in the event of over-pressure. The valve members may each have pressure ports for sensing the pressure, and the ports may be located downstream of the valve members to minimize interaction between the valves.

This invention relates to fuel regulators such as those used in the reception coupling of a refuelling drogue for use in air-to-air refuelling.

Such a reception coupling is attached to a fuel supply hose at one end, and has a valve at the other end which is pushed open upon insertion of a refuelling probe. This allows fuel to flow from the refuelling hose through a passage in the coupling into the probe to refuel the aircraft. Fuel is pumped to the hose under pressure so as to achieve a high flow rate. Should the delivery path become blocked downstream of the probe valve, for example because the following aircraft has completed refuelling, the fuel pressure in the reception coupling may become very high. For safety reasons, it is necessary to provide a pressure regulator valve to shut off the fuel supply at such high pressures. Regulations require that two such regulator valves should be provided in case of failure of one of the regulators.

Commonly the two regulator valves have been provided at spaced apart positions in the passage through the reception coupling. For example, one regulator valve is commonly provided at the inlet or upstream end of the reception coupling adjacent the hose, and the other regulator valve is provided downstream at the outlet adjacent the probe valve. This arrangement can lead to interaction between the two pressure regulators wherein the downstream regulator may start to close, blocking the flow of fuel in response to an increase in downstream pressure. Closing the downstream regulator will lead to an increase in upstream pressure, causing the upstream regulator to close. This will have the effect of reducing the downstream pressure, causing the downstream regulator to open. This behaviour can be cyclic, causing fluctuations in regulated pressure and system wear.

A means of eliminating this behaviour is to include a venturi in the fuel passage at a position where the upstream regulator senses the fuel pressure. This causes the total pressure sensed by the upstream regulator to increase as flow rate increases, thereby separating the regulated pressure of the regulators as flow increases, preventing the problem.

However, a disadvantage of this arrangement is that if the downstream pressure regulator fails, then the upstream regulator will regulate to an incorrect pressure at high flow rates. In addition, the inefficiency of the venturi contributes to a significant overall pressure drop for the reception coupling. This is undesirable as it increases the pressure requirement from the fuel pump. For example, it is common for-prior art regulators to produce a pressure drop of around 40 psi at a flow rate of 500 imperial gallons per minute. Since a pressure of around 50 psi is required at the probe valve, it is necessary to produce 90 psi at the inlet of the reception coupling.

Accordingly, there is a need to provide a regulator arrangement which alleviates these disadvantages.

According to the present invention there is provided a pressure regulator valve arrangement comprising a passage for fluid having an inlet and an outlet, and a valve for opening the outlet to deliver the fluid, the passage including first and second pressure regulator valves, the regulator valves each comprising a pressure port for sensing pressure in the passage, and a valve member arranged to close the passage in response to pressure at the pressure port exceeding a predetermined pressure, in which the pressure ports are both arranged downstream of both of the valve members.

Providing the pressure ports downstream of both of the valve members reduces the tendency for the valves to interact with each other, since the pressure between them is not sensed or used to operate the upstream regulator. Hence it is unnecessary to provide a venturi in the passage, such that the passage may be made larger in cross section. Thus the arrangement may be used in a reception coupling with a consequent low pressure loss across the reception coupling.

The delivery passage is commonly annular in shape, and the valves may be sleeve valves, with valve members being correspondingly annular in shape. The valve members may be closely adjacent or concentrically arranged. This further serves to prevent interaction between the regulators.

Referring toFIG. 1, the reception coupling2includes a fuel passage4having an inlet6for connecting to a fuel hose and an outlet8for communicating with the probe of a following aircraft to be refuelled. A probe valve member10is arranged at the outlet to be operable by the refuelling probe upon insertion into an opening12of the reception coupling2. The valve member10is normally closed, and is pushed axially towards the inlet end6of the reception coupling into an open position by insertion of a probe. In this position, fuel may flow from the inlet end6through the passage4past the valve member10into the probe chamber12. The probe has apertures for allowing the fuel to flow into the probe which communicates with the aircraft fuel tanks to be filled.

In order to prevent damage to the probe and following aircraft when refuelling is complete, it is necessary for the fuel flow to be stopped should the pressure in the passage4exceed a predetermined maximum. Therefore a regulator valve is required automatically to close the passage4upon such pressure being reached. In addition, safety regulations state that there should be two such valves in case one of the valves should fail. According to the prior arrangement, a first regulator valve14is provided adjacent the probe valve10. The passage4communicates with a first valve chamber16of the valve14. Fuel pressure in the chamber16acts to push a first regulator piston18axially towards the inlet end of the coupling. A first valve sleeve member20attached to the piston thus moves axially towards the inlet. The passage4is curved such that the sleeve20crosses the passage4upon axial movement and abuts the seal21on the outside wall22of the coupling to close the passage4. Thus the supply of fuel to the probe chamber12is stopped.

A second regulator valve24positioned adjacent the inlet end of the coupling works in a similar manner. Pressure in the passage4acts to push to the second regulator valve member26axially towards the inlet6to cross a curve in the passage4and block the flow of fluid.

In order to control the flow of fuel through this arrangement and to prevent interaction as described above, it has been found to be necessary to include a venturi28in the passage between the positions of the two regulator valves. However, this causes an undesirably large pressure drop between the inlet and the outlet of the passage4. Also this arrangement tends not to be entirely successful in preventing the two valves from interacting with each other, whereby the first regulator valve tends to close prematurely at high flow rates.

Referring now toFIG. 2, according to the present invention a comparatively wide annular fuel passage30through the reception coupling alleviates the problem of a high pressure loss by the absence of obstructions such as the venturi which was necessary with the prior art arrangement.

Referring also toFIGS. 3-6, the passage30is in fluid communication via a pressure port31with a valve chamber32. The valve chamber32includes actuators in the form of first and second pairs of valve pistons34,36. The first pair of valve pistons34are housed within a first pair of piston bores38in a centrally located regulator valve body40. The pistons34are connected by a first cross member42to a first valve sealing member44. The first valve member44is in the form of a thin plate in the shape of an axially extending ring or sleeve. The first valve member44extends around the circumference of the valve body40adjacent the inlet end of the passage30, upstream of the pressure port31.

The second pair of valve pistons36are housed within a second pair of piston bores46in the valve body40. The second pair of piston bores46are aligned along a diameter of the valve body40which is perpendicular to the diameter along which the first pair of piston bores38is arranged, as can be seen fromFIG. 7. The second pair of pistons36are connected by a short piston rod48to a second cross member50. The second cross member50has axially extending arms52at each end thereof attached to a second regulator valve member54. The second valve member54has a similar shape to the first valve member44and is arranged concentrically around the first valve member44adjacent the passage30and upstream of the pressure port31.

The pistons34,36are spring biased towards the outlet end of the regulator by springs (not shown) arranged in the piston bores. In use, when the fluid pressure in the valve chamber32exceeds a pre-determined maximum pressure, it acts on the two pairs of pistons34,36to push them in the axial direction towards the inlet end of the passage30. Movement of the pistons towards the inlet causes the first and second valve members44,54to extend across the passage30to the outside wall56of the regulator. This seals the passage30from fuel being provided from the refuelling hose.

Since the two regulator valve members are operated by fluid pressure in the same chamber downstream of the both valve members, and act substantially together in adjacent positions, they do not interact negatively with each other. Furthermore, since it is no longer necessary to provide a venturi in the fuel passage, the pressure drop from the inlet to the outlet end of the passage30may be significantly reduced.

Referring toFIGS. 8 and 9, an alternative configuration is shown, in which the fuel passage60is in fluid communication with first and second valve chambers62,63via a fuel pressure sensing ports61, and an open end65of the valve body70respectively. The first valve chamber62includes a first valve piston64. The first valve piston64is housed within the first piston bore68of the regulator valve body70. The piston64is connected by a first cross member72to a first valve sealing member or regulator sleeve74. The first regulator sleeve74is in the form of a thin plate, and extends around the circumference of the valve body70adjacent the inlet end of the passage60.

The second valve piston66is housed within a second piston bore76in the valve body70. The second piston66is connected by a piston rod78to a second cross member80. The second cross member80has axially extending arms82at each end thereof attached to a second regulator sleeve84. The second regulator sleeve84has a similar shape to the first regulator sleeve74and is arranged concentrically around the first regulator sleeve74adjacent the passage60. The regulator valve member assemblies are also shown inFIGS. 10 and 11.

The pistons64,66are spring biased towards the outlet end of the regulator by springs88and90arranged in the piston bores68,76. In use, when fluid pressure in the valve chambers62,63exceeds a pre-determined maximum pressure, the two pistons64,66are pushed in the axial direction towards the inlet end of the passage60. Movement of the pistons towards the inlet causes the first and second regulator sleeves74,84to extend across the passage60into contact with first and second seals92,93in the outside wall86of the regulator. This seals the passage60from fuel being provided from the refuelling hose.

Referring in particular toFIG. 9, the fuel pressure sensing port61is one of a plurality of ports spaced around the circumference of the valve body70, ensuring the pressure within the valve chamber62is substantially similar to that of the fuel passage60. The pressure is regulated or measured with respect to atmospheric pressure, and this is provided on the air side of the pistons64and66by the vent ports94and96respectively. These each pass through a valve body support98which mounts the valve body70to the regulator outside wall86. The vent ports and valve body support shown are one of a plurality, typically4, equally spaced around the regulator.

Since the two regulator sleeves74,84are effectively operated by upstream fluid pressure in the passage30, and act together in adjacent positions, they do not interact negatively with each other. Again, since it is no longer necessary to provide a venturi in the fuel passage, the pressure drop from the inlet to the outlet end of the passage60may be significantly reduced.

Reference is now made toFIG. 12to show the independence of the regulator valves further. This shows the arrangement ofFIG. 8, with both regulator valves responding to high pressure in passage60by partially closing. For detailed design and manufacturing reasons, the regulators may not close by precisely the same amount, and inFIG. 12the first or inner regulator sleeve74is shown slightly more closed than the second or outer regulator sleeve84. The passage60is therefore constricted at100, where the valve members cross the passage, reducing the pressure to the required regulated pressure downstream thereof, with a sensed higher pressure upstream thereof. In this situation, movement of the outer regulator sleeve84does not cause a change in pressures and will therefore not cause the inner regulator sleeve74to move. Conversely, although movement in the inner sleeve will cause a change in pressures, and therefore the outer regulator sleeve84will move, its movement will not influence the pressure. The same rationale applies if the position is reversed, and the outer regulator sleeve84is more closed.

Therefore the second valve is acting as a ‘safety’ valve, with its operation not influencing the regulated pressure unless the first valve should fail.