GB1600480A - Fluid throttles pressure reducers or flow controllers - Google Patents

Description

(54) IMPROVEMENTS RELATING TO FLUID THROTTLES, PRESSURE REDUCERS, OR PLOW CONTROLLERS (71) We, SOUTH WESTERN INDUS TRIAL RESEARCH LIMITED, of The University of Bath, Claverton Down, Bath, Avon, a British Company, do hereby declare this invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement: This invention relates to apparatus for use with fluids, especially liquids, and intended to act generally as a flow restrictor or controller, or as a pressure reducer. For convenience herein such devices are referred to in general as throttles.

The invention is concerned more particularly with throttles intended for use with high pressure flows at very high energy levels. For example, the invention may be applied to throttle valves used as restricters in conjunction with hydraulic pumps coupled as loads to engines under test. It is normal practice to provide restricter valves having adjustable centre pieces forming narrow annular restrictions of very small cross-section through which the liquid flows from the high pressure pump. Such restricter valves suffer from many disadvantages and in particular they are difficult to adjust, generate noise at an excessive level, and result in very high velocity liquid flow which may cause erosion of the surfaces.

It is an object of the invention accordingly to provide a fluid flow controller, restricter, throttle or pressure-reducer, comprising means providing a plurality of elongate passages, connectable between a common inlet and a common outlet and formed to provide a plurality of junctions or intersections between each other or with further passages, and means for adjusting the position of the passages relative to the inlet and/or outlet to vary the effective length of the passages.

Conveniently, the passages are formed between two contacting parts, for example on the.

surface of a cylindrical body located within a bore. For example, the passage may be formed by screw-threads, and in a particular preferred construction the passages are formed by intersecting screw-threads of opposite hand.

According to a preferred feature of the invention the outlets of the passages are inclined or oriented in different directions, to counteract at least partly the reaction forces generated by fluid issuing therefrom. Thus special advantages are obtained by forming intersecting screwthreads of opposite hand since this also provides outlet openings directed in the opposite direction about the axis of the screw.

Conveniently, the device may be combined with an element arranged to shut off the fluid flow completely at the limit of travel of an adjusting member.

The invention may be performed in various ways and one specific embodiment will now be described by way of example, with reference to the accompanying drawing, which is a simple diagrammatic section through a throttle valve according to the invention, designed to operate in conjunction with a hydraulic pump.

In this illustrated example the device comprises a main casing providing a cylindrical bore 10 having an inlet 11 and a number of outlet openings 12 communicating with a lateral manifold 13 leading to an exhaust outlet 14.

Within the bore 10 is mounted a cylindrical element 16 attached to a rod 17 which passes through one end of the casing where a seal 18 is provided, and is connected to an external shaft 20. On this shaft 17 is mounted a sub- sidiary pressure balancing piston 19, the effect of which is to counterbalance the axial force exerted on the element 16 by the high pressure fluid entering the inlet 11.

The cylindrical surface of this element 16 is provided with a double screw-thread, with the two threads 23, 24 extending in opposite directions and thus intersecting at numerous positions over the surface area. This provides at least two elongated restricter passages arranged in parallel in an electrical sense, that is to say each connected between the same high pressure inlet and the same low pressure exhaust. If each thread is a single start thread there will be two passages but clearly any number of passages may be provided by using a multi-start thread.

As compared with a conventional short length, small area throttle valve, these passages are of greatly increased length and also somewhat greater cross-sectional area. At each of the intersections the fluid flow is turned back by the fluid flow in the opposing passage, some turbulence and mixing occurs and energy is lost or converted to kinetic or thermal. In practice it is found that very little noise is generated and the gain in kinetic energy is not troublesome.

By moving the control rod 20 to shift the element 16 lengthwise in relation to the central outlet 12, the effective length of the throttle passages of the screw-thread can be varied and accurate fine adjustments can be made without the need to make microscopic small adjustments of the rod 20, due to the pitch of the screw-thread. Attached to the element 16 is a shut-off valve element 21 in the form of a solid flange which will close off the outlet 12 completely when the device is in its closed position as illustrated.

Since the exit openings from the intersecting threads are directed in opposite directions about the central axis of the screw, their reaction forces are opposed and there will be no resultant circumferential reaction tending to rotate the element 16. The element is also hydraulically balanced lengthwise as explained previously.

Instead of a double intersecting screw-thread, similar results may be achieved by other patterns of grooves. For example, the surface may be knurled and then machined down to form fine intersecting passages, or any pattern of passages, which intersect and/or form junctions, may be formed by etching, milling or in any other way.

WHAT WE CLAIM IS: - 1. A fluid flow controller, restricter, throttle or pressure-reducer, comprising means providing a plurality of elongate passages, connectable between a common inlet and a common outlet and formed to provide a plurality of junctions or intersections between each other or with further passages, and means- for adjusting the position of the passages relative to the inlet and/or outlet to vary the eflective length of the passages.

2. A fluid flow device according to claim 1, wherein the passages are formed between two contacting parts, for example on the surface of a cylindrical body located within a bore.

3. A device according to claim 2, in which the passages are formed by screw threads.

4. A device according to claim 3, in which the passages are formed by intersecting screw threads of opposite hand.

5. A device according to any of the preceding claims in which the outlets of the passages are inclined or oriented in different directions, to counteract at least partly the reaction forces generated by fluid issuing therefrom.

6. A fluid flow controller, restricter, throttle or pressure-reducer substantially as described with reference to the accompanying drawing.

7. A hydraulic loading system for an hydraulic pump, including a fluid flow controller, restricter, throttle or pressure-reducer as defined in any of the preceding claims.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. length, small area throttle valve, these passages are of greatly increased length and also somewhat greater cross-sectional area. At each of the intersections the fluid flow is turned back by the fluid flow in the opposing passage, some turbulence and mixing occurs and energy is lost or converted to kinetic or thermal. In practice it is found that very little noise is generated and the gain in kinetic energy is not troublesome. By moving the control rod 20 to shift the element 16 lengthwise in relation to the central outlet 12, the effective length of the throttle passages of the screw-thread can be varied and accurate fine adjustments can be made without the need to make microscopic small adjustments of the rod 20, due to the pitch of the screw-thread. Attached to the element 16 is a shut-off valve element 21 in the form of a solid flange which will close off the outlet 12 completely when the device is in its closed position as illustrated. Since the exit openings from the intersecting threads are directed in opposite directions about the central axis of the screw, their reaction forces are opposed and there will be no resultant circumferential reaction tending to rotate the element 16. The element is also hydraulically balanced lengthwise as explained previously. Instead of a double intersecting screw-thread, similar results may be achieved by other patterns of grooves. For example, the surface may be knurled and then machined down to form fine intersecting passages, or any pattern of passages, which intersect and/or form junctions, may be formed by etching, milling or in any other way. WHAT WE CLAIM IS: -

1. A fluid flow controller, restricter, throttle or pressure-reducer, comprising means providing a plurality of elongate passages, connectable between a common inlet and a common outlet and formed to provide a plurality of junctions or intersections between each other or with further passages, and means- for adjusting the position of the passages relative to the inlet and/or outlet to vary the eflective length of the passages.

2. A fluid flow device according to claim 1, wherein the passages are formed between two contacting parts, for example on the surface of a cylindrical body located within a bore.

3. A device according to claim 2, in which the passages are formed by screw threads.

4. A device according to claim 3, in which the passages are formed by intersecting screw threads of opposite hand.

5. A device according to any of the preceding claims in which the outlets of the passages are inclined or oriented in different directions, to counteract at least partly the reaction forces generated by fluid issuing therefrom.

6. A fluid flow controller, restricter, throttle or pressure-reducer substantially as described with reference to the accompanying drawing.

7. A hydraulic loading system for an hydraulic pump, including a fluid flow controller, restricter, throttle or pressure-reducer as defined in any of the preceding claims.