GB1595376A - Fluid distributor operable by alternative pressure signals - Google Patents

Description

PATENT SPECIFICATION

( 11) 1595376 ( 21) Application No 11846/78 ( 22) Filed 23 March 1978 ( 19) l:

( 31) Convention Application No 7708858 ( 32) Filed 24 March 1977 in ( 33) France (FR) ( 44) Complete Specification published 12 Aug 1981 ( 51) INT CL 3 F 16 K 31/12 ( 52) Index at acceptance F 2 V 10 F 12 E 13 X 14 EIF E 32 K 3 ( 54) FLUID DISTRIBUTOR OPERABLE BY ALTERNATIVE PRESSURE SIGNALS ( 71) We, MARTONAIR LIMITED, a British Company, of St Margaret's Road, Twickenham, Middlesex, do hereby declare the 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:-

The invention relates to a fluid distributor operable by alternative pressure signals and particularly of the kind including a slide movable between two extreme operational positions in each of which the slide effects the connection of fluid inlet and outlet ports of the distributor in different arrangements, the slide being movable into one or other of its operational positions by the application to the slide of an appropriate end force in response to the application to the distributor of one or other of a pair of control pressure signals.

A fluid distributor of the foregoing kind has been described and claimed in the Complete Specification of our co-pending

Application No 2334/78 (Serial No.

1589042) The fluid distributor claimed and described therein includes control means operable to control the movement of the slide each time either one of the control pressure signals is applied irrespective of whether or not the other signal is still being applied.

According to the present invention, a fluid distributor includes a slide movable between two extreme operational positions in each of which the slide effects the connection of fluid inlet and outlet ports of the distributor in different arrangements, the slide being movable into one or other of its operational positions by the application to the slide of an appropriate end force in response to the application to the distributor of one or other of a pair of pressure signals, the distributor having at one end only thereof, a control device defining a cylinder in which two pistons are slidable one behind the other, the outer of the two pistons with respect to the slide being responsive to the application thereto of one of the signals and the inner of the two pistons being engageable with one end of the slide, the pistons being movable either as a unit in one direction, or the outer piston only being movable in said one direction, under the application to said outer piston of said one signal, and the slide being arranged to be moved in the opposite direction by the application of said other signal to the other end of the slide, whereby the application of said other signal to said other end of the slide will move the slide to, or hold the slide in, one of the operational positions, whether or not said one signal is being applied simultaneously to the outer piston, and whereby the application of said one signal to the outer piston will only result in movement of the slide in said one direction by the two pistons moving as a unit to move the slide to, or to hold the slide in, said other operational position, when said other signal is not simultaneously being applied to said other end of the slide.

Conveniently, the outer piston in said control device has a piston rod extending therefrom in the direction towards the slide and the inner piston is mounted for sliding with radial clearance on the piston rod, the two pistons being arranged to be urged apart by a pressurised fluid admitted to a chamber defined in the cylinder between the two pistons, the end of the piston rod remote from the outer piston forming a valve member which is engageable by the inner piston to close a leakage passage to exhaust formed by the radial clearance between the inner piston and the piston rod, the permitted travel of the outer piston being greater than the permitted travel of the inner piston and the slide, whereby when the outer piston has been moved in said one direction by the application thereto of said one signal and said inner piston and the slide have been 1.0 r_ m tn Q tn 1.595,376 arrested the valve member will be open to permit the pressurised fluid in said chamber defined between the pistons to be exhausted, thereby to permit the slide and the inner piston to be moved to said other position by the application of said other signal to said other end of the slide.

Other characteristics and advantages of the invention will be better understood on reading the following description of one embodiment and be referring to the accompanying drawing which shows a longitudinal section of a distributor which includes a slide and is provided with a device for controlling the movement of the slide in accordance with a priority signal.

The distributor illustrated comprises as in the distributor described and claimed in the aforesaid Patent Application a body 1 and a sleeve 2 having a bore 3 within which a cylindrical slide 4 is mounted to slide.

At one extremity, on the right hand side, there is arranged, as in the aforesaid Patent Application, a first piston 8 which divides a cylinder 6 into two chambers 9 and 10, one of which, 9, is connected to a control orifice 11.

The control orifice is provided in a plug 7 which forms the right hand end wall of the cylinder 9.

The piston 8 is fitted with a rod 12 which includes a valve 13 capable of closing a restricting annular orifice 15 between the rod 12 and a bore of a second auxiliary piston 16.

At the other extremity, on the left hand side, there is mounted a plug 7 a fitted with a simple control orifice I la of a known type.

The control orifice 1 la is connected to a chamber 10 a defined between the adjacent ends of the plug 7 a and the slide 4.

The pressure signal acts directly on one of the extremities of the slide 4 of the distributor during the whole time at which it is present.

In the case of the orifice 11, after the slide 4 has been displaced by the intermediary of the piston 8, the valve 13 is open at the end of the stroke and the pressure in the chamber 10 is connected through the orifice 15, a bore 18 and a vent 19 in the slide 4 to atmosphere or returned to the reservoir so that its value falls to a low level, as has already been described in the aforesaid Patent Application Thus, if a signal is then applied to the orifice 1 Ia, a force is thereby exerted on the slide 4 which is greater than the resistance due to the residual pressure in chamber 10 and the slide is displaced and assumes the position illustrated in the Figure.

If a signal applied to the orifice 11 is not removed while that applied to the orifice 1 la is maintained, the piston 8 is freed and it is returned to its rest position by the effect of the low fluid pressure in chamber 10; the valve 13 is thus closed and the fluid pressure in chamber 10 rises to its normal value again.

If a pressure signal is now applied again to the orifice 11 while the pressure signal applied to the orifice I la is present, the slide 4 remains immobile in the position shown in the Figure and only the piston 8 is displaced.

thereby re-opening the valve 13 70 It can thus be seen that the signal applied to the orifice I la has priority over the signal applied to the orifice 11.

For this reason it is possible to change the position of the slide 4 by the application of 75 the signal to the orifice I la irrespective of whether or not the signal is being applied to the orifice II On the other hand, the slide 4 cannot be displaced by the signal applied to the orifice 80 unless the signal previously applied to the orifice Ila has been removed A priority effect exists in one direction only and there is thus produced a distributor with control by priority signal at one control orifice only 85 It should be noted that the distributor retains a memory in each case, that is the slide 4 remains in the state established by the last signal to displace it even after the disappearance of this signal 90 Although the clearance between the piston rod 12 and the bore of the auxiliary piston 16 is described herein as constituting a restricting orifice 15, complete depressurising of the chamber 10 may be permitted when the 95 valve 13 is open, the valve 13 being closed by resilient means such as a spring, as described with reference to Figure 3 of the aforesaid Specification.

Alternatively, the piston rod 12 may pass 100 through a bore in a partition, the bore in the partition forming a restricting annular passage around the piston rod 12, as described with reference to Figure 4 of the aforesaid Specification 105

Claims (3)

WHAT WE CLAIM IS:-

1 A fluid distributor of the kind including a slide movable between two extreme operational positions in each of which the 110 slide effects the connection of fluid inlet and outlet ports of the distributor in different arrangements, the slide being movable into one or other of its operational positions by the application to the slide of an appropriate 115 end force in response to the application to the distributor of one or other of a pair of pressure signals, the distributor having at one end thereof a control device defining a cylinder in which two pistons are slidable 120 one behind the other, the outer of the two pistons with respect to the slide being responsive to the application thereto of one of the signals and the inner of the two pistons being engageable with one end of the slide, the 125 pistons being movable either as a unit in one direction, or the outer piston only being movable in said one direction, under the application to said outer piston of said one signal and the slide being arranged to be 130 1,595,376 moved in the opposite direction by the application of said other signal to the other end of the slide, whereby the application of said other signal to said other end of the slide will move the slide to, or hold the slide in, one of the operational positions, whether or not said one signal is being applied simultaneously to the outer piston, and whereby the application of said one signal to the outer piston will only result in movement of the slide in said one direction by the two pistons moving as a unit to move the slide to, or to hold the slide in, said other operational position, when said other signal is not simultaneously being applied to said other end of the slide.

2 A fluid distributor as claimed in Claim 1 in which the outer piston in said control device has a piston rod extending therefrom in the direction towards the slide and the inner piston is mounted for sliding with radial clearance on the piston rod, two pistons being arranged to be urged apart by a pressurised fluid admitted to a chamber defined in the cylinder between the two pistons, the end of the piston rod remote from the outer piston forming a valve member which is engageable by the inner piston to close a leakage passage to exhaust formed by the radial clearance between the inner piston and the piston rod, the permitted travel of the outer piston being greater than the permitted travel of the inner piston and the slide, whereby when the outer piston has been moved in said one direction by the application thereto of said one signal and said inner piston and the slide have been arrested, the valve member will be open to permit the pressurised fluid in said chamber defined between the pistons to be exhausted, thereby to permit the slide and the inner piston to be moved to said other position by the application of said other signal to said other end of the slide.

3 A fluid distributor constructed and arranged substantially as described herein and shown in the accompanying drawing.

WALFORD & HARDMAN BROWN, Chartered Patent Agents, Trinity House, Hales Street, Coventry, West Midlands.

Agents for the Applicants.

Printed for Her Majesty's Stationery Office by Burgess & Son (Abingdon) Ltd -1981 Published at The Patent Office, Southampton Buildings London, WC 2 A IAY.

from which copies may be obtained.