US2788800A

US2788800A - Adjustable relief valves

Info

Publication number: US2788800A
Authority: US
Publication date: 1957-04-16
Anticipated expiration: 1974-04-16

Description

April 1.6, 1957 J. M. TowL'ER ETAL 2,788,800

ADJUSTABLE RELIEF VALVES Filed Jan. 28, 1952 2 vsheetssheet 1 www@ LNE@ INYENTOPS l John m rice Towler` Frank H horn Towler' April 15, w57 J. M. TOWLER ET Al- ADJUSTABLE RELlEF VALVES 2 Sheets-S1166?. 2

Filed Jan. 28, 1952 A i INVENTPS John maurice Towler' Frank Ha'thorn Towler DIUSTABLE RELLEF VALVES John Maurice Terrier, Radley, and AFrank Hathom Towler, Doh Park, naar tiey, England; Frank H. Towler, administrator of said .ohn Torr/ienneceased, assignors to Electran'iic Presses Limited, Rooiey, England, a limited liability company of Great Britain Appiication .ianuary 2S, H52, Serial No. 258,477

Claims priori y, application Great Britain February 6, 1951 4 Claims. (Si. 137-540) This invention relates to adjustable relief valves.

One object of this invention is to provide a new and improved construction of adjustable relief valve embodying means .vhereby the blow-o pressure may be regulated quickly by rotating a dial or short lever either directly by hand or by remote control by the addition of suitable electric, mechanical, or iluid transmission between the relief valve and the control point.

Another object of the invention is to provide an adjustable relief valve of such a construction that it may be regulated quickly and easily to blow oif at any intermediate pressure between the maximum and minimum pressure at which the valve is designed to operate.

Broadly the present invention consists of a springloaded adjustsa'ble relief valve in which the 4spring is loaded by hydraulic pressure to increase and to decrease the load applied by the spring to the relief Valve.

A spring loaded adjustable relief valve according to the preferred embodiment of the invention has hydraulic loading means which includes two pistons arranged coaxially within a cylinder in which they are each capable of independent longitudinal movement, one of said pistons serving to load the relief valve spring by hydraulic pressure and the other piston being in axial uid balance and movable mechanically from the exterior of the cylinder relatively to the load applying piston and automatically operating valve means controlling the admission of pressure liquid to and its exhaust from a space between the opposing faces of the two pistons, the arrangement being such that any relative movement of the balanced piston resulting in upset of the normal positional relationship of the two pistons produces operation of the pressure liquid controlling valve means automatically to bring about movement of the load applying piston with restoration of the normal positional relationship between the two pistons and corresponding variation in the load -applied to the relief valve by its spring.

'ln the above preferred embodiment it is also preferred that movement of the load applying piston in the direction to reduce the load on the spring shall be effected by the spring and movement of the same piston in the opposite direction to increase the load shall be effected by hydraulic pressure. This may be attained by a construction in which the space between the two pistons exhausts through an opening in one of the pistons said opening being opened and closed by a valve carried by the other piston. This valve is inwardly displaceable against a spring and on the opposite end of its stem is formed a further valve head which controls the admission of pressure liquid to the space between the pistons.

The parts in the above construction are so arranged that upon movement of the uid balanced piston away yfrom the load applying piston the exhaust opening is opened thus allowing the pressure in the said space to fall until it can be overcome by the relief valve spring which then moves the load applying piston towards the Patented pr. 16, 1957 fluid balanced piston in its newly adjusted position. This movement continues until the exhaust opening is again closed when continued movement results in the inward displacement of the valve stem and the opening of the valve on its opposite end with admission of further pressure liquid to the aforesaid space. This admission results in slight outward movement of the load applying piston to restore its normal positional relationship with the fluid balanced piston. With the pistons in this latter position the space is sealed both against the admission and exhaust of the pressure liquid until such time as the positional relationship is again upset either as a result of leakage from the space or wilful movement of the fluid balanced piston by an operator.

The combined inlet and exhaust valve may either be carried by the uid balanced piston and the exhaust opening -be in the load applying piston or such valve may be carried by the load applying piston and the exhaust outlet be in the fiuid balanced piston. rangement has the advantage that the mechanism for moving the uid balanced piston is not then subject lto the hydraulic pressure and so may more easily be sealed against leakage.

In order that the invention may be clearly understood and carried into etect embodiments according to both examples will now be described by aid of the accompanying somewhat diagrammatic drawings in which:

lFig. l is a sectional elevation of an adjustable relief valve embodying the features of the invention in which the Iadmission and exhaust valve is carried by the uid balanced piston.

Fig. 2 is a part section in plan taken on the line 2 2 in Fig. 1.

Fig 3 is a sectional elevation of a modified form of the relief valve in which the admission and exhaust valve is carried by the load applying piston.

Fig. 4 is a part section in plan taken 4on the line 4-4 in Fig. 3.

Referring to the drawings, the relief valve illustrated in Figs. l and 2 comprises a body dening a chamber or cylinder 1 which is closed at one end by a cover plate 2 and at the opposite `end by a iitting having a bore for a movable valve member 3. The outer end of the bore is open to the pressure of uid `admitted through an inlet passage 4 in the tting. When the pressure in the inlet passage acting on the end of the Valve member 3 has risen to a predetermined figure the valve member is forced inwardly against the force `exerted on it by a loading spring 5 until its movement is sufficient for the stem of the valve member to uncover radial ports 6 and allow iluid to escape through an exhaust passage or port 7.

In vaccordance with the invention the spring 5 is loaded by the application of suitable hydraulic pressure which may be less than the main pressure and the means provided to achieve this in the illustrated examples consist of two coaxial pistons working within the cylinder 1. These pistons are hereinafter referred to as a lluid balanced piston S and a load applying piston 9.

The fluid balanced piston 8 is thus named for the reason that there extends through it a port 1d which is open at one end to a space 2li normaliy separating the two pistons and at the opposite end to a space )l2 on the opposite side of the piston 3 which is closed by the cover plate 2. By this means the piston 8 is always maintained in axial hydraulic balance even though the pressure within the space il is subject to frequent change, This permits the piston 3 to be moved freely along the length of the cylinder 1 by outside mechanical means which will hereinafter be described. A

The load applying piston 9 has at its lower end a nose i3 which seats against a spring pad 14 on the outer end This latter ar-V ofthe springA 5. The opposite end of the spring is also supported by a spring pad and this in turn is engaged centrally by a conical nose 16 on the inner end of the relief` valve 3. Y A The piston 9 in the example illustrated in Figs. l and 2,V is drilled to provide down its centre au exhaust passage 17, and this opens into the space 18 at the outer end of the piston 9 by way yof a branch passage 13a. The space 18 is open to constant exhaust by means of a port 18b, through the wall of `cylinder 1. By this meansa path is provided `from' the space 11 to'exhaust through which pressure liquid within `the said space may flow when it is required to lower the pressure therein. Y

The spring 5 is loaded by admitting Vpressure liquid to the space 1,1 and for this purpose the exhaust passage 17 must be closed. lt is also required that the degree of loading shall be determined by the position of the fluid balanced piston 8 relative to the spring 5. The means for this purpose, according to both the examples illustrated, comprises a valve designed to control both Vthe admission of pressure liquid to and its exhaust from the space'11. This valve, asV shown, is composed of a stem 19 having its outer end pointed to form a

mitre valve

2,0 and its opposite end enlarged to form a mushroom check valve 21. The mitre valve 29 serves to control the opening and closing of the exhaust passage 17 and therefore theirelease of pressure liquid from the space 11 and the check valve 21 controls theadmission of pressure liquid to said space 11.

For the reception of the aforesaid admission and exhaust valve one of the pistons, the piston 8in the valve shown in Fig. l, is bored interiorly to provide a chamber 22 and a parallel bore 23 leading from said chamber 22 to the space 11. rl`he chamber 22 is in constant cornmunication with a pressure liquid inlet 25 by way of a longitudinal groove 25a in the side of the piston carrying the valve and a transverse passage 26. The bore 23 is placed in communication with the space 11 by means of a passageV 27.

The stem 19 of the'valve has a working and liquid tight t in the bore 23, but so that pressure liquid from the chamber 22 may enter the space 11 when the check valve 21 is off its seat, the stem 19 is formed with a reduced portion 19a, thus forming with the wall of the bore 23 an annular chamber which communicates with the space 11 by way of the passage 27. A As will be seen by reference to Fig. l of the drawings the valve stem 19 at the end which is formed as a mitre valve extends beyond the end of the piston 8, whereby the mitre valve is permitted to seat within the opposing end of the exhaust passage 17 in the piston 9 and with the check valve Y21 also seated to ensure that the two pistons maintain a normal positional relationship with each other and separated by the space 11. The valve is held in this position by means of a light spring 28.

It will thus be seen that if the iluid balanced piston 8 is moved away from the load applying piston 9 the mitre valve will be lifted from its seat and pressure liquid withinthe space 11 will flow to exhaust through the exhaust passage 17. The pressure within the space 11 will, in consequence, fall until it can be overcome by the opposing pressure of the spring 5.

This spring will then move the piston 9 towards the opposite piston 8 in its newly adjusted position and this movement will continue until the mitre valve end of the valve stem 19 is contacted to close the exhaust passage 17 when continued movement of the piston 9 will force the valve 'stem inwards thus lifting the check valver21 from its seat and allowing pressure liquid fromrchamber 22 to ow into space 11. The pressure in said space will thus be restored and the piston 9 will, in consequence,

- assume a position of balance which will be that of normal positional relationship with piston 8.

Similar1y,fif the uid balanced piston 8 Vis moved towards the piston 9 the valve stem will be forced inwards from the space 11 between the pistons.

2,788,800 y. fr u f and pressure liquid will be admitted to the space 11. This will result in the piston 9 being forced away from `the piston 8 against the opposing pressure of the spring 5, which in consequence will have its load increased and this movement of the piston 9 will continue'until a position of equilibrium is attained and the normal positional relationship between the two pistons is restored.

This restoration of positional relationship will thus octhe piston 8 within its cylinder and as .previously explained Y the blow-olf pressure may be regulated 'to giverinnite variation between a maximum and minimum by rotating a dial or short lever eitherV directly by hand or by remote control by the addition -of suitable electric, mechanical,`

or fluid transmission between the relief Valve and the control point. l Y Y In the example illustrated regulation is effected directly by hand by rotating a dial 29 over a scale on an instrument panel Si? and this rotary movement of the dial is translated into longitudinal movement of the piston SV through a pinion 31 on the dial spindle 32 and an engaged rack 33 on the piston 3.

In the valve shown in Figs. 3 and 4 of the drawings the valve plunger controlling admission of pressure uid to and exhaust of uid from the space 11 between the

pistons

8 and 9 is carried by the latter piston. Aside from this the valve is similar structurally and functionally to that described above. ln the modied valve the piston 9 hasa bore defining a chamber 22 with a coaxial passage 23 extending therefrom to the space 11 between the two pistons. The chamber 22 is in constant communication with a pressure fluid inlet 25 in the valve body by way of a circumferential groove 25al in the side of the piston 9 and a transverse passage 26 also in the piston. The passage 23 yis yin communication with the space 11 by Way of a passage 27 in the piston.

A movable member or plunger of the modified valve is similar to that above described comprising aV stern 19 having a working and liquid-tight lit in the passage 23'. The plunger also has a reduced central portion 19a1 and an enlarged end portion shaped Vto form a mushroom check valve v21'. is tapered to form a mitre valve Ztl operative to control duid flow through a passage 17V in the passage 8. This latter passage is connected by a branch passage lal with anelongated longitudinal groove in the piston 3 which is in constant communication with an exhaust passage 18b1 which also communicates with the space 18 below the piston 9.

VCheck valve 21 of the valve plunger is urged by a spring 28 against a seat adjacent the opening from-the chamber 22 to the passage 23. VThe check valve thus is Y.

normally effective to prevent ilow of pressure iiuid from the inlet passage 25 into the space 11 between the two pistons. As in the form of the valve first described movement of the piston 8 away from the piston 9 will result in the opening of the passage-17 to allow exhaust of huid Spring Swill thus become effective to shift the plunger 9 .toward the plunger-8 until the predetermined piston relationsllipV or spacing is restored by engagement of the mitre valve 20 with the pistons to close-the passage 17. in such movement `of ,theppiston-9 the loading of the spring 5 is, of course, rduced.

Upon Ymovement of the piston S toward the piston 9 the valve plunger will berforced inwardly, thus unseating the eheekvalve 21.V to admit ow of pressure fluid from the inlet passage 2S'Yinto the space 11 between the two pistons. Thiswill result ,in the piston 9 being forced awayfromrtherpiston' against the yopposing pressure of the lspring 5 which, in consequence, will have its lload The outer end of the valve stem 19Y increased. Such movement of the piston 9 continues until the check valve is closed and a position of equilibrium is attained with the two pistons in their normal positional relationship.

We claim:

1. In a relief valve having a movable valve member biased toward a closed position by a compression spring, fluid pressure operated means for variably loading the spring to determine the pressure required for moving the valve member to open position, said loading means comprising, in combination, means defining a chamber, a pair of piston elements disposed within said chamber in end to end relation, means operable to adjust the position of one of said piston elements axially of said chamber and to retain the element in adjusted position, the other of said piston lelements being freely movable in said charnber and coacting with the valve spring to load the same, said one piston having an inlet passage for introducing fluid under pressure into the chamber between the piston elements, said other piston element having an outlet passage for the exhaust of fluid from the chamber between Ithe piston elements, and a movable valve plunger carried by said one piston element controlling uid ow through both passages.

2. Relief valve spring loading means as deiined in claim 1 in which the movable valve plunger has a stem positioned for engagement with the movable piston element so as to close the outlet passage and movable upon such engagement to shift the valve plunger to open the inlet passage, the uid admitted through said inlet passage acting to shift the movable piston element in a direction to permit the valve plunger to close the inlet passage, said valve plunger acting to terminate the flow of pressure uid through the inlet passage when the two piston elements are in predetermined spaced relation.

3. A relief valve comprising, in combination, a valve body having pressure liuid inlet and outlet passages, a movable valve member controlling communication between said passages, a spring coasting with said valve member and yieldably urging it in a direction to bloei; communication between said passages, said valve body defining a chamber coaxially alined with said valve member, a pair of piston elements disposed Within said chamber in end-to-end relation, the piston element remote from said valve member being normally restrained against movement but adjustable axially of said chamber toward and from the other piston element, the other of said piston elements being movable relative to said remote piston element and coacting with said spring, and valve means carried by one of the piston elements and actuated by the other piston element controlling the admission of pressure fluid to and exhaust of pressure fluid from the chamber between the piston elements to apply a load to said spring through said other piston element, the position of said remote piston element in said chamber determining the extent of the spring loading.

4. A relief valve comprising, in combination, a valve body having pressure duid inlet and outlet passages, a movable valve member controlling communication between said passages, a spring coacting with said valve member and yieldably urging it in a direction to block communication between said passages, said valve body defining a chamber coaxially alined with said valve member, a pair of piston elements disposed within said chamber in end-to-end relation, the piston element remote from said valve member being normally restrained against movement but adjustable axially of said chamber toward and from the other piston element, the other of said piston elements being movable relative to said remote piston element and coacting with said spring, and valve means including a plunger slidably supported in one piston element and projecting therefrom for engagement by the other piston element controlling the admission of pressure uid to and exhaust of pressure iiuid from the chamber between the piston elements to apply a load to said spring through said other piston element, the position of said remote piston element in said chamber determining the extent of the spring loading.

References Cited in the file of this patent UNlTED STATES PATENTS 1,796,796 Le Valley Mar. 17, 1931 1,976,820 Wettstein Oct. 16, 1934 2,073,835 Finley Mar. 16, 1937 2,109,958 Finley Mar. l, 1938 2,398,811 Stacy Apr. 23, 1946 2,504,470 Troutman Apr. 18, 1950