US2985490A

US2985490A - Fluid pressure valve

Info

Publication number: US2985490A
Authority: US
Inventors: Charles E Gates
Original assignee: Bendix Westinghouse Automotive Air Brake Co
Current assignee: Bendix Westinghouse Automotive Air Brake Co
Priority date: 1959-10-05
Filing date: 1959-10-05
Publication date: 1961-05-23
Anticipated expiration: 1978-05-23
Also published as: GB902321A

Description

c. E. GATES 2,985,490

FLUID PRESSURE VALVE Filed 001;. 5, 1959 May 23, 1961 1 1 5 INVENTOR- CHARLES E. GA-nss BY ffmlw ATTORNEYS United States Patent. O

FLUID PRESSURE VALVE Charles E. Gates, Elyria, Ohio, assignor to Bendix-Westinghouse Automotive Air Brake Company, Elyria,

Ohio, a corporation of Delaware Filed Oct. 5, 1959, Ser. No. 844,482

12 Claims. (Cl. 303-40) This invention relates to fluid pressure valves and more particularly to an improved self-lapping relay valve of the type used to deliver fluid under pressure, particularly compressed air, from a local pressure source to a local fluid pressure actuated device in response to control pressure delivered to the valve from a remote source.

The principal object of the present invention is to provide an improved valve of the foregoing type which is so-constructed and arranged that the pressuredelivered by the valve from the local source to the local pressure actuated device is substantially equal at all times to the control pressure delivered to the valve from a remote source.

Still another object of the invention is to provide an improved valve of the foregoing type which is especially suited for use as a relay valve in brake systems.

Yet another object of the invention is to provide an improved relay valve for brake systems which reacts rapidly to even slight changes in pressure and raises, lowers, holds or completely exhausts the air pressure in the brake chamber as the brake valve raises, lowers, holds or completely exhausts air pressure from the relay valve.

Still another object of the invention is to provide a relay valve of the foregoing nature which employs a single valve element for controlling the flow of fluid pressure to and from the pressure actuated device with the element being so arranged and constructed that air pressure acting thereon is at all times substantially balanced, thereby rendering the valve exceptionally responsive to the control pressure from the remote source.

Other objects and their attendant advantages will become apparent as the following detailed description is read in conjunction with the accompanying drawings wherein:

Fig. 1 is a vertical cross-sectional view of a valve constructed in accordance with the invention; and

Fig. 2 is a vertical cross-sectional view of a second embodiment of the invention.

Referring to Fig. l of the drawing, the valve of the invention consists of a body and a cap member 12 which is connected in any conventional manner to the body. The body 10 is provided with inlet and

delivery ports

14, 16 and the cap is provided with control and

exhaust ports

18, 20. The

ports

14, 16, 18 and 20 communicate respectively with an inlet cavity 22, a delivery cavity 24, a control cavity 26 and a hollow plunger 28. The hollow plunger 28 is carried by a diaphragm 30 whoseperipheral edge is clamped between the cap 12 and the body 10 as shown. The plunger 28 is provided with an upper end 32, slidably received in a bore 34 in the cap 12, and an elongated lower part 36, of greater diameter than the upper part, which is slideably received in a bore 38 in a wall 33 which separates delivery cavity 24 from a balancing cavity 35 beneath the diaphragm 30. The lower part 36 of the hollow plunger 28 extends into the delivery cavity 24 and in its normal position its lower end 39, which affords an exhaust valve seat, terminates a spaced distance above a valve member 40 which is normally

livery cavities

22, 24. The plunger 28 and the diaphragm 30 are retained in their normal positions of Fig. 1 by means of a spring 46 interposed between the upper surface of the wall 33 and a diaphragm clamping ring 47 which is riveted to a clamping flange 48 integral with the plunger 28.

The valve member 40 has a downwwardly extending part which is of stepped construction and has an upper part 50 slideable in a cavity 52, whose lower end is open to atmosphere through a port 54, and has a lower part 56 of less diameter which is slideable in a cavity 58 against the floor of which the lower end of the spring 41 bears. For reasons that will become more fully apparent, the cavity 58 beneath the valve 40 and the balancing cavity 35 beneath the diaphragm ar both freely connected with the delivery cavity 24 by wayof a port 60 and

passages

62 and 64 respectively.

Broadly, the operation of the valve is controlled by the admission of fluid pressure through the control port 18 to cavity 26 to exert a downward force on the diaphragm which in turn causes the exhaust valve seat 39 of the plunger '28 to move doumwardly into sealing engagement with sealing surface 42 of valve member 40 thus disconnecting the exhaust port 20 from delivery cavity 24. Continued movement of the diaphragm 30 and plunger 28 then unseats sealing surface 42 from seat 43 to connect the inlet cavity 22 with the delivery cavity 24. Fluid pressure in the inlet cavity 22 then flows into delivery cavity 24 and out through port 16 to the device to be actuated. Simultaneously, fluid pressure flows by way of port 60 and passage 64 to balancing cavity 35 beneath diaphragm 30 and by way of passage 62 to cavity 58 beneath valve member 40'. When delivery pressure acting on the various areas exposed thereto substantially equals the control pressure acting on the upper side 'of the diaphragm, the diaphragm, plunger and valve 40 move upwardly under the influence of the

springs

41, 46 until the valve 40 closes. Any tendency for the diaphragm to continue to move upwardly would tend to lift the exhaust seat 39 from valve member 40 and dump delivery air to atmosphere via the port 20. This would cause the delivery pressure under the diaphragm to immediately drop to less than the control pressure above the diaphragm, and the exhaust plunger would immediately thereafter return to a sealing relationship with the valve member 40. However, since the forces are balanced, the plunger does not actually lift but instead it laps wherein the valve 40 is in sealing engagement with the exhaust seat 39 and also with the inlet valve seat 43 so that there is no further flow of fluid pressure.

In order that the valve will be almost instantaneously responsive to control pressure and also deliver pressure which is substantially equal to the control pressure, there must be substantially no opposition to the movement of the valve 40 to its open position and, after opening, the forces acting downwardly tending to open the valve mus be substantially equal to the forces acting upwardly tending to close the valve. In accordance with the invention pressure opposition to the opening of valve 40 is elimii the total area subjected to opposing control pressure should be substantially equal. In the embodiment of Fig. 1, the control-pressure responsive area comprises the total area on the top of the diaphragm less the area defined by the external diameter of the upper end 32 of plunger 28. The area subjected to delivery pressure comprises the area of the underside of the diaphragm exposed to balancing pressure and an increment of area which comprises the annular area between the outside diameter of the lower end 36 of the plunger and the diameter of the exhaust valve seat 39. If this last area is arranged to equal the difference in area between the control side of the diaphragm and balancing side of the diaphragm it will be apparent that when the valve of the invention is in lap condition, the only force acting up wardly on the diaphragm will be the force of the spring 46. Since this spring can be very light, its force may be reflected in a prmsure diflerential between control and' delivered pressure on the order of less than 1 p.s.i.

When the valve 40 is in lap position delivery pressure acts on the top thereof tending to open it. To oppose this opening pressure a relatively strong spring 41 could be employed but if this were done the sensitivity of the valve would be obviously aifected. In accordance with the invention the eflFects of delivery pressure on the valve are nullified by first determining the area on the top of the valve exposed to delivery pressure and then constructing the valve 40 so that its lower end 56 has a diameter which affords an area substantially equal to the first area. With the exhaust seat 39 in sea-ling engagement with sealing surface 42 of valve 40, the area exposed to delivery cavity pressure comprises the annular area between the valve seat 43 and the exhaust seat 39 of the plunger. By constructing the lower end 56 of valve 40 so that its area exposed to delivery pressure in cavity 58 is substantially equal to the described annular area on the top of the valve, it will be apparent that the valve 40 can not be influenced by pressure in the delivery cavity.

The invention contemplates having either exactly balanced opposing diaphragm areas and separately balanced opposing valve areas or an arrangement wherein the upper side of the diaphragm has a slightly greater area than the lower side (including the plunger area exposed to delivery pressure) and the lower side of the valve has a slightly greater area than the upper side, the larger areas on the diaphragm top and valve bottom being greater than their respective opposite sides by the same amount.

This last arrangement has the advantage of compensating the opposing fluid pressure forces for the force of spring 46. For example, any downward force exerted by control pressure on the top of the diaphragm is opposed by the upward force of the spring, so that with a p.s.i. control pressure, an upper diaphragm area of 8.5 sq.in. and a one-pound spring force, the total downward force on the diaphragm is 85 pounds minus one pound or 84 pounds. If the area beneath the diaphragm is made to be 8.4 square inches, the total pressure in the delivery cavity required to balance the control pressure or 10 psi. is 84 pounds divided by 8.4 sq. in. or 1.0 p.s.i., which is exactly the same pressure as on top of the diaphragrn. Since the upper side of the diaphragm is onetenth of a square inch greater than the lower side, the lower side of valve 40 in cavity 58 should likewise be one-tenth of a square inch greater than that part of the upper side of the valve which is normally exposed to delivery pressure. With this arrangement, when the diaphragm is moving to open valve 40 so that the diaphragm plunger and valve perform essentially as a unitary structure, the total opposed areas will be equal and the only opposing force will be that of the

springs

41 and 46.

The embodiment of the invention illustrated in Fig. 2 is substantially identical to that of Fig. 1 except that instead of a diaphragm a piston is employed, and the valve between the inlet and delivery cavities is balanced by delivery pressure in a different manner. Briefly, the valve of Fig. 2 comprises a body 70 having inlet and

delivery ports

72, 74 respectively connected to inlet and

delivery cavities

76, 78 with the latter also serving as a balancing cavity beneath a piston 80 slideable in a cylinder 82 in the upper part of the body 70. The upper side of the cylinder is closed by a cap member 84 which forms with the piston a control cavity 86 having a port 88 connected to a control valve such as a brake valve (not shown). The cap member 84 .is provided with .a central exhaust port 90, covered by a conventional filter 92, which communicates with a hollow plunger '94 integral with piston 80 and having an upper end 96 slideable in a bore 98, and a lower end'100 of greater diameter than the upper end 96 extending into the delivery cavity 7 8. The piston 80 and hence the plunger 94 are normally retained in the position shown by a spring 102 so that an exhaust valve seat 104 surrounding the lower end of the plunger is out of engagement with a valve member 105 which controls communication between the inlet and

delivery cavities

76, 78.

Valve 105 is of stepped construction having an upper part 106 carrying outer and inner valve members 108, 1l10 respectively engageable with a valve seat 112 surrounding a port 1 14 between the inlet and delivery cavities and the mentioned seat 10 4 on the bottom of the exhaust plunger 94. The upper part 106 of the valve 105 is slideable in a bore 116 whose lower end alfords with the step 117 of the valve a balancing cavity 118 which at all times is connected with the pressure in the delivery cavity 78 by ways of vertical passages 120. The lower end 122 of the valve is of less diameter than the upper end 106 and is slideable in a bore 124 which is at all times connected to atmosphere through a central passage 128 and the hollow plunger 94. The valve 105 is normally retained in the position of the drawings by a spring 130 which acts between a flange 132 in the passage 128 and the bottom of the cavity 124.

The operation of the valve of Fig. 2 is substantially identical to that of Fig. 1, the only difference residing in the balancing of the valve 105. This is accomplished by the vertical passages and the balancing cavity 118 which is located at the step 117 of the valve rather than beneath the valve as in the embodiment of Fig. 1. By arranging and constructing the valve 105 so that the area of the step 117 is equal to the area between the plunger valve seat 104 and the valve seat 112 it will be apparent that when the valve 4105 is in lap position the fluid pressure force in the delivery cavity acting downwardly on the valve will be exactly balanced by the delivery pressure force in cavity 118 acting upwardly.

In the embodiment of Fig. '2 the lower part 100 of plunger 94 is illustrated as being substantially larger than the upper part 96 so that the upper side of the control piston has a substantially larger area than the .opposite or balancing side. It will be apparent from the description of Fig. 1 that the difference in size of the opposed motive areas of the piston or of the valve 105 may be changed to suit the circumstances, it being desirable that the upper side of the piston be larger so that the delivered pressure will more nearly balance the control pressure, having regard for the upward force of the spring 102.

From the foregoing description of the embodiments of the valve of the invention it will be apparent'that there has been provided a valve which is particularly suited for use as a relay valve in brake systems wherein pressure is applied to the rear brakes of a vehicle from a local reservoir in responseto a relatively small volume of control air delivered to the relay valve from a manually controlled brake valve which may be located a relatively long distance from the rear brakes. The valve of the invention because of its high degree of sensitivity increases the speed of application and release of the rear wheel brakes in response to brake valve pressure over the speed afforded by conventional relay valves now in use. By

eliminating unbalanced conditions in both the energized and de-energized condition of the valves, the springs employed in the valve can be relatively very light as opposed to springs employed in conventional valves and by pro-selecting the fluid pressure receiving motive areas of the valve the opposition of the springs can be largely compensated for so that the valve is not only rapidly responsive to control pressure changes but the delivered pressure is also substantially equal at all times to the control pressure. 7

It will be apparent to those skilled in the art that the valve of the invention is susceptible of a variety of modifications without, however, departing from the scope and spirit of the appended claims.

What is claimed is:

1. A valve, for controlling the application of pressure from a supply source of fluid pressure to a pressure actuated device in response to pressure from a control source of fluid pressure, comprising a body having an inlet cavity connected to said supply source of fluid pressure and a delivery cavity connected to said pressure actuated device, a pressure responsive element in said body having opposed upper and lower pressure receiving areas re spectively responsive to pressure received from said control source and pressure delivered to the actuated device, a hollow exhaust plunger centrally connected to said pressure responsive element for movement therewith and having an upper part extending above said element and slidingly received in a bore in said body connected to atmosphere and having a lower part extending below said element into said delivery cavity, an inlet valve seat between said inlet and delivery cavities, an inlet valve resiliently urged against said valve seat, said inlet valve having an integral downwardly extending stepped portion extending through said inlet cavity and having an upper part extending through said inlet cavity and a lower part of less diameter than said upper part, an exhaust valve integrally connected to said inlet valve for simul-.

taneous movement therewith, said exhaust valve closing the lower end of the exhaust plunger upon movement against said exhaust valve, said inlet valve being thereafter opened upon continued movement of the pressure responsive element, a stepped bore in said body for slideably receiving the upper and lower parts of the stepped portions of said inlet valve, one of the last named parts forming with said bore a pressure receiving cavity and the other part forming with said bore a cavity open to atmosphere, and means including a fluid pressure passage for simultaneously connecting the lower side of said pressure responsive element and said pressure receiving cavity with pressure delivered to said pressure actuated device upon opening of said inlet valve.

2. The valve of claim 1 wherein the upper part of= said plunger has less diameter than the lower part thereof so as to afiord a greater motive area on the upper side of said element than the lower side thereof.

3. The valve of claim 2 wherein the area of said downwardly extending portions of said inlet valve exposed to inlet pressure is greater than the area on the upper side of said valve exposed to inlet pressure.

4. The valve of claim 3 wherein the greater area of said downwardly extending portion is substantially equal to the greater area on the upper side of said element.

5. The valve of claim 1 including resilient means normally urging said pressure responsive element away from said inlet valve.

6. The valve of claim 1 wherein said inlet valve is resiliently closed in the direction of fluid flow and wherein the upper part of said downwardly extending stepped portion extending through said inlet cavity is of substantially the same diameter as said valve seat.

7. In combination with a relay valve of the type having an inlet valve resiliently urged against a valve seat to close a connection between inlet and delivery cavities and having an element carrying an exhaust plunger which is moved in response to control pressure acting on said element to close said plunger and thereafter open said inlet valve, the invention which comprises a solid downwardly extending part integral with said inlet valve, and a bore spaced below said valve seat for slidingly and sealingly receiving said downwardly extending part, said par-t having the same cross-sectional area as said valve seat so as to provide no residual area on the under side of said valve exposed to pressure in said inlet cavity to oppose the opening of said valve, a second downwardly extending part of less cross-sectional area than said first part and integrally connected therewith below said first part, a second bore in said body for slidingly and sealingly receiving said second part, said bores having lower walls form-ing cavities with the corresponding lower surfaces of said downwardly extending parts, means for connecting one of said cavities at all times to atmosphere, and means for connecting the other of said cavities at all times to said delivery cavity.

8. In the relay valve of claim 7 wherein the means for connecting the pressure cavity afforded by one of the downwardly extending parts of said inlet valve comprises a vertical passage through said valve and said downward extension, said passage connecting the upper side of said valve normally exposed to pressure in said delivery cavity with said cavity formed by said downward extension.

9. In the relay valve of claim 7 wherein the area of the downward extension in the cavity formed thereby which is exposed to delivery pressure is substantially equal to the area of the upper side of the valve exposed to pressure in the delivery cavity when said plunger is moved against said valve to close the same.

10. Valve mechanism comprising a body, inlet and delivery ports in said body, means in said body aifording a fluid pressure passage connecting said inlet and delivery ports, valve means in said passage for controlling the flow of fluid therethrough, said valve means being resiliently urged to a position disconnecting said ports, a pressure responsive control element in said body responsive to pressure from a control source, a plunger connected to said element in axial alignment with said valve means for controlling said valve means in response to control pressure acting on said element, an exhaust valve and port in said body normally connecting said delivery port to atmosphere, means for closing said exhaust valve and port and then opening said valve means upon movement of said control element and plunger in a direction for opening said valve means and vice versa, a stepped extension integral with said valve means and forming two parts of different cross sectional area, a stepped bore in said body slidingly and sealingly receiving the respective parts of said extension, said stepped parts with the corresponding parts of the bore forming separate cavities, means for connecting one of said cavities at all times with said delivery port, and means for connecting the other of said cavities at all times with atmosphere, the pressure in said cavity connected to said delivery port opposing the pressure at said delivery port acting on said valve means tending to move it in an opening direction.

11. In a self-lapping relay valve of the type comprising a valve body having control, inlet and delivery cavities and a pressure responsive element responsive to opposing pressures in said control and delivery cavities, a port between said inlet and delivery cavities, valve means resiliently urged in the direction of fluid flow to normally close said port, an exhaust port coaxially arranged with respect to said valve means and normally connecting said delivery cavity to atmosphere, a plunger carried by said element and arranged to close said exhaust port and then open said valve means when control pressure exceeds the pressure in said delivery cavity and vice versa and to move said valve means to lap position when said control and delivery pressures are substantially equal, the

invention which comprises a stepped extension integral with said valve means and forming two par-ts of different press sectional area, the part adjacent said valve means having va greater cross sectional area than the other part, a stepped bore in said body slidingly and sealingly -receiving'therespective parts of said extension, said stepped parts forming the corresponding parts of the bore separate cavities, means for connecting one of said cavities at alltimes with atmosphere and means for connecting the other cavity at all times to said delivery cavity.

12. ,In the selfelapping valve of claim 11 wherein the area of said stepped part of said extension which is ex- '8 posed to the pressure of said delivery cavity is substantially equal to the area of said valve means exposed to the pressure insaid delivery cavity when said valve means is in lap position.

References Cited in the file of this patent UNITED STATES PATENTS