US2589586A - Feed valve for air brakes - Google Patents

Description

March 18, 1952 E. c. VROMAN 2,589,586

FEED VALVE FOR AIR BRAKES Filed Oct. 6, 1949 3 Sheets-Sheet 1 Fie. '2.

48. 68 ss 5* I 21 '36 M Q 0 a, 1+ 14 Y I F1cs.8 19

3nvenfor Z9 Erwin C.Vroman Q LZJM 5 3'7 Gttornegs Q Max ch 18, 1952 E. c. VROMAN FEED VALLVE FOR AIRBRAKES 3 Sheets-Sheet 2 Filedoct. s, 1949 Fiei:

. I Bmaemor ErwinCN'roman (Q9 &jm

' (Ittomegs March 18, 1952 Q VROMAN F EED VALVE FOR AIR BRAKES 5 sheet-sheet 3 Filed Oct. 6, 1949 I Inventor ErwinQV'r-o'man QJM (Ittor'negs Patented Mar. 18, 1952 FEED VALVE FOR AIR BRAKES Erwin C. Vroman, Watertown, N. Y., assignor to The New York Air Brake Company, a corporation of New Jersey Application October 6, 1949, Serial No. 119,862

3 Claims.

This invention relates to feed valves for air brakes, and particularly to feed valves of the type widely known in the airbrake art as Model F, manufactured in general accordance with the patent to Campbell No. 1,781,747, issued November 18, 1930. The present application is in part a continuation of application Serial No. 38,677, filed July 14, 1948, now abandoned.

The F type fed valve has a main valve which controls air flow and is adjusted against a valveopening spring bias by a single-acting piston motor subject to a regulatory pressure. The regulatory pressure which actuates the valve motor is controlled by adjusting a throttling inlet valve so that its flow capacity, under the available supply pressure, passes above or below the outflow capacity of a fixed bleed port which constantly vents the motor to atmosphere. The throttling inlet valve is biased in a closing direction by a loading spring whose loading is adjusted to determine the pressure established by the feed valve, and is forced open against said spring bias by discharge pressure established by the feed valve acting against a flexible metal diaphragm.

The F type feed valve was a decided step in advance in the art. The present invention, based on an extensive study of the performance of the earlier commercial valves of the F type, permits commercial production of feed valves whose sensitiveness and stability are each above standards heretofore attainable by any previously known feed valve.

The present invention oiiers a valve which under commercial conditions, and for periods be- 1 tween servicing of at least six and commonly as much as twelve months, will regulate at any desired setting from 45 p. s. i. to 110 p. s. i. with a maximum pressure variation of A, p. s. i. The improved feed valve is smaller than prior embodiments, and has a smaller main valve, but aifords a materially increased flow capacity.

These results are secured by using an improved throttling inlet valve having desirable flow-controlling characteristics and by coordinating these with those of the bleed port, the main valve and the motor which actuates the main valve. Throttling of the communication between said motor and the valve unit which controls it, is an important factor in stable operation.

Good flow capacity of the main valve depends on stability of adjustment. If the valve vibrates between open and closed positions, it capacity will be impaired and also its ability to regulate accurately. The motor which operates the main valve is subject 'tomoderate pressure, and shifts the valve a full stroke in response to a pressure change of only l p. s. i. To take the two usual settings, the pressure ranges in the motor are as follows:

Open Closed pound setting The lower the normal motor pressure the larger the motor vent port can be, and the smaller the clearance above the piston, the closer motorpressure will follow the action of the throttling inlet valve.

To take advantage of these characteristics it is essential to have a throttling inlet valve with superlative characteristics. To attain these the invention provides a ball valve mounted in a carrier which floats on the face of the diaphragm. This valve is inherently self-centering. A light spring urges the valve assembly against the diaphragm and so maintains its centered position. The valve has a conical seat of large effective diameter relatively to the size of thefiow port which it controls. As a consequence the valve lift to open the port wide is very small, actually only 0.00036". From this it follows that functional change of length of the regulatory adjusting spring, and consequently variation of spring stress can be small. For example, with a spring which changes only 0.6 lb. per 0.0001" compression, the change caused by 0.00036" compression is small, i. e. 0.00084 of 258# the spring stress for p. s. i. To an extent not anticipated, the scale of the adjustable regulatory spring is critical. Scale is the rate at which spring resistance builds up with deflection. If it is high, the spring is said to be hard and if it is low then softf Remembering that the pressure established by the main valve affects the diaphragm, which moves the adjustable inlet valve, and this in turn modifies the adjustment of the main valve, one sees that there is a closed cycle of interdependence. Proper timing will give smooth (gradual) action; bad timing will cause hunting. Using a diaphragm of 2.338 sq. inch effective area which to regulate at 110 p. s. i. requires a spring loading of 258#, it is practicable to select by a simple series of trials a spring of the right degree of hardness. Within a moderate range of hardness performance is excellent but if the spring is too hard or too soft, a hunting tendency may result. The significant point here is that there is a considerable and easily deter.-

mined range between hard and soft in which satisfactory action can be had.

Another detail of importance is the cylinder volume including clearance space above the single acting piston of the motor. It is desirable that this volume be small because this accelerates response but some clearance is desirable for cush ioning effect. The volume above the piston when the valve is closed is only 0.86 cu. in. The pilot is optional. The body is formed with two alter-- natively usable mounting faces and each of these has an optionally usable pressure connecting .port. Thus the widest choice as to connections is afforded.

V The commercial embodiment of the valve which has attracted much attention because of its remarkably precise functioning will now be described in detail as the means for explaining :1

.theimportant characteristics of the invention. In the drawings:

Fig. 1 is a plan view of the complete feed valve. Fig. 2 is an axial section on the line 2--2 of Fig. 1.

.V Fig. 3 is a section on the line 33 of Fig. l.

Fig. 4is a section on the line 44 of Fig. 2 but drawn on a larger scale than Fig.2.

. Fig. 5- is a diagram of the ball inlet valve and its seat.

Fig. 6 is a section taken on the irregular line .6-6 of Fig. 3.

Fig. 7 is a section on the irregular line 1-1 of Fig. 3." V

Fig. 8 is a fragmentary view similar to a portion of Fig. 2 showing a modification.

Asa rule feed valves are mounted either on the engineer's brake valve or on a pedestal or bracket on which the engineers brake valve is mounted. There are two typical mountings in one' of which the inlet connection is to the left and the outlet connection to the right and in the other of which the position of these two connections is precisely reversed. To permit a single feed valve to be mounted under either set of conditions, the main body of the valve, which is generally designated by the reference numeral -I I, is provided on opposite sides with distinct mounting faces I2 and I3, see particularly Figs. '6 and '7. Each mounting face has a flange with holes I4 for the mounting studs customarily used.

As shown in Fig. 6 (see also Figs. 2 and 3) the body H is formed with a horizontal partition I5 in which'there is a counterbored and threaded;

aperture to receive a stainless steel valve seat bushing generally indicated by the numeral I6.

This bushing is visible in Fig. 6 in which the line of section passes above the valve seat but'is not visible'in Fig. 7 because the line of section passes below' the valve seat. 'The lower end of the bushing is threaded and the bushing is screwed to its'seat in the counterbore.

" As clearly shown in Figs. 6 and 'Z'there are on the mounting faces I2 and I3 inlet connections I! and I8 both of which lead to the space I9 below the partition I5 and valve seat I6. Similarly, there are outlet connections 2I and 22 which lead to the space above the partition I5 and valve seat I6. If the mounting face I2 is used, the connections I8 and 22 are plugged. They are threaded for that purpose as shown. Similarly, if the mounting face I3 is used, the connections I! and 2| are plugged.

As best shown in Fig. 3 there is on the mounting face I2 a connection 23 shown in Fig. 3 as closed by plug 24. If the mounting bracket has a control port, the plug can be removed. Similarly, the mounting face I3 has another control port 25 also shown closed. by a plug 26. The usual control connection is indicated at 21. All three control connections 23, 25 and 21 lead to the space in front of the control diaphragm as will be explained. Only one is used at a time, the two not in use being plugged. Thus, Fig. 3 is drawn on the assumption that connection 21 is the one to be used. So far as is material here the important point is that any one of the three control connections can be used depending on the type of connection desired. The valve can be mounted right-handed or left-handed without change of function and with either mounting can have an external connection at 21 for the control line incases where that is desired.

The body II has'an open top closed by a cap 28 held by machine'screws as clearly shown in the drawing. The cap seals against the gasket 29 and the gasket seals both on the body I I and also on the upper margin of the motor cylinder 3|.

' The motor cylinder is formed integrally with a hub 32 which seats on a gasket 33 mounted in an annular rebate formed in body II as clearly shown in Figs. 2 and 3. A portion of the hub 32 extends downward and forms a skirt 35 which enci'rcles'the valve head 36 when the valve is open.

The valve 36 which coacts with the seat I6 is pinned to the lower end of a stem 31 which is pressed into the piston II and peened over. The stem is counterbored from its upper end and is threaded at 38 to receive a piston puller. When the piston is fully depressed, the valve 36 moves down far enough to carry the pin which attaches it to the stem below the lower margin of the skirt 35, the removal of the pin being necessary to withdrawal of the piston. The stem 31 is guided in the guideway formed in the hub 32. A coil compression spring 39 reacts between the hub 32 and the piston 4|. The piston II is the moving element of the valve actuating motor and works in the cylinder bushing 3|, a seal being afforded by a marginal packing ring which is shown in the drawings and is of ordinary commercial form. A The cylinder bushing hub and the piston and valve can be withdrawn as a unit through the top of the body II after the cap 28 has been removed. After the above components have been removed from the body, it is a simple matter to depress the piston II and remove the pin which connects the valve 36 with the stem 31.

While the construction above described is functionally similar to the constructions heretofore used in Model F feed valves, it aifords one important advantage. The valve seat I6 is completely unobstructed so that a clear flow path is afforded to it from every direction. This reduces'the tendency for burned oil to accumulate on or near the seat. The use of low grade lubricating oils in air brake compressors is a source of perennial difliculty 'in the maintenance of regulatory valve mechanisms and the change above described has the effect of eliminating one focal point for trouble. Another change which is not clearly apparent from the drawings is the fact that the clearance space above the piston 4| is kept to the practicable minimum for reasons already stated.

Refer now particularly to Figs. 2 and 4. To the left of body I] as viewed in these figures there is an internally threaded circular flange 44. The threaded opening in this flange leads to a shoulder 45 against which is mounted a thin flexible brass diaphragm 46. This is the regula tory dia hragm. The diaphragm is marginall clamped bya threaded annular clamping member 41 which is relieved slightly as indicated at 48 to permit a moderate out'ward (left-hand) fiexure of the diaphragm 46. Immediately to the right of the diaphragm is a cylindrical chamber in which is mounted a felt annulus 49 which serves as a filter to protect the inlet port hereinafter described from dust. A circular groove is cut around the right end of the chamber. It will be observed that this groove 5| is completely bridged by the felt filter 49.

As best shown in Figs. 2 and 3, the connections 23, 25 and 21 each lead to the groove 5| and thus through the filter 49 to the space at the right of the diaphragm 46. it follows that the control pressure communicated through whichever one of these connections is in use reacts on the inner face of the diaphragm 46 and thus urges the diaphragm outward. I

To resist this tendency anadjustable loading spring 55 reacts on a thrust plate 52 which is seated on the outer face of the diaphragm and is guided in the member 41. A shoulder at the end of the guideway is provided to limit positively the outward motion of the plate 52. e

A tubular stem 53 with handle knob 54 is threaded into the member'47 and encloses the loading spring 55. This spring reacts at its outer end on the knob 54 and at its inner end on the thrust member 56 which has a thrust nose engaging a socket in the outer face of the plate 52. By turning the knob and thus screwing the stem 53 in or out, the stress on the spring 55 is adjusted.

From the space above the piston 4| a passage 5'! leads through the cap 28 and body II to a chamber 58 opposite the center of diaphragm 46. The passage has a length which is many times its diameter and has, pressed into the passage 51 near its juncture with the cylinder space above piston 4|, a choke 59 whose port is 0.040" and whose length is approximately A". Thus, the choke divides into approximately equal volumes the clearance space above the piston and the space within the passage 51. Bearing in mind the fact that compressed air is an elastic fluid, a choke so located has very marked damping characteristics. v

Fig. 8 illustrates the possibility of omitting choke 59. The passage 5'! alone exerts a pronounced damping effect even without the choke. The choke is a new feature added in the present continuing application.

Leading from the chamber 58 is a choke fitting 60 whose port is 0.0225 diameter and about in length. It discharges into the space within housing H around hub 32. This space is vented to atmosphere at 6|. There are also vents 62 from the space below piston 4 I.

Threaded into a passage extending between chamber 58 and the diaphragm chamber is the inlet valve seat 63. This has an axial bore 54 which is 0.076" diameter, leading from a con cave conical set. The apex angle of the cone is and the base is so large that the ball valve 65 which is 4" diameter seats fairly on the conical surface as diagrammed on an enlarged scale in Fig. 5. This detail is considered important as assuring smooth flow even under throttling conditions. As will be readily appreciated the flow path gradually contracts and expands as the air passes the ball so that eddying and consequent fluttering of the ball are avoided.

While the details may seem minor at first glance, the location of the supply and vent in directly opposed relation at the remote end of a. choked passage leading from the motor is a vital factor in the attainment of the remarkable stability of operation which has been attained.

In the former embodiments the vent port led through the piston or through the cap and the inlet valve was not designed for particularly smooth throttling. The attendant constant now to the motor and resonant effects, probably starting with a fluttering diaphragm valve, lead to hunting by the main valve motor.

The ball valve 65 is confined in but protrudes from a socket in carrier 66. This is not attached to diaphragm 46, but has a lapped flat rear face which overlies a considerable area at the center of the diaphragm where the latter lies flat on thrust plate 52. The valve carrier readily slides to a centered position as the valve engages its conical seat. A coil compression spring 61 holds the carrier against the diaphragm and affords frictional retention in its centered position. One end of the spring encircles the boss in which the ball-socket is formed, and the other is held centered by a peripheral flange 68 on seat member 63.

Brake pipe pressure acting on the right-hand side of the diaphragm 45 urges it to the left against the resistance of the loading spring 55. If brake pipe pressure is above normal, the diaphragm will be forced back, the valve 65 will be unseated and air will flow past the valve 65 to the chamber 58 which is vented at a constant rate by the choke 59. In this way there is continuously developed in chamber 58 a varying pressure which is a function of brake pipe pressure.

The pressure so developed in chamber 58 is communicated through passage 51 to the space above the piston 4|. When the choke 59 is used, as is the case in the preferred construction, the communication just mentioned is controlled by the choke.

The positions of piston 4| and connected valve 36 are determined by a balance between the pneumatic pressure acting downward on the piston and the upward reaction of spring 39 which, of course, varies according to the position of the piston. Doubtless there is some disturbance of the balance by air flowing through seat I 6 and past the valve 36. Experience with valves of the Model F type shows that cyclic pulsations of pressure tend to occur above the piston 4| and in prior commercial valves these pulsations appear to be self-perpetuating. The effect of such pulsations is to impair the precision of pressurecontrol and reduce the maximum flow capacity of the main valve.

To overcome this difficulty, the first effective step was the location of the supply port 64 and the bleed port 65] at the remote end of the slender passage 51 whose damping-efiect was sufficient to suppress almost completely and under almost all conditions the self-perpetuating characterchoke 59 which is the important new feature disclosed for the first time in the present application. A choke located as shown in the drawings (see Fig. 2) does more than increase flow restriction. It separates two elastic air volumes, one of which is above the piston 4| and the other of which is between the choke 59 and the chamber 58. The damping eifect is virtually complete.

As a consequence, the main valve moves smoothly and without pulsations. It remains wide open until brake pipe pressure approaches within one pound of the setting of the feed valve and then closes gradually. The precision of control is such that the range is usually within p. s. i. The poorest performance observed under commercial conditions is within 1#. This contrasts with prior art valves many of which start to throttle when brake pipe pressure approaches within 3 to 6 pounds of its setting and the control range is usually between 1 and 2 pounds.

In the foregoing specification a number of dimensions have been given. They are illustrative merely. While the particular arrangement illustrated in the drawings ispreferred, modification within the scope of the invention obviously is possible. r

I claim: 7

1. In a pressure-regulating feed valve of the type in which the pressure in the motor of a pressure-motor-operated main supply valve is regulated by'two orifices, one of which is a vent and the other of which is a fiuid pressure supply, and one of which is variably throttled by valve means responsive to the pressure of the discharge from the main valve, the improvements which comprise locating said two orifices at the remote end of a passage which communicates with said motor through a constriction, and constructing the valve means which controls the variably throttled orifice as a concave right conical valve seat encircling said orifice and having a coacting valve formed with a spherical surface adapted to close against said seat, the valve and seat being relatively so dimensioned that they engage when closed on a circle of tangency whose diameter is a substantial multiple of the diameter of said orifice, and

materially less than the maximum diameter of said seat.

2. In a feed valve of the type in which a main valve biased in an opening direction is closed by a pressure-motor subject to a pressure controlled by a constantly open bleed port and a supply valve spring-biased in a closing direction and urged in an opening direction by a diaphragm subject to the regulated pressure, the improvements which comprise constructing the valveoperating motor with the minimum practicable clearance and with a low displacement and locating the diaphragm-operated valve and its related bleed port close to one another at the remote end of a passage connected with the motor, said passage being of such length and cross-section as to afford a substantial flowdamping characteristic, the diaphragm-operated valve being in the form of a sphere which seats against the conical surface of a right conical concave seat on a circle whose diameter is a substantial multiple of the diameter of the seat port controlled by the valve, whereby the lift of the spherical valve to its wide open position is minimized and the flow path past the valve in all its open positions is characterized by a crosssection which gradually reduces and then gradually increases.

3. A pressure-regulating feed valve comprising in combination a main supply valve; yielding means biasing said valve in an opening direction; a piston-motor arranged to move said valve in a closing direction, said motor being characterized by a clearance space which is small relatively to the total displacement of its piston; means enclosing a regulatory chamber which approximates said clearance space in volume; a flow restrictor affording a connection between the regulatory chamber and the motor; means for developing a range of pressures in the regulatory chamber, comprising two restricted connections, one a fluid pressure supply connection leading to and the other a vent connection leading from the regulatory chamber; and regulatory valve means responsive to pressure at the discharge side of said main valve and arranged to throttle one of said connections, the last named valve means comprising relatively movable valve and seat elements formed with opposed conjugate surfaces, said surfaces being so related that throughout said range of relative motion the cross-section ofthe flow path between them when considered with reference to the direction of flow, first diminishes gradually and then increases gradually, whereby energy losses and resulting generation of pressure pulses are minimized.

ERWIN C. VROMAN.

r REFERENCES CIITED The following references are of record in the file of this patent: 4

UNITED STATES PATENTS Number Name Date 654,569 Hogan July 24, 1900 FOREIGN PATENTS Number Country Date 28,832 Austria June 25, 1907 507,293 Germany Feb. 20, 1932 147,057 Austria Sept. 25, 1936

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