Automatic Pressure Regulator

There are many prior art automatic pressure regulators based upon various pressure sensing and pressure regulating means. These means include also rolling diaphragms.

All prior art pressure regulators are relatively complex which includes also pressure regulators predicated on the use of rolling diaphragms.

It is, therefore, the primary object of this invention to provide pressure regulators which are less complex than prior art pressure regulators, and may be manufactured at smaller cost than prior art pressure regulators.

Another object of the invention is to provide pressure regulators complying with the above requirements, predicated on the use of deep convolution rolling diaphragms, and requiring but one single such diaphragm.

Still another object of the invention is to provide rolling diaphragm pressure regulators of utmost simple design, wherein the gradient of the regulating spring is more or less compensated by changes of the effective area of the rolling wall of the rolling diaphragm.

Pressure regulators embodying this invention include a housing defining two passageways of which one may be referred-to as inlet and the other as outlet. The pressure at the inlet exceeds that of the outlet, and it is the pressure at the inlet that is regulated. A piston body is arranged inside the housing and defines an additional passageway which may also be referred-to as piston passageway. The radially outer portion of a deep convolution rolling diaphragm is affixed to said housing, its radially inner position is affixed to said piston body and its convoluted rolling wall is interposed between said housing and said piston body, i.e. positioned in the annular gap formed between these two parts. One side of the rolling diaphragm is acted upon by the inlet pressure, its opposite side is acted upon by the lower outlet pressure which may also be a vacuum or negative pressure, and the rolling wall is arranged to control the effective cross-sectional area of the aforementioned additional passageway or piston passageway. As a result, the rolling wall of the rolling diaphragm controls the flow of fluid or gas from the inlet to the outlet. The piston body is acted upon by spring means interposed between said housing and said piston body tending to cause said rolling wall of the rolling diaphragm to reduce the effective crosssectional area of said additional or piston passageway, or to close that passageway altogether. The annular space between the housing and the piston body has boundary walls of such configuration that the effective area of the rolling wall of the rolling diaphragm increases as said piston body moves against the action of said biasing spring means.

FIG. 1 is substantially a longitudinal section of a regulator embodying the present invention, the left part of FIG. 1 showing the constituent elements of the regulator in the fully closed limit position and the right part of FIG. 1 showing the constituent elements of the regulator in the fully open limit position thereof;

FIG. 2 shows a modified detail of the structure of FIG. 1 in longitudinal section;

FIG. 3 shows a portion of a simplified version of the structure of FIG. 1 in the same way as FIG. 1;

FIG. 4 shows the effective area of a rolling diaphragm device without spring gradient compensation plotted against percent of stroke;

FIG. 5 shows the effective area of a rolling diaphragm device with spring gradient compensation plotted against percent of stroke;

FIG. 6 is a flow regulator or flow controller embodying the invention; and

FIG. 7 is a safety relief valve or blow-off valve embodying the invention.

Referring now to FIG. 1 of the drawing, reference characters 1a and 1b have been applied to indicate the upper part and the lower part of a regulator housing. The upper part 1a defines an inlet passageway 1c and the lower part 1b defines an outlet passageway 1d. The inlet area 1e is situated adjacent inlet passageway 1c and the outlet area 1f is situated adjacent outlet passageway 1d. Reference numeral 2 has been applied to generally indicate a piston arranged and movable inside the housing 1a,1b whose parts are tied together by screws 3 of which but one has been shown in FIGS. 1 and 3. Piston body 2 defines an additional passageway or piston passageway allowing the flow of fluid from inlet 1c and inlet area 1e through piston body 2 to outlet area 1f and outlet passageway 1d. This additional or piston passageway and the flow of fluid through it have been indicated diagrammatically by the dash-and-dot line A. Piston body 2 includes a cylindrical skirt 2a forming a cylinder in which a piston 4 is arranged. Piston 4 is provided with an O-ring 5 and a piston rod 6. The latter is supported in the lower part 1b of housing 1a, 1b by transverse pin 7. Skirt 2a is provided with a lateral perforation 2b.

Reference character 8 has been applied to generally indicate a deep convolution rolling diaphragm. The radially outer portion 8a of diaphragm 8 is affixed to housing 1a, 1b and the radially inner portion 8b of diaphragm 8 is affixed by means of clamp 9 to the upper end surface of piston body 2. There is a clearance or substantially toroidal space 10 left between piston body 2 and the inner surafce of housing 1a, 1b. The rolling wall 8c of diaphragm 8 is arranged in that space 10. The upper side of rolling wall 8c is acted upon by the pressure prevailing in inlet area 1e and the lower side of rolling wall 8c is acted upon by the lower pressure prevailing in the outlet area 1f. It will be apparent from FIG. 1 that the rolling wall 8c is arranged to control the effective cross-sectional area of the additional fluid passageway indicated by the dash-and-dot line A.

The effective area of rolling wall 8c is equal to the annular area defined by its convolution. Since the lower portion 1b of housing 1a, 1b has a slanting inner wall section 1g, the effective area of the rolling wall 8c increases as the stroke of the piston body 2 in downward direction increases. This compensates at least in part for the increase of the action of spring 11 upon piston body 2 as the stroke of the latter in downward direction increases.

Assuming that the force of spring 11 upon piston body 2 increases .DELTA. p lbs when the stroke of piston body 2 increases .DELTA. s inches, and assuming further that the effective area of rolling wall 8c increases when the stroke of piston body 2 increases .DELTA. s to such an extent that the force acting upon the rolling wall 8c increases .DELTA. p lbs, this would mean that the increase of spring tension is fully compensated by the increase in the effective area of the rolling wall 8c. Under such conditions the force of spring 11 upon piston body 2 would be constant for all positions of piston body 2 or, in other words, the bias of piston body 2 would be an invariant. It is not necessary to go to such an extreme. It is, however, desirable to compensate in part the increase of the force exerted by spring 11 as the stroke of piston body 2 in downward direction increases which is effected by an appropriate increase of the effective area of the rolling wall 8c. As mentioned above, such an increase can be brought about by the slanting wall portion 1g. As an alternative, the same compensatory effect may be achieved by providing the piston body 2 with a slanting lateral wall.

FIG. 4 shows that the effective area in square inches of a rolling wall of a rolling diaphragm is independent from the length of the stroke of the piston body or a constant in case that the housing and the piston body define therebetween a toroidal space of constant inner and outer diameter.

FIG. 5 shows that the effective area in square inches of a rolling wall of a rolling diaphragm increases in proportion to the length of the stroke of the piston body in case that the housing and the piston body define therebetween a toroidal space of progressively increasing inner or outer diameter.

The skirt 2a with its perforation 2b and the piston 4 are delay means tending to stabilize the operation of the pressure regulator, i.e. tending to establish equilibrium conditions following variations in fluid pressure.

The structure shown in FIG. 3 differs from that shown in FIG. 1 only inasmuch as the aforementioned delay and stabilization means have been dispensed with in the former. Therefore, and since like parts are designated by the same reference characters both in FIGS. 1 and 3, the latter is self-explanatory.

Referring now to the path of fluid flow indicated by the dash-and-dot lines A, it will be apparent from FIGS. 1 and 3 that piston body 2 is provided with passageway means 2c situated at one end surface thereof for the admission of fluid under pressure from passageway 1c and inlet area 1e into piston body 2. Piston body 2 is further provided with orifice means 2d at a lateral surface thereof for the admission of fluid under pressure from piston body 2 to outlet area 1f and outlet passageway 1d. The effective cross-sectional area of said orifice means 2d is under the control of rolling wall 8c of rolling diaphragm 8. As shown to the left of FIGS. 1 and 3 orifice 2d is entirely obstructed by rolling wall 8c and as shown to the right of FIGS. 1 and 3 orifice 2d is entirely cleared so that no limitation of fluid flow through it is effected by the action of rolling wall 8c.

FIGS. 1 and 3 show embodiments of the invention wherein the extent of the orifice means 2d is 360.degree. . This does, however, not apply to the structure shown in FIG. 2.

In FIG. 2 the same reference characters with a prime added have been applied to designate like parts as in FIGS. 1 and 3. Hence FIG. 2 calls for a detailed description only to the extent that it differs from FIGS. 1 and 3.

As shown in FIG. 2, piston body 2' is provided with passageway means 2c' at the upper end surface thereof for the admission into it of fluid under pressure from inlet area 1e'. l Piston body 2' is further provided with a plurality of discrete orifice means 2d' at the lateral surface thereof for the admission of fluid under pressure from the inside of piston body 2' to outlet area 1f'. In FIG. 2 only one of said plurality of orifice means 2d' is shown. Orifice means 2d' are arranged in a circular pattern equidistantly spaced from each other around the lateral surface of piston body 2', and they have a width that varies in the direction of the longitudinal axis of piston body 2'. As shown in FIG. 2, orifice means 2d' is of substantially triangular shape. Its width is largest adjacent the upper end surface of piston body 2' and decreases progressively in downward direction. Such a geometry limits the rate of change of fluid flow through orifice means 2d' for a given increment of the stroke of piston body 2'. In the position of parts shown in FIG. 2 the rolling wall 8c' of rolling diaphragm 8 obstructs the upper wide portions of orifice means 2d', but allows an unimpeded flow of fluid through the lower portions of orifice means 2d' of relatively limited width. In other words, the position of parts shown in FIG. 2 corresponds to a position intermediate the limit positions shown in FIGS. 1 and 3.

The structure shown in FIGS. 1-3 have various applications. They are primarily differential pressure regulators used, e.g., to maintain a constant pressure at a given point of a gas distribution system. To this end inlet 1c is connected to a source of fluid under pressure, and outlet 1d is connected to a space of relatively lower pressure, e.g. to atmosphere. The structures of FIGS. 1-3 may further be used to maintain a predetermined vacuum in a vessel that is being evacuated by a vacuum pump, in which case passageway 1d is connected to the vessel that is being evacuated and passageway 1c is connected to atmosphere. The structures of FIGS. 1-3 are further applicable as blow-off valves or safety valves as will be explained below in more detail. In that instance the passageway 1c is connected to a vessel wherein pressure is to be maintained below a predetermined level, and passageway 1d is connnected to atmosphere.

Regarding the preferred nature of rolling diaphragms 8,8', reference may be had to my U.S. Pat. No 2,849,026; 8/26/58 for FLEXIBLE FLUID SEALING DIAPHRAGM and my U.S. Pat. No. 3,236,158; 2/22/66 for ROLLING DIAPHRAGMS, both disclosing rolling diaphragms particularly suitable for the purpose in hand.

In operation the tension of spring 11 is adjusted by regulating screw 12 until the desired pressure differential across the rolling diaphragm 8 is attained.

The force balance equation is Spring force = (inlet pressure -- outlet pressure) X (effective area rolling wall of rolling diaphragm). Any change of the difference (inlet pressure -- outlet pressure) results in an imbalance of the system. This, in turn, results in a change of flow conditions by the action of the rolling wall 8c of the rolling diaphragm 8. The change in flow conditions results in a new equilibrium or balance condition.

In order to compensate for the change of the force of spring 11 as piston body 2 changes its location in the process of opening and closing pressure control orifices 2d to maintain a constant pressure differential across diaphragm 8, the effective area of rolling wall 8c thereof is changed so that the increase or decrease in spring force for the new position is compensated by a corresponding increase or decrease of the effective area of the rolling wall 8c of diaphragm 8.

Referring now to FIG. 6, this figure shows a flow regulator or flow controller intended to maintain a constant difference in pressure between the areas P.sub.1 and P.sub.2. This means that the rate of flow across orifices o will be constant.

The structure of FIG. 6 has an inlet 1c" and an outlet 1d". Piston body 2" is suspended on spring 11" which, in turn, is affixed to regulating screw 12". The rolling diaphragm 8" comprises the three parts 8a", 8b" and 8c". Below piston body 2" a cup-shaped member 2a" is fixedly arranged which defines the passageway A".

The left side of FIG. 6 shows the valve in fully open position, i.e. fluid is free to flow from intake 1c", passageway or orifice o in piston body 2" and from there through passageway A" to fluid outlet 1d".

As shown to the right of FIG. 6 piston body 2" has been lowered to such an extent that it engages cup-shaped member 2a" and that the rolling wall 8b" of rolling diaphragm 8" completely obstructs the entrance of passageway A". In this position of piston body 2" no flow of fluid through orifice or orifices o can occur. A flow of fluid through o and A" will occur as long as P.sub.1 > P.sub.2 and P.sub.1 -P.sub.2 will be held constant as long as the above flow occurs.

FIG. 7 refers to a safety relief or blow off valve. It will be apparent that valves according to this invention are capable of gradually modulating a flow of fluid. In the extreme case shown in FIG. 7 the valve is bistable, i.e. it has only two positions, i.e. it is either fully closed or fully opened. This is achieved by making the characteristic of FIG. 5 sufficiently steep.

The left of FIG. 7 shows the fluid intake 1c'", the fluid outlet 1d'", the piston body 2'", the rolling diaphragm 8'", spring 11'", and regulating screw 12'". Piston body 2'" has an opening 2c'" in the end surface thereof. As shown to the left of FIG. 7 the rolling diaphragm 8'" completely obstructs passageway A'" leading to outlet 1d'". The position of parts shown to the left of FIG. 7 obtains as long as the pressure in space 1e'" is less than a critical value. If that value is exceeded piston body 2'" moves suddenly from the position shown to the left of FIG. 7 to the position shown to the right of FIG. 7, thus fully opening passageway A'".

It will be observed from FIG. 7 that the angles of the taper on the piston body 2'" and that on the lower cylinder body 1b'" are opposite. The former has been designated by the reference character X.sub.1 and the latter by the reference character X.sub.2. This causes a large increase of the diaphragm area as the piston body 2'" is moved against the bias of spring 11'". To be more specific, as the result of the above geometry the "pressure gradient" of diaphragm 8 exceeds the gradient of spring 11'", thus rendering the valve of FIG. 7 bistable.

In FIG. 1 the rate of change of the rolling wall of diaphragm 8 is solely due to the slanting wall portion 1g inclined relative to the longitudinal axis of the housing. In FIG. 6 and particularly in FIG. 7 the wall portions X.sub.1,X.sub.2 slant in opposite direction, piston body wall portion X.sub.1 converging in downward direction and cylinder body wall portion X.sub.2 diverging in downward direction. This geometry causes a more rapid rate of change of the force acting on the effective area of rolling diaphragm 8 than the change of the opposite force of spring 11 when the piston body and the spring are displaced equal distances.