US2593602A

US2593602A - Control means

Info

Publication number: US2593602A
Application number: US680829A
Authority: US
Inventors: Pool William; Taylor William Ivan
Original assignee: Celanese Corp
Current assignee: Celanese Corp
Priority date: 1945-07-04
Filing date: 1946-07-01
Publication date: 1952-04-22
Anticipated expiration: 1969-04-22

Description

A ril 22, 1952 w. POOL ETAL CONTROL MEANS Filed July 1, 1946 m n 4 mm 2 8\ 0|.I .w x ,N 2 n! L 3 w w x 2 .3 u a m RR uw m\ Y 345... 7 m E F Af-rQRNEYS Patented Apr. 22, 1952 CONTROL MEANS William Pool and'William Ivan'Taylor, Spondon, near Derby, England, assignors to Celanese Corporation of America, :acorporation of.Del-

aware Application July 1, 1946, Serial No. 680,829 In Great Britain Jul-y 4, 1945 13 Claims.

. Thisinventi'on relates to control means and isconcerned with pressure sensitive control means comprising a peripherally supported diaphragm adapted to move under pressure differences between the two sides thereof. The invention is particularly, although not exclusively, directed to a valve for controlling fluid flow and sensitive to pressure differences between differentpoints along the path of 'flow of the fluid.

vA particular example ofsuch a valve is one in whicha pumping device is employed comprising two pumps inseries, the delivery of the first .pump being greater than that of the second, and in which surplus fluid from the first pump is returned to theinlet side .of the first pump under the control of a diaphragm-operated valve of which two sides of, the diaphragm are exposed respectively to thefluid pressures on the outlet sides of the two pumps, i. e. on the inlet and outlet sides of the second pump. By these meansxthe'pressures on the inlet and outlet sides of the second pump are maintained substantially equal, any difference between such pressures moving'the diaphragm and operating the control valve so as to by-pass a greater or smaller amount of fluid back to the inlet side of the first pump until the pressures are equalised. It is desirable that the diaphragms of such control valves should be extremely sensitive to small pressure difference in order that, whatever position the diaphragm may adopt, the out-ofbal-ance pressure necessary to deflect it into that position should be negligible vin comparison with the absolute value of the pressure on the two sides. On the other hand it sometimes happens that the diaphragm is subjected to a much greater pressure on one side than'on the other,

e. g. when starting up the pumping device or if the flow on the outletside ofzthe second pump should be obstructed, and such large pressure differences are apt to rupture the sensitive diaphragm or to deform it permanently and in such a manner as to reduce its efliciency.

It has now been found that, in pressure sensitive control meanssuchas valves of the kind describedabove, these difiiculties can be overcome or substantially reduced by using a com- ..pound diaphragm comprising a disc and aflat reinforcing ring clamped together attheir pe- .riphery, both the disc andthe reinforcing ring .being distorted'together by pressure on the face :arrangement is one comprising a disclin conjunction with a'ring which, at its inner edge,

is ,slightlyqspaced from the face of the disc. In

normal use, therefore, substantially the Whole area of the disc is exposed to the pressure of fluid applied thereto without interference by thereinforcing ring. On the other hand if the disc is distorted'towards the reinforcing ring by excessive pressure on the other side, the ring then comes into operation to'support the disc and prevent undue deflection or rupture thereof. The arrangement is most effectively produced by distorting the ring and disc together in situ, because in this way a suitably matched (but not identical permanent set of both the ring and the disc can be readily brought about. The disc is of sheet material of a; thinness appropriate to the sensitivity required. The ring may be of thesame thickness or it may be of thicker material.

It is generally desirable to limit the motion of the centre of the compound diaphragm in one or both directions. This may be done by means of a slightly domed rigid circular plate, centrally secured to the diaphragm and carrying a member or members adapted to come into contact with stop surfaces when the diaphragm has been deflected by the maximum amount desirable. When such a plate is employed on the same side of the disc as the reinforcing ring it is preferred that the clearance between the edge of the plate and the inner edge of the ring should be small so that, in its fully distorted position, substantially the whole area of the disc is backed and supported. either by'the reinforcing ring or the central plate. The use of such a domed plate,

:which limitsthe motion of the disc to a degree whichrincreases from just inside the inner edge of the reinforcing ring towards the centre of the disc, gives rise to a disc whosemaximum distortion isv just within the inner edge of the supporting ring, the disc within the line of maximum distortion being domed in the opposite direction. A similar plate, preferably of the same size, may be fixed to the other side of the diaphragm and, if desired, provided with a means to limit the motion of the diaphragm. While such a plate serves only to support the middle of the disc in a position offull deflection, the reinforcing ring affording no support. when the disc is deflected in this direction, it may be remarked that by reason of the annular distortion of the disc, the disc is stronger in this direction and less in need .of support. 7 I

In imparting to the disc and its. supporting ring their permanent set it is desirable that they should be assembled together, and with. any other restraining means employed for limiting the .motion of the diaphragm, e. g. the centrally mounted domed'plate referred to above, in order that the deformation of the diaphragm may be such as to cause it to receive the maximum of support from these members when it is fully deflected.

The distortion of the compound diaphragm may conveniently be done by applying to one side a fluid pressure greatly in excess of any pressure the diaphragm is likely to encounter in working conditions. Thus the entire device may be arranged in conjunction with relief mechanism adapted to relieve the pressure when it exceeds a certain value; in such a case the deflection may be effected under a pressure two or three times as great as that which the relief mechanism comes into operation. For example, if the maximum working pressure of the device is of the order of 300 to 400 lbs. per sq. inch, the pressure employed for distorting the diaphragm may be of the order of 1,000 lbs. per sq. inch. On the other hand'the range within which the device is designed to operate, as determined by the range of free movement of the disc, may be very much less than the pressure at which the relief mechanism operates, the sensitivity of the diaphragm made possible by the present invention enabling it to close or open the valve fully under a pressure range of 10 to 20 lbs. per sq. inch.

By way of example one particular form of apparatus provided with a diaphragm valve in accordance with the invention will now be described in greater detail with reference to the accompanying drawings which:

Fig. 1 is an elevation partly in section of a double-pump device provided with a diaphragm in accordance with the present invention, and

Figs. 2-4 show the diaphragm and valve arrangement in various stages in the course of their assembly.

The mechanism is a double-pump device of the kind described above, and comprises a metal block of generally rectangular form to the two opposite faces of which the two pumps 6, l are bolted. The block is divided into an upper and a lower half, which are fitted together and clamped. A deep cylindrical cavity 8 is formed in the upper part of the block and a similar cavity 9 is formed in the lower part, the two cavities 8, 9 registering with one another so as to form a cylindrical diaphragm chamber. The compound diaphragm It], It is clamped between the two parts so as to divide the diaphragm chamber across the middle.

A central passage l2 leads vertically away from the top part 8 of the chamber, and a central passage l3 leads away from the bottom part 9 of the chamber and constitutes the outlet from the pump device. Twohorizontal passages i5, IS on one side of the block 5 communicate respectively with the upper part 8 of the chamber and with the vertical passage i2, and the passages I5, [6 where they emerge on the face of the block 5, register respectively with the outlet and the inlet passages of the first pump 6. On the opposite face of the block two passages ll, !8 lead horizontally from the upper part 8 and lower part 9-, of the diaphragm chamber and these register respectively with the inlet and the outlet of the second pump 1. A further horizontal passage in the block 5, at right-angles to the four passages mentioned above, and indicated at 20, communicates with the uppermost of them, that is, the passage 16 registering with the inlet of the first pump 6, and the passage 20 constitutes the fluid inlet of the pump device. The two pumps 6, I are similar in form, and so of the same capacity when driven at the same speeds, but they are geared together with gears 2|, 22 of unequal size so that the first pump is driven faster than the second pump '1 and consequently delivers fluid at a greater rate.

The diaphragm 10, ll consists of a thin sheet metal disc [0 of about 1 inches in diameter and a flat supporting ring I I of sheet metal of the same gauge and of the same external diameter and having an internal diameter of inch. The disc and reinforcing ring are clamped together between the two sections of the block 5 containing the diaphragm chamber 8, 9 and, the chamber being of a diameter of 1 inches, the reinforcing ring I! extends into the chamber at every point of its circumference by 1%; inch. Centrally clamped to the disc [0, one above and one below, are two

thick plates

23, 24 of a diameter of .85 inch, each plate being domed on the face adjacent to the diaphragm to a radius of about 4 inches. The clamping of the

plates

23, 24 is effected by means of a screw 25 projecting from a hexagon block 26 and passing downwards through the two plates 23, Hand the diaphragm disc ii}, and screwing into a further hexagon block 21 disposed below the diaphragm. The lower hexagon block 27 is provided with four downwardly projecting stops 28 which engaged the bottom of the diaphragm chamber around the outlet passage 53 thereof. The stops 28 are of such a length as to prevent the diaphragm from being quite fiat; when they rest on the bottom of the diaphragm chamber the diaphragm is pressed upwards by 0.01 inch as indicated in Fig. 2.

The upper hexagon block 26 is formed with a flat projection 29 constituting a valve face. The central passage [2, leading vertically upwards from the diaphragm chamber is enlarged and screw threaded at its lower end, and in it is screwed a nozzle 30 whose edges are ground flat so as to constitute a valve seat against which the fiat valve face 29 of the upper hexagon block 25 engages. From the centre of the upper hexagon block 26 rises a stem 3! extending clear through the nozzle 30 and carrying at its upper end a piston 32 fitting the vertical passage i2 and lying above the horizontal passage 16 leading therefrom to the first pump 6. The upper end of the vertical passage [2 is closed with a screwed plug 33. The piston and its stem 3! serve as a guide to prevent tilting of the diaphragm l0, ll and the hexagon blocks 25, 21 secured thereto. When the diaphragm H], H is in its lowest position, with the stops 28 resting on the floor of the diaphragm chamber 8, 9 the clearance at the edges of the nozzle 30 is 0.012 inch.

Before being first assembled the disc l0 and its supporting ring ll are quite flat, and are only deflected, when the device is assembled, by the lower hexagon block 21 resting on the bottom of the diaphragm chamber 8, 9. The compound diaphragm in this state is shown in Fig. 2. When the device has been assembled a pressure of 1,000 lbs. per sq. inch is applied in the lower part 9 of the diaphragm chamber, in consequence of which the

valve

29, 30 in the upper part 8 of the chamber is completely closed and further the disc [0 and its supporting ring II are distorted into an annular bulge between the upper domed plate 23 and the wall of the chamber 8, 9, the middle of the disc l0 fitting closely in contact with the domed surface of the plate 23 and its edges in contact with the reinforcing ring II. This is shown in Fig. 3. Thepressure is sufficient to give the disc l0 and the ring H a permanent set, but the elasticity of the diaphragm is such that when the pressure is released, as shown in Fig. i, the valve surface 29 drops from its seat (the edge of the nozzle Si!) by about 0.092 inch so that the stops 28 beneath the lower hexagon block 21 are about 0.01 inch clear of the bottom of the diaphragm chamber. At the same time, the diaphragm disc It] lies clear of the reinforcing ring H and of the edges of the

domed plates

23, 24 above and below it. Consequently both surfaces of the diaphragm plate is are fully exposed to fluid pressure in the upper part 8 and lower part 9 of the diaphragm chamber, and the diaphragm is free to move sensitively to equalise the pressures in the two parts of the chamber by adjusting the clearance between the valve face 29 and the valve seat 36. After the distortion of the disc Ii] and its supporting ring H has seen effected, the correctness of the clearances can be checked by means of a gauge applied to the top of the piston 32 by removing the plug During the starting of the device pressure is first applied above the diaphragm, but the stops 28 below-the lower hexagon block 2? lim' the downward movement of the diaphragm and prevents its reaching and passing a flat posi tion. When the pressure in the lower part 9 of the diaphragm chamber is built up, the normal operating position of the diaphragm is a floating position with the valve face 29 clear of the nozzle 30 free from the door of the diaphragm chamber. If excessive pressure arises in the lower part c of the diaphragm chamber, e. g.

by blocking of the flow of fluid from the outlet E3 of the device, the reinforcing of substantially the Whole area of the diaphragm disc It by the upper domed plate 23 and the reinforcing ring H prevent further deformation of the diaphragm disc until pressure relief mechanism operates to throw out the pump drive.

Having described our invention, what we desire to secure by Letters Patent is:

1. A compound diaphragm comprising a disc of thin sheet material and a reinforcing ring of sheet material for superposition with said disc, said disc and said ring each being deformed from a plane in which its periphery lies, the deformation of any point of said ring being slightly greater than that of the corresponding point on said disc by an amount that increases towards their common centre.

2. A compound diaphragm according to claim 1 in which the maximum deformation of the disc is just within the inner edge of the ring and in which the part of said disc within said maximum deformation bulges in the opposite direction to said deformation.

3. A diaphragm assembly comprising a diaphragm chamber, a disc of thin sheet material extending across said chamber, a reinforcing ring of sheet material superposed on said disc, means for clamping together the edges of said disc and ring at the walls of said chamber so as to divide said chamber into two parts, said disc and said ring each being deformed from a plane in which its periphery lies, the deformation of any point on said ring being slightly greater than that of the superposed point on said disc by an amount that increases towards their common centre.

4. A diaphragm assembly according to claim 3 comprising means in the chamber for limiting the movement of the centre of the disc.

5. A diaphragm assembly according to claim 3 comprising a valve for the control of fluid flow disposed within the diaphragm chamber and operated by the motion of the disc.

6. A double-pump liquid-metering device comprising two pumps in series and a diaphragm assembly as claimed in claim 5, the two parts of the diaphragm chamber communicating with the inlet and outlet respectively of the second pump, said device having a by-pass passage between the outlet and the inlet of the first pump, the valve in said assembly controlling the flow of fluid through passage and being adapted to move towards its closing position on an increase of pressure on the outlet side of said second pump.

'3. A double-pump liquid-metering device according to claim 6 comprising, in the diaphragm a domed plate on each side of the disc and fixed to the centre thereof, and means for limiting the movement of each of the domed plates, the periphery of each of the domed plates lying just within the inner edge of the reinforcing ring.

8. A double-pump iic uid-metering device according to claim 7 wherein the valve for the control c1 fluid flow is in the form of a nozzle disposed in one part of the diaphragm chamber and adapted to co-operate with a fiat face carried by the domed plate in said part, opposite and close to the opening of said nozzle.

9. A diaphragm assembly coin rising a diaphragm chamber, a disc of thin sheet material extendin across said chamber, a reinforcing ring of sheet material superposed on said disc, means for clamping together the edges of said disc and rin at the Walls of chamber so as to divide said chamber into two parts, said disc and said ring each being deformed from a plane in which its periphery lies, the deformation of any point on said ring being slightly greater than that of the superposed point on said disc by an amount that increases towards their common centre, a domed plate fixed to the centre of the disc and means for limiting the movement of said domed plate.

10. A diaphragm assembly according to claim 9 in which the periphery of the domed plate lies just within the inner edge of the reinforcing ring.

11. A diaphragm assembly according to claim 9 comprising a second domed plate fixed to the opposite side of the diaphragm to the first, and means for limiting the movement of said second domed plate.

12. A diaphragm assembly according to claim 11 in which the periphery of each of the domed plates lies just within the inner edge of the reinforcing ring.

13. A diaphragm assembly according to claim 9 comprising a valve for the control of fluid flow in the form of a nozzle disposed within the diaphragm chamber and adapted to cooperate with a flat face carried by the domed plate opposite and close to the opening of said nozzle.

WILLIAM POOL. WILLIAM IVAN TAYLOR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,062,300 Pierce May 20, 1913 1,091,763 Pierce Mar. 31, 1914 1,273,534 Pierce July 23, 1918 1,294,486 Kuen Feb. 18, 1919