US2777029A - Fluid actuated switch - Google Patents

Description

Ink. 3- .L

Jan. 8, 1957 H. LANGSTROTH FLUID ACTUATED SWITCH Filed Oct. 28, 1953 2 Sheets-Sheet 1 HALL L'ANGSTROTH XQl/ QJO 1W ATTORNE Jan. 8, 1957 H. LANGSTROTH FLUID ACTUATED SWITCH 2 Sheets-Sheet 2 Filed Oct. 28, 1953 I011 l6 I7 Fig.3

29' Fig. 5

INVENTOR HALL LANGSTROTH BY C ATTORNE United States Patent FLUID ACTUATED SWITCH Hall Langstroth, Riverside, Conn.

Application October 28, 1953, Serial No. 388,749

6 Claims. (Cl. 20083) This invention concerns a piston-type pressure sensitive switch which is responsive to fluid pressure. More specifically, this invention concerns a pressure sensitive switch which is useful at very high fluid pressures at which it will operate within a very small range of pressure tolerances.

In the prior art various types of fluid pressure responsive switches have failed under very high pressures. Those switches which have been used have suffered from various disadvantages, including short life.

Certain switches have proved valuable and are preferred up to moderately high pressure levels. These switches have employed, as a pressure barrier and actuating part of the switching mechanism, a flexible diaphragm composed of resilient fluid tight material such as rubber. In such switches, however, at relatively high pressures, the flexible fluid tight diaphragm material employed is no longer able to withstand the forces to which it is subjected. Observation indicates that failure usually occurs when the fluid tight diaphragm breaks or shears against adjacent solid switch parts, particularly against the end of the piston itself.

It has been necessary to substitute flexible metallic members for resilient fluid tight members in very high pressure applications. Use of the flexible metallic members necessitates a soldered joint of some sort in order to obtain fluid tightness. Unfortunately the brazed joints or seams often fail under the high pressures that they experience. Moreover, the flexible members under the effects of high pressure tend to lose their flexibility and obtain a permanent set.

The fluid actuated, pressure sensitive switch of the present invention is capable of operating at pressures much in excess of those at which presently known switches can operate. Nevertheless, in spite of its ability to withstand high pressures, the switch may be made extremely sensitive, so that it will respond within a very small range of tolerances to any predetermined fluid pressure. At the same time this novel switch may be made compact, lightweight, fluid tight and of extremely simple construction.

The switch of the present invention is useful at higher pressures than prior art switches despite the fact that it employs a fluid tight flexible diaphragm. The diaphragm of the present invention, like the diaphragms used in the prior art low pressure applications functions principally to provide a fluid tight barrier. In order to obtain a fluid tight barrier at the present state of the art, it is necessary to employ a diaphragm material having very low tension or shear strength in comparison with the pressures at which the switch will operate. In the present invention, however, the diaphragm material is prevented from shearing against surfaces having sharp corners or edges and rough surfaces and from deforming to the point where it stretches thin and breaks. The means preventing shearing and/or excessive deformation includes a secondary resilient deformable non-compressible member which is resilient but harder and less resilient than the diaphragm. This secondary resilient member is preferably disc-shaped. The location of this resilient member between the end of Patented Jan. 8, 1957 the piston and the diaphragm prevents the diaphragm from shearing against the edges of the end of the piston.

Shearing may, of course, occur inlocations other than at the end of the piston. It is possible in accordance with the present invention to employ more than one secondary resilient member and to employ such members in locations where shear might otherwise occur. However, it is usually sufiicient to minimize the opportunity for shearing or breaking in regions other than around the end of the piston by use of a backing member against which the flexible deformable member covering the end of the piston may be terminated. This backing member preferably lies in a plane initially spaced from the adjacent surface of the diaphragm a distance in the order of the thickness of the secondary resilient member. Sharp edges between the first chambers walls and the backing member are avoided. Smooth contour surfaces and rounded edges of large radius of curvature are employed.

Structurally the switch of the present invention is built around a chamber having bounding walls. A piston is snugly accommodated at one bounding wall within an opening in said bounding wall. The piston is movable relative to the bounding walls in the direction of its extension through the opening, and this movement is restricted to a distance such that at one extreme the end of piston is essentially flush with the bounding wall and at the other extreme it protrudes slightly into the chamber beyond the bounding wall. A spring exerts a high pressure on the piston which determines the operating pressure of the switch, and this spring is required to urge the piston into the position in which its end protrudes into the chamber. A second opening is provided in another bounding wall in order to permit the entry of fluid under high pressure. A deformable resilient non-compressible diaphragm is arranged in the chamber across the first opening and arranged between the first and second openings so that under fluid pressure the diaphragm will be moved against bounding walls adjacent said first opening. Under the very high pressures at which the switch is intended to be employed the diaphragm assumes fluid-like characteristics and forms a fluid tight barrier that will prevent the flow of fluid through the first opening. Positioned between the end of the piston and the diaphragm and extending beyond the edges of the piston and into contact with the bounding walls of the chamber is a smooth resilient, essentially noncompressible member of harder durometer reading in the diaphragm selected to resist shear against piston and to resist flow between the wall and the piston at the high pressures encountered.

For a better understanding of the present invention ref erence is made to the following drawings:

Fig. 1 illustrates in vertical section one embodiment of the present invention showing the switch in the position it occupies before fluid pressure is introduced.

Fig. 2 illustrates a limited area of the section shown in Fig. 1 which shows the flexible diaphragm and adjacent regions of the switch as the fluid is introduced into the second chamber.

Fig. 3 illustrates in a vertical section similar to Fig. 1 the same switch when the fluid pressure finally overcomes the spring pressure.

Fig. 4 illustrates the region of novelty in a sectional view similar to Fig. 2 showing in simplified form the pre ferred embodiment of the present invention, showing the position its parts occupy before fluid pressure is introduced.

Fig. 5 illustrates the same region of the same switch shown in Fig. 4 showing the positions its parts occupy when the fluid pressure overcomes the spring pressures.

Referring now to Figs. 1-3, a pair of metallic blocks generally designated 10 and 11 provide the basic structure of the present invention. These blocks may be machine casting-s or any other suitable form. These blocks are advantageously made to have rotational symmetry, and the switch about to be described may he assumed to have rotational symmetry throughout except where it is expressly stated to be non-symmetrical. The blocks 10 and 11 define generally cylindrical chamber and provide bounding walls for that chamber. Within the chamber and held in place between blocks I and 11 is a flexible diaphragm 140i rubber, silicone rubber or other suitable, resilient, non-compressible material. Diaphragm 14- is intended to provide a fluid tight seal between two openings within the chamber which will hereafter be described and hence must be composed of a material which will provide a fluid tight seal between these openings even under very high pressure conditions. For convenience in hereafter describing the structure the chamber will be considered as divided into two parts, one chamber portion 12 is that side of the diaphragm remote from the fluid (i. e., the piston side) and the other chamber part 113 is that side of the diaphragm on which the fluid is introduced. This rubber diaphragm 14 maybe advantageously made with an enlarged annular edge 14a which is made to snugly fit the contour of surfaces between the blocks 16 and 11 and is so held in place. Many other ways of holding the diaphragm in place will, of course, occur to those skilled in the art and may be freely sub stituted in this switch. However, the particular configuration illustrated is particularly desirable as the enlarged edge 14a acts somewhat like an O-ring which by virtue of further deformation improves its sealing qualities the higher the pressure of the fluid. Plate 15 is designed to hold block 11 in place against diaphragm 14 and block 10. In order to accomplish its purpose plate 15 has a radial flange 15a which overlies the flange 11a of block 11. Block also has a radial flange 10a which opposes plate 15. An annular U-shap'ed channel 16 in the flange 10a of block it is provided to seat an 'O-ring 17 of toroidal form and of such shape and size that it tends to contact plate 15. Although the ring makes a fluid tight seal between plate and flange 10a, such a seal is unnecessary in view of the sealing qualities of diaphragm 14 and O-ring '17 is employed for its shock mounting or cushioning rather than its sealing qualities.

Extending into chamber portion 12 is the end of a piston member generally designated 19 which is closely engaged by the portion of the walls adjacent said piston 19. This piston is provided with a radial flange '20 against one planar surface of which bears axially arranged helical spring member 21. Spring member 21 extends between flange and closure means 22. Closure means 22 is threadably or otherwise adjustably engaged by the internal wall surface of block 11. Thistype of engagement makes stop 22 axially movable. By axial adjustment of the position 01'? closure means 22,- the pressure on spring 21 may be increased or decreased any desired amount, allowing for variation in the pressure exerted by spring 21. Various choices of material and dimensions for and of the spring also permit the variation in the pressure exerted by spring 21. The flange 20 is held in place by the pressure of spring 21 against a planar surface of inwardly directed radial flange 23 of block 11 extending from the sidewalls of chamber portion 12. Thus the pressure supplied the piston 19 through flange 20 can cause it to move no further toward diaphragm 14 than is shown in Fig. 1 because flange 23 acts as a stop means limiting the movement of said piston.

Movement of the piston 19 from the piston of Fig. 1 can only be away from the diaphragm 14 and it can only be axial in direction because the internal circumferential bearing surfaces of flange 23 and of closure means 22 tend to bear against cylindrical surfaces on the piston and prevent motion in any other direction.

This piston itself does not contact the resilient diaphragm'. Rather the diaphragm is contacted in this instance by a disc 26 offlexible non-coznpressilfrle material of harder durometer reading than the material of the diaphragm 14. The material of disc 26 is chosen for its ability to resist wear rather than to make seals. Various plastic materials such as those known by the trade names Teflon and Kel-F, for example, may be employed for disc 26. Disc 26 must be of such material that it will be able to withstand all wearing action of piston 19 under pressure exerted upon it by diaphragm 14. Disc 26 must be sufficiently resilient and flexible to deform in such manner as to mold itself around the end of the piston and it must do so in such a manner as to expose a surface of smooth contour to the diaphragm. It must also be sufliciently resilient and yielding under pressure to avoid materially increasing the effective area of the end of the piston 19. Obviously, an increase in said effective area must be taken into consideration in calibrating the switch. A rigid metal member if substituted for disc 26 would be bent to cup shape in which shape it would retain a permanent set.

The edges of disc 26 are made to terminate on backing member 27 which is part of the bounding wall of the chamber and which in this case is composed of material which is slightly compressible. Material which may be used with success for this purpose is steel wool or other metallic wools or sponges or other materials exhibiting a diminishing compressibility. This compressible material in this application must be compressed to the point where only a small additional amount of compression can take place. In order to hold backing material 27 in place, a solid rigid backing plate 28 is employed, and it, with the side walls of the chamber and the diaphragm, forms an'unyieldin'g compartment with one movable wall. Since under the conditions of high pressure to which the diaphragm is subjected the material of the diaphragm, by the very property which makes it an excellent high pressure seal, would flow into the spaces between the strands of metallic Wool, it is necessary to cover the backing 27 with a cover 25 which does not have coarse fibers or strands between which the material of the diaphragm might flow. Felt makes an excellent cover 25 for this reason. This cover should be flexible but, because it is backed by the backing material 27, it need not be exceedingly strong. Because of the relatively tougher nature of disc 26 cover 25 is advantageously made to extend between the disc 26 and the diaphragm 14 where it will not be subjected to wearing forces.

A small orifice 29 is provided leading into the second chamber portion 13. A larger opening 30 may be threaded to receive the threaded end of a pipe or other fluid containing member connecting the switch and the high pressure "fluid system. As pressure is increased in the system, the fluid will pass from the region of the line conmotion 30 through orifice 29 into chamber portion 13. Orifice 29 is employed to damp out the efiect of sudden fluid surges. As shown in Fig. 2 the fluid pressure will gradually depress the resilient member causing first deformation of cover 25 and then of disc 26 (not shown deformed). Then, as shown in Fig. 3, it will finally overcome the pressure of the spring causing the piston to be driven upward away from the second chamber and toward contact closing means.

Upward movement of the piston 29 is limited by flange 31 on said piston which, at one extreme of its movement, will abut flange 23. The short amount of movement involved is enough to cause an upward movement of the lever arm 32 pivoting around the hook type fulcrum supplied by'member 33 which is aflixed to block ll. As the piston 19 rises and bears against lever member 32 in opposition to light spring 34, which is connected between tab 35' on block 11 and arm 32, the movement of lever 32 drives contact 36 upward and into contact with contact 37 (see Fig. 3). Contacts 36 and 37 are connected to opposite sides of a circuit so that their mutual contact completes the circuit. It will be obvious that members 32--37 are not of rotational symmetry.

The method of opening and closing the switch described and the contact arrangement, etc., are, of course, by way of example. Many other ways of using the movement of piston 19 to open or shut circuits will occur to those skilled in the art and are intended to be within the scope of the present invention.

By adjustment of cap 22, as previously mentioned it is possible to set the operating pressure of spring 21 at various amounts, differing slightly from other settings. Within small limits of tolerance, the pressure applied by the piston will overcome the pressure of the spring as soon as it exceeds said pressure. It is possible to calibrate the position of member 22 to correspond to different pressures so that the switch may be operated within small tolerances of a variety of pressures selected by the position of member 22.

A more detailed consideration of the movement and action in the area of the flexible diaphragm is desirable. As previously noted the condition shown in Fig. 1 illustrates the switch before fluid is introduced into chamber 13. In this condition the diaphragm is depressed a maximum distance into the second chamber by the force exerted upon it by plunger 19, and by disc 26.

As fluid is introduced into the second chamber portions, the pressure of the diaphragm on cover 25 will almost immediately tend to compress backing material 27. The backing material 27 is selected to support the cover 25 slightly above the edge of block 11 which would otherwise be exposed to diaphragm 14. Because cover 25 is completely flexible, it is easily deformed under slight pressure. Backing member 27, however, materially limits the deformation of cover 25. Disc 26 although a flexible resilient member, is of relatively hard durometer reading material which cannot be easily deformed as can the material of diaphragm 14. Eventually, however, even disc 26 is deformed under the extremely high pressure encountered in this switch mechanism. Although it is not shown in a drawing, it will be realized that the disc 26 is first deformed against the backing material 27 in much the same manner as cover 25 had been deformed so that only that portion of the disc covering the end of the piston resists deformation. As a result the end of piston 29 is left approximately the same in area as it would be without the disc 26. However, the covered end of piston 19 does not have the sharp edges which it would have without disc 26. Disc 26, in other words, provides a surface of smooth contour over the end of the piston extending to the plane of the backing material 27 against which diaphragm 14 cannot shear. As pressure is increased, the backing material 27, which is still slightly compressible, is gradually completely compressed, at which point the surface of cover 25 is at almost the same level as the edge of the sidewalls of chamber 12. Finally, the fluid pressure becomes suflicient to overcome the spring pressure and, as the piston is urged upward at this point, the disc 26 is flattened across the end of the piston and against the backing material.

It will be appreciated by those skilled in the art that a metallic diaphragm soldered in some manner within a switch and subjected to extreme pressure will be subjected to failure by rupture of the solder joint, bursting of the thin diaphragm itself or obtaining a permanent set in a useless or undesirable shape. The diaphragm of the present invention, on the other hand, provides an improved fluid tight joint as pressure is increased. It is not able to shear or burst because it is backed by a surface of smooth contour which limits its stretching and provides no sharp edges against which the diaphragm can shear. Finally, at extremely high pressures the diaphragm of the present invention itself acts very much like a fluid and will not for this reason obtain a permanent set.

Many variations on the present invention will occur to those skilled in the art. For instance, the structure as shown in Figs. 4 and 5 illustrates one modification of the invention which is highly useful. This modification is perhaps the preferred form of the invention because of its simplicity. In describing this modification the numbers corresponding to the numbers in the first described embodiment of the invention will be used with the addition of primes thereto to indicate pieces and parts similar to those used in said first described embodiment.

In the preferred embodiment of Figs. 4 and 5 two blocks are fitted together. In this instance, block 10' is coupled to block 11 by threaded engagement between parts thereof. As before, the block 10 and 11 are hollow, providing chamber portions 13 and 12, respectively. Again, a flexible non-compressible diaphragm 14' is employed to provide a fluid tight seal between chamber portions 12' and 13. However, in this case said flexible diaphragm 14' is held in place between metallic backing plate 28' and block 10 because of the pressure exerted upon the diaphragm due ultimately to the threaded engagement of members 10' and 11. Through chamber portion 12' passes a piston member 19 which extends through a close fitting hole in plate 23 into contact with disc 26' which lies between the diaphragm 14 and the plate 28. Fluid has access to chamber portion 13 through duct 29' which connects it to a suitable connection for a pipe or other fitting from the fluid system. Piston 19 may be under spring pressure or other types of pressure, such as oil pressure, which pressure on the piston must be exceeded by the pressure in chamber portion 13' in order for the piston 19 to move. Again disc member 26 is composed of flexible non-compressible material of harder durometer reading than material of the diaphragm 14. Effectively the material 26' tends to provide a smooth contour as opposed to the sharp edges which would be offered the diaphragm by the piston. The diaphragm would shear in the event that the edges of piston 19' were exposed directly to it. The ideal disc under these circumstances would have greater flexibility toward its outer edges and less flexibility toward its center where it must resist shear. Plate 23 is provided with a shallow recess which will accommodate cap member 26. The side Walls of this recess should be made of smooth contour in order to avoid shearing the diaphragm against them. However, in any event, the side walls of this recess are relatively so shallow that there is little opportunity for damage to the diaphragm due to shearing action thereon.

A lubricant of moly coat, graphite or similar substances is valuable for use between the end of the piston and the disc to minimize Wear therebetween no matter what type of switch is employed.

Other modifications Within the scope of the present invention which might be conceived by one skilled in the art are possible. The object in each such instance is to provide a secondary flexible covering which protects the fluid tight diaphragm from sharp edges by providing a smooth contour surface over the otherwise sharp edges.

1 claim:

1. A high pressure, pressure sensitive switch comprising a chamber having bounding walls, a piston snugly accommodated at one bounding wall within an opening in said bounding wall and moveable a limited distance relative to said wall in the direction of its extension through the wall such that at one extreme of its movement the end of the piston is essentially flush with the bounding wall and at the other extreme said end pro trudes slightly into the chamber, means on the piston and on bounding wall to so limit the movement of the piston, a spring exerting high pressure on the piston to urge it in opposition to the operating pressure into the position in which its end protrudes into the chamber, a second opening in another bounding wall permitting the entry of fluid under pressure, a deformable, resilient, non-compressible diaphragm arranged in the chamber across the first opening and arranged between the first and second openings so that, under fluid pressure, the diaphragm will be moved against the bounding walls adjacent said first opening, said diaphragm assuming fluid-like characteristics and 7 forming a fluid tight barrier that will prevent the flow of fluid through the first opening, and a smooth, resilient, essentially non-compressible member of harder durometer reading than the diaphragm selected to resist shear against the end of the piston and to resist flow between the bounding wall of the chamber and the piston at the high pressures encountered positioned between the end of the piston and the diaphragm and extending beyond the edges of the piston and into contact with the bounding wall.

2. The high pressure switch of claim 1 in which the means limiting the movement of the piston is an outwardly extending flange on the piston which flange lies between opposed shoulders fixed relative to the bounding Wall through which the piston passes a distance beyond the region of snug accommodation of the piston at the chamber bounding walls in excess of the total distance of piston movement.

3. The high pressure switch of claim 2 in which the spring is a helical spring surrounding the piston and extending between a shoulder on the piston and a shoulder fixed relative to the walls of the chamber, which shoulder may be adjusted relative to the chamber walls to increase the amount of pressure applied by the spring to the piston.

4. A structure as described in claim 3 in which the exposed edges of the chamber walls of the chamber are made smooth in contour and too shallow to permit shearing of the diaphragm and the member separating the piston from the diaphragm is a smooth, flexible, resilient, essentially non-compressible disc of harder durometer reading material than the diaphragm.

5. A structure as described in claim 3 in which the wall portion adjacent the piston is slightly compressible but is in turn backed by a solid member which is essentially non-compressible, said slightly compressible backing extending from a portion of the chamber bounding walls to the piston, the flexible, resilient, essentially non compressible member being a disc of harder durometcr reading material than the diaphragm located between the piston and the diaphragm and extending into contact with the slightly compressible backing.

6. A structure as described in claim 3 in which the Wall portion adjacent the piston is slightly compressible but is in turn backed by a sol-id member which is essentially noncompressible, said slightly compressible backing extending from a portion of the chamber bounding walls to the piston and having its surface covered with a flexible cover, the flexible, resilient, essentially non-compressible member being composed of a disc of harder durometer reading material than the diaphragm and being located between the piston and the cover and extending into contact with the slightly compressible backing.

References Cited in the file of this patent UNITED STATES PATENTS 2,275,556 Rasmussen Mar. 10, i942 2,404,843 Huber July 30, 1946 2,655,573 Szwargulski et al Oct. 13, 1953 FOREIGN PATENTS 692,894 France Aug. 11, 1930

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