US 3075740 A
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Description (OCR text may contain errors)
Jan. 29, 1963 D. L. MclNTQsH 3,075,740
DIAPHRAGM VALVE Filed June 2, 1960 Il f- 15A ffy 5 i INVENTOR. ona/o/L MQ/n/osb yazw@ dn;
This invention relates to improvements in a diaphragm valve. More particularly it pertains to an improved assembly and diaphragm having a thin sheet plastic diaphragm molded from an aliphatic base polymer and a thick iiexible backing sheet therefor made of a rubberlike material and an arrangement of securing the diaphragm to the mechanism by which it is actuated.
Valves of the type to 'which this invention relates have a body with a substantially straight passageway therethrough which is interrupted by a transverse Weir whose concaved sur-face extends across the passageway and forms a seat for the diaphragm. The latter is clamped around its periphery between the body and a bonnet -mounted thereon which houses most of the working parts by which the diaphragm is moved toward or away from the Weir. At all times the diaphragm seals off the actuating mechanism from the uid owing through or standing in the body passage.
One of the elements of the actuating mechanism housed within the bonnet is a so-called compressor located adjacent to the diaphragm on the side thereof remote from the weir. When the valve is to be closed, the other actuating mechanism elements cause the compressor to advance towards the weir and bulge the diaphragm iirmly against the top concaved surface thereof, thereby shutting off all communication in the passage from one side of the weir to the other. To open the valve the diaphragm must be withdrawn from its contact with the Weir and bulged in the opposite direction. Diaphragms made of either natural or synthetic rubber compounds reinforced with a fabric are fairly thick and strong and are used successfully in the type of valves described above. However, since the diaphragms of either natural or synthetic rubber are not resistant to certain chemicals, such as acids, alkalies or strong solvents, they cannot be used in lines in which these chemicals are present. To overcome this diicu'lty recently diaphragms have been constructed of aliphatic base polymers such as Saran and polytetrailuoroethylene. The diaphragms constructed wholly of plastic material are not entirely satisfactory. Because if such a plastic diaphragm is made thick enough to provide the necessary strength required it does not have the required tlexibility. Thus recently diaphragms are being made of a thin sheet of the plastic material which is backed up with a rubber-like sheeting to strengthen the diaphragm.
While the thin plastic diaphragm and the backing are normally made of resilient material preformed with a bulge extending away from the weir, the resiliency of the material cannot be relied upon to cause it to return to the opened position when the compressor is withdrawn. Thus, an attachment between the diaphragm and the actuating mechanism whereby the diaphragm would be positively withdrawn from engagement with the Weir upon opening of the valve must be provided. This attachment has heretofore taken the form of a stud with its head embedded in the center of the plastic diaphragm and its shank extending outwardly therefrom on the side remote from the weir to engage into the compressor. Generally a hole was provided through the rubber-like backing through which the shank of the stud extends and engages the compressor. No contact of the plastic diaphragm with the compressor is provided other than through the stud embedded into the plastic material. With the shank ice of the stud engaged in the compressor, undue pressure is applied to the portion of the thin plastic gasket at the head of the stud. At times appreciable pressure is applied to the compressor to insure proper seating of the diaphragm on the Weir. When this is done the plastic material between the stud-head and the Weir is severely squeezed and also stressed so that after a number of operations of opening and closing the valve the plastic diaphragm will rupture at the stud-head.
To overcome the above diiiiculty it has been suggested that the diaphragm be mounted non-rigidly to the compressor. While a non-rigid attachment may overcome the diiculty of rupturing the plastic diaphragm at the studhead, it is undesirable due to the oating action obtained. At times it is desirable to control the flow rates by use of the valve and thus it is desirable to have a valve with positive action knowing that if the valve is turned a certain amount it can be expected that the diaphragm will be raised or lowered a given amount. A further disadvantage is that the method of attachment becomes complex and can only be used on large valves. Even in fairly large valves, the mechanism cannot be built very sturdily due to its complexity. While at times it is not necessary lto have a sturdy method of attaching the diaphragm to the rise, it does become critical when the valve is to be used in a vacuum system. In a vacuum system the diierential pressure obtained gives rise to a -force on the diaphragm tending to close it. Under these conditions a strong method of attaching the diaphragm to the compressor is necessary to keep from pulling the diaphragm from the compressor or rupturing its method of attachment.
It is therefore an object of this invention to provide a diaphragm valve wherein undue stress is not placed upon the head of the stud embedded in the diaphragm upon closing of the valve. A further object is to provide a diaphragm Valve wherein the diaphragm is attached rmly to the compressor so it can be actuated without any floating action. A still further object is to provi-de an improved assembly of a diaphragm, backing and compressor wherein the diaphragm is rmly attached to the compressor without placing undue stress on the diaphragm when ,the diaphragm is closed or actuated.
The above and other objects are accomplished, according to the invention, by-the improved assembly comprising a thin plastic `diaphragm having a stud with its head embedded in a boss onJthleUplastic diaphragm with the thread stem projecting; hflgbgss. The boss extends into a center opening inherii hferglike backing With the threaded stem of the stud'geigagiiigvthe compressor seating the boss of the plastic diaphruagm and the area of the backing adjacent to the central opening against the compressor surface. By the above assembly the diaphragm may -be actuated and closed Without producing undue stress on the plastic diaphragm at the head of the embedded stud. The diaphragm which is of a plastic material is less resilient than the backing. By having the boss of this less resilient material contacting the compressor, the pressure applied to the compressor is transmitted to the boss on the plastic diaphragm and `distributed over the diaphragm uniformly without loca'lizing the stress at the stud. Also by having the boss of the less resilient material contacting the compressor, positive action is obtained and no floating action is experienced as when the `backing sheet is between the compressor and the diaphragm as heretofore used. The resilient backing material used in support of the diaphragm engages the compressor surface at the area adjacent to the boss and thus the advantages of a resilient rubber-like material backing is fully realized.
The invention may be more easily understood by considering the speciiicationin conjunction with the drawings, in which FIGURE l illustrates a diaphragm valve to which the invention is related,
FIGURE 2 is a detailed illustration of the diaphragm backing and compressor assembly,
FIGURE 3 is a top view of diaphragm of FIGURE 2, and
FIGURES 4 and 5 illustrate modifications ofthe assemblyshown in FIGURE 2.
The valve shown in FIGURE l comprises a body 11 having a passageway therethrough which is intersected by a transverse Weir `12. A bonnet 13 bolted tothe body in which Ythe actuating-mechanism for the movement up and down of diaphragm 14 is housed. As shown in the drawing the actuating mechanism comprises a compressor 16 whichis attached toa threaded stud` 17 and engaging the threaded portion of the handle 18 which Vraises and lowers the stud by turning ofthe handle.
In FIGURE 2 the improved assembly usedl in the valve in FIGURE I comprising the compressor 16, diaphragm 14, andthe backing 155 is shown in detaih In Vthe improved assembly the diaphragm which is constructed of relatively thin materialhas a 'boss 20located at its center in 'which the stud 21 which engages the compressor is embedded. In the assembly,the boss `of the Vdiaphragm extends through the backing 1S and the top surface 22 'of the boss seats against the surface 23 of the compressor.
In'addition to the top'surface of the boss seating Vagainst the compressor `the top surface 24 of the backing sheet 15 adjacent to the opening through which the boss extends also is seated against the surface of the compressor. -In FIGURE 3 a top view of the diaphragm is shown.
Amodiication'of the improved assembly of FIGURE l 2 is shown in FIGURE 4. The boss 31 on the diaphragm shown in FIGURE 3 does not extend all the way through the backing 15 as in FIGURE `2. The compressor used in this assembly is made with a boss-like reduced section at the end 32 which lits into the center opening of the backing sheet and is seated against vthe boss of the diaphragm when the diaphragm is attached to the compressor. The top surfaceof the hacking sheet 34 adjacent -to the opening in thebaclcing is 'in Contact with the ared portion 35 of the compressor.
In FIGURE a further m odification of the assembly of FIGURE 2 is shownwherein the boss in which the stud used vfor attaching the diaphragm -to the compressor is appreciably thicker thanr the thiclness of the backing and extends in a recess 41 in'the compressor when the diaphragm is attached.
A method vof attachingjfjthecpmpressor to the mechanism used to raise zitiflipifdrtlpdihpressor is immaterial. The compressor mayjbelcre'wed onto stud 17, however it is preferred to haly'' the attachment made as shown in lFIGURE 1 by ins'gertion of 'a pin 19 in an aligning passageway in stud 17 and the compressor.
It will be apparent from the specification and drawing that the improved assembly herein claimed enables the diaphragm to be actuated and tightly closed without producing undue stress on the plastic diaphragm at the point the stud is embedded. By using a boss on the plastic diaphragm and having this boss in ccntact with the compressor the `diaphragm may be rmly seated without localizing the stress at the head of thestud. Since the backing is valso in contact with the surface of the compressor the advantages of the backing are fully utilized. This assembly is simple and thus may be constructed and used in small valves as well as large valves. Also due to the simplicity, the stud used may be of sufficient size and strength to hold the diaphragm opened even in vacuum operation. In vacuum operation a force is applied intending to close the diaphragm and if the attachment of the diaphragm to the compressor is not strong enough the diaphragm is torn loose from the compressor. In addition to the above advantages by having the boss in contact of the relatively non-resilient material of the plastic diaphragm in contact with the compressor, floating action that is normally obtained in the valve heretofore used is not present. Thus, when the rate of W has to be controlled by use of the valve, this is a distinct advantage. A turn of the handle will actuate the diaphragm a corresponding amount. In valves heretofore used, the backing malerial was inserted completely between the diaphragm and the compressor. Since the backing-is of resilient material a floating action was obtained. When the valve was closed tight the backing would be compressed. Thus, it was `'diilicult'to know whether the movement of the compressor obtained by turning of the valve moved the plastic diaphragm or was compressing or releasing the compression on the backing sheet.
What-is claimed is:
-1. In a diaphragm valve comprising -a body having substantially straight passageway therethrough intersected by a weir extending thereacross with an inwardly curved surface forming aseat for a diaphragm, and a bonnet assembly secured to said body housing having a compressor capable of being moved toward and away from the Weir, a thin plastic diaphragm su'iciently thin that in use a backing is required, and a rubber-like resilient backing sheet ytherefor with the edges clamped between the bonnet and the body, said plastic diaphragm being substantially less resilient than the backing sheet, said backing being interposed between the diaphragm and the compressor, the improvement of said bonnet assembly comprising said thin plastic diaphragm having a stud with its head embedded in a boss on the diaphragm with a threaded stem projecting from the boss and said rubberlike resilient backing sheet having a central opening therethrough, said boss on said plastic diaphragm extending into the central opening of the backing sheet with the threaded stem of 4the stud engaging the compressor, seating the boss on the plastic diaphragm and the area of the backing sheet adjacent to the boss against the compressor surface.
2. A diaphragm valve according to claim 1 wherein the boss on the diaphragm is substantially the same height as the thickness of the backing sheet.
3. A diaphragm valve according toV claim 1 wherein the `boss on the diaphragm extends only part way into the central opening in the backing sheet and a boss, provided on the lower end of the compressor, extends into thecentral opening in the backing sheet to contact the boss of the plastic diaphragm.
4. A diaphragm valve according to claim 1 wherein the boss on the diaphragm extends through the central open- -ing inthe backing sheet and is seated in a recess provided on the lower end of the compressor.
References Cited in the tile of this patent UNITED STATES PATENTS 2,397,373 Saunders Mar. 26, 12946 2,638,306 Fortune May 12, 1953 2,702,686 Fortune Feb. 22, 1955 2,767,956 Rubin Oct. 23, 1956.
FOREIGN PATENTS 547,515 Italy of 1956 1,161,540 France Mar. 24Il 195s