US2747615A - Pressure responsive device having a slotted metal diaphragm - Google Patents

Description

K. TATE 2,747,615

PRESSURE RESPONSIVE DEVICE HAVING A SLOTTED METAL DIAPHRAGM May 29, 1956 2 Sheets-Sheet 1 Filed Feb. 25, 1953 wGE NOE

I H T E N N E K ATTORNEY May 29, 1956 K. TATE 2,747,615

PRESSURE RESPONSIVE DEVICE HAVING A SLOTTEID METAL. DIAPHRAGM Filed Feb. 25, 1953 2 Sheets-Sheet 2 FIG. 6

INVENTOR.

KENNETH L.TATE BY 9 a yaw ATTORNEY United States Patent BE NS V D Y Q HAVING A 'SLOTTED METAL DIAPHRAGM Kenneth L. Tate, Rochester, N. Y., 'assignor 'to Taylor Instrument Gompan'ies, Rochester, N. Y., a corporation' of New York Application February 25, 1953, Serial No. 338,658

3 Claims. (Cl.-137 784) V Thisinvention generally relates -to diaphragms for fiuid 'p'ressure responsive devices and'rnore'particularly to -diaphragms employed in connection with air operated devices or instruments of the force balance type.

For dependable operation of such instruments it is usually quite important that the'efi'ectivearea of the diaphragm remain constant fora travel of as much as 05030 inch. It is even more important "that for a given deflection the efie'ctive area'remain constant overa long period oftime and 'afterhaving'been subjected to a fairly Wide range of temperatures and pressures. 'In other Words, the diaphragm must be-highly repeatable to'p'erform the exacting function which is demanded of it.

In an effort to improve the conventional diaphragm madeof'fabric stock impregnated or covered with a coating of plastic material, it has been a common practice to form or mold a corrugation in the unsupported area of the diaphragm. Such a deeply formed corrugation tends to improve the constant area characteristic of the thediaphragmalthough the repeatability has 'not beenimproved to any substantial extent thereby inasmuch as the tendency to Stretch still remains as aninherent characqeristic of this type of material.

Insofar as repeatability is concerned, this objective could =be obtained by the employment 'of a 'metallic'sheet instead'of a plastic coated fabric. "Io ob'tain'a constant area characteristic and have the diaphragm linear with travel, it would again be"ne'cessary to introduce'a deep corrugation of approximate semicircular configuratiomin the metallic sheet. However, when a metal diaphragm is so constructed, a new problem is introduced since "it haslibeen found that the diaphragm thereby becomes exceedingly stifi and unsuitable forthis reason. 'The'stiffn'ess 'apparently'arises largely from the fact that 'hoop'stresses 'are 'set-up in the corrugation =when deflection occurs. Nevertheless because of the desirable repeatability characteristic, -a "metallic type diaphragm would usually be employed if the 'objectional' stifiness characteristic 'could somehow be eliminated-without the sacrifice of a good constant area characteristic.

it is therefore an object of this invention -to'provide "a diaphragm having both desirable -constant=area and repeatability characteristics.

It is a furtherbbject of this invention toprovide a diaphragm of-metallic material having these 'chara'c'teristicsbutwithout the objectional-s'tiffness characteristic in th'e dire'ction in which it deflects.

It is also an object of the invention toprovide-a "diaph'ragin having a desirable constant areacharacteristic introduced by virtue of a corrugation formed therein.

For-a better understanding of my invention attention 'is mow-directed to the following description taken in-coim'ection "with the-accompanying drawings :and to' the 2 pended claims, in which "the features-of my invention be- -lieved tobe n'ovel are' -morepar ticularly set forth. -ln thefl'ravtiin'gs, Fi 1 isa planor -top view parfly breken a-wayof a diaphragm incorpor'ating t-hefeatt'ires of nly invention; Fig. 2' is a sectional -'viewta.ken' on" heline may be incorporated.

2,747,615 Patented May 29, 1956 2-2of Fig. 1; Fig. 3 is an enlarged sectional view taken on the line 3-3 of Fig. 1; Fig. 4 is a plan view similar to Fig. l'illustratinga modification of-"the invention; Fig. 5 is apartialcross sectional vie'w' throu'gh a-fluid pressure responsive device between'portions-of which is employed a diaphragm representing a fur'ther modification of my invention; Fig. 6 is an enlarged cross sectional view through a portionof 'the device shown in'Figure 5 better to'illustrate the details of the-modified diaphragm of the invention employed therein and Fig. 7 is-a top plan viewof a fragment 'of the Figs. 5 and 6 diaphragm as seen With-a top portion of -the- Figs. 5 and-6 device removed.

Referring to Figures 1, 2 and 3 of the drawings, I

' have illustrated a diaphragm comprising a relatively thin circular shaped disk 10 of a' siiitablemetallic material such as carbon steel, copper, stainless steel or'a'ny'other metallic material which will withstand thecorrosive' action of fluids to' which it may be subjected. Openings or holes 11 spaced circumferentially around and adjacent the outer edge of the disk'are provided therein for'passage of bolts or cap screws'employed to sealingly clamp the peripheralportions of'the'disk-b'etween abutting'members of the device or instrument-within which the disk In addition, a substantially U-sh'aped annular fold or corrugation 12is also formedfin the disk adjacent the periphery thereof'but Within the peripheral portion which will be clamped within an instrument.

In accordance with the invention and to considerably reduce the hoop stresses in or stiffness of the disk which would otherwise be a characteristic thereof, I provide a plurality of spaced slots 13 extending transversely through and across the fold or corrugation 12. These slots may be of varying widths and spacing therebetween but usually are of the order of hundredths of an'inch. In'any event, the width of each slot is usually relatively small or narrow. For example, I have employed slots with-a width as small as 0.0 1Q'inch*with a spacing between slots of approximately 0.03Qinch.

Although slotting of the corrugation solves the problem of increased stifiness which is introduced into the disk by incorporation of the annular corrugation therein, another and new problem is created "thereby inasmuch as the diaphragm must 'be impervious or constitute a perfect seal through which fluids under pressure cannot pass.

Therefore, in'accordance with a further feature of the invention andto prevent'passage'of'fluid through the slots, 'the slo'ts are 'sealingly covered with a layer or layers of a flexible ;andimpervious or fluid impermeable material which will'resistattack of any fluid which might be used and will changein stifl'ness as little as possible with change temperature. For exa'mp'leQin the embodiment shown in Figures 1, 2 and 3, I have illustrated the employment 'of a 'thin layer 'or coating 14 of'a plastic material such as "Teflon, a polyvinyl resin or dental darn bonded 'to' the convex surface of the corrugation 12. The method'o'f bonding varies dependent :upon the plastic material "em- -'p'1oyed 'asthe coating. *Fbrexaniple, in the case 'of'a polyvinyl resin, a suitablyshapedmoldis coatedwith a commercial mold release"and a polyvinyl resin such as 'Stanley 7 x 2-l6' black- Pastisol is applied to each halfo'f the mold by brushing. The slotted and formed metallic disk freed from oxide, degreased and primed isithen placed in the coated mold, the mold closed and its contents heatedto approximately 350 F. for about'a five -to tenminuto interval'whereby the resin is'c'uredto form a toughfilm' securely bonded to the disk. In'the'caseof 'Teflon,- the metallic =disk 'is cle'aned, degreased, 'de-oxized and-primed. l h'en a silieone' rubber adhesive is' 'l'p'pl'i'ed to =-a' suttace ofthe nretallie' blankand a thin film of-Teflon 3s applied over the silicone rubber adhesive. The metal blank with the Teflon and silicone adhesive is assembled into a mold and cured at a suitable temperature and pressure to effect a secure bond. Inasmuch as theslots 13 are so narrow, such a coating would not be forced through the slots by the fluid pressures usually used. However, in the event that it is desired to increase the width of the slots or to employ a seal of lesser bond strength, the coating may be applied both to the convex and to the concave surface of the corrugation as well.

Although the slots 13 have been illustrated as extending transversely through the annular metallic corrugation in a radial direction, there may be an application or applications where a diaphragm must be used which has greater flexibility than would result by virtue of radial slots.

Thus, I have illustrated in Figure 4, as a modification of 7 my invention, a diaphragm comprising a metallic disk 15 having an annular corrugation 16 therein with spaced slots 17 extending transversely therethrough in a diagonal direction or obliquely at anangle with respect to the radius or radii of the corrugation. With the slots inclined to the radius at angles between 60 and 90 degrees, for example, the diaphragm stiffness is reduced several fold since the longer metal strips or spokes in the corrugation both bend and twist as the diaphragm deflects.

, In'so far as production procedure is concerned, the corrugation may be slotted by several methods. For example, after forming the diaphragm with the corrugation therein, a slitting punch may be employed together with a die having adequate backing and a stripper. On the other hand, a resist may be printed on the entire diaphragm with the exception of the portions of the corrugation to be slotted. Then, such portions,which-would be unprotected by the resist, would be etched through. Subsequently,

one or both surfaces of the corrugation may be sprayed witha coating material such as Teflon using suitable means to block 01f the peripheral portion of the diaphragm outside the corrugation which is usually clamped withinan instrument ordevice and the inner area or portion within the corrugation which is usually interposed and clamped between a pair of relatively rigid push plates.

In Figure 5, I have illustrated a partial cross section through a differential pressure responsive device 18 having an internal space or compartment defined by a pair of abutting housing sections 19 and 20. The compartment is divided into a pair of chambers by a diaphragm representing another modificationof my invention. 7

Like. the previously described embodiment, the dia' phragm of this'modification comprises a metallic disk 21 of metallic material with an annular fold or corrugation 22 therein. As illustrated, the peripheral portion of the diaphragm outside the corrugation 22 is fixedly and seal- .ingly clamped between'the abutting housing sections 19 and while the central portion of the diaphragm inside the corrugation is interposed and clamped between a pair of relatively rigid push plates 23 and 24 in accordance with common and well known practice; Flexure or movement of the diaphragm is transmitted from the push plates to a push rod 25 which in turn transmits the motion to a the slots, I have employed; an annular shaped strip of flexible and impermeable material having outer and inner peripheral portions 26 and 27, Fig. 6, clamped or maintained in sealing engagement with portions of metallic disk Zlrespectively clamped between the housing sections f and the push platesf The impermeable and flexible strip is not otherwise bonded or sealed to the disk 21 so that the intermediate "portion 28 thereof between the clamped peripheral portions is flexibly movable with respect to and engageable with a surface of the corrugation 22 as.

better illustrated in Figure 6. In normal operation, the fluid pressure entering the device or instrument 18 through passage 29, for example, is greater than the pressure entering through the passage 30. If by chance the higher 7 plates, said corrugation having a plurality of spaced slots extending transversely therethrough and an annular strip of semi-flexible impermeable material having outer and pressure greatly exceeds the lower pressure, the diaphragm corrugation is prevented from rupturing by resting against the surface of an annular groove 31 provided in housing section 19. In the event that a large overrange of pressure should occur in a reverse direction, intermediate portion 28 of the flexible strip of impermeable material will move away from the metallic corrugation 22 and assume the shape shown by the dotted lines 32 in Figure .6 Where, it will be observed, the flexible material will not rupture since it will be supported by the surface defined by an annular groove 33 provided in housing section 20.

The flexible strip of impermeable material may be made of any suitable material dependent uponithe expected fluid pres'sure, temperature and corrosive characteristics such as a plastic, rubber, or a plastic or rubber impregnated fabric material. V

Thus I have provided for assembly in fluid pressure responsive devices, diaphragms having the desirable characteristics of low stiffness, minimum' efiective area change with travel, large travel and ability to withstand Furthermore,

large overrange and reversal of pressures. the very objectional characteristic of a sustained deviation inherent in most 'diaphragms is not possessed by the diaphragms of my invention. In other words, my diaphragms possess much less drifting tendency with time, temperature and pressure inasmuch as the load is carried by metal rather than fabric or plastic. In short, the diaf phragms of my invention possess all or" the desirable characteristics only one or a few of which are possessed by any one prior art diaphragm known to applicant.

While I. have, in accordance with the patent statutes, shown and described a particular embodiment of my invention and modifications thereof, it will be obvious that changes and modifications can be made without departing from the invention in its broader aspects and I, therefore,

aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention. a

7 What I claim as new and desire to secure by Letters Patent of the United States is: I r

'1. 'In a fluid pressure responsive device having aninternal compartment defined by a pair of abutting housing sections, a diaphragm dividing said compartment into a pair of chambers and comprising a disk of metallic material having an annular corrugation therein, a peripheral portion of said diaphragm outside said corrugation being fixedly clamped between said housing sections with a central portion thereof inside said corrugation beng lIltBl'r posed and clamped between a pair of relatively rigid push inner peripheral portions maintained in sealing engagement with portions of said metallic diaphragm respectively clamped between said housing sections and said push plates, the intermediate portion of said annular strip be tween said peripheral portions thereof being flexibly. movable with respect'to and engageable with a surface of said corrugation.

, 2. In a pressure responsive device having an internal compartment defined by a pair of abutting housing sec- 7 tions, the combination of a diaphragm dividing said com-: partment into a pair of chambers and comprising a'disk f p of metallic material having an annular corrugation there-,

'in, a peripheral portion of said diaphragm outsidefsaid.

corrugation being fixedly clamped between said housing sections ,with a central portion thereof inside said corrugation being interposed and clamped between a pairjof relatively rigid pushplates, an annular groove in one of said housing sections, an annular groove in the other of said housing sections positioned opposite said first mentioned annular groove and defining an annular cavity therewith, the corrugated portion of said disk being disposed Within said cavity with the convex surface thereof positioned adjacent the surface defining the groove in said one housing section, said corrugation having a plurality of spaced slots extending transversely therethrough and an annular strip of semi-flexible impermeable material having outer and inner peripheral portions maintained in sealing engagement with portions of said metallic diaphragm respectively clamped between said housing sections and said push plates, the intermediate portion of said annular strip between said peripheral portions thereof being positioned adjacent said corrugation and defining a seal to prevent passage of fluid through said slots and between said chambers, said intermediate portion being flexibly movable with respect to and engageable with the concave surface of said corrugation and with the surface defining the groove in said other housing section.

3. A diaphragm for a pressure responsive device comprising a disk of metallic material having an annular corrugation therein, said corrugation having a plurality of spaced slots extending transversely therethrough, an annular strip of semi-flexible impermeable material maintained in sealing engagement with peripheral portions of said disk outside said corrugation and with an annular portion of said disk inside said corrugation, an intermediate portion of said annular strip between said portions thereof maintained in sealing engagement with said peripheral and annular portions of said disk being flexibly movable with respect to and engageable with a surface of said corrugation and support means spaced from and positioned opposite said surface for support of said intermediate portion of said flexible strip when disengaged from said corrugation.

References Cited in the file of this patent UNITED STATES PATENTS 768,984 George Aug. 30, 1904 1,038,636 Oxnard Sept. 17, 1912 1,802,136 Carter Apr. 21, 1931 2,061,905 Hewitt Nov. 24, 1936 2,220,902 Hastings Nov. 12, 1940 2,359,721 Williams Oct. 3, 1944 2,578,730 Nicholson Dec. 18, 1951 2,592,501 Williams Apr. 8, 1952 2,646,077 Whitney July 21, 1953 FOREIGN PATENTS 350,005 France June 20, 1905 OTHER REFERENCES Modern Plastics, pp. 108, 109, November 1947, 137- 793.

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