US2220902A - Gauge diaphragm mounting - Google Patents

Description

NOW 1940. H. HASTINGS ETAL 0,9

' GAUGE DIAPHRAGM MOUNTING Fild April 8, 1957 eraerwy BY 6:307:96 F

.uasnoonamuoonem. om @KSWWUK N 8: fiezr'A ORNEYS Patented Nov. 12, 1940 GAUGE 'nmrnaAGM MOUNTING Herbert Hastings, Brighton, and George E. Ford,

Rochester, N. Y., assignors to Rochester Manufactoring 00., Inc., Rochester, N. Y., a corporation of New York Application April 8, 1937, Serial No. 135,758

t 2 Claims.

This invention deals with a gauge, and more particularly a pressure gauge, although some features of the invention are applicable also to gauges of other types.

An object 01 the invention is the provision of a generally improved and more satisfactory gauge, so designed and constructed that it may be made economically and quickly, of few parts, and will be sturdy and reliable in operation.

Another object is the provision of an improved diaphragm construction, and of improved means for holding the diaphragm in place.

Still another object is the provision of a diaphragm construction particularly useful in instruments for registering temperature in accordance with the vapor tension of a fluid whose vapor tension is not a straight-line function of the temperature to be measured.

A further object is the provision of a novel and an improved method of constructing the diaphragm holding means. I

To these and other ends the invention resides in certain improvements and combinations of parts, all as will be hereinafter more fully described, the novel feaatures being pointed out in the claims at the end of the specification.

In the drawing: Fig. 1 is a section taken centrally through a auge constructed in accordance with one emao bodiment of the invention; i

Fig. 2 is a section through the rear end of the gauge shown in Fig. 1, on a larger scale, illustrating additional details;

Fig. 3 is a diagrammatic view illustrating the method of making the construction. shown in Fig. t is a view similar to a fragment of Fig.2, showing a modification of the diaphragm means;

Fig. 5 is a view similar to Fig. 4 showing another modification thereof;

Fig. 6 is a view of diaphragm means constructed in accordance with still another embodiment of the invention, particularly for use in vapor tension thermometers, and

Fig. '7 is a graph illustrating the vapor tension curve of a typical fluid for which the construction shcwnin Fig. 6 is designed.

The same reference numerals throughout the several views indicate the same parts.

This application is a continuation in part of our copending application for patent on Gauge construction, Serial No. 84,662, filed June 11, i936, issued July 12, 1938 as Patent No. 2,123,532. Certain subject matterdisclosed but not claimed in the present application is claimed in said appllcation No. 84,662, or in our companionapplication for patent on Gauge dampingconstruction, Serial No. 134,588, filed April 2, 1937, issued February 14, 1939'as Patent No. 2,147,031.

In oneiorm of gauge herein disclosed as a preferred example of the present invention, the gauge includes a casing having a main cylindrical portion 30, which contains the principal operating parts of the gauge. At the rear end of this portion 30 is an annular inwardly extending wall 3| connected to the forward edge of another cylindrical wall portion 32, of smaller diameter and shallower than the portion 30. The cylindrical wall portion 32 forms a pocket which receives the pressure responsivediaphragm means. At therear edge of the portion 32. is an inwardly extending flange or wall 33 which .merges into a stem portion 34 which may be threaded internally or externally, as desired, for connection to a conduit, tank, or other suitable article subject to the pressure to be indicated.

Within the main chamber formed by the cylindrical wall portion 30 is a mounting plate 40 held in place by suitable means such as studs il passing through the plate and integral with the rear wall 3| of the chamber. Struck up portions on the mounting plate 40 form journals or bearings for a shaft 43 which extends approximately diametricallywith respect to the casing 30'and which is provided near itsmiddle with a crank portion 44 which overlies a stud mounted on the pressure responsive diaphragm, as described in greater detail below.

As the diaphragm moves in response to pressure variations, the stud t5 moves in a direction axially of the gauge and, by acting upon the crank portion M, turns the-shaft 43. A larger crank 41 atthe lower end of the shaft 43 is thus moved in accordance with the movements of the diaphragm. The crank ll lies against one side of and transmits its movements to an arm til formed as an extension of one armof a generally U-shaped member 39 loosely pivoted on a bearing pin 50 secured to the'mounting plate it. The other arm of the U-shaped member i9 is extended at 5| in a general directiontoward the center of the casing 30, and the extension is pro vided with an arcuate portion having gear teeth I thereon concentric with the pivotal axis 50. Thus as the stud 45 of the diaphragm is moved, the motion thereof will be transmitted to the gear segment, but the gear segment will have a greatly enlarged extent of motion relatively to that of the stud 45, not only because of the enlarging effect due to the size of the crank arm 41 with relation to the size of the crank ,but also because of the further enlarging effect due to the distance of the gear teeth on the arm H from the pivot 50, with respect to the distance of the arm 48 from the pivot 50.

At suitable spaced points around the circumference of the cylindrical casing portion 30 cuts are made in the wall 30 and-portions of the wall are forced inwardly as indicated at 60, to form ledges or seats on which the dial plate may rest. The dial plate is provided with a hole of the proper size and in the proper location to receive the end of the pin 50, so that when the dial plate is impaled upon the pin 50, as shown in Fig. 1, the dial plate is properly oriented with respect to the operating mechanism of the gauge. In the center of the dial plate is a bushing 60 in the form of a hollow rivet which extends through the plate and serves to connect the plate firmly to a U-shaped bracket 6? supported by the plate. The'needle shaft 60 extends through the bushing or hollow rivet and is journaled therein near its forward end, the rear end being journaled in the bracket 61. The front end of the shaft 68 carries the needle or pointer 60 which sweeps over suitable scale graduations on the front face of the dial plate GI. A pinion l0 fixed to the shaft 68 behind the bushing 68 meshes with the gear teeth on the member 5|, while behind the pinion I0 is a coiled hair spring H having one end secured to a hub or collar on the shaft 68, and having its other end secured at 12 to the bracket 61. I This hair spring constantly tends, with a slight force, to rotate the needle in one direction, thus taking up backlash between the pinion I0 and the gear teeth on the member 5|, and holding the crank 44 always against the stud 15.

In front of the dial plate SI and the needle 69 is a transparent plate 00 of glass or other suitable material the periphery of which mayrest upon the front edge of the casing portion 30. The glass may be held in place by a bezel having a cylindrical portion 0! fitting, over and surrounding the casing portion 40 and forming a tight press fit therewith, if desired, the bezel also having an annular inwardly extending portion 04, which overlies a washer or gasket 82 and retains this gasket in place against the front faceof the peripheral portion of the transparent plate 00.

A second gasket 90 may be placed beneath the glass 80, and a sleeve or spacing ring BI maybe placed between the gasket 90 and the dial plate 6| to hold the dial plate firmly seated against the abutment 60. I

The parts above described constitute an illustrative embodiment of a gauge body and means for operating the needle from the movements of the diaphragm, but such parts may be varied at will and do not, of themselves, constitute part of the present invention. The invention herein claimed relates to the construction and manner of mounting the diaphragm means, and one embodiment thereof will now be described with reference particularly to Fig. 2 of the drawing.

The diaphragm means in this first embodiment of the present invention comprises a pressure responsive diaphragm I00 of relatively thin metal, preferably corrugated concentrically to render it more flexible, and a relatively stiff and unyielding guard plate IOI of substantially thicker metal, preferably correspondingly corrugated so that if the diaphragm I00 be sufllciently displaced axially, as by subjecting it to heavy pressure, "substantially the entire face of the diaphragm may come into contact with the guard plate NI and be supported thereby against rupture. The operating stud 45 previously mentioned is secured to and projects forwardly from the front face of the diaphragm I00 at its center, and the guard plate IN is provided with a central opening I02 through which the stud 05 extends.

A gasket I04 is placed between the diaphragm I00 and the guard plate IOI adjacent their peripheries. This gasket is preferably of a substantially incompressible material. One of the principal purposes of the gasket is to provide a sharp line of separation between the diaphragm and the guard plate, so that as the diaphragm of this embodiment of the invention moves back and forth under the influence of pressure variations, the eflective diameter of that part of the diaphragm which is subject to movement will remain constant so long as the diaphragm is not subjected to such excessive pressures as will cause it to lie fiat against the guard plate. In other words, in this embodiment of the invention, the diaphragm during its normal fluctuations or movements does not come into contact with any part of the guard plate, and has at all times a constant effective diameter subjected to the pressure to the right of the diaphragm. Only when excessive pressure is applied to the diaphragm does it contact with and become supported by the guard plate IOI.

The peripheral edge of the diaphragm I00 may be, and preferably is, bent into cylindrical shape, to extend forwardly past the periphery of the guard plate IOI, as indicated at I05, and is then bent radially inwardly as at I06, thus securely locking together the members I00 and I0! of the diaphragm assembly or diaphragm means. This diaphragm assembly is placed within the small cylindrical chamber formed by the cylindrical wall portion 32 ,of the casing and is seated against a gasket I09 whichiies against the flange 3'3 and prevents the diaphragm assembly from moving in one direction, that is, in a direction axially backwards or towardthe right when viewed as in Figs. 1 and 2. According to the present invention, novel and improved means is provided for holding the diaphragm assembly against movement in the opposite direction, that is, in a direction [axially forwardly or toward the left when viewed as in Figs. 1 and 2. This improved holding means is formed by the method indicated diagrammatically in Fig. 3, to which reference is now made.

After the diaphragm. assembly has been placed within the cylindrical wall portion 32, a tool 0 is alined concentrically with this cylindrical portion 32. The tool H0 has, around its entire periphery, a sharp annular cutting edge III of a diameter slightly greater than the external diameter of the diaphragm assembly, or the internal diameter of the cylindrical wall portion 32. This tool I I0 may constitute part of a press. The tool is then forced downwardly from the position shown in Fig. 3, so that the sharp cutting edge III cuts into the metal of the wall 32 all the way around the periphery of the diaphragm assembly, and cuts, in effect, an annular slice from such metal, extending all the way around the periphery of the diaphragm assembly. The inclination of the lower surface II! of the tool causes this annular slice of metal to be bent inwardly and downwardly upon or onto the periphery of the diaphragm assembly, as indicated at H3 in Fig. 2. The portion H3 remains attached to and forms an integral part of the metal 01' the wall portion 82, and conv p "it" is mama m m htsior stitutes' an a excellent abutmentor pressure re; sisting means for holdingthe diaphragmassem-t bly properly seated in the casing and preventing forward movement thereof under the influence ofpressure on therear side of the diaphragm. The

operation of cutting down the side walls, 32. and

bending them inwardly over the {edge of the diaphragm may be conveniently referred to as an.

staking operation. Frequently the integral flange portion m provides a sufiicient-fluid tight seal around the periphery ofthe diaphragm as'sem bly, but usually it is preferred to employ additional sealing. means. This is conveniently in the form of a body H5 of solder, applied in a continuous annular body around'the entire periphery of the diaphragm assembly,-in a molten state, and usually to a suflicient extent-to cover completely the flange I I3 and extend a s'ubstan- I tial' distance axially outwardly along the'wall 32 and radially inwardly along the guard plate llll; as readily apparent froml ig. 2. It is "foundtha't solder thusapplied in a moltenforsubstantially! molten condition and then allowedtdsolidify" forms an excellent seal at'this'point and prevents all possibility of fluidlealkage pastjthe diaphragm assembly. It is also to nbted that is indicatedln Fig. 4, in whichthe diaphragmis, shown at ltlla and the guard platelet Ulla. i In-' steadoi using a gasket" lM between the phragm and the guard plate in orderjtoflobtain constant working diameter of the: diaphragm."

the arrangementhere' employed isv to ex n dthe guard plate rearwardly. at its periphery to form t a cylindrical flange. M5, the inner surface of which is substantially truly cylindrical for a material distance. The diaphragm llllla has a similar cylindrical flange I26 flttlngwithin the flange l of the guard plate, and it'may terminate in an annular radial flange I21 spaced from the rear edge of the flange l25 by an interposed gasket lit. The diaphragm llllla is so shaped that it curves away from and leaves the guard plate ltla at a point on the flange I25 where the flange is still truly cylindrical. Thus, notwithstanding flexing of the diaphragm, the effective diameter thereof does not vary, but always remains the same so long as the diaphragm is not subjected to such excessive pressures that it is actually made to lie against the guard plate.

A gasket ltBa may be employed between the diaphragm flange E27 and the casing portion 33, and the whole diaphragm assembly may be fastened in place by a staking operation, which forms a flange llta similar to the flange H3 above mentioned. A sealing body ll5a may be employed, corresponding to the sealing body M5 of the previous embodiment.

In Fig. 5 of the drawing there is shownv another embodiment similar in general to that indicated in Fig. 4.. This embodiment includes a cylindrical flange 52517 on the guard plate Illlb. and the diaphragm Will) has a cylindrical flange lztb fitting within the flange l25b. As before, the separation between the diaphragm and the guard plate occurs at a point where the flange or deformed the diaphragm do to v ees 'mc a 1a eifectivewo'rkingdiametcr thereor At 121b, the diaphragm g u I outwardly past the rear edged the guard plate flange Eli, and then at]!!! the diaphramtis bent forwardly along. the outer edge of theguard plate lb, to a point where it will contact'with the sealing bodyllib. A gasket I281) may interposed between the rear edge of the guard plate flange l25b and the diaphragm flange IZll).-

The advantage :of this construction over that shown in Fig. 4 is that the sealing body .llib here contacts directly with the metal of the diaphragm itself, and seals the: diaphragm to the casing, irrespective of any leakage which might occur between the diaphragm and "the guard plate. In the construction shown in 4, how

ever, the sealing means Ilia doesnot comedirectly into "contact with the "diaphragm llla, and if the construction were somewhat defective, leakage might occur around the edge o!- the diaphragm and into the space "between the diaphragm' and the guard platefafterfwhichfthe fluid could easily escapeinto the gaugeithrou 'gh liixceptffor the difierences abovej rnentionedfthe alternative constructions described in; connection: h i 5 (1 5mg be i ti mi ing ch l struction pro ously described 7 in connection with;

n-45 v In thefconstruetions described with reference o F gs; t n P i n) as, be m de: ri maintaining theefiective working diameter or the diaphragm constantfduring flexurefj of the diaf phragm except when" excessive 'flexure I causes the diaphragm to come into contact with the guard 1 plate. This maintenance] of constant working diameter is highly desirable in various types of measuring instruments, such as straight pressure gauges, where the scale on the dial plate,

graduations on the dial M can bespaced ap-.

proximately evenly or uniformly.

For certain types of measuring instruments, however, the foregoing arrangement is not wholly satisfactory. For example, if the par ticular instrument in which the diaphragm assembly is employed is a vapor tension thermometer, the vapor tension or pressure behind the diaphragm may not be a straight-line function of the temperature of the fluid behind the diaphragm. Hence, a temperature increase of one degree at one point in the temperature range of the instrument would cause a difierent pressure increase acting on the diaphragm than would be apart at one part of the scale than at another,

part of the scale.

As an example, to illustrate this difliculty, there is shown in Fig. '7, somewhat schematically or diagrammatica ly, a part of a vapor pressure curve of a typical fluid frequently used in vapor tension thermometers, namely, dichlormethane or methylene chloride. The graph in Fig. '7 is graduated horizontally, along the bottom of the fig- 5 ure, in degrees Fahrenheit, and is graduated verlow 250 F., the vapor tension or pressure is not lo a straight-line function of the temperature, and

a temperature change from 125 to 150 would cause quite a different pressure change than a 1 temperature change of the same amount, from A diaphragm assembly particularly designed for use in situations of this kind is illustrated diagrammatically in Fig. 6. Here the'diaphragm is shown at 1000 and the backing plate at 1010. The backing plate is so shaped that it curves gradually farther and farther away from the diaphragm in a direction from the periphery toward the center, as will best be understood from a study of Fig. 6. In other words, the backing plate is corrugated to correspond to the corrugations of the diaphragm, as shown, but the general shape of the backing plate, along a radial section, is curved in the same general direction as the curvature of a pseudosphere rather than being straight or conical as in the case of the backing plates of Figs. 2, 4, and 5. A radial line drawn through the tops of the successive corrugations on one side of the backing plate will be a curved line, curving farther and farther away from the diaphragm from the periphery toward the center, in this form of construction shown in Fig. 6, instead of an approximately straight line as in the previous embodiments. The gasket I04 is omitted with this construction, and the diaphragm and the backing plateare preferably in 40 direct contact with each other near their peripherles.

With this construction, as will be readily apparent by careful study of Fig. 6, pressure acting on the back of the diaphragm and displacing it 45 rightwardly when viewed as in Fig. 6 will gradually decrease the effective working diameter of the diaphragm as the extent of displacement increases. In other words, as the diaphragm flexes', a greater and greater extent of its periphery 50 or margin comes into contact with and lies fiat against the backing plate, and the part of the diaphragm thus lying against the backing plate is no longer 'an efiective working part thereof, so that the effective working diameter of the 55 diaphragm decreases until finally, in the extreme position under high pressure, substantially the whole diaphragm lies against the face of the backing plate.

This arrangement of diaphragm assembly per- 60 mits the scale on the dial plate 61 to be graduated approximately evenly or uniformly, notwithstanding the fact that the units of measure used on the scale (such as degrees of temperature) are not a straight-line function of the 5 pressure acting upon and displacing the diaphragm. In otherwords, when the pressure acting upon the diaphragm is relatively low, an increase of a certain amount in that pressure moves or displaces the center of the diaphragm to a 70 certain extent, the diaphragm then being of relatively large effective diameter. When the pressure acting on the diaphragm is higher, however, the diaphragm has a smaller effective working diameter, and then the same increase in the 75 pressure acting upon the diaphragm would cause a lesser displacement of the center of the diaphr sm. thus compensating for the fact that at higher pressures a given increase in pressure should not cause as great a movement of. the temperature indicating needle as the same increase in pressure should cause at a lower part of the scale.

The diaphragm IMc, like all of the previous diaphragms, may carry a centrally located stud 450 for operating upon the crank 44 of the operating shaft 43, and this stud, as in the case of the studs on the preceding diaphragms, may be secured and sealed to the diaphragm by forming a rivet head 200 on the end of the stud which passes through the diaphragm, and by sealing around the edges of the rivet head by means of a sealing body 2M of solder or the like.

To eliminate or reduce unnecessary fluctuations in the diaphragm, the gauge may be provided with pulsation damping means, including, for example, a sleeve I40 sealed within the stem portion 34 of the diaphragm, another sleeve I4I sealed within the sleeve I40, and a plunger or plug I43 movable longitudinally through the sleeve I through a limited range of movement, the plunger I43 being of slightly smaller diameter than the opening through the sleeve I 4| in which it is located, so that thereis a small annular space surrounding the pin I43 through which the pressure variations to the right of the damping device may reach the diaphragm to the left of the damping device. This damping device is not claimed per se in the present application, but

is claimed in one of the copending applications previously mentioned.

While certain embodiments of the invention have been disclosed, it is to be understood that the inventive idea may be carried out in a number of ways. This application is therefore not to be limited to the precise details described, but is intended to cover all variations and modifications thereof falling within the spirit of the invention or the scope of the appended claims.

We' claim:

1. A pressure gauge of the type including a casing wall having a substantially cylindrical section of substantial length and extending approximately radially outwardly at one end of said cylindrical section and approximately radially inwardly at the opposite end of said cylindrical section, and a diaphragm assembly within and extending across said cylindrical section and seated against said inwardly extending part of said wall, said cylindrical section of said wall being of materiallygreater axial length than the axial thickness of saiddiaphragm assembly at its peripheral edge adjacent said wall, characterized by the fact that a portion only of the thickness of said cylindrical wall section between said diaphragm assembly and said outwardly extending part of said wall is partially cut from the remainder of the thickness thereof around substantially the entire periphery of said diaphragm assembly and deformed inwardly and downwardly into overlying relation to the periphery of said diaphragm assembly to hold said assembly seated against said inwardly extending part of said wall.

2. The combination of a casing including walls forming a hollow cylindrical portion of substantial axial length, said walls extending approximately radially inwardly for a distance at one end of said cylindrical portion and approximately radially outwardly for a distance at the opposite and of said cylindrical portion, a sheet metal guard plate having an opening through the guard plate adjacent the center thereof and having a series of annularcorrugations between said opening and the periphery of the plate, a flexible sheet metal diaphragm lying adjacent said guard plate and having a projection alined with said opening in said guard plate and also having a series of annular corrugations substantially mating in complementary fashion with those of said guard plate when said diaphragm is displaced to its maximum extent so as to lie substantially against said guard plate, said diaphragm and said guard plate together lying in said cylindrical portion of said casing and being seated approximately aganist said inwardly extending walls, and a flange formed integrally trom a part only of the,

thickness of said cylindrical wall portion and bent inwardly and downwardly into overlying relation to said diaphragm and guard plate to hold the marginal edges of said'diaphragm and guard plate against displacement in a direction away from said inwardly extending radial walls.

HERBERT HASTINGS. GEORGE E. FORD.'

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