US2492465A - Pressure responsive device - Google Patents

Description

Dec. 27, 1949 DAHL 2,492,465

PRESSURE RESPONSIVE DEVICE Filed May 16, 1947 y INVENTOR EDWARD. 7: DAHL FIG. 2 BY g i ,W

ATTORNEY Patented Dec. 27, 1949 UNITED STATES PAT ENT OFFICE Hammel-Dahl Company,

Rhode Island a corporation of Application May 16, 1947, Serial No. 748,631 Claims. (01. 137-157) This invention relates to valves for the control of fluids and more particularly to pressure retention or sealing mechanism for motor driven reciprocating members which are displaced in accordance with variations in the value of a :poWer medium.

As is known, thediaphragm type of valve comprises essentially a diaphragm and spring means associated with the valve element such that the element is urged in one direction by the spring and in the opposite direction by fluid pressure acting on the diaphragm. Such valves may be of the direct or reverse acting type. In th direct acting valves the valve element is moved downwardly by the pressure of air or other fluid medium in the upper diaphragm case and is returned by the spring. Conversely, in the reverse actin typethe valve is urged downwardly by the spring and fluid pressure is exerted in the lower diaphragm .case to elevate the valve element.

A major desideratum in such structures is a .hlgh sensitivity of response to very small increments of air pressure applied to the diaphragm. Such high sensitivity has not heretofore been satisfactorily achieved. The earlier structures in the art were characterized by .a marked hystersis or failure to translate very small changes in air pressure into a corresponding displacement of the valve element. This lack of sensitivity isi-nherent -in the nature of the prior valve construc-tures. Inasmuch as the ac,- curacy of control ultimately effected by the valve element is a function of the variation in air pressure in a diaphragm chamber, it is apparent that the reciprocation of the rod or stem, which is connected to the valve element, should be secured with the absolute minimum of friction. .Such a low friction reciprocation, of course, is difficult to achieve in even simple mechanisms but is particularly diflicult to attain under circumstances encountered in the diaphragm type of valve of the reverse acting type, i. e., where there is imposed the necessity of establishing a highly effective air seal between the lower diaphragm chamber and the reciprocating stem.

In the past, various expedients have been invoked to establish an "efiective fluid seal and to reduce the friction of the'valve stem to thereby .increase the sensitivity of the valve unit. Generally considered, these efforts have involved the use of special packing g1ands,'oi1 impregnated porous metal bushings and the like, In many prior structures where an eifective air pressure seal was desired recourse was had to metal bellows seals. Where frictionallyengaging contact .seals were employed the direct sliding contact with the reciprocating member inexorably set up substantial frictional resistance to the reciprocation of the stem. Similarly, where metal bellows were utilized not an inconsiderable component of the applied force was expended in extending or compressing the metallic structure of the bellows.

As a result of extensive experimentation on this problem it has now been found that the operation of motor valve structures of the type describedmay be markedly improved by increasing the sensitivity of the valve to minor incremen'ts of air pressure change and by insuring a quick or immediate response to such pressure changes.

The improvements'achieved by the present invention stem from th concept of substantially eliminating contact or frictional seals and establishing a gas seal between the diaphragm casing and a reciprocating valve member by means of a non-metallic bellows seal. As will be seen more fully hereinafter, the novel sealing means comprises a flexible-non-metallic member such as a suitable fabric coated or impregnated with an elastome-r such as natural or synthetic rubbers or the like. Such material, as will readily be appreciated, is flexible or flaccid and can be extended with but the minimum amount of re- ,sistance particularly when in corrugated form. The resistance set up by the flexible fabric will vary with the type of the fabric and particularly with its thickness. In order to insure high sensitivity a highly flexible, gas impermeable fabric is utilized as a bellows and the fabric itself is re-enforced and maintained in its desired configuration by means of a steel spring.

In order to enable .a more ready comprehension of the invention there is shown in th accompanying drawing an illustrative preferred modification of the novel seal as embodied in a valve reversible superstructure, in which:

Fig. 1 is a central vertical section of a diaphragm valve superstructure, and

Fig, 2 is an enlarged sectional detail of the novel sealing means.

In order to'simplify the description of the invention the improved type of seal is illustrated as embodied in the superstructure for a valve body, it being understood that any suitable type of valve body in which fluid flow is to be controlled may be attached to such standard superstructure. While the novel low inertia and low friction sealing connection may be utilized generally in diaphragm valves, it is shown herein to the motor and is constantly urged in the opposite direction by the spring means.

As shown in the drawings, the superstructure comprises a motor, designated generally by the numeral l, which is provided with the reciprocating stem 2 centrally positioned and operable in the spring barrel or case 3. The spring case contains the spring 4, which is so constructed and arranged as to apply a force to the stern opposing the action of the diaphragm. As will appear subsequently, by simple and conveniently effected change in the position of certain parts associated with the spring its direction of thrust can be reversed so that, as intimated previously, the superstructure can function equally efiectively with a direct or reverse acting valve unit.

The spring barrel is extended downwardly to form the integral vertically slotted yoke 5. This latter is formed with the terminal flange 6 which may be provided with apertures for reception of studs or bolts so that the entire superstructure can readily be attached directly to a valve body or to an intermediate bonnet of a valve body.

Considered more in detail, the motor structure includes the upper diaphragm casing and a similarly or symmetrically conformed lower diaphragm casing 8 which casings are formed with the lateral flanges 1' and 8 respectively. A diaphragm 9 is secured between the flanges by suitable means such as the bolts Ill. The diaphragm may be composed of any suitable, flexible, gas-impermeable material such as the rubberized fabric commonly employed in the art. The attached upper and lower casings with the intermediate diaphragm thus define, in effect, two pressure chambers, namely, an upper chamber ii and a lower chamber I2 to which fluid, such as air, may be admitted to apply a variable pressure on either the upper or lower face of the diaphragm,

The upper diaphragm casing is formed with the port or aperture l3 registering axially with the bore of a pipe fitting 14, Similarly, the lower diaphragm casing is provided with the port I5 is communication with the lower pipe fitting 16. The pipe fittings may be attached to their respective casing members in any suitable manner, preferably by weld joints.

The diaphragm 9 is connected to the diaphragm stem 2 in any suitable manner so as to impart reciprocating motion to the latter upon applied fiexure of the diaphragm. As shown, the diaphragm is associated with the upper pressure plate IT and the lower pressure plate 58. These are centrally apertured to receive the reduced end section 59 of the diaphragm stem. As will be observed, the motor stem 2 is reduced at l9 to establish the shoulder 26 and is also reduced a short distance below shoulder 20 to provide the second shoulder 2|. The shoulder 20 is adapted to directly abut the lower pressure plate l8. The pressure plates are'held in firm attach- 4 merit to the shaft and diaphragm by means of the nuts 22.

The spring barrel 3 is somewhat reduced in internal diameter at its upper section to provide a slightly enlarged bore and to establish a shoulder or abutment 23. This reduced bore section is also cut away to provide the groove 26 for the reception of the split spring locking ring 25. A spring button or bridge 26 is fitted into the upper section of the spring barrel so that its lower peripheral edge engages the abutment 23. The bridge is centrally apertured and is fitted with the guide bushing 26'. The bridge is formed with the depending boss 2'! which functions to retain spring 2 in proper position. The upper face of the member 25 is cut away to provide the peripheral groove 28 in which is mounted a compressible sealing member such as the ring 29 composed of neoprene or other elastomeric material. As will be observed, the bridge 26 functions as a guide for the stem 2 and as a thrust abutment or button for the spring 4. The boss 2! serves to center the spring in proper axial position.

The spring button 26 is maintained in assembled position in the barrel by means of the centrally apertured retainer disc 39, As will be seen, this disc fits snugly within the enlarged bore section of the spring barrel and is locked in its operative position by means of the looking ring 24. In assembling the superstructure the disc 36 is forced downwardly to compress the ring 29 thus establishing an effective air seal between the barrel on the one hand, and bridge 26 and disc 30 on the other.

As indicated previously, the invention basically comprehends the concept of establishing a seal of maximum gas-impermeability coupled with minimum physical inertia between the diaphragm chamber and the reciprocating stem to thereby positively insure a high sensitivity of response of the valve element to very small changes in air pressure on the diaphragm. This is achieved by utilizing a special bellows seal and appropriately associating it with the diaphragm on the one hand, and the spring barrel on the other, so that the sealing or pressure retention function does not involve any frictional pressure contact on the reciprocating stem.

The improved bellows or Sylphon seal is shown in detail in Fig. 2. This comprises the tubular corrugated member 3| which is composed Of suitable gas-impermeable material such as rubber, or other equivalent ela-stomers, or a light, strong fabric coated, saturated or impregnated with an elastomeric material such as neoprene. Such material is impermeable to gases and is essentially flexible or flaccid and therefore may be extenuated or convoluted with the minimum application of force. Since this material is highly flexible it is inherently non-sustaining and therefore it is desirable to provide a supporting structure which will retain the material in the desired tubular corrugated shape. This is accomplished by associating a helical spring 32 with the tubular fabric. As will be appreciated, the essential function of the spring is to maintain the gasimpermeable extensible tube 3| in the desired tubular shape; hence, the spring need only be of relatively small cross-section and of low tension. It is apparent however that, if desired, the tension of the spring may be beneficially invoked to increase the sensitivity of the unit by utilizing it to compensate for and, to a degree, balance the weight of the diaphragm and pressure plates amassthus renderin the val more accurately and immediately responsive to changesiin ressurecf the controllmg fluid admitted to .a diaphragm chamber.

shown, particularly in 1, the fabric 3| extends beyond the upper andlower convolution oi thesustaining spring-32 The upperextension of the fabric to be :attached to-a part associated with -themovable diaphragm and the lower extension, converselmis adapted to be sethe disc 38. 'Ihe'upper anchoragefor the-bellowsasealcomprises the centrally apertured disc or button 33. as will be noted, :embraces the upper reduced section of stem 2 betweenshoulders- 2i audit. The inner face :of the disc 33 isiornr'ed withaagroove in which the neoprene sealing ring 34 fitted to thereby esrtablish a fluid tightseal between thestem 2 and the disc. The lowerxface of the disc is out out.

along'itsperipherydo form the pe'ripheral groove 35- which receives theupper or terminal. convolution of spring :32 "and" which "also serves to center each :spring in proper axial alignment in the assembled-unit.

The-fabric 31 'is extended upwardly-beyond the upper 'convolution of the-spring and more-or less tightly contacts thecventical face of the disc 30. A pressure tight 'fit between the bellows and disc may be attained :bycementing the fabric extension 35 directly tothe vertical face of the disc 33.,

or, alternatively, by utilizing. a .clamping ring (not shown) to firmly anchor the fabric extension to disc .33

The lower portion of the flexible corrugated low inertia tubing similarly attached to disc 3&- to thereby establish an effective gas pressure seal between the -:diaphragm chamber and the spring barrel. Asshown, the tubular fabric 34 is extended below the -last or'the lower convolution of thezspring 32 and is adapted to snugly engage the shoulder 36 formed on the disc 30. ,The fabricmay be attached to the disc by directly cementing thereto or by means of a clamping ring or acombi-nation of these two expedients. .As will be-observed, the disc is formed withthe peripheralgroove 31 adapted to receive the terminal convolution of the sustaining-spring 32.

effective -functioning of the seal structure will have been appreciated from .the foregoing description. It is apparent that by reason of the interposition of the novel sealing means between the reciprocatingdiaphragin and the spring barrel, permitting free lowlnertia extenuationof the seallngmeans; the-diaphragmitself isthus made .responsive to .minorincrements of pressure applied by introduction ofv controlling fluid to the diaphragm chamber. Since low frictional tolerances are established between the diaphragm s'tem'i and the disc 30 and bridge 26 each increment of applied fluidpressure, however slight, is immediately translated into axial displacement of the shaft 2. p

The lower end of the diaphragm stems! is guided in its reciprocatm'g motion by' the'lowcr its 6 than bushing 42. l refierabdy. bushing is swedged or otherwise "secured to the stem 2.. In the preferred construction the member 42 come prises a porous oil impregnated bushing adapted to reciprocate within the bore of the lowerbridge fill-with the minimum possible friction.

:As has been indicated previously, the diaphragm stem 2 is adapted to be connected .to a valve-stem which latter is directly "connected to areciprocating valve. As shown in Fig. 1., such valve stem 43 is formed with a reducedtapered end section fitting within a bore 44 tapped'in the main diaphragm stem -2-. The main diaphragm stem lmay be connected to the valve stem '43 in any suitable manner, for example, as shown in the drawings, by'means of a taper pin 45 driven through the-"connecting nut to thereby estab? lish a direct reciprocating connection between the diaphragm and the valve stem. As will be appreciated, in lieu of such simple connection any other means of attaching'thevalve stem to the diaphragm :stem 2 maybe utilized.

illustrated, the "diaphragm stem is of reduced diameter in its median and lower section and such reduced section is fitted with thesleeve 41. This may be keyed, .swedged or otherwise attached to the main stem 2 and is exteriorly threaded to receive the spring adjusting element such as the serrated hut 4'6. .Interposed between the adjusting. nut 46 and the spring 2 is a spring thrust button 48. As shown, this is formed with a lower-substantially conical surface contacting the upper oonoidal surface of adjusting nut or button 4:6. The spring thrust "button d8 is formed with :thewcentral boss 49 to receive and center the spring '4.

The yoke section *5 is formed with a suitable aperture 50 to permit readyaaccess to the nut =46 for connecting anddisconnecting the valvestem 43. The spring barrellsimilarly is formed with :slots or other :form of apertures 51 and 52-to permil; the insertion of :tools such as a spanner or screw driver to adjust the position of the nut 46 to thereby vary the tension of spring 4 to any desired degree. These apertures also allow the insertion of a tool to forcibly elevate or depress the stem 2 to free a valve plug which may become locked to its seal by the accumulation of solid deposits or the like.

.A salient feature of the invention, as previously .pointed out, is that it establishes an effective highly sensitive motor valve construction which is standardized for use optionally with direct or reverse acting valve units. The turret top construction is as efficient as it is'esthetic in its balanced symmetry. Such a standard superstructure manifestly insures more economical factory production and most importantly makes it possible to convert from "a reverse actingto a direct acting valve in the field.

The unit shown in the drawings, as will be apparent, is adapted-to be connected to a reverse acting valve through connection with the valve .stem 43. For such a purpose the variable fluid pressure medium isconnected to the unit through the lower'pipe fitting l6. In these circumstances the pressure of ithec'ontrol fluid acts on the lower surface of the diaphragm tending to elevate the diaphragm stem and its connected valve stem 43. The spring 4 conversely urges the stem 2 downwardly in opposition to the applied fluid pressure.

Such :a unit may readily'be converted so as to function equally effectively with a direct acting valve unit. This may be readily achieved by dismantling the unit and rearranging the position of spring 4, the spring thrust button 48 and im associated nut 46. In such newly assembled position for functioning as a direct acting valve the lower convolution of spring 4 then abuts the upper face of bridge 40 and the thrust button 46 and adjusting nut 46 occupy a position near the upper end of sleeve 4'! and about opposite the slot 52. The source of the controlling fluid pressure is then connected to the upper diaphragm chamber l I through fitting M. It will be seen thatthe unit is designed so as to facilitate such a conversion. This may readily be done by removing the upper diaphragm case 1 and unlocking the locking or retainer ring 25. Upon disconnecting the valve stem 43 and removing the nut 66 the stem 2 with the attached nut 46 and the upper rings 26 and 36 may be removed from the spring barrel after which the position of the thrust ring 48 and nut 46 is changed as previously described.

It will be evident that the improved diaphragm valve construction may be adapted for use with rotary as well as reciprocating valve elements. This may be done by translating the reciprocating motion of diaphragm'stem 2 to rotary motion by suitable means and utilizing such rotary motion to actuate a rotary valve.

It will be observed that the unit is of simplified design and of sturdy construction. The unit may be fabricated largely from machined bar stock thus insuring high structural strength coupled with optimum dimensional tolerances. It will now be appreciated that the invention presents manifold advantages including simplicity of construction, facile conversion in the field and a unit which is as essentially rugged as it is sensitive. While a preferred modification of the invention has been described it is to be understood that this is given didactlcally to exemplify the underlying principles of the invention-and not as limiting its useful scope except as such limitations are clearly imposed by the appended claims. v

I claim:

1. A diaphragm valve superstructure which comprises, a diaphragm casing having a flexible diaphragm mounted therein, a stem connected with the diaphragm and movable therewith, a spring barrel secured to the diaphragm casing, a stem guide and spring abutment assemblage mounted at each end of the barrel, a spring enclosing the stem having one end contacting one spring abutment assemblage and the other end contacting a part adjustably movable axially on the stem and means to establish a fluid tight seal between the diaphragm casing and the stem including, a flexible, tubular, non-metallic bellows attached respectively to the said assemblage at the upper end of the barrel and to a movable part associated with the diaphragm.

2. A diaphragm valve superstructure which comprises, a diaphragm casing having a flexible diaphragm mounted therein, a stem connected with the diaphragm and movable therewith, a spring barrel secured to the diaphragm casing, a stem guide and spring abutment assemblage detaehably mounted in the upper section of the barrel, a spring enclosing the stem having one end contacting the said assemblage and the other end contacting a part adjustably movable axially on the stem, and means to establish a fluid tight seal between the diaphragm casing and the stem including a flexible, tubular, non-metallic bellows attached respectively to the said assemblage and to a movable part associated with the diaphragm.

3. A diaphragm valve superstructure which comprises, a diaphragm casing having a flexible diaphragm mounted therein, a stem connected with the diaphragm and movable therewith, a spring barrel secured to the diaphragm casing, a stem guide mounted in the upper section of the barrel, a stem guide mounted in lower section of the barrel, a spring'enclosing the stem having one end contacting one of said stem guides and the other end contacting a part adjustably movable axially on a portion of the stem and means to establish a fluid tight seal between the diaphragm casing and the stem including a flexible, tubular, non-metallic bellows attached respec tively to the upper stem guide and to a movable part associated with the diaphragm.

i. A diaphragm valve superstructure which comprises, a diaphragm casing having a flexible diaphragm mounted therein, a stem connected with the diaphragm and movable therewith, a spring barrel secured to the diaphragm casing, an upper stem guide detachably mounted in the upper section of the barrel, a spring enclosing the stem having one end contacting the said upper stem guide and the other end contacting a part adjustably movable axially on the lower portion of the stem and means to establish a fluid tight seal between the diaphragm casing and the stem including a flexible, tubular, non-metallic bellows attached respectively to the upper stem guide and to a movable part associated with the diaphragm.

5. A motor valve superstructure which comprises, a diaphragm casing having a flexible diaphragm mounted therein, and defining an upper and lower pressure chamber, a fluid inlet connected with each chamber, a stem connected with the diaphragm and movable therewith, a spring barrel secured to the diaphragm casing, a stem guide and spring abutment assemblage detachably secured to the upper portion of the barrel and forming a pressure tight seal therewith, a stem guide unit mounted in the lower section of the barrel, a spring adapted to enclose the stem, said stem guide being provided with means at stem, means to establish a fluid tight seal between the diaphragm stem and the diaphragm casing including a flexible, tubular, non-metallic bellows attached respectively to the said assemblage and to a movable part associated with the diaphragm.

EDWARD T. DAHL.

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

UNITED STATES PATENTS Number

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