US3465112A

US3465112A - Fluid pressure actuated diaphragm switch

Info

Publication number: US3465112A
Application number: US673604A
Authority: US
Inventors: Ludwig Reichert; Werner Heinlein
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1966-10-27
Filing date: 1967-10-09
Publication date: 1969-09-02
Anticipated expiration: 1986-09-02
Also published as: DE1590170B2; GB1196005A; SE345338B; AT278955B; DE1590170A1; FR1535064A

Description

Sept. 2, 1969 L. REICHERT E AL FLUID PRESSURE ACTUATED DIAPHRAGM SWITCH Filed Oct. 9. 1967 & xwmx INVENTORS Ludwig REICHERT Werner HEINLEIN United States Patent 3,465,112 FLUID PRESSURE ACTUATED DIAPHRAGM SWITCH Ludwig Reichert, Waiblingen, and Werner Heinlein, Stuttgart, Germany, assignors to Robert Bosch GmbH, Stuttgart, Germany Filed Oct. 9, 1967, Ser. No. 673,604 Claims priority, application ggrmany, Aug. 23, 1967,

9, Int. Cl. Hlllh 35/40 US. Cl. 20083 9 Claims ABSTRACT OF THE DISCLOSURE A fluid pressure actuated switch whose housing is provided with an internal annular recess for the marginal portion of an elastomeric semielastic diaphragm.whose central portion bulges into the pressure chamber, of the housing. The pressure chamber is located opposite a second chamber which receives one or more contacts. When the pressure chamber receives a fluid, thecentral mrtion of the diaphragm tends to flatten out with resultant radial expansion of the diaphragm. This radial expansion is resisted by contact of the diaphragm edge with the bottom wall of the recess so that the material of the marginal portion of the diaphragm yields in axial direction, whereby the thickness of the marginal portion increases so that the latter also bears against the side walls of the recess to provide a fluidproof seal between the two chambers. Prior to admission of fluid into the pressure chamber, the thickness of the marginal portion at most equals the axial length of the recess.

BACKGROUND OF THE INVENTION The present invention relates to improvements in fluid pressure actuated diaphragm switches.

German Patent No. 1,080,189 discloses a diaphragm switch whose housing accommodates a diaphragm having a marginal portion tightly clamped by a steel ring so that it undergoes axial compression. The diaphragm divides the interior of the housing into a pressure chamber and a second chamber which accommodates one or more electric switch contacts. The central portion of the diaphragm bulges into the pressure chamber and is deformed in response to admission of pressurized fluid to actuate the switch. The steel ring cooperates with an internal shoulder of the housing to clamp the marginal portion of the diaphragm.

A serious drawback of such pressure responsive switches is that their parts must be machined and assembled with a high degree of precision which contributes to high initial cost and result in a large number of rejects. The clamping action of the aforementioned ring must be selected with a view to prevent damage to the marginal portion of the diaphragm. The interior of the housing must be machined with a high degree of precision to insure satisfactory bulging of the diaphragm and to avoid unevennesses on the aforementioned shoulder because the unevennesses could result in damage to the marginal portion of the diaphragm.

SUMMARY OF THE INVENTION It is an important object of the present invention to provide a simple, compact, inexpensive and rugged fluid pressure actuated diaphragm switch.

Another object of the invention is to provide a diaphragm switch which can operate properly even if its component parts are not machined or otherwise finished with a high degree of precision.

A further object of the invention is to provide a diaphragm switch wherein the marginal portion of the diaphragm need not be clamped in the housing but the diaphragm is still capable of preventing escape of fluid from the pressure chamber.

An additional object of our invention is to provide a diaphragm switch wherein the diaphragm may be installed in the housing in a novel and time-saving way.

Briefly outlined, our invention is embodied in a fluid pressure actuated electric switch which comprises a housing having an internal surface provided with an annular recess of predetermined axial length or width, a deformable diaphragm inserted into the housing and having a marginal portion received in the recess whereby the interior of the housing is divided into a pressure chamber and a second chamber or switch contact chamber, the marginal portion of the diaphragm having a thickness which is less than or at most equals the width of the recess and the diaphragm further having a central portion which bulges into the pressure chamber, and a nipple or analogous means for admitting into the pressure chamber a gaseous or liquid pressure fluid to stress the diaphragm with resulting thickening of the marginal portion whereby the latter provides a fluid-tight seal between the two chambers. The central portion of the diaphragm flattens out in response to admission of fluid into the pressure chamber so that the diaphragm tends to expand radially with ensuing thickening of the marginal portion. 7

The housing is preferably provided with an apertured partition located in the second chamber to constitute a back support for the central portion during admission of fluid into the pressure chamber. The partition can slidably guide a trip in the form of a plug or rivet which causes opening or closing of the switch in response to admission of fluid into the pressure chamber. The trip is preferably biased against the central portion of the diaphragm by a suitable spring installed in the second chamber.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved switch itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a partly elevational and partly axial sectional view of a fluid pressure actuated diaphragm switch which embodies one form of our invention, the diaphragm being shown in unstressed condition;

FIG. 2 is a similar view of the switch but showing the diaphragm in stressed condition;

FIG. 3 is an axial sectional view of the diaphragm as it appears prior to insertion into the housing of the switch;

FIG. 4 is an axial sectional view of a second diaphragm;

FIG. 5 is an axial sectional view of a third diaphragm; and

FIG. 6 is a fragmentary axial sectional view of a housing which forms part of a modified switch.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The fluid pressure actuated diaphragm switch of FIG. 1 comprises a metallic housing or casing 1 having a lower portion 2 surrounding a pressure chamber or plenum chamber 3 for a pressurized fluid which can be admitted through an inlet here shown as a nipple 4 which is integral with the housing 1. The discharge end of the central bore 5 in the inlet 4 is adjacent to the bulging central portion 8a of a disk-shaped diaphragm 8 whose marginal portion 8b extends into an annular recess or groove 7 provided in the internal surface of the housing 1. The lower axial end of the recess 7 is bounded by an annular shoulder 6 of the housing 1. The marginal portion 8b of the diaphragm 8 has a cylindrical peripheral surface 8' which is illustrated in FIG. 3, the latter showing the diaphragm as it appears prior to insertion into the housing 1. The diaphragm consists of oil-resistant elastic material, preferably rubber or synthetic plastic, and is produced by injection molding. The diameter of the recess 7 is smaller than the diameter of the peripheral surface 8' in unstressed condition of the diaphragm.

The upper axial end of the recess 7 is bounded by a radially outwardly extending shoulder 9 of the housing 1 which serves as a seat for a disk-shaped partition 10 constituting a back support for the central portion 8a of the diaphragm 8 when the latter is stressed in response to admission of a gaseous or liquid fluid through the bore of the inlet 4. The partition is received in a second annular recess 11 of the housing 1 which is adjacent to and whose diameter is larger than that of the recess 7. The axial length or width of the recess 7 (between the shoulders 6 and 9) is slightly greater than the thickness of the marginal portion 8b of the diaphragm 8. For example, the width of the recess 7 may exceed the thickness of the marginal portion 8b by one or more tenths of a millimeter, preferably no more than one millimeter. Since the diameter of the peripheral surface 8' exceeds the diameter of the recess 7, the diaphragm 8 is deformed in response to insertion into the housing 1 and its central portion 8a bulges away from the partition 10, i.e., into the pressure chamber 3. In other words, the material of the marginal portion 8b of the diaphragm 8 is forced from all sides toward the center of the diaphragm. The space between the downwardly bulging central portion 8a and the underside of the partition 10 (as viewed in FIG. 1) accommodates the head 14 of a reciprocable rivetshaped trip 13 whose stem 15 extends through a central aperture 16 of the partition and whose disk-shaped upper end 14a extends into a second chamber 17 of the housing 1. The head 14 bears against the concave side of the central portion 8a of the diaphragm 8 and the disk-shaped upper end 14:: is biased downwardly by a helical return spring 14b accommodated in the chamber 17. The end portion 14a can complete an electric circuit between two

electric contacts

17a, 17b in the second chamber 17 or it can move these contacts upwardly to thereby open or close the switch. The numeral 12 denotes an annular bead which overlies the upper side of the partition 10 and is formed by upsetting a portion of the housing 1 above the second recess 11. This bead 12 holds the partition 10 in the illustrated position and permanently locks the diaphragm 8 in the space below the partition.

FIG. 1 illustrates the switch in inoperative position, i.e., when the diaphragm 8 is unstressed because the bore '5 of the inlet 4 is sealed or disconnected from a source of pressurized fluid. If the bore 5 admits fluid, the central portion 8a of the diaphragm 8 is stressed and undergoes deformation in a manner as shown in FIG. 2. The bulge of the central portion 8a is reduced and a larger part of this central portion bears against the underside of the partition 10. Of course, the thickness of the marginal portion 8b of the diaphragm 8 increases in response to flattening of the central portion 8a whereby the marginal portion completely fills the recess 7 and provides a fluidtight seal between the

chambers

3 and 17. In other words, the thickness of the marginal portion 8b of the diaphragm 8 then equals the axial distance between the shoulders 6 and 9, and such thickening takes place in response to relatively small flattening of the central portion 8a. The marginal portion 8b is then tightly clamped between the shoulder 6 and partition 10, and such clamping or sealing action improves in response to increasing fluid pressure in the chamber 3, namely, in response to progressing flattening of the central portion 8a. It was found during actual testing that the diaphragm 8 can readily withstand extremely high pressures in the range of atmospheres above atmospheric pressure without any leakage of fluid into the chamber 17. When the diaphragm 8 is stressed in a manner as shown in FIG. 2, the central portion 8a displaces the trip 13 whereby the upper end portion 14a of the trip engages the

contacts

17a, 17b and thus actuates the switch, for example, by moving the contacts upwardly. The stem 15 is guided in the aperture 16 so that it prevents tilting of the trip 13. If the pressure of fluid in the chamber 3 drops, the diaphragm 8 reassumes its unstressed or normal condition and its central portion 8a again assumes the shape shown in FIG. 1. In the absence of the spring 14b, the trip 13 moves downwardly by gravity and is disengaged from the

contacts

17a, 17b. If the

contacts

17a, 17b are movable with reference to the housing 1, they also return to their normal positions as soon as the fluid pressure upon the diaphragm 8 is relaxed sufficiently to permit more pronounced bulging of the central portion 80.

FIG. 4 illustrates in section a second diaphragm 18 whose central portion 19 bulges prior to insertion into the housing 1. The diameter of this diaphragm 18 need not exceed the diameter of the recess 7. The bulge of the central portion 19 can be produced in a number of ways, for example, during injection molding or by deformation in response to localized heating. The thickness of the marginal portion 18a of the diaphragm 18 is less than or at most equals the width of the recess 7. The thickness of this marginal portion 18a may but need not be the same as the thickness of the central portion 19. When the diaphragm 18 is inserted into the housing of a pressure actuated switch, the central portion 19 :bulges into the pressure chamber, i.e., toward the inlet. When the inlet admits a pressurized fluid, the stressing of diaphragm 18 takes place in the same way as described in connection with FIG. 2 and the marginal portion 18a becomes thicker to provide a reliable seal between the pressure chamber and the second chamber. It is clear that the diameter of the diaphragm 18 may exceed the diameter of the recess 7 so that the diaphragm undergoes at least some deformation and the bulge of its central portion 19 increases in response to insertion into the switch housing. This also insures that the diaphragm seals the pressure chamber from the second chamber at all times, i.e., also when the inlet is disconnected from a source of pressurized fluid so that the fluid pressure in pressure chamber is the same as that in the second chamber.

It is also possible to employ a disk-shaped diaphragm which is absolutely or substantially flat prior to insertion into the switch housing and consists of semielastic material. On prolonged stay in the housing, the semielastic diaphragm retains the :bulge of its central portion even if it is removed from the housing. Thus, when a semielastic diaphragm is removed from the housing after a certain period of time, it resembles the diaphragm 18 of FIG. 4 even though it was originally a flat disk similar to the one shown in FIG. 3.

FIG. 5 illustrates a further diaphragm 20 which also resembles a flat disk and has a conical peripheral surface 20' composed of two conical portions which taper away from the respective axial ends. An advantage of the diaphragm 20 is that its marginal portion 20a can move into very satisfactory sealing engagement with the cylindrical or conical portion of the internal surface of a housing which surrounds the recess 7 or a similar recess. The two conical parts of the marginal portion 20a can provide a very satisfactory sealing action prior to admission of a fluid into the pressure chamber and they allow for more rapid radial and axial deformation of the marginal portion 20a in response to admission of fluid into the pressure chamber. In other words, the trip 13 or an analogous actuating device can operate the switch in response to a relatively small rise in fluid pressure in the pressure chamber. It was found that the diaphragm 20 of FIG. 5 is also very effective when the pressure chamber accommodates a fluid medium, i.e., that its sealing action is satisfactory not 'only in unstressed but also in stressed condition of the central portion.

Referring finally to FIG. 6, there is shown a modified switch housing 21 wherein the recess 22 is bounded by a conical portion of the internal surface of the housing. This recess 22 tapers away from the bore 5' of the inlet 4'. The partition is installed in a second recess in the same way as described in connection with FIG. 1. The diaphragm has been omitted for the sake of clarity, The conicity or taper of the recess 22 can be achieved by exerting upon the shoulder 9' of the housing 21 an axial pressure which reduces the diameter of the upper end of the recess 22. This recess can accommodate any one of the diaphragms -8, 18 and 20 and the conical surface portion bounding the recess 22 insures a very satisfactorysealing action in unstressed and/ or stressed condition of the diaphragm. The deformation or thickening of the marginal portion will begin in response to a relatively small fluid pressure, and the sealing action improves with increasing fluid pressure. The shoulder 23 corresponds to the. shoulder 6 of FIG. 1 and the numeral 17' denotes a contactcontaining chamber at the upper side of the partition 10.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of our contribution to the art and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. In a fluid pressure actuated switch, a combination comprising a housing having an internal surface provided with an annular recess of predetermined axial length and bounded by two axially spaced side faces and an annular bottom face having a predetermined diameter; a diaphragm consisting of elastomeric material, having a predetermined thickness and a predetermined diameter greater than the diameter of said annular bottom face, said diaphragm being inserted into said housing and having a circumferentially extended marginal portion received in said recess whereby the interior of said housing is divided into a pressure chamber and a second chamber, the thickness of said marginal portion being slightly smaller than said predetermined axial length of said recess and said diaphragm when inserted having a central portion bulging into said pressure chamber due to said predetermined diameter of said diaphragm which is greater than said predetermined diameter of said annular bottom face of said recess; and means for admitting into said pressure chamber a pressure fluid to compress said diaphragm with resulting radially outwardly directed pressure on said diaphragm whereby, due to resistance to such pressure by said annular bottom face of said recess, the material of said marginal portion is displaced in axial direction with concomitant thickening of said marginal portion whereby said marginal portion tightly engages said side faces of said recess and provides a fluid-tight sea between said chambers.

2. A switch as defined in claim 1, wherein said diaphragm has a diameter which approximates the diameter of said recess and said control portion defines an at least slightly pronounced bulge prior to insertion of said diaphragm into said housing.

3. A switch as defined in claim 1, wherein said dia phragm consists of oil-resistant material.

4. A switch as defined in claim 1, wherein said marginal portion of the diaphragm has a cylindrical peripheral surface.

5. A switch as defined in claim 1, wherein said marginal portion of the diaphragm has a conical peripheral surface.

6. A switch as defined in claim 1, wherein said recess tapers in a direction from one of said chambers toward the other chamber.

7. A switch as defined in claim 6, wherein the taper of said recess is due to deformation of a portion of said housing.

8. A switch as defined in claim 1, wherein said diaphragm is a flat disk whose diameter exceeds the diameter of said recess before said marginal portion is received in said recess.

9. A switch as defined in claim 1, said diaphragm having prior to insertion thereof into said housing a diameter which at least equals the diameter of said annular recess.

References Cited UNITED STATES PATENTS 2, 694,415 11/ 1954 Dillon. 2,284,424 5/ 1942 Hein 277-177 2,741,678 4/1956 Schaefer et a1. ZOO-83.9 3,093,716 6/ 1963 Horowitz 20083 3,218,051 11/1965 Doetsch 277-177 X BERNARD A. GILHEANY, Primary Examiner H. B. GlLSON, Assistant Examiner.

US. Cl. X.R. 337-306