US3581034A

US3581034A - Fluid-pressure-actuated switch

Info

Publication number: US3581034A
Application number: US805333A
Authority: US
Inventors: Karl Schupp; Hans Weismann
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1968-06-12
Filing date: 1969-03-07
Publication date: 1971-05-25
Anticipated expiration: 1988-05-25
Also published as: GB1208389A; FR2010730A6; DE1765576A1; AT284944B

Abstract

A fluid-pressure-activated switch has a housing provided with an internal annular recess for the marginal portion of an elastomeric 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. The diameter of the annular recess is equal to or smaller than the diameter of the diaphragm and the axial length of the recess is slightly smaller than or at most substantially equal to the thickness of the marginal portion of the diaphragm. The marginal portion includes an axially extending annular bead whose thickness is included in the thickness of the marginal portion and which has a lower resistance to deformation than the material of the remainder of the diaphragm so as to be moved in spite of unevenness on an associated sideface into tight sealing engagement with that face bounding one axial end of the recess when pressure is introduced into the pressure chamber, causing the central portion of the diaphragm to flatten out and to effect radial expansion of the diaphragm which, being resisted by contact of the diaphragm edge with the bottom wall of the contact of the diaphragm edge with the bottom wall of the recess, results in yielding of the material of the margin of the diaphragm in axial direction and thereby in an increase in the thickness of the margin.

Description

United States Patent [72] inventors Karl Schupp Pforzheim;

Hans Weismann, Stuttgart-Feuerbach, Germany [2 1] Appl. No, 805,333 [22] Filed Mar. 7, 1969 [45] Patented May 25, 1971 [73] Assignee Robert Bosch Gmbll Stuttgart, Germany [32] Priority June 12, 1968 [33] Germany [3!] P 17 65 576.4

[54] FLUlD-PRESSURE-ACTUATED SWITCH l 1 Claims, 1 Drawing Fig. [52] US. Cl 200/83, 92/98 [51] Int. Cl H0111 35/40 [50] Field of Search 200/83, 83.2; 92/47, 103, 98, 98 (RD) [56] References Cited UNITED STATES PATENTS 2,813,945 11/1957 Courtot 92/103X 200/ 83.2

3,465,112 9/1969 Reichertetal.

Primary Examiner-Robert K, Schaefer Assistant Examiner-M. Ginsburg AttorneyMichael S. Striker ABSTRACT: A fluid-pressure-activated switch has a housing provided with an internal annular recess for the marginal portion of an elastomeric 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. The diameter of the annular recess is equal to or smaller than the diameter of the diaphragm and the axial length of the recess is slightly smaller than or at most substantially equal to the thickness of the marginal portion of the diaphragm. The marginal portion includes an axially extending annular bead whose thickness is included in the thickness of the marginal portion and which has a lower resistance to deformation than the material of the remainder of the diaphragm so as to be moved in spite of unevenness on an associated sideface into tight sealing engagement with that face bounding one axial end of the recess when pressure is introduced into the pressure chamber, causing the central portion of the diaphragm to flatten out and to effect radial expansion of the diaphragm which, being resisted by contact of the diaphragm edge with the bottom wall of the contact of the diaphragm edge with the bottom wall of the recess, results in yielding of the material of the margin of the diaphragm in axial direction and thereby in an increase in the thickness of the margin.

PATENTEDHAYZSIQYI "155133;

N v i ylllllll IVIIA'OJ;

III

INVENTORS Karl SCHUPP Hclns WEISMANN y their ATTORNEYS BACKGROUND OF THE INVENTION The present invention relates .to fluid-pressure-actuated switches, and more particularly to fluid-pressure-actuate'd diaphragm switches.

' Still more specifically the invention concerns improvements in fluid-pressure-actuated diaphragm switches.

It is known to provide diaphragm switches whose housing accommodates a diaphragm having a marginal portion tightly clamped by a steel ring so that it undergoes axial compression. The diaphragm provided in this construction subdividcs the interior of the housing into a pressure chamber and an additional chamber which latter accommodates one or more electric switching contacts. The central portion of the diaphragm bulges into the pressure chamber and is deformed in response to admission of pressurized fluid, thereby contacting and actuating the switch contacts in the other chamber. The steel ring cooperates with an internal shoulder of the housing to clamp the marginal portion of the diaphragm tightly in place.

This prior art device suffers from the disadvantage that its various parts must be machined and assembled with a high degree of precision which contributes to high initial manufacturing costs andresults in large numbers of rejects because of tolerance variations. Furthermore, the clamping action of the steel ring must be very carefully selected to damage to the marginal portion of the diaphragm and the interior of the housing must be machined with a high degree of precision to insure satisfactory bulging of the diaphragm and to avoid uneveness on the aforementioned shoulder because this could result in damage to the clamped marginal portion of the diaphragm.

An attempt has been made to overcome these problems by providing a construction wherein the switch housing is provided with an internal annular recess which receives the marginal portion of an elastomeric diaphragm. Again, the central portion of the diaphragm bulges into the pressure chamber of the housing and oppositely the pressure chamber separated therefrom by the diaphragm is a second chamber containing one or more contacts. In the unoperated position of the switch the thickness of the marginal diaphragm portion is slightly smaller than or at most approaches the axial length of the recess in which the marginal portion is received. When fluid is introduced into the pressure chamber, the central portion of the diaphragm flattens out with the result that the diaphragm expands in radial direction. Because this radial expansion is resisted by contact of the diaphragm edge with the bottom wall of the recess, the material of the marginal portion of the diaphragm is compelled to yield in axial direction, thereby increasing the thickness of the marginal portion as a result of this material displacement so that the marginal portion now also bears fluidtightly against the sidewalls of the recess.

This type of construction has been found to be highly satisfactory except for one problem connected with the manufacture of the parts, namely the fact that the annular end faces bounding the recess in the housing, and against which the marginal portion of the diaphragm moves into sealing engagement in response to thickening of the marginal portion for the aforementioned reasons, may have unevennesses resulting from manufacture of the housing or possibly caused by careless handling or in some other manner. Of course, these unevennesses could be eliminated by additional manufacturing steps, but it is neither desired to resort to such steps which increase the initial manufacturing cost of the switch nor practical because the removal of additional material from one or both of these axial annular end faces would increase the axial length of the recess and would necessitate the provision of a nonstandard diaphragm to compensate for this increased axial length. Evidently, the manufacture and keeping in stock of such nonstandard diaphragms would also further increase the expense of the switch. Therefore it has heretofore been necessary, where such unevennesses exist and consequently deformation of the diaphragm will not result in the desired sealing action, to discard the thus-defective switches as rejects.

SUMMARY OF THE INVENTION It is, accordingly, an object of the present invention to overcome the aforementioned drawback.

A more particular objectof the present invention is to provide an inexpensive, compact and highly reliable fluid-pressure-actuated diaphragm switch which is not possessed of the aforementioned drawback.

An additional object of the invention is to provide such a diaphragm switch which will operate properly even if its component parts are not machined or otherwise finished with any significant degree of precision.

A concomitant object of the invention is to provide a diaphragm switch of the type in question wherein the marginal portion of the diaphragm is not clamped in the housing but wherein the diaphragm is still capable of preventing the escape of fluid from the pressure chamber into the other chamber.

In pursuance of the above objects and others which will become apparent hereafter, one feature of our fluid-pressureactuated diaphragm switch resides in the provision of a housing having an internal surface which is provided with an annular recess of predetermined axial length and which is bounded by two axially spaced annular side faces and an an annular bottom face. 7

A diaphragm of elastomeric material is inserted into the housing and has a circumferentially extending margin which is received in the recess; thereby the interior of the housing is divided into a pressure chamber and a second chamber.

In accordance with the invention the margin is provided with a circumferentially extending annular bead projecting in axial direction of the diaphragm and having a resistance to deformation which is substantially smaller than that of the remainder of the diaphragm, the thickness of the margin is slightly smaller and the combined thickness of the margin and the head is only slightly larger than the predetermined axial length of the recess and the diaphragm when inserted having a central portion which bulges into the pressure chamber.

Means is provided for admitting into the pressure chamber a pressure fluid to thereby compress the diaphragm with resulting radially outwardly directed pressure thereon whereby, as a result of the resistance to such pressure offered by the annular bottom face, the material of the diaphragm margin including the bead is displaced in axial direction with concomitant thickening of the margin and tight engagement of the same with the side faces. Because of the smaller resistance to deformation exhibited by the annular bead the material of the latter intimately contacts the associated side face to provide a fluidtight seal even in the presence of surface unevennesses on the associated side face.

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

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompany drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a fragmentary axial section through a diaphragm switch according to the present invention in one embodiment; and

DESCRIPTION OF Tl-IEPREFERRED EMBODIMENTS Discussing .now the drawing in detail, and firstly the embodiment illustrated in FIG. 1, it will be seen that reference numeral 1 designates our novel diaphragm switch in general. Reference numeral 2 designates a metallic housing or casing provided with a pressurechamber 3 which is arranged to accommodate a pressurized fluid. Admission of such fluid into the pressure chamber 3 can be accomplished via an inlet 4, illustrated as a-nipple which is-integral with the housing 2 and which is provided with a central bore 5.

The discharge end of the central bore 5 is adjacent to the bulging central portion 8a of a substantially disc-shaped diaphragm 8 consisting advantageously of oil-resistant elastic material, such as rubber or synthetic plastic material and being produced by injection molding, stamping or in another suitable manner. v v

The interior of the housing 2 is provided with an annular recess or groove 7 in its internal surface and the lower axial end of this recess 7 is bounded by an annular shoulder 6 of the housing 2 whereas the upper axial end is bounded by a radially outwardly extending shoulder 9 of the housing 2. The groove 7 further has an annular bottom face 26. The diaphragm 8 is provided with a marginal portion 8b located in the recess 7 and the diameter of the recess 7, that is measured across the annular bottom face 26 thereof, is smaller than the diameter of the diaphragm in the unstressed condition thereof, that is the condition illustrated in FIG. I.

The side face 9 constituting the upper axial end of the recess 7 serves as ase'at for a disc-shaped reinforcing partition I which is apertured and which serves as a-support for the central portion 8a of the diaphragm, 8 when the diaphragm is stressed as 'a, result of admission of pressure fluid through the bore of theinlet 4 into the chamber 3. The partition 10 is received in a second annular recess 11 of the'housing 2 adjacent to the recess 7 and having a diameter larger than that of the recess 7. An annular projection 12 overlies the upper side of the partition l0 and may be formed by upsetting a portion of the housing 2 above the second recess 11 whereby the partition 10 is maintained in the illustrated position and the diaphragm 8 is permanently locked in the space below the partition.

As shown in FIG. 1 the axial end face or side face 6 is assumed to have. unevennesses which are identified with reference numeral 25. Such unevennesses may result from manufacturing, from careless handling, or for any other reason whatsoever. To assure that a seal is provided despite the unevennesses on the side face 6, the margin 8b of the diaphragm 8v is provided with an axially extending circumferential annular bead 27 and the axial thickness of the margin 8!; is slightly smaller than the axial thickness of the recess, and the combined axial thickness of the margin 86 and the bead 27 is equal or slightly longer than the axial length of the recess 7 between thefaces 6 and 9 thereof. The difference may be on the order of one or more tenths or a millimeter.

In accordance with our invention the bead 27 has a resistance to deformation which is significantly smaller than that of the remainder of the diaphragm 8;

Because the diameter of the diaphragm 8 exceeds the diameter of the'recess 7, or rather the annular bottom face 26 thereof, the diaphragm is deformed when it is inserted into the housing 2 and its central portion 8a bulges away from the partition l0 intothe pressure chamber 3, However, it is also possible to so dimension" the diaphragm that its diameter will be indentical with that of the bottom face 26 of the recess 7 and that the diaphragm will be provided with an inherent bulge,-rather than being caused to btilge because of its larger diameter.

In any case, ifa pressure fluid is adrhitted through the bore 5 into the chamber 3, the central portion 8a of the diaphragm 8 is stressed and deflected towards and into engagement with the partition 10. Thus the bulge ofthe central portion 8a is reduced and the diaphragm flattened out. This results in displacement of the material of the diaphragm 8 in radial direction, that is in radial expansion of the diaphragm 8. Because this radial expansion is resisted'by contact of the marginaledge face of the diaphragm 8 with the bottom face 26 of the recess 7, the material of the margin 8b and of the bead 27 yields and seeks the way of least resistance, which is escape in axial direction. In other words, the combined thickness of the margin 8b and of the bead 27 increases so that in spite of the unevennesses'on the side face 6 the two together completely :fill therecess 7 engaging the side faces 6 and 9 and providing a fluidtight seal between the chamber 3 and the other chamber in which the partition 10 is located. The margin'8b and the bead 27 are in this condition tightly clamped between the side faces 6 and 9 and the degree of such clamping or sealing action improves in response to increasing fluid pressure in the chamber 3, or, in other words, in response to progressive flattening of the central portion 8a of the diaphragm 8.

Testing has shown that the diaphragm 8 can readily withstand extremely high pressures in the range of 100 atmospheres above atmospheric pressure without any leakage of fluid out of the chamber 3 intothe other chamber. F lattening of the diaphragm 8, or rather of its bulging portion 8a, results in suitable manner in operation of the switch contacts in the other chamber which is to be sealed from the pressure chamber, and this has not been illustrated because it is already known and is not a part of the present invention. V

Because of the significantly'smaller deformation resistance of the bead 27that is smaller by comparison with the remainder of the diaphragm 8-e ven very small pressures with concomitant small extent of flattening of the bulging portion will result in tight intimate engagement of the head 27 with the side face 6, and furthermore the small resistance to deformation will allow the material of the bead 27 to accommodate itself plastically to the unevennesses of the side face 6. Thus, the seal tightness between the chamber 3 and the other chamber containing the pushrod 28 which is displaced by the diaphragm and operates the diagrammatically shown contacts, is guaranteed regardless of unevennesses existing on the side face 6. This eliminates any necessity for precision treatment of the side face 6 and, atthe same time, eliminates the particular condition which has heretofore been the cause of many rejects among switches of this type.

While in FIG. 1 we have illustrated an embodiment wherein the side faces 6 and 9 are located in two axially spaced parallel planes, FIG. 2 illustrates a slightly modified embodiment wherein the side face 6', corresponding to the side face 6 in FIG. I, is inclined with respect to the axis of the recess 7 and with respect to the side face 9. This is clearlyillustrated in the drawing and the purpose is to assure better guidance of the displaceable material of the diaphragm 8 in outward direction against the annular bottom wall 26 of the recess 7.

It will be appreciated that reduction or termination of pressure in the chamber 3 results in return of the diaphragm 8 to its unstressed condition and concomitant decrease in the axial thickness of the margin 8b and the bead 27.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.

While the invention has been illustrated and described as embodied in a fluid-pressure-actuated diaphragm switch it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

We claim:

I. A fluid-pressure-actuated switch, comprising a housing having an internal surface provided with an annular recess of predetermined axial length and bounded by two axially spaced annular side faces and a circumferential face; an apertured partition in said housing and having an annular marginal face.

diaphragm of elastomeric material inserted into said housing and having acircumferentially extending margin received in said recess adjacent to said partition whereby the interior of said housing is divided into a pressure chamber and a second chamber, said margin being provided with a circumferentially extending annular bead projecting in axial direction of said diaphragm and having a resistance to deformation which is substantially smaller than that of the remainder of said diaphragm, said margin'having an axial thickness slightly smaller than said predetermined axial length of said recess and said margin and said bead having a combined thickness only slightly larger than said predetermined axial length of said recess, and said diaphragm when inserted having a central portion bulging into said pressure chamber; means for admitting into said pressure chamber a pressure fluid to compress said diaphragm with resulting deflection of said central portion into said second chamber and radially outwardly directed expansion of said diaphragm whereby, due to resistance to such expansion by said circumferential face and said partition, the material of said margin is displaced in axial direction with concomitant thickening of said margin and said bead and tight engagement of the same with said annular marginal face, said circumferential face and the other of said side faces and due to the smaller resistance to deformation 'of said annular bead the material of the latter intimately contacts the associated side face to provide a fluidtight seal even in the presence of surface unevenness on said associated side face; and contact means in said second chamber and displaceablc from one operational mode to another operational mode in response to deflection of said central portion into said second chamber.

2. A switch as defined in claim 1, wherein said diaphragm is a disc whose diameter exceeds the diameter of said recess before said margin is received in said recess.

3. A switch as defined in claim 1, said diaphragm consisting of oil-resistant material.

4. A switch as defined in claim 1, said margin of said diaphragm having a cylindrical peripheral surface.

5. A switch as defined in claim 1, said circumferential face being a cylindrical face.

6. A switch as defined in claim 1, that one of said side faces which is associated with said bead being located in a plane normal to the axis of said recess.

7. A switch as defined in claim 1, that one of said side faces which is associated with said bead being inclined with reference to the axis of said recess.

8. A switch as defined in claim 1, said side faces being located in spaced parallel planes extending normal to the axis of said recess.

9. A switch as defined in claim I, the relationship between the deformation resistance of said annular bead and that of the remainder of said diaphragm being so selected that compression of said diaphragm with corresponding radially outwardly directed pressure results in deformation of said bead into intimate fluidtight engagement with its associated side face already upon initiation of deformation of the remainder of said diaphragm.

10. A switch as defined in claim I, wherein said diaphragm except for said bead consists of semieleastic material.

11. A switch as defined in claim 1, wherein said diaphragm is so dimensioned that its diameter will be identical or a little smaller than that of the circumferential face of the recess and that the diaphragm will be provided with an inherent bulge.

Claims

1. A fluid-pressure-actuated switch, comprising a housing having an internal surface provided with an annular recess of predetermined axial length and bounded by two axially spaced annular side faces and a circumferential face; an apertured partition in said housing and having an annular marginal face located in the general plane of one of said side faces; a diaphragm of elastomeric material inserted into said housing and having a circumferentially extending margin received in said recess adjacent to said partition whereby the interior of said housing is divided into a pressure chamber and a second chamber, said margin being provided with a circumferentially extending annular bead projecting in axial direction of said diaphragm and having a resistance to deformation which is substantially smaller than that of the remainder of said diaphragm, said margin having an axial thickness slightly smaller than said predetermined axial length of said recess and said margin and said bead having a combined thickness only slightly larger than said predetermined axial length of said recess, and said diaphragm when inserted having a central portion bulging into said pressure chamber; means for admitting into said pressure chamber a pressure fluid to compress said diaphragm with resulting deflection of said central portion into said second chamber and radially outwardly directed expansion of said diaphragm whereby, due to resistance to such expansion by said circumferential face and said partition, the material of said margin is displaced in axial direction with concomitant thickening of said margin and said bead and tight engagement of the same with said annular marginal face, said circumferential face and the other of said side faces and due to the smaller resistance to deformation of said annular bead the material of the latter intimately contacts the associated side face to provide a fluidtight seal even in The presence of surface unevenness on said associated side face; and contact means in said second chamber and displaceable from one operational mode to another operational mode in response to deflection of said central portion into said second chamber.

9. A switch as defined in claim 1, the relationship between the deformation resistance of said annular bead and that of the remainder of said diaphragm being so selected that compression of said diaphragm with corresponding radially outwardly directed pressure results in deformation of said bead into intimate fluidtight engagement with its associated side face already upon initiation of deformation of the remainder of said diaphragm.

10. A switch as defined in claim 1, wherein said diaphragm except for said bead consists of semieleastic material.