US3119910A - Pressure switch - Google Patents

Description

Jan. 28, 1964. D. T. MEISENHEIMER. JR., ETAL 3,

PRESSURE swncu Filed Oct. 2, 1959 2 Sheets-Sheet 1 F|G.1 H 34 INVENTORS DANIEL T. MEISENHEIMEFSIK LOUIS W. SYARTO Jan. 28; 196 D. T. MEISENHEIMER. JR.. ETAL 3,

PRESSURE SWITCH Filed Oct. 2, 1959 2 Sheets-Sheet 2 FIG. 3

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INVENTORS DANIEL T. MEISENHEIMERJR.

LOUIS w. SYARTO ATTORNEY United States Patent 0 3,119,919 PRESESURE SWITCH Daniel T. Meisenheimer, .Ir., 50 Morris Lane, Milford,

Conn, and Louis W. Syarto, 184 Highlawn Road, Fairfield, Conn.

Filed 9st. 2, 1959 Ser. No. 84 %,899 13 Claims. (Cl. MIL-83) The present invention relates generally to fluid pressure switches and particularly to shock resistant fluid pressure switches and mounting brackets therefor.

The present invention contemplates improvements in fluid pressure switches of the type which are actuated by a single reference fluid pressure. Switches of this type have been constructed having a diaphragm or piston movable by a reference pressure, the diaphragm or piston movement serving to actuate a small electrical switch. Such prior art devices have also included means for adjusting the spring tension of a coil spring or similar member which resists the movement of the piston or diaphragm, so that in effect, the actuation pressure of the switch may be varied. Known prior art switches, however, have been somewhat lacking in their ability to withstand severe shocks or the application of G loads which in some modern aircraft or missile applications may reach a value in excess of 25 GS.

The purpose of the present invention in its broader aspects is to provide a fluid pressure switch of the type mentioned which is better able to withstand severe shocks or G loads than prior devices of this type. In keeping with this purpose, the present invention also provides in combination with the aforementioned switch, means for mounting the switch to an aircraft or missile. This mounting means is particularly able to isolate the switch elements from shock while the mount is specifically designed to withstand high G loads without bending.

As a more specific aspect of the invention, a switch housing is provided having a principal member of rigid single piece construction, this member being adapted to receive two end members whereby the housing enclosure is completed. A diaphragm responsive to a reference pressure is provided and is supported within one of the end members. The opposite end member provides a mount for a small electrical switch which is completely enclosed within the housing. Intermediate the diaphragm is a switch actuation mechanism, longitudinally movable by the diaphragm in one direction and urged in an opposite direction by spring means. The pressure of the spring means acting against the actuation mechanism may be varied by the translatory longitudinal movement of an adjusting member. The adjusting member is threadably engaged with a control member which when rotated, causes a corresponding translatory movement of the adjusting member. This latter movement reduces or increases the pressure of the spring means against the switch actuation mechanism, thereby changing the reference pressure required to actuate the switch. The entire spring adjusting mechanism is enclosed within the aforementioned rigid single piece portion of the housing.

As a further and more specific aspect of the invention, the translating spring adjusting member may be restrained from rotation and may be guided in its longitudinal translatory movement by a plurality of pins which are mounted to the housing. In one form of the invention, portions of the switch actuating mechanism may be guided in their longitudinal movement by a part of the spring adjusting mechanism, so that forces acting upon the switch in a direction normal to its longitudinal axis will be relatively unlikely to influence the longitudinal movement of the switch actuation mechanism.

Another feature of the invention lies in the construction of a novel switch mounting bracket which contributes to the shock resistant properties of the pressure switch. In its broader aspects, the mounting bracket is attached to the principal portion of the housing by means of a single bolt. This bolt is substantially centrally located in the mounting bracket and is insulated in its attachment thereto by being embedded in a shock resistant material. The bracket also includes two longitudinal arms which rest against widely spaced portions of the housing. Each of the arms include shock absorbing members. The spaced arms are adapted to be clamped against the exterior of the housing when the mounting bolt is tightened in its mooring within the housing wall. Thus, the construction of the mounting bracket is such that there will be no direct metal to metal connection between the switch and the bracket. The intervening shock absorbing material, therefore, acts to insulate the switch from external vibration or shock. Also, the spaced arm construction provides a unique distortion-free design adapted to resist severe deflections, such as high G loads.

These and other specific aspects of the invention have been provided which will become more readily apparent after a detailed examination of the following description and the accompanying drawings in which:

FIG. 1 is an elevational View of a preferred embodi merit of a pressure switch incorporating the present inventions shock resistant and anti-G features;

FIG. 2 is a top view of the embodiment of FIG. 1 disclosing more specifically certain of the mounting provisions of the invention;

FIG. 3 is a cross sectional view taken along the lines 33 of FIG. 1; and

FIG. 4 is a cross-sectional View, similar to FIG. 3, but partially broken away, showing a modification according to the invention.

With reference to FIG. 3, a pressure switch 10 constructed according to the present invention has been illustrated. Switch It) includes a substantially hollow longitudinal body member "'12 of rigid single piece construction. At its upper end, body member 12' has been provided with internal threads 14 which are adapted to engage in corresponding threaded relationship with an externally threaded end member or plug 16. Plug 16 has been provided with an O-ring seal 17 so that when the parts 12 and 16 are threaded together, a sealed closure of the upper end of member 12 will be effected. Plug 16 serves as a mount for a small electrical switch 18 which is attached to the underside thereof by means of a bracket 2t and mounting screws 22. Switch is has been provided with terminals 24 and 26 which are connected externally of the switch housing to a suitable mechanism which is to be controlled by switch 18. Exterior terminals 28, 349 and 32 provided for this purpose have been shown in FIG. 2. The upper end of a terminal post 34 has been threaded externally so as to be adapted to engage with a mating electrical connector (not shown). A polyethylene cap 36 may also be provided, which serves as a dust cover when the switch is not being used.

The lower end of the body member 12. is likewise provided internally with a series of threads 38 which are adapted to engage with corresponding external threads provided on a lower end plug 40. Body member 12 has been formed with an annular shoulder 42 against which a spacer 44 will abut when plug 46) has been brought into full threaded engagement with member 1 2. The outer periphery 46 of a diaphragm 48 is held tightly between Washer 44 and plug 40. Plug it! has been provided with an internally threaded port 5i) which may be connected to a fluid pressure line (not shown). By this means the reference pressure may act against the lower surface of a diaphragm 48, this pressure being prevented from escaping between Washer 44 and plug 40 by means of a seal 52.

Immediately above the diaphragm 48 and resting against its upper surface, is a piston-like member 54 which is adapted to move in an upward longitudinal direction whenever the diaphragm is deflected by the reference pressure. The movement of piston 54 is transmitted to a pushrod 56 whose upper end is in contact with an actuating button 58 forming part of switch 18. A coil spring 66 hearing against an abutment 61 of piston 54 urges piston 54 downwardly against diaphragm 4 8. Actuation of switch 18 is prevented until a certain specific reference pressure is exceeded, this pressure being determined by the exposed diaphragm area, and the pressure of the spring. The design of the switch is such that it permits interchangeability of diaphragms having different areas or of diaphragms composed of different materials. Thus, a switch may be altered so that it will respond to pressures in widely different ranges.

In order that the response of a switch within a given pressure range may be adjusted or calibrated, the invention provides a means for varying the spring force exerted against the actuating piston 54. Situated above piston 54 body member 12 has been formed having a transverse integral wall section 62 which contributes to the rigidity of the switch construction. In addition, wall 62 serves as a mounting support for a plurality of longitudinally disposed pins 64. Pins 64 each have one end fastened within wall 62 so that the pins depend from wall 62 in a downward direction. Pins 64 serve to support a spring adjusting member in the form of a collar 66 which is adapted to slide longitudinally thereon. The lower end of collar 66 abuts an upper portion of the spring 66 and will therefore cause a greater or lesser compression of the spring depending upon the longitudinal position of collar 66 within the housing. A control member 68 which is threadably engaged at 70 with collar 66 may be rotated to cause longitudinal translation of collar 66. The control member 68 has an upper annular bearing surface 72 and a lower annular bearing surface 74 which corresponds in diameter to the internal diameter of body member 12, and the member 68 will thereby be guided in its rotation within body member 12 of the switch housing by the bearing surfaces 72 and 74.

With reference to FIG. 1, it will be observed that two oppositely disposed access windows or openings 76 have been provided in the body member 12. Furthermore, a portion of the control member 68 has been provided with grooves or teeth 77 which are accessible through the openings 76. Teeth 77 may be engaged by a tool such as a screwdriver, in order to cause rotation of the control member 63 and thus, adjustment of spring 60. After the adjustment has been made, locking screws '78 may then be tightened against teeth 77 of member 63 to prevent further movement thereof.

With reference to FIG. 3, collar 66has been provided with a central opening 79, which is adapted to receive an intermediate portion of pushrod 56. Collars 66 therefore assists in guiding pushrod 56 as it is moved longitudinally toward or away from switch 18. A longitudinally aligned passage 82 has also been provided in wall 62 to permit the passage of the upper end of pushrod 56.

The operation of the pressure switch shown in FIGS. l-3 is as follows:

Port will be connected to a reference pressure which will act against the exposed lower surface of diaphragm 48. When the reference pressure has achieved a high enough value, diaphragm ddwill be deflected upwardly, thereby causing piston 54 to move pushrod 56 sufiiciently to actuate switch button 58 and switch 18. The effective pressure required to actuate the switch will depend upon the diaphragm area and upon the resisting pressure of spring 60. Resistance of spring may be varied in order to change the actuation pressure of the switch. This is accomplished by inserting a tool such as a screwdriver through one of the windows 76 provided within the body member 12 of the switch housing and by rotating the control member 68 to the right or to the left. Rotation of member 68 will cause collar 66- to translate upwardly or downwardly along pins 64. The travel of collar 66 will cause greater or less compression of spring 60, thereby adjusting the actuation pressure of the switch;

FIG. 4 illustrates a modification according to the invention. In this form a piston having an elongated upper section ill of cylindrical cross-section rests against the upper surface of diaphragm 112. The elongated sec-' tion of the piston has a hollow bore 114 which is adapted to receive a pushrod 116 so that upward movement of the piston caused by deflection of the diaphragm will cause actuation of the switch 118. The upper portion of the elongated section of the piston is adapted to be received within a mating bore located Within a collar 1 20 so that piston 116 will be guided in its upward movement by means of the sliding fit between elongated section 111 and collar 12%. Collar abuts the upper end of a stack spring 121 whose lower end is retained by an annular shoulder T22 of the piston 11!). Collar 129 is supported by a plurality of pins which restrain the collar from rotation but permit limited translatory movement thereof in a downward or upward direction. As in the embodiment of FIGS. 1-3, collar 12% is caused to translate in a longitudinal direction by means of a rotatable control member 139 which is threadably engaged therewith. Thus, in the modification of FIG. 4, .the upper elongated section 111 of the piston lltl is slidably fitted within the spring adjusting collar 126 while the piston contributes to the lateral support of the stack spring. This construction is particularly adapted to Withstand transverse shocks because of the mutual support provided by the various longitudinally movable elements.

in combination with the pressure switch just described, the invention also provides a novel shock nrount which is adapted to cooperate with the structure of the switch in minimizing the effects of shock and/or high G loads upon the moving parts thereof. Accordingly, a single mounting bolt 84 is threadably secured at one end to member 12 of the switch housing. The other end of bolt passes through a resilient grommet 86 which has shock absorbing qualities. Grommet 86 has been provided with an annular groove 8 8 which is adapted to receive a portion of a vibration isolator 92.

As is best seen in FIG. 2, vibration isolator 92 has been constructed to encircle approximately three quarters of the periphery of the switch housing.

T wo shock- absorbent strips 94 and 96 are attached re spectively to the inner upper and lower edges of vibt aw tion isolator 92. The attachment of these strips to the isolator may be made by the use of modern high-strength adhesives. Isolator 92 carrying strips 94- and 96, will be brought up tightly against the switch housing by tightening bolt 84. In an alternate construction (not shown) strips 94 and 96 may also be bonded to the exterior of the hensing, and provided that the bonding material has suflicient strength, mounting bolt 84 nray be eliminated entirely.-

The novel shock mount also includes a mounting bracket 97 which is attached to the vibration isolator 92 by means of bolts 93. Mounting bracket 97 has been provided with a dished-in area 99 having an opening 11% therein, which gives access to the head of bolt 84. As will be observed with reference to FIGURES 1 and 2, the mounting bracket 97 has been formed to have a flat web portion 101 which is adapted to be mounted to a partition in an aircraft or missile. For this purpose attaching holes 102 and 103- hiave been provided. The upper and lower legs 1% and of the mounting bracket 97 have been constructed in the form of sheet metal arms which encircle approximately one-half of the vibration isolator. 92. Bolts 9i which attach mounting bracket 97 to the vibnation isolator 92 will be tightened sufficiently .to assure that top and bottom legs 104 and 105 of the mounting bracket will be clamped tightly about the periphery of vibration isolator 92.v

It will be observed that the combination of the vibration isolator 92 and the mounting bracket 97 provides a shock mount which, though made of sheet metal, has the strength of a casting. The arms of the vibration isolator 92 bear against the exterior of the switch housing 12 at widely spaced longitudinal points while the genenally cylindrical shape of isolator 92 imparts great longitudinal rigidity to this member. The combination of the mounting bracket and isolator is such that the rigidity of isolator 92 will prevent bending of legs Mid and 1% when the switch is subjected to vertical loads. Furthermore, the legs 1634 and MP5 of mounting bracket 97 which encircle the vibration isolator 92 are designed specifically to resist lateral bending forces. Finally, the vibration isolator itself is so constructed that no direct metal-to-metal connection is made between the switch housing and the structure to which it is mounted. lit has been found that a shockmount constructed according to the invention is well able to resist deflections in excess of twenty-five Gs.

Thus, it will be seen that the present invention provides a pressure switch having a housing of substantially singlepiece construction, the rigidity of the housing contributing substantially to the shock-resistance properties of the switchactuating elements enclosed therein. in combination with the switch the invention also provides a unique shock-resistant mount which is adapted to isolate the switch from vibrations which otherwise might be transmitted from the structure to which it is mounted. While providing vibration isolation, the construction of the shock mount is such that it can resist deflections from extremely highlongitudinal and transverse forces.

It will be appreciated that the invention though described in connection with a. pressure switch may actually assume the form of a pressure actuator for devices other than switches. In this broader form, the novel pressure responsive structure disclosed may be employed to actuate a potentiometer, a linear variable differential transformer, or other suitable devices. It should therefore be understood that the foregoing description is directed to a preferred embodiment of the invention and is representative only. Various departures from what has been shown and described may be made within the spirit and scope of the invention as more particularly defined in the appended claims.

We claim:

1. In a fluid pressure switch of the type having a housing, a port at one end of said housing adapted to be connected to reference pressure, pressure responsive means movable by said pressure, the movement of said pressure responsive means being transmitted in one direction longitudinally of said housing to a switch actuator, resilient means urging said actuator in an opposite direction, a switch adapted to be actuated by said switch actuator, and adjusting means acting upon said resilient means for adjusting the resiliency thereof, the improvement comprising a housing for said fluid pressure switch including a generally longitudinally disposed body member of rigid single-piece construction, said longitudinally disposed body meiiber being provided with an access opening, said housing also including two end members attached to said longitudinal body member in sealed relation, a first one of said end members defining said reference pressure port and providing structural support for said pressure responsive means, a second one of said end members providing support for said switch, said adjusting means comprising a collar, control means being threadably engaged with said adjusting means such that rotation of said control means causes translatory movement of said collar and adjustment of said resilient means, guide means within said housing to support said adjusting means and accommodating longitudinal adjusting movement thereof, said control means being mounted within said housing and in a surrounding relation to said adjusting means, said control means cooperating with said adjusting means for causing longitudinal movement thereof, said guide means acting to restrain said collar v6 from rotation when said control means is rotated, and sealing means associated with said control means and said housing serving to isolate said adjusting means from said access opening.

2. In a fluid pressure switch of the type having a hous ing, a port at one end of said housing adapted to be connected to a reference pressure, pressure responsive means movable by said pressure, the movement of said pressure responsive means being transmitted in one direction longitudinally of said housing to a switch actuator, resilient means urging said actuator in an opposite direction, a switch adapted to be actuated by said switch actuator, and adjusting means acting upon said resilient cans for adjusting the resiliency thereof, the improvement comprising a housing for said fluid pressure switch including a generally longitudinally disposed body member of rigid single-piece construction, said longitudinally disposed body member being provided with an access opening, said housing also including two end members attached to said longitudinal body member in sealed relation, a first one of said end members defining said reference pressure port and providing structural support for said pressure responsive means, a second one of said end members providing support for said switch, guide means within said housing supporting said adjusting means and accommodating longitudinal adjusting movement thereof, control means being mounted within said housing and in surrounding relation to said adjusting means, said control means cooperating with said adjusting means for causing longitudinal movement thereof, said adjusting means comprising a collar and said control means being threadably engaged with said adjusting means such that rotation of said control means causes translatory movement of said collar and adjustment of said resilient means, said collar being supported by said guide means, said guide means comprising a plurality of longitudinally disposed pin leans mounted to said housing, said pin means acting to restrain said collar from rotation when said control means is rotated, and sealing means associated with said control means and said housing and serving to isolate said adjusting means from said access opening.

3. A pressure switch according to claim 1 wherein said resilient means comprises a spring and said switch actuator includes a push-rod, one end of said push-rod is in contact with said pressure responsive means, the other end of said push-rod is adapted to cause actuation of said switch.

4. The combination of a fluid pressure switch and a shock mount, said fluid pressure switch comprising a housing, means forming a port at one end of said housing adapted to be connected to a reference pressure, diaphragm means movable in response to said pressure, said diaphragm movement being transmitted in one direction longitudinally of said housing to a switch actuator, spring means urging said actuator in an opposite direction, a switch adapted to be actuated by said switch actuator, means acting upon said spring means for adjusting the compression of said spring means, said housing including a generally longitudinally disposed body member of rigid single-piece construction having a transverse wall integral therewith, said housing also including two end members enclosed by and attached to said longitudinal body member, one of said end members defining said reference pres,- sure port and providing structural support for said diaphragm, the other of said end members providing support for said switch, guide means within said housing supporting said spring adjusting means and adapted to permit longitudinal movement thereof, said switch actuator including a longitudinally slidable piston and a pushrod, one end of said piston being in direct physical contact with said diaphragm, the other end of said piston acting upon said push-rod adapted to cause actuation of said switch, said spring means comprising a coil spring, said spring adjusting means comprising a collar acting upon and adjusting the compression of said coil spring,

rotatable control means threadably engaged with said collar for causing longitudinal movement thereof, said collar adapted for longitudinal movement within said housing, said collar abutting one end of said spring, said guide means comprising a plurality of longitudinally disposed guide pins mounted on said transverse housing wall and supporting said collar, said guide pins acting to restrain said collar from rotation such that rotation of said control means causes longitudinal movement of said collar thereby adjusting the tension of said spring, said longitudinal body member having an opening in its exterior wall providing access to said rotatable control means whereby said spring may be adjusted from a position exterior to said housing; and a shock mount comprising a mounting pin having one end adapted to be threadably mounted within a portion of the switch housing, the op posite end of said mounting pin being embedded in and afiixed to a shock absorbing grommet, means for affixing said grommet to a vibration isolator, said isolator having two longitudinally spaced arms adapted to encircie and rest against the switch housing, said arms including shock absorption means, the mounting pin, grommet and isolator being constructed such that threading of the mounting pin into the switch housing will cause said mounting pin to clamp the spaced arms or" said isolator against the exterior of said housing, a mounting bracket having upper and lower legs adapted to rest against said isolator, and attaching means for aflixing said mounting bracket to said vibration isolator, said attaching means being adapted to clamp said mounting bracket tightly against said vibration isolator.

5. A shock mount for a switch or the like comprising a mounting pin having one end adapted to be fastened to a housing for said switch, the other end of said pin being affixed to a vibration isolator and insulated therefrom by an intermediate shock absorbing grommet, said isolator being adapted to rest against the exterior of said housing at spaced points, said isolator including shock absorbing means at said points, said mounting pin being adapted to cause said isolator to be clamped against said housing, and a mounting bracket having upper and lower legs adapted to rest against said isolator, attaching means for affixing said mounting bracket to said vibration isolator, said attaching means being adapted to clamp said mounting bracket tightly against said vibration isolator.

6. A pressure switch according to claim 5 wherein thevibration isolator is of substantially arcuate shape having 'two longitudinally spaced arms adapted to substantially encircle the switch housing, and said mounting bracket legs substantially encircle said isolator.

7. A shock mount for a switch housing or the like comprising a vibration isolator and a mounting bracket for said isolator, said isolator being constructed such that it will contact said switch housing at a plurality of widely spaced points, said points of contact including shockof shock-absorbent material which are adapted to contact the switch housing, said strips forming a part of said vibration isolator, and wherein the means for attaching the isolator to the switch housing comprises a bonding adhesive.

t? 9. A shock mount according to claim 7 wherein the means for attaching the vibration isolator to the switch housing comprises a mounting bolt which is threadably connected to the structure of the vibration isolator by means of a resilient shock-absorbent material.

10. A sheet metal shock mount for a switch housing or the like comprising a mounting bracket adapted to be fastened to fixed structure and an intermediate member adapted to be attached to said housing, said mounting bracket having a back and upper and lower legs generally perpendicular to said back, said legs defining a cutout against which upper and lower portions of said intermediate memher are adapted to nest, said intermediate member being constructed of a shape such that it offers great resistance to horizontal bending movements, and means for attaching said intermediate member to said mounting bracket.

11. A mount according to claim 10 wherein said intermediate member is of generally cylindrical shape and substantially encircles said housing.

12. A mount according to claim 10 wherein said intermediate member includes shock-absorbing means at those parts of said member which contact the housing.

13. A fluid pressure actuated assembly comprising a unitary, rigid body of generally tubular form, an actuated device mounted in sealed relation at one end of said body and having a movable element exposed to the interior of the body, means closing the other end of said tubular body in sealed relation and forming a pressure fluid port ."for connection to a source of pressure fluid, means within sive element exposed within said chamber, connecting means extending longitudinally through the interior of said tubular body and connecting said pressure responsive element with the movable element of said actuated device, a return spring located within said tubular body and acting longitudinally upon said pressure responsive element in opposition to said pressure fluid, a spring adjusting member received within said tubular body and acting longitudinally upon one end of said spring, means for guiding said spring adjusting member for longitudinal adjusting movement within said body, said tubular body having an access opening in a side wall portion thereof, a rotatable control member received within said tubular body in generally surrounding relation to said return spring and said spring adjusting member, said control member being accessible for rotation through said access opening and being operatively connected to said spring adjusting member to effect longitudinal movement thereof in accordance with rotation of the control member, and annular sealing means acting between said control member and interior walls of said tubular body on opposite sides of said access opening to seal the interior of said tubular body and the mechanism housed therein.

References tilted in the file of this patent UNITED STATES PATENTS 1,938,327 Green Dec. 5, 1933 2,182,450 Clarkson Dec. 5, 1939 2,638,303 Pietz May 12, 1953 2,742,544 Lovick Apr. 17, 1956 2,756,016 Panter July 24, 1956 2,789,176 Mercier Apr. 6, 1957 2,890,305 Gutkowski June 9, 1959 2,917,264 Hartenstein Dec. 15, 1959 2,919,882 Barkalow Jan. 5, 1960 2,924,420 Fink Feb. 9, 1960

Claims (1)

1. 2. IN A FLUID PRESSURE SWITCH OF THE TYPE HAVING A HOUSING, A PORT AT ONE END OF SAID HOUSING ADAPTED TO BE CONNECTED TO A REFERENCE PRESSURE, PRESSURE RESPONSIVE MEANS MOVABLE BY SAID PRESSURE, THE MOVEMENT OF SAID PRESSURE RESPONSIVE MEANS BEING TRANSMITTED IN ONE DIRECTION LONGITUDINALLY OF SAID HOUSING TO A SWITCH ACTUATOR, RESILIENT MEANS URGING SAID ACTUATOR IN AN OPPOSITE DIRECTION, A SWITCH ADAPTED TO BE ACTUATED BY SAID SWITCH ACTUATOR, AND ADJUSTING MEANS ACTING UPON SAID RESILIENT MEANS FOR ADJUSTING THE RESILIENCY THEREOF, THE IMPROVEMENT COMPRISING A HOUSING FOR SAID FLUID PRESSURE SWITCH INCLUDING A GENERALLY LONGITUDINALLY DISPOSED BODY MEMBER OF RIGID SINGLE-PIECE CONSTRUCTION, SAID LONGITUDINALLY DISPOSED BODY MEMBER BEING PROVIDED WITH AN ACCESS OPENING, SAID HOUSING ALSO INCLUDING TWO END MEMBERS ATTACHED TO SAID LONGITUDINAL BODY MEMBER IN SEALED RELATION, A FIRST ONE OF SAID END MEMBERS DEFINING SAID REFERENCE PRESSURE PORT AND PROVIDING STRUCTURAL SUPPORT FOR SAID PRESSURE RESPONSIVE MEANS, A SECOND ONE OF SAID END MEMBERS PROVIDING SUPPORT FOR SAID SWITCH, GUIDE MEANS WITHIN SAID HOUSING SUPPORTING SAID ADJUSTING MEANS AND ACCOMMODATING LONGITUDINAL ADJUSTING MOVEMENT THEREOF, CONTROL MEANS BEING MOUNTED WITHIN SAID HOUSING AND IN SURROUNDING RELATION TO SAID ADJUSTING MEANS, SAID CONTROL MEANS COOPERATING WITH SAID ADJUSTING MEANS FOR CAUSING LONGITUDINAL MOVEMENT THEREOF, SAID ADJUSTING MEANS COMPRISING A COLLAR AND SAID CONTROL MEANS BEING THREADABLY

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