US3267232A

US3267232A - Pressure switch having positive action reset means and adjustable length connection to diaphragm

Info

Publication number: US3267232A
Application number: US379089A
Authority: US
Inventors: Howard R Chapin
Original assignee: Controls Company of America
Current assignee: Controls Company of America
Priority date: 1964-06-30
Filing date: 1964-06-30
Publication date: 1966-08-16
Anticipated expiration: 1983-08-16

Description

3,267,232 ANS AND Aug. 16, 1966 H. R. CHAPIN PRESSURE SWITCH HAVING POSITIVE ACTION RESET ME ADJUSTABLE LENGTH CONNECTION TO DIAPHRAGM Filed June 30. 1964 5 Sheets-Sheet HowARa Aug. 16, 1966 H. R. CHAPIN 3,267,232

PRESSURE SWITCH HAVING POSITIVE ACTION RESET MEANS AND ADJUSTABLE LENGTH CONNECTION TO DIAPHRAGM Filed June 30. 1964 5 Sheets-=Sheet 2 o HOWARD R. Cmmm ATTQRNeY Aug. 16,- 1966 H. R. CHAPIN 3,267,232

PRESSURE SWITCH HAVING POSITIVE ACTION RESET MEANS AND ADJUSTABLE LENGTH CONNECTION TO DIAPHRAGM Filed June 30. 1964 5 Sheets-Sheei: 5

' hwamoR Howmm KCHAHN 3,267,232 PRESSURE SWITCH HAVING POSITIVE ACTION RESET MEANS AND ADJUSTABLE LENGTH CONNECTION TO DIAPHRAGM Howard R. Chapin, Park Ridge, 11]., assignor to Controls Company. of America, Melrose Park, 111., a corporation of Delaware Filed June 30, 1964, Ser. No. 379,089 Claims. (Cl. 200-83) This invention relates to pressure responsive switch mechanisms of the type used, for example, to determine the water level in a washing machine and, more particularly, to a reset type pressure switch.

A general object of this invention is to improve the construction and operation of a reset pressure switch.

A more specific object of this invention is to provide a fixed reset level in a pressure switch construction which is not effected by variations in the trip level of the pres sure switch and, moreover, to provide for adjustment of the reset level as well as the trip level and to achieve adjustment of both independently of each other.

Another, more specific, object of this invention is to provide a pressure switch construction wherein optimum contact force is maintained at pressures closely approaching both the trip and reset pressures.

For the achievement of these and other objects, this invention contemplates a pressure switch construction having an operating spring assembly arranged to oppose diaphragm movement in response to an increase in pressure. The operating spring assembly includes a trip spring and a reset spring supported relative to each other, and to the diaphragm and switch mechanism of the pressure switch, such that only the reset spring opposes initial diaphragm movement from a low pressure condition toward a high pressure condition. After that initial movement, the reset spring is rendered inactive in opposing further diaphragm movement whereupon the trip spring becomes active to oppose diaphragm movement and it alone determines the high pressure trip level of the pressure switch. When going from a high to a low pressure condition, the reverse of the above operation occurs in that the reset spring is virtually inactive during initial movement and, after such initial movement, the trip spring is rendered inactive and the reset spring completes diaphragm movement to a low pressure position and it alone determines the low pressure reset level. Independent, adjustable seats are provided for the trip and reset springs to permit adjustment of each independently of the other.

In accordance with more specific aspects of this invention, it is preferred that the switch mechanism of the pressure switch be in the form of an over-center or toggletype switch having a lost motion connection with the diaphragm so as to elfect precise switching at the trip and reset pressures.

Other objects and advantages will be pointed out in, or be apparent from, the specification and claims, as will obvious modifications of the embodiment shown in the drawings, in which:

FIG. 1 is a section view illustrating a pressure switch constructed in accordance with this invention in its low pressure condition;

FIG. 2 is a similar section view illustrating the pressure switch after initial movement of the diaphragm from the low pressure condition toward a high pressure condition and at the point where the reset spring is rendered inactive leaving the trip spring alone to oppose further movement in response to increased pressure.

FIG. 3 is a similar section view illustrating the pressure switch in a high pressure condition and the switch United States Patent 0 "ic Patented 167,232

mechanism thereof switched over to the high pressure contact;

FIG. 4 is a bottom plan view of the pressure switch with the diaphragm removed to illustrate the switch mechanism; and

FIGS. 5 and 6 are front and side elevations, respective-ly, of the trip spring adjusting mechanism.

With particular reference to the drawings, the pressure switch includes housing 10 formed by a body 1-2, of suitable electrical insulating material, and a metallic cover 14 connected to the body by turned portions 16. Diaphragm assembly 18 is of well-known construction consisting of membrane 20 of suitable resilient material, such as rubber, and backed by metallic disk 22. The peripheral edge of resilient membrane 20 is clamped in annular groove 24 of the body by cover 14 and in this manner is connected so that it can flex about its peripheral edge in response to pressure variations.

The diaphragm assembly divides housing 10 into pressure chamber 26 and switch chamber 28. In a manner well known in the art, suitable means 27 is provided to connect pressure chamber 26 to a source of pressure so that the pressure in chamber 26 varies in accordance with the pressure of the source and diaphragm assembly 118 moves in accordance with pressure variations in ch-am I er 26.

Motion of the diaphragm assembly is transmitted through actuator assembly 29 to switch mechanism 30 and the actuator assembly is associated with operator spring assembly 32 which influences diaphragm movement and correspondingly switch actuation. The operator spring assembly exerts a biasing force in opposition to movement of the diaphragm in response to increase pressure and cooperates in moving the diaphragm assembly as the pressure on the diaphragm decreases.

More particularly, switch mechanism 30 is preferably an over-center switch comprising movable switch blade 34 anchored at one end on body 12 by pin 36 and extending from anchor 36 to support electrical contact 38 between stationary contacts which for convenience will be referred to as low pressure contact 40 and high pressure contact 42. The switch also includes over-center operating tongue 44 and coil spring 46 connected between the tongue and a point adjacent contact 38 on movable blade 34. This is a Well-known type of switch construction and is operative to move contact 38 between the high and low pressure contacts with a snap action in both directions of its movement.

The actuating assembly comprises member 48 suitably connected to backing disk 22 for movement with the diaphragm assembly, adjusting member 50 threadably engaged in member 48, and reset pin 52 disposed in a blind opening 54 in adjusting member 50. Member 48 has a lost motion connection with tongue 44, which will be described more completely hereinafter, and establishes a driving connection between the diaphragm assembly and the switch so that the switch and diaphragm move jointly to the low pressure position (FIG. 1) or the high pressure position (FIG. 3).

Operating spring assembly 32 preferably includes carrier 56 arranged exteriorly of the switch actuating chamber and positioned at an opening 58 in body 12 and aligned with

members

48 and 50 of the actuating assembly. One end 60 of the carrier is arranged in the opening to be disposed in the path of movement of

members

48 and 50 for engagement therewith. Pin 52 is disposed within carrier 56 and extends generally parallel to the direction of movement of the diaphragm assembly with one end thereof extending exteriorly of carrier end 60 into blind opening 54. Carrier 56 includes cylindrical portion 62 extending parallel to pin 52 and adjusting member 64 extending transwasher cooperating to provide a seat on the .pin for the opposite end of spring 68. The reset spring is a compression spring and-exerts a spring force in opposition to movement of the pin, and correspondingly the diaphragm assembly, in response to an increase in pressure in the pressure chamber 26.

Trip spring 74 also has one end seated on carrier 56. More particularly, carrier 56 includes laterally extending shelf 76 including groove 78 facing away from the diaphragm assembly and receiving one end of spring 74. The other end of spring 74 is seated within cap 80 associated with adjusting mechanism 82. Adjusting mechanism 82 takes the form of screw 83 supported on lever 85 fixed at one end to bracket 87 which is suitably connected on body 12. Operating plate 89 includes a serrated arcuate face 91 and is connected for movement with lever 93 which is in turn supported for pivotal movement on pin 95 connected to bracket 87. With this construction the position of cap 80 may be varied as desired to vary the high pressure trip level and manual reset can-be achieved by manipulating lever 93, as will be described more completely hereinafter. Spring 74 is also a compression spring and is compressed'by upward movement of diaphragm assembly 18 'under the influence of an increase in pressure on the diaphragm so that it too exerts a force in opposition to that movement. Spring 74 is stronger than spring 68 and normally biases carrier 56 toward engagement with body 12 and, when the pressure switch is in its low pressure condition of FIG. 1, spring 68 biases the reset pin toward the diaphragm assembly and holds

members

48 and 50 in spaced relation from end 60 of the carrier. Carrier 56 provides a common seat for

springs

68 and 74 and also provides the medium through which the force of spring 74 is transmitted to the diaphragm assembly.

In operation and assuming the pressure switch to be initially in the position of FIG. 1, an increase in pressure in chamber 26 causes diaphragm assembly 18 to flex upwardly. With

members

48 and 50 maintained in spaced 7 relationship from carrier end 60, pin 52 initially moves relative to carrier 56 which remains stationary for an initial portion of diaphragm movement and only reset spring 68 opposes diaphragm movement. movement the reset spring is compressed between shoulder 70 and surface 66 and,after a predetermined amount of such movement, shoulder 50a of member 50 engages end 60 of carrier 56. At this point the switch is still in its low pressure position with contact 38 in engagement with low pressure contact 40. Member 50 having engaged carrier 56, a driving connection is established between the diaphragm assembly and trip spring 74 so that further diaphragm movement is also opposed by the trip spring. No further deflection of spring 68 occurs although a component of the force of spring 68 is acting against diaphragm movement. The diaphragm works against the spring rate of only trip spring 74 during further movement in response to an increase in pressure. In other words, 'both the spring rate and spring force of spring 74 are effective whereas spring 68 and the carrier move as a unit from this point on and without spring 68 being'compressed further. More particularly, continued upward movement of diaphragm assembly 18 from the point illustrated in FIG. 2 acts against spring 74 alone and will eventually operate switch 30 toswit-ch contact 38 from low pressure contact 40 to high pressure contact 42, i.e. to assurne the high pressure position illustrated in FIG. 3. Accordingly, spring 74 determines the pressure in chamber 26 During initial versely of pin 52, and correspondingly transversely of the 4. necessary to trip the pressure switch to its high pressure position.

Should a decrease in pressure occur in chamber 26 the pressure switch will automatically reset itself. When in the high pressure position of FIG. 3, the trip spring exerts a.

and continued decrease in pressure, the sequence of operation is as follows: the carrier, and correspondingly, the actuator assembly and the diaphragm assembly, moves downward until shelf 76 engages body 12 to limit movement of carrier 56 toward the diaphragm assembly; at this point trip spring 74 is rendered operationally ineffective and its force is spent against body 12; after engagement of the carrier with the body only reset spring 68 exerts a downward force on diaphragm assembly 18 so that the reset spring determines the pressure at which switch mechanism 38 operates to switch contact 38 from high pressure contact 42 to low pressure contact 40.

Accordingly, the trip spring establishes the high pres sure trip level and reset spring 68 establishes the reset or low pressure level. The trip and reset springs are adjustable to vary the force each eXerts in oppposition to diaphragm movement and, correspondingly, to vary the highand low pressures at which switch actuation occurs, these adjustments being independent of each other so that one can be varied without effecting a desired setting of the other. It will also be noted that upper end 53 ofpin 52 extends exteriorly of adjusting member 64 and toward cap 80'for engagement with the cap to permit manual reset if desired, or to clear faulty switch operation, by manipulating lever to move cap 88 toward the diaphragm assembly.

To insure precise switching at the desired trip and reset levels a lostmotion connection is provided between the actuator assembly and the switch mechanism. Preferably, member 48 includes a peripheral groove 90 which a opens in a direction transverse to the direction of move.-

ment of the diaphragm assembly and receives tongue 44. The Width of groove 90, that is the dimension parallel to diaphragm movement is greater than the thickness of the tongue so that the tongue is free to move in the groove. relative to the actuator assembly as well aswith it. With this arrangement, tongue movement is initiated immediately upon movement of the diaphragm assembly from either its high or low pressure positions and at the desired high or low pressure trip levels the tongue and spring 46 snap the switch blade over so that switching occurs due to snap action imparted by the tongue and spring and not solely by further diaphragm movement there-by achieving precise control at the desired trip and reset level.

The threaded connection between

members

48 and 50 is preferred as it permits further adjustment in the actuating point for the switch. More particularly, by varying the extension of member 50 with respect to member 48 the distance between groove 90 and shelf 76, when shoulder 50a engages carrier end 60, can be pre-set as desired. Since the engagement between shelf 76 and body 12 provides a limit stop between the trip and reset springs, this connection between

members

48 and 50 permits precise adjustment of the trip and reset levels of the pressure switch and insures an accurate relationship between the groove and the limit stop for reliable operation. A slot 50b is provided in the end of member 50 to facilitate this adjustment.

It will be noted that the carrier, reset spring and reset pin form an integral subassembly which is assembled into the pressure switch as a unit by merely engaging the pin in member 50 and positioning the trip spring and cap. This reduces the number of parts which must be handled during final assembly thereby simplifying assembly procedures. Moreover, it will be noted that from the spirit of the invention or from the scope of the appended claims.

What I'claim is: I 1. A pressure responsive switch mechanism comprising, in combination,

a housing,

a diaphragm separating saidhousing into a pressure chamber and a switch chamber,

switch means disposed in said switch chamber and having high and low pressure operating positions,

means for connecting said pressure. chamber to a source of pressure so that said diaphragm moves in response to Variations in pressure in said pressure chamber,

an actuator assembly connecting said switch means to said diaphragm and transmitting diaphragm movement to said switch means to move said switch means between. said high and low pressure operating positions,

a hollow, elongated carrier disposed with its longitudinal axis parallel to the direction of movement of said diaphragm and having one of its longitudinal ends positioned in the path of movement of said actuator assembly for engagement thereby, said carrier also including an adjustable seat portion extending transversely of said longitudinal axis and means connecting said adjustable seat portion in said carrier for movement along said longitudinal axis to a'predetermined fixed position in said carrier,

an elongated pin member arranged in said carrier along the longitudinal axis thereof and supported for axial movement with respect to said carrier and extending through said one longitudinal end of said carrier for engagement with said actuator assembly,

said actuator assembly including a first member fixed to said diaphragm and having a threaded opening therein and a second member threadedly engaged in the threaded opening of said first member and including a seat opening toward said carrier and having said pin member disposed therein,

a reset spring within said carrier having one end seated on said adjustable seat portion and extending therefrom toward said diaphragm with its opposite end seated on said pin member to bias said pin member into engagement with said actuator assembly and to oppose movement of said actuator assembly in response to an increase inpreSsul'e in said pressure chamber,

a cap member,

means supporting said cap member for adjustable movement relative to said diaphragm to assume a predetermined fixed position relative :to said diaphragm,

and a trip spring seated at one end on said carrier and at its opposite end on said cap member, said trip spring opposing movement of said carrier in response to an increase in pressure in said pressure chamber,

said carrier positioned to engage said housing to limit movement of said carrier in a direction toward said diaphragm and movable out of engagement with said housing in response to an increase in pressure in said pressure chamber and said actuator assembly being normally spaced from said carrier whensaid diaphragm is in a low pressure position so that said carrier remains stationary during initial movement of said diaphragm from said low pres sure position in response to a pressure increase and only said reset spring opposes said initial diaphragm movement, said actuator assembly engaging said carrier after said initial movement to move said carrier and said reset spring as a unit against the force of said trip spring so that only said trip spring opposes movement of said diaphragm after said initial movement.

2. The pressure responsive switch mechanism of claim 1 wherein said elongated pin member extends through said carrier and is freely movable relative to said carrier when said actuator assembly is moving relative to said carrier, said elongated pin member extending exteriorly from said carrier toward said cap member when said actuator assembly is in engagement with said one end of said carrier,

and means supported on said housing and engageable with said cap member and operative to selectively move said cap member toward said pin member to move said pin member, actuator assembly and said diaphragm against the pressure in said pressure chamber to provide for selective reset of said switch means independent of the pressure in said pressure chamber.

3. The pressure responsive switch mechanism of claim 1 wherein said carrier includes a generally tubular body,

means defining a first restricted opening in said one end of said carrier, and said adjustable seat portion includes means defining a second restricted opening in the opposite longitudinal end of said carrier,

wherein said elongated pin member is disposed in and movable with respect to said first and second carrier end openings, said pin member including a generally radial projection within said carrier and positioned to engage said means defining said first restricted opening to .limit movement of said pin member,

and wherein said reset spring is seated between said adjustable seat and said radial projection,

4. A pressure switch comprising, in combination,

a diaphragm movable in accordance with pressure variations, switch means having high and low pressure operating positions,

, trip spring means and reset spring means,

a common spring seat member for said trip and reset spring means and having first and second oppositely facing surfaces, said first surface directed toward said diaphragm and said second surface directed away from said diaphragm,

means for moving said first surface in a direction parallel to the direction of diaphragm movement,

actuating means connecting said diaphragm to said switch means to transmit diaphragm movement to said switch means and positioned for movement into and out of engagement with said common spring seat member,

second spring seat means spaced from said common spring seat member in a direction away from said diaphragm and adjustable relative to said diaphragm,

said trip spring means engaged between said second surface of said common spring seat member and said second spring seat means so that said trip spring means biases said common spring seat member toward said diaphragm,

stop means limiting movement of said common spring seat member toward said diaphragm,

said actuating means including a first portion engageable with said common spring seat member, a second portion engageable with said switch means to provide a driving connection therewith and spaced from said first portion in a direction parallel to the direction of diaphragm movement, and means connected between said first and second portions for providing relative adjustable movement between said first and second portions in a direction parallel .to the direction of diaphragm movement to vary the distance between said second portion and said stop means when said first portion is in engagement with said common spring seat member,

and said reset springmeans seated between said first surface of said common spring seat member and said actuating means to bias said actuating means toward said diaphragm and to hold said actuating means away from said common spring seat member in a low pressure condition so that, during initial movement of said diaphragm from a position corresponding to said low pressure condition, said'common spring seat member remains stationary and c said reset spring alone opposes said initial diaph-nagm movement and said actuating means moves into driving engagement with said common spring seat member after said initial movement to establish a driving connection therebetween to render said reset spring inactive in opposing diaphragm movement with only said trip spring opposing further diaphragm movement due to pressure increase.

5. A pressure switch comprising, in combination,

a diaphragm movable in accordance with pressure variations,

switch means having low and high pressure operating positions,

trip spring means and reset spring means,

a common spring seat member for said spring means having first and second oppositely facing surfaces, said first surface directed toward said diaphragm and a said second surface directed away from said diaactuating means connecting said diaphragm to said switch means to transmit diaphragm movement to said switch means and positioned for movement into and out of engagement with said common spring seat member,

said reset spring means seated between said first surface of said common spring seat member and said actuating means to bias said actuating means toward said diaphragm and holding said actuating means away from said common spring seat member in a low pressure condition, said common spring seat member remaining stationary during initial movement of said diaphragm from a position corresponding to said low pressure condition with said reset spring means alone opposing said initial diaphragm movement and said actuating means moving into driving engagement with said common spring seat member after said initial movement to establish a direct driving connection therebetween to render said reset spring means inactive in opposing diaphragm movement'so that only said trip spring means opposes further diaphragm movement due to increased pressure,

and said actuating means including a first portion engageable with said common spring seat member to establish said direct driving connection and a second portion engageable with said switch means, and means connected between said first and second portions for providing relative adjustable movement therebetween in a direction parallel to the direction of diaphragm movement to vary the distance between said second portion and said stop means when said first portion is in engagement with said common spring seat member.

i 6. The pressure switch of claim 5 including an elon-Z gated rigid pin member,

means in said first actuating means portion defining a seat opening toward said common spring seat mem ber and said pin member being disposed in said seat,

means defining an opening in said common spring seat member,

said pin member extending through said opening in said common spring seat member and movable in said opening in response to movement of said actuating means toward said common spring seat member, said rigid'pin member extending axially exteriorly of said common spring seat member when said actuating means is in engagement with said common spring a housing,

over-center switch means in said housing including a movable switch blade and an over-center, member and having a trip position and a reset position,

a pressure responsive diaphragm,

actuating means connecting said diaphragm to said switch means and transmitting diaphragm movement in response to variations in pressure to said switch means,

spring means connected to said actuating means and opposing switch means movement in response to an increase in pressure on said diaphragm,

said actuating means including a first portion connected to said diaphragm and to the over-center member of said switch means, a second portion connected to said spring means and means connected between said first and second portions for providing relative adjustable movement between said first and second portions in a direction parallel to the direction of diaphragm movement to adjust the trip and reset positions of said switch means. a

8. A pressure switch comprising, in combination,

a housing,

switch means in said housing having a trip position and a reset position,

a pressure responsive diaphragm,

spring means connected to said actuating means and opposing actuating means movement in response to an increase in pressure on said diaphragm,

an elongated, rigid pin member engaging said actuating means and extending therefrom in a direction parallel to the direction of movement of said dia phragm,

said spring means engaging and biasing said pin member toward said actuating means,

and means supported from said housing for engagement with said pin member at a point remote from said diaphragm and selectively operable to exert an axial force through said pin member to said diaphragm to reset said switch means without regard to the pressure on said diaphragm.

9. A pressure switch comprising, in combination,

a diaphragm movable in accordance with pressure variations, i

switch means having high and low pressure operating positions,

trip spring means and reset spring means,

a carrier including an elongated tubular body portion having an axis extending parallel to the direction of movement of said diaphragm and first and second means spaced axially in said body and extending radially inwardly of said body and defining an opening in the radial extending means nearest said diap actuating means connecting said diaphragm to said switch means to transmit diaphragm movement to said switch means and positioned for movement into and out of engagement with said carrier,

trip spring seat means spaced from said carrier in a direction away from said diaphragm,

said trip spring means engaging said carrier and extending from said carrier in a direction away from said diaphragm and engaging said tri-p spring seat means so that said trip spring means is seated between said earrier and said trip spring seat means,

stop means for limiting movement of said carrier toward said diaphragm,

reset spring means disposed within said carrier and engaging the radial extending means of said carrier which is axially remote from said diaphragm,

and reset spring seat means disposed in said carrier and extending axially through the opening in said nearest radial extending means and engaging said actuating means,

said reset spring seat means including a radial projection within said carrier and larger than said opening and engageable with said nearest radial extending means to limit movement of said reset spring seat means, said reset spring means engaging said radial projection so that said reset spring means is seated between said remote radial extending means and said radial surface on said reset spring seat means, said reset spring means biasing said actuating means toward said diaphragm and holding said actuating means away from said carrier in a low pressure condition so that said carrier remains stationary during initial movement of said diaphragm from a position corresponding to said low pressure condition with said reset spring means alone opposing said initial diaphragm movement and said actuating means moving into driving engagement with said carrier after said initial movement to establish a direct driving connection therebetween to render said reset spring means inactive in opposing diaphragm movement with only said trip spring means opposing further diaphragm movement due to increased pressure.

10. The pressure switch of claim 9 including means connecting said remote radial extending means for axial 20 movement relative to said elongated body to adjust the force of said reset spring means.

References Cited by the Examiner BERNARD A. GILHEANY, Primary Examiner.

H. M. FLECK, Assistant Examiner.

Claims

1. A PRESSURE RESPONSIVE SWITCH MECHANISM COMPRISING, IN COMBINATION, A HOUSING, A DIAPHRAGM SEPARATING SAID HOUSING INTO A PRESSURE CHAMBER AND A SWITCH CHAMBER, SWITCH MEANS DISPOSED IN SAID SWITCH CHAMBER AND HAVING HIGH AND LOW PRESSURE OPERATING POSITIONS, MEANS FOR CONNECTING SAID PRESSURE CHAMBER TO A SOURCE OF PRESSURE SO THAT SAID DIAPHRAGM MOVES IN RESPONSE TO VARIATIONS IN PRESSURE IN SAID PRESSURE CHAMBER, AN ACTUATOR ASSEMBLY CONNECTING SAID SWITCH MEANS TO SAID DIAPHRAGM AND TRANSMITTING DIAPHRAGM MOVEMENT TO SAID SWITCH MEANS TO MOVE SAID SWITCH MEANS BETWEEN SAID HIGH AND LOW PRESSURE OPERATING POSITIONS, A HOLLOW, ELONGATED CARRIER DISPOSED WITH ITS LONGITUDINAL AXIS PARALLEL TO THE DIRECTION OF MOVEMENT OF SAID DIAPHRAGM AND HAVING ONE OF ITS LONGITUDINAL ENDS POSITIONED IN THE PATH OF MOVEMENT OF SAID ACTUATOR ASSEMBLY FOR ENGAGEMENT THEREBY, SAID CARRIER ALSO INCLUDING AN ADJUSTABLE SEAT PORTION EXTENDING TRANSVERSELY OF SAID LONGITUDINAL AXIS AND MEANS CONNECTING SAID ADJUSTABLE SEAT PORTION IN SAID CARRIER FOR MOVEMENT ALONG SAID LONGITUDINAL AXIS TO A PREDETERMINED FIXED POSITION IN SAID CARRIER, AN ELONGATED PIN MEMBER ARRANGED IN SAID CARRIER ALONG THE LONGITUDINAL AXIS THEREOF AND SUPPORTED FOR AXIAL MOVEMENT WITH RESPECT TO SAID CARRIER AND EXTENDING THROUGH SAID ONE LONGITUDINAL END OF SAID CARRIER FOR ENGAGEMENT WITH SAID ACTUATOR ASSEMBLY, SAID ACTUATOR ASSEMBLY INCLUDING A FIRST MEMBER FIXED TO SAID DIAPHRAGM AND HAVING A THREADED OPENING THEREIN AND A SECOND MEMBER THREADEDLY ENGAGED IN THE THREADED OPENING OF SAID FIRST MEMBER AND IN CLUDING A SEAT OPENING TOWARD SAID CARRIER AND HAVING SAID PIN MEMBER DISPOSED THEREIN, A RESET SPRING WITHIN SAID CARRIER HAVING ONE END SEATED ON SAID ADJUSTABLE SEAT PORTION AND EXTENDING THEREFROM TOWARD SAID DIAPHRAGM WITH ITS OPPOSITE END SEATED ON SAID PIN MEMBER TO BIAS SAID PIN MEMBER INTO ENGAGEMENT WITH SAID ACTUATOR ASSEMBLY AND TO OPPOSE MOVEMENT OF SAID ACTUATOR ASSEMBLY IN RESPONSE TO AN INCREASE IN PRESSURE IN SAID PRESSURE CHAMBER,