US3077524A

US3077524A - Pressure switch

Info

Publication number: US3077524A
Application number: US48790A
Authority: US
Inventors: Charles M Blackburn
Original assignee: Individual
Current assignee: Individual
Priority date: 1960-08-10
Filing date: 1960-08-10
Publication date: 1963-02-12
Anticipated expiration: 1980-02-12

Description

Feb. 12, 1963 c. M. BLACKBURN PRESSURE SWITCH F iled Aug. 10. 1960 INVENTOR.

N R w K C A L B M w M H C ATTORNEYS 3,077,524 PRESSURE SWITCH Charles M. Blackburn, Silver Spring, Md., assignor to the United States of America as represented by the Secretary of the Navy Filed Aug. 10, 1960, Ser. No. 48,790 2 Claims. (Cl. 200-82) The present invention relates to pressure swiches and more particularly to such a switch that is operable in conjunction with a unique hydraulic actuator arrangement.

Well known in the art are pressure switches which will actuate when a predetermined fluid pressure is attained. Such switches may also be provided with a mechanical latch or detent to hold the switch open or closed after actuation, although oftentime the latch or detent is omitted whereby subsidence of the prmsure will allow the switch to return by the force of a spring to its original condition.

These prior art devices are directly responsive to the rate of change of the fluid pressure, and because of this, are not satisfactory for use in an environment where the fluid pressure is likely to fluctuate, particularly if it is desired that the switch remain open or closed during the period of pressure fluctuation, and yet be able to return to the original condition upon subsidence of the pressure below a certain value.

It is therefore the object of the present invention to provide a fluid pressure actuated switch which will actuate at a predetermined value of pressure, remain in the actuated position even after subsidence of the pressure below the predetermined value, and be able to return to the original position after the pressure has subsided to a second predetermined value. Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawing.

Briefly the present invention contemplates a stepped piston including a pair of unequal area piston faces and enclosed within a cylinder having a pair of corresponding bores. The piston faces are disposed such that the one of smaller area is subjected to the fluid pressure before the other. As the pressure increases to a predetermined amount the piston is urged against the force of a spring into an actuating position wherein a rod attached to the piston engages a pair of electrical contacts in switch closing fashion. While the piston is in this position, a bypass port is opened to allow access of the fluid pressure to the second and larger piston face thus allowing a lesser value of pressure to maintain the piston in the actuating position. The rod then is held in a switch closing position even though the fluid pressure fluctuates considerably. As the pressure decreases to a second predetermined value where it becomes insufficient by acting on the larger piston area to counteract the force of the spring, the piston is returned to its original position.

The single drawing is a simplified schematic diagram of an application of the present invention, the switch being shown in enlarged cross section.

The particular application depicted relates to missiles and specifically to the arming of a warhead of such a missile, although it will become obvious that the present invention may be employed in other ways.

Referring to the drawing in detail, a switch 2 is shown included in an arming circuit 4 and a self-datruct circuit 6 of a missile 8. The switch comprises a cylinder '10 and a contact housing 12, the former being adapted to receive fluid pressure from a pump 14 that is coupled to a hydraulic system 16 of the missile and driven by a ram air turbine 17. Threadably secured to the housing 12 and closing the end thereof is a cap 18. The cylinder in- 3,077,524 Patented Feb. 12, 1963 ice eludes cylinder elements 19 and 20 which are coupled in threaded engagement, a seal being provided therebetween.

Fluid pressure developed by the pump 14 is delivered through a line 26 to a first chamber 28 of relatively small bore within the cylinder 10. At the opposite end of the chamber 28 is formed a concentric second chamber 29 of larger bore which communicates with the first chamber. A bypass port 30 is provided in the cylinder 10 and serves to permit fluid to be delivered to the second chamber 29 from the first chamber 28.

A stepped piston 31 is disposed within the cylinder 10 and is formed with a piston face 32 that coacts with the chamber 28, and a second face 34 which coacts with the second chamber 29. Projecting concentrically from the piston 31 is a rod 36 which extends through an apertured wall 38 of the cylinder 10 into the contact housing 12. A spring 40 is positioned on the rod 36 and is interposed between the wall 38 and the piston 31, the action of the spring tending to maintain the piston to the right in a non-depressed position. While the piston 31 is in this non-depressed position, the bypass port 30 is blocked thereby, the port being unblocked when the piston moves to the left under influence of fluid pressure into a depressed position.

Provided on the piston 31 to minimize fluid leakage are

seals

42 and 44, another seal 46 being recessed in the wall 38 for contact with the rod 36.

The contact housing 12 is threadably secured to the wall 38 of the cylinder 10 and encloses the projecting end of the rod 36. Supported within the housing 12 are pairs of contacts 50 and 52 that are engageable with the rod 36. As can be seen from the drawing, when the piston 31 is in the non-depressed position, the rod 36 engages the contacts 52 to close a portion of the self-destruct circuit 6, it being recognized that actual self-destruction of the missile will not occur until certain other conditions have been met. In the depressed position, the piston 31 urges the rod 36 into engagement with the contacts 50 to close the arming circuit 4. Positioned on the rod 36 is an insulating sleeve 54 which is located in such manner that when the rod is in engagement with the contacts 50, the connection across the contacts 52 is disrupted by the interposition of the insulating sleeve.

In operation when the fluid pressure being delivered to the line 26 is zero or very nearly so, the force of the spring 40 is of sufficient magnitude to constrain the piston 31 in the non-depressed position so that only the selfdestruct contacts 52 are in engagement with the rod 36. This condition corresponds to a pre-boost or pre-launch condition of the missile where the arming circuit 4 should be kept open. While in this non-depressed position, the piston 31 blocks the bypass port 30 so that the fluid pressure is exerted only on the piston face 32.

After the missile is launched, the ram air driven turbine 17 causes the pump 14 to build up hydraulic pressure in the line 26 and on the piston face 32. As the speed of the missile is increased, the hydraulic pressure increases until a value thereof is attained which is sufficient, while acting on the small area of the piston face 32, to move the piston 31 against the force of the spring 40 until the depressed position is attained where the seal 44 is seated against the wall 38. In this position, the rod 36 engages the contacts 50 to complete the arming circuit 4, the contacts 52, however, being interrupted by the insulating sleeve so that the self-destruct circuit is kept open. Also, when the piston 31 is in this depressed position, the bypass port is unblocked so that the fluid pressure now exerts force additionally on the piston face 34. This then permits a much lower value of the fluid pressure to maintain the piston 31 in the depressed position, since a considerably greater piston area is acted on thereby.

3 Thus, if for any reason, as for example in high altitude maneuvering, the hydraulic pressure from the pump 14 should fluctuate, the arming circuit 4 will remain a closed, insofar as the switch 2 is concerned.

If the hydraulic system should fail completely, then the lack of fluid pressure in the chambers 28 and 29 will allow the spring 40 to return the piston 31 to the non-depressed position where the contacts 52 are again closed to permit self-destruction of the missile.

It will be noted from the drawing that a definable gap is provided between the peripheral wall of the piston face 34 and the inner wall of the chamber 29. It is also to be noted that the seal 44 is not a peripheral seal but a face seal positioned for seating against the end Wall 38. The purpose of this arrangement is to allow any fluid which may leak by the seal 42, when the switch 2 is in the pre-boost or non-depressed position, to find a path around the piston face 34 and eventually flow out of the chamber 29 through a drain 60 in the end wall 38. Otherwise, such fluid leaking by the seal 28 might tend to accumulate in the chamber 29 ahead of the piston face 34 and cause premature actuation of the switch.

Similarly, in order to accommodate any fluid which might leak by the seal 46 and to otherwise vent the contact housing 12, an aperture 62 is formed in the wall thereof.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A pressure switch, comprising, a cylinder having a pair of adjacent, aligned chambers therein, one of said chamber-s being substantially smaller in bore than the other, means for supplying fluid pressure to the smaller of said chambers, a differential piston disposed within said chambers and responsive to said fluid pressure to be moved thereby from the smaller chamber toward the larger chamber to a depressed position, said piston including a relatively large portion disposed within the larger of said chambers and having a relatively large piston face thereon, and a relatively small portion disposed within the smaller of said chambers and having a relatively small piston face thereon exposed to said fluid pressure, each of said piston portions having a diameter slightly less than the diameter of the chamber in which it is disposed, and both of said piston faces being directed away from said depressed position, resilient means in said cylinder for producing a force on said piston counter to that produced by said fluid pressure and for maintaining said piston in a non-depressed position in the absence of said fluid-pressure, two spaced pairs of contacts mounted on said cylinder, a movable switch element on said piston and successively engageable with said pairs of contacts in a switch closing position when said piston is moved toward a depressed position, and an insulating means on said movable element and engageable with one pair of said contacts for preventing concurrent closure of both pair of said contacts when said piston is in said depressed position, said cylinder having a bypass .port extending from the smaller chamber to the larger chamber for supplying fluid pressure to said latter chamber for acting on said relatively large piston face, the inlet end of said bypass port being positioned so that it is closed by the smaller portion of said piston when the piston is in said non-depressed position but is automatically opened when said piston moves to said depressed position.

2. A pressure switch as recited in claim 1, wherein a slight, unsealed clearance exists between said larger piston portion and the wall of said larger chamber, and including seal means between the smaller piston portion and the wall of the smaller bore and positioned to seal said bypass port from said'fluid pressure until said piston moves toward said depressed position.

References Cited in the file of this patent UNITED STATES PATENTS 747,772 Rick-man Dec. 22, 1903 1,952,667 Geraghty Mar. 27, 1934 2,596,171 Rabinow May.13, 1952 2,764,645 Smith Sept. 25, 1956 2,813,177 Eberhard et al Nov. 12, 1957 2,827,850 Muzzey Mar. 25, 1958 2,891,120 S'aholt June 16, 1959 2,982,093 Belcher et al. May 2,1961

Claims

1. A PRESSURE SWITCH, COMPRISING, A CYLINDER HAVING A PAIR OF ADJACENT, ALIGNED CHAMBERS THEREIN, ONE OF SAID CHAMBERS BEING SUBSTANTIALLY SMALLER IN BORE THAN THE OTHER, MEANS FOR SUPPLYING FLUID PRESSURE TO THE SMALLER OF SAID CHAMBERS, A DIFFERENTIAL PISTON DISPOSED WITHIN SAID CHAMBERS AND RESPONSIVE TO SAID FLUID PRESSURE TO BE MOVED THEREBY FROM THE SMALLER CHAMBER TOWARD THE LARGER CHAMBER TO A DEPRESSED POSITION, SAID PISTON INCLUDING A RELATIVELY LARGE PORTION DISPOSED WITHIN THE LARGER OF SAID CHAMBERS AND HAVING A RELATIVELY LARGE PISTON FACE THEREON, AND A RELATIVELY SMALL PORTION DISPOSED WITHIN THE SMALLER OF SAID CHAMBERS AND HAVING A RELATIVELY SMALL PISTON FACE THEREON EXPOSED TO SAID FLUID PRESSURE, EACH OF SAID PISTON PORTIONS HAVING A DIAMETER SLIGHTLY LESS THAN THE DIAMETER OF THE CHAMBER IN WHICH IT IS DISPOSED, AND BOTH OF SAID PISTON FACES BEING DIRECTED AWAY FROM SAID DEPRESSED POSITION, RESILIENT MEANS IN SAID CYLINDER FOR PRODUCING A FORCE ON SAID PISTON COUNTER TO THAT PRODUCED BY SAID FLUID PRESSURE AND FOR MAINTAINING SAID PISTON IN A NON-DEPRESSED POSITION IN THE ABSENCE OF SAID FLUID PRESSURE, TWO SPACED PAIRS OF CONTACTS MOUNTED ON SAID CYLINDER, A MOVABLE SWITCH ELEMENT ON SAID PISTON AND SUCCESSIVELY ENGAGEABLE WITH SAID PAIRS OF CONTACTS IN A SWITCH CLOSING POSITION WHEN SAID PISTON IS MOVED TOWARD A DEPRESSED POSITION, AND AN INSULATING MEANS ON SAID MOVABLE ELEMENT AND ENGAGEABLE WITH ONE PAIR OF SAID CONTACTS FOR PREVENTING CONCURRENT CLOSURE OF BOTH PAIR OF SAID CONTACTS WHEN SAID PISTON IS IN SAID DEPRESSED POSITION, SAID CYLINDER HAVING A BYPASS PORT EXTENDING FROM THE SMALLER CHAMBER TO THE LARGER CHAMBER FOR SUPPLYING FLUID PRESSURE TO SAID LATTER CHAMBER FOR ACTING ON SAID RELATIVELY LARGE PISTON FACE, THE INLET END OF SAID BYPASS PORT BEING POSITIONED SO THAT IT IS CLOSED BY THE SMALLER PORTION OF SAID PISTON WHEN THE PISTON IS IN SAID NON-DEPRESSED POSITION BUT IS AUTOMATICALLY OPENED WHEN SAID PISTON MOVES TO SAID DEPRESSED POSITION.