US3824512A

US3824512A - Magnetic self-latching pressure switch

Info

Publication number: US3824512A
Application number: US00415912A
Authority: US
Inventors: F Glass
Original assignee: US Atomic Energy Commission (AEC)
Current assignee: US Atomic Energy Commission (AEC)
Priority date: 1973-11-14
Filing date: 1973-11-14
Publication date: 1974-07-16
Anticipated expiration: 1991-07-16

Abstract

A pressure-operated switch is provided that will maintain closure indefinitely until it is reset electrically. A permanent magnet is positioned close to a reed relay switch in response to a shock wave and the magnet acting in conjunction with two pole pieces effects the closing of the switch which then remains closed even when the shock wave no longer exists. The switch may then be reset to an open position by means of an electrical coil encompassing the reed switch.

Description

United States Patent [191 Glass [111 3,824,512 [451 July 16, 1974 MAGNETIC SELF-LATCHING PRESSURE SWITCH Inventor: Floyd M. Glass, Oak Ridge, Tenn.

The United States of America as represented by the United States Atomic Energy Commission, Washington, DC.

Filed: Nov. 14, 1973 App]. No.: 415,912

Assignee:

US. Cl. 335/205, 200/83 L, 335/153 Int. Cl. .Q H0lh 35/32 Field of Search 335/ 153, 205-207;

References Cited UNITED STATES PATENTS Mathisen 200/83 L 3,349,203 l0/l967 Wolford ..335/205X Primary Examiner-R. N. Envall Attorney, Agent, or Firm-John A. Horan; David S. Zachry; Louis M. Deckelmann [5 7] ABSTRACT A pressure-operated switch is provided that will maintain closure indefinitely until it is reset electrically. A permanent magnet is positioned close to a reed relay switch in response to a shock wave and the magnet acting in conjunction with two pole pieces effects the closing of the switch which then remains closed even when the shock wave no longer exists. The switch may then be reset to an open position by means of an electrical coil encompassing the reed switch.

3 Claims, 2 Drawing Figures 1 MAGNETIC SELF-LATCHING PRESSURE SWITCH BACKGROUND OF THE INVENTION This invention was made in the course of, or under, a contract with the United States Atomic Energy Commission, and a contract with the Defense Civil Preparedness Agency.

An engineering feasibility study on automated attack-effects information systems was recently prepared at the Oak Ridge National Laboratory for the Defense Civil Preparedness Agency. In this study, a pressure switch responsive to an overpressure condution due to a shock wave was desired that would respond positively (switch closed) when interrogated, regardless of whether or not the overpressure was still present, and that could be remotely resettable to a switch open position after being interrogated.

It is not common in the prior art to utilize a reed relay that is actuated to a switch closing position by a shock wave, and remains closed after the shock wave passes. Thus, there exists a need for a pressure-operated switch that when closed in response to an overpressure will remain closed even when the pressure condition no longer exists, and that can be remotely reset. The present invention was conceived to meet this need in a manner to be described hereinbelow.

SUMMARY OF THE INVENTION It is the object of the present invention to provide a magnetic self-latching pressure switch that will maintain closure indefinitely until it is reset electrically.

The above object has been accomplished in the present invention by providing a reed relay switch enclosed within a housing provided with a base, a nonmagnetic bellows attached to the base and forming the side walls of the housing, and a nonmagnetic diaphragm cover affixed to the top of the bellows. A small permanent magnet is attached to the inner side of the diaphragm cover, and two low retentivity pole pieces are attached to opposite wire leads from the reed relay switch and are located a small distance from the magnet. When the magnet is moved closer to the pole pieces in response to an overpressure force on the diaphragm cover, the resulting magnetic forces inducedin the pole pieces effect a closing of the reed switch. Once closed, there is sufficient magnetic flux in the pole pieces to maintain closure of the switch even after the passing of the overpressure force and the return of the magnet to its former position. When it is desired to reset the switch, this may be accomplished by means of a simple electrical coil encompassing the reed switch which coil may be energized from a remote location if such is desired.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a top view, partially cut away, of the pressure switch of the present invention.

FIG. 2 is a partial cross-sectional side view of the switch of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT 2. The reed switch 19 is not shown in FIG. 2 for the sake of clarity. The switching contacts of the reed switch 19 are connected to

respective leads

17 and 18. A small permenent magnet 23 is attached to the inner side of the diaphragm cover 15 and two low retentivity (soft iron) L-

shaped pole pieces

21 and 22 are attached, respectively, to the wire leads l7 and I8 and are locateda small (calibrated) distance from the magnet 23 in the manner shown. The

pole pieces

21 and 22 are supported, respectively, by

posts

26 and 26 mounted on the base 24.

In the operation of the above device, when it is subjected to an overpressure force (e.g., a shock wave from an explosion), the diaphragm 15 moves inward toward the

pole piece

21, 22 as the bellows 16 absorbs the force of the shock wave. The magnetic forces induced in the pole pieces by the approaching magnet 23 have sufficient magnetic coupling through the

leads

17 and 18 to close the reeds of the relay switch 19. When the switch closes, one (C) of the three air gaps (A, B, C) in the magnetic circuit is removed. This leaves sufficient magnetic flux to maintain closure of'the reeds after the passing of the shock wave and the return of the magnet 23 to its former position.

Thus, when one or more of the pressure responsive switches of the present invention are located at each of a plurality of separated sensor stations, then each of the switches can be interrogated by external circuitry, not shown, in a sequential manner to determine which one or ones of these switches has or have been closed in response to a shock wave.

The reed relay switch 19 of FIG. 1 is provided with an electrical coil 20 encompassing the switch as shown in the drawing. This coil is adapted to be connected by means of suitable leads to an external power supply by means of a remote control switch, all not shown. Thus,

' after the pressure switch 19 has been interrogated and has been found to be closed as a result of an overpressure or shock wave, then it may be reset to an open condition by means of the coil 20 when it is energized by momentarily closing the power supply circuit thereto.

Since the sensor, described above, must adjust to changes in atmospheric pressure, a short length of capillary tubing 25 extends through the base 24 of the sensor, as more clearly shown in FIG. 2, such that this will allow breathing" without interfering with the operation of the sensor.

It should be noted that the normal spacing between the magnet 23 and the

pole pieces

21 and 22 can be set at a desired calibrated value such that a desired overpressure will actuate the switch. For example, when two pressure sensitive switches are required at each sensing station, then one may be constructed to close at an overpressure of 0.5 psi and the other constructed to close at an overpressure of 5 psi.

This invention has been described by way of illustration rather than by limitation and it should be apparent that it is equally applicable in fields other than those described. For example, it may be used for the sensing of pressure excursions in any kind of gas or liquid line.

What is claimed is:

l. A magnetic self-latching pressure switch comprising a base member; a non-magnetic bellows mounted on said base and provided with a non-magnetic diaphragm cover over the open end of said bellows; a reed switch mounted on said base member and within said bellows; said reed switch having first and second electrical leads connected to respective contacts thereof; a permanent magnet mounted on the inside of said cover to move toward said base responsive'to incidence on said cover of a pressure wave; and first and second L- shaped pole pieces mounted symmetrically on said base with respect to said magnet, each of said pole pieces being connected to a corresponding lead from said reed switch to induce an attractive polarity in said leads and on said switch contacts, thereby effecting a closing of said switch contacts upon movement of said magnet a calibrated distance toward said pole pieces in response to'said pressure wave, the distance between said pole pieces and said magnet being such that sufficient magnetic flux exists therebetween to maintain said contacts supply.

3. The pressure switch set forth inclaim 2, and further including a short length of capillary tubing extending through said base to provide for automatic adjustment to changes in atmospheric pressure.

Claims

1. A magnetic self-latching pressure switch comprising a base member; a non-magnetic bellows mounted on said base and provided with a non-magnetic diaphragm cover over the open end of said bellows; a reed switch mounted on said base member and within said bellows; said reed switch having first and second electrical leads connected to respective contacts thereof; a permanent magnet mounted on the inside of said cover to move toward said base responsive to incidence on said cover of a pressure wave; and first and second L-shaped pole pieces mounted symmetrically on said base with respect to said magnet, each of said pole pieces being connected to a correSponding lead from said reed switch to induce an attractive polarity in said leads and on said switch contacts, thereby effecting a closing of said switch contacts upon movement of said magnet a calibrated distance toward said pole pieces in response to said pressure wave, the distance between said pole pieces and said magnet being such that sufficient magnetic flux exists therebetween to maintain said contacts closed upon return of said magnet to its normal position.

2. The pressure switch set forth in claim 1, and further including an electrical coil encompassing said reed switch, said coil adapted to be selectively connected to a remote external power supply, whereby the contacts of said reed switch when closed may be reset to an open condition by an energization of said coil by said power supply.

3. The pressure switch set forth in claim 2, and further including a short length of capillary tubing extending through said base to provide for automatic adjustment to changes in atmospheric pressure.