Abstract:
A magnetic latching switch includes a housing having mounted therein a movable electrical control structure normally retained in a first position with a stationary electrical lug structure. The electrical control structure and the electrical lugs are held together by a retaining system including a magnetic arrangement contacted by a biasing arrangement for providing a magnetic biasing force. A diaphragm assembly is movable into direct contact with the magnetic arrangement in response to a predetermined counteracting force exerting an operating force which overcomes the magnetic biasing force, and enables the biasing system to move the contact structure to a second position with the stationary lugs.

Description:
FIELD OF THE INVENTION 
   The present invention relates generally to a magnetic latching switch and, more particularly, pertains to a switch device which is operable to change switching positions in response to a predetermined counteracting force. 
   BACKGROUND OF THE INVENTION 
   In certain applications, it is highly desirable to utilize a switch which will effectively alter an operating condition in response to a reaction caused by a pressure change. In one particular application related to the manufacture of hybrid vehicles, power is obtained from battery packs typically comprised of multiple cells in series with a switch within in a common manifold. If a fault occurs in any of the cells, it is critical to discontinue charging in the faulted battery pack so as to avoid an explosion. Each battery is equipped with a disk which ruptures in the presence of a fault and emits pressurized gas. 
   It is desirable that any pressurized gas is communicated to a pressure switch which will quickly break a normally closed electrical connection with a device connected thereto upon reaching a predetermined critical pressure level. The pressure switch should act as a safety device with an arrangement which will normally maintain electrical engagement between sets of contacts, but will function to immediately snap apart the contacts in the presence of built-up gas pressure. The switch is intended to be manually reset only upon rectifying the fault condition. 
   SUMMARY OF THE INVENTION 
   It is a general object of the present invention to provide a responsive switching device which is particularly fast-acting in breaking an electrical connection. 
   It is also an object of the present invention to provide a safety switch which can be utilized to detect fault in a battery. 
   It is a further object of the present invention to provide a switch having contacts held in one position and snapped to another position upon the presence of a predetermined counteracting force. 
   In one aspect of the present invention, a magnetic latching switch includes a housing having mounted therein a movable electrical contact structure normally retained in a first position with a stationary electrical lug structure by a biasing system including a magnetic arrangement contacted by the biasing arrangement for providing a magnetic biasing force. A diaphragm assembly is movable into direct contact with the magnetic arrangement in response to a predetermined counteracting force exerting an operating force overcoming the magnetic bearing force and enabling the biasing system to move the contact structure to a second position with the stationary lugs. 
   The magnetic arrangement includes a fixed magnet, a fixed core and a movable armature engagable and disengagable with the core. The contact structure includes a movable blade having a set of contacts at opposite ends thereof. The biasing system includes a first spring engaged against the movable blade and a second spring engaged against the armature. A fixed retainer surrounds the core and the fixed magnet, and the second spring surrounds the retainer. A flux washer is disposed beneath the fixed magnet and the retainer. The diaphragm assembly includes a flexible diaphragm attached to a piston having an upstanding piston pin passing through the flux washer and the fixed magnet. The piston pin is engagable with the armature upon application of the operating force. The housing includes an inlet nozzle having a fluid passageway in communication with one side of the diaphragm. The second spring exerts a second biasing force which is greater than a first biasing force exerted by the first spring. The switch is manually reset by means of a reset pin slidable into and out of the housing and engagable with the armature. The first spring lies in surrounding spaced relationship relative to the reset pin. In the first position, the armature is spaced from the movable blade. Upon application of the operating force, an air gap is created between the armature and the core dissipating the magnetic biasing force and allowing the second biasing force to push the movable blade against the first biasing force and cause movement of the contacts relative to the lug structure. The housing is formed with a cavity for holding the stationary lug structure and the contact structure. The housing includes an end cap having mounting structure adapted to attach the switch to a support. 
   In another aspect of the invention, a magnetic latching switch includes a housing having a movable electrical contact structure held in a first position with stationary electrical lugs by a first biasing device exerting a first biasing force. A magnetic holding arrangement is provided for normally enabling the contact structure and the stationary lugs to maintain the normally closed, latched position and creating a magnetic force between a fixed magnet and a movable magnet. The magnetic force normally overcomes a second biasing force provided by a second biasing device acting against the movable magnet. A reciprocable piston assembly is attached to a diaphragm movable in response to a predetermined counteracting force acting on one side of the diaphragm and exerting an operating force greater than the magnetic force. A portion of the piston assembly is engagable with the movable magnet upon application of the operating force such that the movable magnet urged by the second biasing device will move the contact structure into a second position with the stationary lugs. A reset pin is movable into and out of the housing and is in constant engagement with the movable magnet. The housing is formed with a chamber for holding the diaphragm assembly. The housing is also formed with a pocket for holding the fixed magnet, a core, a retainer, a flux washer and the second biasing device. The housing is further formed with a cavity for holding the stationary lug structure and the contact structure. 
   Various other objects features and advantages of the invention will be made apparent from the following description taken together with the drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The drawings illustrate the best mode presently contemplated of carrying out the invention. 
     In the drawings: 
       FIG. 1  is a perspective view of a magnetic latching switch embodying the present invention; 
       FIG. 2  is a sectional view taken on line  2 — 2  of  FIG. 1  showing the switch in a closed or latched position; 
       FIG. 3  is a view like  FIG. 2  showing the admission of a counteracting force to the inlet of the switch and the initial movement of the internal components in an open or unlatched position; and 
       FIG. 4  is another view similar to  FIG. 3  showing further movement of the internal components in the open or unlatched position. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring now to the drawings,  FIGS. 1–4  illustrate a magnetic latching switch  10  in accordance with the present invention. 
   As seen in  FIGS. 1 and 2 , the switch  10  is comprised of a case or housing  12  provided with a seal  14  at its upper end and joined to an end cap  16  by a set of fasteners  18 . The end cap  16  is formed with a riser  20  provided with a pair of cylindrical tapped inserts  22  on opposite ends which are used for mounting the switch  10  to a support surface. The riser  20  includes a recessed central portion for frictionally retaining an O-ring  24  beneath a cylindrical sleeve  26 . The bottom of the housing  12  has fastened thereto an inlet nozzle  28  with an inlet passageway  30  for admitting pressurized fluid such as gas which will act as a counteracting force in the switch operation. The exterior of the inlet nozzle  28  is formed with a circumferential groove  31  for frictionally retaining a hose or the like which carries the gas into the switch. A sidewall of the housing  12  has a pair of spaced-apart threaded fastener shafts  32  integral with a pair of stationary electrical lugs  34  protruding outwardly therefrom for mounting a pair of spaced-apart stationary blades  36  thereon. Upper ends of the blades  36  are held in place by nuts  38  screwed upon the shafts  32 . Lower ends of the blades  36  have terminal ends  40  which provide an electrical connection for the switch  10 . The stationary lugs  34  extend away from the blades  36  and are mounted against a surface of a recessed upper cavity  41  of the housing  12 . 
   As seen better in  FIG. 2 , the inlet passageway  30  communicates with a chamber  42  formed inside a lower part of the housing  12 . A movable piston  44  has a bottom and sidewalls attached to a pressure sensitive means in the form of a flexible diaphragm  46  having peripheral surfaces sealed to an annular ring  48  partially defining the chamber  42 . The diaphragm  46  has convoluted portions  50  which lie between the outer sidewall periphery of the piston  44  and the inner sidewall periphery of the chamber  42 . As will be appreciated, inlet gas flowing through the passageway  30  into the chamber  42  at a predetermined pressure enables the piston  44  and diaphragm  46  to be vertically displaced in the chamber  42 . A cylindrical piston pin  52  extends upwardly in fixed relationship from the piston  44 . The piston pin  52  passes through a central hole  54  formed in a wall  56  extending transversely across the housing  12 . 
   The wall  56  defines the bottom of a pocket  57  formed inside the housing  12 . Cylindrical internal surfaces forming the pocket  57  fixedly receive a cylindrical shell  58 . A flux washer  60  is secured within the lower end of the shell  58 , and a permanent magnet  62  of smaller diameter than the flux washer  60  is attached on top of the washer. A cylindrical core  64  having the same diameter as the magnet  62  is rigidly attached to the upper end of the magnet  62 . The magnet  62  and the core  64  are inserted within a cylindrical retainer  66  having a radially enlarged base  68 . A coiled latch spring  70  surrounds the outside walls of the retainer  66  and has a lower end which rests on the base  68 . The latch spring  70  lies spaced inside the internal sidewalls of the shell  58 . The flux washer  60 , the magnet  62  and the core  64  are formed with aligned apertures and register with central hole  56  for slidably receiving the piston pin  52 . The pin  52  moves vertically relative to washer  60 , magnet  62  and core  64  according to movement of piston  44  as determined by a predetermined counteracting force such as the inlet gas acting against one side of diaphragm  46 . 
   A movable magnet in the form a metallic armature  72  is disposed in the cavity  41  and is normally held fast against the top of the shell  58  and the core  64  by means of permanent magnet  62 . The permanent magnet  62  creates a magnetic flux through the core  64  to hold the armature  72  in contact with the shell  58  against the force of the latch spring  70  which is normally compressed between the base  68  of the retainer  66  and the underside of the armature  72 . The magnetic force created by the permanent magnet  62  is greater than the compressive force of the latch spring  70  so that the magnet  62  holds the armature  72  in a closed or latched position shown in  FIG. 2 . 
   In this position, a movable blade  74  lies spaced slightly above the armature  72 . The bottom of the armature  72  is normally spaced slightly above the top end of the piston pin  52 . The ends of the movable blade  74  are provided with electrical contacts  76  which are normally held engaged against the stationary lugs  34  by the force of a coiled contact spring  78 . An upper end of the contact spring  78  surrounds a central well  80  formed in the end cap  16  which holds the sleeve  26  and O-ring  24 . The contact spring  78  is normally compressed between the end cap  16  and the upper surface of the movable blade  74 , and provides a closing force to hold the contacts  76  against the lugs  34 . The force of the contact spring  78  is less than the force of the latch spring  70  acting on the armature  72 . 
   A generally cylindrical reset pin  82  is disposed for vertical movement within the interior of the contact spring  78  and is formed with a radially enlarged stop portion  84 . As will be appreciated hereafter, the stop portion  84  is engagable with the bottom of the well  80  when the switch  10  is in the fully open, unlatched or disengaged position. The reset pin  82  includes an upper portion which slides through the sleeve  26  and the O-ring  24 , and a lower portion which slides through a central opening in the movable blade  74 . The bottom end of the reset pin  82  engages the top of the armature  72 . In the closed or latched position of  FIGS. 1 and 2 , the top end of the reset pin  82  protrudes slightly from the riser  20  on the end caps  16 . 
   The switch  10  relies upon the design of a biasing system comprised of the magnet  62 , armature  72 , latching spring  70  and contact spring  78  in reaction to a counteracting force against diaphragm  46 . 
   In use, the switch  10  is normally in the closed, engaged or latched position of  FIGS. 1 and 2  in which the movable contacts  76  are engageable with the stationary lugs  34  and complete an electrical connection for a device connected to the terminals  40 . The inlet nozzle  28  is coupled to a hose or the like (not shown) which permits a pressurized gaseous flow into the passageway  30  and the chamber  42  against the diaphragm  46 . Should the pressure of the incoming gas increase, the piston  44  elevates and the piston pin  52  is forced upwardly into contact with the armature  72  until the pressure acting on the lower side of the diaphragm  46  exceeds the magnetic holding force between the magnet  62  and the armature  72 . The armature  72  is then initially separated from the core  64  and the shell  58  as shown in  FIG. 3 , and the magnetic force rapidly decreases due to the air gap  85  between the magnet  62  and the armature  72 . Once the air gap  85  is created, the compressed latch spring  70  expands forcing the movable blade  74  upwardly so that the contacts  76  quickly separate from the stationary lugs  34  to break the electrical connection and create the open or unlatched position. At the same time, the opening force of the latch spring  70  will overcome the closing force of the contact spring  78  driving the armature  72  against the bottom of the reset pin  82  and into contact with the bottom of the movable blade  74 . The piston pin  52  begins moving upwardly and continues to move upwardly as indicated by the arrows in  FIG. 4 , with the armature  72  of movable blade  74 . This movement continues until the stop portion  84  on reset pin  82  engages the bottom of well  80 , the top of the movable blade  74  engages depending portions of the end cap  16 , and the top ends of the contact  76  engage upper walls  86  of the end cap  16 . In this fully open or unlatched condition, the top of the reset pin  82  protrudes more prominently from the top of the switch  10 . 
   Once the gas pressure has properly dissipated below a certain level, the switch  10  is moved back to the closed or latched position by manually pushing down on the top of the reset pin  82  to move the armature  72  against the force of the latch spring  70  and reestablish the holding force between the permanent magnet  62  and the armature  72 . This will also allow the contact spring  78  to push the movable blade  74  downwardly and bring the contact  76  into engagement with the stationary lugs  34 . 
   The present invention thus provides a magnetic latching switch which is responsive to a predetermined gas pressure or other counteracting force to overcome a magnetic biasing force and allow a spring member to change the state of an electrical connection. 
   While the invention has been described with reference to a preferred embodiment, those skilled in the art will appreciate that certain substitutions, alterations and omissions may be made without departing from the spirit thereof. For example, while the preferred embodiment has disclosed the use of gas pressure as a counteracting force, it should be understood that one suitable alternative would be an electrical coil wrapped around the core which, when energized, would create a magnetic field that would oppose the magnetic field of the magnet. Also, while the description indicates that the electrical contacts move from a closed, latched position to an open unlatched position, it should be appreciated that the contacts may also move from an open to a closed position. Accordingly, the foregoing description is meant to be exemplary only and should not be deemed limitative on the scope of the invention set forth with the following claims.