US3155800A

US3155800A - Single action temperature sensitive electrical switch including camming means for a plunger retaining member

Info

Publication number: US3155800A
Application number: US250978A
Authority: US
Inventors: Robert F Denton
Original assignee: GENISCO Tech CORP
Current assignee: GENISCO Tech CORP
Priority date: 1963-01-02
Filing date: 1963-01-02
Publication date: 1964-11-03
Anticipated expiration: 1981-11-03

Description

Nov. 3, 1964 R F. DENTON SINGLE ACTION TEMPERATURE SENSITIVE ELECTRICAL SWITCH INCLUDING CAMMING MEANS FOR A PLUNGER RETAINING MEMBER Original Filed June 13, 1960 3,155,800 SINGLE ACTIGN TEMPERATURE ENSiTiVE ELECTRIEAL EWITQCH llNCLUEl-NG CAB/i- MENG MEANS EUR A PLUNGER RETAIN- ING MEMBER Rohert F. Denton, West Los Angel-es, Caiifi, assignor, by

Inesne assignments, to Geniseo Teehnelogy Corporation, a eerporation of Caiiziornia Continuation of application Ser. No. 35,557, dune 13, I969. This application Jan. 2, 1963, Ser. No. 256,978 8 Claims. (Ci. 200-142) The present invention relates to a single-action ternperature-sensitive electrical switch, and more particularly to such a switch in which a spring-loaded member is released for movement by the melting of a temperaturesensitive pellet.

The present application is a continuation of my copending application Serial No. 35,557 filed June 13, 1960, and subsequently abandoned.

Temperature-sensitive compounds in various forms are used for electrical control purposes. In some electrical switching devices a pellet of temperature sensitive material is placed in confinement so that the melting of the pellet at the critical control temperature permits a springbiased member to move to accomplish a switching action. In prior devices of this kind the direction of movement of the movable member has been along the axis of confinement of the pellet.

One object of the present invention is to provide a device of the above type in which the spring-biased memher is released for movement at a right angle to the axis of confinement of the pellet.

Another object of the invention is to provide a tem-' perature-sensitive switch having a single set of parts which with normally-closed device or a normally-open device.

A further object of the invention is to provide a temperature-sensitive switch which is cheap and easy to manufacture and has high reliability.

The above and other objects and advantages of the invention will be more readily apparent from the following description considered in conjunction with the accompanying drawing, in which:

FIGURE 1 is a longitudinal cross-sectional view of the invention arranged to provide a normally-closed switch;

FIGURE 2 is a longitudinal cross-sectional view of the invention arranged to provide a normally-open switch; and

FIGURE 3 is a fragmentary transverse view taken on the line 3-3 of FIGURE 2.

Referring now to the drawing it will be seen that the invention comprises an elongated housing containing a spring-biased switching member which is selectively released for longitudinal movement within the housing so as to accomplish a desired switching action. In one end of the housing there are provided a pair of electrical terminals adapted to be connected to an external circuit and which, in conjunction with the switching element, accomplish the desired switching action. The other end of the housing contains a temperature-sensitive pellet and a mechanism which, in response to the melting of thepellet, releases the switching element for longitudinal movement within the housing.

Referring now more specifically to FIGURE 1, a metallic switch housing A has a substantially cylindrical configuration. An insulating header E is suspended within one end of the switch housing A and is retained securely in place by an in-turned end flange 11 of the metal housing.- A spaced pair of electrical terminals C project longitudinally inwardly from the header B, being also fanned slight modification may provide either a rates Eatent slightly outwardly in a somewhat V-shaped configuration. Terminals C are the ends of conductors 18 which outside the housing A, may be connected to an external electrical circuit.

I A cylindrical insulating lining D extends throughout most of the interior length of housing A, and has one end 13 in secure engagement with header B so that terminals C are safely insulated from the housing A. A switching element or plunger E is positioned approximately in the longitudinal center of housing A and adapted for longitudinal sliding movement within the liner D. Plunger E has a wedge-shaped nose 15 which is adapted to concurrently engage the inwardly facing surfaces of both of the terminals C. Plunger E is made of an insulating material, and both the liner D and plunger E may be made of Bakelite or similar material.

Except for its nose 15 which is in the form of a fiat wedge (see FIGURE 3) the plunger E is symmetrical about its longitudinal axis. A relatively large concen tric bore in is formed in the rearward end of plunger E. An aligned pair of small radial bores, not shown, are formed through the outer shell of plunger E on opposite sides of the bore 16. A plunger pin F slidably retained in the aligned pair of small bores extends transversely through the large bore 16 of plunger E. A helical spring G whose inner diameter is larger than the diameter of bore 16 of the plunger E is concentrically disposed within liner D on the rearward side of plunger E. A spring retainer member H having an approximately V-shaped configuration has its apex disposed within the bore 16 of plunger E and extending around the pin F so as to be supported thereby. The oppositely disposed

legs

21, 22 of member H extend through spring G and substantially rearwardly thereof.

A metallic pellet housing I is disposed within the other end of switch housing A and engages the other end 14 of insulating liner D for retaining the latter in place. The corresponding end of switch housing A has an outwardly turned flange 12 which merges into a short longitudinal section 26 of the housing A that is of somewhat larger diameter than the main portion of the switch housing. On the rearward end of longitudinal section 26 there is formed an inwardly turned flange 27 which is parallel to and substantially coterminous with the flange 12.

The pellet housing I is symmetrical about its longitudinal axis, and has a hollow interior providing a pellet chamber 30. On its forward end, which is in contact with one end of the spring G, the pellet housing I has formed therein an opening 31 whose diameter is somewhat less than the internal diameter of the spring G. Immediately to the rear of opening 31 there is formed a sloped circumferential shoulder 32 which faces away from the opening 31. Chamber 30 then extends at constant diameter throughout the greater part of the length of the pellet housing I, toward the rearward end thereof where a larger sloped circumferential shoulder 33 is formed. Shoulder 33 also faces away from the opening 31.

Spring retainer member H consists of a thin flat metal strip or strap which, after being formed to its approximately V-shaped configuration, retains a considerable degree of resilience. Each

leg

21, 22 of member H has a first oiiset portion 23 which conforms to the shape of sloped shoulder 32, as well as a second offset portion 24 which conforms to the shape of shoulder 33.

A temperature-sensitive peliet E has the form of a solid cylinder. Pellet I occupies pellet chamber 38, in engagement with the inner surfaces of both tainer member H between the first offset portions 23 second offset portions 24 thereof. The diameter of pellet I is such as to force the retainer member legs tightly against the wall of pellet chamber legs of spring re- An outwardly extending circumferential ilange 35 formed on the rearward end of pellet housing I engage the flange 12 of switch housing A. A fiat circular metal base place K has a circumferential portion of its forward surface in engagement with the circumferential surface of the rear end, including flange 35, of the pellet housing I. The center portion of the forward surface of base place K engages one flat end surface of pellet I, the other flat end surface of pellet J being m inly open to the opening 31 of the pellet housing, but having its outer circumferential edge retained by shoulder 32 of pellet housing 1 and offset portions 23 of the legs of member H. On its rearward circumferential edge the base plate K is retained within the flange 27 of switch housing A.

The invention is assembled as follows. The insulating header B is formed around the spaced conductors 1% which provide terminals C. Header B is then attached to the end of metal switch housing A in retaining engagement with flange 11 thereof. Insulating liner D is slidably inserted within the housing A.

A sub-assembly is then prepared as follows. Spring retainer strap H is positioned with its legs inserted within pellet housing I. Pellet I is inserted for retaining member H in place. Spring G is placed on the forward end of pellet housing I, concentrically surrounding the apex and other projecting portions of member H. Plunger E is placed in front of the forward end of spring G, and plunger E and pellet housing I are compressed together so that the apex of the member H enters the bore '16 of plunger E. Pin F is then transversely inserted through the small bores in plunger E so as to retain the apex of member H.

The entire sub-assembly consisting of pellet housing I, pellet 1, member H, spring G, plunger E, and pin F, is then inserted in a forward direction into the rear end of switch housing A. Thereafter, base plate K is placed in position, and flange 27 (previously left straight) is crimped over so as to securely retain it.

The operation of the invention is as follows. A source of heat, which is to be used for temperature control purposes, is placed in conductive engagement with the base plate K. Heat from the heat source flows through base plate K into pellet l, and when its critical temperature is reached the pellet I suddenly melts. Since each oifset portion of member H is hooked over the corresponding shoulder of pellet housing I, the effect of the sloped configuration of both parts is to provide a cam action. Thus, when pellet J melts, the forward thrust of spring G upon plunger E, and hence upon the apex of member H, forces the leg ends of member H to move radially inward within the pellet housing I. The leg ends are therefore no longer longitudinally retained by the pellet housing, plunger E is no longer restrained by member H, and is forced by spring G to move longitudinally within liner D so as to engage the terminals C.

In FIGURE 1 a jumper wire L provides a transverse connection between the terminals C. Jumper wire L is relatively weak and hence frangible, and when plunger E moves forward the nose 15 thereof breaks the wire L and consequently interrupts the circuit between conductors 1%.

The normally-open switch of FIGURE 2 is identical to the normally-closed switch of FIGURE 1, except in two respects. First, the jumper wire L is omitted, and the circuit is normally-open. Secondly, the nose 15 of plunger E is electro-plated with a conductive coating M. When nose 15 of the plunger E interengages terminals C the metal coating M provides a continuous circuit therebetween.

The invention has been described in considerable detail in order to comply with the patent laws by providing a full public disclosure of at least one of its forms. However, such detailed description is not intended in any way to limit the broad features or principles of the invention, or the scope of patent monopoly to be granted.

What I claim is:

1. A single-action temperature-sensitive electrical switch comprising:

an elongated housing having a transversely spaced pair of electrical terminals in the interior of one end thereof; a plunger in the mid-portion of said housing adapted to slide toward said terminals for producing an electrical switching action; means within the other end of said housing providing a pellet chamber having an opening facing toward said plunger, and having an interior shoulder facing away from said opening; a spring biasing said plunger for movement toward said terminals; a resilient spring retaining member having one end fastened to said plunger, its other end extending through said opening into said pellet chamber and having an offset portion which hooks over said shoulder; a temperature-sensitive pellet occupying said pellet chamber and compressively engaged by said spring retaining member for maintaining'the engagement of said offset portion of said member with said shoulder; and means for applying heat to said pellet from the exterior of said housing to melt said pellet, said offset portion of said member and said shoulder together then providing a cam action for forcing said other end of said member radially inwardly of said chamber as said plunger moves toward said terminals.

2. A switch as claimed in claim 1 in which both said pellet chamber shoulder and said offset portion of said member are sloped in a direction along the length of said housing.

3. A switch as claimed in claim 2 in which said member has a pair of oppositely disposed legs positioned on respective sides or" said pellet, each of said legs has an offset portion, and said sloped shoulder extends circumferentially around said pellet chamber and is engaged by the offset portion of each of said legs.

4. A switch as claimed in claim 1 in which said lastnamed means is a llat circular metallic base plate which closes said other end of said housing, and said pellet has a fiat surface in flush engagement with the inner flat surface of said base plate.

5. In a temperature-sensitive electrical switch, the combination comprising:

housing means providing'a pellet chamber having an opening at one end and an interior shoulder facing away from said opening; an elongated resilient plunger retaining member extending through said opening into said chamber and having an offset portion which hooks over said shoulder; spring means biasing said member for longitudinal movement away from said chamber, said shoulder and said offset portion being "of such configuration as to cooperatively provide a cam action for forcing said offset portion in response to longitudinal movement of said member to move transversely inwardly of said chamher; and a compressively stressed temperature-sensitive pellet occupying said chamber and maintaining said offset portion of said member in engagement with said shoulder for inhibiting longitudinal movement of said member until the application of heat causes said pellet to melt.

' 6. A switch as claimed in claim 5 in which both said pellet chamber shoulder and said offset portion of said member are sloped in a direction along the length of said member.

7. A single-action temperature-sensitive electrical switch comprising:

an elongated substantially cylindrical housing;

an insulating header secured in one end of said housing and carrying a spaced pair of electrical terminals adapted for external circuit connection and which extend within said housing;

a plunger disposed in the longitudinal mid-portion of said housing and adapted to slide toward said terminals for producing an electrical switching action;

means within the other end of said housing providing a pellet chamber having an end opening facing toward said plunger, said pellet chamber having first and second longitudinally separated and longitudinally sloping circumferential shoulders which face away from said end opening;

a compressed helical spring disposed on the pellet chamber side of said plunger;

an approximately ti-shaped metal strap having the apex thereof fastened to said plunger with its two legs extending through said spring and through said end opening into said pellet chamber, each of said strap legs having a longitudinally separated pair of sloping offset portions which conform to said pellet chamber shoulders;

a solid cylindrical temperature-sensitive pellet occupying said pellet chamber in relatively tight engagement with the longitudinal portions of said strap legs lying between the ofiset portions thereof;

and means for applying heat from the exterior of said housing so as to melt said pellet.

8. A single-action temperature sensitive electrical switch comprising:

an elongatedcylindrical housing having a transversely spaced pair of electrical terminals in the interior of one end thereof;

a frangible wire extending transversely between said terminals;

a plunger disposed within the mid-portion of said housing, said plunger being selectively slidahle toward said terminals and the forward end thereof being adapted to sever said frangible wire for interrupting the electrical circuit between said terminals;

a cylindrical skirt disposed within the other end of said housing and forming an annular shoulder facing toward said plunger;

a helical compression spring having 'one end thereof in engagement with said annular shoulder and the other end thereof in engagement with the rearward end of said plunger, and adapted to bias said plunger toward said terminals;

the interior of said cylindrical skirt having a smalldiameter portion adjacent said annular shoulder, a medium-diameter portion in its mid-section, and a large-diameter portion at the extremity of said other end of said housing, said cylindrical skirt also having first and second circumferential shoulders at respective ends of said medium-diameter portion, both of which are longitudinally sloped;

an approximately V-shaped metal retaining strap having the apex thereof fastened to said plunger with its two legs extending through said spring and into opposite sides of the interior of said cylindrical skirt, each of said retaining strap legs having a longitudinally separated pair of sloping offset portions which conform to and normally engage respective ones of said first and second circumferential shoulders;

a solid cylindrical temperature-sensitive pellet occupying said medium-diameter portion of said cylindrical skirt interior in relatively tight engagement with the longitudinal portions of said retaining strap legs lying etween the oifset portions thereof, and normally maintained in compression thereby;

and means for applying heat through said other end of said housing to said pellet;

the action being such that when said pellet reaches its melting point and commences to flow out of said medium-diameter portion of said cylindrical skirt interior, the restraining force imposed upon said four oifset portions of said retaining strap legs is no longer sufiicient to overcome said spring, and said strap legs move radially inwardly into the space formerly ocupied by said pellet as said spring forcibly drives said plunger into contact with said terminals.

References Cited in the file of this patent UNITED STATES PATENTS 630,671 Des Isles Aug. 8, 1899 748,240 Wall Dec. 29, 1903 1,875,928 Lovekin Sept. 6, 1932 1,910,944 Austin May 23, 1933 2,159,423 Bussmann May 23, 1939 2,934,622 Massar Apr. 26, 1960 2,934,625 Patrichi Apr. 26, 1960 2,934,628 Massar et al Apr. 26, 1960

Claims

1. A SINGLE-ACTION TEMPERATURE-SENSITIVE ELECTRICAL SWITCH COMPRISING: AN ELONGATED HOUSING HAVING A TRANSVERSELY SPACED PAIR OF ELECTRICAL TERMINALS IN THE INTERIOR OF ONE END THEREOF; A PLUNGER IN THE MID-PORTION OF SAID HOUSING ADAPTED TO SLIDE TOWARD SAID TERMINALS FOR PRODUCING AN ELECTRICAL SWITCHING ACTION; MEANS WITHIN THE OTHER END OF SAID HOUSING PROVIDING A PELLET CHAMBER HAVING AN OPENING FACING TOWARD SAID PLUNGER, AND HAVING AN INTERIOR SHOULDER FACING AWAY FROM SAID OPENING; A SPRING BIASING SAID PLUNGER FOR MOVEMENT TOWARD SAID TERMINALS; A RESILIENT SPRING RETAINING MEMBER HAVING ONE END FASTENED TO SAID PLUNGER, ITS OTHER END EXTENDING THROUGH SAID OPENING INTO SAID PELLET CHAMBER AND HAVING AN OFFSET PORTION WHICH HOOKS OVER SAID SHOULDER; A TEMPERATURE-SENSITIVE PELLET OCCUPYING SAID PELLET CHAMBER AND COMPRESSIVELY ENGAGED BY SAID SPRING RETAINING MEMBER FOR MAINTAINING THE ENGAGEMENT OF SAID OFFSET PORTION OF SAID MEMBER WITH SAID SHOULDER; AND MEANS FOR APPLYING HEAT TO SAID PELLET FROM THE EXTERIOR OF SAID HOUSING TO MELT SAID PELLET, SAID OFFSET PORTION OF SAID MEMBER AND SAID SHOULDER TOGETHER THEN PROVIDING A CAM ACTION FOR FORCING SAID OTHER END OF SAID MEMBER RADIALLY INWARDLY OF SAID CHAMBER AS SAID PLUNGER MOVES TOWARD SAID TERMINALS.