US3360624A

US3360624A - Electric switch structure having externally accessible drift-free adjustment

Info

Publication number: US3360624A
Application number: US503954A
Authority: US
Inventors: Carl L Erwin; Iii Theodore G Scheid
Original assignee: Northern Electric Co Ltd
Current assignee: Nortel Networks Ltd
Priority date: 1965-10-23
Filing date: 1965-10-23
Publication date: 1967-12-26
Anticipated expiration: 1984-12-26

Description

Dec. 26, 1967 L. ERWIN ETAL ELECTRIC SWITCH STRUCTURE HAVING EXTERNALL 3,360,624 Y ACCESSIBLE DRIFTFREE ADJUSTMENT Filed Oct. 25, 1965 Z L j "'llz 32 26 INVENTORS CAF/L L [QW/N @5050/125 G JWM/@ m' M 'd-d TTORNEYS United States Patent O 3,360,624 ELECTRIC SWITCH STRUCTURE HAVING EXTERNALLY ACCESSIBLE DRIFT-FREE ADJUSTMENT Carl L. Erwin and Theodore G. Scheid III, Chicago, Ill., assignors to Northern Electric Company, Chicago, Ill., a corporation of Delaware Filed Oct. 23, 1965, Ser. No. 503,954 Claims. (Cl. 200--138) ABSTRACT 0F THE DISCLOSURE An electrical switch structure includes a metal case having a tubular deformation-free portion which receives contact blades, the xed ends of the blades being rigidly supported by a rigid insulator and separated from each other by an insulative slida'ble member that holds the parts together `and also has a cam portion that coacts with a dimple on one blade for adjusting the contact of one blade away from that of the other.

This invention relates generally to electric switches, and more specifically to a switch structure which embodies a slidably movable insulative spacer disposed between elements thereof.

Although the principles of the present invention may be includes in various switches, a particularly useful application is made in a miniaturized switch, particularly where such switch is a thermostatic limit switch.

In the assembly and calibration of miniaturized thermostatic switches, some form of calibration is necessary. Prior switch structures have necessitated permanent bending of a blade, bending of a metallic case, bending of a tongue which is integral with a 4metallic case, or forming an indentation in a metallic case. In all such instances, a calibration force is applied to the part to be permanently deformed, which inherently has a degree of resiliency so that such part being bent springs back to some extent. This factor makes calibration techniques and apparatus quite cumbersome since the part must be deflected beyond the point where it should remain when properly calibrated.

The present invention is particularly useful in connection with such a miniaturized thermostat and includes a slidably movable wedge which holds the components together equally well at all positions, and which further, depending on its position, effects proper calibration of the device. In such structure, there is no permanent deformation of any resilient element as a part of the calibration process, and therefore calibration is achieved by positive displacement as there is no spring-back involved.

Accordingly, it is an object of the present invention to provide a novel switch construction.

A further object of the present invention is to provide a switch construction wherein the spring-back problem is entirely eliminated from its calibration process.

Yet another object of the present invention is to provide a switch construction which is particularly adapted to be manufactured in miniaturized form.

A still further object of the present invention is to provide a heavy-duty industrial type of switch is a minimum amount of volumetric space.

Many other advantages, features and additional objects of the present invention will become manifest to those versed in the art upon making reference to the detailed description and to the accompanying sheet of drawings in which a preferred structural embodiment incorporating the principles of the present invention is shown by way of illustrative example.

ICC

On the drawings:

FIG. l is a side elevational View, drawn in actual size, of a thermostatic switch provided in accordance with the principles of the present invention;

FIG. 2 is an enlarged cross-sectional view of the switch of FIG. l;

FIG. 3 is an enlarged end View of the switch of FIG. l;

FIG. 4 is a fragmentary cross-sectional view taken along line IV-lV of FIG. 2;

FIG. 5 is a fragmentary cross-sectional view of the xed end of a blade shown in its disassembled state; and

FIG. 6 is an enlarged cross-sectional view of a modified form of the switch shown in FIG. 2.

As shown on the drawings:

The principles of this invention are particularly useful when embodied in an electric switch such as illustrated `n FIG. 1, generally indicated by the numeral 10. In actual size, this switch is approximately 0.80 inch in length exclusive of the terminals, and as such is termed a miniaturized switch. As shown in FIG. 2, the switch 10 includes a rst electric contact blade 11, a second electric contact blade 12, a bimetal blade 13, an insulative spacer 14, and rigid means generally indicated vat 15 for holding the blades 11-13, such rigid means comprising an insulative spacing member 16 and a tubular case 17.

The electric contact blade 11 has a movable end 18 to which there is secured an electric contact 19. Intermediate its ends, the contact blade 11 has a projection or cam portion 2i). The contact blade 11 has a fixed end 21 best seen in FIG. 4 which includes a pair of oppositely directed

shoulders

22, 23 which coact with a pair of oppositely directed

shoulders

24, 25 on the insulative spacing member 16. The rigid end 21 of the contact blade 11 further has an integral spring 26 which comprises a struck-out portion which normally projects from the plane of the fixed end 21 as shown in FIG. 5. However, in assembly, the associated elements hold the struck-out portion or spring 26 in a position which is substantially coplanar with such xed end 21.

The contact blade 12 is identical to the contact blade 11 for interchangeability, which blades further include a second projection 27 near the movable end 18 thereof.

The b imetal blade 13 has a thickness which is greatly exaggerated in FIG. 2 to facilitate illustration. At its tixed end, the bimetal blade 13 has oppositely directed shoulders similar to the

shoulders

22, 23 described above which coact with the insulative spacing member 16 in the manner described. The bimetal blade 13 has an aperture 28 which receives the projection 20 of the blade 12. The movable or free end of the bimetal blade 13 engages the projection 27 of the contact blade 12. The bimetal blade 13 has a high expansion side 29 which faces the contact blade 11, and in response to a predetermined temperature, the bimetal 13, acting through the projection 27, causes the -contacts 19 of the contact blades 12 and -11 to separate. If desired, the electric contact blade 12 and the bimetal blade 13 may be jointly reversed so that the high expansion side 29 is directed away from the contact blade 11. With such construction, the contacts 19 are normally open, and move to a closed position in response to a suitable temperature increase.

The insulative spacer 14 comprises plastic and has an inner end 30 which serves as a cam or wedge and acts on the projection or cam portion 20 of the contact blade 11. The insulative spacer 14 is made symmetrical so that either side will present such a cam surface 30.

The rigid means 15 extends about the fixed ends 21 of the

contact blades

11 and 12, extends Iabout the fixed end of the bimetal blade 13, as well as about the rigid insulative spacer 14. To this end, the rigid means 15 includes the insulative spacing member 16 which in this embodiment is provided as a pair of spacing member sections 16a and 16b. The outer end of the spacing member 16 comprises a ange 31 against which the case 17 abuts, while the inner end is beveled as at 32 to facilitate assembly. For the same purpose, the entrant end of the case 17 is likewise beveled, and therefore the flange 31 has a complemental beveled surface. As seen in FIGS. 2 and 4, the insulative spacing member 16 holds the various blades 11- 13 in spaced relation to the conductive case 17, and therefore the case 17 is electrically dead or neutral. The insulative spacing member also comprises plastic, but for higher temperature applications, the plastic components may be replaced with similar ceramic components. The spacing member sections 16a and 16b are held together by the entrant or open end of the tubular case 17, such case end tightly encircling the spacing member 16.

Suitable conductors 33 may be soldered or otherwise secured to the exposed ends of the

contact blades

11, 12.

The switch is assembled readily by hand and the insulative spacer 14 is partially inserted. As soon as the cam portion 3@ thereof has fully entered, the spacer 14 tightly urges the blades 11-13 against the rigid means 15 and holds the

contact blades

11, 12 in spaced juxtaposition to each other. Such assembly also serves to deflect the spring means 26 into the plane of the

contact blade

11 or 12, which spring means thus act perpendicularly to the direction of spacer movement, and augment the frictional resistance to sliding ot such spacer 14. The shoulder means 22-25 preclude movement of any of the blades 11-13 in either direction parallel to the direction of movement of the spacer 14.

After the spacer has entered 4to the degree necessary to engage the cam portion 30 of the spacer with the cam portion 20 of the contact blade 11, further movement serves to preset or adjust the relative position of the movable ends 18, which constitutes the calibration of the thermostatic switch 10. By this means of calibration, such presetting is accomplished without permanently bending any element, and can be accomplished by direct ydisplacement means. When such calibration has been completed, it is preferable that the cavity yat the outer end of the insulative spacer 14 be covered with glyptol or the like the serve as a lock, and as an indicator as to possible subsequent tampering with its position. If desired, the joint between the cover 17 and the flange 31 may be varnished or otherwise sealed, and likewise, the various joints shown in FIG. 3 may be sealed if desired.

When the

contact blades

11 and 12 comprise Phosphor bronze, and when a separate bimetal 13 is employed as shown in FIG. 2, the disclosed embodiment may be used for heavy duty industrial applications, even though the same is of miniaturized size. By heavy duty industrial applications is meant that the switch will readily achieve a 7.5-ampere rating under standards established by Underwriters Laboratories. Where a lower electrical rating will suice, one contact blade 34 may comprise a bimetal as shown in FIG. 6, such blade 34 having a lixed end with shoulder means as shown at 22, 23 in FIG. 4. The bimetal contact blade 34 is illustrated in exaggerated thickness for clarity of illustration. However, a slightly thickened insulative spacing member section 16C may be employed in place of the section 16a to compensate for the net difference in thickness. The switch shown in FIG. 6 is otherwise the same as that shown in FIG. 2.

Although various minor modifications might 'be suggested by those versed in the art, it should be understood that we wish to embody within the scope of the patent warranted hereon all such embodiments as reasonably and properly come within the scope of our contribution to the art.

We claim as our invention:

1. An electrical switch structure, comprising in combination:

(a) a case of metal having a tubular configuration free of deformation;

(b) an electrical contact supported therein;

(c) an electrical contact blade having a fixed end and a movable contact end engageable with said contact;

(d) separate rigid insulative means fixedly disposed free of deformation within an end of said tubular case and tightly encircled by the deformation-free tubular case, said rigid means extending about said xed end of said blade in spaced relation to one side thereof so as to leave a space therebetween within said rigid means, such space extending from outside of said case into the interior of said case;

(e) a separate insulative spacer disposed against said one side of said blade and coacting with said rigid means in rigidly supporting said fixed end, said spacer closing said space and being externally accessible for being slidably moved while coacting in the rigid support of said fixed end; and

(f) spring means acting on said slidable spacer in a direction perpendicular to the direction in which said spacer is slidable, and augmenting the frictional resistance of said spacer to sliding.

2. A switch structure according to claim 1, in which said spring means is a struck-out portion of said lixed end of said blade, said portion being held against its resilience by said slidable spacer in a position which is substantially coplanar with said fixed end.

3. In an electrical switch structure, the combination comprising:

(a) a pair of electrical contact blades arranged in spaced juxtaposition to each other, and each having lixed and movable ends, one of said blades having a cam portion projecting as a dimple therefrom;

(b) rigid means extending about and supporting the fixed ends of said blades remotely from said dimple, and insulating said fixed ends from each other; and

(c) an insulative spacer slidably movably disposed between said fixed ends and yurging them against said rigid means, said spacer having a cam portion projecting beyond said rigid means and being further engageable with said dimple for moving one of said movable ends away from the other.

4. In an electrical switch structure, the combination comprising:

(a) a pair of electrical contact blades arranged in spaced juxtaposition to each other, and each having fixed and movable ends, one of said blades having a cam portion projecting as a dimple therefrom;

(b) rigid means extending about and supporting the fixed ends of said blades remotely from said dimple, and insulating said iixed ends from each other;

(c) an insulative spacer slidably movably disposed between said xed ends and urging them against said rigid means, said spacer having a cam portion projecting beyond said rigid means and being further engageable with said dimple for moving one of said movable ends away from the other; and

(d) a third blade, said third blade being of bimetal material, extending along and having its low expansion side disposed against the other of said contact blades, and having a lixed end supported by said rigid means;

(e) said bimetal blade and said other contact blade being selectively positionable as a pair in one position with the high-expansion side of the bimetal blade directed toward said one contact blade to provide a normally closed switch, and in a second position with said highexpansion side of the bimetal blade directed away from said one contact blade to provide a normally open switch.

5. An electrical switch structure, comprising in combination:

(a) a case of metal having a tubular configuration free of deformation;

6 (b) a pair of electrical contact blades disposed in said said rigid means and being further engageable with case and arranged in spaced juxtaposition to each said dimple for moving one of said movable ends other, and each having fixed and movable ends, one away from the other. of said blades having a cam portion projecting as a dimple therefrom; 5 References Cited (c) separate rigid insulative means xedly disposed UNITED STATES PATENTS free of deformation within an end of said tubular T case and tightly encircled by the deformation-free Re'24308 4/1957 Colegrove' tubular case, said rigid means extending about said lmelsbaugh zogofl fixed ends of said blades remotely from said dimplc 10 2717937 9/1955 L ly -t-- "2 00 E9 X and leaving a space between said blades within said 2871315 1/1959 Delf e a 2E) 138 rigid means, Such Space extending from outside of 881,290 4/1959 Dales 20o-138 Said case into the interior of said case; and 2,944,324 7/1960 Ma es 60 g8 X (d) an insulative spacer slidably movably disposed be- 3066206 11/1962 D O15/ef tween said xed ends and urging them against Said 15 a es 20o- 13g rigid means, said spacer closing said space and being l y externally accessible for being slidably moved while BERNARD A GILHEANY P'lma') Examme" coacting in the rigid support of said fixed ends, and H- A- LEWITTER, SSSHHI Examiner. said spacer having a cam portion projecting beyond

Claims

1. AN ELECTRICAL SWITCH STRUCTURE, COMPRISING IN COMBINATION: (A) A CASE OF METAL HAVING A TUBULAR CONFIGURATION FREE OF DEFORMATION; (B) AN ELECTRICAL CONTACT SUPPORTED THEREIN; (C) AN ELECTRICAL CONTACT BLADE HAVING A FIXED END AND A MOVABLE CONTACT END ENGAGEABLE WITH SAID CONTACT; (D) SEPARATE RIGID INSULATIVE MEANS FIXEDLY DISPOSED FREE OF DEFORMATION WITHIN AN END OF SAID TUBULAR CASE AND TIGHTLY ENCIRCLED BY THE DEFORMATION-FREE TUBULAR CASE, SAID RIGID MEANS EXTENDING ABOUT SAID FIXED END OF SAID BLADE IN SPACED RELATION TO ONE SIDE THEREOF SO AS TO LEAVE A SPACE THEREBETWEEN WITHIN SAID RIGID MEANS, SUCH SPACE EXTENDING FROM OUTSIDE OF SAID CASE INTO THE INTERIOR OF SAID CASE; (E) A SEPARATE INSULATIVE SPACER DISPOSED AGAINST SAID ONE SIDE OF SAID BLADE AND COACTING WITH SAID RIGID MEANS IN RIGIDLY SUPPORTING SAID FIXED END, SAID SPACER CLOSING SAID SPACE AND BEING EXTERNALLY ACCESSIBLE FOR BEING SLIDABLY MOVED WHILE COACTING IN THE RIGID SUPPORT OF SAID FIXED END; AND (F) SPRING MEANS ACTING ON SAID SLIDABLE SPACER IN A DIRECTION PERPENDICULAR TO THE DIRECTION IN WHICH SAID SPACER IS SLIDABLE, AND AUGMENTING THE FRICTIONAL RESISTANCE OF SAID SPACER TO SLIDING.