US2542415A - Thermostatically controlled switch - Google Patents

Description

Feb. 20, 1951 M. 1. JEFFREY Tl-IERMOSTATICALLY CONTROLLED SWITCH Original Filed Dec. 31, 1945 3 Sheets-Sheet 1 Feb. 20, 1951 M. JEFFREY 2.

'I'I-IERMOSTATICALLY CONTROLLED SWITCH Original Filed Dec. 31, 1945 3 Sheets-Sheet 2 Fig. 9

INVENTOR. NAXL. JIFFY-77E y a, a anon Feb. 20, 1951 M. L. JEFFREY 2,542,415

THERMOSTATICALLY CONTROLLED SWITCH Original Filed Dec. 31, 1945 3 Shuts-Sheet 3 206} v /9 m2 figji 209 j I O 0 O 208 207 2/0 Jr' /80 u 1? '2! 0 209 Fig. /7 1 3g H 2342/ I /86 209 2,0 .95 m7 D j awe/WM MAX 4. JEF F Patented Feb. 20, 1951 2,542,415 THERMOSTATICALLY CONTROLLED SWITCH Max L. Jeil'rey, Shaker Heights, Ohio, assignor to The National Acme Company, Cleveland, Ohio, a corporation of Ohio Original application December 31. 1945. Serial No.

638.554, now Patent No. 2,523,370, dated September 26, 1950. Divided and this application May 23, 1947, Serial No. 750,107

'1 Claims.

This invention relates to improvements in switches, and more particularly to a quick actin multipole switch. It is a division of my application, Ser. No. 638,554, filed December 31, 1945 which has resulted in Patent No. 2,523,370, dated Sept. 26, 1950.

Although multipole switches have been contemplated heretofore, there have been certain disadvantages inherent in prior structures of which it is the purpose of the present invention to overcome. For instance, they have been relatively cumbersome in structure as well as expensive to manufacture. Furthermore, efforts to lighten the structure weakened it and made the operation thereof unreliable.

By the present invention, I have provided a switch which is extremely compact and yet contains a number of features only to be found in larger and more complicated devices. The switch of my invention is characterized by its ability to quickly make and break a circuit, thus eliminating the tendency of contacts, carrying heavy current, to are. structures are such that although the contacts are relatively close together, the tendency to arc between contacts is reduced by increasing the path over which the arc would have to travel.

The invention also includes an improved snap action mechanism which provides a quick make Furthermore, the contact carrying and break of the contacts. There is also contemplated a new type of thermally operated control which causes the switch to automatically open upona power failure or in the presence of a. sustained overload.

Still other advantages of the invention and the invention itself will become more apparent from the following description of an embodiment thereof, which description is illustrated by the accompanying drawings, and forms a part of this specification.

In the drawings:

Fig. 1 is a bottom plan view of a pair of thermally controlled switches used in my invention;

Fig. 2 is a side elevational view thereof;

Fig. 3 is a top plan view of one of the switches removed from the supporting base;

Fig. 4 is an end view taken from a plane indicated by the line 26-26 of Fig. 6; i

Fig. 5 is an end view of the opposite end;

2 Fig. 6 is a section taken on the line 28-28 of Fig. 3;

Fig. '7 is a side elevational view of the thermostatic element removed from the switch;

Fig. 8 is a. plan view of the heater element removed from the assembly;

Fig. 9 is a plan view of the insulating element removed from the assembly;

Fig. 10 is an exploded view illustrating the manher of assembly;

Fig. 11 is an end elevational view of the support and actuating strip removed from the assem- Fig. 12 is the plan view of a control support removed from the assembly;

Fig. 13 is a plan view thereof;

Fig. 14 is a side elevational view of the support with the time control elements in place;

Figs. 15 and 16 are side and plan views respectively of one of the slide members used in the assembly;

Figs. 17 and 18 are similar views of the other slide element;

Figs. 19 and 20 are plan views of a pair of levers removed from the assembly;

Figs. 21 and 22 are side elevational views thereof;

Fig. 23 is an end elevational view of a fixed contact assembly removed from the switch;

Fig. 24 is a side elevational View thereof;

Fig. 25 is an end elevational view of a movable contact member;

Fig. 26 is a side view thereof.

Briefly, the invention comprises a thermally controlled overload switch adapted to open a set of contacts quickly when the load becomes greater than a certain predetermined value. This is accomplished by a compact unit of bimetal elements and heating elements adapted to operate a linkage to open the contacts. Detent mechanism holds the linkage until a certain force is developed by the bimetal elements at which time the holding is overcome and the contacts are snapped open.

Referring now to the drawings, throughout which like parts have been designated by like reference characters.

In the apparatus shown Figs. 1 and 2, there are two such devices, but since they are both the same, only one will be described. In order to mun the thermostatic switches to the main body of the switch with which they are used, a base plate I 82 is provided from which the thermostatic switches I88 are suspended. The mode of affixing the device into the switch is more fully described in my aforesaid copending application of which this is a division.

The switch is provided with a base plate I" which is secured to the plate I82 by screws I88. The plate is provided with pairs of legs I88 and I81 at opposite ends, each pair of which supports blocks I88 and I88 respectively. Each of the blocks is provided with axially aligned cylindrical bores I88 and I8I into which the ends of the thermostatic element I82 extend. The bores I88-Ill are sufliciently large to provide ample clearance space for the thermostatic element, and to permit the desired expansion thereof as hereinafter described, and yet serve as a guide and protector therefor.

At this point, for a better understanding of the invention, reference is made to Figs. 7 to 11 inclusive which illustrate in detail the thermostatic element. Generally, it comprises an insulated heater element which is disposed between a pair of nested cylindrical bi-metallic elements. The outer bi-metallic cylinder is split longitudinally and is provided with outwardly and longitudinally extending lips along the split edge which engage with and operate the switch.

More specifically. as can be seen in Figs. '1 and 11, the outer bi-metallic element is bent into the form of a cylinder I83 which is split at I88, being provided with a pair of downwardly extending flanges I88. A pair of guide pins I88 are provided on the upper end of the element opposite to the flanges I88, being adapted for guiding engagement with notches I81 in the plate I58.

The heater element comprises a narrow strip of insulating material I88 which is preferably of mica, about which is wound the resistance wire I88. The ends of the wire are secured to metallic clips or hands I18 as by spot welding. Lead wires "I are also connected to each of the clips I18. One end of the mica strip is provided with three apertures for the reception of hollow rivets I12 which hold the assembly together as later described.

The heater element is sandwiched between wide strips of mica I13. Fig. 9, of which there may be six. three being disposed on each side of the strip as shown in Fig. 10.

The mica strips I88 and I13 and the heater element I8 are all secured together by the rivets I12 which are inserted through the outer apertures I18, after which the assembly is rolled into cylindrical form and inserted through the outer bi-metal element I88. A second bi-metal element I88, Fig. 6, is inserted inside the rolled heater assembly, and a third rivet I18 is then inserted through the apertures I18 of the bimetal element and through the center aperture of the heater assembly (I18) to rivet the entire assembly together. When so assembled, the resistance, or heater element, is held in alignment with and between the bi-metal elements, and the wide strips of mica I18 extend beyond the ends providing ample rotection against short circuits. These ends are also the ends that extend into guiding relation with the bores I88I 8| of the blocks I88I88. The bi-metal elements are designed to expand when heated to open up the cylinder moving the flanges I88 apart, which movement effects the operation of the switch.

The flanges I88 are engaged by means. which movement thereof and thus etermines the length of time for which an overload must existbefore the switch is opened as well as to aiford a. snap action therefor. The flanges also engage a pair of levers which open the switch contacts.

As previously stated, the thermostatic element I88 is' disposed with its ends in the bores of the blocks I88 and I88 and with the pins I88 be nl guided by the notches I81 in the plate I88. The wires III of the heater element extend through notches I'I'l of the block I88 and are clamped therein by the clamp bar I18 which extends over the wires in the notches and is held in place by a screw I18 which is threaded into the block.

The means for controlling the time of operation of the switch and the operating levers. are supported on a block I88 which is secured to the lower ends of the blocks I88 and I88 by screws IN. This block (I88) is best shown in Figs. 12 to 14 inclusive.

As can best be seen in Fig. 12. the block is formed with a channel I82 which extends transversely across the block and in which is disposed a pair of slides (Figs. 15 and 16 and Figs. 17 and 18). These slides are disposed in the channel, one on top of the other in nested relation. The slide, Figs. 17 and 18, includes a flat base portion I88 adapted to rest on the bottom or the channel, and one end oi which is thickened at I88 to provide for lateral guiding engagement with the side of the channel. A pair of upwardly extending spaced tongues I81 are provided on the inter mediate portion which provides a kerf therebetween, the tongues being adapted for engagement on opposite sides of one of the flanges I88 of the bi-metal element. The remainder of the body at I88 is relatively thin and adapted to have seated thereon the other slide element (Figs. 15 and 16) which comprises a body portion I88. at one end of which is provided a pair of upwardly extending tongues I 8| disposed in spaced relation to each other and adapted to engage on opposite sides the other flange I88 of the bi-metal element. The slide I88 is adapted to seat on top of the thin portion I83 of the slide I88 in the channel I81, (see Figs. 13 and 14), and both slides are held in the channel by plates I88 that are secured to body I88 at the sides of the channel by screws I 88.

When so secured in place, the tongues I81 and I8I extend above the channel at even height to each other and are in position to engage the spaced flanges I88 of the bi-metal element.

Means is provided to hold the slides in position with the tongues I81-I 8i in properly spaced relation to each other and to restrict or resist the intial movement thereof by the bi-metal element, in the form of a spring detent mechanism which engages notches in the sides of the slide. As best shown in Figs. 16 and 18, the slide I88 is provided with a notch I88 and the slide I88 with a notch I88. These two notches are so positioned that when the slides are in a predetermined position, one on top of the other. the notches are in vertical alignment with each other. The plate I88 is provided with a boss I81 which extends from the side of the channel I82 to the left, as viewed in Fig. 12, to the edge of the plate. This boss is provided with a bore or channel I 88, the outer end of which is threaded, and a plunger I88 is dsposed in the inner end of the bore, being provided with a rounded end 288. The plunger is adapted to be pressed inwardly through the channel I82 with the rounded end 288 in simultaneous engagement with the notches NIB-I95, by a spring 20I. the spring 20I engages with the plunger and the other end with a screw 202 disposed in the threaded end of the bore. The pressure of the spring on the plunger is determined by the screw 202 which may be locked in adjusted position by the nut 203.

It will therefore be seen that the slides must overcome the effect of the p unger to force it out of the notches I95-I96 before they can move longitudinally in the channel I82, and that the pressure on the slides by the bi-metal element, necessary to disengage them from the plunger, is dependent upon the adjustment of the screw 202. Therefore, when the bi-metal element is heated, the cylinder starts to open up. The opening movement is restrained until the pressure by the bi-metal element upon the slides ISO-I85 is sufiicient to force the plunger out of the notches I95I 96. When this occurs, the resiliency of the bi-metal elements snap the slides quickly to the I limit of their movement in the outermost position. This thus provides a quick action for opening the contacts.

Inasmuch as the spring and detent mechanism restrain the movement of the sl des, and the slides in turn restrain the movement of the bi-metal element, the movements of the bi-metal elements are delayed, depending upon the pressure extended by the plunger in the slide notches. The time of operation may, therefore, be predetermined.

The flanges I65 engage between the ends of a pair of levers, which levers open the contacts. The base I80 is provided with a pin 205, disposed at the end of the base at the center line thereof, and upon which are disposed a pair of levers (Figs. 19-22 inclusive). Each of the levers comprises a body portion 206, which is apertured at 201, to fit over the pin 205. The levers are each provided with an offset arm 208 from the end of which rises a flange engaging portion or pin 209. The other end of each lever is provided with an upwardly extending pin 2I0 adapted for engagement with the contact carrying members. The two levers are adapted to be pivotally disposed on the pin 205, one on top ,of each other, as best shown in Figs. 1 and 6. The pins 209 and 2I0 of one lever are longer than those of the lever so that when they are disposed in assembled position, they rise to the same height. The flanges I65 of the bi-metal element extend between the pins 209 and are adapted to move the ends outward upon expansion of the element, and since the two levers cross each other, the ends 2I0 are likewise moved outward, scissors fashion, to open the contacts.

The contacts are supported by the block I58, Fig. 6, which is provided with outwardly projecting portion 2I2 having three vertically extending sots. The center slot 2 I3 receives therein the fixed contact assembly (Figs. 23 and 24) which comprises a pair of contact carrying strips One end of 2 that are spot welded to a member 2I5 on opposite sdes thereof and which extend downwardly and outwardly with the ends 2 I6 in spaced parallel relation to each other and carrying the outwardly facing contacts 2I1. The member 2I5 securely holds the assembly in place. The member 2I5 is also provided with a solder lug 222 The outer movable contact members, illus-' trated in Figs. 25 and 26, included the support member 225, which, like the member 2I5, has a serrated edge. A single contact carrying strip 226 is secured to the side of the member. This strip is provided with a double U shaped bend to provide flexibility thereto, the contact 221 being carried on the laterally extending end. Two of these members are provided and are each supported in the end slots, flanking the center contact, with the contacts 221 in contact with the fixed contacts 2I1. The ends of the strips 228 extend downward beyond the contacts at 228 and are disposed in engagement with the pins 2I0, whgh, as previously stated, extend between these en In operation, the heater element leads I1I may be connected into the circuitbeing controlled. In event an overload occurs, the heating of the resistance element I69 heats the bimetal' element causing it to expand and the flanges I65 to move outward. The movement of the flanges is restrained, however, by the slides I88 and I 90 which cannot move until the plunger I99 is moved out of the detents I-I96. The continued expansion of the strip produces greater pressure on the slides, by which time the bi-metal element has expanded to such an extent that when the slides are released, the bimetal elements spring to an open position snapping or quickl moving the slides to the limit of their movement. At the same time, the ends 209 of the levers 206 are quickly swung apart, which movement is transmitted to the end pins 2I0, and these in turn being in engagement with the ends 228, quickly disengage the contacts 221 and 2", The contacts remain in their open position until the bi-metal element cools and returns to its normal position depicted in the drawings and wherein the plunger again engages with the detents.

The plunger and detent mechanism also serve another purpose in that it holds the contacts closed and guards against accidental opening of the contact in event of shock or vibration.

It will be appreciated that the thermally responsive element, although shown and described as being particularly useful in operating the conment of the resistance type, it is quite within the purview of my invention to heat "the bi-metal element by other means; for instance, the heat could be supplied to the interior of the element by a rod of conducting material, or it could be heated by directing a current of fluid through the cylinder. 'Furthermore, it could be heated by applying radio frequency currents thereto in a manner well known to those versed in the art.

It will also be apparent that although 'only one pair of detents are shown for the slides which delay the operation of the bi-metal element. with this construction, additional detents can be provided on the slides which engage the elements when in the open position and hold the element against contraction until a predetermined amount of cooling takes place. Furthermore, although I have shown the-bi-metal elements as moving the operating flanges apart upon heating of the element, it is quite within the purview of my invention to provide an element wherein the flanges tend to close together upon heating, by simply forming the element in the opposite directions; that is, with the higher expansible metal on the outside insead of the inside of the cylinder.

It will be appreciated that although I have shown only one resistance element for heating the bi-metal element, it is within the scope of m invention to employ more than one resistance element. That is, the bi-metal element could have a resistance element disposed on the outside as well as the inside, or in the structure shown, the bi-metal element could have another resistance element disposed inside of it. These resistance elements could be connected in separate circuits if desired to cause the operation of the switch upon overload in any one of the circuits.

Having thus described my invention, I am aware that numerous and extensive departures may be mde therefrom without departing from the spirit or scope of my invention.

.1 claim:

1. A thermostatic switch, comprising a bimetal element formed into a cylinder or ring sp it longitudinally, and having a pair of outwardly extending flanges on the split portion, heater means for said element and supporting means engaging said element at a point diametrically opposite said longitudinal split and for supporting said element and leaving said flanges free for movement away from and toward each other upon changes in temperature of said element, lever means disposed for movement by said flanges and e ectrical switch contacts operable by said lever means,

2. A thermally responsive switch comprising a bi-metal strip bent into cylindrical form and adapted to expand circumferentially upon the application of heat thereto, means engaging the edges of said strip and movable thereby upon the expansion thereof including a pair of slidable members, each of said slidable members being operated by one of the edges of said strip at opposite ends of the strip adjustable detent means for engaging said slides and holding them against movement upon the expansion of said element to delay the movement of said slides and allow quick movement thereof upon a predetermined amount of expansion of said element.

3. A snap action thermostatic switch inc uding a bi-metal element bent into a cylindrical form spit longitudinally, the edges of said split portion being provided with operating flanges adapted to be moved relative to each other by changing the circumference of the cylinder upon a change in temperature, separate means, each engaging one of said flanges at opposite ends of said element and movable thereby, and means restraining said flange engaging means to hold said flanges in predetermined position until a predetermined pressure is exerted thereon by the changes in said cylinder.

4. A thermostatic switch comprising a pair of bimetal elements of cylindrical formation split longitudinally and disposed one inside the other, electrical heating means interposed between said elements adapted to be connected into an electrical circuit and to heat said elements according to the load in said circuit, at least one of said elements being provided with flanges along its split edges. a pair of slidable members, each of said members being engaged by one of said flanges at opposite ends of said element and adapted to be moved thereby upon expansion or contraction of said elements, restraining means for said slides to hold said slides against movement until a predetermined pressure is built up by said elements and releasable upon a predetermined increase in pressure to allow said slides and said flanges to move quickly.

5. A thermally responsive switch including a thermally responsive element formed of bi-metal strips bent into cylindrical form and disposed one inside of the other, a heater element disposed between said bi-metal elements and including a resistance means adapted to be connected into an electrical circuit and to provide an amount of heat which is a function of the load in said circuit, at least one of said elements being provided with flanges, means for engagement with said flanges comprising a pair of slidable members, detents formed in said slidable members and adjustable spring pressed plunger means for engagement in said detents to hold said slides against movement, said bi-metal elements upon being heated adapted to exert pressure tending to slide said slides and to slide said slides quickly after overcoming the restraining influence of said plungers in said detents, a pair of levers having one end engageable with said flanges on said bi-metal element, electrical contacts supported for engagement with the other end of said levers and operable to be opened by said levers upon movement thereof.

6. A thermostatically operated switch including a bimetal strip bent into cylindrical form adapted to expand circumferentially upon the application of heat thereto, means engaging the edges of said strip and movable thereby upon expansion thereof including a pair of slidable members, adjustable detent means for engaging said slides and holding them against movement upon expansion of said element to delay the movement of said slides and allow quick movement thereof upon a predetermined amount of expansion of said element, lever means operably connected to said slidable members, and electrical switch contacts operable by said lever means to be opened upon said quick movement of said slides.

7. A thermally responsive switch including a thermally responsive element formed of bimetal strips bent in cylindrical form and disposed one within the other, a heater element disposed between said bimetal elements, at least one of said bimetal elements being provided with flanges, supporting means for said elements engaging said elements at a point diametrically opposite said flanges, a pair of slidable members engaged by said flanges, detents formed in said slidable members and adjustable spring pressed plunger means for engagement in said detents to hold said slides against movement, said bimetal elements being adapted upon being heated to exert pressure tending to slide said slides and after overcoming the restraining influence of said plungers in said detents to slide said slidable members quickly, a pair of levers each having one end in operable engagement with one slide, a pair of fixed electrical contacts fixedly mounted on said support means, a pair of movable electrical contacts springably mounted on said support means normally in contact making engagement with said flxed contacts, the other end of said lever means in engagement with said 9 springable mounts of said contacts to quickly Number break said contact-making engagement 01' said 1,289,617 contacts upon the sliding of said slides. 1,677,710 MAX L. JEFFREY. 1,694,928 5 1,745,934 REFERENCES CITED 2,352,439 The following references are of record in the file of this potent. Number UNITED STATES PATENTS 10 131 3 3 Number Name Dnte 345,010 739,967 Wohl et a1. Sept. 29, 1903 440-413 Name Date Berry Dec. 31, 1918 Daniker July 17, 1928 Rider Dec. 11, 1928 Kauch et a1. Feb. 4, 1930 Landon June 27, 1944 FOREIGN PATENTS Country Date Switzerland Feb. 17. 1936 Great Britain Mar. 19. 1931 Great Britain Dec. 23, 1935

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