US2471925A - Thermal switch - Google Patents

Description

J. D. BOLESKY THERMAL SWITCH May 31, 1949.

Filed Dec. 23, 1944 FIG. I.

2 Sheets-Sheet 1 J. D. BLESKY THERMAL SWITCH May 3'1, 1949.

2 Sheets-Sheet 2 Filed Dec. 23, 1944 lPatented May-31,1949

THERMAL SWITCH John D. Bolesky, .mieten-0, Mass., miglior to' Metals `it Controls Corporation,

Attleboro,

Mass., a corporation of Massachusetts Application December z3, 1944, serial No. 569.467

17 Claims. -(Cl. 200-113) This invention relates to a combination switch and circuit breaker, and more particularly to a combination switch' and circuit breaker'which automatically trips out on overload in the electrical circuit and which automatically resets to circuit closing position upon resumption of normal current ow.

sponding parts throughout the several views of the drawings.

Among the various objects of the invention may be noted the provision of a combination switch and thermostatic circuit breaker in which there is accurate alignment of parts, and positive and reliable action of the switch elements of the circuit breaker; the provision of a circuit breaker which simultaneously and independently controls a plurality of circuits; the provision of a device of thev type indicated which may be manufactured inexpensively; the provision of rugged, perfectly balanced centralized driving means for manually moving the switch element to on o r oi positions; and the arrangement of means for positively locating the switch element in its several on and oil positions. Other-objects will be in part obvious and in part pointed out hereinafter.

The invention accordingly comprises the elements and combinations of elements, features of construction, and arrangement of parts which will be exemplied in the structures hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings, in which are illustrated several of various possible embodiments of the invention,

Fig. 1 is a plan of a blank for a thermostatic element for use in the switch of the present invention;

Fig. 2 is a plan of a modified blank for a thermostatic element;

Fig. 3 is an oblique plan of the switch driving element:

Fig. 4 is an oblique plan of a complementary part of the switch driving element of Fig. 3;

Fig. 5 is a section 0n line 5-.5 in Fig. 1v but showing the driving elements added;

Fig. 6 is a section on line 6--6 in Fig. 5;

Fig. 7 is a top plan of the combination switch and circuit breaker of the present invention;

Fig. 8 is a section on line 8--8 in Fig. 9;

Fig. 9 isa section on line 9--9 in Fig. 7

Fig. 10 isa section on line Ill- I0 in Fig. 9;

Fig. 11 is an enlarged section on line lI-II in Fig. 9; and,

Fig. 12 is a fragmentary detail plan view of a positioning member.

Similar reference characters indicate corre- The present invention is concerned with combination thermostatic circuit breakers and switches which utilize a composite metal thermal element to open the circuit upon overload and which will automatically close the circuit after the overload condition of the circuit has been remedied.

An overload current passing through a snapacting bimetallic switch element causes it to heat hereupon it will snap to circuit opening posi- The circuit breaker of the present invention is particularly adapted to automotive circuits, that is, for the headlights, tail lights, parking light, and so-called auxiliary circuits such as heater, dome light, radio, etc., each of which can be controlled and protected from a single circuit breaker-switch.

Ordinarily these circuits in an automobile are fed from the generator driven by the engine land are protected as a group from accidental overloads by a fuse. These accidental overloads may result from such causes as a crossed wire, short circuit or a faulty generator cutout while the engine'is running at high speeds.

The disadvantage of this arrangement is that should an overload blowtheffuse the entire electricalcircuit of the automobile is disrupted, causing the driver to collie to a precarious stop, especially at night, so that he may replace the burnt-out fuse. In the case of an inexperienced driver an accident of this nature is of some consequence and in any event may even necessitate a call for service should he be without additional fuses.

In the switch-circuit breaker shown herein, various circuits in the system may be controlled and protected separately. Also, should a vital circuit such as the headlights circuit experience an overload while driving at night the current would be interrupted only for a short period of time, and meanwhile a subsequent slowing down of the generator may remove the fault which would allow the thermostatic element to cool and return to circuit closing position, restoring' current to the headlights. In the case of overload in one of the circuits of lesser importance such as the dome light, radio, etc., the same sequence of events would occur, warning the driver that something is at fault and requires correction.

Referring now to the drawings, numeral I indicates in general a blank to be stamped from bimetallic thermostatic material. This stamping To the blank i is welded a three-pronged drivi ing hub 9, the three prongs il of which seat in notches lli between the leaf shapes 2, 3 and il. The driving hub 9 is centered on' the blank l while being welded thereto, by 'the use of an arbor through the central hole t in the blank and a similar hole l5 in the center of the driving hub. A further use of these holes't and l5 will be described'later. A three-cornered backing piece il is provided for the other surface of the blank i. It has the general shape of the hub region o the blank l with a center hole 2l and notches it for the prongs il. This backing piece lll and the driving hub s are provided with weiding spots or buttons 2t which are' thicker than the surrounding metal and directedtoward the metal to be joined so that when the blank l is sandwiched between the driving hub 9 and the backlng piece il the weld will be effected only at the small area of contact of thewelding spots 23 and the blank i. This tends to reduce the distribution of strains and stresses in the relatively thin bimetal blank. At the same time electricalcontacts 25, 2l and 29 may be welded to the blank l near the outer edges of the leaves 2, t and t respectively. This combined welding operation, which may be accomplished by the aid of a proper jig, reduces the manufacturing cost of this particular part or the circuit breaker. The entire assembly consisting of the contacts, the driving hub and the blank i may now be handled as a unit for any subsequent operations such as dishing, heat treating, etc. The leaves 2, t and @i are then dished to form automatically r'esettable snapacting thermostatlc disc portions of the type shown. in Spencer Patent 1,448,240. The resulting snap-acting thermostatic elements may be heat treated, calibrated, etc., and are then ready llor use. The dishing as well as the heat treatment and calibration of all the thermostatic elements may be done simultaneously. Fig. 6 shows the concavity imparted to the leai portions 2, 3 and ll of blank l in these subsequent operations for the purpose of imparting snapaction to the thermostatic elements. Thus the leaf portions 2, 3 and l are in effect joined together at a common point or region around the hole 5 in stress-isolated relation, i. e., stresses in any one portion are substantially independent of stresses in any other. Each portion is automatically resettable and retains this characteristic regardless of the condition of other portions.

Referring now to Fig. 9, there is shown at numeral 3i a pill-box base made of an electrical insulating material. The top closure 33 of the pill box is set in a shoulder S5 of the rim 31 of base 3i, extensions 39 of top 33 being held in slots il in rim 3l to prevent rotation. Top 33 is held to base 3l by` bolts 13. Rim 31 is thickened to form pads at the locations of bolts i3 thereby dividing base 3l into three peripheral regions t5, il and t9 for the accommodation of fixed electrical contacts. In region l5 there is imbedded in base :il a single double-duty elecf.

.trical contact 5i extending arcuately from end to end of the region and attached to a. terminal post 53 extending through base 3i and to the outside thereof. In region 41 there are imbedded two electric contacts G5 and El at either end thereof connected by a bridge piece 63 situated inwardly toward the middle of base 8l from the center-line of the contacts, forming a non-conducting space between said contacts, on the are of their centers. Contact 5l is attached to a terminal post E@ extending to the exterior of the base.

Region te contains two separated contacts t5 and el at either endv of the region, which are attached respectively to terminal posts t9 and il. Base 3i 'has a centrally located electrically Vconducting bearing. 'it for the rotary switch and thermostatic elements. Bearing it is attached to a terminal post l5 which extends to the exterior of the base.

Terminal connecting posts 53, 59, t9, li and l5 are all of the friction grip type. They are hollow lengths of tubing of a resilient material such as bronze, split throughout their length and pressed into an undersized hole in base 3l where they expand and are frictionally held. They are further held from rotation by ears 5t which exl tend from each side and seat in molded depressions in base 3l.' The contacts attached to each terminal on the top thereof may be welded or otherwise secured thereto. This form of construction resists vibration (no nuts to loosen), is economical and facilitates the assembly of the device.

Rotary contacts 2l and 2t attached to thermostatic elements 2, .Ts and il bear against and rotate around the arcuate centers of the various xed contacts imbedded in base 3l. They are held to this path by rotation upon a center stud lll, the head 'i9 of the stud being in frictional contact with the upper indented end of center bearing llt. Contacts 25, 2l and 29 are moved to the various switch positions by prongs il extending into notches 8l in the hub end 83 of a rotary switch shaft t5. Center stud ll is rigidly mounted in a center hole B3 in hub end @33. A manipulating knob''l is pinned to the outer end of the shaft B5. The knob is also of an electrical insulating material.

A three-armed resilient spring member B8 preferably made of spring bronze is also carried on hub t3 and is driven by prongs or keys B9 which are part of it (see Fig. 12) and extend into notches ti of.hub d3. The spring prongs 89 rest l on prongs il, thereby supporting member 88 in position. The outer ends of the three arms react against and traverse a series of depressions @l in cover 33. These depressions 9| are located on the radial centers of the three positions of the thermostatic elements 2, 3 and t in their rotation through the 55 arc between the pads for bolts it and resiliently hold the assembly in a xed position until the knob is manually turned.

The ends of the arms of spring member 88 are slit as shown at S3 (see Figs. 10 and 11) and an intermediate portion is shaped into a rounded bearing surface to fit smoothly into depressions @i so that while a rm frictional engagement is obtained with the stationary cover 33, a smooth movement from one location to another is effected. Spring 88 is limited in its rotary movement by the pads for bolts 43 in base ill. The three arms of spring 88 may move only through the extent of regions 45, 41 or 69, re-

are provided on cover 33 for attaching the device to the instrument panel of an automobile or p other convenienty location, only a single hole being required.

The use of the combination switch and circuit breaker of the present invention in an automotive electrical system will now be described. The present device may, however, be used in electrical systems of airplanes, radio communication systems and other installations wherein there are'a number of separate electrical devices to be operated which must be protected from overloads.

In Fig. 8, assuming that terminal is connected to one side of a source of power and terminals 53, 59, 59 and 1| are connected respectively to the heater, dome light, radio, horn, etc.; the tail lights; the parking lights; and thedriving lights; and thence to the other side of the source oi' power; thermostatic switch elements 2, 3 and 4 are shown dotted in a switch "off" position. It will be noted that contact 29 is between contacts 59 and 1| in region 49, that contact 21 is between contacts 55 and 51 in region 41 and cannot contact bridge 63 at any time, and that contact is in the center of the elongated double-duty contact 5| in region 45. In this position all circuits through the device are open except the one through the terminal 15, indented head 13, stud 11, thermostatic element 2, contact 25, contact 5| and terminal 53. This circuit would include the car heater, dome light, radio, horn, etc. Should an overload occur the thermostatic element 2 in the circuit will, because of its electrical resistance, heat suiiiciently to snap to its position of opposite curvature thereby opening the circuit at the contacts 25 and 5| and protecting from the damaging effects of a continued overload any of these devices that may be in operation at that time.

By turning knob 81 clockwise the thermostatic element 2 referred to, with its associated contact 25 will be moved to a different position on contact 5| but will still be in circuit to carry current to its connected devices. Contact 21 will move to contact 51 closing a circuit through terminal 15, bearing 13, head 19, thermostatic element 3, contact 21, contact 51 and terminal 59 to complete a circuit for the tail lights of the automobile. At the same time contact 29 will move from its off position onto contact 61 which will close a similar circuit through terminal 15, bearing 13, head 19, thermostatic element 4, contact 29, contact 61 to terminal 1| to complete a circuit for the parking lights of the automobile. The thermostatic elements 2, 3 and 4 in each of the above circuits will protect the several lights individually vand while one set of lights may be turned oi by a fault effecting snapping of its thermostatic element. the other set of lights will not necessarily be affected.

Turning knob 81 counterclockwise from its "off position (see Fig. 8), contact 25 will move t0 still another position on elongated contact 5| but the circuit through it remains closed. Contact 21 on element 3 will move to contact 55 where it will close a circuit through terminal 15, bearing 13, head 19, thermostatic element 3, contact 21, contact and across bridge 63 to terminal 59. This will complete a circuit again for the tail lights. Contact 29 will move onto contact 55 and complete a circuit through terminal 15, bearing 13, head 19, thermostatic element 4, contact 29, contact 65 and out through terminal 69 complating a circuit for the driving lights oi' the automobile. Thus it will be seen that in each individual circuit a protective thermostatic element is included upon closing each circuit and remains on guard while the circuit is closed.

The device of the present invention represents not only a protective circuit breaker for the protection of aplurality ofcircuits, but is a compact and emicient switch. The indentations 9| in cooperation with the portions of member 33 position the switch accurately and positively. By locating the indentations 9| opposite the desired stopping places for the'contact carrying thermostatic elements 2, 3 and 4, movable contacts 25, 21 and 29 are accurately positioned in the three places desired. The spring character of member I9 and the conilguration of projections 95 and indentations 9| facilitate the accurate positioning of the parts.

It will be seen that the invention provides a combination switch and circuit breaker oi' very compact form, and that by means of a few inexpensive parts there has been devised in one unit protection for a number of electrical circuits.

In view ofthe above. it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As many changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim: l

1. A thermostatic element for the protection oi a plurality oi circuits comprising a plurality of automatically resettable snap-acting thermostatic plates, a rigid mounting, said plates being joined together at said mounting in stress-isolated relation so that stresses in any one plate are substantially independent of stresses in any other plate,l whereby any one plate retains its automatic reset characteristic regardless of the condition of any other plate.

2. A thermostatic element for the protection of y a plurality of circuits comprising a plurality of automatically resettable snap-acting thermostatic plates, a rigid mounting, said plates being joined together at said mounting in stress-isolated relation so that stresses in any one plate are substantially independent of stresses in any other plate, whereby any one plate retains its automatic reset characteristic regardless of the condition of any other plate, a contact on each plate remote from said point mounting, and means for pivoting said thermostatic element at said mounting.

3. A thermostatic element for the protection of three circuits comprising three snap-acting automatically resettable thermostatic discs, a rigid mounting, said discs being joined together at said mounting and symmetrically arranged around said mounting, a contact on each disc remote from said mounting, and means for pivoting said element at said mounting.

which common point constitutes a current terminal.

5. A combination switch and circuit breaker comprising a plurality of stationary contacts, a plurality of movable contacts, snap-acting thermostatic means mounting said movable contacts, and. means for manually moving said movable contacts into and out of engagement with said stationary contacts, 'said snap-acting thermostatic means comprising independent automatically resettable snap-acting thermostats mounted in stress-isolated relation at a common point, which common point constitutes a current terA minal, and control means operated simultane ously by said manual means for positioning said thermostatlc means and bringing said movable contacts into and out of engagement with said stationary contacts.

6. A combination switch and circuit breaker comprising a plurality of snap-acting automatically resettable thermostatic discs attached to a common member in stress-isolated relation, sta= tionary contacts, movable contacts carried by said discs, a manipulating member for moving said discs to bring said movable contacts into and out of engagement with said stationary contacts, and a control member for predeterminately position ing said discs in a plurality of positions.

'7. A thermostatic element for the protection of three circuits comprising three automatically resettable dished thermostatic discs, a rigid mounting, said discs being joined together at said mounting, and symmetrically arranged around "said mounting, a contact on each disc remote trom said mounting and means for supporting said element at said mounting.

d. A combination switch and circuit breaker comprising three automatically resettable dished thermostatic discs joined together at a common point and symmetrically arranged around said common point, means for mounting said discs at said common point, a contact on each disc at a point remote from said common point, three sta tionary contacts, a base on which said discs and said stationary contacts are mounted, means engaging said discs for moving the contacts thereon into and out of engagement with said stationary contacts, detent means operating on said engaging means to hold said engaging means in one or a plurality of predetermined positions and aid.-v ing said engaging means to enter and leave said predetermined position, and manual means i'or moving said engaging means.

9. A combination switch and circuit breaker comprising a switch box having a feeder contact, a manually operable switch post including an end conducting part engaging said feeder contact, a multi-limbed thermostatic element in conductive rotation with said conducting end part, each limb being formed as an automatically, resettable thermostatic plate, and `radial spring detent means extending vfrom said post, said box having a detent surface engageable by said spring means to determine "on and oii" positions of thevv switch, said spring means being adapted to bias' the post to eect electrical contact between said conducting end part and the feeder contact.

l0. A combination switch and'circuit breaker comprising a switch box having a feeder contact and distribution contacts, a manually operable switch post including a conducting end part engaging said feeder contact, a multi-limbed thermcstatic element in conductive relation with said conducting end, each limb being formed as an automatically resettable snap-acting thermolil dit

dit

static plate, and multi-limbed radial spring de tent means extending from said post, said box having a datent suria'ce engageable by said spring means to determine on" and oiP' positions of the switch, said spring means being adapted to bias the post to effect electrical contact between said conducting end part and the feeder contact.

il. A combination switch and circuit breaker comprising a switch box having a feeder contact, a manually operable switch post including a conducting part engaging said feeder contact, a thermostatic limb element in conductive relation with said conducting part, said limb element being formed as an automatically resettable thermostatic plate, detent rotary means associated with said post to determine rotary on and off positions oi the switch, said spring means being adapted to bias the post so as to effect electrical contact between said conducting end and the ieeder contact, said plate being movable thermo-1 staticallyto "on and "oil positions when the switch is in rotary on position.

l2. In a thermostatlc switch construction, a thermostatic plate having a plurality of leaves centrally joined, notches in the plate between the leaves, a hub consisting of a piece on one side of the plate coordinately notched and a piece on the other side of the plate having axial prongs coordinating with coordinated pairs of the notches.

13. In a thermostatic switch construction, a thermostatic plate having a plurality oi' leaves centrally joined, notches in the plate between the leaves, a hub consisting of a piece on one side oi the plate coordinately notched and a piece on the other side of the plate having axial prongs coordinating with coordinated pairs of the notches, said pieces being welded to the plate at regions which prior to welding were made locally thicker on said pieces adjacent the plate.

lt. In a thermostatic switch construction, a single thermostatic plate having a plurality of leaves centrally joined, notches in the plate between the leaves, a hub consisting of a piece on one side of the plate coordinately notched and a piece on the other side of the plate having axial prongs coordinating with coordinated pairs of the notches, said pieces being welded to opposite sides of the plate, and a grooved control post adapted axially to receive said prongs.

l5. In a thermostatic switch construction, a

single thermostatic plate having a plurality of leaves centrally joined, notches in the plate between the leaves, a hub consisting of a piece on' one side of the plate coordinately notched and a piece on the other side of the plate having axial prongs coordinating with coordinated pairs of the notches, said pieces being joined to opposite sides of the plate, a grooved control post adapted axially to receive said prongs, a detent member having key means cooperating with said grooves at their ends and held by said prongs, said post having an axial hole and said plate an aligned opening, and a conducting member passing through said opening into said hole to hold in as-la sembly the post, plate and datent means.

16. A thermostatic element for the protection of a plurality oi circuits, comprising a plurality of snap-acting thermostatic plates each of which is calibrated to protect a circuit, a rigid mount ing, said plates being joined together at said rigid mounting in stress-isolated relation so that stresses in any one plate are substantially inde-f pendent of stresses in any other plate, whereby anyone plate retains the calibration on which the protection of its circuit depends, regardless of the condition of any other plate.` Y 'l 17. A combination switch and circuit-breaker comprisix'ig a plurality ot stationary contacts, a

plurality of movable contacts, snap-acting thermostatic means mounting said movable contacts, and means for moving said movable contacts into and out of engagementwith said stationary conv tacts. a rigid mounting', said snap-acting thermo- 1o static means comprising independent Asnap-acting thermostatic platesmounted in streasLisolated relation at said rigid mounting. which mounting constitutes a current terminal.

JOHN D. u

A v1ol REFERENCES CITED The following references are of'record in the Y' ille of this'patent:`

Number UNITED STATES PATENTS Boles'ky Aug. 24, 1943

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