US2247902A - Thermal-responsive device - Google Patents

Description

G. F. BAHR 2,247,902

THERMAL-RESPONS IVE DEVI CE July 1, 1941'- Filed March 19, 1940 2| FwslLr-r MATERIAL IIIIIIIIII' V117 ATTORNEYS Patented .my 1, 1941 Um'reo STATE l TnEaMaL-acsrousxva mmol: Gustave F. Behr, Bridgeport, conn., manor .to

.Casco Products Corporation, Bridgeport-Conn., a corporation of Connecticut Application March 19, 1940, Serial No. 324,763

17 Claims. 20G-.142)

This invention relates to thermal-responsive devices, and, more particularly, to one which is adapted to be thermally and electrically connected to a heating element of an electrically heated appliance for controlling the circuit thereto in response to overheating of the heating element and current changes of the supply circuit.

The device of the present invention is particu- 'larly adapted for use with automatically con-L trolledcigar lighters of the type disclosed in my copending application, Serial No. 138,133, filed April 21, 1937, but the invention, in its broader aspects, is not limited to such a use.

It is an object o! the present invention to provide a device which will permanently open the supply circuit if the heating element of the appliance should attainsome dangerous lfheat `or if ashort circuitefshould occur such -cau's'e a dangerous heat to develop due to the resistance of any part of the circuit.

Thermal-responsive devices of the type disclosed by the present invention have generally included a fusible element, fusible within a range of temperatures above which it was not desired to have the device attain. The fusible elements heretofore proposed have generally been formed of wax or wax-like compositions or fusible metallic materials having a fusing or melting temperature below some predetermined one. The wax or wax-like compositions, of which many of the heretofore proposed fusible elements have been formed, were found not to be satisfactory under many conditions of use. for the reason that the wax or wax-like compositions would soften under prolonged heating at a temperature somewhat below that of their melting temperature and be no longer effective to perform its function in the device.

The metallic materials, although many were not affected by the prolonged temperatures substantially that of their fusing temperatures, nevertheless, have been dfiicult to use in devices controlling electric circuits, for the metallic materials oftentimes after they had fused or melted would come into contact and bridge spaced members forming a part of the circuit controlledl and would again complete the circuit or short ciry cuit the same.

The device of the present invention obviates the difllculties to be found in the previously proposed devices, for the fusible element of the present invention comprises a flat wafer-like mass of nonconducting composition having a definite known melting temperature housed within a casing formed of current-conducting material.

'I'he fusible element of the present invention preferably is formed of a material having a melting temperature below the temperature above which it is not desired to have the device attain.

The element should be formed of material which is vnot aifected when subjected to prolonged temperatures somewhat below its melting temperature and sulphur, as disclosed in the Russell D. Conboy application, Serial No. 322,698, filed March 7, 1940, serves admirably as the fusible material but other materials having similar I properties may be used. The casing housing the wafer-like mass of material, as it is current conducting, may be disposed so as to form a part of the circuit controlled and will, therefore, be

effective to control the circuit through cooperation with other elements of the device, the mechanical movement of which the fusible lelement fective to control the circuit to the heating elei ment should the latter attain a dangerous heat such as may occur if the supply circuit is allowed to remain closed for an undue length of time.

My device comprises, in its now preferred form, ra pair of spaced contacts with a movable contact tending to be urged by a spring to a position intermediate the "spaced contacts and out of engagement therewith, but which normally is held in good electrical engagement with one of said spaced contacts -by my fusible element which is engaged by the other of said spaced contacts. The melting or fusing of the element allows the 'spring to urge said movable contact to the position intermediate the spaced contacts and out of engagement with the contact hgainst which it had been held by the fusible element.

By forming the fusible element of a flat waferlike mass of fusible material, the device may be made relatively small so that it occupies verylittle space when assembled and mounted to the appliance.

In one form of the invention, the fusible element is accessible through a. removable closure forming a part of the casing housing my device. This permits the fusible element to be easily replaced without necessitating the removal of the'device from the appliance.

Other features and advantages will herein-- after appear.

In the accompanying drawing: Figure 1 is a sectional view of my device. Fig. 2 is a view similar to Fig. 1, but showing a modified form of my device and illustrating the position of the circuit-breaking members plurality of fingers having a plurality of fingers II bent inwardly thereof. ing a metallic stud I3, seats against the inner faces of the fingers I I and closes the one end of the sleeve I0. The stud I3 projects beyond the inner face of the disk I2 and the projecting portion is riveted over to form a head Il which clamps the disk I2 against a shoulder I5 on the stud I3.

A coil spring I6, seating on the disk I2, urges a metallic disk I `I to the left, as viewed in Fig. 1, and away from the head Il. The disll:y I1 is provided with a central concave portion forming a contact surface IIa projecting toward the head I 4 and receiving a cup-like member I8 held therein by any suitable means, but herein shown as having a friction fit within the concavity. The cup-like member may be of any suitable shape desired, but, as herein shown, the cuplike member, when assembled with the disk, forms a frusto-eonical plug projecting from the one face of the disk I`I. ripheral edge bent back to provide a flange 20 forming a guide surface slidably engaging a band 2I of insulating material fitted within the shell I and forming an insulated lining for the same. The other end of the shell I0 is closed by a disk 22, of insulating material received within the end of the shell III and held against.

the edge of the band 2| by a flanged ring 24 threadedly mounted to the shell Ill. The disk 22 carries a centrally located stud 23 provided at the inner end thereof with a spider member having a plurality of resilient fingers 25. The spider is secured to the inner face of the disk 22 by hitting over the end of the stud 23 to form a retaining head 26.

The stud 23 is provided with an integral stop collar 21 which engages the outer face of the disk 22 and cooperates with the head 26 of the stud to hold the disk 22 and spider against relative movement. I'he outer end of the stud 23 is threaded to take a nut or other securing device to clamp a contact clip, not shown. against the collar 21.

The spring I 6, as will be seen, will urge the disk I'I to the left, as viewed in Fig. 1, and out of engagement with the head I4 of the stud I3 which is internally threaded to permit its thermal and electrical attachment to the heating element of the appliance to which the device is to be used. To hold the'disk I'I in engagement with the head I4 against the action of the spring I6, I employ a fusible element which comprises a fiat wafer-like mass 28 of non- A disk I2 of insulating material, carry- The disk II has its pei conducting material meltable at a temperature below the temperature above which it is not desired that the device attain.

The wafer 28 is housed within a suitable casing 29 of some current-conducting material such as brass or the like. The fusible element is disposed between the resilient fingers 25 of the spider member and the substantially conical plug formed by the cup-like member I8 and is held against the plug by the resilient fingers 25. The resiliency of the fingers 25 is suiiicient to hold the element in good electrical engagement with the substantially conical nose of the plug and to urge the contact surface Ila against the head I4. The element is provided on the face engaged by the nose of the plug with a 30 projecting centrally of the same, but terminating just short of the center thereof. The fingers 30 preferably are formed, as clearly shown in Fig. 4, by stamping from the one face of the casing a substantially cruciform portion.

It will be seen that when the stud I3 is thermally and electrically conducted to the heating element, not shown, and the stud 23 is connected to the opposite side of the supply circuitI the circuit through the device will include the stud I3, head Il, contact surface I 1a, the plug I8, the conducting casing 29, fingers 25 and stud 23.

As the casing 25 of the fusible element forms a part of the circuit, a surge of current will cause the casing to become overheated due to the resistance offered. If the casing attains a temperature greater than the melting temperature of the fusible material, the same will melt or fuse and be no longer effective to support the fingers 30 against the spring urged plug I8. The coil spring I8 acting against the disk II carrying the plug I8 will cause the latter 'to partially pierce the fusible element, and this movement of the disk will cause a displacement of the head Il and the contact surface Ila to break the circuit at the point of engagement between the head Il and the contact surface IIa.

If the supply circuit should be held closed for an undue length of time, the likelihood of a dangerous condition arising, due to overheating of the element, will be completely obviated by the present invention. It will be seen, therefore, that if the heating element should attain some dangerous degree of heat, the stud I3 will conduct this heat to the metallic disk I 'I, plug I8, which, as previously explained, is in convtact with the one face of the fusible element.

The heat so conducted, if of a temperature higher than the melting temperature of the fusible material, will cause the same to fuse or melt and the nose of the plug I I again will be urged into the element as just above explained to break the electrical engagement of the contact surface I 'Ia and the head I l.

It will, therefore, be seen that the present device may be used to control the supply circuit of a heating element and will guard against the likelihood of a dangerous condition arising, due, either to a dangerous change of the current of the supply circuit or by the supply circuit being held closed for .a time sufficient to cause the heating element to attain a dangerous temperaure.

'I'he melting or fusing of the material 28, as it has no current-conducting properties, will not give rise to the condition which has arisen in some of the previously proposed devices of a similar nature, wherein the fusible material was itself current-conducting and caused a short circuit if, in fusing, it bridged spaced components of the circuit controlled.

In the form of the invention shown in Fig. 1, the fusible element, if destroyed, may be quickly replaced by a similar fresh one by merely removing the conductor, not shown, from the stud 23 and unscrewing the ring 2l which will permit the disk 22, carrying the stud 23 and spider member, to be removed rendering the destroyed cartridge accessible for removal and substitution of a new one.

In the form of the invention shown in Fig. 2, the device is substantially identical with that shown in Fig. 1 with the exception of the flanged ring 24 employed in the form of the invention shown in Fig. 1 to hold the parts in assembled relation. In the form of the invention illusi vmismos trated in Fig. 2, the flanged ring 2| has been dispensed with and the shell I! is provided with a plurality of ngers $2 at its end opposite to the fingers Il to hold the parts once assembled in 'that relation. The elimination of the flanged ring 2| does not permit a destroyed element to be readily replaced by a fresh one, and, in this form of the invention, it ls intended, once the element is destroyed, to replace the device having a destroyed element with an entirely new device.

Variations and modifications may be made within the scope of the invention and portions of the improvements may be used without others.

I claim:

1. In a device of the type described, a pair of spaced contacts; a movable contact; resilient means tending to dispose said movablcontact intermediate said spaced contacts and out of engagement therewith; and a fusible member in contact with one of said spaced contacts and interposed between the same and the movable contact, said fusible member comprising a quantity of fusible nonconducting material held within a housing of conducting material and holding said movable contact in engagement with the other of said spaced contacts.

2. In a device of the type described, a pair of spaced contacts, one of said contacts being re silient; a movable contact; resilient, means tend.

ing to hold said Irovable contactintermediate said spaced contacts and out ofv engagement therewith; and a fusible member engaged by said resilient contact and holding said movable contact in engagement with the other of said spaced contacts, said fusible member comprising a quantity of fusible nonconducting material held within a housing of conducting material. l 3. In a device of the type described, a pair of spaced contacts, one of said contacts being resilient; a movable contact; resilient means tending to hold said movable contact intermediate said spaced contacts and out of engagement therewith; and a fusible member being engaged by said resilient contact; and holding said movable contact in `engagement with the 'other of said spaced contacts, said fusible member com prising a flat wafer-like mass of nonconducting material held within a housing of conducting material.

4. In a device of the type described, a casing having a pair of opposite walls; a contact carried by each wall; a movable contact within the casing; a springlseated on one wall of the casing urging said movable contact .to a. position intermediate said first-named contacts and out of ensagement therewith; and a fusible member engaged by the contact carried by thewall opposite the wall seating said spring, said fusible member comprising a quantity of nonconductng material having a predetermined melting point held within a housing of conducting material and holding said movable contact in engagement with the other of said spaced contacts against the action of said Spring,

5. In a device of the type described, a pair ofl spaced contacts; a movable contact; resilient means tending to dispose said movable contact intermediate said spaced contacts and out of engagement therewith a fusible member vin contact with one of said spaced contacts, said fusible member comprising a quantity of fusible nonconducting material held Within a housing of conducting material and holding saidmovable contact in engagement with .the other of said spaced contacts; and means for connecting the verse walls of insulating material closing said last-named contact in current and heat-conduct?V ing relation to a heating element of an electri-f cally heated appliance.

6. In a thermal control device for an electrically heated device, a pair of spaced contacts; a movable contact; resilient means tending to dispose said movable contact intermediate said spaced contacts and out of engagement therewith; a fusible member in contact with one of connecting the same to said heating element and providing a direct heat path between the heating element and the fusible member.

'1. In a device of the type described, a pair ofJ spaced contactar one of said contactsbeing resilient; a movable contact; resilient means-'tending to dispose said movable contact intermediate said spaced contacts and out. of e agement therewith; and a fusible member engag by said resilient contact and holding said movable contact in engagement with the other of said spaced contacts, s aid movable contact comprising. a plug having the end thereof engaged by said fusible member of substantially conical shape. said fusible member comprising a quantity of nonconducting material meltable at a predetermined temperature held within a pierceable housing of conducting material, the melting of said nonconducting material allowing said resilient means to cause said plug to pierce said housing and be urged out of engagement with the spaced contact.

8. In a device of the type described, a pair of spaced contacts; a movable contact; resilient means tending to dispose said movable contact intermediate said spaced contacts and out of engagement therewithl; afusible member in contact with one ofsaid spaced contacts, said fusible member comprising a quantity of fusible nonconducting material held within a housing of conducting material and holding said movable contact in engagement with the other of said spaced contacts, the last-named contact including means for thermally and electrically connecting the device to a heating element of an electrically heated appliance, whereby said fusible member is subject to the heat of the heating element and heat caused by current changes of the supply circuit. Y 1

9. In a device of the type described, comprising an open ended casing; a pair of transends; a contact carried by eaich of said walls; a movable contact; resilient means tending to urge said movable contact to a position intermediate said spaced contacts and out of engagement therewith; a fusible member engaged by one of said spaced contacts,` said fusible member holding said movable contact in engagement with the other of said spaced contact and comprising a quantity of fusible nonconducting material held within a housing of conducting material; and a lining of Vinsulating material insulating said contacts and fusible member from said cas- 10. Ina device of the type described, a pair of spaced contacts; means for bridging said contacts comprising a movable contact normally disposed intermediate said spaced contacts and out of engagement therewith, and a fusible member in contact with one of said spaced contacts and holding said movable contact in engagement with the other of said spaced contacts, said fusible member comprising a quantity of fusible nonconducting material held within a housing of conducting material; and means for mounting said device to a heating element of an electrically heated appliance, said mount- 'ing means forming with said movable contact a direct heat path between the heating element and the fusible member.

l1. In a device of the type described, an open ended casing; a pair of transverse walls of insulating material closing said ends; a contact carried by each of said walls, one of said contacts comprising a plurality of resilient fingers projecting toward the opposite Wall; a movable contact; resilient means tending to urge said movable contact to a position intermediate the contacts carried by said Walls and out of engagement therewith; and a fusible member engaged by said resilient lingers and urged thereby into engagement with said movable contact, the resiliency of said fingers being sufficient to hold said movable contact in engagement with the other of said spaced contacts, the resilient means causing the movable contact to pierce said fusible member upon the fusing of the same whereby the movable contact is moved out of engagement with said spaced contact.

12. In a. device of the type described, an open ended casing; a pair of transverse walls of insulating material closing said ends; a contact carried by each of said walls; an intermediate transverse Wall; a plug carried by said intermediate wall; resilient means seating on one of said first-named walls urging said intermediate wall out of engagement with the contact carried by the wall upon which said resilient means is seated; and a fusible member disposed between the other of said spaced contacts and the plug carried by said intermediate wall for holding said Wall in electrical engagement with the other of said spaced contacts, said fusible membercomprising a quantity of fusible nonconducting material held within a housing of .conducting material.

13. In a device of the type described, a casing having a pair of opposite end closing walls; a contact carried by each Wall; a movable contact within the casing; a spring seated on one wall of the casing urging said movable contact to a position intermediate said first-named contacts and out of engagement therewith; a fusible member engaged by the contact carried by the wall opposite the Wall seating said spring, said fusible member comprising a quantity of nonconductingmaterial having a predetermined melting point held within a. housing of conducting material and holding said movable contact in engagement with the other of said spaced contacts against the action of said spring; and means removably secured to the casing for permitting access and removal of the wall carrying the contact engaged by the fusible member to permit a 'destroyed fusible member to be substituted with a fresh one.

14. In a device of the type described, an open ended casing; a pair of transverse walls of insulating material closing said ends; a contact carried by each of said walls; a current-conducting intermediate transverse wall; a plug oi' current-conducting material carried by said intermediate wall; resilient means seating on one of said first-named walls urging said intermediate wall out of. engagement with the contact carried by the wall upon which said resilient means is seated; a fusible member disposed between the other of said spaced contacts and the plug carried by said intermediate wall for holding said wall in electrical engagement with the other of said spaced contacts, said fusible member comprising a, quantity of fusible nonconducting material held within a housing of conducting material; and means for insulating said intermediate wall and the plug carried thereby from said casing.

l5. In a device of the type described, a casing having a transverse Wall of insulating material closing one end thereof; a removable transverse wall of insulating material closing the opposite end of said casing; a contact carried by each of said walls; a movable contact within the casing; resilient means tending to urge said movable contact to a position intermediate said wall contacts and out of engagement therewith; and a fusible member engaged by the contact carried by said removable wall holding said movable contact in engagement with the other of said wall contacts and comprising a quantity of fusible nonconducting material held within a housing of conducting material.

16. In a device of the type described, a. pair of spaced contacts; a movable contact; resilient means tending to hold said movable contact intermediate said spaced contacts and out of engagement therewith; and a fusible member in contact with one of said spaced contacts, said fusible member comprising a quantity of fusible material held within a thin walled housing of conducting material and holding said movable contact in engagement with the other of said spaced contacts, the fusible material reinforcing said housing and holding the same against collapse under the urging of said resilient means, the fusing of said material allowing said resilient means to collapse said housing whereupon the resilient means urges said movable contact out of engagement with the other of said spaced contacts.

17. In a device of the type described, a pair of spaced contacts; a movable contact; resilient means tending to hold said movable contact intermediate said spaced contacts and out of en-` gagement therewith; and a fusible member in contact with one of said spaced contacts, said fusible member comprising a quantity of fusible material held within a thin walled housing of lconducting material and holding said movable contact in engagement with the other of said spaced contacts, the Wall of said housing engaged by said movable contact being collapsible, the fusible material reinforcing said wall and holding the same against collapse under the urging of said resilient means, the fusing of said material allowing said resilient means to collapse said wall whereupon the resilient means urges said movable contact into said housing and out of engagement with the other of said spaced contacts.

GUSTAVE F. BAHR.

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