US2538574A - Protective device - Google Patents

Description

Jan. 16, 1951 E. KOLISCH 2,533,574

PROTECTIVE DEVICE Filed Aug. 18. 1948 2 Sheets-Sheet 2 5. 1 TEF- lNVENTpR Emil ,Kol zsck ATTOR EYS Patented Jan. 16, 1 951 UNITED STATES PATENT OFFI Application August 18, 1948, s er iai;No.44,.845

24 Claims.

jing-appliance of the above type which device ;is "of simple, relatively inexpensive, compact and tugged construction, which tunctions with a minimum number of operating partsunone of which is delicate or apt to become out of order,

'which deyic'e does not, detract from the normal -operati'on of the appliance, which is not exposed to contact-with the materials to be heated by the appliance and which yet'may tie-completely concealed from the exterior of theappliance, which functions without appreciable arcing both in {maintaining the circuit in 'use and in lnterrupta ing'the circuit upon overheatingas for instance in the absence of desired liquid. therein, which admits of beingiinstantly, uner-ringly and automatically, restoredito operativeness'by mesort to. a-simplecontrol manipulation on the. pal-t of the-unskilled user suchas by: the of a knob. accessible. front the exterior of the appli'ance and without the need for-.anyidisassembly tools. or for reaching into interior of the device.

It is: another object of the invention to pro.- F

wide. a multiple fusible. linkprotective: device of the; above. type, by which. a. uniformly efiectiue electricalvcontactwith respectto one otthezfiisible links. is assured; even; in the absence oi. close tolerancesin manufacture: or' assembly, by which the; break of the circuit; upon softening of such tusiblelink under excessive heatis sharply and automatically eflfected by a snap; action and. by

which the connection of a fresh fusible link: is

.efiected. by automatically snapping. such tresh into: place underuthevmanual control otthe user...

.. Itgis, a feature .0! the.inventionuto provide1a plurality of. fusible; links; of which one only is maintained in. operative position where'it issub.

.iected the. heat. evolved in: the: appliancef the nemaini-ng fusible links being in reserve. for ready mlacement: upon insingyand ru tureof the link in 'llSflrlHlQflfi excessive; heat; To this end the .tusiblel link. a tion: is en a ement w t a '2 stop or contact in effective heat conducting and circuit closing relationship with the heating element of the appliance. Spring drive means, re siiient.y arrested. by the engagement of the link and stop are efiective to break through the link by a snap action upon softening of the latter by overheating; thereby tobreak the circuit. The circuit is restored at will by manual control to effect engagement of the next link with the Stop. In a preferred embodiment the links are carried on amovable, preferably a rotary mount and the stop is rigidly and immovably mounted to ar-' rest said mount which is under the sustained influence of a stressed resilient drive, eifec'ztivef: to snap through the link when it softens and propel the mount in direction to bring the ,neXt link into resilient arresting engagement with the immovable stop. Releasable means 1s provided preferably in the form of a pawl functioning uponrupture of a link toarrest the spring driven mount. before the next link reaches the immovable stop, thereby to assure that the circuit re.- mains open until the releasable means has been displaced. as by manually turning aknob accessibl'e from the bottom of the device.

In. a preferred construction, the fusible links radiate from a rotatable mount which desirably rises from the bottom oi the device and stressed resilient means are provided associated with the mount to urge the latter to rotate inone direc.y .tion, while the immovable stop is afiixed above the links the path of movement thereof. it releasable: pawl is preferably provided, coacting with. the rotatable mount to retain the links thereon spaced from said stop after the fusible link. in. actionv has ruptured, thereby ensuring that the circuit will. remain open, and a trigger is: provided controlled by said knob to actuate said releasable": pawl to enablesaid mount to rotate under-the urging of said stressed resilient means to bring the next intoengagement with said stop, so that positive electric contact will be madeto close the circuit".

This application is a continuation impart of my co-perrdi-ng' applications Serial No. '76716'98' Fig. 3 is a fragmentary longitudinal cross-sectional View taken along line 3-3 or "big. 1,

Fig. 4 is a fragmentary transverse cross-sectional view taken along line 4-4 of Fig. 1,

Fig. 5 shows a fragmentary plan view of the mount after a link has ruptured.

liig. 6 is a fragmentary bottom view of the appliance taken along line 6-45 of Fig. 1,

Fig. 7 is a bottom plan view of the heater housing,

Fig. 8 is a fragmentary perspective view of the device showing one of the link mounts, and

Fig. 9 is a fragmentary longitudinal crosssectional view of another embodiment of the device.

Referring now to the drawings there is shown a preferred embodiment of the protective device as applied to a coffee percolator H1. The latter comprises a container aifixed as by welding as at I2, to a hollow base 13 which has an annular flange M at the bottom thereof affixed to the bottom rim l5 of the base as by rivets IS. A bottom plate I1 is afiixed to said flange M by means of screws l8 which also mount legs l9 and which pass through the bottom plate I1 and are threaded into corresponding openings 2| in the flange l4.

Carried by the top 25 of the base l3 and extending through an opening therein is a generally cylindrical, preferably ceramic mount 21. A cylindrical protective housing28 encompasses the main length of the mount which protrudes above top 25 and has an inturned rim 29 extending under diametrically opposed laterally extending ears 3| integral with the mount 21. To permit assembly of the housing 28 to the mount, the rim 29 may have diametrically opposed s;ots 32 to accommodate said ears 3| so that upon slight rotation of the housing 28, after introduction of the cars into the slots 32, the housing is attached'relative to the mount. A nut 33 secured upon the threaded base 34 of the mount 21 causes the ears 3| to be pressed against the inturned rim 29 of the housing, rigidly to clamp the housing and the mount to the base.

' A high resistance wire 35 is wound around the main length 36 of the mount 21 which is of slightly reduced diameterforming an annular ledge 31. One end 38 of the wire is connected to the head of a bolt 39 which extends through a bore 4| in the ledge 31 and the base 34 of the mount 21, and protrudes from the bottom of the mount as at 42, being retained therein by a nut 43. The other end 44 of the resistance wire 35 passes through a bore 45 in the ledge 31 and base 34 and extends from the bottom of the mount as at 46and is connected by a lead 41 to a terminal plug 48 rigidly affixed to the wall of the base I3 and insulated therefrom by insulating washers 49, as is the companion terminal plug 5|.

The protective device disposed within the hollow base l3 establishes an electric circuit from the two ends 38 and 44 of the heating coil to the two terminals 48 and 5|, respectively. The device includes a plurality of fusible links 54, each carried by a corresponding support 55. An electrical contact closes circuit to one only of said links. The rupture of the fusible link under excessive heat results in automatic interruption of the electric circuit, preferably under release of stress resiliently imposed. The contact and the fusible links are then relatively displaceable so that upon manual trigger action thecircuit is automatically snapped closed with another link in operative position. It is, of course, not neces- 4 sary that the entire length of the link be of fusible material but only a portion thereof need be in order to break the circuit when such fusible portion ruptures.

The embodiment of the protective device herein chosen to illustrate my invention comprises a substantially L-shaped bracket 58 of heat conducting material such as sheet metal having its transverse arm 58 extending at substantially right angles to downwardly extending stop or contact finger 59, and afiixed to the bottom end 42 of bolt 39 by nut 43, as shown in Fig. 3.

Mounted within the base |3 on the upper face 1| of a substantially circular flat domed portion 12 formed in the bottom plate i1, is a substantially U-shaped bracket 14, having laterally extending arms which are affixed to face 1| by rivets 16. Extending through an opening 11 (see Fig. 3), in the cross piece 18 of bracket 14, and through an axial opening 19 in the face 1| of i the bottom plate H, is a shaft 8| having a flange 82 integral therewith andseated on the cross piece 18. A collar 83 is affixed on shaft 8| beneath cross piece 18 by a set screw 84 securely, yet rotatably to support the shaft on bracket 14. The lower end of shaft 8| extending through opening 19 has a crown cap 69 affixed thereon by set screw 18,.the cap having a pointer on the periphery thereof which coacts with a dial face 13 to indicate the setting of the shaft.

Carried on the shaft 8| is a mount comprising a disc 85 of insulating material mounted at its axis on the upper part 86 of shaft 8|, as is a generally circular metal contact plate 81 positioned on said disc 85 andwhich has a hub 88 of insulating material through which said upper part 86 extends. a a Plate '81 has a plurality of radiating slots 90 therethrough, illustratively six in number, through each of which extend the arms 89 of the substantially L-shaped bracket or support 55, base 92 of which extends at right angles to arms 89 and is sandwiched between disc 85 and plate .81, and .in electrical contact with the latter. .By means of a nut 93 threaded on the end 86 of shaft 8|, the plate and disc are tightly clamped together against flange .82, thereby rigidly clamp..- ing the bases 92 of supports 55 therebetween, securely to retain arms 89 in upright position. 1.

The upper ends of each pair of arms 89 are bent over a fusible link 54 securely to hold the latter parallel to and radially of the plate 81 and aligned withthe contact finger 59, so that when the mount is rotated in the manner hereinafter described, the links will successively abut thereagainst. A tensed coil spring 63 isprovided; encompassing shaft 8| between collar 83 and face ll of bottom plate l1. One end 64 of coil spring 63 is positioned in a transverse. slot' 65 in shaft 8| and the other end'EB of the coil spring is secured to a bolt 61 held in place on cross piece"18 by nut 68, thereby normally urging shaft 8| and the mount80 to rotate in acounterclockwise'dF 'rection. In order to limit the rot ationof mount 80 an L-shapedbracket 93 is provided also affixed on face 1|, the upstanding arm 99 of which has aflixed theretoan insulating block lo], the latter carries a laterally extending contact arm I82 afilxed thereon by screws I03 electrically connected by lead' I01 to terminal 5|.' Arm I02 "is 'of spring metal resiliently urged for electrical con tact at its' free inturn'ed or toe "end |04;with the rim of contact p1ate'81. 'contactplat'e 81 is provided Withia plurality of emer encieseegme i?! respectively with the radiating links 54;

g'z'e them herd? the biiiiit is broken b? we mpmreo r the iiqk n e serative pdsitibm 7 ho that the device is not 'o"p"= "tile ii'lbimt an t6 bi'ih'g the i159 exeebt the "c t 1151 w s p m hed, however whentne k'nebes is tur din e1 er a clockwise or couhtei clqk s 1186i will have i'eady incl-ieatibn that a new 11-iik ti} respect t? is in "cirefiit by ieasgn of the fact that cap 58 tfii'ne'fi win fame with shaft 81' to indicate the i hummer on the and 13. It is nope noted that as C611 s ring 6315-111 highly'tfised condition the link will exei't considerable pressure against the step fig'er thereby e'ri'suii'n'g that a p'os itiile bents-et jwm be ma e betwee thelirlk 5'4 and. the f stupfihgerm th'atwillifiotjalr loose. i Thus 'by the "device heieinibove described, ail e b'idte we "'diiide is provided may; win positively break the ci'r'guit in the event of a'rfl awn-eating, yet 'ea'f1fqflidkly "and simply be aii I jufsted mfreswre the appliufitie to o"p'er'aitiye 01m 1 tli tidfi Withbutflfe 'Iieed 'fOi special skill 61 afii} to'bls. I Wei e 'th effusible 'liiik engaging stb'f) hinged "21nd the 'rota'ry fusible link mb'unt to e L manually propelled for placing in circuit the hiit ii'n'k "arte'iaffusibleflifik had been 'rii'btuied by the aetion of "sud-h st'op,'t'01e1an'ces would. belie- "quired ll; the m'anufadture andassembly offthe palitfs 'Ijhe effectivenes of the fuse lihkiuptiir; ing' d fiis 'lihk'e'ngaglng a'tidn would depend p'r eftor ra'tkfer than on a,spring dr i irte 931d the bpeiating mu-1d accordingly not be as uniformly dependable.

Wl'1'e' ""anfthe fusible links have been melteii, it is '"aielativelysiniple matter to retrieve the 100mm 1 by unloosening screws 18. The e'iitif' u'iiit 6r 80 can 'then'be replaced by 'm't bi the "plate-81 c'a'ii be rembved "fr'o'fn LT 8 by- 1'nioving n'tlit 93 Wher'eupbn the link ie' 7 iejrr n' fsuppdrts "a n be Withdrawn from *s'ldt's e'pl'ac'ed.

th I

sir ti'oh, 52 of tiig g r 62 will press 7. of stop or contact finger 59' the lower end H3 of which is in the path of movement of the fusiblelinks. In order electrically to insulate the stop finger 59' from the bracket 56' yet provide for effective heat transfer therebetween, a mica insulating strip H4 is positioned between arm Ill and end 2 of the stop finger, the character of mica being such as to provide an effective electrical insulation yet permit rapid transfer of heat. To retain the stop finger and mica strip against arm Ill, aligned openings H5 are provided through the ar lll, mica strip ll 4 and end H2. A centering grommet IIB of insulating material is positioned in each of the opening in end H2 and by means of a rivet II! which extends through grommet HS, mica strip IM and arm II I, the aforementioned elements are rigidly clamped together.

In order to provide an electric path from the heating element to the stop finger 59' a connect ing strip H8 is provided, one end H9 of which is affixed to the stop finger by rivet l2l and the other end 122 of which has an opening therethrough through which end 12 of bolt 3% ct tends, the end being secured on said bolt by nut 43. 7

As the arm 58 of bracket 56' is in close proximit to the top ofthe base and to the heating element it is readily apparent that if any excessive heat should develop, this heat would quickly be transmitted through the stop or contact finger 5 9 to fusible link 54' and cause the latter to soften and thereupon rupture to break the circuit. It is also readil apparent that such heat transfer could occurmore quickly with the above construction than when the bracket 56 is connected only to end 42 of bolt 39 as in Fig. l which is spaced some distance from top 25 and the heating element.

' A many changes could be made in the above construction, and many apparently widely different embodiments of this invention could be made without departing from the scope of the claims, it is intended that all matter contained in the above description or shown in the accom panying drawings shall be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, what I claim as new and desire to secure b Letters Patent of the United States is:

l. A protective device for electric heating appliances, said devic comprising a mount having a plurality of fusible links radiall arranged thereon, a contact stop of heat conducting material in the substantially circular path of said links engaged by one'of said links and effecting circuit closure through said mount, means upon softening of the engaged link to rupture the latter, thereby to disengage said link from said con tact stop and break the circuit, and means to effect relative movement of the stop and the next fusible link for engagement thereof. I

2. A protective device for electric heating appliances, said device comprising a mount having a *plurality of supports thereon, a fusible link carried by each of said supports and extending radially of said mount, a contact stop of heat conducting material in the substantially circular path of said links engaged by one of said links and maintaining the corresponding support in circuit, means upon softening of the engaged link to rupture the latter, thereby to disengage said link from said contact stop and break the circuit, and means after rupture of the engaged link to effect relative movement of the contact stop and the next fusible link for engagement thereof.

3. A protective device for electric heating appliances, said device comprising a mount having a plurality of supports thereon, a fusible link carried b each of said supports and extending.

radially of said mount, a contact stop of heat conducting material engaged by one of said links and maintaining the corresponding support in circuit, means to maintain a pressure at substan tially right angles against the engaged link whereb upon weakening of the said link, the contact stop'will rupture th latter to break the circuit, and means after rupture of said engaged link to bring the next fusible link into engagement with said contact stop.

4. The combination set forth in claim 3 in which said last named means are resilient and normally urge said mount to rotate in one direc-' tion.

5. The combination set forth in claim 4, in which means are provided coacting with said mount to limit the rotation thereof.

6. A protective device for electric heating appliances, said device comprising a mount having a plurality of supports thereon, a fusible link carried by eachof said supports and extending radially of said mount, a contact stop engaged, by one of said links and maintaining the corresponding support in circuit, meansto maintain a pressure of the engaged link against the contact the next fusible link into engagement with said metal contact plate rigid with said disc and ha'vcontact stop.

7. In an electrical device of the type having a heating element; the combination therewith of a rotatable insulating disc, a generally circular ing a plurality of radiating slots therein,a plurality of brackets clamped between said disc and said plate and extending respectively through said slots, a fusible link at the extending end of each of said brackets, a contact finger of heat conducting metal in electrical circuit with said heating element and in the path of rotation "of said fusible links, and means to rotate said disc and said plate, thereby successively to bring each of said links into contact with said contact finger; 8. The combination set forth in claim '7, in which means are provided, resiliently urged against the rim of said metal plate to make contact therewith.

9. A re-settable protective device for electric heating appliances, said device comprising a rotatable mount, a plurality of supports rigid with said mount, a fusible link carried by each of said supports and extending radially of said mount, a contact finger of heat conducting material engaged by one of said links and maintaining the corresponding support in circuit, stressed resilient means normally urging said mount to rotate in one direction and forcin said link against said finger whereby upon weakening of the engaged link, the stressed mount will r0; tate to rupture said link, thereby to open the cir-v cuit.

10. The combination set forth in claim 9 in which means are provided to retain said circuit in open condition after said link has ruptured.

11. In an electrical appliance of the type having a base, a bottom plate, a heating element atfixed to the top of said base and terminal plugs 9 ter connecting a soureeor 'eurrentto saidheating "element; the combination therewith of a protective device therefor, said device comprising an in- 's'ulating disc rotatably mounted on said bottom piste, a generally circular contact making ele- "mentrigid' with said disc and rotatable therewith, a plurality of brackets rigid with said disc and contact element and rising therefrom, a fusible link affixed-to the nee endof each of said brackets a contact finger-electrically connected to one-end said heatin element and depending Jr'o'mthe top of said base in the path of move- Jmcnt cf said fusible links, and a contact arm electrically connected at one end to one of said plugs and having its free end resilientlyurged against the rim ofsaid contact element to make contact 1-2. In an electrical appliance of the type comprising-abase, a bottom plate affixed-thereto, a heating element aflixed to the top of said base and terminal plugs for connecting a'sourc'e of current to said heating element; the combina- -tion therewith of a protective device therefor, said device comprising an insulating disc, a generally circular contact making plate affixed to said disc and having a plurality of radiating slots therein, a shaft rigid with said disc and passing through said bottom plate for rotatably mountin'g said disc and said contact plate, a resilient arm on said bottom -p'late coacting at one end -iwith said contact plate to limit the rotation thereof and electrically connected at. thewoth'er end to one of said terminal plugs, a plurality of substantially L -shaped brackets clamped between said disc andsaid contact plate and respectively rising upwardly through the slots in said contact plate, a fusible link affixed to the free end of each of said brackets, and a contact finger connected to one end of said heating element and depending from the top of said base in the path of movement of said fusible links successively to engage the latter as said disc and said carrier ar rotated.

13. The .combinationsetforth in claim 12, in

which said contact plate has a plurality of ratchet teeth on the rim thereof and said-re silient arm has a-pawl-at the end thereof adapted 'to' engage said ratchetteeth to limit .therotation of said contactplate.

"' '14. The combinationset forth in claim 1 2, in

' supports, a contact finger of heat conducting material in the path of rotation of said links, engaged by one of said links and maintaining the corresponding support in circuit, stressed resilient means urging said disc to rotate and forcing said link against said finger, whereby upon weakening of the engaged link, the latter will be ruptured, means effective upon such rupture to retain said contactfinger spaced from the next link, and means effective upon release of the latter means to bring said next link into engagement with said contact finger.

16. A resettable protective device for electric heating appliances, said device comprising a rotatable insulating disc, a generally circular contact making element affixed to said disc, a plurality of supports rigid'with said element and said disc and rotatable therewith, a fusible link at the end of each of said supports, a contact of heat conducting material in the path of move- :ment of said links, engaged by one of said links and maintaining the corresponding support in circuit, stressed resilientmeans normally urging said mount to rotate in one direction and forcing said last named link against said contact whereby, upon weakening of the engaged link, the. stressed mount will rotate to rupture said link, thereby to open the circuit, means coacting with said contact making element to limit the rotation of said mount and maintain said circuit in open. condition, and means coacting with said last named means to permit further rotation of saidmount to bring the next link into engagement with-said contact and close said circuit.

"-17. In an electrical device of the type having a heating element; the combination therewith of a rotatable insulating disc, a generally circular -metal contact plate rigid with said disc and hav ing a plurality of radiating slots therein, a plurality of metal brackets clamped between said disc and said plate and extending respectively through said slots, a fusible link at the extending end ofeach of said brackets, a contact finger of heat conducting metal in electrical circuit with said heating elementand in the path of rotation of said fusible links, means resiliently urged against the rim of said plate to make contact "heating appliances, said device comprising a rotatable mount including an insulating disc, a

"generally circular" contact making element super posed thereon, means rigidly clamping said contact element and said disc together, fuse link carrying elements'rising from said contact elemerit, a fusible link at the end of each of said carrying elements, a contact of heat conducting material engaged by one of said links pressing thereagainst'and maintaining the corresponding carrying elements in circuit, whereby upon weak- 'ening of the engaged link the latter will be rup- 'tured, means successively to bring said links into engagement with said contact, said rotatable mount having peripheral ratchet teeth and coacting pawl means for limiting the rotation of said mount.

19; In an electrical appliance of the type comprising a base, a bottom plate afiixed thereto, a heating element and terminal plugs for connecting a source of current to said heating element; the combination therewith of a substantially cylindrical insulating mount affixed to the top of said base, extending through an opening therein, and supporting said heating element, a substantially cylindrical casing affixed to said base and encompassing said heating element, a bolt extending through an opening in said mount, said bolt being connected at its upper end to one end of said heating element and protruding from said mount; at its lower end, a substantially L- shaped gbracket, the transverse arm of which has an opening therein through which the lower end of said insulating mount extends, said arm being clamped to the underface of the top of 1 said base, a contact finger rigidly affixed to the vertical .armjof said bracket, extending substantially longitudinally thereof, electrically insulated :therefrom and in heat conducting relation thereito, an electrical conducting connecting strip af- -fixed at one end to said contact finger and at its other end to the protrudingend of said bolt, a

'mount having a plurality ofsupports therein, a "fusible link carried by each of said supports,

one of said links being engaged by said contact finger and maintaining the corresponding sup- .rfi'nger and the next fusible link for engagement thereof. 20. In an electrical appliance of the type comprising a base, a bottom plate affixed thereto,-a

heating element aifixed to the top of said base and terminal plugs for connecting a source of current to said heating element; the combination therewith of a protective device therefor, said device comprising an insulating disc, a generally circular contact making plate afiixed to said disc urging the latter with its disc and contact plate to rotate in one direction, a resilient arm on said .bottom plate having a pawl at one end thereof adapted successively to engage said notches to limit the rotation of said contact plate, and electrically connected at its other end to one; of said terminal plugs, manually operated trigger means to disengage said pawl from its respective notch, a plurality of substantially L-shaped brackets clamped between said disc and said contact plate and respectively rising upwardly through the slots in said contact plate, a fusible link aflixed to the free end of each of said brackets, a con-- tact finger connected to. one end of said heating element and depending from the top of said base in the path of movement of said fusible link normally spaced therefrom when said pawl is'in one of said notches, and engaged by the next link when said trigger is goperated.

: 21. The combination set forth in claim 20, in which said resilient means to rotate said shaft 12 comprises-a wound coil spring encompassing said shaft, afiixed thereto at one end and rigidly affixed at its other end to said base.

22. The combination set forth in claim 20, in which the end of said shaft passing through said bottom plate has means thereon to indicate the setting of said shaft and said disc and contact plate thereon.

23. The combination set forth in claim 20, in which said trigger comprises an insulated cam member normally resilient arm, a rotatable shaft supporting said cam -member at its upper end and passing through said bottom plate, and a knob afflxed to the lower end of said shaft, whereby when said "knob is turned, said insulated member will cam said resilient arm outwardly to withdraw said pawl from said notch, thereby permitting rotation of said shaft by said resilient means therefor.

24. A protective device for electric heating appliances, said device comprising a rotatable mount having a plurality of radiating fusible links thereon, a contact finger of heat conducting material in the pathof rotation of said fusible links and normally engaging one of said links to effect circuit closure through said mount; tension spring drive means urging said mount to rotate in one direction the latter being resiliently arrested by the engagement of said link and said contact whereby upon weakening of 'the engaged link the stressed mount will -ro- 'tate to rupture said link, thereby to open the circuit, means automatically to limit the rotation of said mount to retain said contact spaced from the next fusible link, and means effective upon release of the latter means to bring said next link into engagement with said contact finger.

EMIL KOLISCH.

' REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS in engagement with said

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