US2363674A

US2363674A - Cigar lighter

Info

Publication number: US2363674A
Application number: US259589A
Authority: US
Inventors: Arthur A Johnson
Original assignee: Automatic Devices Corp
Current assignee: Automatic Devices Corp
Priority date: 1939-03-03
Filing date: 1939-03-03
Publication date: 1944-11-28
Anticipated expiration: 1961-11-28

Description

A. A. JOHNSON CIGAR LIGHTER Nov. 28, 1944.

Filed March 3, 1939 I INVENTOR Arthur A. Johnson I D f ATTORNEYS Patented Nov. 28, 1944 2,363,674 CIGAR. LIGHTER Arthur A. Johnson, Bridgeport, Conn, assignor to Automatic Devices Corporation, Bridgeport, Conn.,.a corporation of Connecticut Application March 3, 1939, Serial No. 259,589

Claims.

This invention relates to cigar lighters, and. more particularly, to cigar lighters of the type in which the circuit to the heating element is opened upon the heating element reaching a predetermined desired heat.

In prior constructions of cigar lighters of this type, it has been proposed to use mechanically interlocking elements such as detents or the like, which engaged and held the igniting unit in a position wherein a circuit was completed to the heating element. The detents or the like, after the heating element had reached a predetermined desired heat, were caused to be released whereupon the circuit to the heating element was opened. The detent members had to be sturdy enough to hold the circuit closed against accidental release thereof, but yet flexible enough to permit disengagement from their cooperating elements to open the circuit when the heating element had reached the desired temperature. The range of movement of the detents was not of any considerable moment, but, nevertheless, was critical in order to insure proper operation. This necessitated careful adjustments of the detents and their cooperating elements at the time the devices were assembled, which increased the cost of production.

An object of the present invention is to provide a cigar lighter in which the circuit is maintained closed, without theuse of detents or the like until the heating element has reached a predetermined desired heat, at which time the on cult is opened. This is accomplished by an electromagnet carried by the igniting unit and which is energized upon the closing of the heating element circuit. A magnetic pole piece or armature is disposed within the holding device which cooperates with a magnetic pole piece or core carried by the igniting unit and magnetized by the coils of the electromagnet. The two pieces are brought into engagement when the ignitin unit is moved to the closed-circuit position and are held in the closed-circuit position by magnetic attraction until the heating element has reached its predetermined desired heat. When 45 this occurs, in one form of the invention, the circuit is interrupted and the electromagnet is no longer energized.

In this form of the invention, the circuit includes a normally closed theme-responsive 60 switch member which is adapted to open the circuit when the heating element reaches thepredetermined desired temperature,

In another form of the invention, a normally open therm'o-mponsive switch is adapted, when the heating element reaches its predetermined desired temperature, to close a shunt circuit around the electromagnet, whereupon the electromagnet is short-circuited and the igniting unit moved to open-circuit position.

In either form of the present invention, as there are no mechanical latches or detents employed, the same care in adjusting during assembling is no longer necessary as in the case of the heretofore proposed devices in which such latches or detents were employed. This greatly facilitates the manufacture and assembling of the cigar lighter, and, consequently, reduces the manufacturing costs thereof.

In these prior devices where detents or latches are employed, it was necessary to match the separable parts to insure proper operation of the holding elements, but in the present invention, the separable parts of the device need not be made so as to match each other in each particular cigar lighter for best results, and hence, the igniting units and holding devices are interchangeable with other like igniting units and holding devices.

Other features and advantages will hereinafter appear.

In the accompanying drawing:

Figure 1 is a view of one form of the invention with the holderin section and the ignitin unit in open-circuit position.

Fig. 2 is a longitudinal section of the holder and igniting unit of Fig. 1, with the igniting unit in closed-circuit position.

Fig. 3 is a view similar to Fig. 1 showing another form of the invention with a portion of the igniting unit broken away to show the switch I employed in this form of the invention.

Fig. 4 is a view similar to Fig. 2, but showing the form of the invention illustrated in Fig. 3.

Fig. 5 is a sectional view taken along line 5-! of Fig. 1.-

Fig. Bisaviewsimilartol'ig. 5, but taken along line 0-8 of Pig. 3.

As shown in the drawing, the cigar lighter comprises a tubular metal holder in having a rear transverse wall II. The holder is adapted to be mounted on and grounded to an instrument panel or other support I! and is provided with tangs ll adjacent its open end which are adapted to engage the rear side of the panel II. A collar is is threaded on the open end of the holder and engages the front face of the panel I! and draws the tangs it into ilrm engagement as with the rear side of the panel, thereby formin a good ground connection and a rigid mounting for the holder.

According to the present invention, a contact is mounted on the holding device, and, in the preferred form of the invention, this contact comprises a flat member disposed in the base of the holder. The member I5 in the now preferred embodiment of the invention, as will be hereinafter more fully explained, is an armature and is formed of some magnetizable material. In mounting the armature in the holder, a conductor sleeve I6 is disposed in a central aperture in the rear wall H of the holder l0 and is insulated therefrom by insulating washers ll. The sleeve has a flange l8 which engages the washer I! on the inside of the rear wall. The sleeve I6 is threaded on its outer surface to receive a nut l9 which is threaded thereon and clamps the sleeve in place in the central apertures in the rear wall.

The conductor sleeve isconnected to a suitable source of energy as by a connector lug secured to a conductor 2| leading to one terminal of the source of energy. The connector lug is secured in good electrical engagement with the conductor sleeve by a nut 22 threaded on the sleeve. The armature I5 is mounted in the base of the holder and is electrically insulated therefrom as well as the conductor sleeve It.

A bolt 23, surrounded by an insulating sleeve 24 and disposed within the conductor sleeve It so as to be insulated therefrom and having its threaded end projecting from the rear end there of, holds the armature in place. The bolt is locked in place by means of a nut 25 threaded on the projecting end thereof. A conducting disk 26 isdisposed between the flange ll of the conducting sleeve it and an insulating washer 21. The disk is provided with an arm 28 carrying a contact member 29 adjacent the free end thereof. A second disk 30 of suitable bimetallic material is interposed between the insulating washer 21 and the armature [5. The bimetallic disk 30 has an arm formed integral therewith which carries adjacent the free end thereof a contact member 3|, which normally is held in engagement with the contact 29. The two disks 2B and 30 are clamped in place by the nut 25 when the same is threaded onto the bolt 22. The disk 25 is in facewise engagement with the flange of the conducting sleeve i6, and, as the contact l5 and its associated elements are tightly clamped to the rear wall i I of the holding device, good electrical contact is insured between the flange and the disk. The disk 30 is also securely held in facewise engagement with the flat contact l5, which engagement insures good electrical contact therebetween.

The holder is adaped to have an igniting unit 32 movably mounted therein and completely removable therefrom for use. The igniting unit, as shown in Fig. 2, comprises a flanged friction sleeve 33 preferably formed of non-magnetic material having coaxially arranged therein a sleeve 34 of insulating material and held therein by the inwardly extending flanges 3 5 and 350 respectively on the opposite ends of the sleeve 33. A thimble member 10 of magnetizable material is disposed within the sleeve 24 andhas the open end thereof closed by means of an insulating disk 31. A bolt 38, having one end thereof reduced and projecting through the insulating disk 31, is secured thereto as by being headed over. The opposite end of the bolt extends through a centrally located aperture in the transverse wall of the thimble. A disk 39 insulates the thimble from the friction sleeve and is held in place by a nut 40 threaded onto the end of the bolt which projects through the aperture formed in the wall of the thimble. A handle or knob member ll of some suitable insulating material is threaded onto the projecting end of the bolt. 5

The other end of the igniting unit carries a heating element 42 in the form of a flat spiral coil of resistance wire having one end thereof electrically connected to the open end of the thimble. The opposite end of the resistance wire is led through a suitable aperture in the disk 31 and is connected to one end of a coil of insulated wire 43 wound about the bolt. The opposite end of the wire coil-43 is secured by any conventional means, such as spot welding, to the friction sleeve 33.

The igniting unit is normally held in opencircuit position on the holder by means of a ring 44 having aplurality of inwardly extending lugs 45 projecting through a plurality of longitudinal slots 46 formed in the holding device lil. A coil spring 41 is disposed intermediate the ring 44, and outwardly extending tabs 48 lanced from the holding device. The spring urges the ring outwardly and the lugs 45 engage the inturned flange 35 of the friction sleeve and normally hold the igniting unit in a shallow position on the holder, but will permit the igniting unit to move inwardly upon pressure exerted on the handle.

When the igniting unit is moved inwardly, the open end or pole piece of the thimble 38 will engage the armature l5, and a resilient contact I! lanced from the friction sleeve will be in engagement with the holding device, thereby completing the energizing circuit for both the electrojmagnet and the heating element. The energizing circuit will extend from the conductor 2i through the sleeve I6, switch 29-, to the contact l5, thimble 36, the heating element, through the coil of the electromagnet to the friction sleeve which is grounded as heretofore explained.

As soon as the energizing circuit is closed. the pole piece 36 will become magnetized and the attraction between it and the cooperating armature l5 will hold the ignitin unit in a closedcircuit position. In the now preferred embodiment of the invention, the armature l5 also functions as a contact as does also the open end of the thimble-like pole piece 36. It will be understood, however, that contacts separate from the armature and thimble-like pole piece could be employed. The member l5 might be a seprate ring of magnetizable material carried by the holding device, and the circuit could be completed when a contact separate from the pole piece 36 and electrically connected to the coil was brought into engagement with a contact carried by the holding member.

According to the present invention. when a heating element acquires its predetermined heat, the magnetization of the pole piece It is destroyed so that it no longer holds the igniting unit in closed-circuit position. The magnetization of the pole piece is destroyed in this form of the invention by means of the switch 20, II which is mounted on the holding device in heatreceiving relation with the heating element. To insure an effective heat-receiving relationship between the heating element and the switch, the

open end of the thimble is provided with a series 0f perforations 5! which will allow the heat from the heating element to escape and rise through the aperture 52 formed in the holding device and through which the switch projects.

It will be seen that when the heating element is energized, heat will be carried by radiation and convection currents to the switch, thereby insuring a good thermal relationship between the heating element and the switch.

When the heating coil reaches a predetermined heat, the switch will become heated and will'fiex to the dotted line position shown in Fig. 2, thereby breaking the circuit which includes both the heating element and the electromagnet, and the magnetic pull resulting from the magnet coil will be no longer effective to hold the igniting unit in the closed-circuit position and the ejector spring will move the igniting unit into open-circuit position.

In the form of the invention shown in Figs. 3, 4 and 6, a holding device 52 is mounted on and grounded to an instrument panel or like support in a manner similar to that described in connection with the invention shown in Figs. 1, 2 and 5.

In the form of the invention now being described, an armature 53 is mounted on, but insulated from the transverse wall of the holding device, by a bolt-54 having a threaded end projecting through a centrally located aperture in the end wall of the holding device. The bolt is insulated from the holding device by insulation 55.

A nut 55 is threaded onto the end of the bolt and rigidly secures the contact 53 to the holding device. A conductor lug 51, connected to a suitable current supply wire 58, is mounted on the threaded end of the bolt and secured thereto by means of a nut 59. In this form of the invention, the igniting unit comprises a flanged friction sleeve 50, preferably of nonmagnetic material, having coaxially arranged therein a sleeve 5| of insulating material. A metallic thimble member 52 is also coaxially disposed within the sleeve El and the open end thereof is closed by a perforated transverse disk 53 of some suitable insulating material such as mica. The disk 53 is held to the open end of the thimble by a bolt 64, the opposite end of which projects through a centrally located aperture in the transverse wall of the thimble member. This end of the bolt is threaded and receives a nut 55 which is threaded thereon until the same abuts a disk 55, which insulates the thimble from the flanged outer end of the frictionsleeve. A knob member 58 threaded onto the extended end of the bolt, serves as a handle which may be grasped by the fingers of a user.

The opposite end of the igniting unit carries a heating element 51 comprising a spiral coil of fiat resistance wire, the outer end of which is electrically connected to the friction sleeve 50. The opposite or inner end is electrically connected to a conducting sleeve 59 insulated from the bolt 64 by an insulating sleeve 10. The conducting sleeve 55 is provided with a flanged extension leading through a suitable aperture in an insulating disk II and connected to one end of a coil of insulated wire 12 carried within the thimble and disposed about the bolt 54. The

' opposite end of the coil 12 is connected by any suitable means to the thimble 52. A switch arm I3 of bimetallic material is mounted on the insulating disk 53,which arm carries adjacent the free end thereof a contactmember 15, and. the arm is so formed that normally the contact member 14 is out of engagement with a contact member 15 carried by the flange of the conducting sleeve 55.

The igniting unit is held in a normal opencircuit position, as shown in Fig. 8, by means of a ring 15 having a plurality of inwardly extending lugs which project through a plurality of ion. gitudinal slots formed in the tubular holding device. A coil spring 11 is disposed about the tubular holding device, the one end thereof engaging tabs 15 lanced from the holding device, the opposite end engaging the ring 15. The spring urges the ring outwardly and the lugs engage a shoulder 15 formed on the igniting unit and urges the igniting unit to the shallow open-circuit positionshown in Fig. 3. The igniting unit, however, may be moved into a deep closed-circuit position by pressure against the handle 55. When the igniting unit is moved inwardly against the action of the spring, the open end of the thimble 52, which constitutes a pole piece of the magnet, will engage the armature 55, and a resilient contact 50 carried by the ring 15 will be in engagement with the friction sleeve, thereby completing the energizing circuit for both the electromagnet and the heating element.

The energizing circuit will include the conductor 58, bolt 54, contact 53 through the thimble member 52, coil 12, conducting sleeve 59 through the heating coil 51, to the friction sleeve and thence to ground through the ring 15.

As soon as the energizing circuit is completed, the pole piece 52 cooperating with the armature 53 will hold the igniting unit in the closed-circuit position. The heating element, as the same attains its predetermined desired temperature, will cause the bimetallic switch arm I3 to move into the dotted line position, as shown in Fig. 4, causing an engagement between the

contacts

14 and 15 which short circuits the coil 12, thereby destroying the magnetization of the pole piece, and the igniting unit will be moved to the shallow circuit opened position.

It will be seen that the closing of the switch 14,

' I5 will shunt the coil 12, for the circuit, after the switch has been closed, will include the currentsupply wire, bolt 55, armature 53, pole piece 52, switch '14, 15, conducting sleeve 59, heating element 51, frictional sleeve 50 which, as has been previously explained, is grounded by means of the ring i|5 and the holding device to the supporting pane In the just described form of the invention, the armature 53, pole piece 52, have also been shown as contact members, but as previously explained during the description of the form of the invention shown in Figs. 1 and 2, separate contact members may be employed.

In this form of the invention, as in the previously described form, no mechanical locking means are employed, so that the assembling of the device is not made complicated by careful adjustments of the mechanical locking elements to insure their effective cooperation. This greatly facilitates the manufacture of the device and reduces the manufacturing costs thereof.

In the installation of the device of the present invention, as no mechanical or looking elements are employed, the two separable parts, that is the holding device and removable igniting unit, need not be matched so that the igniting units and holding devices are interchangeable with other like igniting units and holding devices.

In addition to facilitating the manufacture and installation of the devices, thi feature is also a great advantage in the servicing of cigar lighters, for ii! an igniting unit, for example, should become defective through misuse, it may be replaced by a similar igniting unit without necessitating a change or replacement of the existing holding device.

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

I claim: I

a 1. In an electric cigar lighter, a holding device; an igniting unit including a heating element, mounted on the holding device; means including an electric circuit for energizing the heating element; circuit control means therefor, including a magnetizable contact carried by the i niting unit, and means normally urging said magnetizable contact to open-circuit position; and electro-responsive and heat responsive means carried by the igniting unit and made operative solely by the closing of said circuit by said circuit control means, for magnetizing the contact and holding the circuit closed by magnetic attraction or the magnetizable contact, the magnetic attraction of the contact being rendered inoperative upon said heating element reaching a predetermined desired heat, whereupon said urging means moves said circuit control means to open-circuit position.

2. In an electric cigar lighter, a holding device; an igniting unit including a heating element, mounted on the holding device; means including an electric circuit for energizing the heating element, circuit control means therefor, and means normally urging said circuit control means to open-circuit position; electro-magnetic means carried by the igniting unit and made operative solely by the closing of said circuit by said circuit control means for holding the circuit closed by magnetic attraction between the circuit control means; and heat-responsive means for deenergizing said electro-magnetic means to render it means upon said heating element reaching a predetermined temperature, said means including a bimetallic switch carried by said igniting unit. connected in parallel with said electro-responsive means, and responsive to the heat of the heating element.

5. In an electric cigar lighter, a holding device; an igniting unit including a heating element, mounted on the holding device; means including an electric circuit for. energizing the heating ele ment, circuit control means therefon'and means normally urging said circuit control means to open-circuit position; electromagnetic means carried by the igniting unit and made operative solely by the closing of said circuit by said circuit control means for holding the circuit control means in closed-circuit position by magnetic attraction; and means in said circuit responsive to the heat from the heating element for rendering said electromagnetic means inoperative upon said heating element reaching a predetermined desired heat whereby the circuit to said heating element is opened by said urging means.

6. In an electric cigar lighter, a holding device; an igniting unit including a heating element movably mounted on the holding device; means including an electric circuit controlled by movement of said igniting unit to closed-circuit position for energizing the heating element; means for urging the igniting unit to open-circuit position; electromagnetic means carried by said igniting unit for holding the igniting unit in a closed-circuit position upon movement thereof to said position, said magnetic means being the sole means for holding the igniting unit in closed-circuit position; and means automatically rendering said magnetic means inoperative upon said heating element reaching a predetermined desired temperature, whereupon said urging means moves said igniting unit to open-circuit position.

inoperative to hold the circuit closed upon said vice; an igniting unit including a heating element, mounted on the holding device; means including an electric circuit for energizing the heating element, circuit control means therefor, and means normally urging said circuit control means to open-circuit position; electro-responsive means carried by the igniting unit and made operative solely by the closing of said circuit by said circuit control means, for holding the circuit closed; and thermostatic means for shunting out said electro-responsive means to render same inoperative upon said heating element reaching a predetermined temperature, whereupon said urging means moves said circuit control means to opent osition. i in an electric cigar lighter, a holding device; an igniting unit including a heating element, mounted on the.,holding device; means including an electric circuit for energizing the heating ele ment, circuit control means therefor, and means normally urging the circuit control means to open-circuit position; electro-responsive means carried by the igniting unit and made operative solely by the closing of said circuit by said circuit control means, for holding the circuit closed ,by magnetic attraction of the elements of said circuit control means; and heat-responsive means for shunting out said electro-responsive 7. In an electric cigar lighter, a holding device; an igniting unit including a heating element; movably mounted on the holding device; means including an electrical circuit controlled by movement of said igniting unit for energizing the heating element; means for normally urging the igniting unit to open-circuit position; means for moving said igniting unit to a closed-circuit position, magnetic means carried by the igniting unit for holding the same in closed-circuit position upon movement thereto, solely by the magnetic attraction of its magnetic held; and thermostatic means for destroying the magnetic Iield of said magnetic means upon the heating element reaching a predetermined desired heat, whereby the igniting unit is released and moved by said urging means into open-circuit position.

8. In an electric cigar lighter, a holding device; an igniting unit including a heating element, movably mounted on the holding device; means including an electrical circuit controlled by movement of said igniting unit for energizing the heating element; means for normally urging the igniting unit to open-circuit position; eiectromagnetic means carried by said igniting unit and forming a part of said heating element circuit, the magnetic field, produced upon energization oi said electromagnetic means, alone holding the igniting unit in closed circuit position by magnetic attraction when moved to said position; and heat-responsive means for opening the circuit and rendering said electromagnetic means inoperative upon the heating element reaching a predetermined desired heat wherebythe igniting aseaen unit is released for movement by saidurging means into open-circuit position.

9. In an electric cigar lighter. a holding device; an igniting unit including a heating element, movably mounted on the holding device; means including anelectrical circuit controlled by movement of said igniting unit for energizing the heating element; means for normally urging the igniting unit to open-circuit position; means for moving said igniting unit to a closed-circuit position; electromagnetic means for holding the igniting unit in closed-circuit position upon energization thereof, said electromagnetic means carried by the igniting unit and forming a part of said heating element circuit, and the magnetic field produced upon energization of said electromagnetic means alone holding said igniting unit in said position by magnetic attraction; and a normally closed heat-responsive switch means in said circuit adapted to open the circuit upon the heating element reaching a predetermined desired heat whereby the electromagnetic means is rendered inoperative and the igniting unit released for movement by said urging means into open-circuit position.

10. In an electric cigar lighter, a holding device; an igniting unit including a heating element, movably mounted on the holding device; means including an electrical circuit controlled by movement of said igniting unit for energizing the heating element; means.for normally urging the igniting unit to open-circuit position; means for moving said igniting unit to a closed-circuit position; electromagnetic means for holding the igniting unit in closed-circuit position upon energization thereof, said electromagnetic means carried'by the igniting unit and forming a part of said heating element circuit, and the magnetic field produced upon energization of said electromagnetic means alone holding said igniting unit in said position by magnetic attraction; and a normally closed heat-responsive switch means included in said circuit carried by said holding device and adapted to open the circuit upon the heating element reaching a predetermined desired heat whereby the electromagnetic means is rendered inoperative and the igniting unit released for movement by said urging means into open-circuit position.

11. In an electric cigar lighter, a holding device; an igniting unit including a heating element, movably mounted on the holding device; means including anelectrical circuit controlled by movement of said igniting unit for energizing the heating element; means for normally urging the igniting unit to open-circuit position; means for moving said igniting unit to a closed-circuit position; electromagnetic means for holding the igniting unit by magnetic attraction in closedcircuit position upon energization thereof, said electromagnetic means carried by the igniting 'unit and forming a part of said heating element circuit and the magnetic field produced upon energization of said electromagnetic means alone holding said igniting unit in said position; and a normally open heat-responsive switch means carried by the igniting unit and adapted to close a shunt circuit for short-circuiting the electromagnetic means upon the heating element reaching a predetermined desired heat whereby the igniting unit is released for movement by said urging means into open-circuit position.

12. In a cigar lighter of the type described, a holding device; a pole piece mounted on said holding device;

heating element, movably mounted on the holding device and being completely removable therefrom for, use; a solenoid carried by said igniting unit, connected in series with said heating element; means including a circuit andcircuit control means therefor for energizing said heating element and solenoid when said igniting unit is moved to a closed-circuit position; means normally urging said igniting unit to open-circuit.

position; a pole piece carried by said igniting unit 1 adapted to be magnetized by the energization of an igniting unit including a 15 said solenoid and cooperable, when magnetized, with the pole piece mounted on said holding device for holding the igniting unit in circuit-closed pomtion solely by magnetic attraction; and heatresponsive switch means for reducing the energization of said solenoid upon the heating element reaching a predetermined temperature, said urging means thereupon moving said igniting unit to open-circuit position.

13. In a cigar lighter of the type described, a holding device; a: pole piece mounted on said holding device; an igniting unit including a heating element, movably mounted on the holding device, said igniting unit being completely removable from said holding device for use and comprising a hollow plug-like member; a solenoid disposed within the hollow igniting unit, connected in series with said heating element; means including a circuit and circuit control means therefor for energizing said heating element and solenoid when the igniting unit is moved to a closed-circuit position on said holding device; means normally urging said igniting unit to open-circuit position; a pole piece carried by said igniting unit and coaxially disposed relative to said electromagnet and adapted to be magnetized by the energization of said electromagnet and cooperable, when magnetized, with the pole piece mounted on said holding device for holding the igniting unit in closed-circuit position solely by magnetic attraction; and heat-responsive switch means for reducing the energization of said solenoid upon the heating element reaching a predetermined temperature, said urging means thereupon moving said igniting unit to open-circuit position.v

14. In a cigar lighter, a holding device; an igniting unit having a heating element thereon; an electromagnet carried by said igniting unit; an energizing circuit for the heating element and electromagnet including a pair of contacts, each comprising a mass of paramagnetic mate- 'rial; means normally urging said contacts to open-circuit position, one of said contacts being supported by the igniting unit for manual movement into engagement with the other contact carried by the holding device to close the energizing circuit, the contact carried by said ignit ing unit being adapted to be magnetized by the energization of said electromagnet and cooperable, when magnetized, with the contact mounted on said holding device for holding the said contacts in closed-circuit position solely by magnetic attraction; and an auxiliary circuit including a bimetallic switch carried by the igniting unit for shunting out the electromagnet when the heating element reaches a predetermined desired temperature, said urging means thereupon moving said contacts to normal open-circuit position.

15. In a cigar lighter, a holding device; an igniting unit having a heating element thereon; an electromagnet carried by said igniting unit; an

tact mounted on said holding device for holding the said contacts in closed-circuit position solely by magnetic attraction; and a bimetallic switch carried by the holding device and connected in seriu with said electromagnet i'or interrupting the energizing circuit and deenergizing the electromagnet when the heating element reaches a predetermined'desired temperature, said urging means thereupon moving said contacts to nor- 1 mal open-circuit position.

ARTHUR A. JOHNSON.