US1767816A - Electrical heating unit - Google Patents

Description

June 24,1930; 1 H. N. SHAW 1 ,767

ELECTRICAL HEATING UNI-'1 Filed Ma 19.- 1926 2 Sheets-Sheet 1v fBLBbTRI CAL HEATING unt r Patented June 24, 1930 UNITED STATES PATENT OFFICE HAROLD N. SHAW, OF MILWAUKEE, WISCONSIN, ASSIGNOR TO GLOBAR CORPORATION, OF NIAGARA FALLS, NEW YORK, A CORPORATION OF NEW YORK ELECTRICAL HEATING UNIT Application filed May 19, 1926. Serial No. 110,088.

The present invention relates in general to electrical apparatus including one or more resistance units of a type ada ted for the production and emission of radiant energy in the form of heat or light or a combinationof both effects; and the invention has particular relation to apparatus of this type wherein the desired effects are produced wholly through radiation from the source ofrays or partly through direct radiation and partly through reflection.

Features of the present invention are concerned with the efficient utilization of suitable resistance elements or units of the selfsustaining type, especially such as are of a non-metallic character and include silicon air-bide as an essential ingredient, more particularly through the design and construction of simple, efficient and economical mountings for such resistance units. In electrical heating apparatus utilizing preferred types of heating units adapted for the production of relatively high operating temperatures, and also heating or lighting effects dependent upon the radiation of rays of special character for utilization for therapeutic and other purposes, it is especially desirable to satisfactorily maintain the re sistance heating element in mechanically and electrically operative position in the heating apparatus. The high temperatures ordina rily present adjacent the point of engagement or contact between the heating element and conductive terminal or mounting devices therefor have caused deterioration of the contact.

In accordance with the present invention, an electrical heating appliance or device is providedwhich is especially adapted for producing and radiating heat waves or a combination of heat and light waves of special character, and which utilizes as a heat or light source a self-sustaining or rigid element, preferably of a non-metallic character and provided with terminals more highly conductive than the body portion, mounted in a yielding and readily detachable manner between contact terminal elements or devices which are securely and efficiently held in position and serve to mechanattachment or securing in operative position in a reflector or like carrier.

It is an ob ect of the present invention to provide an electrical appliance of improved design and construction embodying a selfsustaining resistance element and terminals therefore securely and efficiently mounted upon a support or base and devices effective to maintain the resistance element in mechanically and electrically operative position through yielding butt-end engagement with its terminals.

It is a further object of the present invention to provide an electrical heating appli ance of the character described embodying one or more self-sustaining resistance elements and terminals therefor mounted on a support, in combination with a reflector or other carrier in which the base is mounted in a readily detachable and replaceable manner.

It is a further object of the present invention to provide an electrical heating unit of improved design and construction embodying one or more rigid and self-sustaining electrical resistance heating elements and terminal contacts therefor mounted upon a supporting plug or the like and arranged symmetrically about the axis thereof, and wherein the heating elements are yieldingly held in operative position and readily detachable from and replaceable in such operative position.

These and other objects and advantages are attained by the present invention, various novel features of which will be apparent from the description and drawings herein, disclosing several embodiments of the invention, and will be more particularly pointed out in the claims.

In the accompanying drawings:

Fig. 1 is a partly sectional elevation of an electrical heating appliance of the radiant reflector type, including a form of heating unit embodying features of the present invention.

Fig. 2 is a plan view of the heating unit of the apparatus shown in Fig. 1.

Fig. 3 is a partly sectional side elevation of the heating unit of Fig. 1.

Figs. 4 and 5 are views similar to Fig. 1, showing modified embodiments of features of the invention.

Fig. 6 is a plan view of the heating unit shown in Fig. 5.

Fig. 7 is a partly sectional side elevation of the heating unit-of Fig. 5.

Fig. 8 is a view similar to Fig. 1, showing a further modified embodiment of features of the invention.

Figs. 9, 10, 11 and 12 are views similar to Figs. 5, 6, 7 and 8, respectively, showing further embodiments of the invention.

In Fig. 1 of the drawing, there .is disclosed a radiant heater of the bowl-shaped reflector type. The body portion of the reflector, indicated at 11, may be considered as of the ordinary parabolic type having a central aperture in which a socket 12 of insulating material is secured, this socket having a flange 13 at its inner end bearing against the inner wall of the reflector. The socket 12 is held in position by means of a nut 14 threaded on the rearwardly projecting portion of the socket and bearing against the outer wall of the reflector. A metallic screw shell or bushing 15 is fixed in position within the socket 12, as by being threaded into a cooperatively threaded portion of the wall of the socket, an extension 16 on the shell 15 being secured in position by a screw 17 which passes through the rear Wall of the socket, being held in place by a securing nut and also serving as a means for connecting the conductive shell 15 to a line terminal. A centrally located spring contact 18 has an apertured extension through which a connection screw 19 passes, this screw passing through the rear wall of the socket, being held in place therein by a securing nut and serving to maintain the contact 18 in operative position and also acting as a line terminal connection.

A plug 21 includes an insulating body having a conductive and externally threaded metal shell 22 fixed thereon and adapted to be threaded into the conductive shell 15 so as to thereby hold the plug in operative position. A contact cap or button 23 is secured to the upper face of the plug 21, with an insulating spacing washer 24 interposed between the lug and the cap 23. This contact cap 23 is preferably of highly conductive and suitably heat resistant metal, aluminum, or an alloy of nickel and iron or chromium, nickel and iron, such as ascoloy, being satisfactory for the particular purpose. The use of aluminum as a contact material for engagement with the ends of silicon carbide resistor rods is disclosed and claimed ,in my copending application U. S. Serial No, 386,979 filed August 19, 1929. The contact piece 23 and the insulating spacer 24 are held in operative position by means of securing screws 25, 25 passing through apertures in portions of the conductive shell 22 which are bent over against the bottom of the plug 21, as indicated at 27, and through alined apertures in the plug 21 and insulating spacers 24, the heads of the securing screws bearing against the bent over portions 27 of the shell 22, and the upper ends of these securing screws being threaded into the conductive cap 23. As indicated, these spaced securing screws 25, 25 constitute eflicient holding means for securing the contact piece 23 in operative position, and particularly against any tendency toward rotation or other displacement thereof.

The upper side of the plug 21 is provided with a recess 29 extending diametrically across the plug, this recess receiving a strip 31 of conductive metal of such size as to fit fairly closely in the recess, the strip extending outwardly beyond the plug with its opposite ends turned over to form resilient bowed portions, as indicated at 32, 32. This conductive element 31 is preferably formed of resilient and highly heat resistant material, such as monel metal, and it is held in place by a screw or bolt located centrally on axially of the plug 21. he head of this securing bolt, the latter being indicated at 34, bears against the upper side of the conductive strip 31, the lower end of the bolt being threaded and having secured thereon a cap nut which bears against the lower face of the plug 21 and holds the bolt and the conductive strip 31 in desired operative position, the lower face of the cap nut 35 constituting a central terminal contact for the insulating plug, the screw shell 22 serving as the other terminal.

The upper side of the contact cap or piece 23 is provided with a recess 36 located axially of the plug 21, this contact recess or cavity 36 being adapted to receive a terminal end of a rigid and self-sustaining resistance heating element 37. This resistance heating element 37 is preferably a unitary, self-sustaining, molded and l1eatl1ardcned composition product wherein a carbonaceous material, such as silicon carbide, is the principal constituent. Certain heating elements of the preferred character are well known in the art, the same bein composed of silicon carbide as an essential constituent, with or Without one or more modifying substances for altering mechanical or electrical characteristics of the final resistance element. Likewise, this resistance element is preferably such as has its end or terminal portions considerably more highly conductive than the body portion of the element, and conscquently less liable to such heating as might have a deleterious effect upon the metallic contacts associated with the terminal portions of the resistance element.

This resistance element 37 is disposed in substantial alinement with or synnnetrical with respect to the axis of the socket 12 and the reflector 11, the other terminal end of the heating element being disposed in a central cavity or recess formed in a contact piece or bridge 38, the recess 39 permitting easy reception of this upper end of the heating element 37. The contact bridge 38 is held in operative position by means of diametrically opposed rods 41, 41 of cold rolled steel, monel metal, or like heat resistant conductive metal of the required tensile strength. The upper ends of these rods 41, 41 pass easily through apertures in the contact bridge 38 and are 1'1"Ot8(l over at the upper side thereof, as indicated at 42- Pertions 43 are pinched or struck up from the material of the rods 41, 41 to serve as ledges or supports for the bridge 38, and these supporting portions 43 may be so disposed as to permit slight movement of the bridge 38 on the rods 41, 41 between such supporting portions and the headed ends 42 on the rods, for the purpose of providing for slight adjustment of the bridge 38, so as to permit the upper end of the heating element 37 to readily establish a suitable area of contact in the recessed portion 39, and generally to provide for equalization of the strain on the supporting rods 41, 41.

As indicated, the inner ends of the upper inwardly turned portions 45, 45* of the bowed spring or resilient elements 32, 32*, respectively, of the contact strip 31 are aperturcd and the lower ends of the rods 41, 41 are headed over therein so as to secure these rods against upward movement relative to these portions 455, 45 of the contact strip 31. As indicated, portions of the rods 41, 41 are pinched or struck up, as indicated at 46, for the purpose of securing the lower ends of the rods in operative position and against substantial movement downward relative to the spring portions 45, 45; and, if desired, provision may be made for any desired amount of lost motion or play between the head at the lower end of each rod and the struck-up portion 46 thereof, in a manner similar to that described for securing the upper ends of these rods to the bridge 38.

Vith the parts in the condition described, a circuit is established from the terminal screw 17, through the metal shell 15 and metal shell 22, the securing bolts 25, contact piece 23, heating element 37, bridging contact piece 38, securing rods 41, 41, contact stri 31, and securing bolt 34, to terminal 35, t ence through spring contact 18, to terminal screw 19.

The cavities or recesses 36 and 39 in the contact pieces 23 and 38, respectively, are of such size and shape, preferably more or less conical in shape, vas to readily receive the terminal ends of the heating element 37 and insure effective mechanical support and electrical engagement through butt-end contact between the terminal ends of the heating element and the walls of the recesses in these contact pieces.

With the parts arranged as described, and the resilient contact strip 31, with its bowed spring portion 32, 32", of the required strength and resilience, these spring portions exert, through the intermediary of the tension rods 41, 41, the desired and required force to resiliently or yieldingly draw or force the contact piece 38 against the upper terminal end of the heating element 37 and thus yieldingly hold the lower terminal end of the latter in secure and effective butt-end engagement within the contact recess 36 in the terminal cap 23, with the heating element thus held in substantial alinement with the axis of the supporting plug 21 and the reflector 11 in which the plug is mounted, and with just the amount of pressure required to maintain the heating element in secure position, from a mechanical and electrical standpoint. Obviously, the cross-sectional area of the spring portions of the contactstrip 31 is such that no appreciable heat is generated therein; and these resilient portions are sufiiciently removed from the heating element 37 so that the mounting retains its required resilience during operation.

In order to remove or replace the heating element 37, the bowed. spring portions 32, 32 are distorted, as by moving the same toward each other, to thus lift the lower ends of the rods 41, 41 and the bridging contact 38 sufficiently to permit transverse movement of the upper end or both ends of the heating element 37 out of their respective contact recesses 39 and 36; and under these latter conditions, the heating element 37 may be readily removed or a replacement element inserted to operative osition by a transverse movement thereo and the bowed spring portions 32, 32 may then be permitted to return to normal position wherein they, in conjunction with the rods 41, 41 and the bridge 38, are effective to support and maintain the heating element in electrically and mechanically operative position.

In accordance with the modification shown in Fig. 4, the inner terminal end of the heating element 37 is mounted in a contact recess 36 in the contact piece 23, but the supporting means for the upper or outer terminal end of the heating element is some-- what different from that of the apparatus of Fig. 1. As indicated, the upper terminal end of the heating element is disposed in a recess 51 formed in a contact piece 52 of conductive material. This contact piece 52 is attached, preferably by welding or riveting, to a relatively stiff and resilient mounting of conductive material in the general form of an elliptical or bowed spring 54, preferably of tempered steel, or other conductive and resilient material, such as monel metal or a suitable bronze. This spring element has its inner ends apertured and arranged in overlapping relation in the recess formed at the upper side of the plug 21, as indicated at 56, with the securing bolt 34 passing through the alined apertures in the ends of the resilient element, and when the cap nut 35 is secured in operative position. on the lower end of the securing bolt 34, the supporting bowed spring 54 is held in mechanically secure operative position and is connected through its terminal ends and the securing bolt 34 to the central terminal 35 of the plug 21. With the parts in this condition and the supporting spring element 54 of the required dimensions to provide a satisfactory resilient mechanical support and mounting for the upper end of the heating element 37, the latter is maintained in operative position, that is, in axial alinement with the supporting plug 21. The circuit through the heating element 37 and the other parts of the circuit between the terminals 17 and 19 is as has been described in connection with Fig. 1, with the exception that the bowed spring supporting element 1 and its upper terminal piece 52 are substituted for the contact strip 31, with its bowed spring portions 32, 32 and the supporting rods 41, 41*, and the contact bridge 38 held in position thereby.

lVith the parts arranged as described and a suitable design of the bowed spring element 541- as to strength and resiliency, this spring element exerts the desired and required pressure upon the terminal ends of the heating element 37 in the direction of the longitudinal axis thereof to maintain the element 37 in mechanically and electrically secure position.

In accordance with the disclosure of Figs.

5, 6 and 7, a plurality of resistance heating elements 37, 37", connected in parallel in the circuit and symmetrically arranged about the axis of the plug 21', are substituted for the single axially disposed heating element 37 ofFlg. 1. Instead of the contact piece 23, as shown'in Fig. 1, a plurality of contact pieces 61, 61 are mounted in opposed recesses at the upper side of the plug 21 by means of securing bolts 25, respectively, having their upper ends threaded into such contact pieces. Each of the contact pieces 61, 61' is made up of a strip of relatively heat resistant conductive material, such as monel metal, indicated at 62, and a strip of relatively softer and more highly condue tive material, indicated at 63, at its upper side, the pieces 62 and 63 being welded. riveted or otherwise secured together and each contact piece being provided with a contact recess 64 in the piece 62, or in both pieces 62, 63, for the reception of the lower terminal end of the corresponding heating element 37, 37". These contact pieces, 6], 61 are preferably mounted in alined recesses 67, 67* formed in the upper side of the plug 21, the'contact pieces fitting fairly closely in the recesses and being thus readily maintained in operative position. The upper terminal ends of the heating elements 37, 37" are received in recesses 39", 39 of a contact bridging piece 38, this, latter piece being held in operative position by rods 41, 41 secured to the bowed spring portions 32, 32 of the contact strip 31, all as generally described in connection with the device disclosed in Figs. 1, 2 and 3. The body portion of the contact strip 31 is distorted at its central portion, as indicated at 31, the latter portion resting upon a centrally projecting portion 68 at the upper side of the plug 21 and suitably spaced and insulated from the contact pieces 61, 61*. Side portions of the contact strip 31 adjacent the raised central portion .31 are disposed in recesses 69. 69 at the upper side of the plug 21, as indicated, so as to assist in maintaining suitable alinement and positioning of the contact strip; and this strip is secured in operative position by means of an axially disposed se curing bolt 34 which passes through an aperture in the upset portion 31 of the strip and has its lower end engaged by the cap nut which, when secured in operative position, secures the bolt in mechanically and electrically operative position, with the head of the bolt bearing upon the portion 31, and the cap nut 35 serving as a central terminal contact for the plug 21.

The circuit through the heatin; unit as disclosed in Figs. 5, 6 and 7 may be traced from the terminal screw shell 22, through bent-over portions 27 thereof beneath the heads of securing screws 25, 25, through the latter, terminal pieces 61, 61, and heating such position as to cause -movement upward of the contact bridging piece 38 thus freeing the terminal ends of the heating elements and permitting transverse movement thereof from or to operative position, all as indicated generally in the description of the device of Figs. 1, 2 and 3.

The device shown in Fig. 8 is structurally similar to that shown in Figs. 5, 6 and 7, except that in the modification shown in Fig. 8, the two heating elements 37 and 37 are connected in series, rather than in parallel as in Figs. 5, 6 and 7, and the connections and terminals of the plug 21 are accordingly modified to accommodate for such series connection of the heating elements. As indicated, the securing screw 25 is not connected with the screw shell 22, but a conductive bridge 72 is disposed beneath the head of the screw .25 and the inner end of the terminal cap nut 35 on the securing bolt 34?, this bridge serving to conductively connect the terminal cap 35 to the securing screw 25. The upper end of the securing bolt 34 passes through and serves to mechanically secure the conductive strip 31 in operative position, but this securing bolt 34* is insulated from the strip 31 by means of a flanged insulating bushing 91 passing through an aperture in the off-set portion 31 of the strip 31 and having its flange between the upper side of the portion 31 and the lower side of the head of the bolt 34*. The operating circuit may be traced from the terminal shell 22, through securing bolt 25, contact piece 61, heating element 37, contact bridge 38, heating element 37, contact piece 61, securing bolt 25, conductive bridge 72,. to central terminal cap 35.

Heating elements of the device of Fig. 8 may be removed from and inserted to operative position in the manner described in connection with the device of Figs. 5, 6 and 7.

In the device shown in Figs. 9, 10 and 11, the heating elements 37 and 37 are connected in parallel between the circuit terminals of the supporting plug 21*, as in Figs. 5. 6 and 7; but the method of mounting the heating elements involves changes over those heretofore described. The upper face of the plug 21 has mounted in the recesses, 67, 67

at the upper face of the plug, supporting ductive material, the upper portion of each spring being turned toward the plug 21 and provided atits upper face with a contact strip 83 of suitable conductive material, the latter being united to theelements 71, 71 by rlveting, welding or the like, the upper strip or both strips being formed to present contact recesses 73 in which the lower ends of the heating elements engage in end abuttlng relation. The supporting portions of: the bowed spring elements are held in operative position by the conductive securing screws 25, 25, which also serve to conductively connect the spring contact elements to the bent-over portions 27 of the terminal screw shell 22. The upper terminal end of the securing screws may pass into an anchoring nut or a reinforcing piece disposed at the upper side of, and separate from or integral with, the base portion of the bowed spring elements, as indicated.

The upper terminal ends of the heating elements engage with a bridging contact piece 75, being in butt-end engagement with the walls of recessed portions 76 formed in. the bridging piece. The bridging piece 75 is held in position by means of a pair of diametrically opposed supporting rods forming side arms of a bail 7 8, these side arms, indicated at 78, being riveted over at their lower ends, as indicated at 79, into the preferably yieldable end portions of a supporting strip 81. The central portion of this supporting strip, is offset, as indicated at 81 the offset portion resting upon the central projecting portion of the supporting plug 21*, and the adjacent side portions of the strip disposed in recesses 69, 69 The supporting strip 81 and the supporting bail 78 carried thereby are maintained in operative position by means of the axially disposed securing bolt 3 1 which is held in position by the cap nut 35 which acts as a central terminal for the plug 21". As indicated, the bridging piece 75 has recessed portions at opposite sides within which recesses the side arms 78 of the bail fit. lVhile the contact bridge 75 may be secured rigidly to the bail 78, it is preferable that this connection be relatively loose and permit some adjustment to permit maintaining the desired mechanical and electrical engagement with the terminals of the heating elements 37, 37", even though there be some slight difference in the length of the two heating elements or the condition of their terminal portions. As indicated, the bridging contact 75 is suspended from the bail 78 by means of a rivet 82 which passes through an opening at the central portion of the contact bridge and permits a limited movement of the bridge on the securing rivet or the like.

It will be ap arent that the operative circuit through die device shown in Figs 9,

10 and 11 extends from the screw terminal 22, through securing screws 25, 25, bowed spring contact 71, 71, and heating elements 37, 3'1 in parallel to bridging contact 75, thence through the arms 7 8* 0 the ball 78, in parallel, to the supporting strip 81, thence through the securing bolt 34, to the central termi-nal cap 35.

It will be apparent that the heating elements 37, 37 may be readily removed from or replaced in operative positiouby distorting the bowed spring supportm portions 71, 71 of the terminal contacts or the lower ends of the heating elements, above or with the resilient ends of the supporting strip 81, such distortion permitting the heating elements to drop so as to free the upper terminals thereof from the contact recesses of the bridging contact 75, under which conditions the heating elements may be readily removed or inserted in a transverse direction.

In the device shown in Fig. 12, the arrangement for supporting the heating elements 37, 37 is similar to that disclosed in connection with the device of Figs. 9, 10 and 11. However, the connection between the heating elements and the circuit terminals is different, in that in the device of Fig. 12, the heating elements are connected in series between the circuit terminals of the supporting plug 21*. This desirable result is secured by insulating the securing bolt 3& from the supporting strip 81 by means of an insulating bushing 91, and by insulating one of the securing screws, such as the screw 25, from the terminal screw shell 22, this latter securing screw 25*, being connected by a bridge 72 to the terminal cap 35, the bridge being preferably mechanically and electrically maintained in operative position against the cap 35 and the head of the securing screw 25*.

The operative circuit for the device of Fig. 12 may be traced from the terminal screw shell 22, through securing screw 25, contact elements 71, 83 heating element 37, bridging contact piece 75, heating element 37, contact elements therefor 83, 71, securing screw 25 and bridging piece 72, to the terminal cap 35.

A satisfactory material for the contact springs and pieces which are required to have sufiicient resilience to yieldingly maintain the heating elements in operative position is a tempered bronze or monel metal; and for the contact strips or other portions which are in immediate contact with the ends of the heating elements, aluminum for the lower operating temperatures, and an iron-chromium alloy, such as ascoloy, are quite satisfactory. The several materials mentioned for these purposes of heat resistance coupled with resilience and ability to maintain themselves without destructive oxidation or deterioration may be selected depending u on the required operating temperatures. owever, in this connection, it is of great advantage to utilize a heating element of the character described hereinabove wherein a heat-hardened substantially nonmetallie heating unit essentially composed of silicon carbide, with or without modifying elements, and having ends of increased conductivity, an especial effect of these highly conductive ends being to retain the metallic contact parts associated therewith at satisfactory operating temperatures.

It will be apparent that in accordance with this invention, a heating appliance is provided embodying one or more self-sustaining heating elements of the cartrid e type which are yieldingly and detachab y held in operative position upon a support in such a manner as to permit handling of the support with the heating elements mounted thereon, the combination constituting a unit which may be readily inserted in or removed from a reflector or other carrier.

It should be understood that it is not desired that the invention claimed be limited to the exact details of construction shown and described, for obvious modifications may occur to persons skilled in the art.

It is claimed and desired to secure by Lettcrs Patent:

1. In an electrical heating device, in combination with an insulating support adapted for insertion in and removal from a holder, a pair of concentrically arranged circuit terminals carried by said support, a contact element mounted on said support axially thereof and provided with a contact recess and connected to the outer one of said circuit terminals, a self-sustaining resistance heating element mounted on said support with one end thereof in engagement with said contact element and extending away from said support, a contact element in engagement with the remote end of said heating element, and spaced, yielding, conductive supporting elements mounted on said support ,and cooperative with said remote contact element for supporting the latter and maintaining said heating element in operative position, said supporting means being connected to the inner one of said circuit terminals.

2. In an electrical heating device, an insulating support adapted for insertion in and removal from a holder, a pair of concentrically arranged circuit terminals thereon, a recessed contact element mounted at one end of said support, a self-sustaining resistance heating element having one end thereof in engagement with and within the recess of said contact element and extending away therefrom, a contact element in engagement with the remote end of said heating element, and opposed, resilient and conductive supporting arms mounted on said insulating support and cooperative with said remote contact to yieldingly position the same and to resiliently support said heating element in operative position with its terminals in yieldii'ig butt-end engagement within the recesses of said contacts and to conductively connect said remote contact to the inner one of said circuit. terminals on said support.

3. In an electrical heating device, the combination of an insulating support having a plurality of circuitterminals concentrically arranged thereon, a recessed contact element mounted at one end of said support, a self-sustaining heating element having one terminal thereof in engagement with said recessed contact portion, a second contact element disposed at a point remote from said support and .in axial alincment therewith, and yielding supporting means for said second contact, saidsupporting means comprising a plurality of spaced arms associated with said second contact and mounted upon said plug through the intermediary of a securing bolt arranged substantially axially of said support.

4. In an electrical heating device, the combination of an insulating support, a pair of spaced contact elements carried by said support. apairot' spaced supporting arms mounted on said support, a bridging contact carried by the ends of said supporting arms remote from said support, and a pair of selt sustaining resistance heating elements yieldingly and detachably mounted in operative engagement with the contact portions on said support and said bridging element.

5. In an electrical heating device, the combination of an insulating support, a pair of spaced contact elements carried by said support and provided with recessed contact portions, a plurality of spaced supporting.

arms mounted on .said support, a bridging contact carried by the ends of said support mg arms remote from said support and provided with recessed contact portions, and a pair of self-sustainingresistance heating elements yieldingly and detachably mounted in operative engagement with the recessed contact portions on said support and said bridging element. with the ends of said heating elements in end-abutting engagement with the walls of said contact recesses.

6; In an electrical heating device, the combination of an insulating support, a pair of spaced elements having contact portions and carried by said support, a plurality of spaced supporting arms mounted on said support, a bridging contact carried by the ends of said supporting arms remote from said support and provided with recessed contact portions, and a pair of self-sustaining resistance heating elements extending away from said support and yieldingly and detachably mounted in operative engagement with the contact portions on said suport and said bridging element, said bridging element being adjustable relative to said so porting arms.

In an electrical heating device, the combination of an insulating support having a pair of concentrically arranged circuit terminals thereon, a pair of spaced contact elements carried by said support, a plurality of spaced supporting arms, means for mounting said arms in operative position, said mounting means including a securing screw disposed axially of said support and connected to a central one of said terminals, a bridging contact carried by the ends of said supporting arms remote from said support, and self-sustaining resistance heating elements yieldingly and detachably mounted in operative engagement with the contact portions on said support and said bridging contact element.

8. In an electrical heating appliance, an insulating support, a terminal contact mounted on said support, a. self-sustaining resistance heating element having one terminal in engagement with said contact, a sec- 0nd contact in engagement with the other terminal of said heating element, and a pair of supporting elements serving to adjustably support said second contact in operative position, the supporting means for one of said contacts including a yielding resilient portion serving to maintain said heating element in operative position with its terminals in yielding engagement with said contact;

9. In an electrical heating appliance, an insulating support, a plurality of terminal contacts, one of said contacts being disposed adjacent said insulating support, self-sustaining resistance heating means having one terminal in engagement with said contact, a second contact remote from said support and in engagement with the other terminal of said heating means, said heating means and said contacts being symmetrically arranged about the axis of said support, and a pair of supporting arms mounted upon said insulating support and mechanically and electrically connected to said second contact, said supporting arms serving to support said second contact in operativeposition, and the supporting means for one of said contacts including a yielding resilient portion serving to maintain said heating means in yielding mechanical and electrical engagement with said contacts.

In witness whereof T an my signature

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