US1873053A - Electrical heating apparatus - Google Patents

Description

Aug. 23, 1932. H. N. SHAW i 1,873,053

ELECTRICAL HEATING APPARATUS O riginal Filed Sept. 5, 1925 Patented Aug. 23, 1932 UNITED STATES PATENT OFFICE HAROLD N. SHAW, OF NIAGARA FALLS, NEW YORK, ASSIGNOB '1) GLOBAB OORPOBA- TION, OF NIAGARA FALLS, NEW YORK, A CORPORATION OF NEW YORK nnnc'rnrcar. nm'rme urm rus Original application filed September 3, 1925, Serial No. 54,193. Divided and this application filed larch 7,

1928. Serial No. 259,674.

This invention relates in general to electrical heating apparatus, and it has more particular relation to certain classes of such heating apparatus embodying or utilizing improved means or devices for electrically and mechanically mounting or maintaining selfsustaining electrical resistance heating elements or units in electrically and mechanically operative position and condition in such apparatus. The present application constitutes a division of my copending application Serial No. 54,193, filed September 3, 1925.

In accordance with the present invention, electrical heating apparatus of improved design and construction and particularly adapted for use as hot-plates, cookers and the like and wherein the production of relatively. high operatingtemperatures may be desirable, is provided, such apparatus embodying or utilizing'self-sustaining resistance heating elements, andbeing especially adapted for use of such elements as are in the form of molded and heat-hardened bodies produced from a' composition containing carbon or a carbide,

particularly silicon. carbide, as an essential constituent, and the apparatus also embodying improved mounting devices for the heating elements which insure eflicient mechanica support for the latter and electrical connection thereof to a supply circuit.

As a particular feature of the present in- ;vention, electrical heating apparatus in accordance therewith embodies or utilizes a combined electrical connection and mechanical support for the resistance heating element,

the combined support and terminal being yieldingly urged to abut against the extreme end or ends of the resistance heating element with suificient pressure to satisfactorily insure the desired mechanical support of and electrical engagement with the heating element. An additional feature is that the terminal mounting permits ready insertion of the heating element to and its removal from operative position. Again, beneficial use is made of the fact that certain materials are particularly well adapted to afford desired mechanical strength and resiliency and to maintain satisfactory electrical contact with a heating ele- 'tion, and will be more Renewed January 7, 1932.

ment of this general character even when the latter and the associated portion of the contact or terminal are maintained at relativel high temperatures. Again, additional ad vantages, particularly in the matter of sustained eflicient life of the heating elements! and terminal mountings therefor, are secured by utilizing a resistance heating element invention: a

Fig. 1 is a sectional elevation,'in the plane ofthe line I'-I of Fig. 2, of one form of electrical heating apparatus embodying the pres: ent invention.

Fig. 2 is a partly sectionalplan view of the apparatus shown in Fig. 1.

Fig. 3. is a View similar to 1 showing an electrical heating device embodying a modified form of terminal mounting for the heating element.

Fig. 4 is a sectional elevation of another modified form of electrical heating device.

In accordance with the disclosure of Figs. 1 and 2, the invention is applied to an electrical heating device, which may readily be utilized as a hot-plate, broiler, or the like, comprising a substantiall box-shaped frame 10 having side walls 12 w ich serve as a general support for the heating elements. At points adjacent the upper edge of one of the side walls 12 of the frame, one or more conductive terminal bolts 13 are disposed, each of these bolts having its head 14 at the inner 24 spaces a nut 25, threaded on the bolt, from of-the bolt from the wall. An insulating washer 16 surrounds the bolt and bears against the outer side of the wall 12, a nut 17 being threaded on the outer end of the bolt 13and serving to draw the bolt into and secure the. same rigidly in operative position. A line connection 18 is secured in position between the nut'17 and a clamping nut19 on the bolt 13. The inner end of the head '14 of each bolt is formed as a recessed or cupshaped contact, or has a recessed contact piece secured thereto, by welding or otherwise, for the reception of the terminal end of a self-sustaining unitary heating element 20, here shown of bar or rod shape, and it may have its ends of somewhat rounded or convex shape, thusfacilitating any necessaryadjustment of the terminal end in the recessed contact while insuring required con- Y bushings 21 mounted therein and being preferabl sufliciently large to permit the heating e ement to be wholly free of the bushing to a slight extent. This wall 12 is shown asprovided with an additional aperture at I a point intermediate a pair of the apertures carrying insulating'bushings. 21. A bolt 22 passes through this intermediate aperture, with the head of the bolt at the inner side of and insulated from the wall by a flangeon an insulating bushing 83 which passes through the wall and serves to insulate the bolt 22 from the wall. An insulating washer the wall, and the nut serves to draw the bolt into and maintain the same in fixed position upon the sidewall 12.

. The outwardly extending portion of the bolt 22 is rovided with a nut 26, serving as an adjusta le abutment or seat, along with a second adjustable nut 27; and betweenthe two nuts 26 and 27, a resilient contact ele ment or terminal 29 is mounted in position, the point ofmounting on the bolt 22 being adjustable byadjustment of the nuts 26, 27. As indicated the contact element or mounting 29 extends in opposite directions from the supporting bolt 22 and comprises a relatively stiff and resilient, and heat-resistant conductive supporting element 31 of material such as Monel metal or an iron-chromium alloy,

. and an inner leaf or strip 32 of more highly conductive metal, such as aluminum, or an aluminum-nickel alloy,'-and preferably welded, riveted, or otherwise secured to the strip 31. The body portion of the mounting or terminal 29, at each side of the supporting screw 22, may be bent or otherwise suitably formedso as to bring the ends thereof in desired operative position and preferably relatively close to the side wall 12 of,the supporting frame at points in line with the apertured bushings 21 through which the ends of the resistance elements 20 project. The inner side of the mounting or terminal element 29 at the terminals thereof, at least the contact strip 32, is formed with sockets or recesses, as indicated at 34, which may be of more or less generally conical sha e and of such size as to easily and adjustaEly receive the'terminal ends of the resistance heating elements 20, the other end of each of which is in engagement with the recessed con-.

tact associated with the head 14 of the corresponding bolt 13.

A line terminal 35 is maintained in electrical connection with the terminal mounting 29 through the holding nut 27 and a clam ing nut 36 adjustable.on the bolt 22.

carrying the terminals 18 and 35 out to a suitable switch or contact-maker, any desired combination of series or parallel connections, and consequent varying heating effects, of the resistance heating elements 20 maybe secured.

The leaf strip 32 may extend throughout the full length of the resilient supporting strip 31, as indicated, or it may extendionly .part way, after the fashion of the contacts of the apparatus shown in' Figs. 3 and 4', de-

scribed hereinafter. The terminal element 29 ispreferably reversely bent to some extent for the purpose of increasing its spring effect or ability to exert pressure on the terminal end of the heating element in the general direction of its axis; and the position of this terminal element on the supportin bolt 22 and the strength and resilience of th1s element, especially the resilient supporting strip 31thereof, are so selected that the recessed contact portions of the mountin are caused to engage the extreme ends 0 the heating elements with the required pressure exerted'in the direction of the longitudinal axes ,of the heating elements, to yieldingly maintain the desired electrical contact tween the ends of the heating elements and the recessed contacts 34 and 14 and also to mechanically support-and maintain the heating elements in operative position throu h the butt-end engagement thereof with t e recessed contact portions 14 and 34, and preferably free of any support except that of the t'ermin'alcontact elements 29 and 14.:

The heating element 20 may readily be removed from operative position, preferably after loosening the nut 27 to a slight extent, by flexing the resilient mounting element against its normal bias until itclears the end tion wherein the heating) of the heating-element. The mounting may then be swung about the bolt 22 to a posielement may be drawn out through the ushing 21, and a replacement inserted to position, after which the mounting may againbe swung to and secured in its operative position, as shown. Suitable supporting means are associated with the upper edges of the side walls 12 of the supporting frame for mounting a plate, perforated cover, grate or grille 38, a convenient methodbeing to form recesses pro viding seats 37 upon which the cover, grate or grille may rest or be supported, as indicated, or in any desired manner. A rear or lower wallt39 may serve as a part of a protective enclosure, and in some cases, with suitable curvature, it mayhave the function of a reflector, of more especial utility when the device is-set on edge. It'may bedesirable to provide apertures in this ventilation purposes.

The construction shown herein may be modified to a considerable degree, as desired, as by placing the contact mounting 29 and the shank of' its supporting bolt 22, with the contact retaining nuts thereon, on the inside of the wall 72; but the arrangement illustrated may be considered more desirable where the maintenance of a low temperature at the contact terminals 34 is particularly desired. Likewise, individual spring contact terminals or mountings of the same type as the element 29, but with a single contact portion 34, may be substituted for the bolts 13 with their contact heads 14. And the rigid butt 'terminal contact or mounting 14 may be replaced by a spring butt terminal similar to the terminal contact or mounting 29. p i

In accordance with Fig. 3,- features of the inventionare shown as applied to a heating device of the general class'heretofore described and shown in Figs. lyandf2, but wherein the contact terminals may be wholly at the outer side of the supporting frame 41. Opposed side walls 42 of the frame are "provided with alined apertures in which are mounted insulatingbushings 43 ofsuch size that resistance heating elements 44 passing therethrough are readily maintained spaced from the walls thereof. The contact terminal used is indicated generally at 45, and consists of a, relatively straight, stiff and resilient supporting leaf r strip 46, in the form of a single lamination or multiple laminations, ofheat-resistant conductive material,

tur'ein the leaf and insulatedtherefrom and, threaded into an aperture in the wall 42, the

of the character described hereinabove.

This leaf spring is supported adjacent its lower end by a holding screw 47 having a threaded end and passing through an aperleaf being insulated from the wall 42b a flanged insulating bushing 48, and. an insu atenga ement t wall 39 for g ing washer 49 separatin the spring leaf and the head of the screw On the inner side of the resilient leaf 46 is a conductive contact strip or leaf 50 either single or laminated and preferably 0 amateral suitable for aconductive contact exposed to heating, and preferably riveted or welded, or bolted, as indicated, at its lower end to the supporting leaf spring 46, by means of connection screws 52 and securing nuts thereon. One or both of these connection screws52'may serve as the terminal for a line connection. At its upper end, the contact strip 50 is recessed at 53, in generally conical form,'to produce an engagement or contact portion for adjustably. receiving and mechanicall and electrically engaging the end, prefera ly somewhat rounded or convex, of the heatin element 44 through butt-end erewith. By suitable design of the contact element 45 as to strength and resilience of the supporting ,leaf spring 46 and the mounting of the same and its contact strip 50, and selection of the length of the heating element 44, these contact elements are caused to 'efi'ectively fully support and yieldingly maintain the heating element, through butt-end engagement therewith, in normalopera-tive position with the desired electrical engagement between the parts. The resistance heating elements 44 are preferably of the type described hereinabove, and protrude to a slight extent beyond the side walls 42 of the supporting frame. To replace a heating element 44, one or both of the terminal mounts 45, after any necessary loosening of the screw 1 47, are distorted against the normal bias sufliciently to withdraw the recessed contact portion 53 from one end of the heating element, the mounting being then swung about its supporting screw 47 so as to being drawn out through the adjacent aperture in the wall 42. With a replacement element in position, the mounting 45 can be permit the heating element position through flanges on the plate secured to the side walls 42. This plate 57 may be plane or suitably shaped to act. as a reflector of heat raysfrom'the heating element 44.

.- In the modification disclosed in'Fig. 4, a.

base 61,

of metal or insulating material, is carried by an enclosing box-like frame 63.

Contact terminals "64 are mounted on the.

support 61 adjacent the. sides thereof, and

include a relatively stiif and resilient leaf spring element 65 of heat-resistant conductive material, such as Monel metal or an ironclgrommm alloy, having its lower end bent ill . leaf spring 65. The bolt .66 is insulated from the base 61 by a bushing 67 having a,

flange at its lower side bearing against'the lower face of the base. A clamping nut 68 secures the bolt 66 and thus the terminal mounting 65 in operative position on the base. A line connection 70 may be secured in position on the bolt 66 betwcenthe nut 68 and a clamping nut 69. i

A contact strip 71 of suitable conductive material, as described hcreinabove, is secured, by riveting, welding or otherwise, to the supporting leaf or strap spring 65. The inner side of the contact strips 71 at the upper ends thereof, and, if desired, the corresponding portion of the supporting leaf spring 65, are provided with concavities or recesses, as indicated,for the adjustable reception of the ends of the resistance heatingelements 74 which have but-end engagement with the v alls of the recesses.

At a point intermediate the contact terminals 64, an upright support 76 is secured upon the base 61, this support being shown as of conductive material suitably insulated by a separator 77 from the base 61. The upright support76 may be secured in position by ascrew 78 passing through the base or frame 61 and threaded into the lower end of the support, the head and shank of thescrew being insulated from the base 61 as by means of a flanged insulatingbushing 79. There is mounted on the upper, end of the support 7 6 a conductivebloek 81 of suitably heat-resistant material, the same being provided with a suitable number'of recesses intended for the reception of terminal portions of heating element 74 which have butt-end engagernent with the walls of therecesses, the opposite ends of the heating elements being supported by and in yielding and releasable engagement with the terminal mountings 64. he terminal mountings 64 are so designed,

especially the resilient pressure springs '65 thereof, as to cause the heating elements 74 to be effectively supported in osition between'the conductive strips 71 o the mountings and the contact block 81, with the re quiredpressure to insure secure and eflicient yielding mechanical support of the heatingelements and efiicient yielding electrical engagement between theterminal mountings and the ends of the heating elements through butt-end engagement therewith. Any heating element may be readily removed and replaced by distorting the terminal mounting 64 against its normal bias suificiently to permit the end of the heating element to be' 78 as one line terminal, the heating elements may be connected in parallel to the supply line. With such a line connection and suitable switching arrangements, the heating elements may be connected at will either in series or in multiple between the supply line terminals, and corresponding desired heating effects may be thus secured. If desired, the

terminal mountings 64 may be mounted on the side walls 63 of the frame. Also, these terminal elements may be mounted on the outer side of the side walls 63, with the contact recesses disposed opposite apertures in such walls, 1n a manner apparent from the disclosure" of Figs. 1, 2 and 3. When the desired'electrical heating effects permit or require it, the intermediate contact piece 81 and its support may be removed, and a single heating element may be supported in operative position between the two contact terminals 64.

As indicated, the conductive terminal mountings described hereinabove include means for resiliently or yieldingly supporting the heating element and maintaining the desired electrical connection from a line ci'r-" cuit to the ends of the heating element, wholly through butt-end engagement between the heating element and the terminal mountings; and thisresilient effect may be present in one or both of the terminal mountings. Satisfactory resilient and heat-resistant materials for producing the desired resilient engaging and supporting effects in the terminal mountings are tempered steel, or an iron-chromium alloy, such as ascoloy, Monel metalor suitable bronze; and likewise, with these resilient parts of suitable cross-section, they serve efiiciently. as a portion of the electrical path through the terminal mounting.

The resistance heating elements 20, 44, 74,

, are preferably unitary, self-sustaining, molded andheat-hardened composition products wherein a carbonaceous material, such as sili-- con carbide, is the principal constituent. Certainheating elements of the preferred characte'r are known in the art, the same being composed of silicon carbide as an essential eonstltuent, with or without one or more modifying substances for altering mechanical or electrical characteristics of the final product. The preferred heating element comprises a heat-producing'body portion and integral terminal portions of the same crosssectional area as the body portion but of such different composition as to have greater corrdgctivity and less heat-producing efiect than the body portion. This condition of more highly conductive terminals insures that portions of the metallic terminal mountings in electrical and mechanical engagement with' the ends of the heating element are maintained in satisfactory operating condition during a long life.

Where the operating temperatures of the heating appliance are relatively low, the re; cessed contact portion of the terminal mounting may be of aluminum, or an alloy thereof, such as aluminum-nickel, which does not oxidize or scale to a distinctive extent under the circumstances, it probabl forming a relatively thin oxide film whic does not build up or increase appreciably after being once established. However, where temperatures produced are higher or approach or exceed 'the melting point of aluminum, Monel metal,

a nickel-copper alloy, and iron-chromium or iron-chromium-nickel alloys, give desirable operating results. Aluminum alloy contacts for' electrical resistors are described in an applicatig si by John A. Boyer, U. S. Serial No. 386,9 ,6 ed August 19,1929.

The desired yielding but-end contact relation between the contact portion of the termlnal mounting and the end of the heating element is secured through the resiliency and normal bias of the terminal mounting ele-. ment, the contact portion of which is movable about its fpoint of sup ort due to the s ring effect 0 a portion 0 the mounting.

ertam desirable results as to movement of the contact portion of the mounting may be secured in other manners, such as pivoting the mounting elementfat its point of support, or otherwise guidin the contact portion for substantially straig t line movement along the axis of the heating element; and the normal biasing of the contact portion to secure the desired movement thereofmay be secured 1n varymg degrees through otherv forms of springs, gravity, and the lik Desirable results may be secured by spraying under high pressure a coating of finely divided conductive particles on the contact portion of the metallic supporting element, after thoroughly cleaning, as by sand-blasting, the latter. Likewise, desirable results may be secured by depositing a similar thin sprayed metal coating on theextreme end of the resistance element, for the purpose of establishing a satisfactory initial electrical enga ment between the parts, thus assisting in quickly establishing the desired normal operating condition of the contacting part.

The present invention is especially concerned with the provision of apparatus capable of commercially satisfactory and eflicient operation at temperatures corresponding-to a glowing condition of the resistance heating element; and electrical heating appliances embodying features of the present invention,

relatin to the electrical and mechanical mountlng of the resistance heating element as, described hereinabove .are capable of giving extremely satisfactory results and efiicient operation at temperatures up to as high as and even beyond 2,500" F. i

It should be understood that the invention set forth herein is not limited to the exact details of construction and operation described, for obvious modifications may occur to persons skilled in the art; and it is desired that the claims cover such various modifications within their scope as may occur to those skilled in the art. I

7 It is claimed and desired to secure by Letters Patent:

1. In an electrically heated appliance, a support having apertured side wall portions, a recessed contact in alinement with an aperture in a side wall portion and having a yielding and resilient support, a second con tact 'on the opposite side of the last mentioned side wall portion, and a rod-shaped electrical resistance heating element passing through the aperture in the last mentioned side wall portion and yieldingly mounted for direct heat transmission in electrically and me- -chanically operative position between said contacts through the yielding direct butt-end engagement of said first contact upon an end of said heating element.

2. In an electrically heated appliance, a support having aperture'd side wall portions, a pair of recessed contacts in alinement with apertures in said side wall portions, each of said contacts having a yielding and resihent support therefor, and a rod-shaped electrical resistance heating element passing through two of said apertures and yieldingly mounted for direct heat transmission in electrically and mechanically operative position between said contacts through the yielding direct butt-end engagement of said contacts on tlie ends of said heating element.

' 3. In an electrically heated appliance, a support having aperturedside wall portions, a recessed contact in alinement with an aperture in a side Wall portion and having a yielding and resilient support mounted on the outer sideofsaid side wall portion, a second contact, and a rod-shaped electrical re sistance heating element passing through said last mentioned aperture and yielding ly mounted for direct heat transmission in electrically and mechanically operative position between said contacts through the yielding direct butt-end engagement of said first contact upon an end of said heating element;

4. In an electrically heated appliance, a

support having apertured side wall portions,

a pair of recessedcontacts in alinement with apertures in said side wall'portions, each of said contacts having a yieldingand resilient support therefor mounted on the outer sides of said'side wall portions, and a rod-shaped electrical resistance heating element yieldingly mounted in electrically and mechanically operative position between said contacts through the yielding direct butt-end engagepassing through at least one of said apertures and yieldingly mounted for direct heat transmission in mechanically and electrically operative position between and in direct buttend engagement with pairs of said contacts, one of each pair including a resilient support, and the contacts in engagement with the corresponding ends of adjacent heating elements being connected in series.

6-. In an electrically heated appliance, a support having opposed side wall portions, one of said wall portions being apertured,

7 terminal contacts carried by said support,

one of said contacts being disposed on the outer side of said apertured wall portion and including a recessed portion in alinement with the aperture in said wall portion, and a resilient conductive portion integrally connected at one end to said recessed portion a and mounted in position at its 0 posite end on said wall portion, and a rod-s aped elec-- trical resistance heating element with its body portion disposed between. said wall portions and having one end projecting thropgh the a erture in said wall portion, said heating e ement being yieldingly mounted in mechanically and electrically operative position at least in part through the forcible but yielding butt-endengagement of said recessed contact upon the end of said heating element. i v

In an electrically heated appliance, a support having opposed side walls one of which is apertured, terminal contacts carried by said support, one of said-contactsqbeing' disposed at the outer side of said 'aperturedwall and including a recessed portion in almement with the aperture in said wall, and a resilient portion upon which said renon-metallic resistor rod mounted below sai late, a bolt whose head abuts the inner surat its upper side, an integral self-supporting ace of an end wall of the frame and whose threaded portion extends outside. the frame-p79,

a resilient contact arm rotatable about-said bolt outside of said frame and havin -a con tact recess adjacent an end thereof or-supporting said resistor rod in 'electricali-a'nd mechanical engagement by butt-end pressure of the resilient member, an aperture in said end wall through which the resistor rod ex-- tends, a second recessed contact for the other I end of the resistor rod mounted on the opposite end of the frame from the first-mentioned end wall, and .means for adjustabl S11 porting said resilient contact'arm w ere yi the resistor rod may be removed through the aperture in the end wall immediately after distortion and rotation of said resilient arm.

9. The electrical heating appliance described in claim 8 in which the rotatable resilient arm carries a lurality of contacts and theadjacent end 0? the frame has a corresponding number of similarly spaced apertures, while the opposite end of the frame supports a corresponding number of similarly s aced contacts, the rotatable resilient mem r being so mounted that by distortion and rotation it may hold a plurality of resistor rods in mechanical and electrical engagement by butt-end pressure on the ends Y of the resistor rods.

In witness whereof I afiixmy signature hereto.

HAROLD N. SHAW.

cessed portion is mounted,.said resilient por' tion being mounted at one end on said wall, and a self-sustaining, non-metallic resistance heating element having terminal portions more highly conductive than'the body portion of the element and having a terminal portion of increased conductivity extending through the aperture in said well and into engagement with the apcessed contact on the outer side of said wall; said heating element being yieldingly maintained in position through d1rect butt-end engagement there- -of withsaid'contacts, with said resilient mounting of said outer contact urging the latter nto forcible but yielding engagement w1th the extreme end of said heating element.

8. In an electrical heating appliance, a.

supporting frame having an apertured plate

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