US2659799A

US2659799A - Electric heating element

Info

Publication number: US2659799A
Application number: US185835A
Authority: US
Inventors: Ireland Murray
Original assignee: McGraw Electric Co
Current assignee: McGraw Electric Co
Priority date: 1950-09-20
Filing date: 1950-09-20
Publication date: 1953-11-17
Anticipated expiration: 1970-11-17

Description

Nov. 17, 1953 M. IRELAND ELECTRIC HEATING ELEMENT Filed Sept. 20. 1950 INVENTOR ATTORNEY latented Nov. l7, 195 3 UNITED STATES PATENT OFFICE ELECTRIC HEATING ELEMENT Murray Ireland, Elgin, Ill., assignor to McGraw Electric Company, Elgin, 111., a corporation of Delaware This invention relates to electric heating elements for toasters the like, and is particularly directed to an improved construction for securing the heating wire windings.

The electrical resistance wire windings, usually wire ribbon, of heating elements, particularly when heating are likely to sag away from the surface of the supporting form of the heating element. Various proposals have heretofore been made for avoiding this difficulty but, so far as I am aware, none of such proposals have been found practical.

The general object of t..-e present invention is to provide a heating element having the heating windings supported against sagging through a securing construction which will not injure the windings or interfere with the heating effect thereof, and which is adapted for rapid production and otherwise acceptable for commercial employment.

According to the invention the windings of a heating element are anchored to the supporting form by individual securing means in the form of individual thin wire staples adapted to make substantially only point or thin line contact with the heating ribbon or other wire, and further arranged to make merely sliding contact with the wire so as to avoid injury thereto during the course of installation. Because of the close spacing usually employed between the windings of heating elements the use of staples presents a difficulty in that if the staples be of sufficiently small size to avoid short circuiting of adjacent windings they are likely to injure the heating wire in the course of installation. According to the invention it is possible to use staples of a size which can be employed without injury to the wire and which would cause short circuiting between adjacent windings if applied crosswise of the windings. To avoid the latter condition the staples are arranged in inclined relation to the windings. This permits the staples for the windings to be arranged in a line and permits installation of the staples by rapid machine methods.

The invention will be understood by reference to the accompanying drawing. In such drawing:

Fig. l is a front view of an electric heating element according to the invention;

Fig. 2 is a corresponding rear view thereof; and

Fig. 3 is an enlarged sectional view taken at one of the securing staples.

As conventionally, the flat electric insulating form it may comprise sheet mica, but it also 'may comprise other suitable insulating material.

taining relatively closely spaced notches i2 and i3. Metal eyelets l4 and I5 are provided in the lower portion of the form for anchoring the ends of the ribbon and providing electric terminals therefor. At the top of the form is metal clamping strip 16 having upstanding posts ll and i8 adapted for the support of the heating element. Staples l9 secure the individual windings of the ribbon against the form and will hereafter be more fully described.

At the opposite edges of the form are notches i2 and i3. As conventionally the spacing of adjacent notches may vary, preferably being more closely spaced in the lower area of the form to provide a greater concentration of heating wmdings of the ribbon therein than in the upper area. The IlbbOll between windings extends through adjacent notches i2 and I3 at the opposite edges of the form and is anchored by loop formations 20 and 2| at the back side of the form, as shown in Fig. 2. Such loop formations are shown as containing an axial twist, but this is not a part of my invention and is merely optional.

Staples l9 are of thin wire. The yoke thereof bridges an individual WlIldlIlg of the heating ribbon or other wire II and the staple legs 22 extend through the form and are bent in anchoring engagement with the opposite face. As prevlously pointed out, it is desirable that the staples be applied so as not to deform the wire. A light sliding contact between the staple and the heating wire is round suitable for securing purposes. Accordingly, the staples must not be tightly clenched as in the case or other usages.

It will be noted that the staples are relatively wide in relation to the spacing of the windings, and that if applied crosswise they would cause short circulting. Accordingly they are arranged at a diagonal to the direction of the windings. With such orientation the staples may be disposed in a single line extending vertically to the heating element and transversely to the direction of the windings. The particular heating element illustrated and described has the windings all disposed on the front face of the form. Certain leads of the wire, as shown in Fig. 2 are disposed at the back of the form. These also may be socured by staples 23 and 24 extending from back to front through the form in positions which will not short circuit the windings. It will be understood that the invention i also applicable to heating elements having windings on both sides of the form.

Normally a single staple for each winding provides suilicient support, in which case the staples will preferably be located substantially midway between the opposite edges of the form. Where required, however, a plurality of staples may be employed at spaced point along each winding.

I claim:

1. An electric heating element comprising a flat electric insulating form and an electric resistance wire having spaced straight windings extending across the form and wire staples Wider than the wire of the winding and contacting said wire securing the intermediate portions of the individual windings against one face of the form and extending through and being anchored at the other face of the form, said staples extending diagonally to the direction of the windings and adjacent staples lying in spaced relation, and the legs of each staple being spaced by an air gap from the winding secured by the staple.

2. An electric heating element comprising a flat electric insulating form and an electric resistance wire having spaced straight windings extending across the form and wire staples wider than the wire of the windings and contacting said wire securing the individual windings against one face or the form and extending through and being anchored at the other face of the form, said staples extending diagonally to the direction of the windings and said staples being arranged in a common line transverse to the direction of the windings and adjacent staples lying in spaced relation, the legs of each staple being spaced by an air gap from the winding secured by the staple.

3. In an electric heating element, in combination, a sheet of mica having notches along a pair of opposite edges, a resistance wire lying across one face of said sheet of mica in spaced spans of straight wire supported by engagement of looped portions of said Wire with said notches, and a row of wire staples wider than the wire of the spans extending through said sheet and clinched thereon, each of said staples of the row straddling one of said spans intermediate its ends for supporting it and with the legs of each staple being spaced by an air gap from the span which it holds, said staples lying at an acute angle to the wire of said spans and in parallel relation with each other whereby to provide spacing of the staple holding each span from adjacent spans and from the staples holding said adjacent span independently of the spacing between each span and said adjacent spans.

MURRAY IRELAND.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,359,400 Lightfoot Nov. 16, 1920 1,474,887 Bridges Nov. 20, 1923 1,480,084 Lamb Jan. 8, 1924 1,565,539 Woodson Dec. 15, 1925 1,726,757 Murphy Sept. 3, 1929 2,040,369 Fischer May 12, 1935 2,243,993 Watson June 3, 1941 2,419,355 Koci Apr. 22, 1947 2,503,601 Tice Apr. 11, 1950 2,503,357 Ames May 23, 1950 2,522,724 Scharf Sept. 19, 1955 2,570,376 Quist Oct. 9, 1951