US2370767A - Electric boiling plate - Google Patents

Description

March 6, Q B. BACKER 2,370,767

ELEGTRI C BOILING PLATE Filed Jan. 28, 1942 INVENTOR:

Fi .5 5 1; v flag. 41.

Patented Mar. 6, 1945 ELECTRIC BOILING ,PLATE GhriStianzB; Backer, Belmont, Mass.

Application January .28 In Canada. Fe

1942; Serial No.1428,4.85. I. bruary 19, 1941'.

3 1Claims.; (01.219-37)" This invention relates to boiling plates for electric stoves and. more particularly to the radiant light weight type of boiling plate consistingof one or several (generally two) tubular. heating elements bent into suitable shape and supported on a light frame and having a heat. reflectorin the form of a sheet. metaldishmounted beneath.

the tube elements.

Presently available boiling .plates ,of .the type referred to have their elements permanently fixed into the terminal box (if. any) as by brazing,

pressing or kneading the. metal of.,.the terminal box around the tube elements, at .the points.

where they enter the .box, in order to. provide a water-tight joint between thetubes and terminal box. It will be apparent that such aboiling plate. does not permit thereplacement of a burnt out.

tube withoutthe risk-f seriouslydamaging. the

remaining good tube, as well as the terminal..box,:

porcelain block and other parts. vIn any ,case, the replacement of the burnt out tube cannot be efi'ected in the field, but the whole boiling plate must be removed to a repair shop. In many instances, the entire plate must be discarded.

Moreover, frequent burn-outs at the.tube terminals of presently .available boiling plates occur.

due .to inadequate protection .of such terminals.

and their related parts bythe terminalbox.

An object of the invention is. to. provide a tubue.

lar element boiling plate. ;of such design that. should one of the heating tubes burn out, it. may, be easily removed in thefield and replaced with-a new tube without damage to other .parts of .the

plate.

Another object is ,to provide a. terminal box for the tube terminals of a boiling plate of such design that over-boiling liquids coming into contact with the box will not reach the terminals and thereby damage the electrical insulation thereof.

A further object is to provide a boiling plate of such design that the reflector dish may be easily removed for cleaning purposes.

The invention will be described with reference to the accompanying drawing in which,

Figure 1 is a plan view of a boiling plate in accordance with the invention,

Figure 2 is a sectional elevation,

Figure 3 is an elevation of the tube terminals and related parts in separated condition,

Figure 4 is a bottom plan view of the terminal box, and

Figure 5 is a further elevational detail view of the tube terminals.

Referring to the drawing, the boiling plate insembly screw 20 engaging a connecting post 2t eludes tubular heating elements I and 2 bent intosuitablev shape as. shown .in Figure 1 and mountedin pOsition on a spider frame .3 having suitable retaining notches. 4 therein to receive the tubes. The tubes contain theusual electrical elements 5 surrounded. by, insulation 6. The.

spider frame is carried by an. annular. support] mounted in the main framed. A heat reflector dish 9, havinga central. hole 10,. is. arranged vbelowthe spider frame and is also carried by the.

support 1.

Theflendsof the tubular elements are bent downwardly asv at; l l and I2 .forattachment to the. terminalbox, generally indicated at I3.v

The terminal. box comprises alight weight meta1 casing. I 4 .open. at thebottom to receive -a porcelain terminal block 15. The side walls of the casing areslightly outwardly flared and have a prominent. outwardly flared lip portion l6 extendingbelow the lower surface :of the porcelain block.v The top wall of. the casing is provided with four holes having upwardly extending nippl es l1 permanently fixed. therein and adapted to receive the fourends ll and-.12 of they tubular elements...Each of .the-endsH-and l2 have-a small. drip. cap l8 of inverted cuplshape perma-- nently attached thereto, as by brazing to-provide a water tight joint between thecap .and tubep It will be observed that the caps seat upon the-upper edges ,of thesnipples and .have -a deep outwardly flared skirt portion .l8'-. adapted to sheddrips and avoid the-possibility-of. the latterreaching the seating 'surfaces Theecaps-have beenshown as,beingformedin'pairs,.onefor each pair: of tube ends, butittwill. beeunderstoodwthat individual capsmay;bejemployem. The tube-ends and terminal box casing are securely assembled together by means of a clamp I 9 extending across the top of both pairs of caps and having an aspermanently fixed t0 the casing. It will be observed that tightening of the screw 20 causes a solid seating contact of the caps l8 with the nipples ll. Terminal wires 22 of the tubular elements enter recesses 23 in the porcelain block and are connected to the terminal strips 24 on glsie lower face of the block by terminal screws 26 of the power supply,

It will be apparent that, should it be necessary to replace a tubular element, it is only necessary to unscrew the assembly screw 20 and the two terminal screws 25 of the tube to be replaced. The tube ends are then free for withdrawal from the terminal box and the entire element readily removed from place in the plate. Anew tubular The strips are connected to the three wires element is then inserted and its ends conveniently assembled in the terminal box as previously described. The entire operation of removing a burnt out tube and inserting a new tubular element may therefore be performed in the field in a period of three or four minutes.

It will also be observed that drips from overboiling liquids reaching the tube ends and the terminal box will be readily shed by the long flared skirted portions of the caps I8 and the flared side wall and depending lip of the terminal casing, thus preventing such drips from coming into contact with the electrical terminals or wires. As is well known, this is a frequent occurrence in present day boiling plates and is a source of much trouble.

It will be understood that many variations in the structure described may be effected without departing from the spirit of the invention. Thus, for the sake of economy, the ends of one of the tubular elements may be permanently fixed. as by brazing, to the terminal box while the ends of the other element may be removably secured thereto in accordance with the invention. In this case, the ends of the inner tubular element would usually be fixed in place while the ends of the outer element would be removably secured in place, since normally the inner element has a much longer life than the outer element. The reason for such longer life is that the inner element is much longer and has a greater loading than the outer element in order to provide rapid boiling under medium load. This inner element will therefore have a much heavier heating wire. The uneven length of life is further aggravated by the fact that the outer tube must have about 20% higher loading per unit length than the inner tube in order to attain the same temperature on both tubes. Th result will generally be that the inner tube, although it is used more than the outer tube, will last perhaps two or three times as long as the outer one. In most cases of burnouts in this type of plate, therefore, it is the outer tube which must be replaced. In any event, in the embodiment of the invention just referred to, one would permanently fix the tubular element of normally longer lif and removably mount the other element in position.

I claim:

1. In a boiling plate for an electric stove having a frame and a three Wire power supply, means supporting the plate in the frame, a plurality of substantially tubular heating elements in the plate, a terminal box remote from said supporting 'means for connecting the elements to the power supply, said terminal box having a casing, and

means for fastening the ends of the elements to the casing including means for fastening the ends of at least one of the elements for detachment from the casing independently of the other element ends, said latter means comprising a plurality of tubular members carried by the box and each adapted to receive an element end, each end of said one element having aseating portion fixed thereto and adapted to seat on the end of a re- I spective tubular member, and means holding said seating portions in seated engagement on said tubular members comprising a plate engaging the seating portions and having a screwthreaded connection with the terminal box.

2. In a boiling plate for an electric stove having a frame and a three wire power supply, means supporting the plate in the frame, a plurality of substantially tubular heating elements in the plate, a terminal box including a casing remote from said supporting means for connecting the elements to the power supply, said casing having openings receiving the ends of the elements, nipples loosely encircling said ends and each having a liquid tight connection with the edge of a respective opening, an inverted cup-shaped cap fixed in liquid tight engagement to the ends of each element and having seating engagement with a respective pair of nipples, said cap having a depending outwardly flared wall encircling a respective pair of nipples, and means holding the caps in seating engagement on the nipples comprising a plate engaging the tops of the caps and having a screw-threaded connection with the terminal box.

3. In a boiling plate for an electric stove having a frame and a three Wire power supply, means supporting the plate in the frame, a pair of substantially tubular heating elements in the plate having downwardly extending ends, a terminal boxinclucling a casing remote from said supporting means for connecting the elements to the power supply, said casing having openings receiving said ends, tubular members loosely encircling said ends and each having a liquid tight connection with the edge of a respective opening, a cap fixed in liquid tight engagement to the ends of each element and having seating engagement with the pair of ends of respective tubular members, the cap on the ends of one element being separate from the cap on the ends of the other element, and means holding the caps in firm seating engagement with the ends of the tubular members comprising a plate engaging the tops of the caps and having a screwthreaded connection with the terminal box.

CHRISTIAN B. BACKER.

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