US1360452A - Electric heater - Google Patents

Description

W. A. SHARPE.

ELECTRC HEAER.

APPLICATION mw JAN. 2e, 1920.

Patented Nov. 30, 1920.

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5MM Mgr ,Luf- ORNEY PATENT OFFICE.

WILLIAM A. SHARPE, 0F DETROIT, MICHIGAN.

ELECTRIC HEATER.

Application led January 26, 1920.

To all whom 'it may concern:

Be it known that I, IVILLTAM A. SHSARPE, a citizen of the ITnited States, and residing at Detroit in the county of Wayne and State of Michigan, have invented new and Improved Electric Heaters, of which the following is a specification,

This invention consists primarily in a novel electric heating element formed by cutting it from a thin rolled ribbon of proper metal` preferably an alloy of iron and nickel, and consists specifically in mounting this flat thin heating element, properly insulated` against the heat transmitting surface of an electric heater so that maximum heating effect is obtained.

This invention comprises a heating element cut from a thin rolled ribbon of metal, which has high resistance to electric currents` in such a manner as to constitute a thin serpentine structure.

It further consists in so cutting this element that it consists in a series of substantially parallel portions at right angles to the fiber or grain of the ribbon which are connected by substantially semi-circular portions of substantially the same resistance as the transverse portions.

It also consists in a fiat radiating surface, a thin sheet of non-conducting material such as mica flat against the radiating surface, my improved flat serpentine heating elcment, and non-conducting means to press the heating element toward the radiating surface.

It also consists in the details of construction illustrated in the accompanying dra'wing and particularly pointed out in the claims.

In the accompanying drawing, Figure 1 is a side elevation of a motor vehicle showing the wiring adapted for a heater embodying my improvements when attached to the radiator. Fig. 2 is an elevation of a heater with the cover removed. Fig. 3 is a section on the line 3-3 of Fig. 2 on a larger scale. Fig. 4 is a section on the line 4 1 of Fig. 3. Fig. 5 is an elevation of a connecting block. Fig. 6 is a front elevation of a radiator showing a plate which serves to attach a heater thereto.

Similar reference characters refer to like parts throughout the several views.

Electrieheating elements are usually in the form of round and flat wires and sometimes in the form of narrow tapes. The

Specification of Letters Patent.

Patented Nov. 30, 1920.

Serial No. 353,987.

present element is a thin serpentine structure, preferably in the form of a' series of parallel transverse parts .l (Fig. 2) which are connected at their ends by the semicircular parts 2. This element is cut bv shearing or punching from a thin rolled rilibon of metal which has high resistance to electric currents and which docs not readily oxidize, nickel-steel and nickel-chromiurii alloys being' suitable.

Rolling the ribbon develops fiber or grain which offers a definite electric resistance, but when narrow strips are cut from the ribbon transversely to the fiber. an increased resistance is had` l have found that while rolled or drawn resistance elements elongate when heated. their lateral expansion is much less proportionately for the same risc in temperature.

In the present case, the resistance to electl'ic currents of the transverse parts l is substantially the same as the semi-circular connections 2, but the parts l elongate very little because they are cut across the fiber. For the same amount of metal7 therefore. the element shown in Fig. 2 has the following advantages (a) It will not crawl toward its terminals as there is little tendency to elongate generally when heated.

(b) The transverse parts 1 otter the same resistance as the end parts 2 and the heating is uniform.

(c) The proportionately large surface area between terminals makes for maximum heating capacity.

After the clement has been produced I prefer to cement it to a ribbon of mica. which insulating material is laid flatly against the heat transmitting surface. preferably a thin sheet of steel. Any desired meansvmay be employed to hold the element in position` a block of asbestos or asbestos mixed with cement being preferred.

In Figs. 2. 3. and 4. this heating element A is shown mounted in a shell 3 having a cover 4. A body 5 of a poor heat-conducting material. such as asbestos, is mounted within the shell and has a groove 6 in its lower side in which a conductor 7, preferably of copper. is mounted. This body 5 is cut away at one end to afford space to bend the conductor 7 laterally. as shown in Fig. 2. the conductor ending in `a contact stcnl 8 which extends through a thimble 9 in the end 10 of the shell. A narrow strip 11 of insulating material prevents any possible contact between the screws 12 and 13 or the nuts 14 thereon with the bottom 15 of the shell. The screw 12 connects one end of the heating element to the conductor T while the screw 13 connects the other end of the heating element to the conductor 16 which has a contact stem 17. A thin piece 31 of mica may be placed between the conductors 7 and 16, as shown in Fig. 3 to prevent short circuiting between them.

Thin strips 18 and 19'of mica are placed on either side of the heating clement to insulate it from the cover 4 and body 5. The ends of the body Amay have extensions 20 provided with slots 21 through which bolts 22 may extend to secure the heater in position. In F ig. 6 a plate 23 is shown to extend along the front of an automobile radiator 24 to receive the heads of the bolts 22 which extend through proper air passages in the radiator which plate shields the heater from the air which normally lpasses through the radiator and with the.

heater and the adjacent radiating plates of the radiatorV constitutes what might be called a stove.

Conductor wires 25 may extend from a connection 26 (Fig. 1) to a. connection 2T on the instrument board of an automobile and thence conductor wires 28 may lead to a switch plug 29 which ma; be slipped onto the contact stems 8 and 1 It is to be understood that the use of this heating element is not limited to long, narrow heating devices, but that the element may be made of any desired configuration and used in any type of heater, so long as it is cut from a thin rolled sheet or ribbon and consists in serpentine portions all in the same general surface.

l. In an electric heater, the combination of a trough shaped case having a thin metal front, aI block of heat resistant material in the back of-the case, a heating element lying fiatA against the front of said block` and a thin sheet of insulating material between the heating element and the front of the case, said case havin perforated ears whereby it may be attached to a radiator.

2. In an electric heater, the combination of a trough shaped case having a thin metal front, a block of asbestos composition Htting within the case against the back thereof, a heating element ying fiat against the front of said block, a thin sheet of mica between the heating element and the front of the case said case having perforated ears, a plate of the size of the heater positioned at the front of an automobile radiator. and fastening devices attaching the plate and the front of the heater to saidn radiator.

WILLIAM A. SHARPE.

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