US2623971A - Electric resistance heater - Google Patents

Description

Dec. 30, 1952 T. W. GLYNN ELECTRIC RESISTANCE HEATER Filed June 21, 1951 2 SHEETS-SHEET l IN V EN TOR. M50002: (7X61. YNN

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ELECTRIC RESISTANCE HEATER Filed June 21, 1951 2' SHEETS-SHEET 2 'HTTOPNEXi Patented Dec. 30, 1952 UNITED STATES PATENT OFFICE ELECTRIC RESISTANCE HEATER Theodore W. Glynn, Kingsport, Tenn., assignor to Blue Ridge Glass Corporation, Kingsport, Tenn., a corporation of New York Application June 21, 1951, Serial No. 232,746

Claims. 1

This invention relates to electric resistance heaters, and more particularly, to those in which an electric heating element covers one side of an upright glass plate for space heating.

Such heaters are Well known and are generally mounted so that they can be set upright on the floor or attached to a wall of a room. Due to convection, the top portions of such plates always are hotter than the bottom portions. The heating elements of the heaters have been a single electrical conductor made of aluminum or other metal having the desired electrical resistance for producing heat. The conductor usually is formed by spraying the resistance material on the glass plate. Since the resistanace of the heating element becomes greater as the temperature of the plate increases, and the top portion becomes hotter than the bottom portion due to convection, the top portion is caused to have a greater resistance than the bottom portion. With a series circuit, in accordance with Ohms law, that portion having the greater resistance will develop the most heat. Thus, the convection and the increase in resistance of the top portion both cause a considerable temperature difference between the top and bottom of the plate.

It is among the objects of this invention to provide an electric resistance heater in which the temperature difference between the top and bottom of the plate is reduced, in which the maximum temperature of any part of the plate and the average temperature of its upper half are reduced at the same time that the average temperature of the lower half of the plate is increased, in which a higher wattage can be put into the plate for a given maximum temperature of any part of plate than heretofore, and in which high voltage differences are avoided in the hottest part of the plate.

g In accordance with this invention, a heating element covers most of one side of an upright glass plate. The ends of the heating element are connected to a pair of electric terminals. The heating element is formed from a plurality of electrical conductors having the desired electric resistance, which are connected in parallel between the terminals. Each of the conductors covers a different area of the plate, the areas being disposed one above the other. Although three or more conductors can be used in some cases with better results than two, for most practical purposes two conductors are sufiicient, one of them covering substantially the upper half of the plate and the other one covering only the lower half of the plate. The conductors preferably extend either back and forth across the plate in vertically spaced lengths or up and down the plate in horizontally spaced lengths.

The invention is illustrated in the accompanying drawings, in which Fig. 1 is a view of one side of an upright electric resistance heater; and Figs. 2, 3, 4 and 5 are diagrammatic side views of four modifications of this invention.

Referring to Fig. 1 of the drawings, a rectangular panel or plate I of tempered glass of the type generally used for an electric resistance type of space heater is adapted to be mounted in a frame or other support of well known form which can be set on the floor or hung on a Wall. Since the frame forms no part of the invetnion, it is not disclosed. Mounted on one side of the glass plate is an electric heating element which is formed from at least two electric conductors 2 and 3 integrally connected in parallel to a pair of terminals 4 and 5, most suitably disposed at the bottom of the plate substantially midway between its ends. Soldered to these terminals are metal sleeves 6, in which wires 1 are fastened for connecting the heating element in an electric circuit, such as the usual volt household circuit.

The conductors are formed from electrical re sistance material, preferably aluminum or aluminum alloy sprayed on the surface of the plate in a predetermined pattern. The pattern is such that with two conductors or resistors, one of them covers substantially the upper half of the plate, while the other covers only the lower half. The two conductors have substantially the same resistance when cold. The upper conductor 2 may be somewhat longer than the lower one, although not necessarily so. The upper conductor extends from terminal 4 along the bottom of the plate to a point near the adjacent right hand corner. The conductor then extends straight up the plate to a point near its top and then straight across the plate to a point near its opposite end. From there the conductor extends down a very short distance and then back across the plate. The conductor continues to extend back and forth across the plate in this zigzag fashion until it reaches a point about half way down the plate at the left hand end of the plate. The upper half of the plate therefore is traversed by a considerable number of vertically spaced parallel lengths of conductor 2 in the form of horizontal bars. From the left hand end of the lowest bar, conductor 2 extends down the end of the plate to its bottom and then straight across to terminal 5, thus'completing a circuit.

I'he other conductor 3 covers the area of the plate that is surrounded by the first conductor. This is substantially the lower half of the plate. Thus, the lower conductor extends from terminal 4 horizontally toward the adjacent end of the plate and then upward a short distance and back toward the same terminal. If the terminal is too high for the conductor to extend across it, the conductor then extends back to the right hand end of the plate again and then back across substantially the full length of the plate. From there conductor 3 extends back and forth across the plate in the same way as the other conductor to form vertically spaced parallel lengths or bars. The upper bar is directly .below the lowest bar of the upper conductor, and its left hand end is connected by a vertical portion to a lower portion that extends back and forth between the vertical portion and terminal 5 until conductor 3 connects with that terminal.

When this heater is plugged into an electric circuit, the top half of the plate will become hotter than the lower half, due to convection. The higher temperature upper portion of the plate will increase the resistance of the upper conductor more than the resistance of the lower conductor will be increased, and accordingly the amperage of the. upper conductor will decrease and less wattage will be developed in conductor 2 than in conductor 3. Since the voltage across the top half of the plate and the voltage across the bottom half are each equal to the line voltage, the wattage input at the lower half of the plate is not decreased so much as in present heaters with a single conductor where the voltage drop across the lower half is directly proportioned to the resistance of the lower half and is less than the line voltage for the new plate. Consequently, the temperature of the lower half of the new plate will remain higher than heretofore. At the same time, due to the fact that the line voltage for the new plate is less than the voltage drop across the top half of a plate that is provided with a single conductor heating element and that develops approximately the same total wattage, the maximum temperature. reached by the upper half of my plate will be less than in the case of the single conductor plate. The result is that the maximum temperature at the hottest spot of my plate and the average temperature of the top half of the plate will be reduced as compared with a .plate provided with a conventional single conductor heating element, but the average temperature of the lower half of the plate will not be reduced so much as formerly. This means that the total temperature difference over the plate will be reduced materially as compared with a plate having only a single conductor heating element. More uniform heat distribution over the plate results in less expansion stress and a more durable plate from the breakage standpoint. Although this heater can take the same wattage as heretofore and yet have a lower temperature at its hottest spot, it also can take a higher wattage without exceeding the maximum temperature reached on the standard series design of heater. In an actual case the maximum temperature of the heater was lowered F. in one instance, and in the other instance the rated wattage of the heater was increased about 180 watts.

Due to the fact that glass becomes a poorer insulator as it becomes hotter, it is advantageous to avoid high voltage differences between conductor bars in the hottest areas of the plate, as far as possible. The circuit design shown in Fig. 1 has such an advantage, as well as the advantage of symmetry of pattern. However, other designs or patterns can be used, such as shown in Figs. 2 to 5.

Thus, in Fig. 2 upper conductor [2 is arranged substantially like. conductor 2 of Fig. l, but lower conductor I3 is perfectly symmetrical, with everything below the top bar extending from the center of the plate toward its opposite ends.

In Fig. 3 the lower conductor 23 is arranged like conductor 3 of Fig. 1, and upper conductor 22 is more like conductor 12 of Fig. 2.

Fig. 4 shows a circuit pattern in which upper and lower conductors 32 and 33 correspond, respectively, to upper conductor 23 of Fig. 3 and to lower conductor I3 of Fig. 2. Both conductors are symmetrically arranged.

In Fig. 5 the lengths or bars formed from the zigzag portions of the two conductors 42 and 53 extend vertically. The two conductors form symmetrical patterns.

According to the provisions of the patent statutes, I have explained the principle of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. An electric resistance heater comprising an upright glass plate, a heating element covering most of one side of the plate, and a pair of electric terminals for said element on the plate, said element being formed from a plurality of electrical conductors connected in parallel between said terminals, said conductors having substantially the same resistance when cold but having greatly increased resistance when hot, each of said conductors covering a different area of said plate, and said areas being disposed one above the other, whereby the resistance of the upper conductor will be increased by heat rising from the lower conductor.

2. An electric resistance heater comprising an upright glass plate, a heating element covering most of one side of the plate, and a pair of electric terminals for said element on the plate, said element being formed from two aluminum electrical conductors connected in parallel between said terminals and having substantially the same resistance when cold, one of the conductors covering substantially the upper half of said plate, and the other conductor covering only the lower half of the plate, whereby heat rising from the lower conductor will increase the temperature and resistance of the upper conductor.

3. An electric resistance heater comprisin an upright glass plate, a heating element covering most of one side of the plate, and a pair of electric terminals for said element mounted at the center of the bottom of the plate, said element being formed from two aluminum electrical conductors connected in parallel between said terminals, one of said conductors coveringsubstantially the upper half of said plate, and the other conductor covering only the lower half of the plate.

4. An electric resistance heater comprising an upright glass plate, a heating element covering most of one side of the plate, and a pair of electric terminals for said element mounted at the center of the bottom of the plate, said element being formed from two aluminum electrical conductors connected in parallel between said terminals, one of the conductors covering substantially the upper half of said plate and having end portions extending down the ends of the plate and then across its bottom to said terminals, and the other conductor covering the area of the plate bounded by the upper conductor portions and the portion joining their upper ends.

5. An electric resistance heater comprising an upright glass plate, a heating element covering most of one side of the plate, and a pair of electric terminals for said element mounted at the center of the bottom of the plate, said element being formed from two aluminum electrical conductors connected in parallel between said terminals, one of the conductors extending from one of the terminals along the bottom of the plate to and then up along the end of the plate to and across its top and then back and forth across the plate in vertically spaced lengths to cover substantially its upper half, the conductor then extending downward along the other end of the plate to and along its bottom to the other terminal, and the other conductor covering the area of the plate surrounded by the upper conductor.

6. An electric resistance heater comprising an upright glass plate, a heating element covering most of one side of the plate, and a pair of electric terminals for said element mounted at the bottom of the plate, said element being formed from two aluminum electrical conductors connected in parallel between said terminals, one of said conductors extending from one of the terminals along the bottom of the plate to and then up along the end of the plate to and across its top and then back and forth across the plate in vertically spaced lengths to cover substantially its upper half, the conductor then extending downward along the other end of the plate to the other terminal, and the other conductor extending from one of the terminals back and forth across the plate in vertically spaced lengths to a point adjacent the lowest length of the first conductor and then downward beside the first conductor and finally back to the other terminal.

7. An electric resistance heater comprising an upright glass plate, a heating element covering most of one side of the plate, and a pair of electric terminals for said element mounted at the center of the bottom of the plate, said element being formed from two aluminum lectrical conductors connected in parallel between said terminals, one of the conductors extending from one of the terminals along the bottom of the plate to and then up along the end of the plate to and across its top and then back and forth across the plate in vertically spaced lengths to cover substantially its upper half, the conductor then extendin downward along the other end of the plate to and along its bottom to the other terminal, and the other conductor extending from the right hand terminal back and forth across substantially the right hand half of the plate in 6 vertically spaced lengths and then across substantially the left hand half of the plate directly below the lowest length of the upper conductor, the lower conductor then extending back and forth across said left hand half in vertically spaced lengths to the left hand terminal.

8. An electric resistance heater comprising an upright glass plate, a heating element covering most of one side of the plate, and a pair of electric terminals for said element mounted on the plate, said element being formed from two aluminum electrical conductors connected in parallel between said terminals, one of said conductors COVSIiIlg substantially the upper half of said plate, and the other conductor covering only the lower half of the plate, each conductor having vertically spaced lengths extending back and forth across the plate from points near th ver tical center line of the plate to points near its opposite ends.

9. An electric resistance heater comprising an upright glass plate, a heating element covering most of one side of the plate, and a pair of electric terminals for said element mounted at the bottom of the plate, said element being formed from two aluminum electrical conductors connected in parallel between said terminals, one of said conductors extending from said terminals about half way up the opposite ends of the plate and then back and forth across the plate from said ends to points adjacent its vertical center line in vertically spaced lengths connected at the top of the plate by a length extending nearly the full length of the plate, and the other conductor extending from one of the terminals back and forth across the plate in vertically spaced lengths to a point directly below said lengths of the other conductor and then downward beside the first conductor and finally back to the other terminal.

10. An electric resistance heater comprising an upright glass plate, a heating element covering most of one side of the plate, and a pair of electric terminals for said element mounted at the center of the bottom of the plate, said element being formed from two aluminum electrical conductors connected in parallel between said terminals, one of said conductors extending from said terminals outward toward the opposite ends' of the plate and then upward to its top and up and down across substantially the upper half of the plate in horizontally spaced lengths, and the other conductor forming substantially the same pattern over the lower half of the plate.

THEODORE W. GLYNN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,957,227 Reimers et a1 May 1, 1934 2,119,680 Long June 7, 1938

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