US1708961A - Electric heater - Google Patents

Description

Aprifi 1929 c. ABBOTB" 11,78,951

ELECTRI C HEATER Original Filed July 6, 1926 Inventor: Cherries C. Abbott,

bLJ

' His Attow neg.

Patented Apr. 16, 1929.

UNITED STATES- PATENT OFFICE.

CHARLES C. ABBOTT, OF PTTTSFIELD, MASSACHUSETTS, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ELECTRIC HEATER.

Original application filed July 6, 1926, Serial No. 120,562. Divided and this application filed August 17,

1927. Serial My invention relates to electric heaters and has for its object the provision of a simple and rcliableconnection between a resistance conductor and a terminal member.

In carrying out my invention in one form I provide a slot in the terminal member and fold the end of the resistance conductor to provide a plurality of lengths which are placed in the slot and secured therein by pressing the sides of the slot together.

This application is a division of m copending application Serial No. 120,562, filed July 6, 1926.

For a more complete understanding of my invention reference should be had to the accompanying drawing in which Fig. 1 is a view mainly in section of an electric heater embodying my invention; while Fig. 2 is a sectional view of Fig. 1 taken along the line 2-2 looking in the direction of the arrow; Fig. 3 is an enlarged sectionalview showing the electric heating unit; Fig. 4 is a sectional view along the line 4-4 of Fig. 3.

Referring to the drawing, in carrying out my invention in one form I provide an electric heating unit comprising a metallic sheath or casing 10, preferably tubular, in which a heating resistance element 11 is secured. As shown, the heating resistance 11 is a wire which is made of a suitable material, such as a nickel chromium alloy. It is wound helically on a cylindrical support 12 made of suitable electrically insulating material, such as lava. The ends of the resistance wire are secured to metallic terminal members 18 and 14, which may be made of the same material as the resistance wire, the terminal members being inserted in longitudinal apertures or bores 13* and 14 provided for them in the support 12.

In order to provide for the connection of 1 the ends of theresistance wire with the terminal members 13 and 14, each terminal member is provided with a longitudinal slot 15, Figs. 3 and 4, the two terminal members being identical in construction. This slot begins at one end of the terminal member and terminates just short of the other end. The end of the resistance wire is folded over to form two or more parallel lengths which are twisted t -gether, as indicated by the numeral 16. As shown, three lengths are twisted together. the groove 15 and then the side walls of the This twisted portion 16 is placed in groove are pressed together or peened over an intermediate section of the twisted portion, as indicated at 17 and 18. The ends of the twisted portion project from the peened over walls of the groove, and, due to the constriction of the intermediate length, effectively secure the twisted portion in place. As connected with the terminal member 14, the resistance wire extends from the open end of the groove, but in the terminal member 13 the twisted portion 16 is reversed so that the wire passes out laterally from the opposite end of the groove, as shown in Fig. 1.

In assembling the resistance Wire and terminals on the support 12, the resistance wire is secured to the terminal 14, and the terminal 14 inserted in its aperture 14, the resistance wire being laid in a longitudinal groove 19 provided for it in the support 12 and brought to the opposite end of the support where it is laid in a cross groove 20 in the support and brought out at the opposite side. The resistance wire is then wound helically on the support toward the opposite end and sufficient slack is left in the resistance wire after the winding operation to permit the terminal 13 to be connected as previously described and then inserted in its aperture 13 in the support, the'resistance wire extending through a longitudinal slot 21 in the support. After the terminal 13 has been put in place the resistance wire is tightened by twisting the terminal one or more revolutions, whereby one or more turns of the resistance Wire are wound around the terminal 13 to take up the slack. The edges of the groove 15 are rounded off at 15 and 15 at the region where the wire is brought out laterally, in connection with terminal memben13, so that the wire will not be injured when wound on to take up. the slack. This form" of connection provides a very reliable mechanical and electrical joint and also allows the resistor to be readily assembled on the support 12.

The core 12 with the resistance wire there on is embedded in the sheath '10 in powdered heat refractory insulating material 22, such as magnesium oxide, which is preferably compacted so as to secure the core and heating resistance in place and also to increase the heat conductivity of the powdered material. As shown in the drawing, the turns of the resistance wire are suitably spaced apart on the core, the powdered insulating material being packed between the turns. This compacting operation may be carried out in any suitable manner, for example by reducing the diameter of the sheath, as by swaging or rolling, after the unit has been assembled.

The end of the sheath opposite the terminal members 13 and 14 is closed by means of a metallic washer 23, the end of the sheath being spun over to secure the washer in place. In the opposite or terminal end of the sheath is a washer 24 made of insulating material, such as mica, and a porcelain insulator 25, apertures being provided in the washer and insulator for the protruding end lengths 26 and 27 of the terminal members. To im prove their flexibility the lengths 26 and 27 may be made of twisted wire. As shown, these protruding ends or terminals are somewhat smaller than the terminal member por tions inside the unit, a shoulder being thereby formed at the junction of the two portions on which the insulating washer 24 is seated. The end of the sheath 10 is spun over a shoulder 28 provided on the insulator 25. In addition to acting as an insulator, the washer 24 acts as a cushion or bufier to prevent cracking of the porcelain insulator 25 from the end pressure caused by the swaging operation.

While I have described my invention as embodied in concrete form and as operating in a specific manner in accordance with the provisions of the patent statutes, it should be understood that I do not limit my invention thereto, since various modifications thereof will suggest themselves to those skilled in the art without departing from the spirit of my invention, the scope of which is set forth in the annexed claims.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. The method of securing a resistance conductor to a metallic terminal member which consists in providing a longitudinal groove in the terminalmeniber, folding the conductor to provide a plurality of lengths, placing said lengths in said groove, and then compressing the sides of the groove on said lengths to secure the resistance-conductor to said terminal member.

. 2. The method of securing a resistance wire to a metallic terminal member which consists in providing a longitudinal groove in the terminal member, twisting lengths of the wire together, placing said twisted portion in said groove, and then squeezing the sides of said groove together on said twisted portion.

3. The method of securing a resistance wire to a metallic terminal member which consists in twisting lengths of said wire together, and then compressing the metal of said terminal around said twisted portion.

4. The method of securing a resistance wire to a metallic terminal member which consists in twisting lengths of said wire together, and then compressing the metal of said terminal member around a central section of said twisted portion.

5. The method of securing a heating resistance wire to a terminal member which consists in providing a longitudinal groove in the terminal member, folding the wire to form a plurality of parallel lengths, twisting said lengths, laying said lengths in said groove, and then squeezing the sides of said groove together on said twisted portion.

6. In an electric heater, a terminal member provided with a groove, and a resistance conductor provided with folded lengths laid in said groove, the walls of said groove being compressed in said lengths to secure the resistance conductor to said terminal.

7. In an electric heater, a terminal member provided with a groove, and a resistance conductor provided with folded twisted lengths laid in said groove, the walls of said groove being compressed in said lengths to secure the resistance conductor to said terminal.

8. In an electric heater, a terminal member provided with a longitudinal slot, a resistance conductor provided with folded twisted lengths laid in said slot, the walls of said slot being compressed on said lengths to secure said resistance conductor to said terminal member. 3

In witness whereof, I have hereunto set my hand this 15th day of August, 1927.

CHARLES C. ABBOTT.

Images