US1561272A - Method of making expanded-metal resistors - Google Patents

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Nov. 10, 1925- 1,561,272

H. C. NAGEL METHOD OF MAKING EXPANDED METAL RESISTORS Original Filed March '7. 1919 WITNESSES: I INVENTOR His/y GNa eI r v ATTORNEY Patented Nov. 10, 1925.

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Original application fil'ed March 7, I919, Serial No. 281,154@ Batent Kc. 1,396382'1, dated. November 192I. Divided and this application filed June 3,1921. serial No. 474,839.-

To all whom it may concern:

Be it known that I, HARRY C. EAGEL', a citizen of the United States, and a resident of *Wi'lkinsburg, in the county of Allegheny and State of Pennsylvania, have invented: a new and useful Improvement. in Methods of Making Expanded-MetalResistors, otwhich the following is a specification; this application being a -division olt my application Serial No. 281,154, filed March 7, 1919, which has matured into Patent No.1,396,871,.dated November 15,1921.

My invention relates to resistors for elec tric circuits and particularly to expandedmetal resistors and methodsot making. the

same.

The object of my invention is to provide an improved expanded-metal resistor and a novel method of makingthesame.

In some cases, as where it is desired to control the circuits of electric motors on board ship, castegrid. resistors are'unreli able because of their liability to become broken after repeated shocks, and "wire resistors have not the required capacity. Liquid resistors, too, are obviously undesirable. panded metal resistors. have accordingly been tried.

Ordinary expanded metal, however, is unsatisfactory for such uses because it cannot be obtained commercially with port-ions unexpanded or in the variety and degree. of expansion to. make: it adaptable for resistor work. A common method of manufacture, which comprises first, slitting the metal sheet and later, pulling the metal apart at the slits, is unsatisfactory because the width of the resulting product is less than that of the original sheet, the walls of some of the slits are pulled apart more than those of others, and, while some of the slit openings may be larger than is necessary for resistor purposes, thus causing the resistor to occupy unnecessary additional space, others of the openings may be so small as to cause shortcircuits.

Accordingly to the present invention, a strip of uncut metal is operated uptn in such fashion as to simultaneously cut and stretch the metal, whereby the resulting product is of the same width as the origlnal, uncut sheet. The metal is stretched in a direction oblique to the plane of the sheet so as to obtain comparatively large openings between the walls of the slits without the necessity of taking up. a great deal: of room in the plane ofithe grid. "The openings are provided of just. the pro-per size so-that. the maximum amount of resistor material -is crowded into the" min imum amount of space, without danger of short circuits. The open ingsare further of symmetrical form to provide for'the parallel resistance paths'being of equal length. :Ul fi ut portions of the metal are left at the ends to serve as terminals. To lengthenthe electrical, seriespath, the expanded metal is longitudinally slotted. If a steel or similar alloyis employed, the metal is sherardized or otherwise protected against the weather.

- Figurevl. oi the accompanying drawing is a front view of an improved forms. otmyexpanded metal resistor and Fig. '2 is a side view thereof, looking in the direction of the arrows. i

In forming my expanded-metal resistor, a sheet of metal having the requisite electrical conductivity first out along slits 1 to form a lengthened path for the electric current. The sheet is then moved longitudinally and to one side. The sheet is then cut at slits 2. opposite portions 9" that are not cut at the previous op.erati on. The sheet is then moved longitudinally in the same direction, Landto the other side, and is cut-at slits'fi opposite the slits first made, and so on" until s much ott'lie sheet has been out as is'desirec l; tions oftlie metal are" left uncut at the. ends, as shown at t and 5. Uncut portions may also, if desired, be left at the center and at other securing places.

Simultaneously with the slitting operation, the metal is stretched in a direction oblique to the plane of the sheet, by reason of the shape of the cutting tool, to produce openings 6 which shall be inclined to the plane of the sheet whereby the walls of the openings shall be separated from each other to an appreciable extent, thereby avoiding short-circuits, but without occupying an unduly large amount of room in the plane of the sheet. Oblique stretching is obviously better for this purpose than stretching either in the plane of the sheet or at right angles thereto. The simultaneous slitting and stretching is effected in such fashion that the portions of the openings (3 on each side of the metal portions 9 are oi.

the same size and width. The parallel paths of the current are thereby rendered equal in length.

By means of the simultaneous of slitting and stretching, there contraction in the width ofthe metal, because the stretching operation is effected at a time when the metal that is being stretched is contiguous to unstretched metal. The resulting product is therefore of the same Width as the uneXpan-ded metal and is stiffer than ordinary expanded metal.

The metal is then slotted as at 7 to increase the electrical series path from one of the terminals at, longitudinally through the grid to the terminal 5, and then back through the other portion ol the grid to the other terminal 4, and openings 8 are punched, one in the terminal portion 5 and one in each of the terminal portions 4 so as to provide for easily securing the resistor in position in a frame or box by means of bolts or similar securing means. The metal may then be sherardized or otherwise treated to preserve it from the destructive eli'ects ot the air. Such treatment is particularly sirable if the resistor is to be employed on board ship.

I have found that, in this manner, a very serviceable grid may be produced, which entirely satisfactory where cast metal grids and other resistors are undesirable, which is of uniform quality, having the requisite stiffness, and which is not subject to the defects of ordinary expanded-metal resistors.

I claim as my invention:

1. The method of making expanded-metal resistors which comprises slitting an interior portion of a plane metal sheet between two uncut end portions, simultaneously expanding said slitted portion, then actuatoperations can be no ing said sheet in the plane thereof and re- 7 peuting sald operation, and finally cutting through one of said end portions and said interior portion.

2. The method of making expanded-metal resistors which comprises slitting a plane metal sheet, simultaneously with the slitting operation stretching the metal obliquely to the plane of said sheet, then so actuating said sheet that upon repetition of said operation, the slits formed thereby in said sheet are in staggered relation to the slits formed by said first operation.

3. The method of forming an expandedmetal resistor which comprises simultaneously cutting and stretching an interior portion of a metal sheet between two uncut end portions, and slitting the resulting product through one 01": said end portions and said interior portion.

4. The method of forming an expandedmetal resistor which comprises simultaneously cutting and stretching an interior portion of a metal sheet between two uncut end portions, slitting the resulting product through one of said end portions and said interior portion, punching an opening in each of the slitted end portions and the said other end portion, and treating the resultant product to render it Weatherproof.

5. The method of making an expander metal resistor which comprises slitting an interior portion of a plane metal sheet between two uncut end portions, simultaneously expanding said slitted portion, then actuating said sheet longitudinally and to one side and repeating said operation, then :10- tuating said sheet longitudinally and toward the opposite side and repeating said operation, and finally cutting througl'i one of said end portions and said interior portion.

In testimony whereof, I have hereunto subscribed my name this 26th dav of Mav. 1921.

HARRY C. NAGEL.

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