Title:
Resistor
United States Patent 2279445


Abstract:
This invention relates to fixed resistors for use in electric circuits, and more particularly to the molded type of resistors used in radios. Many fixed resistors are provided with projecting terminals, such as wire leads, permanently attached thereto. The rest generally have their ends electroplated...



Inventors:
Clancy, William E.
Application Number:
US38357941A
Publication Date:
04/14/1942
Filing Date:
03/15/1941
Assignee:
STACKPOLE CARBON CO
Primary Class:
Other Classes:
338/322, 338/331
International Classes:
H01C1/14
View Patent Images:



Description:

This invention relates to fixed resistors for use in electric circuits, and more particularly to the molded type of resistors used in radios.

Many fixed resistors are provided with projecting terminals, such as wire leads, permanently attached thereto. The rest generally have their ends electroplated or sprayed with copper, nickel or other suitable low resistance metal for the purpose of providing the resistors with terminals to which wires can be connected. The objection to this latter type of resistor is that in connecting wires to the metal coated ends of the resistor the metal coating is often scraped off the resistor body sufficiently to increase the contact resistance between resistor and wire and thereby, in effect, change the resistance value of the resistor.

It is among the objects of this invention to provide a molded resistor of the type just referred to which has terminals that will not wear or scrape off, that strengthen the resistor, and that are applied in a simple and inexpensive manner.

In accordance with this invention a resistor body is formed by molding a charge of resistance material into the desired form, and embedding a foraminous piece of metal in the body with a portion of it, preferably only one surface, exposed in order to form a terminal for the body. By molding a foraminous terminal in the resistor body a strong union is effected between them, while the outer surface of the terminal forms a low contact resistance surface to which the wires of a circuit can be attached without danger of injuring the metal terminal.

The invention is illustrated in the accompanying drawing in which Fig. 1 is a plan view of one type of fixed resistor embodying my invention; Fig. 2 is a longitudinal central vertical section of Fig. 1; Fig. 3 is a perspective view showing a modification of the invention; Figs. 4 and 5 are side and end views, respectively, of a further embodiment; and Fig. 6 is a perspective view of another modification of the invention.

Referring to Figs. 1 and 2 of the drawing, a resistance material, preferably formed from a mixture of powdered graphite and an insulating binder, such as resin, is molded into a rectangular slug or resistor body 1. At the same time, pieces of foraminous metal, preferably copper screen, are molded or embedded in the opposite sides of the body adjacent its ends, but with the outer surfaces of the metal pieces exposed in order to form terminals 3 at both ends of the body. During molding a hole 2 is punched through each end of the resistor body and the embedded screen pieces. Any of the resistance material that may have squeezed out through the interstices of the screens during the molding operation and coated the outer surfaces of the terminals may be removed by buffing or the like. If . desired, both sides of the resistor body can be entirely covered by screen strips during the molding operation, after which the central portion of each strip can be ground away to leave the end terminals 3. Holes 2 through the resistor are for o1 the reception of a bolt 4 or other suitable fastening member by which a wire 5 of an electric circuit can be electrically connected to the terminal.

In thus fastening a wire in place there is no danger of scraping the metal terminals away because 13 they are of material thickness and are securely embedded in the resistor body.

In the embodiment of Fig. 3 a cylindrical resistor is shown which is adapted to be connected in a circuit by clips, or by wires soldered to it. The resistor therefore is provided with terminals II formed by molding a band of foraminous metal into the surface of the body 12 at each end thereof.

In Figs. 4 and 5 is shown another type of re23 sistor adapted to be held in a clip or soldered to circuit wires. In this form a circular piece of foraminous metal is molded in each end surface of the body 13 to form terminals 14 therefor.

In Fig. 6 a strip of foraminous material is :;:) molded in each end of a resistor body which completely encloses the embedded portion. However, the strips are long enough to project axially from the ends of the body and thereby form flexible leads for the body.

;3. The resistor shown in Fig. 6 is provided with projecting flexible leads or terminals 15 formed by molding only one end of a flat strip of foraminous metal, most suitably copper screen, in each end of the body 16. The strips lie approximately in the central longitudinal plane of the body and project from the opposite ends thereof so that they can be soldered to the wires of an electric circuit.

If desired, the terminals referred to herein can be plated with silver to avoid oxidation.

According to the provisions of the patent statutes, I have explained the principle and construction of my invention and have illustrated and described what I now consider to represent its best embodiments. 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. A resistor cbmprising a molded body of resistance material, and a foraminous piece of metal embedded in each of two opposite surfaces thereof with the outer surfaces of the metal pieces exposed, said metal pieces and body being provided with a common passage therethrough for the reception of a fastening member.

2. A resistor comprising a molded body of resistance material, and foraminous pieces of metal embedded in two opposite surfaces of each of its end portions with the outer surfaces of the metal to piece exposed, each end of the body and the adjoining metal pieces being provided with a common passage therethrough for the reception of a fastening member.

3. The method of making a resistor comprising molding strips of foraminous metal into two opposite sides of a body of resistance material with the outer surface of each strip exposed, and then removing all but the end portions of each strip whereby to form end terminals.

WILLIAM E. CLANCY.