US2286097A - Terminal - Google Patents

Description

June 9, 1942'. w. v. JOHNSON 2,286,097

TERMINAL Filed Oct. 29, 1958 Fig. 4.

1a? 6 12mg 7/ 90x15 ZZ WITNESSES: INVENTOR Welzon V Jo son. 06 BY ATT EY Patented June 9, 1%42 TERMINAL Welton V. Johnson, Short Hills, N. J., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application October 29, 1938, Serial No. 237,772

2 Claims.

This invention relates to terminals and it has particular relation to eye or loop terminals for electrical conductors or leads employed for connecting instruments and electrical circuits.

Terminals heretofore employed in practice ordinarily comprise a metallic lug which is united to an electrical conductor by means of solder. Such terminals have a number of objections resulting from their construction. Because of the heat required during the soldering operation, insulation present on the conductor may be charred and destroyed, and the metal itself of the conductor or terminal may be rendered more brittle. Furthermore, the eifectiveness of the bond between the terminal and the conductor is dependent upon the skill of the operator and accordingly is extremely variable. -In order to insulate such terminals, it has been the practice to employ three separate pieces of insulation which add to the complexity of manufacture and detract from the appearance of the finished terminal. After the completion of the soldering operation, the excess flux and solder, of course, must be removed. Finally, the mechanical strength of the bond between the terminal and the conductor is relatively low.

In accordance with this invention, a terminal is provided for a conductor by slipping over the end of the conductor a snugly fitted sheath which is bent together with a portion of the conductor enclosed therein into an eye or loop to form a finished terminal. Although the terminal could be used without further modification, I prefer to flatten the eye or loop by subjecting it to a pressing operation which not only produces an excellent bond between the internal surface of the sheath and the portion of the conductor adjacent thereto, but also provides a flat external surface on each side of the loop or eye which makes a satisfactory electrical contact with a terminal screw on which the terminal is mounted or with adjacent terminals in case a number of terminals are mounted on the same terminal screw. Insulation of the terminal assembly may be efiected by slipping over the conductor a tubular insulation member, such as that commonly referred to as spaghetti, which may be extended over an end of the terminal sheath.

It is, therefore, an object of this invention to provide a terminal which may be mounted in final position without employing a binder.

It is another object of this invention to provide a tubular sheath for the end of the conductor which has a flattened loop portion.

It is another object of this invention to insulate a terminal assembly by extending over an end of the terminal and an associated conductor a tubular insulating member.

It is a further object of this invention to provide a conductor terminal sheath having a flared end for facilitating entry of the conductor therein It is a still further object of this invention to provide a conductor terminal sheath having a partially or completely closed end.

It is another object of this invention to provide an improved method for constructing terminals having the characteristics set forth in the preceding objects.

Other objects of this invention will be apparent from the following description taken in conjunction with the accompanying drawing, in which:

Figure l is a view in plan of a lead employing terminals constructed in accordance with this invention; and

Figs. 2, 3 and 4 are detail views showing various stages of the manufacture of the finished terminals illustrated in Fig. 1.

Referring to the drawing, Fig. 1 shows a lead comprising a conductor I, which is illustrated as a stranded, flexible conductor, although other conductors, such as solid conductors, may be employed. The conductor l is provided with a terminal A having a neck portion 2 and a loop or eye portion 3. As illustrated, the neck portion 2 is circular in cross-section, whereas the loop or eye portion 3 has a flattened surface 4. Insulation for the assembly is provided by a tubular insulation 5, such as that commonly designated as spaghetti, but it is to be understood that my invention may be applied to pre-insulated conductors.

The terminalA shown in Fig. 1 is constructed by forming a tubular sleeve or sheath 6, as illustrated in Fig. 2. This sheath may be constructed in numerous ways, but preferably it is a seamless tube of electro-conductive material, such as copper. ,This sheath may be employed without further modification, but for purposes hereinafter set forth it is preferred to flare one end 1 outwardly and to close, either partially or completely, a second end 8. This may be done in any suitable manner, as by peening or spinning the metal at each end into the desired shape. In the specific embodiment illustrated, the end 8 is only partially closed.

The sheath as thus far described is next slipped over a conductor Ia until the conductor substantially abuts the closed end 8 of the sheath. Preferably, the sheath is of a diameter such that it snugly receives the conductor la. Because of the flare on the open end I of the sheath, the conductors la may be readily guided into the sheath. When the conductor la has been introduced into the sheath, the sheath and the enclosed conductor are bent into the form of a loop 3a, as clearly illustrated in Fig. 3. If desired, the terminal assembly may be considered as completed at this stage, but the terminals so constructed are not entirely satisfactory. Although a fair contact is provided between the conductor Ia and the sheath, this contact is not as satisfactory and permanent as desired. Moreover, since the sheath has a circular cross-section radial from the axis of the eye or loop, it offers what is substantially a line contact to the terminal screw or to adjacent terminals if more than one terminal is mounted on the same screw, as is customary in relay and other electrical work. When several terminals are mounted on the same terminal screw, because of the line contacts therebetween the terminals tend to stack irregularly, and when the terminal screw is tightened, the pressure exterted thereby on the stacked terminals may force the eyes or loops of the terminals open with a resultant possibility of a terminal dropping completely away from the terminal screw. Moreover, the adherence between the conductor la and the sheath at the stage illustrated in Fig. 3 is not sufficient to assure the retention of the conductor in the sheath under stresses ordinarily encountered in practice. That is, if a tension is applied to the conductor la, the conductor may be withdrawn entirely from the sheath.

The various defects pointed out in the foregoing paragraph may be overcome by subjecting the eye or loop 3a to pressure sufficient to flatten opposite surfaces thereof. This pressure may be applied in numerous ways, but in the particular manner illustrated in Fig. 4, the eye 3a is placed between a pair of dies 9, I9. The lower die I is provided with a pocket having a wall H which substantially surrounds the eye in order to prevent the eye from opening under the high pressures employed. If desired, the die I0 may also be provided with a core extending into the opening of the eye in order to prevent an excessive contraction of the opening. The opposed faces of the die may be given any desirable configuration, but ordinarily I prefer to make the portion extending over the eye or loop 3a substantially flat with slightly rounded edges l2, l3 for merging the flattened portion of the eye or loop 3a gradually into the circular neck portion 2a of the terminal.

Under the influence of the high pressures exerted by the dies 9, 1!], the internal surface of the sheath is forced against the conductor Ia flattening the conductor and forming an excellent electrical contact therewith. Moreover, the flattening operation tends to increase the strength of the loop or eye 3a in a direction radial from the axis thereof, thereby tending to restrain the loop or eye from opening under the influence of the pressure exerted by the terminal screw employed for attaching the terminal in its desired position. The compacting of the conductor la in the sheath also increases the mechanical adherence therebetween, which lessens the possibilities of the conductor being pulled away from the sheath under the forces experienced in practice.

Several advantages accrue from the particular shape given the terminal. Because of the flat surfaces imparted to the terminal by the dies, a number of these terminals may be stacked on a terminal screw and will stack neatly and uniformly. This is a very important advantage in many applications, such as relay work, in which a number of terminals must be mounted on the same terminal screw. Because of the large flat surfaces provided, excellent electrical contact, as well as mechanical contact, is provided between adjacent surfaces of the terminals and between the terminals and the terminal screw. The closed or partially closed end 8 of the sheath not only acts as a stop for the conductor when it is initially inserted in the sheath, but it prevents fraying of the end of the conductor under the pressure of the dies 9, l0 and provides a neat appearance for the resulting terminal. The flare formed at the end I of the sheath, as above noted, serves as a guide for the conductor la when it is initially introduced into the sheath and thereafter serves as a guide to prevent abrupt bending and nicking of the conductor la. Preferably, the edge of the end I is rounded to preclude any possibility of cutting the insulation. Since no solder is employed in the terminal, the terminal may be employed in apparatus subjected to high heat without fear of failure.

In order to insulate the conductor and terminal illustrated in Fig. 4, it is merely necessary to slip a tubular insulating member over the conductor I a and neck 2a of the terminal to produce the final lead illustrated in Fig. 1. The one-piece insulation serves to stiffen somewhat the junction between the conductor Ia and the neck 2a of the terminal, and may be extended until it abuts the eye or loop of the terminal.

As stated above, any suitable material may be employed for the sheath 6, copper and brass being examples of suitable electro-conductive metals for this purpose. In any event the material employed should be one that may be deformed under pressure and that will retain the deformed shape.

If a terminal is desired at each end of the conductor I, it is easy to fit a second sheath B over the remaining end of the conductor, a portion of the sheath being introduced between the conductor I and the insulation 5. This sheath is then bent into an eye or loop and pressed between the dies 9, I!) in the same manner described with reference to the terminal A.

The operation .of my invention may be recapitulated briefly as follows: In order to form a terminal for a conductor, a sheath 6 is selected having an internal diameter of a size sufficient to receive snugly a conductor. One end of the sheath 6 is provided with a slight outward flare in order to act as a guide for the conductor, and the other end of thesheath is partially or completely closed to'form a stop for the conductor and to prevent fraying of the conductor ends during subsequent treatment. After a conductor has been inserted into the sheath, the sheath is bent into the form of an eye or loop, and the eye or loop is sub jected to high pressures in order to flatten opposed surfaces and to improve the electrical and mechanical contacts between the sheath and the conductor enclosed thereby. Finally, an insulating member is slipped over the conductor and a neck left on the terminal.

Although I have described my invention with reference to certain. specific embodiments thereof, it is obvious that numerous modifications thereof are possible. Therefore, I do not wish my invention to be restricted except as required by the appended claims when interpreted in view of the prior art.

I claim as my invention:

1. The method for mounting a tubular sheath terminal on a flexible conductor which comprises placing said sheath terminal over the end of said conductor, bending said sheath terminal and enclosed end of said conductor into the configuration of a loop, maintaining a guide device about said loop for preventing opening thereof, and flattening said sheath terminal and enclosed end under pressure over a substantial part of the width of said sheath for forcing opposed flattened surfaces of said sheath terminal into intimate contact with said conductor while retaining substantially said loop configuration, said flattening of said sheath serving to form opposed flattened surfaces on said loop extending in planes substantially transverse to the axis of said loop and proportioned with said sheath for resisting opening of said loop under the influence of terminal screw pressure applied thereto.

2. The method for mounting a tubular sheath on a flexible conductor which comprises partially closing a first end of said sheath, flaring outwardly the walls of said sheath at a second end of said sheath, inserting said conductor through said second end until said conductor substantially abuts said first end, bending said sheath and enclosed conductor into the configuration of a loop, maintaining a guide device about said loop for preventing opening thereof, and pressing said loop between fiat surfaces with sufiicient pressure to produce opposed substantial flat surfaces thereon and to force said sheath into intimate contact with said enclosed conductor, said pressing of said sheath serving to form opposed fiat surfaces on said loop extending substantially radially from the axis of the loop and proportioned with said sheath for resisting opening of said loop under the influence of terminal screw pressure applied thereto.

WELTON V. JOHNSON.

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