US3015084A

US3015084A - Electrical connector

Info

Publication number: US3015084A
Application number: US795823A
Authority: US
Inventors: Joseph J Gribble
Original assignee: Square D Co
Current assignee: Schneider Electric USA Inc
Priority date: 1959-02-26
Filing date: 1959-02-26
Publication date: 1961-12-26
Anticipated expiration: 1978-12-26

Description

Dec. 26, 1961 J. J. GRIBBLE ELECTRICAL CONNECTOR Filed Feb. 26, 1959 LIB R. m m m ROTATlOM United States Patent @7 3,015,084 ELECTRICAL CONNECTOR Joseph J. Gribble, Fox Point, Wis., assigner to Square D Company, Detroit, Mich., a corporation of Michgan Filed Feb. 26, 1959, Ser. No. 795,823 3 Claims. (Cl. 339-272) The present invention relates to electrical connectors, and particularly to solderless terminal lugs of the type in which a screw is threaded into the lug body to exert pressure on a solid or stranded conductor or cable.

One of the main problems in electrical connectors is that of maintaining a tight connection between the lug and the cable or conductor. A tight connection is obtained by gripping the cable between a shoe and the body of the lug with a predetermined amount of pressure. In prior lugs this pressure was obtained by providing the lug with a screw which abutted the shoe. The shoe engaged the conductor and the screw was threaded into the body of the lug and aganist the shoe to provide clamping pressure of the shoe on the cable. Vibration or movement of the parts relative to each other or turning of the screw in a loosening direction after assembly results in a release of this pressure and an increase in the electrical resistance between the conductor and the body of the lug. Also, after the clamp is tightened, certain portions of the metal of the clamp or lug, or cable are subject to cold flow and thereby a release of pressure and an increase in the electrical resistance between the conductor and the bodyof the lug. Further, it will be appreciated that if stranded conductors or cables are gripped, the strands of these conductors may move on one another or cold liow themselves to provide a release of pressure and an increase in resistance between the cable and lug. As the pressure was released, the resistance increased and the lug became heated and thus increased in temperature.

One of the objects of the present invention is to overcome the problems encountered with the prior electrical connectors by providing structure which will maintain the required pressure between the lug and cable.

Another object of the present invention is to provide leaf spring means between the screw and the shoe and so arranged as to maintain a more uniform pressure of the shoe against the conductor as well as to provide that leaf spring with teeth lockingly engaging the screw to retard turning movement of the screw relative to the lug body.

A further object of the invention is to loosely fasten the screw, the leaf spring means, and the clamping shoe together so that the parts may be positioned relative to each other during manufacture of the lug and while the lug is being secured to a conductor.

Other objects and a fuller understanding of the invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawings in which:

FIGURE 1 is a top view of an electrical connector with a conductor cable inserted therein;

FIGURE 2 is a sectional view taken along the line 2-2 of FIGURE 1 with the conductor omitted for purposes of clarity;

FIGURE 3 is a sectional view taken along the line 3 3 of FIGURE 1 with the conductor omitted for purposes of clarity;

FIGURE 4 is an enlarged top view of a modified form of the leaf spring means used in the connector;

FIGURE 5 is an end view of the leaf spring means of FIGURE 4; and

FIGURE 6 is a graph illustrating the ratio of temperature rise to screw rotation of the present invention as compared to connectors not having a leaf spring.

ffice An electrical connector capable of performing the objects of the present invention has a body adapted to be secured to a support. This body has a conductor receiving recess and a screw threaded passage whose axis intersects the axis of the recess. The connector further has a clamping shoe in the recess to bear against a conductor inserted in the recess and a screw threaded in the passage to exert pressure on the shoe.. Between the screw and the shoe is a leaf spring interengaging the shoe and screw and capable of stabilizing the pressure exerted on the shoe as the screw is turned in the threaded passage. This leaf spring has teeth lockingljy engaging the screw to retard turning movement of the screw relative to the body.

A preferred embodiment of an electrical connector incorporating the features of the invention has been illustrated in the drawings for purpose of examplication and not for the purpose of limitation.

The electrical connector illustrated is constructed of current conductive material. The connector or terminal lug has a body 10 provided with a blade 11 for securing the body to a terminal block or other supporting structure (not illustrated). The body lll'is of tubular shape to provide a top wall 12, a bottom wall 13, and opposite side walls 14 and 15 interconnecting the top and bottom walls and defining therewith a conductor receiving recess 16 for receiving a conductor such as the conductor 17 in FIGURE l. The body is also provided with a screw threaded passage 18 which extends through the top wall 12 and between the side walls 14 and 15 and has its axis intersecting the axis of the recess 16.

Turnably threaded into the screw threaded passage 18 is a screw 19 which carries a clamping shoe 20 and one or more leaf springs 21. In this instance the screw 19, shoe 21) and one leaf spring 21 are loosely joined into an assembly by a pin 22 which extends axially from the screw, through a hole 23 in the leaf spring and into the shoe 20.

The clamp shoe 20 has a relatively flat top surface 24 and a grooved bottom surface 25 with the groove running lengthwise of the shoe 20 and parallel to the axis of the recess 16. The shoe is rectangularl in shape and has a length greater than the distance between the walls 14 and 15 so that it will engage the walls 14 and 15 of the body 10 to prevent rotation of the shoe relative to the body.

The details of construction of the leaf spring 21 are best illustrated in FIGUR-ES 4 and 5. Several identical leaf springs 21 are illustrated in stacked relation, in FIG- URE 5, to show how they cooperatively fit together, when so stacked for use in place of a single leaf spring. When two springs are used, each should have half the resistance to defiection as when a single spring is used. The combination of the two springs will provide the same resistance to deflection and will provide the resistance to deflection over a greater range of deflection. Leaf springs 21 are of rectangular shape and elongated to provide opposite ends or spaced

portions

28 and 29, one on either side of the opening 23. In addition the spring is of modified wave shape or is curved so that the

portions

28 and 29 of the bottom most spring will seat against the top surface 24 of the shoe 2li while the remaining part of the leaf spring is not engaging the shoe. Between these spaced

portions

28 and 29 are a plurality of teeth 30 which extend outwardly from the surface of the leaf spring 21. The teeth on the uppermost leaf spring engage the screw 19. 'In this particular instance the teeth 30 are formed by providing tabs extending into the hole 23 and then twisting those tabs so that the edges extend away from the opposite surfaces of the respective leaf spring. The details of this design will not be described further since it is commonly used in lock washers.

When the conductor 17 is positioned in the recess 16 and the screw 19 is turned relative to the body 10, the screw 19 exerts pressure through the leaf spring 21 and against the clamp shoe to compress the conductor 17 between the clamp shoe 20 and the bottom wall 13. Since the leaf spring 21 is of rectangular shape it may abut the side walls to prevent turning of the leaf spring relative to the body. When the screw 19 has been turned until it is fully tightened the teeth 30 engage the bottom of the screw to lock the screw in position and at least retard turning movement of the screw relative to the body. Simultaneously the spring action of the leaf spring 21 stabilizes the force of pressure exerted by the screw on the shoe as the screw is turned in the threaded passage during the final tightening operation. lt has been found that best results are obtained when the spring is capable of stabilizing the pressure exerted by the screw on the shoe for at least one-half full turn of the screw.

After the screw has been tightened the teeth will retard loosening of the screw and the spring will stabilize the pressure exerted on the conductor, even when the screw loosens for at least onehalf full turn because of vibration or when other detrimental conditions for example, cold ow of the metal occurs.

In FIGURE 6 there is illustrated a graph which compares the rise in temperature of a connector which does not have a leaf spring (curve 32) with the rise in temperature of a connector which has one leaf spring (curve 32) and a connector which has more than one leaf spring (curve 34) for at least one-half full turn of a screw in the loosening direction. At the point x, which represents 1/2 turn of the screw, a lug without a leaf spring will have a temperature rise Y whereas a lug with a single leaf spring will have a temperature rise Z, and a lug with a plurality of leaf springs will have a temperature rise Z. At the point X these curves 32, 33, and 34 are farther apart, further indicating the greatly reduced heating resulting when one or more leaf springs are used to compensate for any cold ow or loosening of the screw. Thus a lug provided with a leaf spring will carry its rated current While remaining much cooler than a lug which does not have the leaf spring. In fact it has been determined that the insertion of the leaf spring means has reduced the temperature rise at least approximately 30% for over one-half turn of the screw.

Although this invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.

I claim:

1. A solderless terminal lug having a body to be secured to a support, said body having a conductor receiving recess of rectangular cross-section and a circular threaded passage whose axis intersects the axis of said recess, a clamping shoe in said recess and engageable with said body to prevent rotation of the shoe relative to the body, a screw adjustably threaded in said passage and having an end surface terminating in and movable in the recess, leaf spring means of modified wave-shape movable in said recess and engageable with said body to prevent rotation of the spring means relative to the body, said spring means having spaced portions engaging said shoe and an opening located between said spaced portions, a pin extending outwardly from said end surface through the opening and loosely securing the shoe to the screw and teeth formed on the spring means and disposed about said pin and lockingly engaging the end surface of the screw at spaced points about said pin to retard rotation of the screw in the threaded passage in at least one direction of rotation.

2. The structure of claim 1 wherein said leaf spring means is capable of stabilizing the pressure exerted by the screw on the shoe for at least 1/2 full turn of the screw relative to the body of the lug.

3. The combination as recited in claim 1 wherein a plurality of leaf springs of modified wave-shape are super-imposed upon each other in said recess.

References Cited in the file of this patent UNITED STATES PATENTS 2,679,634 Rawley May 25, 1954 2,712,123 Wibell et al. June 28, 1955 2,789,276 Hummel p Apr. 16, 1957 FOREIGN PATENTS 449,152 Great Britain Mar. 23, 1935 713,146 Germany Nov. 1, 1941 879,049 France Nov. 10, 1942 902,658 France Dec. 22, 1944