US3723950A - Junction block and method of making same - Google Patents

Abstract

The method of making a barrier strip wherein an insulator body is formed of a thermo plastic material, the insulator body having a stressing wall therein; and an electrically conductive metal conductor clip is formed with a resilient pre-stressing section; assembling the conductor clip with the insulator body in such fashion that the clip pre-stressing section is placed under a distorting force by engaging it with the stressing wall of the insulator body; heating the assembly to place the insulator body in a pliable state so that the stored force in the pre-stressing section of the conductor clip is relieved by the movement of the clip into the pliable plastic body; and cooling the assembly to provide a close mechanical interlock between the insulator body and the conductor clip. A novel barrier strip assembly results from the above method.

Description

United States Patent [1-91 Lovrenich [54] JUNCTION BLOCK AND METHOD OF MAKING SAME [76] Inventor: Rodger T. Lovrenich, 2285 West [58] Field of Search ..339/198, 217, 218, 220, 221, 339/95; 29/629, 630 D; 85/7 P; 24/221 A, 221 R, 73 R, 73 M [5 6] References Cited UNITED STATES PATENTS 3,348,191 10/1967 Kinkaid ..339/176 2,344,832 3/1944 Rosengren ..24l22l A 3,585,574 6/1971 Drapkin ....339/l98 R 3,274,532 9/1966 Engel ....339/l76 3,530,422 9/1970 Goodman ..339/17 [4 1 Mar. 27, 1973 3,497,952 3/1970 King et a1. ..29/629 Primary ExaminerMarvin A. Champion Assistant Examiner-Robert A. Hafer Attorney-Earl F. Kotts [57] ABSTRACT The method of making a barrier strip wherein an insulator body is formed of a thermo plastic material, the insulator body having a stressing wall therein; and an electrically conductive metal conductor clip is formed with a resilient pre-stressing section; assembling the conductor clip with the insulator body in such fashion that the clip pre-stressing section is placed under a distorting force by engaging it with the stressing wall of the insulator body; heating the assembly to place the insulator body in a pliable state so that the stored force in the pre-stressing section of the conductor clip is relieved by the movement of the clip into the pliable plastic body; and cooling the assembly to provide a close mechanical interlock between the insulatorbody and the conductor clip. A novel barrier strip assembly results from the above method.

2 Claims, 17 Drawing Figures 3 Sheets-Sheet 2 INVENTOR P000512 7. LOVREN/CH Patented March 27, 1973 5 Sheets-Sheet 5 EICH JUNCTION BLOCK AND METHOD OF MAKING SAME BACKGROUND OF THE INVENTION The term barrier strip" is used herein as a generic term which includes both junction blocks and terminal strips. It is basically a long strip of insulator material containing several electrically conductive conductor sections separated by insulating barriers.

Junction blocks are devices for making an electrical connection between one conductor and another conductor. The conductors usually are wires. Such devices often comprise plastic insulator blocks with spaced apart metal face plates having threaded portions extending into openings through the block. The threaded openings are adapted to receive the threaded shanks of cap screws so that the heads of the cap screws can be drawn down to the face plate.

In some instances in prior art devices the ends of the cap screws are upset, after they are screwed into position, by an upsetting tool which is inserted through the back of the assembly into the openings which extend through the insulator blocks. Such openings occasionally cause difficulty because if a cap screw is too long, it will extend through its opening and out the back of the insulator block where it is in position to cause short-circuiting. However, if the back of the insulator is closed (to preventlong screw short circuiting), it is impossible to upset the end of such a cap screw.

In these prior art devices, the metal clip is assembled to the insulator block by riveting in the case of open back versions and by a friction or press fit in the case of closed back versions. However, underwriting agencies have tended to reject applications employing friction retaining methods.

Further the prior art devices have been made of brittle insulating materials, such as a phenolic plastic, and these materials tend to chip and break in the field.

OBJECTS It is a principal object of the present invention to provide a novel barrier strip involving a process of manufacture which produces an insulator body of flexible material having a metal conductor clip assembled thereto in a manner to provide an improved mechanical interlock.

It is another object of the present invention to provide such a barrier strip which includes an insulator body with a closed back, and wherein the conductor clip includes a cap screw with an upset end.

It is another object of the present invention to provide such a barrier strip wherein the cap screw and clip are assembled prior to assembly with the insulator bodyj I have found that the foregoing and related objects can be attained by a method disclosed in the following description and accompanying drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary plan view of ajunction block, the right end portion being shown without a conductor clip inplace.

FIG. 2 is a side elevation of the device shown in FIG. 1.

FIG. 3 is a sectional elevation taken along the line 3--3 in the direction of the arrows in FIG. 2.

FIG. 4 is a plan view of the clip plate.

FIG. 5 is an end elevation of the clip shown in FIG. 4.

FIG. 6 is a sectional elevation showing the clip being inserted in place.

FIG. 7 is an elevation similar to FIG, 6 showing the clip embedded into the insulator block after heating.

FIG. 8 is another modification of the .clip arrangement shown in FIG. 6, positioned in. an opening in the insulator block.

FIG. 9 is a view similar to FIG. 8 showing the clip embedded into the insulator block after heating.

FIG. 10 is a plan view of a terminal strip showing the second embodiment of the present invention.

FIG. 11 is a side elevation of the terminal strip shown in FIG. 10.

FIG. 12 is a sectional elevation taken along the line 12--12 in the direction of the arrows in FIG. 11.

FIG. 13 is a side elevation of the conductor clip used with this embodiment.

FIG. 14 is a rear view of the conductor clip shown in FIG. 13.

FIG. 15 is a bottom view of the conductor clip shown in FIGS. 13 and 14.

FIG. 16 is an elevation of the terminal strip shown in FIGS. 10-12, sectioned to disclose the cam surface.

FIG. 17 is a sectional view of another modification of the invention disclosing a different type of clip.

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment The first modification of the first embodiment is shown in FIGS. 1-7 of the drawings. The second modification of the first embodiment is shown in FIGS. 8 and 9.

Referring to FIG. 1, a portion of an elongated junction block is shown at 10. This block is formed of a material which is an electrical insulator. The material is of the thermoplastic type which will be pliable when heated to its softening temperature and which will solidify or harden when cooled. The preferred material is a material such as polycarbonate because this material is flexible when it sets and will not chip or break like I the plastics normally used in such applications. However; other thermoplastics such as nylon, polystyrene, vinyl copolymers, and the like can be used.

The block 10 is formed as a long strip with equally spaced barriers 14. These barriers insure adequate electrical insulation between adjacent junction terminals. For convenience the portion of the junction block between adjacent barriers will be referred to as a and 18 at the right in FIG. 1. Forming a .part of openings 16 and 18 are slots 20 and 22 respectively adapted to accommodate the downturned ends of the plate of the conductor clip 24 (FIG. 5). The back of the insulator body 10 is closed as shown at 26. As shown in FIG. 1, no conductor clip is inserted in the end openings, these openings being reserved to accommodate hold-down cap screws. The conductor clip 24 includes a flat plate 28 whic has a pair of downturned threaded bosses 30 and 32 and a pair of downturned ends 34 and 36. Each of the ends is constructed as shown in'FIG. 5 with a pair of upward and outward extending FIGS. 38 and 40. The conductor plate 28 is formed of a resilient metal (usually brass) which is capable of conducting electricity. As shown in FIG. 6 the slot 22 is of such width that the walls of the slot move the small fingers 38 and 40 of the conductor clip 24 inward and stress these resilient fingers whereby they store a force which tends in the absence of an obstacle, to return them to their natural position.

Assuming that the insulator material is polycarbonate, the assembly is then heated to a suitable temperature such as 300 F. by immersion in hot glycerin, which additionally anneals the material. When the polycarbonate has been heated it becomes soft and the metal fingers 38 and 40 are able to relieve their stress and move to their normal position and thus penetrate into the plastic as shown in FIG. 7. When the assembly is cooled, a strong close-fitting mechanical interlock is formed between the fingers and the adjacent portion of the insulator block.

Prior to attaching the conductor clip plate 28 to the insulator body, clamp plates 42 and 44 are fixed in place on the shanks of cap screws 46 and 48. The cap screws are threaded through bosses 30 and 32 and then the ends of the cap screws are upset as at 50 and 52.

I This prevents the cap screws from accidentally becoming free from the assembly during handling and shipment.

The elongated strip can be cut at cut-line A (FIG. 1) in the factory to provide a strip of the desired length before further assembly. A cut can be made along cut-line B in the field and then the clip is pulled out sidewise. The holes in the plastic insulator body can then be used to accommodate hold-down bolts.

Another modification of this embodiment is shown in FIGS. 8 and 9 of the drawings. Each downturned end of the conductor clip plate has a bifurcated portion which results in two resilient legs 54 and 56. The clip end is shown inserted in the opening 22 of the insulator body, and it will be noted that the legs 54 and 56 are displaced inward toward each other. After the assembly is heated as described above, the plastic becomes pliable, and the legs 54 and 56 spread apart embedding the fingers 38 and 40 into the plastic. Again, this results in a strong interlock when the assembly is cooled.

Second Embodiment ,The second embodiment of the present invention is disclosed in FIGS. -17 of the drawings. A terminal. strip is shown at 110. It is formed of a thermoplastic such as plastic. Central openings such as shown at 104 and 106 are formed in the body 102 of the strip. Transverse slots 108 and 110 extend across the central holes. The width of these slots is less than the diameter of the central holes so that hold down bolts such as shown at 111 (FIG. 11) will not slip out sidewise. Extending I beneath the central holes are cam tracks 113 as shown in FIG. 16.

The electrical conductive metal conductor clip is shown generally at 112 in FIGS. 13, 14 and 15. It includes a top section 114 which has a downward extending boss 116 therein. The boss has internal threads 1 18. Extending downward from the top section 114 is a back section 120 which is of less width than the top section.

A bottom section 122 is bent back at about 90 to a point beneath the boss 116. At this point it is again bent at about to form a downwardly extending tail 124.

FIGS. 3-15 is applied to the insulator body 102 as shown in FIG. 12. The clip is seated in the opening in the insulator body and the tail 124 of the clip extends down through the central openings, such as 104 (FIG. 10) of the drawing, and the sidewise extending ears 126 and 128 of the tail move down through the slot 110. When the clip is firmly in place, pliers or other suitable tools are used to twist the tail 90 to its normal position. As this is done, the tail ears 126 and 128 ride on the cam track 113 shown at FIG. 16 of the drawings. The twisted position of the conductor clip tail is shown in FIG. 12.

As the conductor clip ears move downward along the cam track, the bottom 122 of the clip is pre-stressed against the adjacent seat in the insulator body. At this point, the clip is in a stressed condition.

The bottom portion of the insulator body 102 is formed to provide a tubular protective boss 135. The protective boss extends into opening 136 in a panel 138. The protective boss avoids accidental contact of the conductor clip tail 124 with the panel 138. When placed in position as shown in FIG. 12, the device is ready for soldering of a wire to the tail 124 above the spade 134. In this embodiment, heating of the tail 124 during the soldering process will cause softening of the plastic adjacent the ears 126 and 128, and the stress in the conductor clip will cause the ears to penetrate into the plastic. When the assembly cools, a close mechanical inter-lock is formed.

A holding plate is shown at 140 with a cap screw 142 extending therethrough into threaded engagement with the downward extending boss 1 16. In use, a wire will be placed between the holding plate 140 and the top 114 of the conductor clip 112.

Another modification of this embodiment is shown at FIG. 17. This modification is adapted for use with a printed circuit board. The only difference in this modification is the tail configuration 224 which extends into an opening 236 in circuit board 238.

Having thus described my invention, I claim:

1. A terminal strip comprising an elongated strip of electrical insulating material with spaced apart substantially parallel barrier walls forming a stall therebetween;

said stall having a hole therethrough and a cam track in said hole which spirals along the sidewall of the hole; and

a conductor clip of resilient electrically conductive material having a top seated on the top of said strip and a downward extending tail with a pair of fiat ears extending sidewise in opposite directions; said ears resting against said cam track such that said clip is adapted to be twisted to effect movement of said ears along said cam to a stressed position.

2. A terminal strip as claimed in claim 1 wherein the electrical insulating material is thermoplastic and is adapted to receive the clip ears embedded therein when said clip is twisted and heated.

a; a: a: a a:

Claims (2)

1. A terminal strip comprising an elongated strip of electrical insulating material with spaced apart substantially parallel barrier walls forming a stall therebetween; said stall having a hole therethrough and a cam track in said hole which spirals along the sidewall of the hole; and a conductor clip of resilient electrically conductive material having a top seated on the top of said strip and a downward extending tail with a pair of flat ears extending sidewise in opposite directions; said ears resting against said cam track such that said clip is adapted to be twisted to effect movement of said ears along said cam to a stressed position.

2. A terminal strip as claimed in claim 1 wherein the electrical insulating material is thermoplastic and is adapted to receive the clip ears embedded therein when said clip is twisted and heated.

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