Patent Publication Number: US-4097107-A

Title: Insulation displacement terminal

Description:
This invention relates generally to electrical terminals and more specifically electrical terminals which make electrical contact with an insulated electrical wire by displacing portions of the insulation and engaging the conductor core. 
     A typical insulation displacement terminal is shown in U.S. Pat. No. 3,824,530 granted to Lincoln Edwin Roberts on July 16, 1974 for &#34;Installation of Electrical Connector or Wire Intermediate the Ends Thereof&#34;. The terminal 18 disclosed in the patent illustrates the typical approach to insulation displacement terminals in the use of a plate portion 24 or 26 having a narrow slot 30 or 32 which as an insulated electrical wire is pushed down into it displaces the insulation and engages the conductor core. A drawback of such a &#34;fixed slot&#34; terminal is that the slot is generally sized to accept a specific diameter conductor core thus requiring a different terminal for each size of insulated electrical wire. Another related drawback is that such &#34;fixed slot&#34; terminals are not well suited for stranded conductor cores which may not have a smooth outer surface or hold their shape as well as solid conductor cores. 
     The object of my invention is to provide an improved insulation displacement terminal which overcomes one or more of the drawbacks enumerated above. 
     Another object of my invention is to provide an insulation displacement terminal which accommodates various diameter cores. 
     Another object of my invention is to provide an insulation displacement terminal which is especially suited for insulated electrical wires having stranded conductor cores. 
     Yet another object is to provide an insulation displacement terminal having relatively movable end plate portions having slots which are designed to urge the conductor core toward the bottom or closed end of the slots under the bias of a spring portion of the terminal. 
     Yet another object of the invention is to provide an insulation displacement terminal having relatively movable end plate portions having slots which scrape the conductor core for good electrical contact while simultaneously energizing a spring portion of the terminal which subsequently biases the electrical wire against the bottom or closed end of the slots which assures good electrical contact with the scraped conductor core and prevents egress of the electrical wire from the slots. 
    
    
     Other objects and features of the invention will become apparent to those skilled in the art as the disclosure is made in the following detailed description of a preferred embodiment of the invention as illustrated in the accompanying sheet of drawing in which: 
     FIG. 1 is a side view of an insulation displacement terminal in accordance with this invention, 
     FIG. 2 is a front view of the terminal shown in FIG. 1 taken substantially along the line 2--2 of FIG. 1 and looking in the direction of the arrows, 
     FIG. 3 is a front view of the terminal similar to FIG. 2 showing the terminal operatively engaging an insulated electrical wire, 
     FIG. 4 is a section taken substantially along the line 4--4 of FIG. 3 and looking in the direction of the arrows, 
     FIG. 5 is a perspective view of the terminal shown in FIGS. 1 and 2 with a portion thereof broken away to illustrate otherwise hidden detail. 
    
    
     Referring now to the drawing and more particularly to FIG. 5 the terminal 10 comprises a unitary sheet metal body which may be conveniently formed from a strip shaped stamping which is reversely folded upon itself and bent into a double layered L-shaped body. More specifically the terminal 10 comprises a pair of rectangularly shaped end plate portions 12 and 14 juxtaposed one in front of the other in a closely spaced parallel relationship. Then parallel bottom edges of the end plate portions 12 and 14 are interconnected by a central flat spring portion 16 which is of hairpin shaped section and disposed generally perpendicular to the end plate portions 12 and 14. The bottom leg 16a of the spring portion 16 is connected to the back end plate portion 14 and the top leg 16b is connected to the front end plate portion 12. Consequently the spring portion 16 which is shown in its free unstressed state in FIGS. 1 and 2 permits but resists upward vertical movement of the front plate portion 12 with respect to the back end plate portion 14 from the position shown in FIGS. 1 and 2. The front plate portion 12 moves substantially parallel to the back plate portion 14 for a reasonable distance because of the shape and disposition of the spring portion 16. The bottom leg 16a of the spring portion 15 has a coplanar extension which serves as a male electrical contact 16c for mating connection with a female contact (not shown) and a central portion which is cut out and bent downwardly at an angle to serve as a lock tab 16d for locking the terminal 10 in a connector body cavity (also not shown). 
     The front and back end plate portions 12 and 14 have slots 18 and 20 respectively which extend laterally, that is, in the same general direction as the parallel bottom edges conneced by the spring portion 16. The slot 18 in the front plate portion 12 comprises a V-shaped open end 18a at the free side edge 12a; an outer enerizing portion 18b which converges toward the bottom edge in a direction toward the right as viewed in FIG. 2 and an inner scissors portion 18c which diverges from the bottom edge toward the right and terminates in a closed end 18d laterally spaced from the side edge 12a. The slot 20 in the back end plate portion 14 comprises a V-shaped open end 20a at the free side edge 14a, an outer energizing portion 20b which diverges away from the bottom edge toward the right as viewed in FIG. 2; and an inner scissors portion 20c which converges toward the bottom edge and terminates in a closed end 20d. 
     The terminal is illustrated with the spring portion 16 in a free unstressed state in FIGS. 1, 2 and 5. In this state, the V-shaped open ends 18a and 20a and the adjacent end portions of the outer energizing portions 18b and 20b are respectively aligned to simultaneously receive an insulated electrical wire 22 comprising a central conductive core 24 and an outer insulation layer 26. From their aligned end portions, the outer energizing portions 18b and 20b diverge away from each other and end at a location of maximum vertical displacement of the slots 18 and 20 from which location the inner scissors portions 18c and 20c commence and thence converge toward the vertically displaced closed ends 18d and 20d. 
     The slot portions 18b, 18c, 20b and 20c are preferably of substantially constant width approximately equal to the largest diameter of conductor core to be received therein. The terminal however does accommodate a smaller diameter core since it is the relatively movable upper edges 18e and 18f of the slot 18 forming a V and the lower edges 20e and 20f of the slot 20 forming an inverted V which are operative to first scrape the conductor core 24 for good electrical contact and then bias the electrical wire 22 against the closed ends 18d and 20d to make good electrical contact. When spring portion 16 is in the free or unstressed state the upper edge 18e of the outer energizing portion 18b of the slot 18 in front end plate portion 12 and the lower edge 20e of the outer energizing portion 20b of the slot 20 in the rear end plate portion 14 define an acute dihedral angle A perpendicular to the end plate portions 12 and 14 as shown in FIG. 2. Similarly the upper edge 18f and lower edge 20f of the respective inner scissors portions 18c and 20c form an acute dihedral angle B. The acute dihedral angle A is normally greater than the acute dihedral angle B so that the conductor core 24 is biased into engagement against the closed ends 18d and 20d under the action of spring portion 16 as shown in FIG. 3. 
     In operation, the insulated electrical wire 22 is placed in the aligned V-shaped open ends 18a and 20a of the slots 18 and 20. The edges defining these V-shaped open ends are preferably coined facilitating the piercing of the insulation layer 26 as the insulated electrical wire 22 is moved into the aligned end portions of the energizing portions 18b and 20b as shown in solid lines in FIG. 2. Further movement of the wire 22 to the right along the edges 18e and 20e causes vertical upward movement of the front plate portion 12 with respect to rear plate portion 14 against the resistance of the spring portion 16. The movement energizes the spring portion 16 and also causes the edges 18e and 20e to scrape the conductor core 24 under the bias of the energized spring portion 16. 
     When the conductor core 24 engages the vertex of the V formed by the edges 18e and 18f and the vertex of the inverted V formed by the edges 20e and 20f, the front plate portion 12 has moved up a distance D 1  from its original solid line position C to an uppermost portion which is represented by phantom line position C 1  of the top portion of the front plate portion 12. This position of the front plate portion 12 is not otherwise shown however it can readily be appreciated from FIG. 2 that the distance D 1  is the maximum vertical displacement of the front plate portion 12 and corresponds to the vertical distance between the aforementioned vertices in the free unstressed state of the spring portion 16 plus the diameter of the conductor core 24. 
     As the conductor core 24 passes the vertices and simultaneously enters the scissors portions 18c and 20c, the energized spring portion 16 causes the front plate portion 12 to move vertically downward with respect to rear plate portion 14 and the edges 18f and 20f of the respective scissors portions 18c and 20c in turn move the conductor core 24 toward the right and eventually bias the electrical wire 22 against the aligned closed ends 18d and 20d of the slots 18 and 20 as shown in FIG. 3. When the electrical wire is against the closed ends 18d and 20d, the front plate portion 12 has moved downwardly to the phantom line position C 2  shown in FIG. 1 which is at a lesser vertical distance D 2  above the original solid line position C. As noted from FIG. 4 which corresponds to the phantom line position C 2  shown in FIG. 1, the ends of the spring portion 16 attached to the end plate portions 12 and 14 are further apart than in FIG. 1 since the front end plate portion 12 does not return to its original position. Thus the slots 18 and 20 are configured such that the front plate portion 12 returns toward but does not reach its original position responsive to the electrical wire being received in the scissors portions 18c and 20c which assures a biasing of the electrical wire 22 against the closed ends 18d and 20d to make a good electrical contact with the terminal 10. 
     I wish it to be understood that I do not desire to be limited to the exact details of construction shown and described, for obvious modifications will occur to a person skilled in the art.