US3206833A - Method of making an electrical connector - Google Patents

Description

P 1965 J. L. YONKERS 3,206,833

METHOD OF MAKING AN ELECTRICAL CONNECTOR Filed July 23, 1963 MW. cfofzzzfi YOVZ/ff/ZS ROBERT L.KA HN ATTY United States Patent 3,206,833 METHOD OF MAKING AN ELECTRICAL CONNECTOR John L. Yonkers, Northbrook, Ill. Electro-Appliance Co., Inc., 1915 N. Elston St., Chicago, Ill.) Filed July 23, 1963, Ser. No. 296,980 1 Claim. (Cl. 29155.5)

This invention relates to an electrical connector and more particularly to a connector using a tapered helical spring disposed within an insulating body. The invention also relates to a method of making the new connector.

Wire connectors generally to which this invention relates have a tapered metal helical spring into which wires to be connected are twisted. This spring is disposed within a rigid insulating body. This construction has some serious disadvantages. For one thing, twisting a wire connector over a number of copper wires makes it necessary for the rigid insulation to be strong enough to withstand the force exerted by the spring in tending to go over the wires to be connected. Considerable force tending to expand the coil diameters of the small end against the housing body is created. This may crack the housing body. The use of pliers on such connectors can be dangerous. The bite of the jaws of a plier on the insulating body may crack the same. Also the use of pliers to twist the wires deeper into the connector may result in cracking the connector body as pointed out. In addition, the spring within the housing body may become so firmly attached to the wires to be connected that the spring is separated from the insulating body and permits the body to drop or separate.

The present invention provides a wire connector having a spring member completely disposed within an insulating housing, which need not be rigid and is preferably flexible. The spring member has a helical spring connector portion which is preferably though not necessarily tapered and an anchor portion which is firmly attached to the insulating housing body. The helical connector spring portion is available for use as a connector for wires to be disposed therein but itself is not attached to the housing body. The insulating body, when flexible, provides a number of substantial advantages. One is that the connector and wires to be connected may be turned relative to each other over a range which is not sharply defined without damage to the insulating housing body. In addition, it is diflicult to destroy the connection between the anchor portion of the spring member and the housing body. Hence the new connector, whenever applied to wires for connection purposes, will not expose the joined wires. In addition, as will be apparent later, the new connector permits the spring coils to readily adapt themselves completely to wires to be connected.

The invention generally provides that coils or turns making up the anchor portion of a spring member have plastic molded completely around the individual wires for anchoring the spring to the insulating body housing. The remainder of the tapered helical spring is free of the plastic and is available for connecting purposes, the entire spring being disposed within the insulating body housing. In general, it is preferred to have the spring conneetor portion to be anchored at the large end of a tapered helical spring. This disposition has advantages which will be apparent after the invention has been described. However, the anchor portion of the spring may be at either end or at some intermediate portion of the helical spring. Generally, the turn or turns of the helical spring forming the anchor portion thereof will have sulficiently large diameter so that the anchor turns will clear the bare wires being joined. In other words, the function of the anchor portion of the spring is purely for anchor- 3,206,833 Patented Sept. 21, 1965 age purposes and is not concerned with electrical connecting.

The procedure for making connnectors embodying the present invention involves two steps which are essential for quantity production. One step involves the application of a priming coating of plastic to the anchor portion only of the helical coil spring. In its simplest form, this involves the application of an epoxy resin coating to the anchor turns of the spring only. The other step involves the application to the entire spring member, including the primed anchor portion, of a plastic coating having the property of not adhering to unprimed metal and also having desired physical properties of toughness and electrical insulation. The second step is most conveniently accomplished by having a mandrel carry the spring member and shaped to fill the space within the turns of the connector portion while leaving space between the mandrel and anchor turns. Plastic is thereupon applied to the entire spring member and mandrel. The mandrel is of a material to which the plastic will not adhere. The plastic may be applied by dip-coating or by a variation known as fluidized bed coating. .The dip coating procedure utilizes a liquid bath of a plastic such as polyvinyl chloride (PVC) or vinyl latex into which the mandrel and spring, at a suitably high temperature, are dipped and withdrawn. utilizes a finely divided solid plastic, as polyethylene, which is blown over the work to be coated.

'Such plastic materials used for coating metals in general do not adhere strongly to metal, s0 that unprimed portions of the spring member will not be firmly secured to the plastic. However, many-if not mostof the plastics used for coating will bond to an epoxy resin primer coating.

'For a more complete description of the invention, reference will now be be made to the drawings wherein:

FIGURE 1 shows a perspective view, with a portion broken away, of a connector embodying the present invention, three wires to be joined being shown in dotted form.

FIGURE 2 is a section on line 22 of FIGURE 1, with the addition of a mandrel for illustrating the connector immediately after the clipping procedure for mak: ing the same.

FIGURE 3 is a perspective view of the spring.

FIGURE 4 is a view in diagrammatic form illustrating a means for dip-coating a spring member carried by a mandrel.

The new connector has a metal spring member which includes helical spring 10 here shown as of the tapered type having small end 11 and large end 12. The spring metal used may be brass, copper plated steel, phosphor bronze, or any of the metals used in connectors of this general type presently available on the market. Tapered helical spring 10 is illustrated as having a generally smooth taper for most of the length of the spring, although this is not essential. In the form illustrated here, spring .10 has about two large turns 13 and 14 extending from large end 12. Turns 13 and 14 have a large diameter than turn 12, for example, which is the largest diameter turn of the uniformly tapered body portion of the spirng. Turns or coils 13 and 14 function as the anchor portion of the spring member while spring 10 functions as the connector portion. The pitch of end turns 13 and 14 is increased over that of portion 10 so that these end turns or coils are spaced from each other along the axis of the spring member a short distance. The amount of spacing is unimportant so long as there is suflicient space for plastic to be disposed between the coils of the anchor portion of the spring member.

Similarly, the increase in diameter of the coils of the anchor portion is not important with regard to the amount The fluidized bed coating procedure of increase except that the increase should be sufficient so that the end turns forming the anchor portion of the spring can be completely embedded in plastic, while leaving the rest of the spring free. However, the change, insofar as the pitch and diameter of the anchor turns of the spring member, can be eliminated with flexible plastic and the end turns of a helical spring having a more or less uniform taper can be utilized as the anchor portion. While the turns of spring connector portion are shown as being closely spaced, that is not essential.

The completed connector, as illustrated in FIGURES 1 and 2, has anchor portion turns 13 and 14 securely bonded to plastic housing body 20. This is obtained by priming anchor turns 13 and 14 with a thin layer of epoxy resin. It is understood that the anchor portions to be primed must be suitably prepared to be clean and free of grease so that the epoxy resin will bond to the metal. The turns of connector spring portion 10, beginning with turn 12 and ending with small end 11 are not bonded to plastic 20 by the simple expedient of leaving the metal un primed. As illustrated in FIGURE 2, plastic housing body 20 has portion 21 which is disposed within one or two end turns of the spring at the small end. This can be avoided if desired, but is generally not objectionable.

By having the anchor portion at an end of the spring member, a simple dipping operation can apply liquid epoxy resin to those turns only. Thereafter the spring member is heated to cure the primer layer. In some instances, heating the primer layer may not be necessary, depending upon the resin used.

The plastic for body 20 can be any one of a number of plastic materials which do not bond to unprimed metal and are tough and can be applied as a coating. Examples of such plastics are polyvinyl compounds, particularly the chlorides, nylon, polyethylene, rubber. Polyvinyl chloride is widely used for dip-coating and is excellent for use here.

In order to manufacture the connector thus far described, it is practically necessary to use a mandrel. If dip-coating is to be utilized, then mandrel 25 will have to be of metal for retaining and conducting heat at a desired rate. Thus mandrel 25 may be of aluminum, copper, brass or steel. Mandrel portion 27 is shaped to fit snugly Within connector portion 10 of the spring member. Mandrel portion 27 has part 28 which is disposed to clear anchor portion turns 13 and 14 of the spring member. In order to prevent excessive buildup of plastic at this region, the mandrel may be undercut at region 28 and provided with collar 30 of a material like Teflon. This material, as is well known, can withstand a much higher temperature than most plastics and has a greasy surface to which most plastic materials will not adhere. Heat exchange between the mandrel metal and the plastic being applied is affected. Build-up of the plastic coating material can be controlled. However, collar 30 may be omitted if desired or may be of metal.

With mandrel 25 disposed within spring connector portion 10 as illustrated in FIGURE 2, the formation of plastic housing 20 can be initiated. In dip-coating, mandrel 25 is suspended to be in a vertical position as illustrated in FIGURE 4. The mandrel and spring are preheated to about 400 F. for P.V.C. dip-coating and then dipped into bath 34 of liquid P.V.C. maintained at a constant temperature and level. The mandrel and spring are quickly dipped into the bath to the desired depth and are pulled upwardly from the bath at a predetermined rate. Whenever the withdrawal rate is slowed, the amount of plastic deposited around the mandrel and spring will increase in thickness. As a result, many shapes for insulating body 20 are possible. The preheating step may be utilized for curing the epoxy resin primer layer.

A simple means for controlling the withdrawal of the mandrel and spring from the bath is illustrated in FIG- URE 4 wherein cam 36 operates on cam follower 37 carried by arm 38 for raising the mandrel. It is understood 4 that in practice, a large number of mandrels are supported for a simultaneous handling. After dip-coating, the work (P.V.C. body) is heat treated for fusing the plastic. All this is conventional in dip-coating.

Any desired spring shape can be selected. In all cases, the mandrel is so designed that a spring can be attached to a mandrel by friction. With plastic material deposited about the mandrel above anchor turns 13 and 14, a plastic skirt will be created which will more than cover any bared wires to be connected.

The completed connector is removed from its mandrel. The shape of the connector housing makes it possible to blow a connector free of a mandrel by compressed air passing through an axial bore in the mandrel.

Various mandrel shapes are possible. So long as the mandrel fills the region within helical spring connector portion 10, no plastic can surround the wire so that the spring metal bearing on the mandrel surface will remain uncoated. By having clearance between the mandrel and the anchor turns, the plastic material can enclose and bond to the primed metal. Because of the twisting of wires when used in a connector, the absence of a strong bond to metal may result in the spring being disconnected from the plastic housing body. It is possible to provide a large number of anchor turns and omit the priming.

The gauge of spring wire can be about the same as that of Wire connectors now available. In contrast to such wire connectors now available, the spring wire gauge can also be heavier because of the freedom of individual spring coils to move or shape themselves. Thus the coils of the spring in the new connector can move axially of the helical spring to accommodate irregularities of the Wires to be connected. Also the coils can increase in diameter locally to accommodate the wires being connected. Thus if there is an enlargement in the wires being connected, the spring coils can successively accommodate themselves as the wire connector is twisted and after the obstruction has been passed, the wire coils can contract to normal size. As a result, the new connector can have many more spring coils over a length of wires to be joined than a conventional wire connector whose spring coils are fixed for diameter or pitch or both.

In wire connectors, the direction of turning of the wire connector with respect to wires to be connected is such that when turning a wire connector to tighten it there is a tendency (which is resisted in conventional wire connectors by the rigid body) to create forces to expand or open one or more spring coils. This tendency for expanding the spring coils comes into play particularly when the shape or arrangement of wires being connected tends to bind in the helical spring coils. A conventional Wire connector will bind in such cases and prevent the Wire connector from being fully applied. In such case, the use of pliers may be relied upon to turn the connector, in which case the rigid insulating body is frequently cracked. If no attempt is made to turn such wire connector any further, there is a possibility that the wire connector is not fully positioned and may permit Wires to work loose under vibration or will provide insufiicient contact area for the wires and spring.

By contrast, the new wire connector with a flexible housing body can be turned over wires and permits the spring coils to expand their diameter or even to move laterally of the entire helical spring and pass the block or obstruction. As the new wire connector progresses along the wires being connected, the particular coils which may have expanded or which may have moved laterally can assume their normal condition and position. Consequently, the new wire can be turned, and without excessive force, to an end position where wires to be joined are well within many coils of the helical spring. with the spring coils exerting a compressive force upon the wires to establish good electrical contact over large areas of wire and spring.

T e new Wire connector with flexible housing can be turned by hand without tools and without the need for great force. The adaptability of the spring coils with regard to coil diameter, and lateral movement of coils, thus assures that the new wire connector, when turned by hand, can be turned to a final position where the wire connector is moved to the limit of its travel. As a result of this adaptability, the new wire connector can use heavier gauge wire for the helical spring as compared to conventional wire connectors. Furthermore, one particular size of new wire connector provided with a flexible housing can cover a greater range of connector requirements than is true of conventional wire connectors.

The new wire connector with flexible housing provides a still further advantage in some applications, such as in lighting fixtures, household appliances, and the like. In such devices, the new wire connector with a flexible housing will function to dampen any vibration or 60-cycle hum which may be present. Thus, for example, in ballasts for fluorescent lighting, a 60-cycle hum may be accentuated by a rigid insulating housing for a wire connector providing a vibration conducting path between the ballast core and the sheet metal of the fixture.

What is claimed is:

A method of making a wire connector comprising winding a length of spring wire to provide multi-coil tapered helix connector portion and a co-axial anchor portion having at least one helical coil extending away from the large end of said connector portion helix along the axis thereof, said anchor portion having the coil diameter significantly larger than warranted by the connector portion helix taper, priming the wire of the anchor portion only with a coating of epoxy resin, disposing the entire length of spring wire having the aforementioned shape over the tapered end of a mandrel of good heat conducting metal and shaped so that the tapered end of the mandrel provides a snug friction fit within the coils of the connector portion only, the mandrel portion within the anchor coil portion being small enough to provide annular clearance between the mandrel surface and anchor portion metal, said mandrel being longer than the overall length of the shaped wire to leave a mandrel end portion clear beyond the anchor portion of the shaped wire, positioning said mandrel so that its length is vertical with the tapered end carrying the shaped wire being at the bottom, moving the mandrel vertically down into a molten bath of vinyl plastic to immerse the entire length of shaped spring wire into said bath and then raising said mandrel from the bath at a predetermined rate, to permit molten plastic to congeal about the shaped metal, said mandrel raising the entire length of spring wire together with the congealed mass of plastic, said mandrel conducting heat from the bath to atmosphere to congeal the molten plastic and create a plastic shroud which covers the small end of the connector heliv portion and extends along the outside only of the connector portion toward the anchor portion and continues along both the inside and outside of the anchor coil portion and about the wire making up the anchor coil portion to embed such anchor coil portion wire, the plastic being firmly cemented to the anchor coil portion wire, and thereafter removing said finished wire connector from the tapered end of said mandrel.

References Cited by the Examiner UNITED STATES PATENTS 2,110,458 3 3 8 Applegate l7487 FOREIGN PATENTS 637,564 3/62 Canada.

JOHN F. BURNS, Primary Examiner. JOHN P. WILDMAN, E. JAMES SAX, Examiners.

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