US2197094A - Electrical connector - Google Patents

Description

' April 16, 1940. c, J, @HLAR 2,197,094

ELECTRICAL CONNECTOR Patented Apr. 16, 1940 r UNITED STATES,

2,197,094 I ELECTRICAL ooNNEc'roa Clarence J. Cihlar, Richmond, Ind., assignor to Belden Manufacturing Company, Chicago, 111., a corporation of Illinois Application March 30, 1938, Serial No. 198,795

1 Claim. (01. 173-322) My invention relates to electrical connectors and has particular relation to detachable plug connectors of the type used for connecting elec trical conductor cords to electrical appliances,

5' such as toasters, flat irons, and the like.

Connectors of this type usually comprise a hollow; elongated body of insulating material having a plurality, most frequently two, socket 1 type contacts supported in suitable open ended recesses formed therein. The individual conductors of the conductor cord with which the connector is used are attached to these socket type contacts within the insulating connector body by suitable screws or the like.

During use of conductor cords fitted with connectors of this type, it is very common practice for the user to effect the disengagement of the connector from the cooperating contact pins or the like forming a part of the appliance with which the connector is used by jerking or pulling the conductor cord. In substantially all of the connectorsheretofore known to the art, the stresses resulting from this pulling or jerking of the cord have been applied directly to the electrical connection between the cord conductors and the connector contacts with the result that injury to the connector, or its connections, or even to the user have occurred. Further, repeated application of such stresses tend to wear the cord insulation and create a serious fire hazard.

In fact, the potential dangers and hazards of these older type connectors are so great that the insurance underwriters have recently promulgated a rule which provides, in effect, that connectors of this type must be capable of sustaining a weight of fifty pounds applied between the contacts and the associated conductor cord for a period of five minutes without permitting separation of the cord conductors and the contacts even when the contact screws have been backed off sufficiently to substantially disconnect the conductors from the contacts.

This rule necessarily requires that connectors of the subject type must include a strain relief means for relieving the electrical connections from mechanical stresses during use, and the principal object of the present invention is to provide an improved strain relief for use in conjunction with connectors of this general type which will inherently prevent the, tensional stresses which may be impressed upon the conductor cord during use from; being transmitted to the electrical connection between the cordcon- 55 ductors and the connector contacts. .As will preparing a conductor cord for use with a conas to define in the assembled connector two elonhereinafter appear, the improved strain relief means of the present invention also accomplishes the further function of preventing lateral displacement of the component parts of the connector body. Other objects of theinvention are to provide an improved means for finishing the ends of conductor cords, which shall facilitate the assembling of those cords into the insulating bodies of the connectors with which they are used; to provide an improved strain relief and 10 cord finishing method which shall be relatively simple and inexpensive to practice and which may be utilized in' conjunction with existing types of connector structures W'lthllO more than slight modification thereof; to provide an improved strain relief and cord (finishing arrangement which shall utilize no metallic parts what soever, thereby minimizing insulation stresses and, fire hazards; and, generally, to provide an improved strain relief and connector embodying go the same.

Referring to the single "sheet 'of drawings wherein two preferred embodiments of the invention are illustrated Figure 1 is a perspective view of an electrical connector of the general type to which the present invention is particularly applicable;

Figure 2 is a sectional view on the general line 2-2 of Figure 1;

Figures 3, 4, and 5 are fragmentary views 'illus- 3'0 trating three steps in preparing the ends of a conductor cord in accordance with the present invention;

Figure 6 is a sectional View illustrating an intermediate step in the assembling of a conductor cord and connector embodying the present invention; b

Figure 7 is a fragmentary sectional view on the general line 7-1 of Figure 6; *Figure 8 is a view similar to Figure 6 showing 40 the connector and cord assembled in one of the halves of the insulating body; and

Figure 9 is a fragmentaryview, similar to Figures 3, l, and 5, illustrating a second method of nector embodying the present invention.

The body of the connector illustrated in the drawing comprises two cooperating half sections H which are adapted to be securely held together when the connector is assembled by a pair 59 of stiff, U-shaped springs 63 which engage and fit within suitable recesses l5 formed in the sides of the sections 1 l.- The opposed faces of the two cooperating half sections H are hollowed out so 5 gated recesses I! for receiving and positioning two socket type contacts l9 which are adapted to cooperate with contact pins or the like forming a part of the appliance with which the connector is used.

The contacts are of the conventional socket type such as are illustrated in U. S. Letters Patent No. 1,954,859, April 17, 1934, to Andre, and the recesses I! are preferably so formed that the socket contacts H! are securely held against movement relative to the plug body when the connector is assembled. The recesses H are, of course, open at the lower end of the plug body, as is illustrated in Figure 1.

The conductor cord 2! illustrated in the drawing is of the usual duplex or two conductor type provided with a braided outer covering. Each of the conductors 25 making up the conductor cord 2| includes a metallic cable 23 surrounded by a suitable insulating sheath. The conductorcord 2! is admitted to the interior of the connector body through a generally cylindrical cord receiving passageway 22 extending inwardly into the central portion of the upper end of that body. The inner end of the cord receiving passageway connects with the two contact receiving recesses I'l through suitable curved branch passageways 29, each of which is adapted to receive the end portion of one of the two conductors 25 making up the conductor cord 2!.

Tominimize bending and kinking of the conductor cord adjacent the connector body, the connector preferably includes an axially fieYible protector spring 3! the lower coils of which are adapted to be fastened to the connector body as by engaging the annular recess 33 formed as an enlargement of the cord receiving passageway 2l. A ferrule 35 may be provided at the outer end of this protector spring for engaging the cord proper.

In carrying out the present invention, the cooperating halves ll making up the connector body are provided with cooperating opposed recesses 31 or equivalent means which support a member such as the pin 39 so that it extends across the cord receiving passageway 21, preferably adjacent the inner end of that passageway. The pin 39 or like member is preferably of insulating material and is preferably provided with conically shaped or otherwise pointed ends. As will hereinafter appear, the pin 39 provides a convenient means whereby the connector cord 2! may be mechanically connected to the connector body so as to provide a strain relief for the electrical connections of the connector. In addition, the pin 39 serves to mechanically interconnect the two halves ll of the connector body so as to prevent lateral displacement of the body halves in the region of the pin 39 during use of the connector. The pin 39 or equivalent member should, of course, be of such dimensions that it does not more than partially close the cord receiving passageway.

Prior to the assembling of the connector, the braided covering of the conductor cord 2! is removed for a short distance so as to permit separation of the two conductors 25, as illustrated in Figure 3. Then, a suitable length of the metallic cable 23 forming a part of each of the conductors 25 is bared and attached to one of the socket type contacts 49, as is shown in Figure 3. Heretofore it has been customary to thereupon assemble the two half sections H of the body about these contacts. the adjacent end of the conductor cord2l occupying the central passageway 21 and the branched ends of the cord conductors 25 occupying the branched passageways 29. When so assembled, any force applied to the cord ll would be transmitted directly to the electrical connection between the cord conductors, and the socket contacts, the overcoming of which condition is the principal object of thepresent invention. In contrast with this, a conductor cord which is to be assembled into a connector provided with a pin 39 or like member extending transversely across the cord receiving passageway within the connector body, in accordancewith the present invention, is wound prior to being assembled with cord or thread 39', as is illustrated in Figures 4, 5, and 6, to provide a loop 4! in the conductor cord for engaging the pin 39 or other member which extends trans- The cord wrapping or winding 39' is best applied by first winding a suitable number of turns of double ply thread about both of the cord conductors 25 and about the end of the braided covering which remains on the conductor cord 25 after the contacts have been applied thereto, as illustrated at 43 in Figure 4. This wrapping may then be tied, and the individual conductors wrapped for a suitable distance by one of the double threads used in the initial wrapping. The

Wrapping may be continued with both threads.

to close the loop 4|, as illustrated at 45 in Figure 5, after which it is desirable to wrap the individual threads or cords over the remaining length a of each of the individual conductors, as is illus trated in Figure 6. This wrapping over the ends of the conductors adjacent the loop 4i holds the conductor insulation in place and also facilitates the assembling of the connector by making con ductor ends easier to handle.

When the conductor cord has been wrapped in this manner, it is assembled into one of the halves H of the insulating body by simply pressing the loop 4| over the pointed end of the pin 39, as is illustratedin Figures 6 and 7; The dimensions of this loop 4| preferably should be such that it will tightly grip the pin 39. Next,

the socket contacts [9 are located in the recesses H provided for them, and the wrapped end portions of the conductors 2! are placed in the branch passageways 29 which connect the central cord receiving passageway 21 with the socket receiving recesses l1. Thereupon, the other half of the connector body is put in position and the retaining springs l3 inserted in the recesses 15 so as to lock the body parts together.

Actual tests 'of a structure of this type show that it provides a most satisfactory strain relief and constitutes one of the few of such structures to be approved by the Board of Insurance Underwriters. The action of the strain relief pin 39 in mechanically interconnecting the body halves ll so as to prevent lateral displacement of those members efiectively, prevents relative movement of the several parts of the connector adjacent the strain relief means and adds much to the reliability and useful life of the connector. Moreover, it is much easier to assemble a connector and cord prepared in accordance with my invention than it is to assemble the structures heretofore used in the, art.- The tapered end on th transverse pin 39 which extends across the cord receiving passageway 21 and the wrapping of the exposed ends of the cord conductors 25 are important features in facilitating the assembling of the cord and connector.

It will be apparent that it is not necessary to extend the wrapping 39' along the entire exposed length of the two conductors 25 making up the cord 2!. The invention can be accomplished merely by providing two spaced wrappings 41 or equivalent means for joining the conductors 25 so as to define a loop 49 similar tothe loop II,

as is illustrated in Figure 9. It is preferred, however, to continue the wrapping over the entire exposed portions of both of the conductors 25,- since this greatly facilitates the assembling of It is my desire, therefore, that the accompanying claim shall be accorded the broadest reasonable construction consistent with what appears therein and with the prior art.

I claim the following as my invention:

In an electrical connector of the class described, a pairof cooperating half sections of insulating material assemblable by face to face contact to provide a connector body, said half sections adjacent said recesses, a pair of contacts supported by said body, a conductor cord having a pair of insulated conductors connected respectively to said contacts, said conductors being positionedin the passageway on opposite sides of the pin member, said conductors being tightly bound together adjacent the pin member at the side thereof facing the contacts with a thread or like wrapping, whereby said pin mernber functions also as a strain relief to prevent the bound portion of the conductors from being pulled outwardly from the passageway.

CLARENCE J. CIHLAR.

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