Patent Publication Number: US-3875324-A

Title: Wire connector

Description:
United States Patent Waddington et 21.  
 Apr. 1, 1975 [54] WIRE CONNECTOR FOREIGN PATENTS OR APPLICATIONS 1 1 lnvemorsl William Waddington, Faflwood; 777,950 2/1968 Canada 174/87 Charles F. Mazzeo, Scotch Plains, both of N]. L C Primary Examiner-Darrell lay [73 1 Asslgnee&#39; fi v Corporatmn New York Attorney, Agent, or Firm-Samuelson &amp; Jacob [22] Filed: May 31, 1973 21 Appl. No.: 365,548 1571 ABSTRACT A wire connector in which installation torque is trans- [52] U.S. Cl. 174/87, 403/18 mitted from an insulating housing to a tapered spring [51] Int. Cl H01r 5/12, HOZg 15/08 connector member contained within a cavity in the [58] Field of Search 174/87, 138 F; 287/75, housing through threaded engagement between a con- 287/78; 403/18 volution at the smaller end of the spring member and the housing at the corresponding end of the cavity. [56] References Cited UNITED STATES PATENTS 1 Claim, 4 Drawing Figures 3.519 707 7/1970 Krup 174/87 R WIRE CONNECTOR The present invention relates generally to wire conne&#39;ctors for securing a connection between electrical wire ends by rotational installation of the connector over the wire ends and pertains, more specifically, to a wire connector in which installation torque is transmitted from an insulating housing to a tapered spring connector member contained within a cavity in the housing through threaded engagement between the spring member and the housing.  
  Wire connectors have proved to be highly effective in providing a simple means for securing electrical wires together, both mechanically and electrically, in many different installations and have gained a high degree of commercial acceptance. As a result. a wide variety of such devices has been developed in an effort to simplify their design and construction while increasing their operating effectiveness. In such devices, the wires are connected by a tapered, helically coiled spring member contained within a housing of insulating material having a closed end such that the connection is insulated electrically. The device is turned onto the ends of the wires with installation torque being transmitted from the housing to the spring member. With some existing connectors. it is possible to make a connection which is unsafe and actually hazardous. In particular, in connecting solid wires where the wire ends are not precisely aligned longitudinally with one another. the following several distinct hazardous conditions can occur.  
  First, the electrical wires can be threaded into the connector with such force that the wire which is advanced longitudinally further than the remaining wires can actually drill through the insulation material of the housing at the closed end.  
  Second, the wires can be threaded into the connector with sufficient force so that the furthest advanced wire strikes the closed end of the housing. Ifthe closed end of the housing resists penetration of the wire, and if additional torque is applied, the wire can act like a screw and the spring member can act like a nut, thus developing a force that can drive the spring member in the direction away from the closed end of the housing toward the open end. Unless there is a sufficiently strong supplementary means for retaining the spring member inside the housing. the spring member can partially back out of the housing. creating a hazardous condition.  
  Third. with only one or two convolutions of the spring member gripping the wires. the furthest advanced wire can strike the non-resistant closed end of the housing. Continued rotation of the connector will cause movement of the spring member away from the closed end of the housing thereby disengaging the driving coupling between the housing and the spring member and leaving only a limited connection between the spring member and the wires. A strong pull on either wire could pull the wire from the connector.  
  It is therefore an object of the invention to provide a wire connector which overcomes the above limitations and thus precludes the occurrence of the hazardous conditions outlined above.  
  Another object of the invention is to provide a wire connector with an improved coupling arrangement between the spring member and the housing of the connector for transmitting installation torque from the housing to the spring member.  
  Still another object of the invention is to provide a wire connector in which considerable torque can be applied to the connection between wires without slippage between the housing and the spring member of the connector.  
  A further objectof the invention is to provide a wire connector with a simplified construction having component parts which are easy to manufacture. assemble and use.  
  The above objects, as well as still further objects and advantages. are attained by the invention which may be described briefly as a wire connector for securing a connection between electrical wire ends by rotational installation over the wire ends, the wire connector comprising a helically coiled spring member extending longitudinally from a larger diameter first end toward a smaller diameter second end, the spring member being generally tapered longitudinally along a central portion between the ends thereof and having a plurality of convolutions, and a housing of relatively rigid insulating material, the housing having a cavity containing the spring member, the cavity having a configuration generally complementary to the external configuration of the spring member with the relative dimensions of the cavity and the spring member providing a clearance space between the housing and the central portion of the spring member, the cavity including an end portion adjacent the second end of the spring member, that end portion having a diameter smaller than the outside diameter of at least one convolution adjacent the second end of the spring member, the one convolution having a thread-forming edge along the outside periphery thereof such that rotation of the housing relative to the spring member in the direction of installation will form a complementary thread in the housing at the endportion to establish a threaded engagement between that one convolution and the housing for transmitting installation torque from the housing to the spring member.  
  The invention will be more fully understood, while still further objects and advantages will become apparent, in the following detailed description of a preferred embodiment illustrated in the accompanying drawing. in which:  
  FIG. 1 is a plan view of a wire connector constructed in accordance with the invention;  
 FIG. 2 is an end view of the wire connector;  
  FIG. 3 is an enlarged cross-sectional view taken along line 3-3 of FIG. 1, together with a pair of electrical wires to be connected;  
  FIG. 4 is a view similar to FIG. 3, but with the wire connector installed over the ends of the electrical wires. 1  
  Referring now to the drawing, and especially to FIGS. 1 through 3 thereof, a wire connector constructed in accordance with the invention is illustrated generally at 10 and has a housing 12 of relatively rigid dielectric material and a helically coiled spring member 14 fixed within the housing 12.  
  Housing 12 is of unitary construction and preferably is molded of a synthetic resin having desirable strength and toughness as well as the requisite electrical insulating properties. The housing is generally in the form of a shell providing an internal bore or cavity 16 extending from an open end 18 of the housing 12 to a closed end 20, a first part 22 of the cavity 16 having an internal diameter great enough to receive the ends of insulated electrical wires 24 and 26 to be placed within the wire connector and a second part 28 having an internal contour generally complementary to the external configuration of the helically coiled spring member 14, as will be explained in more detail hereinafter.  
  As outlined above, it is the function of a wire connector to secure firmly together a plurality of wires to establish a fast mechanical joint as well as a good electrical connection between the ends of the wires. The wires 24 and 26 are received within the wire connector 10 through the open end 18 and are engaged by the spring member 14 by twisting the wire connector to longitudinally advance the wires from open end 18 toward closed end 20, the engagement of spring member 14 with the wires 24 and 26 being likened to a screwthreaded engagement.  
  In order to facilitate grasping and turning of the wire connector during installation, the exterior of the housing 12 is provided with a pair of cars 30 extending laterally outwardly. Ears 30 may be gripped conveniently by an operators fingers to enhance the ability of the operator to twist the wire connector as the connector is advanced along the wires 24 and 26. The particular configuration of the ears 30 also serves to indicate the direction of rotation for installation, as illustrated by the arrow in FIG. 2.  
  Turning now to FIG. 4, as well as to FIGS. 1 through 3, spring member 14 is provided with a plurality of convolutions 32. In order to grip the wires 24 and 26 firmly. the convolutions 32 have an internal edge 34 for permanently deforming the wires by pressing a groove into the wires as the wire connector is advanced over the ends of the wires during installation. The spring member 14 is generally tapered from a larger diameter at first end 36 to a smaller diameter at second end 38, the taper being established by intermediate convolutions of consecutively smaller diameter extending along the central portion 40 of the spring member lying between the first and second ends 36 and 38, respectively. These intermediate convolutions are resiliently expansible so that a variety of wire sizes can be accommodated by resilient dilation of the convolutions as the spring member 14 is advanced over the wires. The difference between the inside diameter of the cavity 16 adjacent the intermediate convolutions and the outside diameter of the intermediate convolutions along the central portion 40 of the spring member 14 establishes a clearance space 42 which accommodates the desired resilient expansion of the intermediate convolutions. The ability ofthe intermediate convolutions to expand and contract resiliently also serves to maintain a relatively constant gripping force upon the Wires through cycles of heating and cooling which may be encountered during service.  
  In order to couple the spring member 14 for rotation with the housing 12 during installation of the wire connector 10 over wires 24 and 26, the relative dimensions of the cavity 16 adjacent closed end and the convolution at the second end 38 of the spring member are such that an interference fit is established between the housing and the spring member adjacent the second end 38 sufficient to transmit the requisite driving torque for installation. Thus, the inside diameter of the end portion 44 of the cavity 16 is smaller than the outside diameter of the convolution 46 ofthe spring memher.  
  As best seen in FIG. 3, prior to installation. end portion 44 has no thread complementary toconvolution 46 but merely receives convolution 46 at the entrance to end portion 44 with a slight interference fit. The convolution 46 has a thread-forming edge 48 along the outside periphery of the convolution so that relative rotation between the housing 12 and the spring member 14, as the housing is rotated in the direction of installation, will establish a complementary thread 50 in end portion 44 and thus provide a threaded engagement between the convolution 46 and the housing 12. As such relative rotation is continued, a deeper thread 50 is established in the wall of the housing by a combination of pressing and cutting of the housing material by the end portion of the spring member at end 38 in response to installation of the wire connector 10 upon the wires 24 and 26. In order to assure the formation of such a deeper thread and thus enhance the coupling between the housing and the spring member, the end portion 44 of the cavity 26 is tapered toward a smaller diameter at the end wall 52 of the housing 12. Relative rotation between the housing and the spring member will stop when the end 38 of the spring member bears againstthe end wall 52 of the housing. Continued turning of the housing will merely thread the wires 24 and 26 deeper into the spring member 14.  
 Preferably, the wall thickness of the end wall 52 and.  
 the wall thickness of the wall of the housing along end portion 44 is greater than the predetermined wall thickness of the remainder of the housing so as to reinforce the housing in the vicinity where the spring member is coupled to the housing. Additionally, the thickness of the end wall 52 is great enough to withstand the thrust of the end 54 of wire 24 against the end wall. Furthermore, by limiting the inside diameter of the convolution 46 at the small end 38 of the spring member 14 to that which will not permit the passage through convolution 46 of a wire having sufficient column strength to pierce the end wall 52 of the housing. such failure of the housing is prevented.  
  Manufacture and assembly of the component parts of the wire connector 10 is simplified by the abovedescribed structure. Thus, the spring member 14 need merely be placed within the housing 12 wherein the spring member is retained by place by lip 56 which projects into the cavity 16 at the large end 36 of the tion. Manufacture ofthe housing is simplified in that no special structure, such as abutments or threads, is required at the closed end 20 of the housing, nor is any thread required adjacent the lip 56 or anywhere along the cavity 16. Assembly is simplified in that angular orientation of the spring member 14 relative to the housing 12 is not critical when the spring member is inserted into the housing.  
  It is to be understood that the above detailed description of a preferred embodiment is provided by way of example only. Various details of design and construction may be modified without departing from the true spirit and scope of the invention as set forth in the appended claims.  
  The embodiments of the invention in which as exclusive property or privilege is claimed are defined as follows:  
  1. As an article of manufacture, a wire connector for securing a connection between electrical wire ends by rotational installation over the wire ends, said wire connector comprising:  
 a helically coiled spring member extending longitudinally from a larger diameter first and toward a smaller diameter second end, said member being generally tapered longitudinally along a central portion thereof between said ends and having a plurality of convolutions;  
 a housing having a wall of relatively rigid insulating material. said housing having a cavity containing said spring member, the cavity having a configuration generally complementary to the external configuration of the spring member with the relative dimensions of the cavity and the spring member providing a clearance space between the housing and the central portion of the spring member, said wall having a predetermined wall thickness along the portion of the length thereof corresponding to the tapered longitudinal central portion of the spring member;  
 said housing including a lip projecting into the cavity adjacent the first end of the spring member and retaining the spring member within the cavity prior to said rotational installation, and an end wall adjacent the second end of the spring member; and  
 coupling means for transmitting installation torque from the housing to the spring member, upon said rotational installation, and subsequently precluding relative longitudinal movement between the spring member and the housing, said coupling means consisting of:  
 an unthreaded end portion of said cavity, said end portion having a given inside diameter at the outside periphery of at least one convolution adjacent said second end of the spring member, the thickness of the wall at the unthreaded end portion of the cavity and at said end wall being greater than said predetermined wall thickness; and  
 a thread-forming edge along the outside periphery of at least said one convolution adjacent the second end of the spring member, said threadforming edge having an outside diameter larger than the given inside diameter of the unthreaded end portion of the cavity by an amount great enough to enable, upon rotation of the housing relative to the spring member in the direction of said installation, the formation of a complementary thread of sufficient depth in the thicker housing wall at said unthreaded end portion to establish a threaded engagement between the said one convolution and said housing of a strength great enough to transmit said installation torque and preclude said longitudinal movement;  
 said one convolution having an inside diameter small enough to preclude the passage through the convolution of a wire having sufficient column strength to pierce the end wall.