Abstract:
A screw assembly for use with an electrical connector securing a conductor includes a threaded body configured to be releasably coupled to a coupling portion of the connector. A contacting structure includes a plate spaced from the threaded body and has a flat contacting surface configured for contacting the conductor. The plate is coupled to the threaded body. The plate is rotatable relative to the threaded body when the threaded body is coupled to the coupling portion of the connector. The plate is restricted from movement away from said threaded body when the threaded body is not coupled to the coupling portion of the connector. A spacer may be positioned between the plate and the threaded body and is configured to urge the plate away from the threaded body.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to electrical connectors and, more particularly, to wire-contacting screw assemblies for use with such connectors. 
       BACKGROUND OF THE INVENTION 
       [0002]    Various types of electrical connectors are used for connecting electrical conductors to one another or to the terminals of electrical devices. Conventional connectors receive a conductor within a channel or the like and then receive a screw. The screw is then tightened against the conductor so that it is held in physical contact with the connector. 
         [0003]    Known conductors are made of a soft material such as copper or aluminum and may further be defined by a series of individual bare strands. Conventional connectors and, more particularly, screws used with such connectors, may have a tendency to damage the conductors. Pointed, angled or tapered screw configurations often dent or damage the strands. 
         [0004]    Connections between connectors and conductors may also involve different materials. For example, the screw of a connector may be made of one material while a conductor may be made of another. Different materials may have different rates of expansion and contraction. Accordingly, the life span of the connection and/or the temperatures to which the connector and conductor may be subject to lead to relative movement between the connector and the conductor. This movement causes loosening of the connection, which leads to an inadequate electrical connection between the parts involved. 
         [0005]    Loose connections may also arise from different degrees of elasticity of the parts involved. More particularly, one element may exhibit one degree of elastic deformation during engagement of the screw with the conductor, while another material will exhibit a different degree of elastic deformation. These different degrees of elastic deformation lead to different degrees of material recovery, which may result in loose connections. 
         [0006]    Known connectors may be used in areas subject to relatively high degrees of vibration. In such types of environment, vibration may similarly lead to loose connections between the conductor and the connector. More particularly, vibration may lead to movement of the screw relative to the connector. This relative movement, in turn, loosens the physical contact between them. As a way to compensate for this observed loosened connection, a user often performs periodic maintenance to retorque the connection. Without such maintenance, the loose connection may eventually result, for example, in elevated operating temperatures in the connection, which in turn may result in a failed connection. 
         [0007]    Therefore, it is desirable to have a connector and a corresponding screw that address the drawbacks of conventional connectors and corresponding conventional screws. 
       SUMMARY OF THE INVENTION 
       [0008]    These and other problems in the prior art have been addressed with this invention. In one embodiment according to this invention, a screw assembly for use with an electrical connector secures a conductor and includes a threaded body configured to be coupled to a coupling portion of the connector. A plate is spaced from and coupled to the threaded body and has a flat contacting surface configured for contacting the conductor. The plate is coupled to the threaded body to enable rotation of the plate relative to the threaded body. The plate is restricted from movement away from the threaded body when the threaded body is not coupled to the coupling portion of the connector. A spacer is positioned between the plate and the threaded body and configured to urge the plate away from the threaded body. The spacer may alternatively or additionally be configured to deflect toward the threaded body when the plate contacts the conductor. The plate may be rotatable relative to the spacer. In specific embodiments, the plate is configured for movement toward the threaded body. Coupling of the plate to the threaded body may define a unitary structure configured to be releasably coupled to the connector. 
         [0009]    In another embodiment, an electrical connecting assembly for securing a conductor includes a connector body configured to receive the conductor. A threaded body and a contacting structure are assembled as a unitary structure. The threaded body is releasably coupled to a coupling portion of the connector body. The contacting structure includes a plate spaced from the threaded body and which has a flat contacting surface configured for contacting the conductor. The plate is coupled to the threaded body such that the plate is rotatable relative to the threaded body when the threaded body is coupled to the coupling portion. The plate is restricted from movement away from the threaded body when the threaded body is not coupled to the coupling portion. 
         [0010]    In another embodiment according to this invention, a method of securing a conductor to a connector includes positioning the conductor within the connector. A first portion of a unitary structure is releasably coupled with a coupling portion of the connector. A second portion of the unitary structure engages the conductor. The first and second portions are spaced from one another. The method includes rotating the second portion of the unitary structure relative to the first portion when the first portion contacts the conductor. In a specific embodiment, the method further includes deflecting the second portion toward the first portion when the second portion contacts the conductor. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0011]    The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
           [0012]      FIG. 1  is a perspective view of a connector and screw assembly in accordance with an embodiment of this invention; 
           [0013]      FIG. 2  is a perspective view of the screw assembly of  FIG. 1 ; 
           [0014]      FIG. 3  is a disassembled perspective view of the screw assembly of  FIG. 2 ; 
           [0015]      FIG. 4  is another disassembled perspective view of the screw assembly of  FIGS. 2 and 3 ; 
           [0016]      FIG. 5  is a cross-sectional view taken generally along lines  5 - 5  of  FIG. 4 ; 
           [0017]      FIG. 6  is an assembled cross-sectional view of the screw assembly of  FIG. 5 ; 
           [0018]      FIG. 7  is a cross-sectional view of the connector and screw assembly of  FIG. 1  contacting a conductor; and 
           [0019]      FIGS. 8-17  are perspective views of alternative embodiments of a plate of the screw assembly according to this invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0020]    With reference to the drawings and, more particularly to  FIG. 1 , a connector  10  according to one embodiment of this invention includes a connector body  12  that is adapted to receive one or more conductors  14 . To that end, the connector body  12  includes a lateral aperture  16  that permits introduction of the conductor  14  into and/or through the body  12 . The body  12  includes a bore  18  having an axis  18   a,  extending from a top surface  19  of the body  12 , and which is defined by a threaded wall  20  for receiving a screw assembly  22  to be described in further detail below. In this exemplary embodiment, the body  12  has a generally square cross section, although persons of ordinary skill in the art will readily appreciate that other shapes are similarly contemplated. The body  12  may further include an extending portion (not shown) which permits coupling of the body  12  with other components. To that end, the extending portion may include a secondary aperture to facilitate such coupling. Moreover, while only one bore  18  is shown, any number, configuration and arrangement of bores are within the scope of this invention. 
         [0021]    As noted above, the body  12  is adapted to receive one or more conductors  14 . More particularly, the body  12  of this exemplary embodiment includes a lateral aperture  16  that defines a lateral bore  26  extending through the body  12  in a direction generally transverse to the axis  18   a  of the bore  18 . This transverse orientation of the lateral bore  26  permits, as explained below, securement of the conductor  14  within the body  12  via engagement of the screw assembly  22 . The lateral bore  26  is suitably sized to receive a range of sizes of conductors  14 . The conductor may be defined by multiple strands  14   a.  The lateral bore  26  therefore, is suitably sized to receive the strands  14   a  which may in some cases diverge in different directions. The lateral bore  26  moreover extends between opposed side walls  30  of the body  12 . 
         [0022]    With reference to  FIGS. 1-6 , the screw assembly  22  is a unitary structure and engages the body  12  of the connector  10  through engagement of the threaded wall  20  of the bore  18  with exterior threads  34  of the screw assembly  22 . More particularly, the screw assembly  22  engages the body  12  of the connector  10  in such a way that the screw assembly  22  is releasably coupled to the body  12 . The screw assembly  22  includes a threaded body  36  and a T-shaped contact plate  38  that is rotationally coupled to the threaded body  36  and free to rotate relative to the body  36 . Rotational coupling of the contact plate  38  is facilitated by press fitting or the like of an end portion  40  of a shank  46  coupled to the contact plate  38  within a bore  48  of the threaded body  36 . 
         [0023]    The contact plate  38  is spaced from the threaded body  36  in the assembled, unitary configuration of the screw assembly  22 . In particular, the space between the contact plate  38  and the threaded body  36  is defined by a distance between the contact plate  38  and a point of coupling between the end portion  40  of the shank  46  within the bore  48  of the threaded body  36 . This space, along with the coupling of the shank  46  within the bore  48  enable rotational movement of the contact plate  38  relative to the threaded body  36 , even when the screw assembly  22  is coupled to the body  12  of the connector  10 . A spacer  50 , which in this exemplary embodiment takes the form of a cup spring washer (i.e., a Belleville washer), is positioned between the threaded body  36  and the contact plate  38 . In this regard, the cup spring washer  50  includes an aperture  52  that is configured to receive the shank  46 . When the threaded body contact plate  38 , and the cup spring washer  50  are coupled to one another, the screw assembly  22  defines a unitary structure that is engageable with the body  12  of the connector  10 . As such, even though the screw assembly  22  includes a number of discrete components, those components, when assembled, are not intended to be disassembled. Therefore, the screw assembly  22  is usable in the field without the need for any disassembly or assembly. 
         [0024]    Coupling of the shank  46  within the bore  28  of the threaded body  36  also restricts movement of the contact plate  38  relative to the threaded body  36 , such that the contact plate  38  cannot be separated from the threaded body  36 . Moreover, this coupling permits movement of the contact plate  38  toward the threaded body  36 . With particular reference to  FIGS. 5-6 , the amount of movement permitted by this coupling is defined by a spacing between the cup spring washer  50  and a top surface  38   a  of contact plate  38 . The amount of movement is further defined by the particular type of coupling between the end portion  40  of shank  46  and a corresponding receiving structure  54  within the bore  48  of the threaded body  36 . 
         [0025]    Axial movement of the contact plate  38  relative to the threaded body  36  is limited by the cup spring washer  50 . More particularly, the cup spring washer  50  has a projecting surface  50   a  that faces the contact plate  38  and which is deflectable in a direction along an axis  48   a  of the bore  48  of the threaded body  36 . In this regard, a force exerted between the conductor  14  and a contact surface  38   b  of the contact plate  38  in a direction along the axis  48   a  deflects the cup spring washer  50  such that the projecting surface  50   a  is pushed toward the threaded body  36 . This deflection, in turn, permits movement of the contact plate  38  toward the threaded body  36 . Resiliency of the cup spring washer  50  exerts a reaction force against the contact plate  38  in a direction toward the conductor  14 , thereby securing contact between the contact plate  38  and the conductor  14 . Therefore, the cup spring washer  50  serves as a thrust washer between the plate  38  and screw body  36  for increased clamping force, torque retention and dynamic connection. 
         [0026]    Rotational movement of the contact plate  38  relative to the threaded body  36  is enabled by minimizing the amount of contact between the contact plate  38  and the cup spring washer  50 . More particularly, when the threaded body  36 , cup spring washer  50 , and contact plate  38  are coupled to one another, the contact plate  38  contacts the cup spring washer  50  only along a rim  60  defining aperture  52  of the cup spring washer  50 , rather than along the entire projecting surface  50   a.  This minimum amount of contact between the contact plate  38  and the cup spring washer  50  in turn minimizes the friction between the contact plate  38  and the projecting surface  50   a,  thereby facilitating rotational movement of the contact plate  38  relative to the cup spring washer  50 . No particular orientation of the contact plate  38  is required with the connector  10  of this invention. 
         [0027]    The contact surface  38   b  is suitably shaped to minimize damage to conductor  14  engaged by the contact plate  38 . More particularly, the contact surface  38   b  in some embodiments is in the form of a smooth or flat surface, thereby spreading the force exerted by the screw assembly  22  against the conductor  14  throughout the entire area of the contact surface  38 b. Alternative embodiments of the contact plate  38   c - 38   l  are shown in  FIGS. 8-17  each of which incorporate at least some of the features of the contact plate  38  shown in  FIGS. 1-7 . Those of ordinary skill will readily appreciate other contact plate designs within the scope of this invention in addition to those disclosed herein. 
         [0028]    The operation of the screw assembly  22  is best appreciated with respect to the structure depicted in  FIG. 7 . The screw assembly  22  is inserted into the body  12  of the connector  10  by engaging the exterior threads  34  of the threaded body  36  with the threaded wall  20  in the bore  18  of the connector body  12 . Moreover, lip  69  is disposed at a proximal end of the bore  18  to facilitate initial engagement of the threaded body  12  with the threaded wall  20 . In this regard, rotation of the threaded body  36  relative to the body  12  is facilitated by engagement of a tool (not shown) that engages a tool engaging portion at a proximal end of the threaded body  36 . In this exemplary embodiment, the tool engaging portion is in the form of a socket  70  configured to accept an Allen wrench. Persons of ordinary skill in the art however, will readily appreciate that other types of tool engaging portions may be substituted, such as portions configured to receive a different type of tool. 
         [0029]    Rotation of the screw assembly  22  relative to the body  12  may be continued up to a point where deflection of the cup spring washer  50  is detected. This deflection, as noted above, causes a reaction force to be exerted by the cup spring washer  50  against the contact plate  38 . This reaction force, in turn, causes a force to be exerted by the contact surface  38   b  of the contact plate  38  against the conductor  14  in the body  12  of the connector  10 . This force exerted against the conductor  14  thereby secures the connector  10  to the conductor  14 . Any subsequent expansion or contraction of the conductor  14  relative to the contact plate  38  does not result in decoupling of the screw assembly  22  relative to the body  12  of the connector  10 . More particularly, any such expansion or contraction respectively causes a further deflection of the cup spring washer  50  or a return thereof to its original shape. Accordingly, the position of the threaded body  36  relative to the body  12  of the connector  10  is fixed regardless of any relative expansion or contraction of the conductor  14 . Likewise, any vibration of a structure containing the connector  10  will result in the conductor  14  exerting a force against the contact plate  38  which, in turn, exerts a force against the cup spring washer  50  which will react accordingly by deflecting or returning to its original shape rather than decoupling the threaded body  36  from the body  12  of the connector  10 . 
         [0030]    From the above disclosure of the general principles of this invention and the preceding detailed description of at least one embodiment, those skilled in the art will readily comprehend the various modifications to which this invention is susceptible. Therefore, we desire to be limited only by the scope of the following claims and equivalents thereof.