Abstract:
A terminal block assembly include a base assembly includes a terminal block housing and a terminal stud extending therethrough, a filter assembly coupled to the stud; and a ground assembly coupled to the base assembly and the filter assembly for dissipating filtered signals. The filter assembly is mechanically isolated from the base assembly and the ground assembly to prevent structural loading of the filter assembly.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to terminal block assemblies for electrical power distribution, and, more particularly, to filtered terminal block assemblies for removing undesirable frequencies from electronic signals. 
     A growing proliferation of electronic devices in modern products and systems can produce unintended and undesirable signal distortion between electrical components, systems and subsystems. While some signal distortion is tolerable in many instances, in certain applications signal distortion is a significant issue that must be controlled, if not overcome. Such applications wherein reduction and/or elimination of signal distortion is desirable include, for example, power supply systems for telecommunication systems, telecommunication switching applications, cellular base stations, radar transmission systems, industrial control systems, and instrumentation systems. 
     Consequently, a variety of terminal block assemblies have been introduced that include one or more filter elements coupled to electrical terminal elements for removing undesirable frequency transmission through the terminal block. One type of filtered terminal block assembly includes a tubular capacitor element mounted to a terminal stud for filtering a signal through the stud. When electrical connections are made to the terminal stud in the field, however, the tubular capacitor element may be placed under a structural load. Connections to threaded studs render this type of terminal block assembly particularly vulnerable to placing the capacitor element under stress when a wire is fastened to the stud. The resultant stress may damage the capacitor element and adversely affect filtering performance of the terminal block assembly. 
     BRIEF SUMMARY OF THE INVENTION 
     In an exemplary embodiment of the invention, a terminal block assembly includes a base assembly including a terminal block housing and a terminal stud extending therethrough, a filter assembly coupled to the stud, and a ground assembly coupled to the base assembly and the filter assembly for dissipating filtered signal frequencies from signals transmitted through the terminal block. The filter assembly is mechanically isolated from the base assembly and the ground assembly to prevent structural loading of the filter assembly. 
     More specifically, the filter assembly includes a resilient contact member for mechanically isolating the filter assembly from the base assembly and the ground assembly. The terminal stud includes opposite ends configured for electrical connections thereto, and an undercut located between the opposite ends for retaining the resilient contact element. The filter assembly further includes a tubular capacitor element and the resilient contact member establishes an electrical connection with an inner surface of the tubular capacitor element. 
     Mechanical isolation of the filter element from structural load and associated stress and strain provides an operating environment of the filter element free from negative effects of structural load. Filter performance and reliability of the terminal block assembly is therefore increased in a cost effective manner. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded view of a terminal block assembly; 
     FIG. 2 is a side elevational view of the terminal block assembly shown in FIG. 1 in an assembled condition; and 
     FIG. 3 is a cross sectional view of the terminal block assembly along line  3 — 3  of FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 is an exploded view of a terminal block assembly  10  for transmitting electrical signals from, for example, a power supply source, system or subsystem (not shown) to a power receiving component, system or subsystem (not shown) while filtering undesirable frequencies, electromagnetic interference and noise from the transmitted signal. While terminal block assembly  10  is particularly advantageous for use in connection with high current power supply systems for telecommunication systems, it is contemplated that the advantages of terminal block assembly also accrue to many other applications wherein signal distortion is problematic, including but not limited to telecommunication switching applications, cellular base stations, radar transmission systems, industrial control systems, and instrumentation systems. Therefore, the invention is not intended to be limited to any particular application, and the foregoing end-use applications are set forth for illustrative purposes only. 
     Terminal block assembly  10  includes a base assembly  12 , a filter assembly  14  and a ground assembly  16 . Base assembly  10  includes a non-conductive terminal block housing  18  and two electrically conductive terminal studs  20  extending therefrom on opposite sides  22 ,  24  of housing  18 . In an exemplary embodiment, terminal block housing  18  is fabricated from a known plastic or thermoplastic material, and studs  20  are insert molded therein. In alternative embodiments, other dielectric materials are employed to fabricate terminal block housing  18 , and studs  20  may be coupled to terminal block housing  18  according to other methods and techniques known to those in the art, such as, for example, a two-piece housing assembly fastened over terminal studs  20 . 
     One side  22  of terminal block housing  18  includes an opening or bore  26  for each stud  20  that receives respective portions of filter assembly  14 , further explained herein below. Terminal block housing side  22  further includes a plurality of mounting apertures  28  for receiving fasteners of ground assembly  16 , also further explained herein below. Terminal block housing side  24  includes first and second outer walls  30  extending in substantially parallel fashion from side  24  and approximately equally spaced from a longitudinal axis of terminal studs  20 . 
     Terminal studs  20  are each configured for connection to a load side or line side device (not shown) with opposite threaded ends. While the illustrated embodiment includes two studs  20  extending through opposite sides  22 ,  24  of terminal block housing  18 , it is understood that with appropriate modification of terminal block housing  18  to accommodate the respective terminal studs  20 , greater numbers of terminal studs  20  may be employed within the scope of the present invention to provide a multiple pole filtered terminal block assembly for a desired end-use application. 
     Filter assembly  14  includes an electrically conductive resilient contact element  32  and a filter element  34  for each terminal stud  20 . Resilient contact elements  32  include opposite ends  35  and a plurality of resilient members  36  extending therebetween. Each end  35  forms an incomplete annulus for insertion over terminal studs  20 , and resilient members  36  are slightly outwardly bowed between spring element ends  35  so that resilient contact element  32  flexes with spring-like action to absorb structural loads placed upon filter assembly  14 . 
     In one embodiment, each filter element  34  includes a generally tubular body having an inner surface  36  and an outer surface  38  situated about a central bore through the body. Each of body inner and outer surfaces  36 ,  38  include separate circuits plated thereon. Capacitive material (not shown) is located between the respective circuits of body inner and outer surfaces  36 ,  38 . When filter elements  34  are placed over terminal studs  20 , body inner surfaces  36  are electrically associated with an outer surface of terminal studs  20 . A magnetic field generated between surfaces  36 ,  38  through the capacitive material filters signals of a predetermined frequency from a signal transmitted through terminal studs  20 . The filtering capacity of each filter element  34  is dependent upon specific characteristics of filter element  34 , and a variety of ratings of filter elements  34  are commercially available from different manufacturers. Thus, a range of frequencies filtered from terminal block assembly  10  may be varied from application for different applications with proper selection of filter elements  34 . 
     In a further embodiment, more than two filter elements  34  may be employed with respective terminal studs  20 , and ratings of filter elements  34  may be the same or different from one another to provide a variety of signal filtering options. In alternative embodiments, other known filter elements  34  may be used in lieu of the above-described and illustrated tubular capacitor filter elements. 
     Ground assembly  16  includes a ground plate  40  and a plurality of fasteners  42  for coupling ground plate  40  to terminal block housing apertures  28  through complementary openings  44  extending through ground plate  40 . While in the illustrated embodiment, fasteners  42  are threaded fasteners or screws, it is appreciated that other fasteners and fastening mechanisms known in the art may be employed in alternative embodiments to couple ground plate  40  to terminal block housing  18 . 
     Ground plate  40  further includes a filter element opening  46  for each of filter elements  34  of filter assembly  14 . Solder preform  48  is applied about a circumference of filter element openings  46  for bonding and electrically connecting filter element outer surfaces  38  to ground plate  40 . Opposite standoffs  50  extend upwardly from either end of ground plate  40  through apertures  52  in ground plate  40 . Ground plate  40  provides a parallel path in the electrical circuit through terminal block assembly  10  to dissipate filtered signal portions from filter elements  34 . 
     While in the illustrated embodiment ground plate  40  includes two openings  46  for each filter element  34  of filter assembly  14 , greater numbers of terminal openings  46  may be employed within the scope of the present invention to accommodate additional filter assemblies  14  in a multiple pole filtered terminal block assembly. Thus, ground plate  40  may be adapted for a desired end-use application with appropriate modification of terminal block housing  18  to accommodate additional terminal studs  20  and filter elements  34 . Still further, additional standoffs  50  may be employed in alternative embodiments, and greater or fewer than the four illustrated fastener openings  44  may be employed to accommodate greater or fewer numbers of fasteners  42 . It is also recognized that other shapes of ground plate  40  may be used in alternative embodiments in lieu of the substantially rectangular ground plate  40  illustrated in FIG.  1 . 
     Terminal block assembly  10  is assembled by inserting resilient contact elements  32  over respective terminal studs  20  so that resilient contact elements  32  are positioned in terminal block bores  26  in terminal block housing first side  22 . Filter elements  34  are also placed over respective terminal studs  20  and positioned in respective terminal block bores  26  in terminal block housing first side  22 . One end  35  of each resilient contact element establishes electrical connection with each filter element inner surface  36 . Ground plate  40  is inserted over filter elements  34  and fastened to terminal block housing  18  with fasteners  42 . Solder preform  48  is applied to the circumferences of filter element openings  46  in ground plate  40  and solder preform is heated reflowed to bond solder preform  48  to ground plate  40  and filter element outer surface  38 , and also to form an electrical connection between ground plate  40  and filter element outer surface  38  for dissipation of filtered signals from filter elements  34 . Standoffs  50  are coupled to ground plate  40  to complete assembly of terminal block assembly  10 . 
     Resilient contact elements  32  mechanically isolate filter elements  34  from mechanical loads and associated mechanical stress that may occur, for example, when wires (not shown) are connected to terminal studs  20  above ground plate  40 . Resilient contact elements  32  absorb structural loads that would otherwise be placed on filter elements  34 . Negative impacts on filter performance due to structural stress and strain on filter elements  32  are therefore avoided. 
     FIG. 2 is a side elevational view of assembled terminal block assembly  10  illustrating filter assembly  14  partially within and partially extending from terminal block housing bore  26  (shown in FIG. 1) and grounding assembly  16  attached to terminal block housing  18 . Ends  60  of terminal studs  20  are threaded and therefore configured for coupling to respective connection wires (not shown) with, for example, a known connection member (not shown), such as a nut. Thus, when an electrical circuit is completed through terminal studs  20 , predetermined frequency ranges of signals passing therethrough are filtered out by filter assembly  14 . Thus, for example, a clean power supply signal, i.e., free of undesirable noise, may be supplied to, for example, telecommunications system equipment. 
     FIG. 3 is a cross sectional view of terminal block assembly illustrating threaded ends  60  of terminal studs  20  extending through terminal block housing  18 . Outer walls  30  extend from terminal block housing side  24 . 
     Each terminal stud  20  includes an undercut  70 , or step diameter decrease that acts as a stop for resilient contact member  32  (shown in FIG. 1) and retains resilient contact member  32  between capacitor element  34  and stud undercuts  70 . As such, resilient contact member  32  isolates filter element  34  from a structural load when terminal block assembly  10  is installed in the end-use application. Undercuts  70  are located intermediate threaded ends  60  of terminal studs  20  and within terminal block housing  18  adjacent housing bores  26  (shown in FIG.  1 ). Solder preform  48  is applied and reflowed about filter elements  34  to form an electrical connection between capacitor element outer surface  38  and ground plate  40  for dissipation of filtered signals. 
     While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.