Abstract:
An electrical distribution block has an electrically insulative and temperature resistant housing and a conductive rod having multiple electrical connection locations spaced along its length. The conductive rod is inserted into the housing, and the housing allows access to the electrical connection locations on the conductive rod. An electrical connection may be established by inserting a wire through the housing and into the electrical connection location. A fastener for maintaining the electrical connection is accessible through the housing to press the wire against the conductive rod.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     The present application claims priority from Provisional Application Ser. No. 60/146,911, filed Aug. 3, 1999, entitled ELECTRICAL DISTRIBUTION BLOCK. 
    
    
     BACKGROUND OF THE INVENTION 
     The present application relates to electrical distribution blocks, and, more particularly, to electrical power distribution blocks designed specifically for high temperature applications. Such thermal-resistant distribution blocks allow for maintaining an electrical connection under extreme thermal conditions. 
     In many instances, electrical distribution blocks are used with electrical elements having short electrical leads. The short wires forces the electrical distribution block to be mounted near to the electrical element, often exposing the electrical distribution block to the high temperature environment. In a situation where a sensor is used in a furnace, such exposure can be severe. 
     In addition, even if the materials are individually temperature resistant, fluctuations in temperature may effect the integrity of the electrical contacts over time. In particular, connections may weaken due to variations in thermal expansion rates between the various materials. 
     Further, high temperatures can increase electrical resistance within conductive materials, precipitating undesired power loss. Thus, the connection must be formed and maintained using temperature resistant materials, which have conductive properties that are similarly unaffected by high temperatures. 
     Finally, once the electrical distribution block is mounted in the high temperature environment, repair time and connection set up time should be minimized. Thus, it is desirable to have an electrical distribution block that allows for connections from more than one direction, so as to facilitate repair, upgrades, and maintenance over time. 
     BRIEF SUMMARY OF THE INVENTION 
     A temperature resistant, electrical distribution block has an electrically insulative housing and a conductive rod. The conductive rod defines multiple electrical connection locations spaced along its length. The conductive rod is inserted into the housing, and the housing allows access to the electrical connection locations through the housing. An electrical connection may be established by inserting a wire through the housing and into the electrical connection location. Fasteners are accessible through the housing for pressing each wire against the conductive rod and for maintaining the electrical connection between the wires and the conductive rod. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of the electrical distribution block. 
     FIG. 2 is a cross-sectional end view of the electrical distribution block of FIG.  1 . 
     FIG. 3 is a top plan view of the electrical distribution block of FIG.  1 . 
     FIG. 4 is a cross-sectional side view of the electrical distribution block of FIG.  1 . 
     FIG. 5 is a cross-sectional top view of the conductive rod housed in the electrical distribution block of FIG.  1 . 
     FIG. 6 is a cross-sectional end view of the conductive rod. 
     FIG. 7 is a cross-sectional side view of the conductive rod. 
    
    
     While the above-identified drawing figures set forth a preferred embodiment, other embodiments of the present invention are also contemplated, some of which are noted in the discussion. In all cases, this disclosure presents the illustrated embodiments of the present invention by way of representation and not limitation. Numerous other minor modifications and embodiments can be devised by those skilled in the art which fall within the scope and spirit of the principles of this invention. 
     DETAILED DESCRIPTION 
     FIGS. 1-7 illustrate an electrical distribution block  10  incorporating the present invention, including a housing  12 , a conductive rod  14  and fasteners  16 . FIGS. 1-4 illustrate the electrical distribution block  10  in the assembled position, and FIGS. 5-7 illustrate the conductive rod  14  removed from the electrical distribution block  10 . 
     The housing  12 , conductive rod  14 , and fasteners  16  maybe formed in any of a variety of ways known in the art, only one of which is described here for explanatory purposes. The electrical distribution block  10  is described for use in a cycled heat environment, but the present invention is equally applicable in stable temperature environments. 
     The electrical distributor block  10  is designed for use in a cycled heat environment, wherein the temperature fluctuates over a wide range quite rapidly. The housing  12  is formed of ceramic. In the preferred embodiment, the housing  12  is formed of ceramic, which rated as temperature resistant to 1000 degrees Celsius. The most preferred material for the housing  12  is porcelain of the type KER111 according to DIN 40680. The housing  12  is substantially rectangular, generally having a top  18 , a bottom  20 , two sides  22 , and two ends  24 . In the preferred embodiment, the housing  12  is approximately 63.5 millimeters long, 38 millimeters wide, and 25.4 millimeters high. 
     As shown in FIG. 1, the top  18 , the sides  22  and the ends  24  of the housing  12  have openings  46 , 48 , 36 . Though the opposing side  22  and end  24  may not be seen in this view, the preferred embodiment is symmetrical both in length and width, and the description of the side  22  and end  24  which follows is equally applicable to both sides  22  and ends  24 , respectively. 
     In the preferred embodiment, the housing  12  has four trapezoidal cutouts  28  on the top  18  and bottom  20 . The cutouts  28  serve several purposes. First, the cutouts  28  provide a gripping surface during assembly. Second, the cutouts  28  increase the amount of surface area exposed to the environment, and reduce the volume of the housing  12 . The cutouts  28  are sized to maintain a relatively uniform distribution of ceramic across the housing  12 . 
     In a cycled heat environment, the cutouts  28  provide relief points for tension and compression stresses, and assist in relatively uniform heating and cooling of the housing  12 . In addition, by assisting in relatively uniform distribution of ceramic material and providing relief points for compression and tension stresses, the cutouts  28  prevent cracking of the housing  12  over time and contribute to the overall durability of the housing  12 . In the preferred embodiment as shown, the cutouts  28  extend vertically into the housing  12  approximately 8 millimeters, longitudinally into the housing  12  approximately 8.6 millimeters, and horizontally approximately 9 millimeters at the cutout bottom  32  and 11 millimeters at the cutout top  34 . 
     In addition, the top  18  of the housing  12  defines circular cutouts  30 . The circular cutouts  30 , like the trapezoidal cutouts  28 , provide relief for tension and compression forces during cycled heating and cooling. In addition, the circular cutouts  30  may also be drilled to provide through holes for fixedly attaching the housing  12  to a structure (not shown). The circular cutouts  30  are aligned longitudinally along the top  18  the housing  12  and are spaced evenly to maintain a relatively uniform volume of ceramic throughout the length the housing  12 . In the preferred embodiment, there are three circular cutouts  30 , spaced approximately 15.85 millimeters center to center and from the edges  24  to the center of the first circular cutout  30 . In the preferred embodiment, each circular cutout  30  is centered horizontally and has a diameter of approximately 7.5 millimeters. 
     FIG. 2 illustrates the end  24  of the housing  12 . On each end  24  of the housing, two longitudinal bore holes  36  extend the entire length of the housing  12 . The longitudinal bore holes  36  are sized to fit a metal conductive rod  14  (shown in FIGS.  5 - 7 ), two of which maybe inserted into the longitudinal bore holes  36 . In the preferred embodiment, the longitudinal bore holes  36  are approximately 6.5 millimeters in diameter, and the conductive rod  14  is slightly smaller to allow for different rates of thermal expansion and contraction. In addition, in the preferred embodiment, the longitudinal bore holes  36  are positioned slightly closer to the top  18  than to the bottom  20  (approximately 10.65 millimeters from the top  18  to the longitudinal axis  38  of the longitudinal bore hole  36 ). Positioning the longitudinal bore holes  36  closer to the top  18  allows the ceramic housing  12  to insulate the conductive rod  14  from the support structure (not shown). In cycled heat environments, the support structure maybe formed of any number of different materials. Since the thermal properties of the support structure cannot be determined in advance, the longitudinal bore holes  36  are offset away from the bottom  20  and the support structure (not shown) in order to insulate the conductive rod  12 . 
     As shown in FIG. 2, the cutouts  28  cause the end  24  of the housing  12  to be substantially H-shaped. As previously described, the ends  24  have two longitudinal bore holes  36 , one on each side  22 , and two cutouts  28  on the center of the top  18  and bottom  20 . The two longitudinal bore holes  36  are sized to receive the conductive rod  14 . By providing an insertable rod  14 , the electrical distribution block  10  permits the conductive rod  14  to be replaced after installation of the housing  12 . The two longitudinal bore holes  36  are positioned slightly above the mid point vertically on the end  24  of the housing  12 . 
     As shown in FIG. 3, the top  18  can be divided into three sections: a left distributor section  40  (shown in FIG. 3 at top), a right distributor section  42  (shown in FIG. 3 at bottom), and a center section  44 . The center section  44  contains the circular cutouts  30  as previously discussed. The left and right distributor sections  40 , 42  are substantially the same, except that they are positioned on opposite sides of the housing  12 . The description of the right distributor section  42  which follows can be applied equally to the left distributor section  40  as they are substantially the same. 
     The right distributor section  42  defines several vertical holes  46  across the top of the housing  12 . The vertical holes  46  are aligned longitudinally along the length of the housing  12 , and centered over the longitudinal bore hole  36  corresponding to the right distributor section  42 . The vertical holes  46  extend from the top  18  into the longitudinal hole  32 . In the preferred embodiment, the vertical holes  46  are approximately 5.6 millimeters in diameter, approximately 1.0 millimeters smaller than the longitudinal bore hole  36 . The vertical holes  46  are spaced evenly along the top  18 . In the preferred embodiment, the vertical holes  46  are spaced 9 millimeters center to center, and approximately 4.8 millimeters from either end  24  to the center of the first vertical hole  46 . The vertical holes  46  are spaced to allow for substantially uniform distribution of ceramic throughout the housing  12 . In addition, the vertical holes  46  provide relief from tension and compression stresses. When a screw is inserted into the vertical hole  46 , the housing  12  thermally insulates the screw from the surrounding environment, preventing the screw or wire from cooling or heating too quickly relative to the surrounding housing  12 . Finally, the housing  12  prevents human contact with the screw, reducing the likelihood of accidental electrical shocks. 
     While the vertical holes  46  could extend completely through the housing to allow for mounting of a screw through the hole  46  from either the top  18  or the bottom  20  of the housing  12 , in the preferred embodiment the housing  12  is designed to be mounted to an underlying support structure (not shown). Since the bottom  20  is designed to be mounted to a support structure, the bottom  20  does not have holes  46  sized to receive a screw because it would be difficult to access such holes after the housing  12  was mounted. 
     As shown in FIG. 1, the sides  22  of the ceramic housing  12  define horizontal holes  48  which extend into the housing  12 . The horizontal holes  48  are aligned with the vertical holes  46  along the right distributor section  42  of the housing  12 . The housing  12  defines two fewer horizontal holes  48  along the side  14  than vertical holes  46  across the top  18 . 
     As shown in FIG. 4, the vertical hole  46  on either end  24  of the right distributor section  42  corresponds with an end hole  50  on the conduct rod  14 . The end hole  50  is discussed further with regard to FIGS. 5-7. As can be seen, in the preferred embodiment, the end hole  50  is positioned slightly below the central axis  52  of the conductive rod  14 , when viewed in cross-section from the side  22 . 
     The conductive rod  14  can accept a wire through the end hole  50 , allowing an additional electrical attachment on each end  24 . The end hole  50  also permits one electrical distribution block  10  to be connected to an adjacent electrical distribution block (not shown), to allow the electrical distribution blocks to be connected in series. 
     The horizontal holes  48  extend into the housing  12  to meet the longitudinal bore hole  36 . The horizontal holes  48  are aligned longitudinally along the side  14 , and are positioned vertically so as to be centered over the longitudinal bore hole  36 . The horizontal hole  48  has a slightly smaller diameter than the longitudinal bore hole  36 . In the preferred embodiment, the horizontal holes  48  are approximately 5.6 millimeters in diameter. Like the vertical holes  46 , the horizontal holes  48  serve a dual purpose of insulating the wire from the surrounding environment and from human contact. In addition, the horizontal holes  48  provide access to the longitudinal bore hole  36 , allowing access to the conductive rod  16  when it is inserted into the longitudinal bore hole  36 . 
     The vertical and horizontal holes  46 , 48 , 50  are aligned vertically in pairs, such that each vertical hole  46  has a corresponding horizontal hole  48  or end hole  50 . The vertical and horizontal or end holes  46 , 48 , 50  are paired such that a wire may be inserted into one hole  46 , 48  and a screw may be tightened into the corresponding hole  50  to establish an electrical contact with the conductive rod  14 . Alternatively, if desired, screws may be positioned horizontally through holes  48 , 50  and wires inserted vertically though holes  46 . Thus, it does not matter whether the wire or the screw is inserted into the vertical hole  46 , the other should be inserted into the corresponding horizontal or end hole  48 , 50 . In the preferred embodiment, the vertical holes  46  and the horizontal and end holes  48 , 50  are position to allow access to the electrical attachments through the sides  22 , the ends  24 , and the top  18 . 
     In an alternative embodiment, the housing  12  may define a access slots (not shown), formed by interconnecting the horizontal holes  48  and interconnecting the vertical holes  46 . The access slots could allow access to the conductive rod  14 . In addition, the conductive rod  14  similarly could define connection slots (not shown) allowing insertion of a wire and insertion of a screw to fix the wire into place. 
     The conductive rod  14  is insertable into the housing  12  through the end  24  of the housing  12 . As shown in FIGS. 5-7, end holes  50  extend longitudinally into the conductive rod  14 . Wire holes  54  also extend horizontally into the rod  14 . Screw holes  56  also extend into the conductive rod  14  from other directions, such as vertically, each wire hole  54  paired with one screw hole  56  to allow the screw (shown in FIGS. 2-4) to tighten down onto a wire (not shown). In the present invention, the wire hole  54  and the screw hole  56  extend into the conductive rod  14  and connect at an angle less than 180 degrees. In the preferred embodiment, the wire holes  54  extend the fill width of the diameter of the conductive rod  14 . The screw holes  56  extend slightly more than half-way through the conductive rod  14 , intersecting the wire holes  54  at a 90 degree angle. 
     The 90 degree attachment angle allows the screw (shown in FIGS. 2-4) to tighten down against the wire, pressing the wire against the far side  58  of the wire hole  54 . A connection at an angle greater than 90 degrees may result in gradual loosening of the electrical connection, particularly in the cycled heat environment. 
     The vertical holes  46  are aligned so as to be centered over the central axis  52  of the conductive rod  14 , and over the screw holes  56  in the conductive rod  14 . In the preferred embodiment, the vertical holes  46  are not threaded, but the screw holes  56  are, allowing the screw  62  to be inserted into the vertical hole  46  and tightened down into the screw hole  56 . 
     The horizontal holes  48  are similarly aligned so as to be centered over the central axis  52  of the metal rod  14  and over the wire holes  54 . However, in the preferred embodiment, neither the wire holes  54  nor the horizontal holes  48  are threaded. In an alternative embodiment, both the wire holes  54  and the screw holes  56  can be threaded, leaving the choice as to whether as to use the vertical holes  46  for the wires or the screws  62  for the time of installation. 
     While the housing  12  can be produced with holes  46 , 48  that are threaded, in the preferred embodiment, the holes  46 , 48  are not threaded. Instead, the holes  46 , 48  provide access to the conductive rod  14 , and the holes  54 , 56  on the conductive rod  14  are threaded. Thus, the screw  62  can be inserted through the hole  46  in the housing  12  and tightened into the screw hole  56 . 
     The distribution block  10  is designed to be used in high temperature, cycled heat environments, meaning the temperatures fluctuates. The cutouts  28 , 30 , 32  are positioned to maintain a nearly uniform material distribution across the housing  12 . Because of the cycle heating and cooling, if the housing  12  had more material on one end or on the other or at various points along the housing  12 , those areas might retain heat or not heat as quickly as other areas placing. These areas could become weak points in the housing  12 , causing the housing  12  to crack and fracture. The cutouts both circular  30  and square  28 , 32 , permit the housing  12  to heat and cool in uniform fashion to prevent cracking. 
     FIG. 3 shows a top view of the block  10 . Both the sides  22  and the top  18  can have any number of holes  48 , 46  as the particular application requires; however, the number of holes  48  on the side  22  should be two less than the number of holes  46  across the top  18  to permit insertion of the wire into the end hole  50  of the inserted rod  14 . 
     As shown in FIG. 4, the horizontal holes  48  are positioned slightly above the vertical midpoint of the side  22  of the housing  12 . The cutout  32  along the bottom  20  of the housing  12  divides the housing  12  in two. In the embodiment shown, cutout  32  provides stress relief along the bottom  20  of the housing  12 . In addition, in the preferred embodiment, the housing  12  has legs  60 , which allow air to flow between the housing  12  and the mounting structure (not shown). This air gap allows for convection heating and cooling of the housing  12 , largely independent of thermal conduction from the underlying mounting structure. 
     As the distribution block  10  is intended to be used in a cycled heat environment, it is imperative to maintain a relatively uniform thickness throughout the block  10 . The combination of the cutouts  28 , 30 , 32  and the bore holes  46 , 48  cooperate to maintain a relatively uniform thickness throughout the housing  12 . As the housing  12  is heated, the housing expands slightly and the cutouts  28 , 30 , 32  and bore holes  46 , 48  provide relief for the thermal expansion. Since the cutouts  28 , 30 , 32  and bore holes  46 , 48  assist in maintaining a relatively uniform thickness across the housing  12 , the housing  12  also cools relatively uniformly. 
     In the preferred embodiment, the conductive rod  14  is approximately 5.5 millimeters in diameter, and 58 millimeters long, formed of NICLAFOR 1000-TD4 (CuNi9Sn6), which is rated as temperature resistant to 300 degrees Celsius. The screws or fasteners  62  are formed of steel with DACROMET, chromium based alloy plating, which is rated as temperature resistant to 350 degrees Celsius. 
     As FIG. 4 illustrates, the screws  62  can be tightened down into the conductive rod  14 , where the head  64  of the screw  62  is surrounded completely by the ceramic housing  12 . Since metal typically expands and contracts more rapidly than ceramic, a screw  62  can easily become loose over time in the cycled heat environment. However, the deep inset of the screw  62  in the present invention offsets the thermal differences between the ceramic housing  12  and the metal screw  62 , maintaining a heated envelop for the screw  62  during the cycling process. In other words, as the ceramic housing  12  cools, the inset of the screw  62  maintains a heat or temperature proximately equal that of the surrounding housing  12 , essentially keeping the screw  62  warm until the housing  12  cools, and preventing the screw  62  from thermally contracting before the housing  12  thermally contracts. In addition, the housing  12  insulates the screw  62  and the conductive rod  14  from human contact. 
     The offset alignment of the end holes  50  permit the fastening screw  62  to tighten down against the inserted wire. By offsetting the hole  50  away from the central axis  52  of the metal rod  14 , the hole  50  is positioned closer to the ceramic housing  12  and away from the screw  62 . The ceramic housing  12  maintains the temperature of the metal rod  14 . This is particularly important at the ends  24  of the housing  12 , where the wire or screw  62  can be inserted into the end hole  50  because the end hole  50  is not surrounded by the housing  12 . Instead, the end hole  50  is exposed to the environment, allowing for more rapid changes in temperature, depending on the environmental conditions. The offset of the end hole  50  from the central axis  52  controls for the potential temperature changes by using the housing  12  as a insulator. In a preferred embodiment, the end hole  50  is offset away from the central axis  52  toward the underlying mounting structure approximately 0.5 millimeters. In a more preferred embodiment, the end hole  50  is offset away from the central axis  52  approximately a distance greater than 5 percent of the diameter of the conductive rod  14 . In the most preferred embodiment, the end hole  50  is offset away from the central axis  52  a distance approximately equal to 9 percent of the diameter of the conductive rod  14 . 
     In the preferred embodiment, the metal rod  14  is offset upward in the housing away from the underlying mounting structure. The legs  60  and offset of the longitudinal bore holes  36  help to insulate thermally the conductive rod  14  from the underlying mounting structure. As it is unknown at the time of production what type of structure the housing  12  will be mounted to, the electrical connections should be protected from overly rapid cycling of heating and cooling through thermal conduction from the underlying mounting structure. As previously indicated, the metal components are more affected by the cycled heating and cooling than the ceramic housing  12 . The offset allows the housing  12  to provide an insulative or buffer layer between the underlying mounting surface and the metallic rod  14 . 
     In the present invention, the distribution block  10 , by virtue of the combination of materials used and structural design, is temperature resistant up to 300° Celsius. In addition, the inset of the screws  62  and the positioning of the cutouts  28 , 30 , 32  permit the use of the distributor block  10  in the cycled heat environment for an extended period of time without deterioration of the electrical connections or cracking of the housing  12 . 
     The positioning of the screw holes  62  and the alignment of the holes  46 , 48 , 50  relative to each other permit the mounting of the housing  12  and subsequent attachment of the wires to the distribution block  10 . As such a block  10  will likely be used within another structure, flexibility as to the mounting of the wires and direction of the screws  62  is desirable to permit easy installation of the distributor block  10 . 
     While the present invention has been described with regard to cutouts  28 , 30 , 32 , the circular cutouts  30  may serve an additional purpose, allowing for fixable mounting of the housing  12  to another structure. Holes (not shown) could be drilled or formed in the locations of the circular cutouts  30 , passing entirely through the housing  12 , to allow for the housing  12  to be mounted. 
     In an alternative embodiment, the openings on the housing  12  may be interconnected. In addition, the openings on the conductive rod  14  may be connected or continuous along the length of the rod  14 . 
     Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.