BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an exploded perspective view of components of a prior art watt-hour meter socket jaw assembly.
FIG. 2 is an exploded perspective view of components of a prior art meter jaw mounting assembly.
FIG. 3 is an exploded perspective view at a reduced scale of a prior art power meter socket enclosure.
FIG. 4 is an exploded perspective view of a slide-in embodiment of a meter socket jaw assembly according to the present invention.
FIG. 5 is a perspective view of an assembled mold-in embodiment of a meter socket jaw assembly according to the present invention.
FIGS. 6
a-6f are perspective views of a plurality of alternative embodiments of jaws for watt-hour meters and bus bars according to the present invention.
FIG. 7 is an enlarged side elevational view of a prior art watt-hour meter socket jaw member and diagrammatically illustrates an effective electrical/thermal path of the jaw member.
FIG. 8 is an enlarged side elevational view of the mold-in embodiment of the meter socket jaw member of the present invention and diagrammatically illustrates an effective electrical/thermal path of the mold-in jaw member.
FIGS. 9
a and 9b illustrate respectively an exploded perspective view of one side of a meter socket assembly and a perspective view of the assembled meter socket components, both incorporating the slide-in embodiment of the meter socket jaw of the present invention.
FIG. 10 is a cross-sectional view of the slide-in meter socket jaw within an insulative meter socket jaw mounting block, taken on line 10-10 of FIG. 9b.
FIG. 11 is an enlarged perspective view of a meter socket half incorporating the mold-in embodiment of the meter socket jaw of the present invention.
FIG. 12 is a cross sectional view of the mold-in meter socket jaw molded within an insulative meter socket jaw mounting block, taken on line 12-12 of FIG. 11.
FIG. 13 is a flow diagram illustrating principal steps in forming meter jaws of the present invention by extrusion.
FIG. 14 is a flow diagram illustrating principal steps in forming a mold-in meter socket assembly of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure.
Referring drawings in more detail, the reference numeral 1 generally designates an improved watt-hour meter jaw assembly according to the present invention. Sets of the jaw assemblies 1 are used to receive corresponding sets of connector blades (not shown) of electrical power industry standard configurations of watt-hour meters. The meter jaw assemblies 1 may include one of two principal embodiments of meter jaw members 2, including a slide-in meter jaw member 3 (FIG. 4) or a mold-in meter jaw member 4 (FIG. 5). The meter jaw members 3 and 4 are secured to corresponding insulative meter jaw mounting blocks 6 (FIG. 9) or 7 (FIG. 11) for mounting within a meter socket enclosure 228 (FIG. 3).
The slide-in and mold-in meter jaw members 3 and 4 have a number of elements in common and will be described generally with reference to FIG. 8. Each meter jaw member 2 includes a base tab 10 with a pair of resilient meter jaw contacts 12 extending therefrom. The illustrated meter jaw contacts 12 are roughly back-to-back S-shaped elements and are generally mirror images of one another. Outer curved regions 14 of the contacts 12 curve toward one another to define a watt-hour meter blade receiving space 16 therebetween. Outer ends 18 of the contacts 12 flare from the curved regions 14 to form a guide for a meter blades into the blade receiving space 16. It should be noted that the jaw contacts 12 taper in thickness from root ends 20 at the base tab 10 toward the outer ends 18. The contour of the taper of the jaw contacts 12 is a factor in determining the resilience or spring constant of the jaw contacts 12.
Various embodiments of the meter jaw members 2 generally function to connect a first conductor, such as a meter blade or a bus bar (not shown), to a second conductor, such as a service power cable, a bus bar, or the like. The illustrated meter jaw members 3 and 4 each include an electrical power cable connector or wire receiver 26 to provide for connection of an electrical supply cable from an electrical utility or a service cable, such as for a home or commercial building, to conductor blades of a watt-hour meter. The illustrated cable connector 26 is U-shaped and includes a pair of spaced apart, generally parallel legs 28 and 29 connected by a curved bight section 30. An inner leg 29 extends from the base tab 10. The illustrated legs 28 and 29 include slide nut grooves or slots 32 formed into their inner surfaces to receive a slide nut 34. The slide nut 34 has a threaded aperture 36 (FIG. 4) to receive a threaded slide screw 38, which is illustrated as an Allen type screw. The slide nut 34 and slide screw 38 cooperate with the power cable connector 26 to clamp a stripped end of a power cable (not shown) against the bight section 30 of the connector 26. The power cable connector 26, slide nut 34, and slide screw 38 are similar in configuration and function to corresponding elements of the wire connector 202 shown in FIG. 1.
The jaw contacts 12 are configured to exert a selected compressive force on a watt-hour meter blade or stab to optimize electrical and thermal contact therewith. The force exerted is determined by the constituent material and the geometric dimensions. These factors also determine the electrical conductivity between areas of contact of the jaw contacts 12 with the meter blade and the area of contact between the wire receiver 26 and a power cable. Although not shown, the jaw members 2 may have a jumper blade extending from an outer end of the outer leg 28 of the wire receiver 26 to receive a jumper to interconnect jaw members 2 of a mounting block when the meter is to be removed.
The meter jaw members 2 may include a mounting element or key 44 for securing it to a fixed support. The slide-in meter jaw member 3 includes a slide-in mounting key 46 while the mold-in meter jaw member 4 includes a mold-in mounting key 48. The illustrated slide-in mounting key 46 includes a key web 50 (FIG. 10) extending from the base tab 10 and terminating in a key flange 52 extending from opposite sides thereof. Similarly, the mold-in mounting key 48 includes a key web 56 (FIG. 8) extending from the base tab 10 and having a plurality of key flanges 58 extending from opposite sides thereof to provide opposite grip surfaces 60 of the mold-in key 48 with a serrated or “corduroy” effect. The grip surfaces 60 of the mold-in key 48 could, alternatively, be provided with outer surface configurations or finishes for enhanced gripping, such as a pebble grain, bumps, knurling, swaging, or the like.
FIGS. 6
a-6f illustrate alternative embodiments of the meter jaw members 2 and bus bar connectors 66 (FIGS. 6d and 6e) which are considered to be encompassed by the present invention. FIG. 6a shows a meter jaw member 70 with an integral bus bar or tab 72 extending from a base tab 10, which also has resilient meter jaw contacts 12 extending therefrom The bar 72 may be punched or drilled and joined to other bus bars using fasteners. The jaw member 70 also has a slide-in mounting key 74 extending from the base tab 10. A meter jaw member 78 in FIG. 6b includes a pair of resilient meter jaw contacts 12 extending from a base tab 10 along with a pair of resilient bus bar jaw contacts 80 extending from the base tab 10 at a substantially right angle to the meter jaw contacts 12. The bus bar jaw contacts 80 are substantially similar to the meter jaw contacts 12 except that a bus bar receiving space 82 therebetween is wider than the blade receiving space 16 of the jaw contacts 12 of the jaw members 2. The jaw contacts 80 enable the jaw member 78 to be connected to a bus bar without the use of fasteners. The illustrated jaw member 78 includes a slide-in mounting key 74 extending from the base tab 10.
FIG. 6
c shows an in-line meter jaw member 86 including a pair of resilient meter jaw contacts 12 extending from one side of a base tab 10 and a pair of bus bar jaw contacts 80 extending from an opposite side of the base tab 10. FIG. 6d shows an in-line bus bar connector 88 having pairs of resilient bus bar jaw contacts 80 extending from opposite sides of a base tab 10. FIG. 6e illustrates a right angle bus bar connector 90 including a pair of resilient bus bar jaw contacts 80 extending from one side of a base tab 10 and a second pair of bus bar jaw contacts 80 extending from an end of the base tab 10, at a right angle to the first set of contacts 80. The bus bar connectors 88 and 90 allow in-line and perpendicularly positioned bus bars to be interconnected without the use of fasteners. Finally, FIG. 6f illustrates an offset meter jaw member 92 including a pair of meter jaw contacts 12 extending from one side of an extended base tab 94 and a pair of bus bar jaw contacts 80 extending from an opposite side of the base tab 94 in laterally spaced relation to the meter jaw contacts 12. The variations in the illustrated jaw members 3, 4, 70, 82, 86, and 92 and in the illustrated bus bar connectors 88 and 90 are not meant to be exhaustive, but as exemplary of the great flexibility of connectors embodying the present invention.
The meter jaw members 2 and bus bar jaw members 66 are preferably of a one-piece construction and are formed of a metal or metal allow having a high level of electrical and thermal conductivity. Because of similarities between the meter jaw members 2 and the bus bar jaw members 66, manufacturing details will be addressed particularly to the meter jaw members 2, but should be understood to also apply in most cases to the bus bar jaw members 66. Materials for the meter jaw members 2 should be strong and durable and have a selected degree of elasticity or resilience, particularly in the jaw contacts 12. Additionally, the material selected should be economical in bulk and economical to fabricate. Suitable materials for the meter jaw members 2 include aluminum alloys known by the standard designations of 6101, 6061 or 6063 alloys.
The meter jaw members 2 may be formed by any suitable manufacturing process which is appropriate for the selected material and the desired material characteristics for the elements of the meter jaw members 2. In certain embodiments, the meter jaw members 2 are formed by an extrusion process 99 (FIG. 13). In the process 99, the cross sectional shape of the meter jaw members 2 is extruded at step 100. The extrusion may be cut to selected lengths for convenient handling and for treating at step 102 for desired metal characteristics of the meter jaw members 2, including desired strength, hardness, stiffness, elasticity, and the like. Such treatments may include heat treating. The treated extrusion lengths are cut or sliced into the individual meter jaw members 2 having specific depths at step 104. Finally, surfaces of the meter jaw members 2 is finished at step 106, which may include deburring, polishing, chemical cleaning, and tinning or plating with other metals. As stated previously, the manufacturing processes described for the meter jaw members 2 are also appropriate for the alternative embodiments of the meter jaw members 72, 78, 86, and 92, as well as the bus bar jaw members 88 and 90.
Heat generated in the jaw member 2 is directly proportional to electrical resistivity and length and inversely proportional to cross sectional area. The slight improvement of aluminum to brass is coupled with the significant improvement in both length and cross-sectional area to result in a jaw with less than ⅕ the resistance of a conventional jaw. The heat conducted through the jaw 2 is directly proportional to thermal conductivity and the cross-sectional area and inversely proportional to the length. Typical values of prior art and the invention indicate that nearly four times as much heat can be conducted through the new jaw. The thermal gradient in the new jaw is less than ¼ that of a conventional jaw, or about 8 degrees centigrade less.
The unique attributes of the invention described herein allow better utilization of the trade-offs required to construct an economically feasible meter jaw. Aluminum costs far less per pound than either copper or copper alloys. Aluminum is also easily and economically extruded. Aluminum is regularly used in electrical connectors for these reasons. By using an extrusion process, it is possible to economically vary the thickness of the jaw contact fingers, permitting better mechanical, electrical and thermal performance. Aluminum is currently approximately ⅓ the density and ½ the price of copper or copper alloys. This results in a 6 to 1 cost advantage for this invention per unit volume.
FIGS. 7 and 8 diagrammatically illustrate a comparison of electrical and thermal conduction paths of a meter jaw assembly 2 according to the present invention with electrical and thermal conduction paths of a conventional meter jaw member 204, as previously shown in FIG. 1. Typical dimensions of the jaw member 204 are 0.75 inch (19.05 mm) wide by 0.047 inch (1.19 mm) thick, providing a cross sectional area of about 0.035 square inch (22.74 mm2). The electrical and thermal conductive path 110 of the meter jaw member 204, represented by the heavy surface line in FIG. 7, extends from the area of contact of the jaw member 204 to the area of contact of the jaw member 204 with the wire connector 214 (FIG. 1) and has an effective length of 1.672 inches (42.47 mm) on each side of the meter jaw member 204. In contrast, a meter contact jaw 12 of the meter jaw member 2 has a width of 0.875 inch (22.23 mm) and a midpoint thickness of 0.074 inch (1.88 mm) for an average cross sectional area of about 0.065 square inch (41.77 mm2). The effective length of electrical and thermal conductive path 112 for each jaw contact 12 of the jaw member 2 is 0.877 inch (22.28 mm). Thus, the jaw contacts 12 have a much greater cross sectional area and a much shorter path than a comparable portion of the conventional jaw members 204 to provide greater electrical conductivity and lower resistive heat generation while providing greater thermal conductivity for any heat generated by conduction or contact resistance between the meter blade and the jaw contacts 12.
FIGS. 9
a,
9
b, and 10 illustrate an embodiment of a slide-in meter socket assembly 120 that can utilize the one-piece slide-in meter jaw members 3. The insulative slide-in mounting block 6 has an aligned pair of open key slots or channels 122 that cooperate with the slide-in keys 46 of meter jaw members 3 to position the jaw members 3 on the mounting block 6. The illustrated key channels 122 are open toward the center of the mounting block 6 and closed toward the outer ends of the block 6. The jaw members 3 are retained in place by a jaw retainer 124 having gusseted guide plates 126 at its ends which engage the jaw contacts 12 of the jaw members 3 and also act as guides or position limits for the blades of the watt-hour meter when inserted. The retainer 124 is secured to the mounting block 6, as by a fastener 127 such as a screw or bolt. The illustrated retainer 124 has an essentially rectangular pocket feature that may receive an optional terminal to provide a ground reference for a meter blade when required. The mounting block 6 positions a pair of meter jaw members 3 in a spaced apart relation with the blade receiving spaces 16 thereof aligned to receive the aligned blades on one side of a conventional watt-hour meter.
The illustrated mounting block 6 includes grooves or notches 128 and apertures within bosses (not shown) on an underside of the block 6 to receive and properly position a wire meter support 130. Slide nut and slide nut screw assemblies 132, including a slide nut 34 and a slide screw 38, are then positioned in the receiving grooves 32 of meter jaw members 3 to engage and clamp stripped ends of power cables (not shown). Alternatively, a retainer/support member (not shown) could be configured which integrates the features and functions of the jaw retainer 124 and the meter support 130. A complete assembly 120, as shown in FIG. 9b, forms one half of a four terminal meter socket which is installed within a meter socket enclosure 228. The slide-in mounting block 6 may be formed from any suitable insulative material, such as from any one of a number of plastics, as by molding which is sturdy, stable, and highly insulative. The mounting block 6 may, for example, be formed of a glass fiber reinforced polycarbonate. The mounting block 6 may include sets of locating pegs 134 which engage holes in a mounting bridge 232 (FIG. 2) when the assembly 120 is installed within an enclosure 228.
FIGS. 11 and 12 illustrate an embodiment of a mold-in meter socket assembly 140 that can utilize the mold-in meter jaw member 4. The mold-in mounting block 7 has the meter jaw members 4 integrally molded thereinto and has notches 142 to receive and locate a wire meter support (not shown) similar to the support 130 of FIGS. 9a and 9b. The illustrated mounting block 7 has a centrally located pocket 144 including an aperture (not shown) to receive a mounting screw (not shown) similar to the mounting screw 127 of FIG. 9a. The pocket 144 is provided to receive an optional terminal (not shown) to provide a ground reference for a meter blade when required. The illustrated mold-in mounting block 7 includes integral meter blade guides 146 which are gusseted for reinforcement. The mounting block may also include locating pegs 148 (FIG. 12) The meter jaw members 4 are adapted to receive the slide nut and slide screw assemblies 132 within grooves 32 to secure the ends of power cables therein.
FIG. 14 illustrates a process 250 for forming the mold-in meter socket assembly 140. At step 252 a pair of mold-in meter jaw members 4 are inserted into a mounting mold apparatus (not shown) with the mold-in keys 48 thereof extending into the mold cavity having the shape of the mold-in mounting block 7. At step 254, a resin in a plastic state is injected into the mold cavity to fill the cavity and to surround the keys 48. The serrated surfaces 60 of the keys 48 helps to strongly retain the jaw members 4 in the mounting block 7. At step 256, the resin is solidified, as by cooling and/or curing. At step 258, a completed meter socket assembly 140 is ejected from the mold apparatus in a form similar to the assembly shown in FIG. 11. The mounting block 7 may be formed of materials similar to the mounting block 6, such as glass fiber reinforced polycarbonate. The mold-in assembly 140 greatly economizes assembly of a watt-hour meter socket by substantially reducing the part count and by automating assembly of the meter jaw block sub-assembly.
It is to be understood that while certain forms of the present invention have been illustrated and described herein, it is not to be limited to the specific forms or arrangement of parts described and shown.
Patent Application
20080057797
