The present invention relates generally to contact assemblies, and more particularly, to a one-piece meter jaw and to meter socket assemblies incorporating such jaws, such as for use in a socket for a direct-reading watt-hour meter. This type of socket is known in the trade as an “S” type meter socket. It has a standardized form to allow the interchangeability of meters from various manufacturers without removing any wires or cables. A watt-hour meter having a typical pattern of a pair of parallel sets of aligned connector blades is shown in U.S. Pat. No. 4,104,588, which is incorporated herein by reference. While such a meter socket is employed for meters capable of continuous full load currents of 20 to 400 amperes, it is most typically utilized for residential applications at 200 amperes.
In standard plug-in “S” type meter sockets, a watt-hour meter is plugged into a meter socket which is mounted in an enclosure. This configuration must provide means to make the electrical connection to the incoming and outgoing power cables or bus bars. In this type of meter socket, the electrical connections to the meter, as well as the retention of the meter in the meter socket, is performed solely by a plurality of meter jaws. These jaws are electrically connected to means for electrical connection to the power cables or bus bars. Because these jaws and connectors are all connected to separate electrical potentials, they must be fixedly supported by one or more insulating mounting bases or blocks, which are in turn secured to the enclosure.
In one known configuration, the meter jaws are constructed of flat metal that is formed to create a conductive receiving jaw in such a manner that there is a resulting compressive force which is required to retain the meter blades in the jaws. The compressive force must be sufficient to reduce the heating that will occur as current is passed through the watt-hour meter, but must be low enough to permit installation of the meter into the meter socket and removal of the meter therefrom. Some specifications require that the force required to insert the meter, which may have from 4 to 7 meter connections, into the meter socket be less than 100 pounds. The selection of materials for such jaws is a compromise. The metal must have high electrical conductivity to reduce the resistive heating effects and high thermal conductivity to permit conduction of the heat out of the meter sockets through the power cables. It must also be relatively short and thick to lower its bulk resistance to minimize the heating effects. On the other hand, the mechanical form of the meter jaw must be such that the yield strength of the material is not exceeded as the meter blade is engaged to such an extent that the jaw does not substantially return to its initial geometry when the meter blade is retracted or an additional supplemental spring component would be required. In order to insure these mechanical characteristics, the mechanical form of the jaw should be relatively long and thin in cross-section. The conductive element is often chosen to be a bronze, brass, beryllium-copper, or other alloy rather than copper or aluminum, which are more electrically and thermally conductive.
Because of these trade-off characteristics, many meter jaw designs employ additional separate components which function as springs to supplement the compressive forces provided by the electrically conductive elements of the meter jaws. Additional components are also used to guide the meter into the jaws and to electrically and/or mechanically connect the meter jaw, electrical connector, mounting base and enclosure.
The prior art meter socket described above has several disadvantages. Firstly, the use of a high number of components acts to reduce reliability. Secondly, the high number of components acts to increase assembly costs. Yet another disadvantage of the current art is the temperature rise permitted. Agencies such as Underwriters Laboratories specify temperature rise limits for meter sockets and their components. A limit is specified for the connector to insure that connecting cable insulation or bus bars are not damaged or degraded. A 10 degree Centigrade higher limit is imposed on the meter jaw to insure that watt-hour meters are not degraded or damaged. Most current art meters exhibit this 10 degree difference. It is the result of the geometry of the meter jaw and its electrical and thermal conductivity. Many modern watt-hour meters employ semiconductor electronic components. These and other electronic components exhibit reduced life phenomena at increased temperatures.
The present invention provides greatly improved watt-hour meter socket components and assemblies thereof which reduce the number of components required for each meter jaw in a meter socket, which reduce the number of manufacturing operations required to manufacture the electrical connector used in each meter jaw, which reduce the heat generated in each meter jaw in a meter socket, and which minimize the thermal gradient from the meter jaw to the power connection.
The meter socket assemblies of the present invention generally include one piece meter jaw members for receiving connector blades of watt-hour meters and are generally formed of a base tab, a pair of resilient meter jaw contacts extending from the base tab and having outer curved sections mutually curved toward one another and positioned in mutually spaced relation to form a meter connector blade receiving space between the outer curved sections. The jaw contacts have such geometric configurations and material characteristics as to exert a selected force on a meter connector blade having a standard industry specified thickness when received in the blade receiving space. Additionally, an electrical power connector extends from the base tab and is configured to receive a power cable, a bus bar, a bus bar connector, or the like.
More specifically, the meter jaw contacts are generally S-shaped and extend from the base tab in mutually spaced, back-to-back relation therefrom. In one embodiment of the meter jaws, the electrical power connector is formed by a U-shaped conductor having spaced apart legs connected by a curved bight section and sized to received to receive an electric power cable. Slide nut grooves are formed into opposite internal surfaces of the legs to receive a slide nut having a slide screw threaded therein for clamping a stripped end of the electric power cable between the slide nut and the U-shaped conductor. The meter jaw may include a meter jaw mounting key extending from the base tab for use in mounting the meter jaw member on an insulative meter jaw mounting block to form a half of a watt-hour meter socket assembly for mounting into a meter socket enclosure.
In a mold-in embodiment of the meter jaw assembly, the meter jaw mounting key is a mold-in mounting key, formed by a key web extending from the base tab with a plurality of key flanges extending from opposite sides of the key web to form substantially serrated surfaces on the opposite sides of the key web. A pair of the mold-in meter jaw members are positioned in spaced relation within a mounting block mold with the mold-in mounting key extending into the mounting block mold cavity. The meter jaw members are properly positioned and oriented to align the meter blade receiving spaces. A resin in a plastic state is injected into the mold cavity and allowed to solidify or cure whereby parts of the pair of meter jaw members are molded into the mounting block to simplify forming a meter socket assembly half.
In a slide-in embodiment of the meter jaw assembly, a slide-in meter jaw mounting key is formed by a key web extending from the base tab and terminating in a key flange spaced from the base tab. An insulative meter jaw mounting block is formed with a pair of aligned key retainer channels which receive the key flanges to position a pair of meter jaw members in aligned and spaced relation on the mounting block. A meter jaw retainer member is secured to the mounting block to retain the meter jaw members in place within the slide-in meter jaw assembly. The slide-in embodiment of the meter jaw assembly has a few more parts than the mold-in embodiment and requires more assembly steps. However, the slide-in embodiment significantly reduces the parts count and assembly steps required to form a meter socket assembly.
Various objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention.
The drawings constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof.
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.
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.
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 (
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
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 (
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 (
a-6f illustrate alternative embodiments of the meter jaw members 2 and bus bar connectors 66 (
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.
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 (
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.
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
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.
This application claims priority under 35 U.S.C. 119(e) and 37 C.F.R. 1.78(a)(4) based upon U.S. Provisional Application, Ser. No. 60/842,125 for AN IMPROVED METER JAW ASSEMBLY, filed Sep. 1, 2006, which is incorporated herein by reference.
Number | Name | Date | Kind |
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3281550 | Waldrop | Oct 1966 | A |
4104588 | Westberry | Aug 1978 | A |
4201439 | M'Sadoques | May 1980 | A |
5595316 | Gallarelli et al. | Jan 1997 | A |
5870276 | Leach et al. | Feb 1999 | A |
6561844 | Johnson | May 2003 | B1 |
20050227532 | Kellerman | Oct 2005 | A1 |
Number | Date | Country | |
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20080057797 A1 | Mar 2008 | US |
Number | Date | Country | |
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60842125 | Sep 2006 | US |