Patent Publication Number: US-6982390-B2

Title: Advanced instrument packaging for electronic energy meter

Description:
RELATED APPLICATION DATA 
     This application is a divisional of application Ser. No. 10/229,778, filed Aug. 28, 2002 which is a divisional of application Ser. No. 09/490,992, filed Jan. 26, 2000, now issued U.S. Pat. No. 6,476,595 issued on Nov. 5, 2002, the entirety of which is incorporated herein by reference, which claims the benefit of provisional application No. 60/117,394, filed Jan. 27, 1999. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to electronic energy meters, and more particularly to packaging for electronic energy meters. 
     BACKGROUND OF THE INVENTION 
     Programmable electronic energy meters are rapidly replacing electro-mechanical meters due to the enhanced functionality achieved using programmable logic integrated into solid-state electronic meters. Some of these meters can be used to meter various different electrical services without hardware modification. For example, meters having a voltage operating range between 98 Vrms to 526 Vrms are capable of operation with either 120 V or 480 V services. U.S. Pat. No. 5,457,621, dated Oct. 10, 1995, entitled SWITCHING POWER SUPPLY HAVING VOLTAGE BLOCKING CLAMP, assigned to ABB Automation Inc. discloses examples of such meters. In addition, some meters are constructed for use with any 3-wire or any 4-wire service, also disclosed in U.S. Pat. No. 5,457,621. 
     However, many meters have complex packages that are difficult to assemble and which make it difficult to test the meter, leading to increased costs and lower reliability. Therefore, there remains a need for an electronic meter package that is easy to assemble, reliable, and permits easy testing of the enclosed meter. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to an electronic energy meter and its package. The meter package has a reduced number of parts, and the main circuit board assembly has the metering electronics on board, thereby eliminating the need for flying leads and point-to-point wiring within the package. Thus, the meter package is mechanically simplified compared to presently available meter packages, resulting in a lower cost and a more reliable meter contained therein. 
     According to aspects of the invention, the meter package comprises four primary parts, and eliminates the need for screw or rivet type fasteners. The only interconnections (electrical connections between the circuit board and metal hardware in the meter) are accomplished by the use of a voltage spring between the circuit board and the current bus conductors. 
     According to one aspect of the invention, current sensing elements are disposed on the circuit board. This allows current conductors to be installed through the current sensors during the mechanical assembly of the enclosure. 
     According to further aspects of the present invention, instead of a separate component known as a terminal block, the present invention has features molded into the enclosure bottom half, along with a multifunction partial or upper terminal block to provide the desired isolation between metal components. 
     According to another aspect of the invention, a serialized data label is incorporated into the package, thereby eliminating the need for adhesive and thus reducing overall production costs. 
     According to further aspects of the present invention, the meter further comprises a binocular that provides an uninterrupted link between the meter and an external device. The binocular comprises two directional guides that are separated by a rib. 
     According to further aspects of the present invention, the meter further comprises an actuator switch or pushbutton that can actuate or perform two functions with one button. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be better understood, and its numerous objects and advantages will become apparent to those skilled in the art by reference to the following detailed description of the invention when taken in conjunction with the following drawings, in which: 
         FIG. 1  is a schematic diagram of a meter assembly, exploded, in accordance with the present invention; 
         FIG. 2  is a front view of an exemplary meter (with the wiring cover removed) in accordance with the present invention. 
         FIG. 3  is a top view of an exemplary circuit board assembly with current sensors and current conductors in accordance with the present invention; 
         FIG. 4  is a side perspective view of an exemplary circuit board assembly with current sensors and current conductors in accordance with the present invention; 
         FIGS. 5A ,  5 B,  5 C, and  5 D are schematic diagrams at various views of an exemplary current conductor in accordance with the present invention; 
         FIG. 6  is a side perspective view of an exemplary current sensor assembly in accordance with the present invention; 
         FIG. 7  is a top view of an exemplary current sensor assembly with circuit board assembly and partial terminal block in accordance with the present invention; 
         FIG. 8  is a side perspective view of an exemplary current sensor assembly with circuit board assembly, partial terminal block, and a contact spring in accordance with the present invention; 
         FIG. 9  is an opposing view of  FIG. 8 , with a cutaway portion of the circuit board; 
         FIG. 10  is a perspective view of an exemplary current sensor assembly with a contact spring in accordance with the present invention; 
         FIG. 11  is a perspective view of an exemplary contact spring in accordance with the present invention; 
         FIG. 12  is a perspective view of an exemplary voltage disconnect link in accordance with the present invention; 
         FIG. 13  is a cutaway side view of  FIG. 12 ; 
         FIG. 14  is a schematic diagram showing an exemplary data label incorporated into a meter package in accordance with the present invention; 
         FIG. 15  is a cross-sectional view of an exemplary data label incorporated into a meter package in accordance with the present invention; 
         FIG. 16  is a front perspective view of an exemplary binocular in accordance with the present invention; 
         FIG. 17  is a rear perspective view of an exemplary binocular in accordance with the present invention; 
         FIG. 18  is a schematic diagram showing a binocular and an associated circuit board assembly in accordance with the present invention; 
         FIG. 19  is a perspective view of an exemplary actuator switch (exploded) in accordance with the present invention; 
         FIG. 20  is a perspective view of an exemplary inner actuator of an actuator switch in accordance with the present invention; 
         FIG. 21  is a bottom perspective view of an exemplary inner actuator in accordance with the present invention; 
         FIG. 22  is a perspective view of an exemplary outer housing of an actuator switch in accordance with the present invention; 
         FIG. 23  is a perspective view of an exemplary actuator switch (assembled) in accordance with the present invention; and 
         FIG. 24  is a rear view of a portion of an exemplary second enclosure portion in accordance with the present invention. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS AND BEST MODE 
     A perspective view (exploded) of an exemplary meter in accordance with the present invention is shown in  FIG. 1 . The meter comprises a first enclosure portion  10  and a second enclosure portion  20  that together form a case for containing the electrical components (e.g., a circuit board assembly  30 ). The meter further comprises a wiring cover  40  that attaches to the second enclosure portion  20 . A front view of an exemplary meter is shown in  FIG. 2  (with the wiring cover  40  removed). 
     The first enclosure portion  10  acts as the rear or base of the meter and comprises terminal block features  12  that eliminate the need for a complete separate terminal block. The terminal block features  12  form voltage isolation barriers between the various metal parts at different voltage potentials when they are encased in the assembly. This function works in conjunction with a partial terminal block  50  that is provided. The partial terminal block  50  has similar features as the terminal block features  12  and has features designed to mesh in an interlocking manner with the terminal block features  12  to form voltage isolation between the components it serves, while providing unrestricted access to the internal metal components and ease of assembly. Thus, instead of a separate component known as a terminal block, the present invention has features  12  molded into the bottom portion of the first enclosure portion  10 , along with a multifunction partial or upper terminal block  50  to provide the desired isolation between metal components. This arrangement provides superior performance by simplifying the assembly steps, permitting simultaneous assembly in clamshell fashion around all the components, and, at the same time, yielding higher voltage creeping distances between components. The total number of components is reduced because some of the metal parts are combined into one. 
     The second enclosure portion  20  acts as the front or top of the meter and preferably comprises a semi-transparent material to eliminate the need for a separate front cover. A window area  24  is provided for the digital display  31  of the circuit board assembly and product nameplate, for example. The other areas of the second enclosure portion  20  can be textured to provide a frosted appearance, thereby desirably obscuring the view into the inside of the meter product. This eliminates the need to have windows of separate clear material attached to the enclosure  20  or a separate front cover, and reduces the number of components. 
     The circuit board assembly  30  contains the electrical components and circuitry for performing typical meter functions, such as that described in U.S. Pat. No. 6,577,961, issued Jun. 10, 2003, entitled ENERGY METER HAVING PROGRAMMABLE FUNCTIONS, and incorporated herein by reference. Although the electrical components and circuitry of the circuit board assembly  30  can be any meter electrical components and circuitry that provide the desired functionality, an exemplary circuit board assembly having features in accordance with the present invention is now described. 
     Preferably, the circuit board assembly  30  comprises toroidal current sensors  33 . As shown in  FIG. 3 , current sensors  33  are disposed at approximately 45-degree angles on the circuit board assembly  30 . The toroidal current sensors  33  are mounted on the circuit board parallel to each other, but at an approximately 45-degree angle to the edge of the circuit board. This allows the current sensors  33  to be pre-installed on the circuit board assembly  30  using any conventional technique such as a wave solder technique. Although any current sensors can be used, current sensors having current transformers having low permeability cores (e.g., a permeability less than about 10,000 and preferably between about 1000 and 10,000) that are nanocrystalline or amorphous are preferred. An example of preferred cores are amorphous cores manufactured by Vacuumschmelze located in Germany. The advantage of this configuration is that it allows subsequent assembly of current conductors  35  through the center of each individual current sensor  33  after the current sensors  33  are mounted on the circuit board assembly  30 . This configuration eliminates point-to-point wiring and flying leads in the assembly, and provides a very compact assembly. 
     A current conductor  35  is inserted through the center of each current sensor  33 , as shown in  FIGS. 3 and 4 . Each current conductor  35  preferably comprises flat wires, instead of the conventional round wires, thereby enhancing the contact surface area. Preferably, the wires are formed, instead of stamped or punched, from a spool of flat wire, resulting in substantially zero waste.  FIGS. 5A ,  5 B,  5 C, and  5 D show top, side, front, and perspective views, respectively, of an exemplary current conductor. The angular bends in the wire allow it to be used in very compact assembly while maintaining desired separation between conductors due to the flat thickness dimension being advantageously utilized. 
     The ends of the current conductor  35  are inserted into a wire clamp  14  and fastened by a wire clamp screw  15 , as shown in  FIG. 6 . The wire clamps are attached by conventional fasteners to the partial terminal block  50 , as shown in  FIG. 7 . 
     The toroidal current sensors  33  are disposed so that the current conductors  35  are installed therethrough during the mechanical assembly of the enclosure. In this manner, individual test probes can be implemented for a current source while the current sensors  33 , mounted in close proximity to each other for a more compact design, are mounted and electrically connected to the circuit board, effectively creating a complete, working meter before final assembly in the enclosure portions  10  and  20 . This makes it possible to calibrate and test the “meter” as a circuit board, or component of the final assembly rather than only being able to calibrate and test the meter after final assembly in the enclosure. Thus, rework of failed circuits is easier, and the opportunity is provided to perform final assembly in locations where testing and calibration equipment is not available. 
       FIG. 8  shows a front perspective view of the circuit board assembly  30  attached to the partial terminal block  50  in accordance with the present invention, and  FIG. 9  shows an opposing perspective (cutaway) view. A flexible voltage contact spring  37  under stress and compression acts as a spring connection and provides a wireless and solderless voltage connection between current conductors  35  and the circuit board assembly  30 , thereby connecting the partial terminal block  50  with the circuit board assembly  30 . A side view of the interconnection of the circuit board assembly  30  and the current conductors is shown in  FIG. 10 . 
     An exemplary spring is shown in  FIG. 11 . The spring can comprise any material with adequate mechanical properties and electrical conductivity properties, such as stainless steel, phosphor bronze, or Be—Cu. Each contact area  38  of the spring is bifurcated  39  to yield a redundant contact point further enhancing the reliability of the connection. 
     The spring  37  is an axially loaded leaf spring design that is used to make the voltage connection between the current phase input to the circuit board assembly  30 . This mechanical connection is designed to maintain adequate contact pressure to result in a gastight electrical connection under the environmental conditions the product is rated for. The spring design eliminates flying leads and point-to-point wiring within the meter assembly. This design greatly simplifies the physical assembly of the product. As shown in  FIG. 9 , the spring  37  is retained in the assembly  30  by features  52  molded into the terminal block upper half  50 . No special tools are required for the assembly of these parts. 
     A voltage disconnect link is provided in an exemplary embodiment of the invention. The disconnect link of the present invention replaces remote wired hardware that is conventionally used as a voltage disconnect link. The disconnect link is used to isolate current and voltage sources during testing and calibration on some types of test equipment. The voltage disconnect link comprises voltage disconnect screw  61 , a voltage disconnect square nut  63 , and a voltage disconnect slot  64  in the circuit board assembly  30 , as shown in  FIGS. 10 ,  12  and  13 . The circuit board assembly  30  has at least one voltage disconnect link circuit pad  66  on a side of the voltage disconnect slot  64 , and can have more than one circuit pad  66  on the sides of the slot  64 . The voltage disconnect screw  61  and the voltage disconnect square nut  63  are assembled to slide in the slot  64 . At one end of the travel, the circuit pads  66  are shorted out by their contact with the screw assembly  61 / 63 , thereby completing the voltage circuit. At the other extreme travel position of the screw assembly  61 / 63  in the slot  64 , the screw assembly  61 / 63  resides in a pocket  55  (preferably rectangular) that is preferably molded into the terminal block upper half  50 . The pocket  55  in the terminal block upper half  50  prevents the rotation of the nut  63  and allows the assembly to be locked in either the open or closed position (with respect to the circuitry). Therefore, the voltage can be disconnected from a current source using this link assembly. To operate the disconnect link, a screwdriver is used to loosen the screw about ½ turn. At that point, the screw assembly  61 / 63  is free to slide in the slot  64  that it is assembled into. Also shown in  FIGS. 12 and 13  is an auxiliary voltage connector  8 . 
     Referring back to  FIG. 1 , the wiring cover  40  provides an access port  42  that allows access to an internal power connection jack  32  (disposed on the circuit board assembly  30 , for example) in order to power up the meter for reading the stored data when the electrical service to the meter is interrupted, for example. An access port cover  44  is provided, and can comprise a weather resistant adhesive backed seal, for example, that is applied over the access port  42  in such a manner as to render the port impervious to dust and moisture, while providing tamper-evident and anti-tamper sealing. In order to access the internal power jack  32 , a meter reader pierces, breaks, or removes the cover  44 , and inserts an external power plug that is part of an external power pack assembly (not shown) through the access port  42  into the internal power connection jack  32 . This permits the meter to be powered up for a data exchange. Once this operation is complete, the cover  44  can be replaced (or a new cover  44  applied) onto the wiring cover  40  over the access port  42 . 
     The components of the meter preferably snap together during assembly, using tabs and grooves formed on the enclosure portions  10  and  20 , for example, thereby eliminating the need for any screws. Anti-tamper seal screws  22  can be provided, for example, if required by the industry. 
     The arrangement of the components of the present invention simplifies the assembly steps, permitting simultaneous assembly in a clamshell fashion around the components, and, at the same time, yielding higher voltage creepage distances between components. The total number of components is reduced because some of the metal parts can be combined into one. 
     The meter package has a reduced number of parts, and the main circuit board assembly has the metering electronics on board, thereby eliminating the need for flying leads and point-to-point wiring within the package. Thus, the meter package is mechanically simplified compared to presently available meter packages, resulting in a lower cost and a more reliable meter contained therein. 
     According to an embodiment of the invention, the second enclosure portion  20  comprises a serialized data label  26 , as shown in  FIG. 14 . The data label  26  is preferably formed of a plastic, and has data (e.g., meter serial number, specification information, etc.) directly printed thereon, by a thermal transfer technique, for example. The data label can have any desired dimensions and size, such as a rectangle that fits behind the window  24 . Preferably, the data label  26  snap-fits onto molded retainer features  25  of the second enclosure portion  20  next to the window  24 , so that the data can be viewed through the window  24 . The molded retainer features can be ribs or grooves, for example. The second enclosure portion  20  preferably has a curved surface, as shown in  FIG. 15 , that assists in retaining the snap-fit label and provides rigidity to the enclosure portion  20 . The snap-fit eliminates the need for adhesive which prior art meter labels and nameplates rely on. Preferable material for the data label  26  is 0.010″ top coated DuPont polyester stock, manufactured by the DuPont, Wilmington, Del. Furthermore, because of the snap-fit, tedious and careful placement of an adhesive-backed label is avoided. 
     For optical communication, a device called a binocular  16 , as shown in  FIGS. 1 ,  16 , and  17 , is used. The binocular  16  provides an uninterrupted link between the meter and an external device. The binocular comprises two directional guides  17  for LEDs  18  mounted on the circuit board  30 , as shown in  FIG. 18 , and separated by a rib  19 . Preferably, the binocular  16  is molded out of an opaque resilient material, such as a thermoplastic elastomer, although any material can be used. The binocular  16  allows full contact between the second enclosure portion  20  and the circuit board assembly  30 , thereby ensuring maximum shielding of ambient light. The rib  19  prevents crosstalk between the LEDs  18 . Because the binocular  16  comprises a resilient material, it is flexible and not rigid and compensates for variance in tolerances of all the parts involved, thereby producing a good press fit under a large variance. This also will act as a shock absorber for the assembly. It should be noted that the binocular  16  is more desirable than using two separate, individual prior art light pipes to guide light signals because there is much less attenuation of the signal through the open air of the binocular directional guides  17  than in the imperfect transparent solids of conventional light pipes. 
     According to an embodiment of the invention, an actuator switch is incorporated into the meter. An exploded perspective view of an exemplary actuator switch  100  is shown in  FIG. 19  (exploded) and  FIG. 23  (assembled). The actuator switch  100  can be used to actuate multiple concealed switches of any kind. The switch  100  comprises an inner actuator  110  and an outer housing  120  that are assembled in the second enclosure portion  20 . 
       FIGS. 20 and 21  show a top view and a bottom view, respectively, of an exemplary inner actuator  110 . An upper gap  114  in the ribs  115  of the inner actuator  110  corresponds with the locking-tab  126  on the inside of the outer housing  120  ( FIG. 22 ). These features interlock together when the inner actuator  110  is inserted into the back of the outer housing  120 . Specifically, these features interlock together when the inner actuator  110  is inserted into the back of the second enclosure portion  20  and the outer housing  120  is inserted into the front of the second enclosure portion  20 . This keeps the assembly together and forces the inner actuator  110  and the outer housing  120  to travel up and down together. However, the inner actuator  110  is free to rotate within the outer housing  120 . Both sides of the flange  117  that forms the upper surface of the inner actuator  110  are designed to flex downward and give way to the locking-tab  126 . Referring to  FIG. 22 , the chamfer  128  on the bottom of the locking-tab  126  is designed to assist in the assembly process while preventing disassembly. The hex area  129  inhibits the outer housing  120  from turning within the second enclosure portion  20 . This also limits the downward travel of the actuator switch within the second enclosure portion  20 . 
     Cantilevered spring features  130  are disposed on the bottom of the outer housing  120  that return the switch to its up position. The actuator switch  100  is disposed through a hole  26  in the second enclosure portion  20 .  FIG. 24  shows a rear view of a portion of the second enclosure portion  20 . A boss  28  is disposed in the hole  26  on the back of the second enclosure portion  20  that limits the rotation of the inner actuator  110  to about 90 degrees either way. There are holes  122  in the outer housing  120  and another hole  113  in the inner actuator  110  that provide a way of sealing the actuator switch to a position where it will not rotate. This is to isolate one of the functions while still being able to actuate the other. There are two substantially flat flanges  116  on the bottom of the inner actuator  110 . These are preferably, but not be limited to, about 90 degrees apart. In this case, the flanges  116  interfere with associated tactile switches mounted on a circuit board. The drafting and coring features are present to reduce material and make the parts easier to mold. Molded plugs  105  are provided to prevent the rotation of the button without hampering the actuation of one of the switches. The slotted extension  118  on the top of the inner actuator  110  provides a way of turning assistance as with a coin or screwdriver. 
     Thus, the actuator switch can actuate or perform two functions with one button; i.e., it can activate two switches. First one switch is activated, and then the actuator switch is turned 90 degrees, and a second switch is activated. As described, the actuator switch is incorporated into the housing, and activates pads or switches on the underlying circuit board assembly  30 . 
     While the invention has been described and illustrated with reference to specific embodiments, those skilled in the art will recognize that modification and variations may be made without departing from the principles of the invention as described hereinabove.