Modular watthour meter socket and test switch

A watthour meter has, in one aspect, a flexible seal with a locking head carried on the meter base and a strap extending from the head and disposable in a loop around and through apertures in juxtaposed mounting flanges of the meter base and the meter dome to lockably join the dome and base. A tamper detector is carried on a blade moveably extending through the base. Movement of the blade during separation of the meter from the meter socket jaw contacts triggers the tamper detector. A connecting pin extends through aligned openings in the base and the dome to non-separably join the base and the dome. The pin engages a tamper signaling switch to provide an indication of a change of in pin state during a tamper event.

BACKGROUND

The present invention relates, in general, to watthour meters and/or watthour meters socket adapters.

Electrical power is supplied by an electric utility to individual use sites by power line conductors which extend from the utility poles to a meter socket mounted on a convenient surface at the use site. The power line conductors are physically connected to line jaw contacts in the meter socket. Distribution conductors extend from load jaws mounted in the socket throughout the use site.

An electric power watthour meter is provided for measuring the power consumed by a use site by measuring the current drawn by the use site from the line to the load conductors. A watthour meter typically has a base on which metering components are mounted. Blade terminals extend from the base for interconnection in the socket line and load jaw contacts so as to place the meter in series between the power line conductors and the power load conductors. A dome historically formed of glass surrounds the electro-mechanical metering components mounted on the watthour meter base. The dome includes a mounting flange which overlays a flange on the base and is fixed to the base by a metal mounting ring. A seal is used to then secure the dome to the base.

With the advent of electronic meters and automatic meter reading equipment, the glass dome has been replaced with a plastic dome or cover typically having a view window in an end wall for viewing an electronic display of power consumption. The mounting flange on the plastic domes are formed with slots for engagement with a standard meter base carrying the blade terminals and metering components.

The watthour meter is installed in the socket and/or in a socket adapter or socket extender which is mounted in the socket which also carries mating jaw contacts by inserting the meter blade terminals into the meter socket or socket adapter jaw contacts.

A concern which arises with any watthour meter design, whether of the automatic reading type or a more conventional, electronic or mechanical watthour meter, is the ability to detect tampering with the meter, such as the removal of the meter to insert wires to bypass the meter and thereby obtain free, unmetered power. In addition to removing the meter, certain tampering events involve the removal and the replacement of the meter in an inverted position in the socket so as to cause reversal of the rotation of the measuring disk.

Other tampering efforts have involved separation of the meter dome from the meter base to enable tampering with the internal mechanical, electronic, or electrical components of the meter in order to obtain free power.

On-site inspections of watthour meter mounting configuration by utility personnel have become less frequent. This has encouraged would be tamperers to increase their efforts to unauthorizedly obtain electric power from the meter socket without payment. This is despite the elaborate anti-tampering design features built into each watthour meter, meter socket adapter and meter socket and other tampering detection circuits and devices.

Older tamper detection devices were mechanical in nature and frequently included an orientation sensitive switch, also known as a tilt switch, which detected reverse mounting of the watthour meter in the socket after the meter is first removed from the socket. Once removed, a single phase meter could be installed upside down resulting in reverse rotation of the meter disc and register dials which record cumulative energy consumption. The existence of a single tampering event or the recording of the number of times a tampering event was typically detected and stored in a memory device in the watthour meter.

While effective, such mechanical tampering detection devices still require some type of on-site inspection to determine the tamper detection elements detected a tampering event.

One method of providing a tamper indication between the meter dome or cover and the meter base is shown inFIG. 1and involves the use of a metal T-shaped seal. The seal, which typically is formed of aluminum, has a generally flat head and an elongated, bendable stem. The stem is inserted through aligned apertures in the metal band surrounding the meter dome flange and the base flange.

During assembly of the watthour meter, after the dome is mounted on the base, the T-seal is inserted stem first through aligned apertures in the ring and base. As the end of the stem passes through an aperture in the base it encounters a ramp surface which bends the end of the stem out of the plane of the remainder of the stem. The end is further bent back manually over the stem itself as shown inFIG. 1to lock the seal on the base.

In use, any attempt to pull the T-seal from the base, will cause the bent end to sever from the remainder of the stem thereby providing an indication of a tamper event.

However, since the meter is normally mounted in a socket when tampering occurs, the separation of the end of the stem from the T-seal causes the short metal end to fall into the interior of the socket which is carrying voltage. This metal piece could create a dangerous arcing condition.

Thus, it would be desirable to provide a safer means for sealing or providing a tamper indication lock of a meter dome and/or a cover to a meter base which avoids problems associated with prior art meter seals.

It would also be desirable to provide a watthour meter having an approved tamper event detection which effectively detects any initial separation of a watthour meter from the meter socket jaws which is capable of providing a tamper detection event signal which can be transmitted internally and/or externally of the watthour meter.

SUMMARY

The present invention is a watthour meter having improved tamper detection features over previously devised watthour meters.

The watthour meter of the present invention is formed of a base carrying metering components and a dome coupled to the base.

In one aspect, a receiver means is carried on the base. A seal in the form of a flexible tie having a strap which is looped through apertures in the joined meter base and cover extends through a locking head on the tie for non-releasably securing the flexible tie to the base and cover. Separation of the tie is an indication of tampering.

The receiver means may comprise a receptacle on the base for receiving the locking head of the tie. Apertures are formed in the receiver means for receiving the strap of the tie in a loop configuration around edges of the base and the dome.

In another aspect of the present invention, a hanger is provided for hanging the watthour meter in a vertical orientation prior to installation of the watthour meter in the meter socket. A fastener is mounted in a closed bore in the base and pivotally attaches the hanger to the base. The fastener extends through a hollow post formed in the base and is completely insulated from the electrical power carrying components of the meter. A projection is carried on the base for angularly positioning the hanger in a meter hanging position as well as to secure the hanger in a storage position for use of the meter.

In another aspect of the present invention, tamper detection means is provided for detecting a separation of the watthour meter from a meter socket. The tamper detection means includes at least one blade moveably carried in the base and adapted for connection to a watthour meter socket jaw contact. Tamper signaling means is responsive to the detection of movement of the blade upon separation of the watthour meter from the meter socket jaw contact and provides a tamper detection signal.

In one aspect, the tamper signaling means is a switch having a switchable contact which provides an electrical signal upon detection of blade movement. The tamper signal may be used within the watthour meter to provide a visual and/or audible signal of a tamper event and/or transmitted remotely from the watthour meter for an external tamper indication.

In another aspect, a connecting or seal pin extends through aligned openings in the base and the dome and is latched to one of the base and the dome. An inner end of the pin engages a tamper detecting means or switch to provide an indication of a change of state of the pin. The pin also non-rotatably and non-separably joins the meter dome and meter base.

The watthour meter of the present invention contains several unique features which overcome deficiencies found in previous watthour meters. The unique seal formed of a flexible tie with locking head provides a dome/base tamper indicating seal which prevents rotation between the cover and dome while at the same time is formed of an electrically insulating material to minimize any arcing or short circuits with current carrying components in the meter socket in the event of separation of any portion of the seal or tie from the watthour meter. The seal or tie receiver is integrated into the base and cooperates with apertures in the receiver, base and cover to provide the desired mounting of the seal by a simplified, low cost construction.

The present invention also provides a unique fastener for pivotally coupling the temporary mounting hanger to the base which is completely electrically insulated from the meter components to prevent the formation of a conductive path through the hanger to the interior of the meter.

A unique tamper detection means is provided in the form of means for detecting movement of a unique moveably mounted blade on the base. The moveable blade exhibits movement relative to the bottom wall of the base during the initial stages of separation of the watthour meter from the meter socket jaw contacts. This movement is detected by the tamper detector means which generates a signal to provide an indication of tampering. The signal can be in multiple forms for use on the watthour meter or being capable of being sent remotely from the watthour meter to a central utility station.

In one aspect, a connecting or seal pin extends through the base and the dome and is latched to one of the base and dome to non-separably and non-rotatably join the base and the dome. The connecting pin engages a tamper detecting device or switch which generates a tamper event indication signal during a change of state or position of the connecting pin.

DETAILED DESCRIPTION

Referring now to the drawing and toFIGS. 2–12in particular, there is depicted a watthour meter20having a meter dome/cover/meter base tamper indicator or seal means22, constructed in accordance with one aspect of the present invention, mounted thereon. The meter dome or cover, hereafter referred to simply as the dome24, has a generally cylindrical shape formed of a cylindrical side wall26extending from a first end28at a closed end wall30to an opposed end32which is formed as a mounting flange having a top annular ledge34and an axially extending rim36. The ledge34and the rim36form a step which disposes the rim36at a slightly larger outer diameter than the diameter of the side wall26. This allows the end32of the dome24to overlay and engage a complementary formed rim on a meter base40.

The meter dome24is formed of a suitable electrical insulting material. While the dome24could be formed of glass, a more cost-effective material is an electrically insulating plastic. The meter dome24could be formed of a transparent material, such as a transparent plastic, for ease in viewing the interior metering component power consumption display.

As is also shown by example only inFIGS. 2 and 3, the meter dome24is provided with a handle42which may be integrally formed with side wall26. The handle42, which can take a variety of shapes, is shown to be in the form of a outwardly extending lip projecting over a predetermined angular extent of the sidewall26and having an end44spaced from the end wall30. The handle42provides a convenient gripping surface to assist in installing and removing the entire watthour meter20into and from a meter socket.

Returning to the end32of the meter dome24, as shown inFIGS. 2 and 3, at least one and preferably a plurality of circumferentially spaced apertures, typically in the form of slots48, are formed through the ledge34and open inside of the inner surface of the rim36. An arm49is formed on the inner surface of the rim36and projects in a space manner under each aperture or slot48. The arm49cooperates with a mating flange on the base40to rotatably join the cover24to the base40.

The base40, shown in greater detail inFIGS. 3–10, includes a bottom wall50. A annular side wall52extends from the periphery of the bottom wall50. The side wall52is defined by an inner ledge54, and a pair of radially spaced rings56and58which are spaced apart to define an annular groove60. The groove60is capable of receiving a shield62, shown inFIG. 14. The shield62, which can be formed of an opaque or translucent flexible plastic, may have any length so as to be disposed within the side wall26of the cover24and block at least a portion of the metering components mounted on the base40from exterior view.

An annular flange64projects radially outward from the outer surface of the side wall52and is spaced from the outer ring58of the side wall52by an annular groove66which is designed for receiving a fluid seal, such as a resilient O-ring, not shown.

A plurality of circumferentially spaced discontinuities or notches68are formed in the flange64. The discontinuities or notches68receive the arms49on the dome24when the second end32of the dome is axially aligned with and engaged with the base40. A rotation or twisting movement supplied to either or both of the dome24in the base40causes the arms49to rotate underneath the flange64and axially fix the dome24to the base40.

A plurality of slots70are formed in the bottom wall50of the base40for receiving meter blades as shown inFIGS. 14–16and described hereafter. Other features on the base40are employed for connections to the metering components, not shown, which are normally mounted on the base40and housed within the interior of the meter dome24.

As shown inFIGS. 3,4and5, and in greater detail inFIGS. 6–13, the watthour meter20includes a receiver means80. The receiver means80includes a boss82which is disposed on the bottom wall50of the base40. The boss82is in the form of an enlarged block, which is mostly solid, such as would result from an integral, one piece molding with the base40. A seal receptacle84is formed in the block82adjacent to one end of the block82which is adjacent to the inner ring56of the side wall52.

The seal receptacle84has an outer lip86which surrounds an irregularly shaped open-ended cavity88. The cavity88extends through the lip86and a substantial distance into the block82.

The cavity88includes an enlarged central bore90and opposed, smaller dimensioned ends92and94. The ends92and94extend from an open end on the upper surface of the lip86to inner ends96and98, respectively, which are disposed above a bottom wall100defining the bottom of the central bore90of the cavity88.

As shown inFIGS. 8 and 9, notches102and104are formed in opposed sides of the lip86adjacent to the notch94.

A first aperture106is formed in the bottom wall100. A second aperture108is formed in one wall of the notch94. A third aperture110is formed in one wall of the notch92. The apertures108and110are laterally aligned.

A projection107is formed in the bottom wall100and is shaped as a wedge tapering outward into the first aperture106from the top surface to the bottom surface in the orientation shown inFIG. 9. The projection107wedges against a flexible tie inserted into the aperture106to hold the tie in an interference fit in the aperture106, as described hereafter.

The seal receiver cavity88is configured for releasably receiving a seal means, such as a flexible tie120, as shown in detail inFIG. 11. The flexible tie, which is also known as a cable or wire tie and is sold by Panduit Corp., is formed with a locking head122having a through-bore or throat124in which is mounted a locking pawl126. A strap128extends integrally from the head122and terminates in an end130. One or more gripping projections132may be formed adjacent to the end130on one side or surface of the strap128. A plurality of teeth134disposed at a close spacing extend from the head122for a substantial predetermined distance along the length of the strap128on an opposite side or surface of the strap128.

A bend138may be formed in the strap128spaced from the end130to facilitate wrapping of the strap128in a loop so as to enable the end130to be inserted through an inlet end of the throat124in the head122and be forced through the throat124through an outlet end140. The teeth134engage the pawl126to prevent a reverse movement or pullout of the strap128from the head122. In this manner, the strap128is locked in a loop as described hereafter.

An optional tab142can also be integrally formed on and extending from the head122in a direction opposite from the direction of extension of the strap128. The tab142facilitates installation and handling of the tie120as well as providing a convenient writing or label surface for indicating the date of installation of the seal, the installer or other information, etc.

As shown inFIGS. 5 and 7, the back surface51of the bottom wall50of the base40is formed with a pocket150below the boss82. The pocket150includes an inclined or angled end wall152, the purpose of which will become more apparent hereafter.

A guide way having opposed inward tapering sidewalls154and156is formed in the flange64on the back surface51on the bottom wall50on the base40to guide the end130of the seal120into the aperture108, through the notch94in the block82, through the head122of the seal120disposed in the cavity88, as described hereafter, and then through the aperture110in the opposed notch92. The end130, on continued insertion through the head122, contacts the inclined or angled end wall152of the pocket150and is urged away from the back surface51. The end130may then be grasped to pull the seal120in a tight loop around the mating edges of the dome24and the base40to seal the dome24and base40together against rotational movement and to provide an indication of an attempted separation of the dome24from the base40when the seal120is broken, severed or removed from the meter20

As shown inFIG. 12, the end130of the seal120is first inserted into the cavity88and the block84and through the aperture106and the bottom wall100of the block84until the head122seats within enlarged center portion90of the cavity88, with the main portion of the head122facing radially inward from the side wall50to the base40. In this position, the throat124in the head122is aligned with the apertures108and110for passage of the seal120therethrough. The projection107wedges against the strap128of the tie120to retain the tie120in the cavity88. Further, in this mounting position, the lower edges of the tab142of the seal120seat in the notches102and104formed in the block84.

As shown inFIGS. 12 and 13, prior to mounting of the dome24to the base40, the seal120is inserted into the receiver80as described above. The end130of the seal120is left extending from the back surface51of the bottom wall50of the base40. The dome24is then locked to the base40by alignment of the slots48and fingers49with a corresponding notches68and the flange64of the base40. After engagement of the flange32of the dome24with the flange64of the base40, rotational movement is imparted to one or both of the dome24of the base40to rotatably offset the base40from the cover24. This slides the fingers49below the adjacent solid portions of the flange64to axially lock the cover24and base40together to prevent axial separation unless one of the cover24of the base40is rotated to bring the fingers49back into alignment with the notches68in the flange64of the base40.

After the dome24and base40have been locked together, the end130of the seal120is looped around and through the apertures in the base40and the head122. The end of the strap128of the seal120extend below the back surface of the base50and may be cut off to avoid interference with adjacent portions of the meter socket in which the meter20will be mounted.

Another feature of the inventive watthour meter20is a unique mounting connection of a hanger180used to temporarily mount the watthour meter20in a vertical orientation prior to installation in a meter socket.

The hanger180is in the form of a strap182, typically of metal, and having generally circular aperture184adjacent one end and a keyhole shaped aperture186adjacent an opposite end.

A fastener188, such as a threaded bolt or a pop rivet, is passed through the aperture184in the hanger180and into a post190projecting inward from a platform192on the front surface of the bottom wall50of the base40. The post190may be internally threaded or the fastener188may be a self-tapping fastener to enable the fastener188to be threadingly coupled to the post190.

The post190has a closed exterior so as to completely enclose all the fastener188. This electrically insulates the fastener from the internal components of the meter20.

A smooth portion on the shank of the fastener188allows pivotal movement of the strap182between a watthour meter use position wherein the strap182completely overlays the platform192and a pivotally extended position shown inFIGS. 2,4and5, in which the strap182extends at an acute angle with respect to the platform192. A stop194may also be formed as a projection on the platform192to act as a stop to angularly position the strap182in the desired position to enable the end of the slot186to be disposed along a vertically extending center line through the base40to enable temporarily mounting of the base40of the meter20on a hook, not shown. The stop194also engages the aperture186when the hanger182is pivoted to an overlaying position on the platform192to secure the hanger182in this position during installation, use or movement of the meter.

Another aspect of a watthour meter is shown inFIGS. 14–17. A plurality of blades, with two blades200and202being shown by way of example only, are mounted in the bottom wall50of the base40. Each blade has a first end portion204extending from the bottom surface51of the base50and adapted for engagement with a meter socket jaw contact206, shown inFIGS. 15 and 16, which is fixedly mounted in a meter socket, not shown. Each blade202also includes an opposed end portion208which projects into the interior of the base50above a front surface of the base50. The end portion208of each blade200and202contains apertures for connection to the metering components mounted on the base40.

Each blade, such as blade202, is fixedly mounted in the bottom wall50of the base40by a pair of projections or dimples210formed in the blade202intermediately between the opposed ends206and208and a fastener, such as a cotter pin212which is extendable through another aperture in the blade202spaced a predetermined distance from the dimples210so as to trap the bottom wall50of the base40securely between the pin212and the dimples210without movement of the blade202.

A tamper detection and indicating means is provided to detect and indicate unauthorized tampering with the meter20as defined by an unauthorized separation of the meter20from the jaw contacts206in the meter socket.

The tamper detection means includes at least one moveable blade, such as the blade200, which is reciprocally moveably mounted in one of the slots70in the base40. The moveable mounting of the blade200can be effected in a number of ways. In one instance, the spacing between the dimples210and the cotter pin212can be increased by a slight amount, as shown inFIG. 15, to permit movement of the blade200over a distance214shown inFIG. 15.

Another mounting configuration can eliminate the dimples but adds a movement detector, such as a microswitch216seen inFIGS. 15 and 17. The microswitch216is mounted to the blade200by fasteners218, for example. The microswitch216has at least one and on a plurality of terminals220projecting from one end for connection by wires to signal responsive components mounted within the watthour meter20, such as a relay, an automatic meter reading circuit, etc.

A moveable plunger222extends from the body of the microswitch216and is normally disposed in contact or slightly spaced from the bottom wall50, but in a non-activated or depressed state as shown inFIG. 15in the normal mounting position of the meter20in the meter socket. In this position, the cotter pins212is disposed in substantial registry with the bottom surface51of the base40so as to prevent any movement of the blade200in a direction out of the jaw contact206separate from movement of the base40. A biasing means disposed internally within the body of the switch216to normally bias the plunger222outward to a pressure responsive state, is also sufficient to bias the blade200in the desired normal mounting position shown inFIGS. 14 and 15.

It should be noted that during insertion of the meter20into this meter socket, the end204of the blade200will initially contact the outer edges of the socket jaw contact206. This will force the cotter pins212into engagement with the bottom surface51of the base40to provide a rigid, non-moveable blade200structure for further insertion of the end204toward the blade200into the socket jaw contact206.

When the meter20is separated from the meter socket, as shown inFIG. 16, the initial separating movement of the base40of the meter20relative to the socket jaw contact206is possible over the distance214. However, the blade200is held captive in the jaw contact206and does not initially move with initial movements of the base40. However, this initial movement of the base40depresses the plunger222of the switch216since the switch216remains fixed in position on the blade200. The plunger222switches an internal contact within the switch216and provides an output signal on the terminals220. This output signal on the terminals220, which is an indication of separating movement of the base40of the meter20relative to the meter socket can be conveyed, to a relay on the base40for internal or external activation of a light, audible alarm or other tamper event detection indicating means as well as by a direct signal or via a relay or other signal conditioning element, as an input to an automatic meter reading device mounted within the meter20to likewise activate a visible and/or audible light or alarm shown inFIG. 26in the meter20and to convey a remote signal to the utility company of the detection of a tampering event.

Another aspect of a tamper detecting means employed in a watthour meter or electrical service apparatus is shown inFIGS. 18–26. In this aspect, the meter20can have the same dome24and base40construction described above and shown inFig. 1.

As shown inFIGS. 18–20and22–25, the bottom wall50of the base40is positioned between an upturned, annular sidewall230. The upper end of the sidewall230transitions into a radially outward extending ledge232. A slot or bore234which can be disposed at a non-perpendicular angle with respect to the radial extent of the ledge232, extends through the ledge232from a first end on the radially outer surface236of the ledge232to an inner end opening to the interior of the base40. The bore234may taper outwardly in increasing width from the first end to the second inner end.

As described above, the sidewall26of the dome or cover24also transitions into a radially outward extending ledge240. The outer edge of the ledge240transitions into an axially depending rim242which overlays the outer surface236of the ledge232of the base40when the dome24is mounted on the base40as shown inFIGS. 18–20.

An aperture244is formed in one or both of the ledge240and the rim242of the dome24and opens to one end of the bore234in the base232. The aperture244provides access to the bore234for insertion of a connecting or seal means, such as a connecting pin250shown inFIGS. 19,21,22,23,24, and25.

The connecting means, hereafter referred to as a connecting pin250, is formed of a high strength material which resists bending or breakage. For example, the connecting pin250may be formed of a metal, such as steal, brass, etc.

As shown in detail inFIG. 21, the connecting pin250may be formed of a one-piece, integrally cast or machined body having a first end252, a shank254, and the opposed second end256. A flange258projects angularly from the stem254at the first end252. The second end256may have a tapered edge260, by example only.

A latch means262is carried by the connecting pin250. The latch means262may be integrally cast or machined in the connecting pin250, such as in the stem254at an intermediate position between the first and second ends252and256.

The latch means262may be in the form of a bendable latch arm264which extends over a cut-out or recess266in the stem254. The latch-arm264is bent under a pre-load force to extend angularly from the plane of the stem254as shown inFIG. 22. The latch-arm264terminates in a tip-end268. The inner edge268of the latch-arm262can be tapered or disposed at a non-perpendicular angle relative to the longitudinal axis of the latch-arm262.

In assembling this aspect of the meter20, the dome or cover24is mounted on the base40in the orientation shown inFIG. 19. In this position, the aperture244in the dome24is aligned with one end of the bore234extending through the ledge232on the base40as shown inFIGS. 19 and 20. The second end256of the connecting pin250is then inserted through the aperture244in the dome24and the bore234in the ledge232of the base40until the tip end of268of the latch-arm264passes an inner edge270of the ledge234on the base40. During such insertion, the latch arm264is bent into the plane of the stem254until the tip end268clears the surface270of the ledge232. At this time, the latch arm264snaps back to its normal, angular position with respect to the stem254bringing the tip end268into latching engagement with the inner surface270of the ledge232of the base40thereby latching the connecting pin250between the cover24and the base40to rotatably fix the dome24on the base40while at the same time preventing rotation or separation of the dome24relative to the base40.

With the watthour meter20mounted in a meter socket, not shown, when the socket cover271of a ringless socket,FIG. 22is mounted over the dome to the socket housing, or a sealing ring273is mounted over the rim244and adjoining portions of the dome24and the ledge232of the base40, the socket cover271or the sealing ring273will bias the first end252of the connecting or seal pin250toward the rim236moving the pin250further into the interior of the base40. This biasing force urges the opposed second end256of the pin250into forced engagement with tamper event detection signaling device, such as a micro switch290. The microswitch290, which can be fixedly mounted on the bottom wall of the base40, includes one or more terminals or output connections292which provide an electrical signal through a switchable contact291,FIG. 26, within the interior of the microswitch290. The state of the contact290is switched by a movable, spring biased plunger294having an end extending outward from the micro switch290. The biased inward position of the connecting pin250, as shown inFIG. 25, causes the second end256of the pin250to move the plunger294from a first, normal, outward most extending position to a depressed position relative to the housing of the microswitch290. This places the internal contact in the micro-switch290in a first state, which can be opened or closed depending upon the signaling circuitry. This contact position could be used to indicate the normal mounting position of the cover or dome24on the base40. However, any removal or separation of the cover24from the base40, which will require breakage of the connecting pin250, as described hereafter, or a predetermined amount of rotation of the cover24relative to the base40, the tip end268of the connecting pin250to disengage from the inner surface270of the ledge244of the base40. The internal biasing force exerted on the plunger294in the microswitch290will then cause the plunger294to move outward, pushing the connecting pin250radially outward sufficiently to cause the internal contact in the microswitch290to change states or positions to a second position indicative of a tampering event. The connecting pin250and the tamper event signaling device form a tamper detection and signaling means.

The bore234through the ledge232of the base40, in addition to being angled relative to the bottom wall50of the base40, may also be tapered from at an outer end of the ledge234to a wider cross-section at an inner edge of the wall230on the base40. This enables rotational movement of the latch-arm262relative to the inner end270of the ledge232as described above.

The connecting pin250also resists separation of the dome24from the base40. Removal of the dome24from the base40can be accomplished only by removing the entire meter20from the meter socket and then breaking the pin250, such as by separating the outer lip or flange258from the stem254. It will be noted that any separation of the meter20from the meter socket will also be detected by the tamper detection means.

The signal from the contact291in the microswitch290is output through the terminals292which may be connected, as shown inFIG. 26, to various tamper indicating devices. The terminals292may be connected through an intermediate relay, not shown, or directly to a visible tamper indicating means, such as an illuminatible lamp or LED294, mounted on the meter20in a visible location or through an external conductor to an illuminatible means294in the meter socket. Alternately or concurrently, the output signals from the terminal292of the microswitch290may be connected to an audible alarm, such as a horn or siren296, which again can be mounted on or in the meter20or in the meter socket.

The output signals from the microswitch290may also be connected via the terminals292to a relay298having an internal contact299which switches state when the relay298is activated by a signal from the microswitch290. The signal300from the contact299can be conveyed remotely from the meter20and/or meter socket for a remote tamper indicating signal.

In summary, there has been disclosed a watthour meter having unique features not found in previous watthour meters. Such features include a unique tamper detection means using a moveably mounted meter blade and blade movement detector, an electrically insulated mounting of the temporary meter hanger, a flexible seal formed of an electrically insulating material to seal the meter cover and base while at the same time providing a tamper indicator of unauthorized separation of the meter cover from the meter base.

In another aspect, a connecting pin insertable through aligned openings in the base and the cover is latchable to the base to prevent rotation and/or separation of the cover from the base. The inner end of the pin is biased into engagement with a tamper detection and signaling means, such as a microswitch. The microswitch provides an indication of a tamper event when the connecting pin is disengaged from the plunger of the microswitch thereby enabling the internal contact of the microswitch to change state. This signal can be conveyed to one or more tamper indicating devices on the meter and/or meter socket, such as visual or audible signaling devices, including lamps, LEDs, horns, sirens, etc. The tamper detection signal from the micro-switch can also be conveyed as a remote signal to the utility company, etc., for remote indication of a tamper event occurring with a particular watthour meter.