Patent Description:
The tap-off boxes of the invention include a number of improvements, including the addition of a mechanism for automatically latching the tap-off box to the busway. Other improvements, which are not part of the invention, could be the addition of current transformer (CT) sensor assemblies that detect breaker status in addition to monitoring currents distributed via the tap-off box, and replaceable faceplates that permit thermal scanning of internal components from outside the tap-off box.

An example, not part of the invention, also relates to an improved CT sensor that detects tripping of a breaker, in addition to monitoring currents, and that may be used in a power distribution sub-assembly or power tap for a busway or track, as well as in other current-sensing applications.

The rigorous demands of mission critical data center sites require methods to quickly disconnect and reconnect equipment without removing power from any other equipment. Additionally, all power distribution systems of the type used in mission critical data centers and other sites requiring continuous power distribution to multiple devices must be capable of providing monitoring of power parameters both locally and remotely. An example of such a power distribution system is disclosed in <CIT>. and incorporated herein by reference.

<FIG> is a perspective view of a section of the power track or busway illustrated in <CIT>. The busway is made up of a power track housing assembly that supports isolated high current conductors. A commercial version of the illustrated busway is sold by Power Distribution, Inc. as part of the POWERWAVE™ and POWERWAVE <NUM>™ bus systems. As illustrated in <FIG> , the busway housing assembly includes a housing or enclosure <NUM> ; insulators <NUM>; the high current conductors or bus bars <NUM>; and auxiliary sub-channels <NUM> that may contain communications components, such as data signal-carrying electrical or fiber optic communications cable <NUM> and data connectors <NUM> for connecting the cable to monitoring circuitry in the individual tap-off boxes, and/or an isolated ground conductor for engaging a corresponding ground element (not shown) extending from the tap-off box. Housing or enclosure <NUM> may further include grooved runways <NUM> extending along the top and sides of the housing assembly for mounting or securing electromagnetic interference (EMI) shielding and/or mounting plates (not shown) that enable the busway to be secured to a ceiling or overhead mounting structure.

It will be appreciated that the present invention may be applied to or used with busway systems other than the one disclosed in <CIT>, or the PowerWave™ bus systems, and that features of the tap-off box may be varied to accommodate the different bus systems without departing from the scope of the invention. On the other hand, it is to be understood that the preferred embodiment of the invention shares features with the PowerWave™ bus system, including spring contacts that engage the conductors or bus bars <NUM>, and a spring contact camming mechanism that is activated, as described below, by a slidable and rotatable knob.

US patent application <CIT> discloses a tap-off box distributing power from a busway of an electrical power distribution system. The tap-off box comprises a housing including power distribution and monitoring components and a mast that extends from the housing and includes a plurality of electrical contacts for engagement with respective conductors in the busway, as well as a snap-on fixing mechanism. <CIT> shows a similar arrangement, wherein the mast of the tap-off box is inserted into a channel of the busway and the whole assembly is rotated so as to mechanically fix and electrically connect the tap-off box to it.

<CIT>, <CIT>, XP055735813 and XP055735829 disclose additional tap-off boxes with contact masts which are mechanically fixed to the busways through screws.

<CIT> shows yet another tap-off box with a mast, wherein the mast comprises electrical contacts and a fixing tab that are actuated through a lever in order to, respectively, electrically connect and mechanically fix the tap-off box to the busway.

One of the improvements offered by the present invention relates to securing of the tap-off box to the busway, and in particular to a latching mechanism that is independent of the contact-engagement mechanism, and that automatically latches the tap-off box in place before the camming mechanism is activated to cause the spring contacts to engage respective conductors in the busway. The inclusion of an independent latching mechanism ensures that the tap-off box is properly positioned at the time the contacts are engaged so as to ensure a proper connection and avoid damaging the contacts, while also preventing the tap-off box from being unintentionally pulled from the busway while the contacts are engaged, which could cause damage to the contacts or busway and present a serious safety hazard.

Unlike known tap-off box latching mechanisms, the latching mechanism of the invention does not require a complex interlock with the contact-engaging mechanism, and furthermore does not require any action on the part of the installer other than insertion of the tap-off box contact mast into the busway. In contrast, prior tap-off box arrangements having independent latching mechanisms, such as the ones disclosed in <CIT> and German Publication No. <CIT>, have required some sort of manual intervention on the part of the installer to secure the tap-off box after the mast has been inserted into the track or busway.

For example, the tap-off box securing mechanism of <CIT> uses a spring-biased member that automatically extends into a slot only after a mast of the tap-off box has been inserted into the track and the tap-off box and mast have been rotated into a final contact-engaging position. In this arrangement, a spring-biased blocking member prevents rotation of the tap-off box back to a position at which it can be removed. On the other hand, the tap-off box latching mechanism disclosed in German Patent Publication No. <CIT> provides positive latching of a tap-off box upon purely linear insertion of a contact assembly into the track, without any rotation, but requires a complex "connecting mechanism" consisting of dual axially opposed spring-biased "connecting elements" that snap-on to latch the tap off box to the rail by engagement between bearing surfaces on the connecting elements and abutment surfaces on the rail, and further requires an additional "locking mechanism" operated by a handle in order to both initially prevent movement of the locking elements in a disengaging direction, and also to move the locking elements in a disengaging direction.

Other examples of non-automatic tap-off box latching mechanisms include those disclosed in <CIT> and <CIT> and <CIT>, in which the latch and contacts are actuated and withdrawn together by a common switch or lever; <CIT>, which discloses a latching mechanism operated independently from the contact engaging/disengaging mechanism, but in which the latching mechanism is still lever- operated in both the latching and unlatching directions; and <CIT>, which discloses a latching mechanism that is lever-operated to move a latching member in the latching direction, against a spring bias in the unlatching direction (which is operated the direction needed to achieve automatic latching).

Finally, by way of further background, non-automatic tap-off box securing mechanisms or means that are neither automatic actuated by levers, cam, or the like include those of <CIT>, which describes a tap off box latching arrangement actuated by a cover interlock; <CIT>, which discloses a cover-operated interlock for the contacts only, and in which the tap-off box is secured to the bus by screws; <CIT>, which discloses a tap off-box with cover-contact interlock that is simply hung from the busway by hooks; and <CIT>, which discloses a cover-operated interlock between a load switch and the contacts.

Another improvement not part of the present invention relates to monitoring of current in a branch circuit carried by the tap-off box, and in particular to the use of a new type of non-contact current sensor in which is installed a plastic or graphite voltage-sensing insert that provides an anchor for the current sensor and that replaces an auxiliary circuit breaker trip detection switch to detect tripping of a respective circuit breaker in the corresponding branch circuit.

It is known to use arrays of current transformer (CT) sensor components to non-invasively monitor current in branch circuits, both in connection with a breaker panel board and also in a tap-off box. Such CT sensor arrays are disclosed, for example, in <CIT> and <CIT>. Other conventional CT sensor arrays and housing configurations are disclosed in <CIT>; <CIT>; and <CIT>, and <CIT>;<CIT>;<CIT>;<CIT> ; <CIT>; and <CIT>. Of these, <CIT> is of interest because the CT sensor assembly an additional component, in the form of a memory chip <NUM>, embedded in the individual transformer housing. However, none of the conventional current sensors have a way to detect whether an absence of current is caused by a tripped circuit breaker or just normal operation of the branch circuit. Instead, it has heretofore been necessary to provide an auxiliary circuit breaker trip detection switch operated by the movable contact arm assembly of the breaker to detect whether a current interruption has been caused by tripping of the breaker. While effective, the inclusion of auxiliary breaker trip detection switches in a multiple-breaker tap-off box, where space may be at a premium, is inconvenient and costly. Furthermore, each different type of breaker will require a different auxiliary trip detection switch. Because the trip detection switch is mechanically connected to the breaker, there is no way to provide a single auxiliary switch that can be used with multiple circuit breaker configurations.

Another especially advantageous feature that may be provided in the tap-off box, but which is not part of the present invention, is a replaceable faceplate made of a material transparent to infrared radiation so as to permit infrared scanning of breakers from outside the tap-off box, and that may be replaced by a different infrared radiation transparent faceplate to accommodate different breaker configurations without having to replace the entire cover. By way of background, Power Distribution, Inc. 's <CIT> discloses a cover made of infrared transmissive material to facilitate infrared scanning of internal components, (col. <NUM>, lines <NUM>-<NUM>), but not with a variable configuration breaker faceplate for diverse types of breakers.

It is accordingly an objective of the invention to provide an improved tap-off box for a power distribution busway system.

It is also an objective the invention to provide an improved latching arrangement for a tap-off box.

These objectives are achieved, according to one aspect of the invention, by a tap-off box for distributing power from a busway of an electrical power distribution system as it is defined in claim <NUM>. The tap-off box that includes a latching mechanism that automatically secures the tap-off box to the busway upon insertion of a spring contact-carrying mast into the busway. Automatic latching of the tap-off box enables the spring contacts to be safely moved by an installer into engagement with conductors in the busway.

According to a preferred embodiment of the invention, the latch is in the form of a single spring-loaded member that latches onto a rail as the masthead is pushed into the busway. A push button actuated camming member pushes the latch away from the rail to enable the masthead to be withdrawn from the busway. The push button and camming member are independent of the mechanism that extends and retracts the spring contacts while the masthead is inserted and latched into the busway.

Still further objectives, not part of the invention, are achieved by a tap-off box with a cover configured to include a replaceable infrared transmitting faceplate that can be adapted for a variety of different breaker configurations. According to a preferred embodiment not part of the invention, the cover may also include a replaceable current monitoring module with breaker status indicator lights.

These and other features of the present invention will become apparent from the following description and accompanying drawings.

It shall be noted that the embodiments shown in <FIG> include various features which are not subject to the present claims.

Throughout the following description and drawings, like reference numbers/characters refer to like elements. It should be understood that, although specific exemplary embodiments are discussed herein there is no intent to limit the scope of present invention to such embodiments. To the contrary, it should be understood that the exemplary embodiments discussed herein are for illustrative purposes, and that modified and alternative embodiments may be implemented without departing from the scope of the present invention, as defined in the claims.

<FIG> show a latching mechanism and a contact-engaging mechanism for a universal tap-off box according to a preferred embodiment of the invention. The tap-off box includes a generally planar quadrilateral mast <NUM> that extends from a tap-off box housing <NUM>. Mast <NUM> supports four spring contacts <NUM>-<NUM>, two of which (<NUM>, <NUM>) are on a front side of the mast <NUM>, as shown in <FIG>, and two of which (<NUM>, <NUM>) are on the rear side of the mast <NUM>, as shown in <FIG>. The spring contacts <NUM>-<NUM> are positioned to engage conductors <NUM> on the two sides of a busway of the type illustrated in <FIG>. Each of the contacts <NUM>-<NUM> is a generally rectangular plate spring attached at one end <NUM> to the mast <NUM> and having a distal, conductor- engaging edge <NUM> that rests against the mast when a camming mechanism is in an initial position, and that is cammed away from the mast against a restoring force of the spring when the camming mechanism is rotated to a conductor-engaging position after insertion of the mast <NUM> into the busway. The spring restoring force biases the spring contacts <NUM>-<NUM> towards the mast <NUM>.

The camming mechanism includes posts <NUM>, each having a cam shaped cross-section in portions of the respective posts that extend behind the spring contacts <NUM>-<NUM>. The posts <NUM> are rotatably secured to the mast by clips <NUM>, and each post includes a cylindrical base <NUM> having a radially extending bare <NUM> for receiving a horizontal crank post <NUM> attached to slider <NUM>, visible in an end view in <FIG>. Slider <NUM> is in turn attached to a knob <NUM> that is slidable along a horizontal guide slot <NUM> near a top of the tap-off box housing <NUM>.

In operation, the knob is initially on the left side as shown in <FIG>. In this position, the posts <NUM> are in a position in which the spring contacts <NUM>-<NUM> rest against or are flush with the mast <NUM>, allowing insertion of the mast <NUM> into the busway. Following insertion of the mast <NUM> into the busway, the knob <NUM> is slid to the right side of guide slot <NUM>, moving the crank posts <NUM> to cause rotation of the cylindrical bases <NUM>, which causes posts <NUM> to rotate. Rotation of the posts <NUM> cams the distal conductor-engaging edges <NUM> of spring contacts <NUM>-<NUM> away from the mast <NUM> and into engagement with the conductors <NUM> in the busway. Knob <NUM> can then be rotated to cause it to clamp the housing <NUM> of the tap-off box between the knob <NUM> and the slider <NUM>, preventing lateral movement of the knob <NUM> and locking the spring contacts <NUM>-<NUM> in the conductor-engaging position.

The configuration of the camming mechanism and spring contacts of the preferred embodiment illustrated herein may be the same as configuration of the camming mechanism and contacts in the PowerWave™ systems sold by Power Distribution, Inc. However, those skilled in the art will appreciate that the camming mechanism and spring contacts may also be varied without departing from the scope of the invention. Furthermore, unlike the conventional tap-off box connection system, the present invention adds an automatic latching arrangement that engages upon full insertion of the mast <NUM> into the busway, to hold the tap-off box in position before the spring contacts are engaged, and to permit the spring contacts to be disengaged by manipulation of knob <NUM> while the tap-off box is still securely locked in position.

The latching mechanism of the present invention is best viewed in <FIG>, and includes a single one-piece latch member <NUM> having a latch head <NUM> with a busway engaging surface <NUM> and an inclined cam surface <NUM>, a main body with a pivot notch <NUM>, a lower extension <NUM> with a pushing surface <NUM>, and a spring mounting slot <NUM> or integrated spring <NUM>. The pivot notch receives a pivot post <NUM> positioned in an opening <NUM> in the mast <NUM>, as shown in <FIG>. The busway engaging surface <NUM> is arranged to engage a top surface <NUM> of one of the subchannels <NUM> in the busway of <FIG>, but those skilled in the art will appreciate that the latch head <NUM> and busway engaging surface <NUM> may be arranged to latch onto horizontal surfaces of a busway other than the illustrated surface, including surfaces not associate with sub-channels, depending on the design of the busway, and that the invention is not limited to use with the busway of <FIG> or the particular latch member shape or structure illustrated in <FIG>. For example, the pivot notch <NUM> may be replaced by a hole or by an axle extending from the latch member <NUM>.

The latch member <NUM> is biased to pivot to the latching position by a separate spring fitted into slot <NUM>, or by the integrated spring <NUM>. During insertion of the mast <NUM> into the busway, the inclined cam surface <NUM> first encounters a lower portion of the sub-channel <NUM>, as shown in <FIG>, or any structure between the latch head <NUM> and the latch-engaging top surface <NUM>. The latch member <NUM> is then caused to pivot around post <NUM>, against the force of the spring bias, until the mast <NUM><NUM> is inserted into the busway by an amount sufficient to enable the latch head <NUM> to clear the sub-channel <NUM> or other structure, as shown in <FIG>, at which time the latch pivots in response to the spring bias and automatically engages the top surface <NUM> to latch the mast <NUM> within the busway and prevent removal of the tap-off box. At this time, the spring contacts <NUM>-<NUM> are positioned to face conductors <NUM>, and may be safely moved into engagement with the conductors by manipulation of knob <NUM>, as described above. In addition, completion of mast insertion results in independent ground springs <NUM>, if provided, being positioned within corresponding slots in the busway, and rails <NUM>, which extend from the top of the tap-off box, having engaged the busway housing <NUM>.

While engagement of the latching mechanism is automatic, disengagement is provided by an unlatching mechanism that includes an unlatching member <NUM> having an elongated main body from which extends a central pusher <NUM> for engaging the pushing surface <NUM> of the latch member <NUM>, integral or attached springs <NUM> for biasing the unlatching member <NUM> to a position in which the pusher <NUM> is disengaged from the pushing surface <NUM>, and buttons <NUM> for causing the unlatching member <NUM> to move against the spring bias and cause the pusher <NUM> to engage the pushing surface <NUM>. Further movement of the pusher <NUM> and pushing surface <NUM> in response to pushing of buttons <NUM> then causes the latch member <NUM> to pivot against its own spring bias, and busway engaging surface <NUM> to disengage from top surface <NUM> so that the tap off box can be removed from the busway. The use of two buttons <NUM> at opposite sides of the pushing member forces the operator to firmly grasp the tap off box by, for example, placing the operator's fingers on a surface of the housing <NUM> opposite the surface from which the buttons extend, on both sides of the box, and to simultaneously push on both buttons <NUM> by using the operator's thumbs in order to move the pusher <NUM> far enough to cause disengagement, thereby preventing premature or unintentional unlatching of the tap- off box and ensuring that the operator's hands are in a position to safely remove the tap off box by pulling vertically on both sides of the housing <NUM>.

<FIG> and <FIG> show the interior of the tap-off box of the preferred embodiment, which the front and sides of the housing removed. Housing <NUM> contains power distribution and monitoring circuitry, including circuit breakers, bus bars, and current sensors, as will be described below and which are not part of the invention.

Each of the spring contacts <NUM>-<NUM> is electrical connected by respective wires (not shown) that extend through the mast to terminals <NUM> positioned near a top of the tap-off box. Terminals <NUM> are connected to the circuit breakers <NUM> by a laminated bus system <NUM> made up of four plates <NUM>-<NUM> shown respectively in <FIG>, which distribute the current supplied through the four spring contacts <NUM>- <NUM> and corresponding terminals <NUM> into two branch circuits. Parts <NUM>-<NUM> are in the form of conductive plates with appropriately positioned terminals and laminated together with insulation layers to form a unitary assembly that can easily be installed in the tap-off box as a unit, and that can be customized for different circuit breaker and branch circuit configurations by forming the plates <NUM>-<NUM> to have appropriately positioned terminals. It will be appreciated that the circuit and circuit breaker configurations, including the number of spring contacts and bus conductors, and the number of branch circuits, may be varied. To this end, the use of the laminated bus assembly, which is preferred but not required, makes it possible to more easily vary the branch circuit configuration. Furthermore, in order to better accommodate different types of breakers or breakers with different current capacities, the breakers <NUM> are optionally mounted on an adjustable height mounting bracket <NUM>.

The downstream sides of the circuit breakers <NUM> and ground terminals <NUM> are connected by wires (not shown) to output connectors or receptacles <NUM>,<NUM> having selected alternative configurations, as will be described below in connection with <FIG>. The wires extend in conventional fashion through respective central openings in current sensors <NUM>,<NUM>, which are connected to a field replaceable monitoring module <NUM> via respective printed circuit boards <NUM>,<NUM> and an interposer printed circuit board <NUM> containing an output connector <NUM>. The monitoring module <NUM> contains circuitry for providing an output monitoring signal via a communications cable <NUM> that can, for example, be attached to a databus carried by one of the channels <NUM> in the busway. Those skilled in the art will appreciate that monitoring module <NUM> and communications cable <NUM> may be replaced by a different format module and connector as desired. The interposer printed circuit board <NUM> is preferably positioned above sensor circuit boards <NUM> ,<NUM> to save space, with connection between the circuit boards being provided by one or more jumpers or ribbon cables <NUM>. It will be appreciated that the configuration of the respective circuit boards <NUM>-<NUM>, output connector <NUM>, monitoring module <NUM>, and related components may be varied.

As illustrated in <FIG> and <FIG>, the current sensors <NUM>,<NUM> are non-contact, <NUM> single phase CT current sensors that surround the branch circuit connection wires extending between the output receptacles and the circuit breakers <NUM>. Such sensors are typically made up of wire wound toroidal coils on a metallic or nonmetallic core and enclosed within a plastic housing that may be mounted to the circuit board and electrically connected via terminals connected to the toroidal coils, and are commercially available. As a result, the sensors <NUM>,<NUM> may be freely varied, except to the extent that the current sensors <NUM>,<NUM> are capable of receiving voltage sensing inserts <NUM>.

The voltage sensing inserts <NUM><NUM> replace the auxiliary breaker switches commonly used to detect tripping of the breaker based on breaker contact positions, and may be made up of a generally annular, plastic or graphite encased non-contact voltage sensor element. As is well known, non-contact voltage sensing elements may take a variety of forms, such as a capacitive plate or wire (not shown). In order to detect tripping of the breaker, the voltage sensing elements are arranged to output a signal upon detecting a change in voltage that results when the breaker goes from a closed position to an open position. Rather than being connected to the current monitor, the signal-outputs of the insert are connected to monitoring and indicator circuitry that would otherwise be connected to the auxiliary switch. The auxiliary switch monitoring circuitry may, for example, control breaker operation indicator lights <NUM> on the monitoring module <NUM>, as shown in <FIG>. Monitoring module <NUM> preferably further includes a blind connector <NUM>, shown in <FIG>, for connection to the monitoring module output connector <NUM> on the interposer printed circuit board <NUM>.

<FIG> shows a side plate arrangement for the tap-off box housing <NUM> of the preferred embodiment. The side plates <NUM> illustrated in <FIG> are extruded aluminum panels that provide enclosure rigidity and strength as well as grounding continuity, and that are arranged to fit within a flange <NUM> of a back panel <NUM>. By varying the width of the side plates <NUM>, front panel or cover <NUM> (see <FIG>, <FIG>), and a receptacle panel <NUM> (shown in Fig. <NUM>), the thickness of the tap off box may be varied to accommodate different size receptacles <NUM>,<NUM> and/or breakers <NUM>.

The receptacle panel <NUM> shown in <FIG> fits within slots formed in the side plates <NUM> to ensure electrical ground continuity, and include openings <NUM> of various shapes to accommodate different sizes or types of receptacles such as, by way of example and not limitation, the IEC version receptacles <NUM> shown in <FIG> and the NEMA version receptacles <NUM> shown in <FIG>.

Those skilled in the art will appreciate that it is also possible to provide side panel or receptacle arrangements other than the illustrated arrangements, including arrangements in which the top, side, and bottom panels or plates are integral with the back or front panels, or formed in one piece therewith, and arrangements in which the receptacles are provided with adapters or extenders <NUM> to leave more room within the enclosure for bigger wires or cables. It is also possible, as shown in <FIG>, to provide one or more panels with an adapter such as the cover adapter <NUM> to increase the width to match the width of other panels or plates and allow increased enclosure depth.

As shown in <FIG>, the front panel or cover <NUM> preferably includes not only an opening <NUM> for the output connector <NUM> and a recess <NUM> for the monitoring module <NUM>, but also an opening <NUM> for receiving a field replaceable breaker faceplate <NUM>. The field replaceable breaker faceplate <NUM> may have various configurations to accommodate different types of breakers, and includes a plate <NUM> that is transparent to infrared radiation to enable infrared scanning of the breakers from outside the tap-off box, without having to remove the front panel or cover <NUM>.

Finally, as shown in <FIG>, the monitoring module <NUM> may optionally also include one or more additional light emitting diode (LED) indicator lights <NUM> to, for example, provide an indication that maintenance is required. To facilitate replacement of the faceplate <NUM>, the recess <NUM> may include posts <NUM> for receiving captive quarter turn fasteners <NUM> or similar fastening members. In addition, an adapter <NUM> may be provided to enable connection of the illustrated jack <NUM> with a Molex type micro-fit connector provided in the busway. Those skilled in the art will appreciate that the monitoring unit may use any of a variety of different communications protocols and jacks or adapters.

The present application further discloses a non-contact current monitoring assembly, comprising: a non-contact current sensor including a toroidal winding and a central opening for sensing a current in a wire passing through the central opening; and a voltage sensing insert at least partially positioned in said opening and fixed to the non-contact current sensor for detecting an open circuit condition of a circuit breaker connected to the wire. Therein, the voltage sensing insert might replace an auxiliary breaker switch.

The present application further discloses a tap-off box, comprising: a housing that encloses power distribution and monitoring circuitry and components, the power distribution and monitoring circuitry and components including at least one circuit breaker, wherein the housing includes a rear panel, a top panel from which an electrical contact supporting mast extends, a pair of side panels, a receptacle panel, and a front panel, the front panel including an opening arranged to receive a variable configuration breaker faceplate made of a plastic material that allows IR scanning of the power distribution and monitoring circuitry and components.

Claim 1:
A tap-off box for distributing power from a busway of an electrical power distribution system, the tap-off box comprising:
a housing (<NUM>) including power distribution and monitoring components;
a generally planar mast (<NUM>) that extends from the housing and includes a plurality of electrical contacts (<NUM>-<NUM>) for engagement with respective conductors (<NUM>) in the busway; and characterized by
a snap-on latching mechanism that includes a spring-biased latch member (<NUM>) pivotably attached to the mast (<NUM>) via a pivot post (<NUM>) positioned in an opening (<NUM>) in the mast, wherein the latch member (<NUM>) has a busway engaging surface (<NUM>) configured to engage a horizontal upper surface (<NUM>) of a structure (<NUM>) in the busway, the latch member (<NUM>) further including an inclined cam surface (<NUM>) configured to engage a lower surface of the busway structure (<NUM>) and cause the latch member (<NUM>) to pivot in a first direction as the mast (<NUM>) is inserted into the busway, the latch member (<NUM>) being moved in a second direction by the spring-bias into a latching position in which the busway engaging surface (<NUM>) engages the horizontal upper surface (<NUM>) of the busway structure (<NUM>) to latch the tap-off box into the busway after the latch member (<NUM>) has moved past the busway structure (<NUM>) upon full insertion of the mast into the busway; and
an unlatching mechanism (<NUM>, <NUM>) positioned adjacent the latch member (<NUM>) and configured to engage and pivot the latch member (<NUM>) in said first direction upon actuation by an installer to enable removal of the tap off box from the busway.