Abstract:
A fuse block for cabinet mounting provides a shaft that may exit a side of the cabinet to be received by a handle mounted on that side. A finger attached to the inner cabinet door provides for an interlock by engaging with a bolt communicating with the shaft preventing inadvertent opening of the cabinet when the fuse block is connected to power and/or connecting the fuse block to power when the cabinet door is open.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     BACKGROUND OF THE INVENTION 
     The present invention relates to electrical fuse blocks for mounting in cabinets and having rotary disconnect shafts extending out of the cabinets to a handle, and in particular, to a fuse block in which the handle may be mounted on the side of the cabinet yet which provides an interlock limiting operation of the fuse block when a cabinet door is open. 
     Fuse blocks, as are well known in the prior art, provide one or more sockets for receiving standard electrical fuses having a fusible link that will melt and separate when excessive current is drawn through the fuse. The fuse block may include terminals for attaching power connections to the fuse block, and thus serves to simplify the wiring of the fuses into series with power carrying conductors. 
     It is common to mount one or more fuse blocks in a cabinet having a door that may be closed to prevent inadvertent access to exposed conductors inside. The fuse block may incorporate a disconnect allowing disconnection of power from the fuse block. The disconnect may be used when fuses need to be changed or when it is necessary to remove power from the fuse connected circuits and the associated equipment when the equipment is idle or must be worked on. 
     The disconnect may be operated by a rotary shaft extending forward from the fuse block through the door cabinet to be received by a handle held on the cabinet door. The handle allows power to be disconnected without opening the cabinet door and exposing the internal wiring. The handle may, in addition, have a lockout accepting a padlock and preventing turning of the handle to reconnect power except by the holder of the padlock key. In addition, the handle may be designed to grip the shaft except when the disconnect is in the open circuit position, thus preventing opening of the cabinet door until power is removed from the fuse block. In this way, an interlock is provided to prevent unintended opening of the cabinet when the fuse block is connected. 
     In an alternative configuration of the fuse block, the shaft may extend out of a side of the cabinet to be received by a handle mounted on the sidewall of the cabinet. In this case, the handle is always connected with the fuse block shaft and thus does not serve as an interlock to hold the door closed when the fuse block is connected to power. 
     Generally, the fuse blocks will be placed in a wide variety of cabinets of different sizes and in different locations within the cabinets. What is needed is an interlock system for such a fuse block using a side mounted handle that works with a variety of different cabinet sizes and placements. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides a door interlock system that works with a fuse block having side mounted handles. A finger is attached to the door to provide an indication that the door is shut and a means for locking the door when the fuse block is powered. The interlock accommodates over travel of the finger thus allowing a single finger or small number of standard fingers to accommodate a variety of different cabinet dimensions and mounting conditions. 
     Specifically, the present invention provides a disconnect mechanism for a fuse block, where the fuse block receives power connections and has a support face for mounting against the rear panel of a cabinet to hold one or more fuses accessible from a front face of the fuse block opposite the support face. The disconnect mechanism provides a rotary shaft communicating with the fuse block and extending outward along the rear panel when the support face of the fuse block is mounted against the rear panel. An outer end of the rotary shaft is adapted to receive a portion of a door handle mounted on the side of the cabinet so that the rotary shaft can be rotated by the handle to disconnect the fuses from the power connections. 
     A bolt operator extends radially from the rotary shaft to rotate therewith and provide a stop surface that may be engaged by a bolt, the bolt moving between a lock position and an unlock position. In the lock position, the bolt engages the stop surface preventing free rotation of the rotary shaft to connect the fuses to power. In the unlock position, the bolt is disengaged from the stop surface allowing free rotation of the rotary shaft to connect the fuses to power. A finger mounted on the lid of the cabinet engages the bolt when the lid is closed to move the bolt to the unlocked position. 
     It is thus one object of the invention to prevent inadvertent connection of the fuse block to power when the cabinet door is open. When the cabinet door is open, the finger on the lid is withdrawn leaving the bolt in the locked position preventing free rotation of the rotary shaft to the “ON” position. 
     The bolt operator may further provide a bolt-retracting surface engaging the bolt to move the bolt to a door release position. The bolt may engage the finger to prevent opening of the cabinet door when the bolt is not in the door release position. The bolt-retracting surface may engage the bolt only when the rotary shaft is positioned to disconnect the fuses from the power connections. 
     Thus, it is another object of the invention to prevent opening of the door inadvertently when power is connected to the fuse block. 
     The finger may include a cam surface moving the bolt to the unlocked position when the door is fully closed. 
     Thus it is another object of the invention to allow for free reconnection of the fuse block when the door is closed. 
     The bolt may be a lever centrally mounted on an axle extending parallel to the rotary shaft. The lever may pivot about the axis of the axle to move between the locked and unlocked positions. 
     Thus it is another object of the invention to provide a simple mechanism to produce the interlock of the present invention. 
     The axle may be sized to extend through a sidewall of the cabinet when the support face of the fuse block is mounted in the cabinet. 
     Thus it is another object of the invention to allow overriding of the door-locking interlock in the event that it is necessary to have access to the cabinet while the power is on. It is an additional object of the invention to provide for this ability to defeat the locking of the door from a position near the handle that is accessible to the user. The end of the axle may extend outside of the cabinet and there, shrouded by a tube, may have a screw head to allow actuation of the bolt with a standard screwdriver fitting within the shrouded tube. 
     Thus it is another object of the invention to prevent inadvertent defeating of the door lock. 
     The lever may include a spring rotationally biasing the lever toward engagement with the bolt operator. 
     Thus it is another object of the invention to provide an interlock that may be overcome when the cabinet door is open in a secondary operation by moving the lever against its biasing spring manually. 
     The handle attachable to the sidewall of the cabinet to engage the rotary shaft may have a means for receiving a padlock to prevent rotation of the handle. 
     Thus it is another object of the invention to provide for an absolute lockout of the fuse block that may not be defeated even when the cabinet door is open. Because the handle is always connected to the rotary shaft, locking of the handle is sufficient in this regard. 
     It is another object of the invention to provide such a lockout that does not prevent access to the interior of the cabinet. Unlike a locking of a front handle, a locking of a side-mounted handle does not prevent opening of the door. 
     The bolt operator may be a cam disk and the stop and bolt-retracting surfaces may be portions of the periphery of the cam disk. Thus it is another object of the invention to provide an extremely simple mechanism for realizing the interlocks that are required. 
     The fuse block may include a fuse block shaft extending outward along a side face of the fuse block to be substantially perpendicular to the rear panel when the support face is mounted against the rear panel, and the fuse block shaft may support a gear having radially outward teeth, and the bolt operator plate may include a series of corresponding slots whose separations form teeth engaging teeth on the gear of the fuse block shaft whereby torque on the rotary actuator may be converted to corresponding torque on the fuse block shaft. 
     Thus it is another object of the invention to provide a kit for converting a standard fuse block having a forwardly extending rotary shaft for use with a side mount handle configuration using a thereby simplifying stocking and manufacturing of fuse blocks. 
     The above objects and advantages may apply to only some embodiments falling within the claims and thus do not define the scope of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a fuse block assembly of the present invention mounted to the side wall of a cabinet and having a side-extending disconnect shaft received by a sidewall-mounted handle and showing an interlock finger extending inward from a rear surface of a front door of the cabinet; 
     FIG. 2 is a simplified perspective view of the fuse block assembly of FIG. 1 showing a cam plate mounted to one end of the side mounted shaft engaged by the handle and a pivoting bolt such as interacts with the cam plate; 
     FIG. 3 is a top plan view of a gear that engages with gear slot/teeth on the cam plate of FIG. 2; 
     FIG. 4 is a cross-sectional view along lines  4 — 4  of FIG. 2 showing the relative orientation of the gear of FIG. 3, which fits on a frontward extending shaft of the fuse block, and the cam plate of FIG. 2, and further showing a pivot mounting of the bolt of FIG. 2 where the axle of the bolt is accessible from outside of the cabinet; 
     FIG. 5 is an elevational view of the bolt and cam plate of FIGS. 2 through 4 when the lid is open and the fuses of the fuse block are disconnected showing how the cam plate prevents a clockwise rotation of the bolt; 
     FIG. 6 is a figure similar to that of FIG. 5 when the cabinet door is shut such as moves a finger down to cause clockwise rotation of the bolt releasing the cam plate; 
     FIG. 7 is a figure similar to that of FIGS. 5 and 6 showing rotation of the cam plate after closure of the door of FIG. 6 to reconnect the fuse block power connection; 
     FIG. 8 is a figure similar to FIGS. 5 through 7 showing an interengaging of the bolt and finger when power is connected to the fuse block and an attempt is made to open the door; 
     FIG. 9 is a view similar to FIGS. 5 through 8 showing clockwise rotation of the cam plate to disconnect the fuse block and to cause clockwise rotation of the bolt releasing the finger to allow the door of the cabinet to be opened; and 
     FIG. 10 is a view of the cam plate of FIGS. 5 through 9 mapping the function of the cam plate onto its profile. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIG. 1, a fuse block assembly  10  may receive fuse cartridges  12  at its front face and may attach at its side face to a side wall of a cabinet  16  to abut the rear wall  14  of the cabinet  16 . The open face of the cabinet  16  may be covered by a door  26  supporting an inwardly extending finger  28 . 
     Input terminals along the top of the fuse block assembly  10  may receive power conductors  18  which connect independently through a set of disconnect contacts (not shown) to one side of each fuse cartridge  12 . The disconnect contacts may be controlled by a rotary handle  22  mounted to a sidewall  24  of the cabinet  16 . The use of a side mounted rotary handle  22  reduces some tolerance problems required when alignment with a handle on the door is required. Permanent locking of the fuse block assembly  10  may be obtained by using the lock mechanism previously built into the rotary handle  22  according to methods well known in the art. 
     As is understood in the art, when the disconnect contacts are closed, the fuse cartridges  12  joins power conductors  18  to power conductors  20  which attach at output terminals along the bottom of the fuse cartridge  12 . The power conductors  18  and  20 , for example, may be for three-phase power and may provide power to a motor or other piece of equipment (not shown). 
     Referring now to FIGS. 2 and 4, a fuse block  30 , being part of the fuse block assembly  10  and holding the fuse cartridges  12  and the disconnect contacts, may be mounted at its rear surface on a support plate  32 . An upwardly extending square shaft  34  (shown in FIG. 4) rotates to open and close the disconnect contacts and connect and disconnect the fuse cartridges  12  to and from the power conductors  18 . 
     Referring now to FIGS. 2,  3  and  4 , a quarter gear  36  having a hub  38  with a square aperture  40  may be fit over the vertically extending shaft  34  of the fuse block  30  and secured by a split ring  42  or the like. Teeth  44  of the quarter gear  36  extending horizontally parallel to the rear wall  14  engage corresponding teeth  46  formed as cutouts in a vertically oriented cam plate  48  turning about a shaft  50 . The axis of the shaft  50  is generally parallel to the rear wall  14  of the cabinet  16 , and perpendicular to the axis of the upwardly extending shaft  34 . The interengaging teeth  44  and  46  provide that rotation of the shaft  50  produces a corresponding rotation of shaft  34  and vice versa. 
     The use of quarter gear  36  allows the present invention to make use of a standard fuse block having a vertically extending fuse shaft  34  simplifying and reducing the number of different fuse blocks required for different applications. The fuse block  30  may be simply mounted on plate  32  holding the remaining components described herein to convert a standard fuse block  30  to a side mounting operation. 
     Referring to FIG. 4, shaft  50  may be supported on a bearing  52  attached to a vertical wall  54  formed by an upwardly bent section of support plate  32 . Vertical wall  54  may include feet  56  that abut the sidewall  24  of the cabinet  16  spacing the vertical wall  54  therefrom and serving to attach the support plate  32  to the cabinet  16  and in abutment with the rear wall  14  of the cabinet  16 . 
     As positioned, shaft  50  may extend through the sidewall  24  of the cabinet  16  to be received by rotary handle  22  held captive on sidewall  24 . It will be understood that in this way, a fuse block  30  having an upwardly extending shaft  34 , may be operated through a side mounted rotary handle  22  without changing the orientation of the fuse block  30  such as might decrease access to the fuse cartridges  12 . Generally therefore, rotation of the rotary handle  22  acting on shaft  50  causes a corresponding rotation of the shaft  34  allowing disconnecting and connecting of the fuses from outside of the cabinet. 
     Referring again to FIG. 2, vertical wall  54  of the fuse block assembly  10  also supports a lever bolt  60  having opposed upper end  62  and lower end  64 , these ends formed as outward and inward bends in the lever bolt  60 , respectively. Lever bolt  60  is center mounted on an axle  66  supported by bearing spacer  68  attached to the vertical wall  54  holding the axle  66  adjacent to and parallel with shaft  50 . Axle  66  turns with the lever bolt  60  and extends through sidewall  24  to be accessible near the rotary handle  22 . A tubular shroud  70  surrounds the axle  66  as it extends from the sidewall  24  out of the cabinet  16 . The outer end of the axle  66  includes a screw slot  72  that may be engaged by a screwdriver blade  74 . In this way, axle  66  may be rotated by intentional manipulation with a screwdriver, but is unlikely to be accidentally rotated. As will be described further below, rotation of the axle  66  allows overriding of the locking of the door  26  of the cabinet  16  when power is connected to the fuse block assembly  10 . 
     Referring to FIGS. 2,  4  and  5 , a spring  76  is wrapped about the bearing spacer  68  and connects between the vertical wall  54  and the lever bolt  60  to bias the lever bolt  60  in a counterclockwise direction (as viewed from inside the cabinet  16  looking toward the sidewall  24 ) so that the lower end  64  of the lever bolt  60  acts like a cam follower riding against the outer periphery of the cam plate  48 . 
     Referring specifically now to FIG. 5, in an initial state, the cabinet door  26  may be opened and the lower end  64  of the lever bolt  60  may be engaged with a stop surface  80  formed in the periphery of the cam plate  48 . The stop surface  80  has a radial face,  82  extending along a line of radius from the axle  66  and preventing counterclockwise rotation of the cam plate  48  when the lower end  64  is so engaged without creating an incidental outward force on the lower end  64 . A rear sloped face  84  of the stop surface, however, has a slope and thus allows clockwise rotation of the cam plate  48  such as pushes radially outward on the lower end  64  disengaging it. 
     Referring momentarily to FIG. 10, the periphery of the cam plate  48  clockwise from the stop surface  80  has a constant radius R 1  whereas the periphery of the cam plate  48  counterclockwise from the stop surface after the sloped face  84  has a constant radius R 2  greater than R 1 . The position of the cam plate  48  when the lower end  64  of the lever bolt  60  is engaged with the stop surface  80 , per FIG. 5, corresponds to a position of the shafts  50  and  34  in which the fuse cartridges  12  of the fuse block  30  are disconnected from the power connections as indicated by band  102   a . It will be understood therefore in FIG. 5, that with the lower end  64  engaging the stop surface  80   a , reconnection of the fuse cartridges  12 , per band  102   b , such as would require a counterclockwise rotation of shaft  50 , is prevented. However, a clockwise rotation of the cam plate  48 , such as does not reconnect the fuse cartridges  12 , is possible, with the lower end  64  riding up on the sloped face  84  to radius R 2 . Manual override of the system when the cabinet door  26  is open may be obtained easily by placing a finger on the upper end  62  of the lever bolt  60  and manually rotating it in a clockwise direction against its spring bias. 
     Referring now to FIG. 6, with closure of the door  26 , finger  28  descends proximate to the upper end  62  of the lever bolt  60 . Finger  28  has a wedge surface  86  that operates to push against the upper end  62  to cause clockwise rotation of the lever bolt  60  disengaging the lower end  64  from the stop surface  80  of the cam plate  48 . Accordingly, after door  26  is closed, cam plate  48  is free to rotate in a counterclockwise direction to cause engagement of the power conductors  18  to the fuse cartridges  12  per band  102   b  of FIG.  10 . 
     With such closure of the door  26 , the lower end  64  of the lever bolt  60  rides along the periphery of the cam plate  48  at the first radius R 1 . In this position, the cam plate  48  holds the lever bolt  60  away from the wedge surface  86  of the finger  28 , but still above a hook portion  90  of the finger  28  which dropped below upper end  62  when the door  26  was closed, effecting by a momentary clockwise rotation of the lever bolt  60  by second wedge surface  92  on leading edge of hook portion  90 . 
     Referring now to FIG. 8, with the lever bolt  60  held on the periphery of the cam plate  48  at R 1 , upward motion of the hook finger  28  as indicated by arrow  94  is blocked by the upper end  62  of the lever bolt  60 . Thus, without further effort, the door  26  may not be opened when the cam plate  48  is in a position connecting the fuse cartridges  12  to the power conductors  18 . 
     It will be understood from this description that a simple changing of the length of the finger  28  will allow the present invention to work with a variety of different cabinet sizes and mounting locations and further, that the exact dimensions of the finger  28  are not critical as the hook portion  90  may pass or over travel the upper end  62  of the lever bolt  60  by a considerable distance without undesirable effects. 
     Referring now to FIG. 4, the door  26  may nevertheless be opened in certain cases where it is necessary to have access to the interior of the cabinet  16  when the fuse cartridges  12  are connected to the power conductors  18  by defeating the action of the lever bolt  60 . This may be done by insertion of a screwdriver blade  74  into the shroud  70  to provide for a slight clockwise rotation of the lever bolt  60  with lower end  64  moved away from cam plate  48  against its biasing spring. 
     Alternatively, as shown in FIG. 9, cam plate  48  may be returned to its clockwise position disconnecting the power conductors  18  from the fuse cartridges  12  per band  102   a  of FIG.  10  and by further clockwise rotation, the lower end  64  of the lever bolt  60  may pass the stop surface  80  to ride up on the region of the periphery of the cam plate  48  at radius R 2  causing a clockwise rotation of the lever bolt  60  similar to that provided by the screwdriver and removing upper end  62  from interference with the hook portion  90  of the finger  28  so that the door may be opened. 
     In summary and referring to FIG. 10, when the door  26  is closed as indicated by bands  100  and  101 , there is free rotation of the cam plate  48  and thus, the fuse block may be connected or disconnected per band  102  without interference. Except for the use of a screwdriver blade as described above per band  101 , the door  26  may not be opened when the lower end  64  of the lever bolt  60  is aligned with any portion of the periphery of the cam plate  48  counterclockwise to the stop surface  80 . 
     When the door is opened as indicated by band  104 , rotation of the cam plate beyond stop surface  80  is blocked but there is free rotation of the cam plate  48  clockwise to the region counterclockwise to the stop surface  80 . 
     It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein, but include modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims.