Switchboard Cell for Receiving Switchgear Movable by Positioning Drive

The present invention relates to a switchboard cell for receiving switchgear movable by a positioning drive, with a door which closes the switchboard cell and having an opening for the passage of a tool provided for operating a threaded spindle of the adjustment drive.

A switchboard cell of this type has become known, for instance, from U.S. Pat. No. 4,112,269. Controlling such a switchboard cell may be dangerous to the user if no attention is paid to creating the prerequisites for a safe execution of the control action prior to certain such control actions.

In this connection it is an object of the present invention to prevent the motion of the switchgear by means of the adjustment drive if the door of the switchboard cell is open. Such a safety device is to be designed with purely mechanically and automatically acting means in order to avoid any dependence on auxiliary power.

The above and other objects of the present invention are achieved by a switchboard cell for accommodating switchgear which can be moved by a positioning drive, having a door which closes the switchboard cell and having an opening for the passage of a tool provided for operating a threaded spindle of the positioning drive, wherein the head piece of the threaded spindle on the operating side is associated with a stop which is guided movably in the direction of the longitudinal axis of the threaded spindle and can be blocked and released in dependence on the position of the door.

The stop prevents the tool from coming into engagement with the threaded spindle at all. This has advantages over blocking the threaded spindle since in this case, the attempt could be made to overcome the safety device by the use of force.

Blocking and release of the stop body in dependence on the position of the door requires the selection of part of the door travel and transforming it into a suitable motion of a latching member or the like. This can advantageously be accomplished by means of a flexible transmission member, the jacket of which is fixed in the vicinity of the door and a guiding element of the stop body in respective abutment and the core of which is movable by the door relative to the jacket. Transmission members of this type are known, for instance, as Bowden cables or cable releases. It is furthermore known to employ flexible transmission members of this type for tripping circuit breakers in dependence on the existence of a control unit (U.S. Pat. No. 4,041,260) or to block movable switching units against operation depending on the position (British Pat. No. 20 10 015).

The guiding element of the stop body can be designed as a guiding rod which is guided in two parallel cross pieces of the adjustment drive and has recesses associated with the positions of the switchgear provided within the switchboard cell for engagement of a latch which can be operated by the flexible transmission member. By the guidance at both cross pieces, the danger of jamming is avoided and at the same time a mechanical strength is obtained such that an attempt at unathorized manipulation of the stop body can remain unsuccessful.

In this arrangement, the flexible transmission member can be inserted in such a way that the latch forms the abutment for the jacket of the transmission member and that a stationary stop is provided for the end of the core on the latch side, wherein the latch is pretensioned by a spring in the sense of an engagement of the latch with the guide rod. The release of the guide rod is accomplished here by action on the transmission member by the door. As soon as the door is opened, the force ceases and the latch engages the guide rod again under the influence of the spring.

The latch can be designed as a sheet metal latch angled off three times in the same sense, wherein one leg forms the abutment of the jacket of the transmission member; a leg parallel to this leg has an opening corresponding to the jacket of the transmission member; and a bottom piece arranged at right angles to these legs has an elongated hole for guiding the latch at a mounting baffle, as well as a latch post. The opening provided at a distance from the legs forming the abutment forms a protection for the jacket of the transmission member against damage and assures reliable operation of the device.

Near a frame part of the door of the switchboard cell, a plunger serving for action on the core of the transmission member can be supported at a holder, and the plunger and the holder can be designed as opposite each other, forming a wedge-shaped gap. The wedge-shaped gap permits defeating the safety device by means of a tool which has a corresponding wedge angle, so that, for instance, an authorized specialist can carry out work on the switchboard cell which requires opening the door with the circuit breaker in place. By suitable choice of the position of the wedge-shaped gap and its design, provision can be made such that to an unauthorized person, the possibility of defeating the safety device is not recognizable. Manipulation is further made more difficult by the fact that only tools with a certain wedge angle permit the defeating action.

In particular, the plunger can have a wedge inclination which starts at a stop projection and extends in the direction of the door-side end, and a leg of the holder extending parallel to the direction of the displacement of the plunger can be arranged beside the wedge inclination.

The invention will be explained in greater detail in the following detailed description with reference to the drawings, in which:

FIG. 1 shows in a top view onto the bottom plate of the switchboard cell or a pull-out frame for a switchboard cell, an adjustment drive with a stop body preceding a threaded spindle;

FIG. 2 shows details of a latch serving for blocking the stop body shown in FIG. 1, while

FIG. 3 shows the latch according to FIG. 2 in a view rotated 90.degree.; and

FIGS. 4 and 5 show respective views and sections at right angles to each other, of a device located near the frame of the door of the switchboard cell, for transmitting a motion on the latch shown in FIGS. 2 and 3.

On the bottom plate 1 shown in FIG. 1 of a pull-out frame or a switchboard cell intended for receiving a switchgear, for instance, a low-voltage circuit breaker, there is a positioning drive which is designated as a whole with 2 and comprises a stationary cross piece 4 serving as the nut of a threaded spindle 3, as well as a movable cross piece 5 serving as the abutment of the threaded spindle 3. Driver pins 6 which are arranged extending beyond the cross piece 5 on both sides serve for coupling to suitable parts of the switchgear which can therefore be moved by rotating the threaded spindle 3. For operating the threaded spindle 3, a head piece 7 in the form of a hexagon is provided on the front side.

At the rearward end, i.e., the end opposite the head 7, the threaded spindle 3 is provided with a threadless end piece 10, over which an angled-off portion 11 of a follower slider 12 engages, which is guided by means of an elongated hole 13 at a post 14 which is inserted into the top side of the cross piece 4. Through contact of the angled off portion 11 with a shoulder 15 of the threaded spindle 3 formed by the threadless end piece 10 on the one hand and a disc 18 secured by a transfer pin on the other hand, provision is made that the threaded spindle 3 can turn freely and the follower slider 12 can be taken along in both directions in the process.

In the cross pieces 4 and 5, a guide rod 16 is movably guided in a position parallel to the threaded spindle 3. At its rear end, the guide rod 16 is provided with a cross piece 17 which extends parallel to the angled-off portion 11 of the follower slider 12. By a tension spring 21 engaging a cross piece 17 on the one hand and a lateral extension 20 of the follower slider 12 on the other hand, the guide rod 16 is pulled against the angled-off portion 11 of the follower slider 12 or the disc 18, respectively. This arrangement has the purpose to take the guide rod 16 along always in the same sense if the threaded spindle 3 is readjusted, so that the front end of the guide rod 16 is always at the same distance from the movable cross piece 5. At this end a stop 22 is fastened at the guide rod 16 and has an opening or cutout 23 fitting the head 7 of the threaded spindle 3. The guide rod 16 with the stop 22 is thereby movable in the direction of the arrow 24 by a tool until the latter comes into engagement with the head 7. If the tool is removed, the stop 22 returns into the position shown. In order to allow access to the head 7 for the tool, an opening 8 is provided in the door 53 of a switchboard cell.

The guide rod 16 is provided with five recesses which cooperate with a latch designated as a whole with 30 in such a way that a displacement of the guide rod 16 and thereby, an actuation of the threaded spindle 3 in dependence on the position of the door 53 can be prevented. Three of the recesses correspond to the operating position, the test position and the disconnect position, and are designated in this order with 25, 26 and 27. For blocking the actuation also in the intermediate positions of the pull-out frame, a further undesignated recess is provided between these recesses. Although six recesses are accordingly needed for three main positions and three intermediate positions, five recesses are sufficient in the embodiment shown on the basis of an accidental covering of two of the occurring positions.

Details of the latch 30 will now be explained with the aid of FIGS. 2 and 3. In the latter, a magnified portion of the guide rod 16 with the recess 25 is shown. A threaded section 32 at the end of the jacket 33 of the transmission member 31 is inserted into a leg 34 which is parallel to the guide rod 16, of a sheet metal latch 35, where the jacket 33 extends through an opening 36 of a further leg 37, extending parallel to the leg 34, of the sheet metal latch 35. Thereby, the transmission member 33 is braced appropriately against lateral stresses. A bottom part 40 of the sheet metal latch 35 contains an elongated hole 41 for guidance in a sheet metal holder 42 further includes a latch projection 46. Serving as the stationary abutment for an end piece 43 of the core 44 of the transmission member 31 is an angled-off piece 45 of the sheet metal holder 42. A tension spring 47 insures pretensioning the sheet metal latch 35 in the sense of an engagement of the latch projection 46 with the recess 25 of the guide rod 16. Sheet metal holder 42 also includes a leg 45a which guides the lower leg portion 40 of the latch 35 to prevent it from moving upwardly due to the stresses caused by movement of flexible cable jacket 33.

The transmission member 31 is actuated by a door plunger 50 which is arranged in a holder 51 next to a frame part 52 of a door 53 of the switchboard cell. A further end section 32 corresponding to the end section 32 of the jacket 33 in FIG. 2 is fastened in the holder 51, while a plunger 43 rests against the core 44 at a working surface 54 of the door plunger 50. The door plunger 50 is additionally guided in an opening 55 of the frame part 52 and is designed with a rounded front end 56 for action by the door 53.

According to FIGS. 4 and 5, the door plunger 50 rests against the holder 51 with a stop projection 57. Starting from the projection 57, the door plunger 50 has a wedge inclination 60 extending parallel to the displacement direction of the door plunger 50 which is arranged at a small distance from the leg 61 of the holder 51. In this manner, the wedge-shaped gap 62 is formed which is provided for the temporary defeat of the safety device. To this end, FIG. 5 shows the bit 63 of a tool which is introduced between the wedge inclination 60 and the leg 61. Thereby, the door plunger 50 is held in the position shown, whereby the closed condition of the door 53 is simulated and the latch tab 46 is lifted out of the recess 25. (FIG. 2).

In the foregoing specification, the invention has been described with reference to a specific exemplary embodiment thereof. It will, however, be evident that various modifications and changes may be made thereunto without departing from the broader spirit and scope of the invention as set forth in the appended claims. The specification and drawings are, accordingly, to be regarded in an illustrative rather than in a restrictive sense.