Patent GB-664275-A (GB)
Title: Improvements relating to box-like enclosures with removable covers
IPC: H01H9/04
Filed: 1949-03-21
Abstract: 664,275. Switch covers and cases. SIEMENS-SCHUCKERT (GREAT BRITAIN), Ltd., FLAX, S., and DIXON, B. J. March 21, 1949. No. 7677/49. Class 38 (v). [Also in Groups XVII and XXV] A box-like enclosure, particularly a flameproof enclosure for electrical equipment, comprises a body and a cover or covers fastenable to the body by wedge means on one of the parts engaging behind a co-operating wedging surface or surfaces on the other part, the wedging action being the result of movement of the two parts relative to each other in, or substantially in, the plane of the joint therebetween, said movement being produced by a screw acting directly on the cover and with its axis parallel to the direction of movement. The invention is shown applied a box 1 for electrical equipment having a supplementary chamber 2 for an isolator switch. The front of the sides of the box 1 and the inner faces of flanges 6, 7 on the cover B therefor each carry a row of. wedges 9, 8 respectively. The line of each row is slightly inclined to the plane of the joint so that each row forms a single interrupted wedge. The cover is attached in two stages, first a straight-forward movement causing the wedges 8 to pass between the gaps in the wedges 9 followed by a downward sliding movement to cause interengagement of the wedges. The latter movement is effected by a screw 10, Fig. 7, working in a nut 13 fixed to the box, a flange 12 on the screw sliding into a recess on the cover during the first movement of the latter. In the fastened position shown, the head 11 of the screw is received in a shrouding recess 15 in the nut and can only be actuated by a special spanner, to prevent unauthorised opening of the enclosure. Interlocking mechanism between the switch and the cover is also provided comprising a plunger 21 spring- pressed into engagement with a cam 19 on the shaft 18 of the switch operating handle 3. When the switch is "on" as shown, the plunger projects into recess 15 and prevents access to the screw 10. Conversely, when the screw 10 is withdrawn, outward movement of the plunger and consequently operation of the switch to the "on" position is prevented thereby. An alternative interlocking mechanism is shown in Fig. 12. In the withdrawn position, the head 11 of the screw 10 enters a diametral passageway 43 in the boss 42 of the switch operating handle, said passageway being sufficiently large to pass the special spanner. Actuation of the switch is thus prevented. With the cover secured in position, however, the head 11 is received in the nut as before and the handle 3 is freed. When the switch is "on", head 11 is inaccessible as the passageway is then out of alignment therewith. A cover c (Fig. 4) for the chamber 2, has wedges 27 engaging wedges 28 on the chamber as in the case of cover B. A screw 31 is provided for moving the cover to its final position, the screw working in a nut 32 on the chamber wall and having a pair of flanges 34, 35 between which the wall 38 of a recess in the front of the cover engages. A flange 41 on the wall 38 shrouds the head 40 of the screw to prevent unauthorised manipulation thereof.