Patent GB-874892-A (GB)
Title: Improvements in explosion proof enclosures, more particularly for electric mine equipment
IPC: E21F9/00
Filed: 1958-04-15
Abstract: 874,892. Switch cases. HOUILLERES DU BASSIN DU NORD ET DU PAS-DE-CALAIS. April 15, 1958 [April 24, 1957], No. 12021/58. Class 38 (5). [Also in Group XXI] An explosion-proof enclosure for electrical equipment used in mines comprises at least one door for access and inspection which is provided on at least one of its sides, with a flat strip extending along the edge of a door and supported on the side by a beam element of which the depth is at least one-third of its length, said flat strip providing at the door closure one of a pair of closely - spaced surfaces through which gases must be expelled in the event of an explosion. In Fig. 1 a quick access compartment for electrical apparatus 15 is comprised by a door in the form of deep shell 14 the side walls 16 of which constitute webs supporting a flange 17 which in the closed position of the door is spaced a predetermined distance from a wall 4 of a slowaccess compartment 1. The slow-access compartment has walls of such thickness that it can withstand an inner explosion. The cover 14 is secured in the closed position by catch-members 18, 19, Fig. 2, on the wall 4 engaging over one side of the flange 17. To open the cover 14 it is first released from the catch members 18, 19 by a sliding movement in the direction of the axis of a slidable hinge-pin 11 to which it is secured by lugs 13, and it is then upwardly hinged about the axis of the hinge pin 11. The slow access compartment 1 carries a rotatable switch-actuating knob 7 having an arcuate peripheral portion which engages a notch 20 in the hinge-pin 11 when the switch and door 14 are closed and a flat peripheral portion 9 which clears the notch 20 when the switch is open-circuited to permit the door 14 to be opened and to prevent remaking of the switch until the door 14 is again closed. In a modified form of interlock between a rotatable switch-actuating knob 7a, Fig. 3, on the side of the compartment 1, a slidable bolt 22 is provided with pointed ends 23, 24 engageable, respectively, in a notch in a collar 25 carried by the hinge-pin 11 and in a notch 9a in knob 7a. In a modification, Fig. 5 (not shown), the switch in the compartment 1 is replaced by an explosion-proof connector socket which receives a plug which is interlocked with the door 14 by a slidable bolt operating in a manner analogous to the operation of the bolt 22 in Fig. 3. In another modification having a plug connector (not shown), the cover 14c, Fig. 7, is arranged to swing horizontally about a vertically slidable and rotatable hinge-pin 11c provided at its upper end with a boss 34 carrying an operating lever 35 and having a helical groove 37, the upper end of which is provided with a deeper portion, Fig. 8 (not shown), which co-operates with the end of a slidable bolt 22 interlocking the cover 14c with the plug in a manner analogous to the notch 24, Fig. 3. To open the cover 14c the boss 34 is rotated by pulling on the lever 35 so that the hinge-pin 11c and cover 14c are lifted by the action of the helical groove on the interlocking bolt to release lugs 45 on the cover 14c from retaining-catches 44 on the compartment 1c, so permitting the cover to open. In the closed position of the cover 14c the lever 35 engages a lug 41 of a catch 42 fast with the cover 14c and extends under a pair of lugs 43 on the compartment 1c.