GB718846A - Improvements in or relating to explosion-proof chambers for electrical apparatus - Google Patents

Abstract

718,846. Switch cases. NAAMLOOZE VENNOOTSCHAP FABRIEK VAN ELECTRISCHE APPARATEN VOORHEEN F. HAZEMEIJER & CO. Sept. 24, 1952 [Sept. 25, 1951; Sept. 16. 1952], No. 23977/52. Class 38(5) [Also in Group XXV] An explosion-proof chamber for electrical apparatus, e.g. a snap-action switch, has a cover which after it has been placed in position on the chamber, can be locked thereto by a sliding movement. In one form, Figs. 1, 3 and 4, the cover 2 is hinged at 33 and has headed pins 3 engageable in keyhole slots 4, 5 in the front of the chamber 1a. A bolt 6, threaded in a box 7 on the cover, has two collars 9, 11 arranged to engage on either side of a projection 10 secured to an upper part 1 of the chamber, so that rotation of the bolt causes up-or-down movement of the cover to engage or disengage pins 3 and slots 5. The switch-operating spindle 12a has a shaped end 14 which may be engaged by a corresponding aperture 15 in a part 35 in the box 7, by axial movement of the part 35 to the left, Fig. 4, after the box has been raised to the Fig. 4, or "locked" position. This latter movement is only permitted when the switch is " off," i.e. when a groove 17 on part 35 is opposite a fixed lug 18. The switch is closed by rotation of part 35 which rotates a bore 13 therein from out of alignment with the bolt 6, which thereby becomes inaccessible so as to prevent removal of the cover whilst the switch is "on". When the switch is " on " the lug 18 rides in a groove 16 in member 35 so as to prevent axial movement of the latter. The pins 3 may be roundheaded, as shown, or may be enlarged only in a direction at right angles to the sliding movement, Fig. 6, and the holes 4 may be formed in a U- shaped frame surrounding and attached to the front of the chamber, Fig. 7, (not shown). Figs. 6 and 8 also show a modification of the switch operating gear wherein the end 14 of the operating spindle 12a is enclosed by a socket 111 having two walls 113, 114, between which can be inserted a cylindrical member 104 when the walls are vertical, i.e. when the switch is " off ". Member 104 is carried by a part 101 pivoted to the cover 2 at 116 and has grooves 106, 105 co-operating with a pin 115 on the wall 114 similarly to lug 18 and grooves 17, 16. Member 104 can only be withdrawn axially from the spindle 12a when a hole 107 therein co-incides with a pin 108 on part 101.