GB636985A - An electric alarm device in connection with safety-chains for doors - Google Patents

Abstract

636,985. Door-chain fastenings. MARTENS, D. G. Dec. 23, 1947, No. 33933. Convention date, May 3, 1939. [Class 44] [Also in Group XXXVIII] In a safety-chain fastening for doors incorporating contacts for operating an electric alarm (see Group XXXVIII) the guiding member 1 is a rectilinear casing the front wall of which has a substantially U-shaped slot adapted to receive the sliding member 5 attached to the chain 2. One branch 4<SP>1</SP> of the U-shaped slot, intended for non-alarm daytime use, extends in the normal manner from the insertion passage 6 towards the gap between the door D and door-frame K, while a second branch for night use is of angular shape extending from the insertion passage 6 in a first portion 4 parallel to the door-gap, i.e., transverse to the chain pull, and thereafter in a short second portion 4<SP>11</SP> parallel to the branch 41 and provided with contacts which operate the alarm when bridged by the member 5. For night use the member 5 is retained in the position shown by a spring plate behind the slot 4<SP>11</SP>, and opening the door tautens the chain causing member 5 to move along the slot 4<SP>11</SP> and operate the contacts. This action is made more sensitive by the provision of a small-angular projection 14 which engages the chain to tauten it for very slight movement of the door D. If the normal daytime use is not required the upper slot 4<SP>1</SP> may be omitted from the guiding member 1 (Fig. 3, not shown).