GB1268362A - Improvements in or relating to locking means - Google Patents

Abstract

1,268,362. Magnetic fastening device. M. H. JONES. 9 Oct., 1969 [11 Oct., 1968; 3 June, 1969], Nos. 48279/68 and 28012/69. Heading E2A. [Also in Division G4] A locking device comprising a bolt housing 1, a keeper 2 and a magnetised bolt 3 which is slidable in the housing and can be moved by an external magnet between a release position shown in Fig. 1 and a fastening position in which the magnetised bolt 3 engages the housing 1 and the keeper 2, magnetic retention means, cooperating with the magnetised bolt, being provided to retain the bolt in the projecting locking position and in the released position against unwanted movement. In the embodiment shown in Fig. 1 the cylindrical housing 1 and keeper 2 are of low friction synthetic plastics material such as nylon embedded in the door 7 and the frame 9 respectively and fixed therein by screws through embedded flanged plates 10, 11 respectively and thus the whole assembly is concealed when the door is closed. The inner end of the housing 1 is closed by a plate 16 having a ferromagnetic stud 18 as a magnetic retention means to hold the magnetised bolt 3 in the release position and having a skirt 17 of a height such that there is an air gap between the bolt 3 and the stud 18. A similar stud 26 is provided in the keeper 2 to hold the bolt in the fastened position. The magnetised bolt may be sheathed in nylon which has a projecting annular shoulder 19 which engages the shoulder 15 on the housing 1, thus preventing complete removal of the bolt from the housing. A semicircular ferromagnetic screen 27 in the form of sheet or rods may be provided which prevents operation of the magnetised bolt by the external magnet from one side of the door. The bolt 3 may incorporate two magnets 20a, 20b with like poles facing and an air gap between them, thus enabling operation of the bolt with a smaller magnet. The fastening means may have an associated alarm system with one or two switches 28, 29 sensitive to the influence of the locking bolt 3 such as a reed or diaphragm switch or magnetically operated microswitches. In a further embodiment the housing and keeper are fixed by countersunk screws (35, 36) which replace the studs 18, 26, the flanged brackets 10, 11 are dispensed with and the entrances of the housing and keeper are chamfered for easier access of the magnetic bolt. The fastening means may be adapted for surface mounting.