Patent GB-607199-A (GB)
Title: Improvements in and relating to locks
IPC: E05B27/00
Filed: 1944-08-14
Abstract: 607,199. Locks. YALE & TOWNE MANUFACTURING CO. Aug. 14, 1944, No. 15475. Convention date, Sept. 25, 1943. [Class 44] A lock of the type having a key plug rotating in a cylinder and a series of tumblers locking it in the cylinder, has a locking bar slidable in the plug and movable into a position in which a part thereof extends outwardly of the plug into an opening in the cylinder, means being provided tending to press the bar into a position in which the extending part is withdrawn from the cylinder opening, and grooves are'provided in certain of the tumblers into any one of which. the edge of the locking bar can enter, depending on the position of the tumblers in the plug, allowing the bar to move inwardly out of the cylinder opening. The key plug 10 rotates in a bore in the cylinder 11, and bores 12 in the cylinder and plug house springs 15, drivers 16 and tumblers 18. A longitudinal slot 20 formed in the plug and a slot 21 in the cylinder, in alignment in the locked position, accommodate a locking bar 22, of the form shown in Fig. 7. The part 23 of the bar enters the slot 21, while the cam surfaces 24 on the edge of the bar are adapted to enter grooves 25 in the tumblers 18. The bar is urged outwardly by springs 26. Most of the tumblers are formed with grooves 25, but the shortest tumbler used in the series of locks is without grooves, so that it contacts the lowermost cam surface 24 of the locking bar and keeps the bar with the part 23 in the slot 21. The next longer tumbler is formed with one groove, so placed that in the locked condition it accommodates one of the cam surfaces of the bar and allows he latter to move out of the clot 21 to lie entirely within the key plug; the bar will thus not prevent rotation of the latter. The clearance between the tumblers and drivers and their bores is greater than that between the locking bar and the slot 21, therefore very slight rotation of the plug will bring the bar part 23 beyond the edge of the slot 21, after which it will be impossible for the bar to move out of the key plug and out of interlocking engagement with the grooves of all the tumblers, i.e. the locking bar will be held in the position of Fig. 5, rendering it impossible to move the tumblers with a picking tool. The grooves 25 are formed in the tumblers at distances corresponding to the bittings of the keys of the lock series, therefore any key bitted in accordance with the bitting depths for which the lock is designed will position the tumblers so that the grooves 25 lie in alignment with the cam surfaces of the locking bar, and therefore, provided that no short ungrooved tumbler is present, the locking bar will be able to move out of slot 21. This will also be the condition if the tumblers are set by a picking tool. If torque is not applied to the key plug until the tumblers have been moved vertically as by a special key or picking tool, then immediately on application of torque the bar, if engaging the grooves of the tumblers when the plug is rotated, will lock the tumblers against movement. If on the other hand the locking bar is pressed outwardly into the slot 21 by any one of the tumblers through the positioning of the latter by a tool, or by a short (ungrooved) tumbler in the normal locking position, then the bar will make it impossible to apply rotation to the key plug as is necessary to pick the tumblers.