GB449029A - Improvements in and relating to cylinder locks - Google Patents

Abstract

449,029. Revolving barrel locks. BAXTER, F. W., 15, Hanover Park, Peckham, London. Dec. 18, 1934, No. 36350. [Class 44] A pin tumbler cylinder lock has one or more displaceable segments on the plug normally held in alignment by a driver or tumbler and capable of movement transversely to the axis thereof limited only by the driver or tumbler and the cylinder in which the plug is housed, so that when subjected to an angular torque a ledge is formed to prevent continued movement of the tumblers into the unlocking position by a picking instrument. Alternatively or in addition, grooves may be formed on the tumblers or drivers to engage corresponding grooves in the bores of the cylinder and plug. Fig. 5 shows a lock in which the plug 1 has a segmental portion 8 and the cylinder bore has two recesses 12 so that when a torque is applied to the cylinder a ledge 11 is formed to prevent the tumbler 5 from being raised to its unlocking position, or should the picker succeed in doing this the segment tends to become displaced and engage one of the notches 12 as the cylinder is turned. In addition the driver 3 is tapered and the opening in the segment 8 flared out to prevent the formation of a ledge on which the driver can rest in the unlocking position. Grooves are formed as shown in the tumbler and the driver bore so that, should a torque be applied to the cylinder when the tumbler is raised the tumbler grooves will engage those in the driver bore to prevent the return of the tumbler. Grooves may also be formed on the drivers and in the tumbler bores. A segment 8 may be provided at each bore or only on some of them, or one segment may extend over all or several of such bores. The segments 8 may have concave or convex undersurfaces instead of flat and may be split into upper and lower parts as shown for a convex surfaced segment in Fig. 10. Fig 12 shows a segment 8 resting upon a cylindrical plug of smaller diameter than the cylinder. The lower ends of the bores in the segments may be opened out so that the tumblers do not normally engage them. The grooves in the tumblers or drivers may be screw-threads, or single grooves as shown in Fig. 17 where a groove 32 in the driver co-operates with a groove 19 in the plug which also has its bore enlarged at its upper end as shown at 18. Fig. 19 shows a lock in which the tumblers normally rest on the drivers by gravity. A segment 22 in this case is provided in a recess in the cylinder. Fig. 20 shows an additional safeguard against picking which comprises a lever 23 pivoted in the plug, and normally engaging a groove 26 in the cylinder. The lever becomes displaced as shown by inserting the proper key. To prevent picking by cutting away the flange of the plug and inserting thin feelers between the plug and cylinder, spring rings 28, Fig. 22, are sprung into grooves 29, 30 in the plug and cylinder.