GB2064637A

GB2064637A - Cylinder Lock

Info

Publication number: GB2064637A
Application number: GB8036758A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-11-17
Filing date: 1980-11-17
Publication date: 1981-06-17
Also published as: GB2064637B

Abstract

A key-operated locking device includes a cylinder 10 rotatable within a housing 11 upon insertion of the correct key 12. The cylinder 10 contains a pack of moulded plastic tumblers 13 engaged at their ends by spring-loaded bars 20 and 21 contained in longitudinal recesses 18 and 19 in the housing 11. <IMAGE>

Description

SPECIFICATION Locking Devices This invention relates to locking devices of the kind comprising a cylinder rotatable within a housing, the cylinder containing a plurality of tumblers which are displaceable on insertion of a key into the c'ylinder in a direction at right angles to the axis of rotation of the cylinder within the housing such that, when the correct key is inserted, the tumblers are moved into positions in which they do not project from the cylinder which is accordingly freely rotatable within the housing whereas, when any other key is inserted, one or more tumblers project from the cylinder and rotation of the cylinder is prevented.

In conventional locking devices of the above kind, the tumblers are in the form of discs or plates and are individually spring-loaded to project from the cylinder. Disadvantages of such devices are that they can be picked and that they can be forced, either by inserting a tool in the key slot and applying a torque or by extracting the cylinder axially from the housing.

It is an object of the invention to provide a locking device of the kind referred to which is resistant to picking and less susceptible to forcing than existing devices.

According to the invention, there is provided a locking device of the above kind in which the housing has a longitudinal recess containing a bar which is spring-loaded into engagement with the ends of the tumblers such that, when a correct key is inserted, the bar does not, project radially inwardly beyond the recess and the ends of the -tumblers do not project radially outwardly beyond the cylinders whereas, when an incorrect key is inserted, either the bar projects radially inwardly or the ends of the tumbler projects radially outwardly.

The housing preferably has two diametrically opposed longitudinal recesses each containing a bar so that one bar engaged one end of each tumbler and the other bar engaged the other end of each tumbler with the arrangement such that when an incorrect key is inserted at least one of the bars projects radially inwardly of its recess to prevent rotation of the cylinder.

The spring means acting on the bars may take the form of three helical springs acting on one bar and a single helical spring acting on the other bar, with the three springs unbalanced to make manipulation thereof more difficult.

The tumblers may be formed as plastics mouldings, for example from an acetal resin, with the different tumblers moulded from slightly different coloured plastic materials to facilitate control of assembly.

The surface of each tumbler engaged by the edge of an inserted key may be of ramped form and the tumblers may be of somewhat stepped form so that, when assembled in a pack, they serve to guide one another during relative sliding movement upon key insertion.

The invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a longitudinal sectional view of a first form af locking device showing the effect of insertion of a correct key, Figure 2 is a transverse sectional view of the device of Figure 1, along the line 2-2 of Figure 1, Figure 3 is a longitudinal sectional view of the locking device of Figure 1 showing the effect of insertion of an incorrect key, Figure 4 is a transverse sectional view of the device of Figure 3, along the line 4-4 of Figure 3, Figure 5 is a longitudinal sectional view of the device of Figure 1 prior to insertion of a key, Figure 6 is a plan view of the cylinder of the device of Figure 1 showing the tumblers sectioned, Figure 7 is a longitudiual sectional view of a first alternative form of device, Figure 8 is a transverse sectional view of the device of Figure 7, Figure 9 is a longitudiual sectional view of a further alternative form of device, and Figure 10 is a transverse sectional view of the device of Figure 9.

Referring first to the embodiment shown in Figure 1 to 6, the locking device includes a rotatable cylinder 10 contained within an outer housing 11 and rotatable relative thereto upon the insertion of a correct key 12. The cylinder 10 can be formed as a casting from a zinc-based alloy and has a rectangular cross-section through aperture in which a pack of seven moulded tumblers 13 is located. The simple form of the aperture simplifies manufacture of the mould tools required to produce the cylinder 10 and facilitates the production of a flash-free casting using relatively simple equipment. A considerable manufacturing economy as compared to conventional disc tumbler devices is thus obtained.

The tumblers 13 are formed as mouldings, either from a synthetic plastics material such as an acetal resin or nylon or from a zinc based alloy.

Each tumbler 13 has the configuration shown in Figure 2, 4 and 6 and is generally rectangular form with parallel side walls 14 and 1 5 bounding a through aperture with the walls 14 and 1 5 joined at one end by a fixed width bridge 16 and joined at their other ends by a variable thickness bridge 1 7, the different thicknesses of the bridge 1 7 distinguishing the tumblers 1 3 from one another. As shown there are four different thicknesses, providing four step heights corresponding to four different cuts of the key 12.

The side edges of each tumbler 1 3 are stepped as shown in Figure 6 so that each tumbler 1 3 acts as a guide for the adjacent two tumblers during sliding movement thereof on insertion of a key.

The stepped form of each tumbler also acts as a strengthening means, as well as facilitating assembly of the tumblers to form a pack which can be assembled and then inserted as a pack within the aperture in the cylinder 10.

The surface of the bridge 17 engaged by the cut edge of the Key 12 is of ramped form as shown. This has two advantages. First, it facilitates key insertion and ensures that, when the Key 12 is inserted into the cylinder 10, a smooth action is obtained as the tumblers 1 3 are engaged in sequence by the tip of the key.

Second, it allows a greater spacing to be obtained between the different tumbler heights. Thus, for a cylinder diameter of 12.7mm, and four key cuts, a step increment of 0.8mm can be utilised. This increase in increment permits a higher degree of security to be obtained for the same manufacturing tolerance levels as existing devices and ensures that the device is resistant to reduction in security through wear.

In the particular arrangements shown in Figures 2 and 4, the corners of the tumblers 1 3 adjacent bridges 1 6 are rebated, the purpose of the rebates being to render "picking" of the device more difficult. The device has, however, as explained below, an inherent resistance to picking arising from the method of spring-loading the tumblers.

The outer housing 11 is formed with diametrically opposed longitudinal recesses 1 8 and 1 9 each of which contains an elongated locking bar 20, 21. Locking bar 20 is acted upon by three springs 22, 23 and 24 and locking bar 21 is acted upon by a single spring 25. The springs 22, 23, 24 and 25 are helical springs and each is located in a pocket in the associated locking bar 20, 21. The combined ratings of the three springs 22, 23 and 24 are greater than the rating of spring 25 such that prior to insertion of a key (i.e.

the condition shown in Figure 5), locking bar 21 is pressed against the base of the recess 19. In this condition, it is to be noted that the edges of the thickest bridges 1 7 extend over the centre-line of the cylinder but, because of the ramp form of these edges, the tumblers 13 are still urged radially outwardly by the tip of the key.

The three springs 22, 23 and 24, acting on bar 20 are unbalanced so that if, for example, an attempt is made to move the bar 20 outwardly to hold it in an inoperative position, the bar 20 will tend to tilt. The bars 20 and 21 can be formed as mouldings from a synthetic plastics material such as nylln or a polyacetal resin or as castings from a zinc-based alloy and when the correct key is inserted, the bars 20 and 21 are completely located in the respective recesses 1 8 and 1 9 and the cylinder 10 can rotate freely with the curvate outer edges of the tumblers 13 sliding relative to the inwardly facing curvate surfaces of the bars 20 and 21.

When, however, one or more of the cuts on the Key 12 do not correspond to the complementary steps afforded by the different bridge thicknesses 17, the bars 20 and 21 will move into positions corresponding to those shown in Figure 3. In this figure, the third cut from the tip of the key is incorrect, as also is the sixth cut. The incorrect cut will cause tilting of bar 20 and as the bar 20 tilts, all the tumblers 13 will move to follow the surface of the bar 20 and bar 21 will move into a position in which it projects from its recess 21 to prevent rotation of the cylinder 10. The bars 20 and 21 are so arranged that, when any key other than the correct key is inserted, one or both bars project from their respective recesses to prevent rotation of the cylinder 10.If the tumblers 1 3 are all lifted against the action of springs 22 23 and 24 to their fullest extent to ensure that bar 20 is held within its recess 18, bar 21 will move radially inwardly out of its recess 1 9 to prevent rotation df the cylinder.

In the "picking" of a conventional disc tumbler device, the tumblers are moved individually and segmentially against their spring-loading into their release positions. Such a method of picking is not possible with the spring-loading arrangement of the present invention since the tumblers will tend to "float" or slide uncontrollably when a picking action is attempted. The rebated corners of the tumblers also makes it more difficult for a "picker" to establish the release position of each tumbler 13.

The inner end portion of the body 10 is provided with means (not shown) whereby it can be attached to a mechanism to be operated by the locking device and the outer end portion 26 of the body 10 is of increased diameter to provide a flange which bears against a shoulder 27 to position the body 10 axially relative to the housing 11. The flange and shoulder 27 arrangement also serves as a bearing enabling the body 10 to rotate freely relative to the housing.

Immediately inwardly of the flange 26, the body 10 is provided with internal shoulders 28 which cooperate with the shoulders on the key to limit the depth of key insertion. The outer end portion 26 of the body has a key slot of a configuration complementary to that of the key so that only keys of the required cross-section can enter the body for engagement with the tumblers 13.

Turning next to Figures 7 and 8, this shows an arrangement in which the body 10, housing 11 and tumblers 13 are as in the embodiment of Figures 1 to 6 and the same reference numerals are used to indicate corresponding parts of the locking device. In this embodiment however, the bars 20 and 21 acted on by springs 22,23,24 and 25 are replaced by moulded plastics bars 29 and 30. Bar 29 includes a main body portion which overlies the series of tumblers 1 3 and, in the position occupied prior to key insertion bears on parts 31 and 32 of the housing 11, projecting out of its recess 1 8 to prevent rotation of the cylinder 10 within the housing 11. At the ends of the main body portion of the bar 29 there are integral leaf spring elements 33 which bear against the base of the recess 18 to bias the body portion of the bar 29 against the row of tumblers 13.

The bar 30 acting on the other ends of the tumblers 13 also has a main body portion with integral leaf spring elements 34 at the ends of the main body portion and bearing against the base of the recess 1 9. The rating of the spring means afforded by bar 30 and its spring elements 34 is less than the rating of the spring means afforded by bar 29 and its spring elements 33 so that the bars 29 and 30 occupy the positions shown. This may be achieved in the manner depicted in Figure 8, i.e. by providing the bar 30 and its leaf elements 34 with a central slot. It may alternatively be achieved by forming the bar 30 and its leaf elements 34 from material which is of less thickness than the material from which bar 29 and its leaf elements 33 are formed. In addition, the leaf elements 33 at the two ends of bar 29 may be different so that bar 29 is not balanced.

Turning next to Figures 9 and 10, these show an embodiment which differs only from that shown in Figures 1 to 6 in that the tumblers are located in individual slots in the cylinder. The tumblers, indicated as 35, are thus of less thickness than the tumblers 13, and are open at their lower ends.

The modes of operation and ristance to picking and forcing of the embodiments of Figures 7 and 8, and Figures 9 and 10 are as described above in relation to Figures 1 to 6.

Claims

1. A locking device of the kind comprising a cylinder rotatable within a housing, the cylinder containing a plurality of tumblers and the housing having a longitudinal recess containing a bar which is spring-loaded into the ends of the tumblers such that, when a correct key is inserted, the bar does not project radially inwardly beyond the recess and the ends of the tumblers do not project radially outwardly beyond the cylinder whereas, when an incorrect key is inserted, either the bar projects radially inwardly or the ends of the tumbler project radially outwardly.

2. A locking device according to claim 1, wherein the housing has two opposed longitudinal recesses each containing a bar so that one bar engages one end of each tumber and the other bar engages the other end of each tumbler, with the arrangement such that when an incorrect key is inserted at least one of the bars projects radially inwardly of its recess to prevent rotation of the-cylinder.

3. A locking device according to claim 2, wherein the spring means acting on the bars comprises three helical springs acting on one bar and a single helical spring acting on the other bar.

4. A locking device according to claim 3, wherein the three springs are unbalanced to make manipulation of the tumblers more difficult.

5. A locking device according to claim 2, wherein each of the bars is of channel form in cross-section with the inwardly facing surface of the base of the channel of arcuate form to allow free rotation of the cylinder and tumblers when the correct key is inserted.

6. A locking device according to claim 1, wherein the tumblers are formed as plastic mouldings and are assembled in a pack.

7. A locking device according to claim 6, wherein one end of the pack of tumblers is acted upon by one spring mechanism and the other end of the pack is acted upon by another spring mechanism of different rating.

8. A locking device according to claim 6, wherein the surface of each tumbler engaged by the edge of an inserted key is of ramped form.

9. A locking device according to claim 8, wherein each tumbler is of stepped form in crosssection so that adjacent tumblers act to guide one another during relative sliding movement.

10. A locking device comprising a cylinder containing a pack of moulded plastic tumblers engaged at their ends by spring loaded bars, substantially as hereinbefore described with reference to and as shown in the accompanying drawings.