GB2441400A

GB2441400A - Cylinder lock with restrained driver pin

Info

Publication number: GB2441400A
Application number: GB0712293A
Authority: GB
Inventors: Bruce Patrick Mccarthy
Original assignee: Assa Abloy Ltd
Current assignee: Assa Abloy Ltd
Priority date: 2006-09-01
Filing date: 2007-06-25
Publication date: 2008-03-05
Also published as: IE20070611A1; GB0712293D0; GB0617289D0

Abstract

A cylinder lock assembly comprises a plug 1 with keyway 3 rotatably mounted in a cylinder 2. The lock having a plurality of axially spaced tumbler pins 10 slidably mounted in the plug and a plurality of axially spaced driver pins 11 slidably mounted at least partially in the plug extending transverse to the longitudinal axis of the plug 1 from the periphery of the plug to the keyway 3. The driver pins 11 are biased towards the tumbler pins 10 and include a restrained driver pin 11A that is engagable with a portion of the cylinder 2 or plug 1 to limited inward movement of the restrained driver pin to an innermost position in which the pin projects into the aligned tumbler pin passageway 8. The restrained driver pin 11A may be engagable with a projecting portion such as a shoulder formed by a step change in the cross-section of the cylinder 2 or plug 3.

Description

-1-2441400 Cylinder assembly This invention relates to a cylinder

assembly for a lock.

A standard cylinder assembly for a cylinder lock comprises a cylinder in which a plug is rotatably housed.

The plug has a keyway extending along the axis of the cylinder and plug. Both the cylinder and plug have radially extending passageways which in one position of the plug are aligned. Tumbler pins are mounted in the aligned passageways and cooperate at their outer ends with driver pins that are spring biased radially inwardly. Prior to insertion of a key, tumbler pins extend across the interface of the plug and cylinder to prevent the plug being rotated relative to the cylinder, but when the correct key is inserted the tumbler pins are moved radially outwardly by such a distance that the interfaces of the tumbler pins and driver pins coincide with the interface of the plug and cylinder and the plug can then be rotated relative to the cylinder.

The security of locks is always an issue and the present invention is concerned with making a lock more secure in one particular respect. A known way to attack a cylinder assembly is "bumping". The principle behind bumping is the transfer of kinetic energy between the pin and driver which, in a standard cylinder assembly, are held in contact by the springs. By applying a shock load to a tumbler pin it is possible to separate the tumbler pin and driver (like the balls on a Newton's Cradle) to create a false split line. This shock load is applied by using a key which has all the notches cut slightly deeper than the standard deepest cut. This key also has part of the "ear" removed and replaced by a compressible material such as rubber to allow the key to spring back slightly. To bump the cylinder assembly the key is inserted into the plug and a small turning load is applied, then the end of the key is hit sharply with a small hammer or screwdriver until the plug turns. In the hands of a skilled practitioner it will be possible to operate the cylinder assembly.

The present invention seeks to make a method for attack of this kind more difficult.

According to the invention there is provided a cylinder assembly for a lock, the assembly comprising a plug of generally circular cylindrical shape and including a keyway extending along the longitudinal axis of the body of the plug and open at a front end of the plug to allow insertion of a key, the plug including a plurality of axially spaced tumbler pin passageways extending transverse to the longitudinal axis of the plug from the periphery of the plug to the keyway, a cylinder including a generally cylindrical opening in which the plug is rotatably mounted, the cylinder including a plurality of axially spaced driver pin passageways extending outwardly from the generally cylindrical opening, the driver pin passageways being aligned with the tumbler pin passageways in one rotational position of the plug, a plurality of tumbler pins slidably mounted in respective tumbler pin passageways in the plug, and a plurality of driver pins slidably mounted at least partly in respective driver pin passageways in the plug, the driver pins being biased towards the tumbler pins, wherein the driver pins include a restrained driver pin that is engageable with a portion of the cylinder or the plug to limit inward movement of the restrained driver pin to an innermost position in which the pin projects into the aligned tumbler pin passageway.

By limiting movement of the driver pin one of two arrangements can be obtained. On the one hand the cylinder assembly may be, for example, of the Euro-profile or oval-profile type, so that, in normal use, the restrained driver pin is positioned in a driver pin passageway that extends downwardly from below the plug. In that case upward movement of the restrained driver pin is limited and the corresponding tumbler pin will drop down further than it otherwise would until it rests on the top of the driver pin. That will then prevent the key making contact with that tumbler pin if an attempt is made to bump the cylinder assembly, and the tumbler pin will remain in its position spanning the drive pin passageway and the tumbler pin passageway. On the other hand the cylinder assembly may be, for example, of the rim, screw-in or Scandinavian type, so that in normal use, the restrained driver pin is positioned in a driver pin passageway that extends upwardly from above the plug. In that case downward movement of the restrained driver pin is limited, the corresponding tumbler pin drops to its usual position under gravity and a gap is therefore created between the restrained driver pin and its corresponding tumbler pin. An attempt to bump the cylinder assembly will then be prevented by the gap.

Whilst the driver elements and the tumbler elements are referred to above as "pins" and are preferably of generally circular cross-section, it should be understood that other shapes of element may also be employed and that the shape is not directly relevant to the functioning of the invention. For example, the pins could be of generally rectangular cross-section.

Also, it should be understood that the "cylinder" is not usually of circular cross-section but will commonly be of the general shape shown in the drawings of this specification, and may be of any other shape. Usually the cylinder is of generally constant cross-section along its length, but that is also not a necessary feature.

There are a variety of ways in which the inward movement of the driver pin may be limited. In some arrangements the restrained driver pin is provided with a projecting portion that is engageable with a portion of the cylinder or plug. The projecting portion of the restrained driver pin is preferably provided by a flange on the pin.

In the case where the pin is of generally circular cross-section, the flange is preferably also of generally circular cross-section projecting on all sides of the pin.

That avoids any need to control the orientation of the pin and ensures that the pin can be effectively restrained.

I

The flange is preferably provided at the outer end of the pin.

Whether or not the restrained driver pin has a projecting portion, the portion of the cylinder or plug engaged by the driver pin may have a projecting portion with which the driver pin is engageable. The projecting portion of the cylinder or plug that is engageable by the restrained driver pin preferably comprises a shoulder formed by a step change in the cross-section of the driver pin passageway or tumbler pin passageway for the restrained driver pin. Again the shoulder is preferably provided around the whole passageway arid, in a preferred case where the passageway is of circular cross-section, is concentric with the passageway, whereby the passageway has an inner portion of a given circular cross-section and an outer portion, concentric with the inner portion, of a larger circular cross-section. The flange of the restrained driver pin, when one is provided, may be slidably mounted in the outer portion of the driver pine passageway and the other part of the pin may be slidably mounted in the inner portion of the driver pin passageway.

The driver pins are preferably resiliently biased towards the tumbler pins, for example by compression springs, which may be positioned in the driver pin passageways on the outer side of the driver pins and sandwiched between the driver pins and end stops that close off the outer ends of the driver pin passageways.

The restrained driver pin may be positioned to the rear of the other driver pins, that is furthest from the entry point for the key. It is then in the least accessible location. More than one restrained driver pin may be provided, if desired.

By way of example, certain embodiments of the invention will now be described with reference to the accompanying drawings, of which: Fig. 1 is a sectional view of a first form of cylinder assembly embodying the invention, Fig. 2 is a sectional view along the lines Il-Il in Fig. 1, and Fig. 3 is a sectional view of part of a second form of cylinder assembly embodying the invention.

Figs. 1 and 2 show a cylinder assembly for a cylinder lock which is in many respects of conventional design and conventional parts of the assembly will first be described.

Thus the assembly generally comprises a plug 1 rotatably mounted in a cylinder 2. The plug 1 is of generally circular cylindrical shape and includes a keyway 3 extending along the longitudinal axis of the body of the plug. The keyway 3 is open at its front end 4 to allow a key to be inserted into the keyway from that end. At the rear end of the plug 1, a cam actuator 5 is provided for actuating a cylinder lock (not shown) with which the cylinder assembly is used.

The cylinder 2 is provided with a circular cylindrical cavity 6 in which the plug 1 is rotatably received and that cavity extends radially into an opening 7 in the region of the cam actuator 5 to allow space for rotation of the actuator.

The plug 1 is provided with a plurality of tumbler pin passageways 8 which extend radially outwardly from the keyway 3 to the periphery of the plug 1 and are spaced along the length of the plug and disposed in a common radial plane. The cylinder 2 is provided with corresponding driver pin passageways 9 which extend radially outwardly from the cavity 6 to the periphery of the cylinder 2 and are spaced along the length of the plug and disposed in a common radial plane. The passageways 9 and the passageways 8 are aligned in one orientation of the plug (the one shown in Figs. 1 and 2) and in the example shown there are six passageways in each set, all of circular cross-section.

A tumbler pin 10 is slidably mounted in each of the tumbler pin passageways 8 and a driver pin 11 is slidably mounted in each of the driver pin passageways 9. Each driver pin passageway 9 is closed at its outer end by an end stop 12 and a compression spring 13 is mounted in each driver pin passageway 9 between the end stop 12 and the driver pin 11. In Fig. 1, the springs 13 are not shown (although they are present) and in Fig. 2 the spring 13 is indicated schematically.

The assembly as described above is of a kind known per se. In accordance with the embodiment of the invention shown in Figs. 1 and 2, the driver pin 9A at the rear end of the row of passageways is formed with a shoulder 14 as a result of a step change in diameter of the passageway, defining a relatively narrow portion of passageway at the inner end. The driver pin hA mounted in the passageway 9A is formed with a circular flange 15 at its outer end. The flange is sized to be accommodated in the wider portion of the passageway 9A but cannot pass the shoulder 14 formed in the passageway. Thus, as shown in Figs. 1 and 2, inward movement of the driver pin hA is restricted to the limit position shown in Figs. 1 and 2.

In the condition of the assembly shown in the drawings, before insertion of a key, all the tumbler pins 10 are in their lowermost positions. For all the tumbler pins except the tumbler pin 1OA at the rear of the row of pins, the pins are pressed into this position by the driver pins 11 which in turn are biased by the springs 13.

In the case of the tumbler pin 1OA, it is simply gravity that causes the pin to adopt its lowermost position because the driver pin 11. A is held by the shoulder 14. Consequen-tly, there is a gap between the tumbler pin 1OA and the restrained driver pin hA.

If an attempt is made to bump the cylinder assembly by the technique described above, then because of the gap between the tumbler pin 1OA and the restrained driver pin hA, the driver pin hA will not be displaced and will therefore continue to hold the plug 1 rotatably fixed in the cylinder 2. Thus the arrangement shown in the drawings provides an obstruction to bumping. I'

In the embodiment just described the driver pin passageways are above the plug 1 and as a result of gravity a space is created between the driver pin hA and the tumbler pin 1OA. In an alternative embodiment (not illustrated), the driver pin passageways are below the plug 1. In that case, the parts will assume the same positions as shown in the drawings (but inverted) except that the tumbler pin 1OA will drop under gravity to a position in contact with the driver pin hA. In that position the tumbler pin 1OA will be spaced from the keyway and therefore will not be bumped by a key inserted into the keyway for that purpose. Thus, in the alternative embodiment a line of contact from the key through the tumbler pin to the driver pin is again avoided but in this case by means of a lack of contact of the key with the tumbler pin, whereas in the illustrated embodiment there is a lack of contact of the tumbler pin and the driver pin.

Fig. 3 shows a modified arrangement to that shown in Figs. 1 and 2. In the modification according to Fig. 3, where corresponding parts are designated by the same reference numerals as in Figs. 1 and 2, the driver pin 9A is limited in its inward movement by engagement of the inner end of the pin 9A with a shoulder 14 formed in the tumbler pin passageway 8A. Thus the inward movement of the driver pin 9A is again restricted as in Figs. 1 and 2, but in this case by engagement of the driver pin 9A with a part of its associated passageway BA in the plug 1. As in the embodiment of Figs. 1 and 2, the driver pin passageways 9 -10 -may be below the plug 1 rather than above them as shown in Fig. 3.

In the preferred embodiments described above gravity is relied upon for positioning of the tumbler pin 1OA, but it will be understood that the invention could also be employed in an assembly in which the tumbler pin passageways were horizontal because the position taken up by the tumbler pin 1OA is not critical to operation of the assembly. Because the driver pin hA is held at a position further from the keyway than the length of the tumbler pin 1OA, there will be at least one gap to one side of the other of the tumbler pin 1OA and bumping will therefore be avoided. The tumbler pin 1OA and the driver pin hA can, however, both still operate in the same way as the other pins: upon full insertion of the correct key, the tumbler pin 1OA is moved outwardly to a position in which it is in contact with the driver pin hA and the driver pin hA is lifted off the shoulder 14 against the bias of the spring 13. At that stage the interface of the driver pin hA and the tumbler pin 1OA is aligned with the interface of the plug 1 and the cylinder 2 so that the pins no longer obstruct rotation of the plug relative to the cylinder.

Claims

Claims: 1. A cylinder assembly for a lock, the assembly comprising a

plug of generally circular cylindrical shape and including a keyway extending along the longitudinal axis of the body of the plug and open at a front end of the plug to allow insertion of a key, the plug including a plurality of axially spaced tumbler pin passageways extending transverse to the longitudinal axis of the plug from the periphery of the plug to the keyway, a cylinder including a generally cylindrical opening in which the plug is rotatably mounted, the cylinder including a plurality of axially spaced driver pin passageways extending outwardly from the generally cylindrical opening, the driver pin passageways being aligned with the tumbler pin passageways in one rotational position of the plug, a plurality of tumbler pins slidably mounted in respective tumbler pin passageways in the plug, and a plurality of driver pins slidably mounted at least partly in respective driver pin passageways in the plug, the driver pins being biased towards the tumbler pins, wherein the driver pins include a restrained driver pin that is engageable with a portion of the cylinder or the plug to limit inward movement of the restrained driver pin to an innermost position in which the pin projects into the aligned tumbler pin passageway.

2. An assembly according to claim 1, in which, in normal use, the restrained driver pin is positioned in a driver pin passageway that extends downwardly from below the plug.

-12 - 3. An assembly according to claim 1, in which, in normal use, the restrained driver pin is positioned in a driver pin passageway that extends upwardly from above the plug.

4. An assembly according to any preceding claim, in which the tumbler pins and the driver pins are of generally circular cross-section.

5. An assembly according to any preceding claim, in which the restrained driver pin is provided with a projecting portion that is engageable with a portion of the cylinder.

6. An assembly according to any of claims 1 to 4, in which the restrained driver pin is provided with a projecting portion that is engageable with a portion of the plug.

7. An assembly according to claim 5 or 6, in which the projecting portion of the restrained driver pin comprises a flange on the pin.

8. An assembly according to claim 7, in which the flange is provided at the outer end of the pin.

9. An assembly according to any preceding claim, in which the restrained driver pin is engageable with a projecting portion of the cylinder.

10. An assembly according to any of claims 1 to 8, in which the restrained driver pin is engageable with a projecting portion of the plug.

11. An assembly according to claim 9 or 10, in which the projecting portion of the cylinder or plug that is engageable by the restrained driver pin comprises a shoulder formed by a step change in the cross-section of -13 -the corresponding driver pin passageway or tumbler pin passageway.

12. An assembly according to any preceding claim, in which the driver pins are biased towards the tumbler pins by respective compression springs in the driver pin passageways.

13. An assembly according to any preceding claim, in which the restrained driver pin is positioned to the rear of the other driver pins.

14. A cylinder assembly for a lock, the assembly being substantially as herein described with reference to the accompanying drawings.