GB2439781A

GB2439781A - Cylinder plug with two pairs of inserts

Info

Publication number: GB2439781A
Application number: GB0613285A
Authority: GB
Inventors: Bruce Patrick Mccarthy
Original assignee: Assa Abloy Ltd
Current assignee: Assa Abloy Ltd
Priority date: 2006-07-04
Filing date: 2006-07-04
Publication date: 2008-01-09
Anticipated expiration: 2026-07-04
Also published as: IE20070457A1; GB0613285D0; GB2439781B

Abstract

A plug for a cylinder assembly of a lock is of generally circular cylindrical shape and includes a keyway 2 extending along the longitudinal axis of the body 1 of the plug. The plug includes in the region of its front end first and second pairs of inserts 8A, 8B, 9A and 9B made of a material harder than the material of the body 1 of the plug. The inserts 8A, 8B, 9A and 9B of each pair extend on opposite sides of the keyway 2 adjacent thereto in a direction transverse to the longitudinal axis of the plug, with the inserts of the first pair 8A, 8B axially spaced from the inserts of the second pair 9A, 9B. The plug further includes a plurality of axially spaced tumbler pin passageways 6 extending transverse to the longitudinal axis of the plug from the periphery of the plug to the keyway 2 for slidably receiving tumbler pins.

Description

0 2439781 Cylinder plug This invention relates to a plug for a cylinder

assembly of 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 lock is to force a threaded member, such as a screw, into the end of a plug and along the keyway. The member then is in threaded engagement with the plug and large forces can be applied to the plug via the threaded member, destroying the lock.

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

According to the invention there is provided a plug for a cylinder assembly of a lock, the plug being 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 for slidably receiving tumbler pins, wherein the plug further includes in the region of the front end of the plug first and second pairs of inserts made of a material harder than the material of the body of the plug, the inserts of each pair extending on opposite sides of the keyway adlacent thereto in a direction transverse to the longitudinal axis of the plug, with the inserts of the first pair axially spaced from the inserts of the second pair.

By providing two pairs of inserts a substantial obstacle to insertion of a threaded member into the front of the plug is provided. Whilst a single pair of such members is of some value, for example in restricting the diameter of a member that can reasonably be inserted, we have found that the provision of a second pair of inserts adds a surprising amount of extra protection: whereas with a single pair of inserts the thread of a member inserted may actually engage the inserts and therefore in some

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respects actually improve the grip on the plug of an inserted member, two pairs of inserts tend to act to strip the thread.

Whilst reference is made above to first and second pairs of inserts it will be understood that there may be one or more further pairs of inserts, if desired.

The inserts may be disposed in a variety of configurations, some of which will be referred to below.

Whilst it is within the scope of the invention for the inserts of a pair to be staggered in an axial direction it is preferred that the inserts are disposed at substantially the same position along the longitudinal axis. The inserts of each pair are preferably disposed approximately parallel to each other on opposite sides of the keyway. The cross-sectional shape of the keyway may be of elongate rectangular shape and the inserts are then preferably disposed adjacent to the longer sides of the keyway. In such an arrangement it is possible to have only a small spacing between inserts so that only a small screw threaded member can be inserted between them.

Preferably each insert extends from a peripheral region of the plug at least as far as a central region of the plug and more preferably beyond the central region of the plug.

In one embodiment described below, the inserts of a pair extend from the same peripheral region of the plug at least as far as the central region of the plug. In that case the keyway may also extend to the same peripheral

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region of the plug, but another possibility is for the keyway to extend to a peripheral region opposite said peripheral region from which the inserts of a pair extend.

In a preferred arrangement, the first pair of inserts extend from a first peripheral region of the plug and the second pair of inserts extend from a second peripheral region of the plug opposite to the first peripheral region.

It is, however, within the scope of the invention for both pairs of inserts to extend from the same peripheral portion of the plug.

In the arrangements described above the inserts of a pair extend from the same peripheral portion of the plug, but an alternative arrangement within the scope of the invention is for the inserts of a pair to extend from opposite peripheral regions of the plug at least as far as the central region of the plug.

Preferably the inserts are located towards the front of the plug. If the inserts were provided only at the rear then their effect could be negated simply by screwing a member only partway into the plug. Thus fewer than two tumbler pin passageways are preferably located in front of one of the pairs of inserts. Preferably the first pair of inserts is located in front of all the tumbler pin passageways. In such a case the first pair of inserts will be especially close to the front of the plug. The second pair of inserts are preferably located axially between two adjacent tumbler pin passageways, preferably behind the most forward tumbler pin passageway but in front of the

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next most forward tumbler pin passageway. Thus in the preferred arrangement the most forward tumbler pin passageway is located, in terms of its axial position, between the first and second pairs of inserts.

Each insert preferably comprises an elongate cylinder, preferably of circular cross-section, housed in a respective bore formed in the plug. The bore preferably opens onto the periphery of the plug. The inserts may be a force fit in the bores or may be held in the bores by other means.

In order to be effective the material from which the inserts are made is harder than the material from which the body of the plug is made. In an embodiment of the invention described below the material from which the inserts are made has a hardness on the Rockwell scale in the range of to 70 HRC and a Vickers hardness in the range of 600 to 900 Hv.

In normal use the plug is received within a cylinder to form a cylinder assembly. Accordingly, the invention further provides a cylinder assembly for a lock including a cylinder and a plug as defined above mounted in the cylinder.

The cylinder assembly, once readied for use includes tumbler pins slidably received in the tumbler pin passageways of the plug and may be employed in a lock assembly.

By way of example, various examples of plugs for cylinder assemblies of locks, all being embodiments of the

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invention, will now be described with reference to the accompanying drawings, of which: Fig. 1A is an exploded perspective view of a first plug; Fig. lB is a plan view of the first plug; Fig. 1C is an inverted sectional view along the line C-C in Fig. lB of the first plug; Fig. 1D is an inverted sectional view along the line D-D in Fig. 1C of the first plug; Fig. 1E is an inverted sectional view along the line E-E in Fig. 1C of the first plug; Fig. 2A is an exploded perspective view of a second plug; Fig. 2B is a plan view of the second plug; Fig. 2C is an inverted sectional view along the line C-C in Fig. 2B of the second plug; Fig. 2D is an inverted sectional view along the line D-D in Fig. 2C of the second plug; Fig. 2E is an inverted sectional view along the line E-E in Fig. 2C of the second plug; Fig. 3A is an exploded perspective view of a third plug; Fig. 3B is a plan view of the third plug; Fig. 3C is an inverted sectional view along the line c-c in Fig. 3B of the third plug; Fig. 3D is an inverted sectional view along the line D-D in Fig. 3C of the third plug;

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Fig. 3E is an inverted sectional view along the line E-E in Fig. 3C of the third plug; and Fig. 4 is a perspective view of a cylinder assembly incorporating two plugs embodying the invention.

Referring first to Figs. 1A to 1E, there is shown a plug which is of generally conventional design. The plug comprises a body 1 which is of generally cylindrical shape and includes a keyway 2 that extends along the longitudinal axis of the plug and is open at the front end 3 of the plug to allow insertion of a key into the keyway 2. As can be seen in Figs. 1D and 1E, the cross-sectional shape of the keyway is of elongate rectangular shape, having relatively long sides 4 and short top and bottom ends 5. The keyway is open at the end that meets the periphery of the plug body (in the example shown this is the bottom of the keyway but in other plugs it might be the top of the keyway).

The plug body 1 is formed with a series of radially extending passageways 6 axially spaced from one another but aligned radially. In this particular example there are six such passageways. The passageways 6 extend from the periphery of the plug body 1, from a position opposite the open end of the keyway 2, and extend into the keyway; in the example shown, they extend from the top of the plug body 1. In use, the passageways 6 accommodate tumbler pins that are slidably received in the passageways and biased towards the keyway 2 by driver pins which, prior to insertion of a key, are slidably received partly in the

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plug body 1 and partly in passageways of the cylinder surrounding the plug body, thereby preventing rotation of the plug body relative to the cylinder in which it is housed.

At its rear end, the plug body 1 is provided with a slot 7 extending diametrically across the body, by means of which rotation of the plug can be converted to rotation of another member for operating a lock.

All the features described above are conventional and are well known features of plugs of cylinder lock assemblies.

The plug shown in Figs. 1A to 1E is distinguished from standard plugs by the provision of two pairs of hard inserts received in blind bores in the plug body 1. More particularly there is a first pair of inserts 8A, 8B and a second pair of inserts 9A and 9B. Each of the inserts is of the same form and comprises a cylindrical rod of circular cross-section. Each insert is received as a force fit in a respective blind bore 10 formed in the plug body 1.

In the first plug shown in Figs. lA to 1E, the first pair of inserts 8A and 8B are located in front of the most forward tumbler pin passageway 6 and extend parallel to one another in a plane perpendicular to the axis of the plug from a bottom peripheral region of the plug adjacent to the open end of the keyway 2 up through the central region of the plug and almost to the top peripheral region of the plug. Thus, as can be seen from Fig. 1D, the inserts are C, located immediately adjacent to the sides of the keyway 2 and parallel to those sides. The second pair of inserts 9A and 9B are located between the most forward and the next most forward tumbler pin passageways 6 and extend parallel to one another in a plane perpendicular to the axis of the plug from a top peripheral region of the plug down through the central region of the plug and almost to the bottom peripheral region of the plug. Thus, as can be seen from Fig. 1E, the inserts are located immediately adjacent to the sides of the keyway 2 and parallel to those sides.

The plug body 1 is made of the same material as in a standard plug but the inserts 8A, BB, 9A and 9B are made of a material that is harder than the material of the plug body. In one particular example of the invention the inserts 8A, 8B, 9A and 9B are made of a hard steel and have a hardness on the Rockwell scale in the range of 55 to 70 HRC and a Vickers hardness in the range of 600 to 900 Hv.

The inserts 8A, 8B, 9A and 9B protect the plug against attack in the following manner. If an attempt is made to screw a member into the front of the plug, then the core of that member cannot be significantly wider than the keyway 2 if it is to pass between the inserts. A member with such a narrow core but with a radially projecting thread might then be able to pass the first pair of inserts with the inserts engaging in the thread, but the second pair of inserts would still be an obstruction and indeed the combined effect of the first and second sets of inserts should be to strip the thread, thereby preventing the

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-10 -inserted member from obtaining a good grip on the plug.

Figs. 1A to 1E show one form of plug that may be employed. Figs. 2A to 2E and Figs. 3A to 3E show other forms of plug which differ only in the arrangement of the inserts 8A, 8B, 9A and 9B. The same reference numerals are therefore used in those other figures as in Figs. 1A to 1E.

In the plug of Figs. 2A to 2E, the inserts 8A and 8B extend parallel to one another in a plane perpendicular to the axis of the plug from a top peripheral region of the plug down through the central region of the plug and almost to the bottom peripheral region of the plug adjacent to the open end of the keyway 2. The inserts 9A and 9B extend parallel to one another in a plane perpendicular to the axis of the plug from a bottom peripheral region of the plug adjacent to the open end of the keyway 2 up through the central region of the plug and almost to the top peripheral region of the plug.

In the plug of Figs. 3A to 3E, the inserts of each pair again extend parallel to one another in a plane perpendicular to the axis of the plug but from opposite peripheral regions of the plug. Thus, the inserts 8B and 9A extend from a top peripheral region of the plug down through the central region of the plug and almost to the bottom peripheral region of the plug adjacent to the open end of the keyway 2. Similarly, the inserts 8A and 9B extend from a bottom peripheral region of the plug adjacent to the open end of the keyway 2 up through the central region of the plug and almost to the top peripheral region

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-11 -of the plug.

It will be understood that the drawings show three particular arrangements of inserts by way of example and that there are many other arrangements that may be adopted in accordance with the invention. Whilst in the illustrated embodiments there are two pairs of inserts provided, it is of course possible to provide further inserts.

As already indicated, in use the plug is housed within a cylinder of a cylinder lock assembly. Fig. 4 shows a cylinder assembly for use in a cylinder lock and comprising two cylinder housings 21 and 22, in each of which respective plugs are housed. The assembly is of a kind that is generally well known but is distinguished by the inclusion of plugs embodying the invention. In Fig. 4, a plug body 1 having a keyway 2 can be seen within the cylinder housing 21, which includes an extended portion 23 in which passages that can align with the tumbler pin passageways 6 are provided, those passages receiving driver pins and springs in a manner known per se. Also visible in Fig. 4 is the cam 24 that is able to be drivingly connected by the slot 7 to the plug body 1.

Claims

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-12 -Claims: 1. A plug for a cylinder assembly of a lock, the plug being 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 for slidably receiving tumbler pins, wherein the plug further includes in the region of the front end of the plug first and second pairs of inserts made of a material harder than the material of the body of the plug, the inserts of each pair extending on opposite sides of the keyway adjacent thereto in a direction transverse to the longitudinal axis of the plug, with the inserts of the first pair axially spaced from the inserts of the second pair.

2. A plug according to claim 1, in which the inserts of each pair are disposed at substantially the same respective position along the longitudinal axis 3. A plug according to claim 1 or 2, in which the inserts of each pair are disposed approximately parallel to each other on opposite sides of the keyway.

4. A plug according to claim 3, in which the cross-sectional shape of the keyway is of elongate rectangular shape and the inserts are disposed adjacent to the longer sides of the keyway.

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-13 - 5. A plug according to any preceding claim, in which each insert extends from a peripheral region of the plug at least as far as a central region of the plug.

6. A plug according to claim 5, in which each insert extends from a peripheral region of the plug into and beyond a central region of the plug.

7. A plug according to claim 5 or 6, in which the inserts of a pair extend from the same peripheral region of the plug at least as far as the central region of the plug.

8. A plug according to claim 7, in which the keyway also extends to the same peripheral region of the plug.

9. A plug according to claim 7, in which the keyway extends to a peripheral region opposite said peripheral region from which the inserts of a pair extend.

10. A plug according to any of claims 7 to 9, in which the first pair of inserts extend from a first peripheral region of the plug and the second pair of inserts extend from a second peripheral region of the plug opposite to the first peripheral region.

11. A plug according to any one of claims claim 5 to 10, in which the inserts of a pair extend from opposite peripheral regions of the plug at least as far as the central region of the plug.

12. A plug according to any preceding claim, in which fewer than two tumbler pin passageways are located in front of one of the pairs of inserts.

* 13. A plug according to any preceding claim, in which the first pair of inserts is located in front of all the C, -14 -tumbler pin passageways.

14. A plug according to any preceding claim, in which the second pair of inserts are located axially between two adjacent tumbler pin passageways.

15. A plug according to claim 14, in which the second pair of inserts are located behind the most forward tumbler pin passageway but in front of the next most forward tumbler pin passageway.

16. A plug according to any preceding claim, in which each insert comprises an elongate cylinder housed in a respective bore formed in the plug.

17. A plug according to any preceding claim, in which the elongate cylinders are of circular cross-section.

18. A plug substantially as herein described with reference to the accompanying drawings.

19. A cylinder assembly for a lock including a cylinder and a plug according to any preceding claim mounted in the cylinder.

20. A cylinder assembly according to claim 19, including tumbler pins slidably received in the tumbler pin passageways of the plug.