GB2384523A - Attack protection for cylinder locks - Google Patents

Abstract

A lock cylinder has a body (10) comprising a face part (11) from the rear of which extend a plug receiving cylinder (13) and a protrusion (15) extending radially from the cylinder (13). At the end of the body remote from the face part (11) there are a pair of lateral ears (16, 17) with threaded holes therethrough to receive fixing screws to secure the lock in place, in use, in an aperture through a door. To improve security of the lock an anti-drill shield is fitted to the protrusion (15), the shield providing two deflector plates (25, 26) against the rear of the face part, which plates serve, in use, should an attempt be made to drill through the face part to reach the ears and the fixing screw positions, to deflect the drill and prevent it reaching said positions.

Description

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CYLINDER LOCKS This invention relates to pin tumbler cylinder locks.

A pin tumbler lock typically has a lock body which is fixed in an opening through a wing, such as a door, with a circular face of the body being disposed at the side face of the door which is normally its outer face, in use.

This face has therethrough a circular section opening which is a continuation of a circular section bore through the main part of the lock body, i. e. that part which is received within the door, and a rotatable plug is received in said bore. Accordingly a forward end of the plug is disposed in the opening in the face of the lock body, providing a slot for insertion of the key of the lock, to lift the pin tumblers and permit rotation of the plug in the normal manner.

At the rear end of the plug, it is common-for it to have an annular groove for a circlip or the like to retain a flat connecting bar which, in use, acts upon a locking mechanism in the door width, to operate a bolt or latch of the lock assembly.

Commonly the part of the lock body within the door is made up of a first portion which exteriorally is cylindrically shaped, in the interior bore of which the plug is rotationally disposed, and an integral narrow second portion which extends radially from the first portion, in the interior of which are a series of spaced drillings which receive in the normal manner spring loaded drivers to act on the lock pins in the plug.

To retain the lock body in the opening through the door, it is usual for the rear of the lock body, at the junction between the first and second parts

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thereof, to be formed with a pair of lateral ears extending to respective opposite sides of the second portion of the lock body within the door. The ears have respective screw threaded holes therethrough to receive respective fixing screws extending through the door from the opposite side thereof from that at which the face of the lock is disposed. The respective ends of the screws generally project a short way beyond the holes through which they engagingly pass, but terminate spaced from the inner side of the face of the lock.

It is known that an attack on the lock often involves the attacker drilling through the outer exposed face of the lock body to reach the ears, so as to release the fixing of the lock body in the door and thus overcome the locking function. Whilst it may be possible to counter such an attack by using harder fixing screws, this is disadvantageous in that the fixing screws need to be cut to shorten them for use at less wide doors.

An object of the invention is to improve the security of pin tumbler cylinder locks.

According to one aspect of the invention there is provided a pin tumbler lock cylinder having a face from the rear of which extends a plug receiving cylinder and a protrusion extending radially from the cylinder, a pair of lateral projections on the cylinder and/or the protrusion at opposite sides respectively of the protrusion, threaded openings respectively through said projections, and an anti-drill shield having a part fitted on said protrusion and providing respective abutments disposed ahead of said threaded openings in a direction from said cylinder lock face towards the openings.

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Preferably the anti-drill shield is as in said another aspect of the invention.

According to another aspect of the invention there is provided an anti-drill shield for a pin tumbler lock cylinder, the shield having a pair of parallel or generally parallel legs extending from a closed end portion, a pair of wings extending laterally outwardly from said legs respectively, and a pair of arms, perpendicular or substantially perpendicular to said wings respectively, at respective opposite sides of said legs.

Preferably the shield is of unitary construction, and desirably the shield is made of metal, for example case hardened steel. Conveniently the respective junctions between the legs and the wings, and between the wings and the arms are radiussed. Advantageously the arms are folded out of the planes of respective outer side surfaces of the shield defined by said wings to extend therebeyond and prevent access to the respective areas immediately above said outer side surfaces from one end of the shield in a direction parallel to said side surfaces. More preferably said arms are at said one end of the shield. More desirably, the closed end portion is curved. More conveniently the wings extend downwardly at an obtuse angle from the plane of the legs respectively.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a front perspective view of a conventional pin tumbler lock cylinder body,

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Figure 2 is a perspective view of an anti-drill shield according to one aspect of the present invention, and Figure 3 is a rear perspective view of the body of Figure 1, with the shield of Figure 2 fitted thereto, in accordance with another aspect of the present invention.

The pin tumbler lock cylinder body 10 shown in Figure 1 is of known form and is of one piece in brass. The lock body 10 comprises a cylindrical face part 11 through which extends a circular section opening 12 which has its central axis offset from the central axis of the face part 11. As viewed in Figure 1, the respective axes of the part 11 and the opening 12 are on the same vertical centre line, but with the axis of the opening 12 being spaced below that of the face part 11. Extending from the rear of the face part 11 is a plug receiving cylinder 13 which has a circular section bore 14 centrally therethrough, the longitudinal axis of the bore 14 being coincident with the axis of the opening 12 so that the opening 12 forms a continuation of the bore 14 through the face part 11. A rotatable pin tumbler lock cylinder plug (not shown) is received in the bore 14 in the normal manner, the plug being of conventional form having appropriate drillings to receive the pins of the pin tumbler lock. Also extending from the rear of the face part 11 is a protrusion 15 which also extends radially from the outer cylindrical surface of the cylinder 13, the protrusion 15 terminating just short of the end of the cylinder 13 remote from the face part 11. Again this arrangement is wholly conventional, the protrusion being provided with internal drillings (not shown) to receive springs and driver pins to cooperate with the pins of the

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lock plug, in the normal manner so that, in use, with the correct key inserted into the plug, the respective interfaces between the plug pins and the drivers in the extension part 15 exactly correspond to the interface between the plug and the inner end of the extension part 15, so that the plug can then be rotated in its cylinder 13 so as to rotate a conventional connecting bar connected to and extending from the rear end of the plug remote from the face part 11 to actuate a locking mechanism of the lock in a door or other wing, in the normal manner.

As shown in both Figures 1 and 3, there is provided at the junction between the cylinder 13 and the protrusion 15 at the end of the protrusion 15 remote from the face part 11, a pair of oppositely directed laterally extending projections in the form of ears 16,17 respectively, the ears extending at opposite sides of the protrusion 15. Each- ear extends beyond the periphery of the cylinder, but does not extend beyond the sideways boundary of the lock cylinder body defined by the diameter of the face part 11. The ears 16, 17 are formed with respective threaded holes 18,19 therethrough to receive respective fixing screws (not shown). In use, in the normal manner, the cylinder 13 and protrusion 15 are received in a bore through a wing, such as a door, and the lock body is held in place by the fixing screws referred to above extending through the door from the opposite side thereof from that at which the face part 11 is disposed. When said fixing screws passing through the holes 16,17 respectively are tightened, they draw the lock cylinder body in a direction towards said opposite side of the door and thus tightly secure the cylinder 13 and protrusion 15 in the bore in the door in which they are received with the face plate being held tightly against a rose which is thus itself held at said face of the door around the bore through the door which

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accommodates the remainder of the lock cylinder body. Normally the face part 11 is at the surface of the door which is outermost, in use, so that the fixing screws cannot be accessed from outside of the door.

However it is known that burglars will attack this form of lock by drilling through the outer exposed face part 11 in an attempt to reach and disable the fixing screws which are engaged in the respective ears 16,17, the respective ends of such screws normally extending at least a short way beyond said ears towards the rear surface of the face part 11. In this manner it is possible to drill through the ears and thus release the remainder of the lock body from the fixing screws, thus overcoming the locking function.

The present invention seeks to improve the security of the lock by providing an anti-drill shield which is fitted to the lock body as shown in Figure 3 to prevent access to the ears by drilling through the face part 11 of the lock cylinder as described above.

The anti-drill shield, which is shown in Figure 2, and which clips on to the lock cylinder body as shown in Figure 3, is made of metal, preferably case hardened steel. Moreover in the embodiment described, it will be appreciated that the shield is made in one piece. Conveniently it is produced in the general form of a strip of material, with one of the longitudinal sides thereof at its respective opposite ends being formed with lateral projections which, in the final form of the shield, as will be described, act as drill deflectors.

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Figure 2 shows the shield produced by appropriate bending/folding of the initial strip. The shield is formed with a pair of spaced parallel legs 20,21 which extend from an arcuate closed end section 22. Basically the extent and curvature of the section 22, the length of the legs, and the spacing apart thereof is such as to match the outer shape of the extension part 15, so that, as shown in Figure 3, the section 22 and the legs are a close fit over the part 15 of the lock cylinder body. This part of the shield can clip tightly onto the protrusion 15, in the manner of an interference fit, and depending upon the material of the shield there could be flexing to effectively'snap-fit'the shield in place. As shown in Figure 3, in this embodiment, the shield does not extend for the whole longitudinal extent of the part 15, although it could do so if required.

The respective end portions of the rectangular strip forming the shield are bent outwardly at an obtuse angle from the legs respectively to form a pair of laterally outwardly and downwardly directed wings 23,24 respectively. The angle at which these wings extend is dependent upon the curvature of the lock cylinder 13 and thus its disposition relative to the protrusion 15 at respective opposite sides of that part. In other words the wings are arranged to engage against the respective parts of the exterior surface of the cylinder at respective opposite sides of the protrusion 15, as shown in Figure 3. It will be appreciated that in the embodiment shown each wing does not contact the whole of the surface of the cylinder adjacent the protrusion 15, given that the cylinder surface is curved whilst each wing is straight, but there can be sufficient contact so that these wings are supported on the cylinder surface.

However in alternative embodiments the wings could be curved to match the curvature of these respective parts of the cylinder at respective opposite sides

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of the protrusion 15, or alternatively in some embodiments it may not be necessary for these wings actually to engage these surfaces of the cylinder at respective opposite sides of the protrusion 15.

Finally it will be seen from Figure 2 that the lateral projections on the strip referred to above, are themselves turned through 900 or substantially 90 to form two short upstanding arms or deflectors 25,26 respectively. Each arm thus extends above the level of the outer planar surface of the wing with which the arm is connected. When the shield is fitted onto the lock body, as shown in Figure 3, it can be seen that as these arms are at the end of the shield which is disposed adjacent the rear of the face part 11, these arms engage against the rear surface of the face part 11, whilst at the other end of the shield the respective edge faces of the wings opposite those from which the arms extend, engage against the ears 16, 17 so that the shield is tightly held in place with little or no longitudinal movement being possible longitudinally of the lock body. It will be appreciated that the height of the upstanding arms can be varied as required, their purpose being, as will be described, to prevent drill access through the face part 11 to the ears 16,17 and fixing screws.

When the lock body and shield of Figure 3 are, in use, fitted to a door, the respective ends of the fixing screws passing though the holes 18,19 will extend over the outwardly facing surfaces of the wings 23,24 respectively and this engagement will, as described, assist in retaining the shield in place on the lock body. The ends of the screws may or may not actually contact these outer side surfaces of the wings, but if they do not contact them they will be sufficiently close thereto to prevent'lifting'of the shield.

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Additionally lifting is also prevented or restricted by the size of the bore through the door. In other words any attempt to prise off the shield may result in the end section 22 abutting against the interior surface of the bore before there is any significant'lifting'of the shield.

Accordingly if an attempt is made to drill through the face part 11 from the front thereof in order to reach the ears 16,17, the drill tip, on passing through the face part 11, will meet one of the arms or deflectors 25,26 and will be'deflected'such that upon continued drilling the drill bit will now be diverted and will not reach the ear towards which it was originally directed.

This is true whichever side of the face plate is drilled, and in all cases it is considered that the arms or deflectors will be sufficient to prevent an attack on the security of the lock succeeding, including where an attempt might be made to avoid the deflectors by drilling at an angle downwardly from the face part 11 instead of the conventional drilling attack which is in the general horizontal plane of the ears 16,17.

As explained above, the clip is fitted securely onto the lock cylinder body so that when the drill hits an arm or deflector 25 or 26, this will not cause the shield to deflect off the body. As described any longitudinal movement of the clip is minimised and additionally any upward movement of either wing is prevented by the end of the screw, where these are of sufficient length to extend over the wings. Thus a simple and effective means is provided for improving the security of the lock.

It will be understood that the shield can be of a different form to that shown, it merely being necessary that a part thereof is adapted to fit part of the lock

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cylinder body, for example that containing the driver pins and springs, together with abutments disposed ahead of the threaded openings, in a direction from said lock cylinder face towards said openings.

Claims (21)

1. CLAIMS 1. A pin tumbler lock cylinder having a face from the rear of which extends a plug receiving cylinder and a protrusion extending radially from the cylinder, a pair of lateral projections on the cylinder and/or the protrusion at opposite sides respectively of the protrusion, threaded openings respectively through said projections, and an anti-drill shield having a part fitted on said protrusion and providing respective abutments disposed ahead of said threaded openings in a direction from said cylinder lock face towards the openings.
2. 2. A lock cylinder as claimed in Claim 2, wherein the shield comprises wing portions extending from said part on said protrusion to respective opposite sides thereof.
3. 3. A lock cylinder as claimed in Claim 2, wherein said wing portions extend laterally outwardly from said part on said protrusion.
4. 4. A lock cylinder as claimed in Claim 3, wherein said wing portions engage respective portions of the external surface of the cylinder at opposite sides of the protrusion.
5. 5. A lock cylinder as claimed in any one of Claims 1 to 4, wherein the part of the shield fitted on the protrusion comprises a pair of parallel legs engaging respective opposite parallel sides of the protrusion and a closed end portion engaging a complementarily shaped end portion of the protrusion from which the parallel sides extend.

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6. 6. A lock cylinder as claimed in any one of Claims 2 to 4, wherein said respective abutments are upstanding arms perpendicular or substantially perpendicular to said wings.
7. 7. A lock cylinder as claimed in Claim 6, wherein the arms extend from said wings.
8. 8. A lock cylinder as claimed in Claim 6 or Claim 7, wherein at one end of the shield said arms engage a rear of said face of the lock cylinder, and at the opposite end of the shield the wing portions engage said lateral projections.
9. 9. A lock cylinder as claimed in any one of Claims 2 to 4, wherein the wing portions define respective flat outer side surfaces disposed below the level of said threaded openings, so that the respective ends of fixing elements extending through said openings, in use, extend over said side surfaces to prevent displacement of the shield.
10. 10. A lock cylinder as claimed in any one of the preceding claims, in which the shield is of one-piece construction.
11. 11. A lock cylinder as claimed in any one of the preceding claims, in which the shield is of metallic material.
12. 12. A lock cylinder as claimed in any one of the preceding claims, in which the shield is formed by folding a flat strip along fold lines thereof.

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13. 13. An anti-drill shield for a pin tumbler lock cylinder, the shield comprising a pair of parallel or generally parallel legs extending from a closed end portion, a pair of wings extending laterally outwardly from said legs respectively, and a pair of arms, perpendicular or substantially perpendicular to said wings respectively, at respective opposite sides of said legs.
14. 14. A shield as claimed in Claim 13, wherein said closed end portion is curved.
15. 15. A shield as claimed in Claim 13 or Claim 14, wherein said arms extend from said wings.
16. 16. A shield as claimed in any one of Claims 13 to 15, wherein the arms are folded out of the planes of respective outer side surfaces of the shield defined by said wings respectively to extend therebeyond and prevent access to the respective areas immediately above said outer side surfaces from one end of the shield in a direction parallel to said side surfaces.
17. 17. A shield as claimed in any one of Claims 13 to 16, which is of unitary construction.
18. 18. A shield as claimed in any one of Claims 13 to 17, which is of metallic material.

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19. 19. A shield as claimed in any one of the preceding claims, formed by folding a flat strip along fold lines thereof.
20. 20. A pin tumbler lock cylinder substantially as hereinbefore described, with reference to, and as shown in Figure 3.
21. 21. An anti-drill shield for a pin tumbler cylinder lock substantially as hereinbefore described, with reference to and as shown in Figure 2.