GB2314375A - Cylinder Locks - Google Patents

Abstract

A cylinder lock comprises a body 10, a rotatable cylinder 13 in the body with a key slot therethrough, and a plurality of radially extending biased pins 17, 18, 19 mounted in radial bores 15 in the cylinder and aligned bores 16 in the body so that, as is conventional, the cylinder can be turned on insertion of an appropriate key 23 . The lock incorporates an additional interlocking element, such as a peg 24, which is biased to project from the body into the key slot so as prevent cylinder rotation except when the correct key is fully inserted into the key slot, whereupon the peg is moved out of the key slot and thus the cylinder, to allow cylinder rotation.

Description

CYLINDER LOCKS This invention relates to cylinder locks for use in locking doors or other closures.

With a conventional cylinder lock the lock cylinder is secured from rotation in the lock body by means of a system of pins, drivers and springs at each of a number of locations along the length of the lock cylinder. Where it is required for the lock to be operated by several different keys, it is normal practice to insert an extra component, known as a disk, between a pin and its associated driver. The inclusion of one or more such disks with a selected number of the pins means that at each such pin/driver assembly there are different lift heights at which a split line between the cylinder and the lock body occurs, and thus various differently cut keys can operate the lock. Where the lock is heavily master keyed, for example on an apartment block front door, several disks will be provided with each pin.

Such an arrangement results in reduced security because accidental split lines can be created by a person pushing an incorrect key rapidly into and out of the cylinder whilst applying a turning force to the key, or by a person partly inserting an incorrect key so that at least one pin bears on an angled surface of the key notch rather than resting in the bottom of the notch.

The first of these practices is known as 'raking' the key, and as a consequence anti-rake keys have been developed with a view to counteracting it. Such keys generally have a small notch cut into the key, an obstruction being provided in the lock body, usually in the form " of a small split washer, so that the cylinder is prevented from rotating by engagement of the key against the obstruction, this occurring unless the notch is aligned with the obstruction upon full insertion of the key into the cylinder. Accordingly this defeats any attempt to operate the lock by partial key insertion or by rapid in and out movement of the key. An arrangement of this type is disclosed in our UK Patent No 2223054B.

A problem with such an anti-rake solution is that the notch can severely weaken the key, leading to the possibility of keys breaking off in the cylinder, particularly when the lock has to be released against a side loading, or where the user accidentally tries to turn the key before it is fully inserted. Moreover for a key and cylinder lock system which has already been sold, the lock must be modified or replaced to provide the obstruction and every key must be replaced with one containing the notch.

Where a lock cylinder can be rotated without the key being fully inserted, a further problem, apart from the security aspect, is that it is possible for disks to escape from the chambers in the cylinder into the open key slot left in the cylinder by the absence of the key, once the cylinder has been rotated by 1800. As a result, some correct keys are rendered subsequently unusable.

An object of the invention is to provide a cylinder lock in which the above problems are at least minimised, or overcome.

According to the invention a cylinder lock comprises a body, a cylinder rotatably mounted in the body, a key slot in the cylinder for receiving a key, a plurality of radially extending pins mounted in radial bores in the cylinder and aligned bores in the body, the pins being biased towards the key slot, each pin being split into at least two portions so that the cylinder can be turned only when the interfaces between the pin portions are made by the insertion of an appropriate key to coincide with the surface of the cylinder, at least one of said pins being split into at least three portions so that a plurality of different appropriate keys can be used to turn the cylinder, and an additional interlocking element biased to project from the body into the key slot across said surface of the cylinder so as to obstruct turning of the cylinder unless an appropriate key is fully inserted into said key slot, whereupon the additional interlocking element is moved out of said key slot and clear of said surface of the cylinder, thereby to allow turning of the cylinder by said fully inserted key.

Advantageously the additional interlocking element is mounted on the body. Preferably the additional interlocking element is a peg received in a bore extending through the body, the bore being in communication with the key slot when the cylinder is in its locked position.

Conveniently the external surface of the body has a groove therein, the groove being in communication with the bore through the body and containing a spring clip which acts on the peg to bias it to extend from the body into the key slot. Desirably the bore is arranged beyond the final pin in the direction of key insertion, so that the part of the peg which protrudes into the key slot is only moved out of the key slot upon full insertion of a standard key, i.e. one with a continuous flat surface opposite to its conventional notched narrow side.

The invention will now be described, by way of example, with reference to, and as shown in, the accompanying drawings, in which: Figure 1 is a fragmentary longitudinal side sectional view of a conventional cylinder lock, with no key inserted; Figure 2 is a view of part of the lock shown in Figure 1, with a key only partly inserted; Figure 3 is a view like Figure 1, showing a cylinder lock of the invention, with a correct key fully inserted; Figures 4 and 5 are enlarged views of part of the lock of Figure 3, showing an interlocking peg in a locking and release position respectively; Figure 6 is a fragmentary top view to a reduced scale of the lock of Figure 3; Figure 7 is a sectional view on line 7-7 of Figure 6; Figures 8 and 9 are respectively a top plan view and an underneath plan view, to a smaller scale, of the peg of Figures 4 and 5; and Figure 10 is a side view of a biasing clip shown, to a larger scale, with the peg in Figures 4 and 5.

Figure 1 shows a conventional form of pin tumbler cylinder lock comprising a body 10 having a circular section bore 11 therethrough, this being formed with a step 12 to provide a wider part of the bore at the front of the lock body. Rotatably fitted in the bore 11 is a plug or cylinder 13 which has a cylindrical flange 14 at its one end, this being received in the enlarged portion of the bore 11 formed by the step 12.

At its opposite end, the cylinder is formed with an annular groove in its external surface for reception of a retaining clip or the like to hold the cylinder in the lock body. The cylinder 13 has a key slot formed therethrough, and as is well known, this is in communication, at one side thereof, with a plurality of radial bores 15 spaced in alignment along the length of the cylinder.

In the 'locked' position of the cylinder, these bores 15 are aligned with corresponding radial bores 16 spaced longitudinally in the body, the bores 16 being in direct communication with the bores 15, as shown in Figure 1.

The cylinder is normally secured from rotation in the body by means of a system of pins, springs and drivers repeated along the length of the cylinder. Figure 1 shows for each set of aligned bores 15 and 16 an accommodated pin 17, associated driver 18 and associated biassing coiled compression spring 19. One end of the spring bears against the driver, whilst its other end engages a plug which closes the bore 16. As described in the introduction, some cylinders are master keyed, with there being one key operating all cylinders in a particular building, and individual keys which operate only one cylinder or a group of cylinders.

In such a case, at least one extra component known as a disk is inserted between the pin and its associated driver. Examples of such disks 20 are shown in Figure 1 for the second, third and sixth pin tumbler assemblies as counted in the direction of key insertion. The inclusion of one or more of these disks 20 means that there are different lift heights at which at split line occurs, and therefore various differently cut keys will operate the cylinder.

Figure 2 illustrates one of the problems referred to in the introduction, namely that where a person using an incorrect key does not fully insert it into the cylinder.

As illustrated in Figure 2 for the inwardsmost tumbler set, it is possible partly to insert the key so that the end of the pin 1 7 bears on an angled surface 21 of a key notch rather than resting in the bottom of its correct notch. It will be appreciated that in certain circumstances the engagement of the pin 1 7 at the surface 21 will be such that the pin 1 7 is pushed downwardly, as viewed in Figure 2, to a position where a split line is formed at the outer surface of the cylinder, thereby, as far as this pin tumbler set is concerned, allowing cylinder rotation, even though the key is not fully inserted into the lock.

As will be clear from Figure 2, rotation of the cylinder with the key in this state makes it possible for one or more of the disks 20 shown in figure 2 to escape from the bore 15 into the part of the key slot which remains open in the absence of the key being fully inserted, this open part being denoted generally by the numeral 22 in figure 2. As a result of the loss of these disks, some correct keys may be rendered inoperable.

As used herein, the term "pin" includes a pin 17, its associated driver 18, and one or more of the disks 20, so that where the pin tumbler comprises merely a pin 17 and driver 18, it will be considered that the pin is split into two portions, whereas where a disk is also provided, the pin will be considered to be split into three portions, and so on, if more disks are provided.

The embodiment of a cylinder lock of the invention shown in Figure 3 incorporates an anti-raking system which does not weaken the key, does not require existing keys to be replaced, and at the same time removes the possibility of cylinder disks 20 becoming dislodged from their correct positions in the pin chambers or bores.

As can be seen from Figure 3, the cylinder lock is of a very similar form to that shown in Figure 1. However, the lock incorporates an additional interlocking element which prevents rotation of the cylinder relative to the body unless a correct key 23, also shown partly in Figure 2, is fully inserted into the lock. The key 23 is of conventional form with its blade having the usual pin-receiving notches in its 'front' edge, with its 'rear' edge being straight, namely flat and continuous, this straight edge being, in use, flush with the open, outer side of the key slot and in juxtaposition with the internal surface of the bore 11 in the body 10.

In the embodiment illustrated in Figure 3, the interlocking element is in the form of a peg 24 which, as will be explained, is biassed so that it protrudes some way into the key slot, the biassing being provided by a brass wire spring clip 25. To accommodate the peg 24 and clip 25, the exterior surface of the body 10 is formed with a machined groove 26 which is of generally rectangular cross-section, the groove being contained in a plane normal to the axis of the lock and extending around the whole of the part of the body above the portion thereof in which the bores 16 are formed, as best shown in Figure 7. As can be seen from Figure 3, the axial position of this groove along the length of the body is slightly beyond the final pin tumbler assembly in the direction of key insertion. As will be explained, with the form of key 23 shown in Figure 3, the intention is that the interlocking performed by the peg 24 will only be overcome, to allow cylinder rotation, when the key 23 is fully inserted to its correct position, as shown in Figure 3, i.e with the pin 1 7 of the final pin tumbler assembly being received in its associated complete notch in the 'front' edge of the blade of the key.

As shown in Figure 6, a circular section bore 27 extends radially through the body 10 from the bottom of the groove 26 at the apex of the body, with the body being positioned as shown in Figures 3 and 7. As can be seen from Figure 6, the diameter of the bore 27 is slightly greater than the width of the groove 26, the groove being locally enlarged laterally at the position of the bore 27, so that an annular ledge 28 is formed around the top of the bore 27 within the groove 26.

The one-piece peg 24 has a lower cylindrical part 29 which may be slightly chamfered at its free end, and an upper part in the form of a cylindrical flange 30 which has a central diametral generally rectangular slot 31 therein. As can be seen best from Figures 4 and 5, the peg is intended to be fitted to the body 10 with its lower cylindrical part 29 as a close fit in the bore 27 and its flange 30 received in the locally enlarged portion of the groove 26, with the flange resting, in the lower position of the peg shown in Figure 4, on the ledge 28.

The spring clip 25, which is of circular cross-section, as shown in figures 4 and 5, is fitted into the groove 26 around the body 10, the part of the clip at the bore 27 being received in the slot 31 so as to bear upon the peg 24 and bias it to its Figure 4 position in which the flange 30 is forced down on to the ledge 28 with the bottom of the part 29 projecting into the key slot which will be aligned, and thus in communication, with the bore 27 when the cylinder is in its "locked position", i.e with the open end of the key slot being the uppermost end of the cylinder, as shown in Figure 3.

Accordingly it will be appreciated that the projection of the part 29 into the key slot provides an interlock between the cylinder and the body, which prevents relative rotation therebetween. Accordingly, in the example iilustrated, rotation of the cylinder can only occur if an appropriate key 23 is fully inserted into the cylinder, for only upon full insertion will the end of the key reach the part 29 in the key slot, with the 'rear' edge of the blade of the key engaging the chamfer at the free end of the part 29 and forcing the peg 24 upwardly out of the key slot against the biassing of the spring clip 25, so that the peg assumes the position shown in Figure 5 where it is clear of the split line at the bore 27 between the cylinder and the body. Accordingly with the peg 24 held in its Figure 5 position by virtue of its engagement with the blade of the key, cylinder rotation is now possible, the interlock having been released. Once the lock has been actuated, and the key rotated back to its Figure 3 position, it will be appreciated that withdrawal of the key will result in the peg 24 again being forced downwardly to project into the key slot by virtue of the bias of the clip 25, the interlock therefore being restored.

Any attempted rotation of the cylinder without a key is prevented by the peg 24, in that in such a case an edge of the key slot would engage a straight side of the inwardly biassed peg, with the result that rotation forces on the cylinder would be resisted at the peg and would not drive it out of the key slot.

Accordingly there is provided an anti-raking system which does not require the production of a notch or similar weakening of the key, and does not require existing keys and/or locks to be replaced or adapted.

Additionally, the arrangement removes the possibility of any of the disks 20 becoming dislodged from their correct positions in the pin chambers.

Whatever accidental split line may occur during key insertion is irrelevant, since the peg 24 prevents rotation of the cylinder until the key is fully inserted. It will be appreciated that various alternative forms of peg 24 and associated biasing means could be provided. For example, the two elements could be combined into a single integral element, the whole of the element being springy, or just the part thereof which is arranged to move into and out of the key slot. Other means for retaining the interlocking element could be provided without the need for a groove in the outer surface of the body.

Although with a conventional key of the form shown in Figure 3, it is necessary for the interlocking element to be at or downstream of the final pin tumbler set, in order to ensure that the interlock is not released until the last pin has correctly engaged in its intended key notch, it would be possible to position the interlock differently in the body, for example near the front end of the body, if a different form of key were to be used.

For example if the 'rear' edge of the key blade were to be provided with an appropriate groove, extending from the free end of the key blade, it would be possible to position the interlocking element nearer or at the front end of the lock so that upon key insertion the interlock would remain in place whilst the groove in the key blade passes beneath it, the interlock only being released once the key is fully inserted, whereupon the groove runs out and the 'rear' edge of the blade then engages the interlocking element to push it out of the key slot.

In a further alternative, it might be possible for the interlocking element to project sidewardly into the key slot, for example at 90" around the cylinder body from the position shown in Figure 3, with some form of appropriate shaping on the side of the key being provided to displace the interlocking element out of the key slot once the key is fully inserted. As added security, more than one interlocking element of any of the forms described, or of any suitable other form, could be provided.

The lock shown provides both 'anti-rake', in that an appropriate key has to be fully inserted in order for rotation of the cylinder to occur, and 'security' in that rotation of the cylinder is prevented when a key is not inserted, the interlock providing an additional element which would need to be held back in attempted picking of the lock. The biased interlock element would not be driven out of the key slot upon attempted rotation of the cylinder in the event of a picking action on the pin tumblers, in contrast to the first embodiment in the early published specification No. 222305A of our previously mentioned UK Patent No.

2223054B, where the interlock pin can be driven inwards into the cylinder by rotational force applied to the cylinder in the event of picking, and thus provides an 'anti-lock' feature only. This difference is due not only to the biassing of the peg, but to the fact that there is no round or angled surface at the point of contact between the cylinder and the peg, so that attempted rotation of the cylinder without a key cannot drive the peg out of the cylinder. With the abovementioned prior art embodiment, the interlock pin has a rounded outer end which can be engaged by the cylinder upon attempted non-keyed rotation thereof, so as to drive the pin fully into the cylinder, which can then be rotated.

Claims (12)

1. A cylinder lock comprising a body, a cylinder rotatably mounted in the body, a key slot in the cylinder for receiving a key, a plurality of radially extending pins mounted in radial bores in the cylinder and aligned bores in the body, the pins being biased towards the key slot, each pin being split into at least two portions so that the cylinder can be turned only when the interfaces between the pin portions are made by the insertion of an appropriate key to coincide with the surface of the cylinder, at least one of said pins being split into at least three portions so that a plurality of different appropriate keys can be used to turn the cylinder, and an additional interlocking element biased to project from the body into the key slot across said surface of the cylinder so as to obstruct turning of the cylinder unless an appropriate key is fully inserted into said key slot, whereupon the additional interlocking element is moved out of said key slot and clear of said surface of the cylinder, thereby to allow turning of the cylinder by said fully inserted key.

2. A cylinder lock as claimed in Claim 1, wherein the additional interlocking element is mounted on the body.

3. A cylinder lock as claimed in Claim 2, wherein the additional interlocking element is a peg received in a bore extending through the body, the bore being in communication with the key slot when the cylinder is in its locked position.

4. A cylinder lock as claimed in Claim 3, wherein the body has a groove in its external surface, the groove being in communication with said bore in the body and containing a spring clip which acts on the peg to bias it to extend from the body into the key slot.

5. A cylinder lock as claimed in Claim 4, wherein part of the peg is engageable with the body to limit the extent to which it is biased into the key slot.

6. A cylinder lock as claimed in any one of Claims 1 to 3, wherein the peg is part of an inherently springy element by means of which said peg is biased into the key slot.

7. A cylinder lock as claimed in any one of Claims 1 to 3 or Claim 6, wherein the additional interlocking element is engageable with the body to limit the extent to which it is biased into the key slot.

8. A cylinder lock as claimed in any one of the preceding claims, wherein the additional interlocking element is arranged beyond the final pin in the direction of key insertion into the cylinder.

9. A cylinder lock as claimed in any one of Claims 1 to 8, wherein the additional interlocking element is arranged at or forward of the final pin in the direction of key insertion into the cylinder, but is engaged so as to move clear of said cylinder surface only upon full insertion of the key into the key slot.

10. A cylinder lock as claimed in any one of the preceding claims, wherein said additional interlocking element moves in a bore in the body having a central axis in the plane containing the respective central axes of said aligned bores in the body.

11. A cylinder lock as claimed in any one of Claims 1 to 9, wherein said additional interlocking element moves in a bore in the body at an angle other than 1800 to said aligned bores in the body.

12. A cylinder lock as claimed in any one of Claims 1 to 8, in combination with a key having a shank with grooves to be engaged by said pins in its one face and a straight, continuous surface as its opposite face arranged to lie flush with the open end of the key slot when the key is inserted into said key slot in use.

1 3. A cylinder lock substantially as hereinbefore described, with reference to, and as shown in Figures 3 to 10 of the accompanying drawings.