GB2295191A

GB2295191A - Protective shield for radial pin tumbler locks

Info

Publication number: GB2295191A
Application number: GB9423384A
Authority: GB
Inventors: Frederick Nigel Milbank
Original assignee: Milenco Ltd
Current assignee: Milenco Ltd
Priority date: 1994-11-19
Filing date: 1994-11-19
Publication date: 1996-05-22
Anticipated expiration: 2014-11-19
Also published as: GB2295191B; GB9423384D0

Abstract

A shield device prevents unauthorised access to an RPT lock 1 by surrounding the exposed parts of the head 6 of the lock 1 with a skirt portion 23 and a face portion 22. The face portion 22 has a round aperture 26 the same size as and aligned with the key hole (not shown) to allow access by a key. In one embodiment (figure 2) the shield is mounted inside a collar 30 which is permanently fixed to a welding plate 3 to allow the shield to be rotatable relative to the lock 1. In a second embodiment (figure 4) the shield is secured beneath a permanently fixed cover plate 40 which contains an aperture 41 through which a raised portion 25 of the face portion 22 protrudes so that the shield is rotatable relative to the lock 1 and the cover plate 40. The shield is made from a material with a surface hardness of at least Rockwell 55 C. <IMAGE>

Description

Lock The present invention relates to a lock and to a device for improving the security of a radial pin tumbler lock.

Radial pin tumbler locks (RPT locks) are commonly used in applications such as vending machines, steering wheel locks and launderette equipment. They offer a relatively high level of security at a low cost.

Members of the Master Locksmith Association in the UK have recently developed a technique for overcoming these locks. This technique, which is known as core cutting, involves the use of a device known as a core cutter to cut the face out of the lock. This reveals the pins, which can then be removed, allowing the lock to be opened.

It is an aim of the present invention to improve the security of RPT locks by preventing the use of a core cutter.

According to the present invention there is provided a radial pin tumbler lock having a shield to prevent access to the face of the lock. The shield may be made of a material having a hardness of at least Rockwell 55 C, and preferably at least Rockwell 60 C. The shield may be mounted so as to be rotatable relative to the lock.

Preferably, the shield surrounds the front and sides of the head of the RPT lock. The shield may include mounting means for front loading and/or for back loading.

The shield may include an aperture to allow a key to be inserted into the lock. The aperture may be matched to the size of the key hole in the lock and is preferably within +0.5mm of the outer diameter of the key hole. The shield may include a slot, which may extend radially from the aperture to the outer periphery of the lock.

The present invention also provides a shield for a radial pin tumbler lock. The shield may include any of the features mentioned above.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, of which: Figure 1 shows a front view of an RPT lock having a front-loaded shield; Figure 2 shows a cross-sectional side view, taken along line II-II of Fig. 1; Figure 3 shows a front view of an RPT lock having a rearloaded shield, and Figure 4 shows a cross-sectional side view, taken along line IV-IV of Fig. 3.

Figures 1 and 2 show an RPT lock 1 mounted in an aperture 2 in a plate 3. The RPT lock is entirely conventional and is shown only in outline in Fig. 2. Some features of the lock are, however, shown in Fig. 1.

The lock 1 includes a casing 5 having a rounded head portion 6. A circular bore 8 extends axially through the end face 9 of the head portion 6. The rotatable shaft 12 of the tumbler mechanism is located centrally within the bore 8, forming a circular slot into which the hollow cylindrical barrel of the key fits. The shaft 12 is provided on one side with a notch 13 for engagement with a lug on the inner wall of the key barrel, to allow the shaft to be turned. A second notch 14 is provided in the front face of the lock, to accommodate a second lug on the outer wall of the key. This lug retains the key in the lock as it is turned.

The pins 15, which control locking and unlocking of the lock, are arranged around the drive shaft 12 and are half hidden by the end face 9 of the casing 5. These pins are engaged by the key as it is inserted into the lock and are pushed into the casing exactly the right distance to release the locking mechanism and allow the tumbler mechanism to be turned. These features are entirely conventional and would be well understood by a person with a knowledge of RPT locks.

In the technique known as core cutting, the part of the face that overlaps the pins is cut away by a rotating cutter, so exposing the pins and allowing them to be removed. The lock can then be opened using any key. The present invention precludes access to the face 9 and so prevents the face being cut away.

In the embodiment shown in Figs. 1 and 2, the invention comprises a shield 20 that fits over and encloses the head portion 6 of the RPT lock. The shield 20 is made of high tensile steel, for example that sold under the Trade Mark Hi-Ten Speed 45, and is hardened to a hardness of Rockwell 55-60 C. Alternatively, the shield could be manufactured from a range of other materials such as plastics or ceramics, providing they have sufficient hardness.

The shield 20 includes a disk-shaped face 22 having a peripheral cylindrical skirt 23. A circular raised portion 25 is provided centrally on the face 22 and a circular bore 26 extends axially through the raised portion and the face. The diameter of the bore 26 is matched to the diameter of the bore 8 in the front face of the lock, preferably to within a tolerance of +0.5mum.

It is important that the bore 26 is no larger than necessary, in order to prevent access to the face of the lock.

As can be seen in Fig. 1, a radial slot 28 extends from the bore 26 to the edge of the shield 20. This slot is designed to accommodate the extended grip provided on the keys of many widely available RPT locks. If the key does not have an extended grip, the slot may be omitted. The slot does serve a useful purpose, however, by introducing an intermittent edge which will damage the cutting edge of a very hard cutter, such as a tungsten carbide cutter, that may be used to attack the lock.

The shield 20 is seated within a bezel 30, which is welded or otherwise permanently attached to the plate 3.

The shield is retained within the bezel 30 by a circlip 32 that engages corresponding grooves 34,35 in the outer cylindrical wall of the shield 20 and the inner cylindrical wall of the bezel 30. The shield is rotatable within the bezel, which allows it to turn with the key when the lock is operated. The fact that the shield rotates also improves the security of the lock since it helps to protect the lock from an attack using a drill or a rotating cutter.

In the embodiment shown in Figs. 3 and 4, the shield 20 is exactly as described above, but is mounted using a rear-loading method. In this method, the shield 20 is positioned between the first plate 3 to which the lock 1 is attached and a second cover plate 40, which is permanently attached, for example by welding, to the first plate. The shield is retained in position by the engagement of the raised portion 25 with an aperture 41 in the second plate 40. As in the first embodiment, the shield 20 is rotatable with respect to the lock.

Claims

1. A shield device for an RPT lock comprising a body portion that in use extends through an aperture in a mounting plate, a head portion having an engagement surface that engages a face of the mounting plate and a key hole provided in an end face of the head portion, the shield device comprising a face portion and a skirt portion depending from the periphery thereof, the shield device being arranged to be mounted such that the face portion and the skirt portion surround and protect the exposed surfaces of the head portion, the shield device further including an aperture in the face portion, said aperture being arranged to be aligned in use with the key hole and being matched substantially in size thereto.

2. A shield device according to claim 1, wherein the shield has a surface hardness of at least Rockwell 55 C and preferably at least Rockwell 60 C.

3. A shield device according to claim 1 or claim 2, in which the aperture in the face portion is circular and is equal to the diameter of the key hole to a tolerance of +0.5mm.

4. A shield device according to any one of the preceding claims, in which the aperture includes a radially-extending slot.

5. A shield device according to any one of the preceding claims, the shield device being arranged to be mounted for rotation relative to the lock body.

6. An RPT lock comprising a body portion that extends, in use, through an aperture in a mounting plate, a head portion having an engagement surface that in use engages a face of the mounting plate and a key hole provided in an end face of the head portion, the lock further including a shield device comprising a face portion and a skirt portion depending from the periphery thereof, the shield device being arranged to be mounted such that in use the face portion and the skirt portion surround and protect the exposed surfaces of the head portion, the shield device further including an aperture in the face portion, said aperture being arranged to be aligned with the key hole and being matched substantially in size thereto.

7. An RPT lock comprising a body portion that extends through an aperture in a mounting plate, a head portion having an engagement surface that engages a face of the mounting plate and a key hole provided in an end face of the head portion, the lock further including a shield device comprising a face portion and a skirt portion depending from the periphery thereof, the shield device being mounted such that the face portion and the skirt portion surround and protect the exposed surfaces of the head portion, the shield device further including an aperture in the face portion, said aperture being aligned with the key hole and matched substantially in size thereto.

8. A lock according to claim 7, the lock including a collar member mounted on the mounting plate, the shield device being received within the collar member.

9. A lock according to claim 8, wherein the shield device is mounted so as to be rotatable within the collar member.

10. A lock according to claim 8 or claim 9, including means for retaining the shield device within the collar member.

11. A lock according to claim 7, the lock further comprising a cover plate mounted on the mounting plate, the cover plate including an aperture and the shield device including on its face portion a raised portion that is received with in the aperture in the cover plate.

12. A lock according to claim 11, wherein the shield device is mounted so as to be rotatable relative to the cover plate.

13. A lock according to any one of claims 6 to 12, the lock comprising a shield according to any one of claims 1 to 5.

14. A shield device for an RPT lock, the shield being substantially as described herein with reference to, and as illustrated by, Figs. 1 and 2, or Figs. 3 and 4, of the accompanying drawings.

15. An RPT lock, the lock being substantially as described herein with reference to, and as illustrated by, Figs. 1 and 2, or Figs. 3 and 4, of the accompanying drawings.