AU2008100399B4 - High security tumbler lock - Google Patents

Description

00 CKI HIGH SECURITY TUMBLER LOCK FIELD OF THE INVENTION This invention relates to standard pin tumbler locks which can be opened by using a bump key or a pick tool.

BACKGROUND OF THE INVENTION 00oO Locksmiths have known for a long time that it is possible to open 95% of standard pin tumbler locks by using a method referred to as a bump key. A bump key is made by filing or cutting the grooves of a key down to the deepest point.

The bump key is than inserted into the lock tapped with a heavy object and turned at the same time.

Whereas in the past this technique was mainly used by locksmiths to gain entry for clients who were locked out of their premises, knowledge of the technique has proliferated via the internet and there has been a rapid increase in the number of burglaries using the technique. Accordingly lock manufacturers are attempting to design tumbler locks which prevent bump key entry since high security locks which are not susceptible to bumping are much more expensive.

When a bump key is struck the pins of the lock are forced up into their chambers and as they return under the influence of their biasing springs the lock cylinder is able to rotate through the shear plane of the pins thus opening the lock.

Accordingly stop bump designs attempt to prevent at least one pin being bumped up into its chamber so that the break between top and lower pin cannot pass the shear plane.

For example the lock disclosed in NL1029046C breaks one of its pins into three sections rather than the conventional two upper and lower sections. WO 01/48340 discloses a lock in which the upper and lower pins have a locking 00 C mechanism. US 2005/0022568 teaches a similar lock in which an engagement O mechanism locks the upper driving pin and the lower tumbler pin together thereby blocking the shear line and preventing rotation of the cylinder.

HK 1093659 and US 11/925369 disclose an anti-bump lock in which the upper driver pin and the lower tumbler pin are magnetized and so remain locked when bumped and can only be separated by the turning force of the key when their junction is in the shear plane of the cylinder. However none of these methods of 00oO 0locking upper driver and lower tumbler pins together consistently prevent C 10 bumping every time a bump key is used.

OBJECT OF THE INVENTION It is therefore an object of the present invention to provide a tumbler lock which is more secure than prior art locks or at least provides a useful alternative.

STATEMENT OF THE INVENTION According to the present invention a stop bump tumbler lock comprises an outer body housing an inner cylinder which has a longitudinal keyway and one or more chambers transverse to the keyway and extending into the outer body each of which chambers contains a pair of inline pins biased into the keyway by a spring retained in the chamber such that when the correct key is inserted in the keyway the junction between each pair of pins is moved into the shear plane between the inner cylinder and the outer body of the lock and in which at least one pair of pins has a shortened biasing spring which is attached to the end of the chamber.

Alternatively at least one pair of pins has engagement means for keeping them together but allowing separation by the turning force of the key when the junction is in the shear plane and in which the biasing spring is retained in the body of the lock and attached to the end of the nearest pin.

1 00 c Preferably engagement is achieved by magnets.

Preferably the outermost end of the biasing spring is a press fit into the end of the chamber.

Cc Preferably the end of the outer pin and the innermost end of the biasing spring Sare reduced to provide a press fit between the two.

00 BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the invention is now described by way of example only with reference to the accompanying drawings in which: Fig 1 is a longitudinal cross section of a standard tumbler lock with a typical key Fig 2 is a longitudinal cross section of the subject tumbler lock with a bump key Fig 3 is the lateral cross section AA of Fig 2 in the locked position Fig 4 is the lateral cross section AA of Fig 2 in the unlocking position Fig 5 is the lateral cross section AA of Fig 2 in the unlocked position and Fig 6 is Fig 2 inverted.

DETAILED DESCRIPTION OF THE INVENTION Fig 1 illustrates a standard tumbler lock 1 with six chambers 2 containing six sets of upper driver pins 3 and lower tumbler pins 4 biased against cylinder 5 by springs 6. Key 7 has grooves 8 cut so that when inserted in keyway 9 of cylinder pins 4 are pushed upwards so that the break between pins 3 and 4 are all in line in shear plane 10 between cylinder 5 and lock 1. Accordingly when key 7 is turned cylinder 5 rotates in lock 1 unlocking the latch (not shown).

Fig 2 shows a tumbler lock modified in accordance with the present invention with fifth chamber 2 from the front of lock 1 containing driver pin 13 and tumbler 00 C pin 14 with magnetic ends 12 at their junction. Also spring 16 and pin 13 are c modified so that the reduced end of spring 16 grips reduced end 11 of pin 13.

Opposite end 15 of spring 16 is enlarged and wedged into top of chamber 2.

Bump key 17 has all its grooves 18 cut to the lowest groove point. In order to bump standard lock 1 open, key 17 is inserted fully into keyway 9 and struck with t' an object like a screw driver handle and at the same time turning pressure is Sapplied to key 17. The impulsive force of the bump is transmitted to all pins 3 and 00 4 which move upwards in chambers 2 against the biasing force of springs 6. As they return under the force of springs 6 the breaks between pins 3 and 4 encounter shear plane 10 and key 17 rotates cylinder 5 thus unlocking the latch (not shown).

The detail of this unlocking action is illustrated in Figs 3, 4 and 5. Fig 3 shows pins 13 and 14 in the locked position with keyway 9 clear. Fig 4 shows standard key 7 inserted in keyway 9 thus raising pins 13 and 14 so that their junction is in shear plane 10. Fig 5 shows cylinder 5 rotated in lock 1 with pins 13 and 14 separated. Clearly pins 13 and 14 have to separate to allow rotation of cylinder The prior art locks discussed above attempt to stop bumping by providing engagement means between pins 3 and 4 so that they are locked together and can not be separated at shear plane 10 by the turning pressure on key 17 as pins 3 and 4 return to their biased position after the bump. HK 1093659 attempts to achieve this with magnets similar to magnetic ends 12 of pins 13 and 14.

However this magnetic locking and the other forms of engagement between pins 3 and 4 are not strong enough to prevent rotation of cylinder 5 and so do not prevent bumping.

The subject invention does however prevent bumping in the following way. When key 17 is struck pins 13 and 14 do not move upwards under the transmitted bump force because they are suspended by their shortened spring 16 and are thereby isolated from the bump. Pin 13 continues to pass through shear plane 00 Sand prevents cylinder 5 from rotating despite the turning pressure on key 17 Ct during the bump. Accordingly the subject invention does not rely simply on magnetic engagement between pins 13 and 14 to prevent turning of cylinder but only to keep pins 13 and 14 together. The strength of integral pin 13 is what prevents turning of cylinder Cc In fact there is an alternative embodiment of the subject invention which eliminates magnetic ends 12 of pins 13 and 14 altogether. In Europe cylinder 00 locks are usually installed in the orientation shown in Fig 6 which is an inversion of that in Australia and the USA. Accordingly pins 13 and 14 are maintained conjoined by the force of gravity and no magnets nor any other form of engagement is required. Shortened spring 16 alone is required to remove pin 14 from the influence of the bump. Further spring 16 and pin 14 do not have to be modified to hold pin 13 away from keyway 9 since the force of gravity does this.

It will be clear that the simple modifications to a standard tumbler lock according to the present invention result in a lock which can be manufactured for the same cost as the standard lock. This cost is much less than that of existing high security locks based on more complex mechanisms which prevent bumping. In particular the inverted version of the subject lock is different only in one shortened spring and will cost the same as the current standard.

VARIATIONS

It will be realized that the foregoing has been given by way of illustrative example only and that all other modifications and variations as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of the invention as herein set forth. Throughout the description and claims of this specification the words "comprise" and variations of that word such as "comprises" and "comprising" are not intended to exclude other additives components integers or steps.

Claims (5)

1. A stop bump tumbler lock comprises an outer body housing an inner cylinder which has a longitudinal keyway and one or more chambers transverse to the keyway and extending into the outer body each of which chambers contains a pair of inline pins biased into the keyway by a spring retained in the chamber such that when the correct key is inserted in the 00 0keyway the junction between each pair of pins is moved into the shear N 10 plane between the inner cylinder and the outer body of the lock and in which at least one pair of pins has a shortened biasing spring which is attached to the end of the chamber.

2. The lock of claim 1 in which the at least one pair of pins has engagement means for keeping them together but allowing separation by the turning force of the key when the junction is in the shear plane and in which the biasing spring is retained in the body of the lock and attached to the end of the nearest pin.

3. The lock of claim 2 in which engagement is achieved by magnets.

4. The lock of claim 2 in which the outermost end of the biasing spring is a press fit into the end of the chamber.

5. The lock of claim 2 in which the end of the outer pin and the innermost end of the biasing spring are reduced to provide a press fit between the two.