Disc tumbler lock and key

Details Disc tumbler lock and key Disc tumbler lock and key

2000-02-15

2004-04-27

Gall, Lloyd A. (Department: 3676)

Locks

Operating mechanism

Key

C070S369000, C070S371000, C070S386000

Reexamination Certificate

active

06725696

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to cylinder locks of the kind having a barrel rotatably mounted in an outer housing or cylinder, and also having key releasable means which functions to hold the barrel against rotation relative to the cylinder when a correct key is not located within the lock keyway. The invention is particularly concerned with such locks in which the key releasable means includes rotatable disc tumblers.
Locks of the foregoing kind are generally of relatively complex construction and include a large number of parts. As a consequence, such locks are relatively expensive to manufacture. Example locks of that kind are the subject of U.S. Pat. No. 4,512,166 (Dunphy 1) and U.S. Pat. No. 4,624,119 (Dunphy 2).
Many locks, including the Dunphy locks, include provision for changing the lock combination. Such a change generally involves removal of the lock barrel assembly and substitution by another barrel assembly which is responsive to a key different to that which operated the original barrel assembly. It is usually the case that the barrel change-over is achieved by use of a special change key, and that key functions in the required manner because of a feature which can be readily identified by visual inspection of the key. By way of example, in the case of the Dunphy lock the relevant feature is a particular configuration at the tip end of the key blade which is clearly observable and is relatively easy to duplicate.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a disc tumbler cylinder lock of relatively simple construction. It is a further object of the invention to provide such a lock having a barrel change-over facility which is of relatively simple form. It is yet another object of the invention to provide a barrel change-over facility which involves use of a special change key having an appearance not significantly different to that of the service key which is used to operate the lock under normal conditions. It is still another object of the invention to provide an improved method of forming a key for use with a disc tumbler cylinder lock. A further object of the invention is to provide an improved key for use with a disc tumbler cylinder lock. A still further object of the invention is to provide a key which is operable to permit removal of a barrel assembly from a cylinder lock and which has an appearance not significantly different to that of the service key for use with the same lock.
A disc tumbler lock according to one aspect of the invention is characterised in that it includes a side locking bar which is cooperable with one or more of the tumbler discs so as to be movable between lock and release positions at which the bar respectively prevents and permits rotation of the barrel assembly relative to the cylinder. When the side locking bar is in the lock position it extends across the separation plane between the lock barrel and the cylinder and thereby prevents rotation of the barrel relative to the cylinder. The bar is preferably held in that lock position by engagement with an outer peripheral surface of at least one of the tumbler discs. Each tumbler disc preferably has a recess in the outer peripheral surface which is adapted to receive part of the locking bar such that the bar can move radially inwards through a distance sufficient to adopt the release position at which the barrel can be rotated relative to the cylinder.
It is preferred that the tumbler discs are arranged in face to face relationship within a tubular sleeve or housing and that there is no intervening component such as a spacer plate between each two adjacent discs, at least in the majority of cases. It is further preferred that adjacent discs are arranged in face to face engagement.
A disc tumbler lock according to another aspect of the invention is characterised in that it includes barrel retention means which when active prevents removal of the barrel assembly from the lock cylinder, and which can be influenced into an inactive condition so as to thereby allow removal of the barrel assembly. It is a feature of the lock that at least one of the disc tumblers controls transfer of the barrel retention means between its active and inactive conditions.
It is preferred that a lock having such barrel retention means includes rotatable disc tumblers, and it is further preferred that the lock includes a side locking bar which is cooperable with one or more of the tumbler discs so as to be movable between lock and release positions at which the bar respectively prevents and permits rotation of the barrel assembly relative to the cylinder.
The tumbler discs may be arranged to respond to insertion of a key in substantially the same manner as the tumbler discs of the Dunphy locks. That is, insertion of the correct service key into the lock keyway causes each of the tumbler discs to adopt a rotational position at which the side locking bar can move to the release position and thereby permit rotation of the lock barrel relative to the cylinder.
The removable barrel assembly is rotatably mounted within a cylindrical bore of the cylinder and is movable axially through one end of that bore during a barrel change-over operation. The barrel retention means which controls the ability of the barrel assembly to be removed from the cylinder may include at least one detent which, when active, coacts between the cylinder and the barrel assembly to prevent axial movement of the barrel assembly through the aforementioned end of the cylinder bore.
It is preferred that at least one of the tumbler discs (hereinafter called the dual function disc) controls the condition of the aforementioned detent. The arrangement is preferably such that the dual function disc permits the detent to adopt the inactive condition when the disc has a particular rotational position (the second function position) relative to the or each other adjacent disc of the barrel assembly. That second function rotational position is preferably different to the rotational position (the service position) adopted by the dual function disc when the correct service key is inserted into the lock keyway.
In standard disc tumbler locks it is usually the case that each disc must have a single predetermined rotational position relative to each other disc in order to enable the barrel to be rotated relative to the cylinder. By contrast, in a lock according to the second aspect of the invention the barrel release disc has two such rotational positions, a first one of which is achieved by use of the correct service key, and the second of which is achieved by use of a special change key. It is preferred that the barrel detent is rendered inactive when the dual function disc adopts the second function rotational position, but remains active when the dual function disc adopts the service rotational position.
According to another aspect of the invention there is provided an apparatus for forming a key for use with a disc tumbler lock and which includes an elongate blade having tumbler indexing sections at locations spaced apart in the longitudinal direction of said blade, and a loping ramp surface between each two adjacent said indexing sections; the apparatus including a rotatable holding device to which a key blank can be releasably secured so that the elongate blade of that blank extends from the device and the longitudinal axis of said blade is substantially coincident with the axis of rotation of said device, forming means operable to treat the longitudinal surface of said blade and thereby form said indexing sections and said ramp surfaces, first drive means operable to cause rotation of said holding device about said axis of rotation, second drive means operable to cause relative movement between said device and said forming means in the direction of said axis of rotation, and control means operable to control the operation of each said drive means in accordance with a pre-selected sequence of operations which includes, operating said first and second drive means between each two successive indexing

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