Locks – Special application – For closures
Patent
1998-08-11
2000-09-26
Gall, Lloyd A.
Locks
Special application
For closures
70475, 70477, 70482, 70485, E05B 5504
Patent
active
061229466
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to latches of the kind which are controlled by a key operable lock and which are intended for use on doors and other movable members adapted to close an access opening. It will be convenient to hereinafter describe the invention with particular reference to doors, but the invention has wider application.
BACKGROUND OF THE INVENTION
Latch assemblies for doors commonly include a turn knob or handle which is generally located at the inside of the door and which is rotated to withdraw the latch bolt into its casing. In order to improve the security of such assemblies, manufacturers have included a key operated lock which is operative to releasably hold the turn knob or handle against rotation. Such locks are typically arranged so as to be operated from the inside of the door and are not operable from the outside of the door. In particular, key operation of the latch from the outside of the door will not release the lock. That can lead to serious problems in circumstances where the door needs to be opened urgently from the inside, particularly if the lock key has been misplaced or is not conveniently accessible.
It is an object of the present invention to provide a key controlled latch which can be released from a locked condition by use of a key at the outside of the door or other member with which the latch is used.
A typical latch assembly to which the present invention is applicable includes a casing, a latch bolt movable relative to the casing to adopt either an extended latching position or a retracted release position, a first actuator at an inner side of the assembly which is operable to move the latch bolt to the release position, locking means which is rendered active or inactive by key operation from the inner side of the assembly and which when active renders the first actuator inoperable, and a second actuator at an outer side of the assembly which is operable to move the latch bolt to the release position.
In normal latch assemblies of the foregoing kind operation of the outer or second actuator does not affect the operation of the locking means. That locking means remains active in spite of operation of the outer actuator, and can be rendered inactive only by appropriate and deliberate operation of the locking means from the inner side of the latch assembly. It is usually the case in such prior assemblies that the locking means is key operated. That is, the locking means will generally include a key operated tumbler lock and locking mechanism connected to that lock so as to be influenced by operation of the lock. The second or outer actuator may also include a key operated tumbler lock, but in conventional assemblies of the foregoing kind operation of that lock does not influence operation of the first actuator locking means. The two locks are arranged so that one is operated from the inner side of the assembly and the other is operated from the outer side.
SUMMARY OF THE INVENTION
According to the present invention, a latch assembly of the foregoing kind is characterised in that it includes lock release means which is responsive to operation of the second actuator to render the locking means inactive.
The first actuator will generally include a rotatable knob or handle which is connected to the latch bolt in a known manner so as to be operable to move that bolt into the release position, and the bolt may be spring biased into the latching position. The locking means preferably includes at least one cam controlled detent which is movable between actuator locking and actuator release positions. It is also preferred that the lock release means is operable to influence the detent cam in a manner such that operation of the second or outer actuator causes the detent cam to move to a position corresponding to the actuator release position of the detent. The cam may be spring biased towards that corresponding position, and retaining means may be operable to allow or prevent such movement according to whether or not, respectively, the second actuator i
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patent: 4635453 (1987-01-01), Hart
patent: 4777810 (1988-10-01), Webster
Gall Lloyd A.
Lockwood Australia Pty. Ltd.
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