FIELD OF THE INVENTION

The present invention relates to door lock assemblies and more particularly to door lock assemblies providing key access from only one side of the door.

BACKGROUND OF THE INVENTION

There exist various door lock applications wherein it is desired that the lock be key operated from one side and knob operated from the other side. For example, certain safety regulations require that a door be able to be unlocked from the inside without the use of a key.

It is well known to adapt single cylinder door locks for this purpose. Normally pinless cylinders are used for this purpose. It is not known to adapt double cylinder door locks for this purpose.

SUMMARY OF THE INVENTION

The present invention seeks to provide a door lock having selectable and changeable knob operation on one side thereof.

There is thus provided in accordance with a preferred embodiment of the present invention a door lock having selectable and changeable knob operation including a lock housing defining at least one bore in which is rotatably mounted a plug defining a keyway, the lock housing and the plug including a plurality of tumbler pins, a knob assembly including a handle portion fixed to a key portion which is configured with respect to the tumbler pins such that when the key portion is fully inserted into the keyway, the tumbler pins are aligned so as to permit rotation of the plug, a selectably position- able locking element located in the plug in communication with the keyway and apparatus for selectably locking the locking element in locking engagement with the key por¬ tion, thereby to prevent removal of the knob assembly from the keyway.

There is also provided in accordance with a preferred embodiment of the present invention a double cylinder door lock having selectable and changeable knob operation on one side thereof including a lock housing defining a pair of bores in which are rotatably mounted respective plugs defining keyways, the lock housing and the plugs including a plurality of tumbler pins which are positioned by a key inserted into one of the keyways, a knob assembly including a handle portion fixed to a key portion which is configured with respect to the tumbler pins such that when the key portion is fully inserted into the keyway, the tumbler pins are aligned so as to permit rotation of the plug, a selectably positionable locking element located in the plug in communication with the keyway and apparatus for selectably locking the

locking element in locking engagement with the key por¬ tion, thereby to prevent removal of the knob assembly from the keyway.

In accordance with a preferred embodiment of the invention, the selectably positionable locking ele¬ ment is a ball which is located within a bore extending transversely through the plug with respect to the keyway and intersects the keyway. The key portion is formed with a recess to receive part of the locking element when the key is fully inserted into the keyway.

Preferably, the apparatus for selectably lock¬ ing comprises a set screw accessible from the outer face of the plug.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood more fully from the following detailed description, taken in conjunction with the drawings in which:

Fig. 1 is a partially exploded view pictorial illustration of a double cylinder door lock constructed and operative in accordance with a preferred embodiment of the present invention;

Figs. 2A and 2B are sectional illustrations taken along lines II - II in Fig. 1 showing a portion of the lock in two alternative operating orientations;

Figs. 3A and 3B are respective pictorial and sectional illustrations of the double cylinder door lock of Figs. 1 - 2B fully assembled; and

Figs. 4A and 4B are respective pictorial and sectional illustrations of a door lock according to another preferred embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Reference is now made to Fig. 1, which illus¬ trates a double cylinder door lock having selectable and changeable knob operation on one side thereof, construct¬ ed and operative in accordance with a preferred embodi¬ ment of the present invention. The door lock preferably may be essentially a conventional double cylinder door lock, such as one commercially available from Mul-T-Lock Ltd. of Yavne, Israel under catalog number 80070002 including a lock housing 10 defining a pair of bores 12 in which are rotatably mounted respective plugs 16 defin¬ ing keyways 18.

As seen by additional reference to Figs. 2A, 2B, 3A and 3B, the lock housing 10 and each plug 16 include a plurality of tumbler pins 20.

In accordance with a preferred embodiment of the present invention, in contrast to the prior art, there is provided a knob assembly 22 including a handle portion 24 fixed to a key portion 26 by means of a set screw 27. The key portion 26 is configured with respect to the tumbler pins 20, with key combinations identical to those of an ordinary key, such that when the key portion 26 is fully inserted into the keyway 18, the tumbler pins 20 are aligned so as to permit rotation of the plug 16.

Further in accordance with a preferred embodi¬ ment of the present invention and distinct from the prior art, the plug 16 is provided with a bore 28 extending transversely with respect to the keyway 18 into engage¬ ment therewith. A selectably positionable locking ele¬ ment, typically a ball 30 is located in the bore 28 in communication with the keyway 18. An additional bore 32, preferably threaded, is formed in plug 16, extending inwardly from a front face 34 thereof. A set screw 38 is selectably positioned in bore 32 for selectably locking

the ball 30 in locking engagement with the key portion 26, thereby to prevent undesired removal of the knob assembly 22 from the keyway 18.

In accordance with a preferred embodiment of the invention, the key portion 26 is formed with a recess 40 to receive part of the ball 30 when the key portion 26 is fully inserted into the keyway 18.

Fig. 2A illustrates a normal operating arrange¬ ment when the knob assembly 22 is locked within keyway 18. It cannot be disengaged from the keyway except by repositioning of the set screw 38. In accordance with a preferred embodiment of the present invention, the lock of the present invention may be easily converted for ordinary key use from both sides, simply by retracting the set screw 38 to an orientation shown in Fig. 2B, whereby ordinary keys, with or without recess 40 may be inserted into the keyway and removed therefrom for opera¬ tion of the lock.

It is a particular feature of the present invention that when the knob assembly 22 is locked within keyway 18, as shown in Figs. 3A and 3B, disengagement of the knob assembly requires displacement of both set screws 27 and 38, since the handle portion 24 of the knob assembly 22 blocks access to set screw 38 via aperture 32 in plug 16.

Accordingly, the knob assembly 22 is not easily disengaged from door lock and lost, since first, the handle portion 24 must be removed and only then can the set screw 38 be displaced to allow the remainder of the knob assembly 22 to be removed from the keyway.

Reference is now made to Figs. 4A and 4B, which illustrate a single cylinder door lock having selectable and changeable knob operation, constructed and operative in accordance with a preferred embodiment of the present invention. The door lock preferably may be essentially a conventional cylinder door lock, such as one commercially

available from Mul-T-Lock Ltd. of Yavne, Israel under catalog number 85170060 including a lock housing 50 defining a bore 52 in which is rotabably mounted a plug 56 defining a keyway 58. The lock housing 50 and the plug 56 each include a plurality of tumbler pins 60.

In accordance with a preferred embodiment of the present invention, in contrast to the prior art, there is provided a knob assembly 62 including a handle portion 64 fixed to a key portion 66 by means of a set screw 67. The key portion 66 is configured with respect to the tumbler pins 60, with key combinations identical to those of an ordinary key, such that when the key portion 66 is fully inserted into the keyway 58, the tumbler pins 60 are aligned so as to permit rotation of the plug 56.

Further in accordance with a preferred embodi¬ ment of the present invention and distinct from the prior art, the plug 56 is provided with a bore 68 extending transversely with respect to the keyway 58 into engage¬ ment therewith. A selectably positionable locking ele¬ ment, typically a ball 70, is located in the bore 68 in communication with the keyway 58. An additional bore 72, preferably threaded, is formed in plug 56, extending inwardly from a front face 74 thereof. A set screw 78 is selectably positioned in bore 72 for selectably locking the ball 70 in locking engagement with the key portion 66, thereby to prevent undesired removal of the knob assembly 62 from the keyway 58.

In accordance with a preferred embodiment of the invention, the key portion 66 is formed with a recess 80 to receive part of the ball 70 when the key portion 66 is fully inserted into the keyway 58.

In accordance with a preferred embodiment of the present invention, the lock of the present invention may be easily converted for ordinary key use from both sides, simply by retracting the set screw 78 to an orien-

tation shown in Fig. 2B, whereby ordinary keys, with or without recess 80 may be inserted into the keyway and removed therefrom for operation of the lock.

It is a particular feature of the present invention that when the knob assembly 62 is locked within keyway 58, as shown in Figs. 4A and 4B, disengagement of the knob assembly requires displacement of both set screws 67 and 78, since the handle portion 64 of the knob assembly 62 blocks access to set screw 78 via aperture 72 in plug 56.

Accordingly, the knob assembly 62 is not easily disengaged from door lock and lost, since first, the handle portion 64 must be removed and only then can the set screw 78 be displaced to allow the remainder of the knob assembly 62 to be removed from the keyway.

It will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described hereinabove. Rather the scope of the present invention is defined only by the claims which follow: