Title:
PICK-PROOF LOCK
United States Patent 3787812
Abstract:
A pick-proof lock for use with a key having a double bitting. First means is included for reading the first bitting. Second means is included for reading the second bitting to open the lock only when the first bitting reading means and second bitting reading means are enabled by a key having the proper bittings. Unlocking preventing means prevents unlocking of the lock until the second bitting reading means is enabled. Responsive means disables the unlocking preventing means when the second bitting reading means is enabled.


Inventors:
ARMSTRONG W
Application Number:
05/190905
Publication Date:
01/22/1974
Filing Date:
10/20/1971
Assignee:
The Waterbury Pressed Metal Company (Waterbury, CT)
Primary Class:
Other Classes:
70/278.3, 70/283, 200/43.08, 340/5.31, 340/5.67, 340/542
International Classes:
E05B27/00; E05B45/10; E05B47/06; (IPC1-7): E05B47/00; E05B45/10
Field of Search:
70/277,278,282,283,356,358,416,419,421,DIG.49 2
View Patent Images:
US Patent References:
3670538CONTROLLABLE KEY LOCK1972-06-20Curry
3599454KEY READER AND IDENTIFIER SYSTEM1971-08-17Hill et al.
3500326MECHANICALLY PROGRAMMED ENCODER SYSTEM1970-03-10Benford
3494157MAGNETIC LOCK1970-02-10Coker
3415087Electromechanical lock1968-12-10Kramasz et al.
3194034Cylinder lock1965-07-13Leiser
2475220Electric key lock1949-07-05Chaulk et al.
2057301Combined lock and switch1936-10-13Golokow et al.
1435682Lock1922-11-14Allain
0421205N/A1890-02-11
Primary Examiner:
Craig Jr., Albert G.
Attorney, Agent or Firm:
Davis, Hoxie, Faithfull & Hapgood
Claims:
1. A lock of the type having a rotatable cylinder arranged within a housing and tumblers extending into the key slot of the cylinder to receive the biting of a key, wherein the improvement comprises:

2. A lock as claimed in claim 1 including:

3. A pick-proof lock comprising:

4. A pick-proof lock as claimed in claim 3 including:

5. A pick-proof lock comprising:

6. A lock of the type having a rotatable cylinder arranged within a housing and tumblers extending into the key slot of the cylinder to receive the bitting of a key, wherein the improvement comprises:

Description:
The present invention relates to locks and more specifically, to a pick-proof lock for use with a key having a double bitting.

Various devices known in the art have been used with locks for actuating alarms to indicate attempts at improper access. For example, U.S. Pat. No. 3,427,413 and 2,057,301 disclose the utilization of electric switches with locks having standard pin tumblers for actuating an alarm to signal an attempt at improper access. However, none of the prior art devices disclose a pick-proof lock for actuation by a key having a double bitting.

It is an object of the present invention to provide a pick-proof lock.

It is a further object of the present invention to provide a lock for use with keys having double bittings to enhance the number of different key changes possible.

It is a further object of the present invention to provide a pick-proof with alarm signal means.

Briefly, the pick-proof lock of the present invention includes a first means for reading the first bitting and a second means for reading the second bitting to open the lock only when the first bitting reading means and second bitting reading means are enabled by a key having the proper bittings. Unlocking preventing means prevents unlocking of the lock until the second bitting reading means is enabled. Responsive means disables the unlocking preventing means when the second bitting reading means is enabled.

Other objects, aspects and advantages of the present invention will be more fully understood when the detailed description is considered in conjunction with the drawings as follows:

FIG. 1 is a partial sectional view of a pick-proof lock according to the present invention;

FIG. 2 is a top plan view of the lock of FIG. 1; and

FIG. 3 is a schematic diagram illustrating one possible circuit arrangement for the enabling switch, the alarm actuating switches, and the alarm circuitry, in use with a key having the improper bitting.

Referring to FIGS. 1 and 2, the pick-proof lock 10 includes a housing 12 having a recess 13 and a cylinder or barrel 14 positioned in the recess 13 for rotational movement therein in a conventional manner.

A first bitting reading means or tumblers 16 are positioned in the housing 12, e.g. by springs (not shown), and extend into bores 18 arranged in the cylinder 14 transversely to the direction of longitudinal key slot 20. A key 22 having the proper bitting 21 will, upon insertion into slot 20, move the tumblers 16 upward to the desired position for enabling the barrel 14 to rotate.

Disposed 180° opposite to the tumblers 16 is a second bitting reading means or plungers 23 positioned for reciprocating movement in housing 12 and extending into bores 24. The plungers 23 are in contact with microswitches 25 and act to open or close the microswitches 25 in response to a key 22 having the proper second bitting 26. An additional plunger 27 is arranged at the opposite end of slot 20 for actuation of microswitch 28.

Microswitch 28 which may be arranged to be normally closed is opened by the downward movement of plunger 27 when engaged by the end 30 of the second bitting 26. The plunger 27 thus in a sense reads the length of the key 22 to determine if the key 22 is of the proper length.

As shown in FIG. 3, a solenoid 32 is electrically connected in series with the terminals of microswitches 25A, 25B, 25C, 25D and 28 to a source of power, shown as a battery 34. (The terminals are designated as normally open [NO], common [C], and normally closed [NC].) Utilizing the proper key 22 having the proper bit length and second bitting 26 will open microswitch 28 and close normally open microswitches 25C and 25D and open normally closed microswitches 25A and 25B allowing the solenoid 32 to be energized. Energization of the solenoid 32 retracts movable core arm 36 from core slot 38, allowing the barrel 14 to rotate to retract a bolt (not shown) for unlocking the door, see FIG. 2.

Further, a conventional bell alarm 40 and relay 42 may be electrically connected to the second bitting reading means for actuation should the microswitches 25 be partially actuated by having one or more of the microswitches improperly opened or closed, e.g., by insertion of a key having the improper bitting. As shown in FIG. 3, microswitch 25C remains in a normally open state due to use of a key with the improper bitting 26 thereby preventing energization of the solenoid 32 and also causing energization of the alarm 40.

In the normal, inoperative, position the tumblers 16 and plungers 23 and 27 extend into the cylinder 14 and the core arm 36 is positioned within the core slot 38 to prevent rotation of the cylinder 14 within the housing 12 and unlocking of the lock. When a key having the proper bittings 21 and 26 is inserted into the key slot 20, the tumblers 16 move upward in bores 18, thereby enabling the first bitting reading means. Further, the required plungers 23 and 27 are also depressed, thereby closing microswitches 25 and 28 and enabling the second bitting reading means. The lock 10 is opened by simply rotating the key 22 and barrel 14 as with conventional locks.

At least one of the microswitches 25 and 28 should be normally open. When a key 22 having the proper bitting 26 is inserted into the key slot 20 the end 30 of the key 22 will be read by microswitch 28. The desired microswitches 25 and 28 must all be closed to complete the circuit to the solenoid 32 for retraction of core arm 34 from core slot 36, thereby disabling the core arm 34 and allowing the barrel 14 to rotate within the housing 14 to open the lock.

By arranging the microswitches 25 (shown as four in the drawing) and microswitch 28 in open or closed positions, 70 combinations are proper, thereby multiplying the conventional number of key combinations by 70.