High security electronic combination lock

• US 6,741,160 B1
• Filed: 10/18/1999
• Issued: 05/25/2004
• Est. Priority Date: 10/20/1998
• Status: Expired due to Term

• Current Assignee: Kaba-Mas Corporation
• Original Assignee: Kaba-Mas Corporation
• Inventors: Thompson, Daniel L., Dawson, Gerald L., Stallard, Lee
• Primary Examiner(s): Crosland, Donnie L.
• Application Number:
  US09/419,948
• Time in Patent Office: 1,681 Days
• Field of Search: 340/5.55, 340/5.2, 340/5.24, 340/5.22, 340/5.67, 340/5.73, 340/542, 340/5.7, 702/62--64, 702/86, 703/15, 703/32, 702/784, 341/35
• US Class Current: 340/5.55
• CPC Class Codes: G07C 9/00666 with dials
• CPC Class Codes: G07C 9/00912 for safes, strong-rooms, vaults or the like
• CPC Class Codes: Y10T 70/7085 Using a dial having indicia or pointer and indicia
• CPC Class Codes: Y10T 70/7418 Dials

Abstract

An electronic combination lock having a knob which has no divisions or markings relating to the numbers of the combination thereon. The rotation of the knob drives a generator, which produces electrical power. The power generated serves as a power source for the electronics of the lock. A knob position detector indicates to the microprocessor the speed and amount of rotation of the knob. The timing capabilities of the lock provides the opportunity to set the minimum time that can be used in the entering of the combination. The lock waits a period of time, typically, two seconds between the entry of one element of the combination and the lock permitting the entry at the next element of the combination. The microprocessor will also keep a count record of all the failed attempts to open the lock since the last successful operation. If the numbers of tries or attempts to unlock the lock equals or exceeds the number set in the microprocessor microcode, the lock will fail to open even if an authorized combination is subsequently entered. After an error indication is displayed, the lock is disabled to prevent further entry tries, until the lock is reset. In order to eliminate the possibility of correlation between the number displayed and/or entered and knob position, there is a random time delay between the start of knob rotation and the incrementing the number displayed.

Claims

1. An electronic combination lock comprising:

a knob;

a knob rotation detector, said detector senses rotation of said knob;

a bolt;

a display; and

an electronic circuit, said circuit receives a knob rotation signal from said knob rotation detector, said circuit converts said knob rotation signal into a display number, said circuit stores said display number as a combination number in memory, upon receiving a signal indicating reversal of said knob before said knob rotates to select a subsequent combination number said circuit recalls said combination number from said memory and updates said display with said combination number, said circuit updates said display number as said knob rotates until said combination number is stored, said circuit combines one or more combination numbers into an entered combination, said circuit compares said entered combination with an authorized combination, upon said entered combination comparing equal to said authorized combination said circuit enables said bolt to be withdrawn and said lockopened.

2. A method for preventing unauthorized opening of an electronic combination lock, said method comprising:

entering a combination;

comparing said entered combination with an authorized combination;

upon said entered combination comparing equal to said authorized combination, resetting an error counter;

upon said entered combination failing to compare equal to said authorized combination, incrementing said error counter; and

upon said error counter reaching a predetermined number, preventing said lock from opening until a reset combination is entered that resets the error counter.

3. A method for decorrelating knob position from the number displayed when entering a combination into an electronic lock, said method comprising:

conditioning said lock to accept entry of said combination;

rotating said knob; and

delaying incrementing said number displayed for a random time period.

4. A method for correcting a combination entered into an electronic lock;

said method comprising;

rotating a knob until a desired number is indicated on a display;

entering said desired number as part of said combination;

before entering a next number of said combination, reversing rotation of said knob and recalling said entered number to said display; and

rotating said knob until a correct number is indicated on said display.

5. An electronic combination lock comprising:

a knob;

a knob rotation detector, said detector senses rotation of said knob;

a bolt;

an electronic control circuit, said circuit receives a knob rotation signal from said knob rotation detector, said circuit converts said knob rotation signal into an entered combination, said circuit compares said entered combination and an authorized combination, when said entered combination compares equal to said authorized combination said circuit resets an error counter and enables said bolt to be withdrawn and said lock opened, upon a failure of said entered combination comparing equal to said authorized combination said circuit increments said error counter, when said error counter reaches a predetermined number said circuit prevents said lock from opening until a reset combination is entered that resets said error counter.

6. An electronic combination lock comprising:

a knob;

a knob rotation detector, said detector senses rotation of said knob;

a bolt;

a display;

an electronic control circuit, said circuit receives a knob rotation signal from said knob rotation detector, said circuit imposes a random time period delay between said dial beginning rotation and updating said display with a combination number, said electronic circuit converts said knob rotation signal into an entered combination, said circuit compares said entered combination with said authorized combination, when said entered combination compares equal to said authorized combination said circuit enables said bolt to be withdrawn and said lock opened.