Patent Publication Number: US-4369481-A

Title: Electronic lock

Description:
FIELD OF THE INVENTION 
     The present invention relates to an electronic lock. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a new and useful electronic lock comprising means for producing a beam of electromagnetic radiation, a key having a reflecting means for reflecting the beam in a unique pattern and electromagnetic radiation sensitive means responsive to the beam when reflected in the unique pattern for causing the lock to be unlocked. 
     In the embodiment disclosed, the beam produced is a laser beam, and the electromagnetic radiation sensitive means comprises a plurality of light sensitive means located to receive the beam reflected in the unique pattern. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic illustration of the invention. 
     FIG. 2 is a plan view of the key employed in the system of FIG. 1. 
     FIG. 3 is a plan view of the light sensor board of FIG. 1. 
     FIG. 4 illustrates another embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to FIGS. 1-3, the lock comprises an electric door strike 21 movable by a solenoid 23. The solenoid 23 comprises an electrical coil 25 having a core 27 connected to the strike 21. When the solenoid 23 is energized, it moves the strike 21 to an &#34;unlatched&#34; position to move the latch of a door (not shown) out of the jamb and permits the door to be opened. The latch is part of a door knob mechanism in which the knob can be turned only from one side, the side located in the security area. This allows the person in the security area to leave the area without operating the lock. 
     Reference numeral 31 identifies a D.C. power supply and reference numeral 33 identifies a laser capable of emitting a beam of light 34 along a given path when energized. Reference numeral 35 identifies a sensor board which carries a plurality of photo-diodes 37A-37F. The board 35 has a hole 36 formed therethrough to allow passage of the beam 34. Member 39 is a silicon controlled rectifier (SCR). Member 41 is a removable key which carries a light reflecting means 43 and an electrically conductive member 45 the latter of which is adapted to engage electrical contacts 47 and 49 when the key is located in the position shown. 
     The power supply 31 has its plus terminal connected to the laser 33 by way of lead 51. The anode of the SCR 39 is connected to lead 51 by way of lead 53 and the cathode of SCR 39 is connected to one terminal of solenoid 23 by way of lead 55. The other terminal of solenoid 23 is connected to the minus terminal of supply 31 by way of lead 57. The other terminal of the laser 33 is connected to contact 47 by way of lead 59 and contact 49 is connected to lead 57 by way of lead 61. 
     The photo-diodes 37A-37F are secured to board 35 at spaced apart positions and are located in a unique pattern. The diodes are all electrically connected together in series by way of leads 63-67. Diode 37A is connected to lead 51 by way of lead 69 and diode 37F is connected to the gate of SCR 39 by way of leads 71 and 73. A switch 75 is connected between leads 71, 73 and lead 61. 
     Strike 21, solenoid 23, power supply 31, laser 33, board 35, contacts 47 and 49, SCR 39 and switch 75 all are carried by the house or building structure. The strike 21 and solenoid 23 is located in the wall adjacent the door. The laser 33, board 35 and contacts 47 and 49 will be carried by the wall of the house or building and positioned on the exterior to allow them to function as will be described. Power supply 31, SCR 39 and switch 75 will be located in the security area of the house or building. Normally the switch 75 will be open and SCR 39 will be a nonconducting condition. The key 41 is removable and normally will be carried by the user. In use the key 41 will be located as shown such that the electrically conductive member 45 engages contacts 47 and 49. Although not shown, guides will be provided to allow the key 41 to be positioned as shown. When member 45 engages contacts 47 and 49 a circuit is completed to the laser turning it on and causing it to emit a beam 34. The beam passes through aperture 36 of board 35 and strikes light reflecting means 43. Reflecting means 43 preferably is a crystallized substance such as diamond, corundum, etc. The crystal 43 reflects light back in a unique light pattern consisting of several major points of light and many minor points of light. The crystal employed reflects the major points of light in a unique pattern corresponding to the pattern of the diodes as secured to board 35. If the key is the proper one for the lock, each photo-diode will coincide in position with a major point of reflected light. Thus all of the photo-diodes will conduct and current will be applied from the supply 31 to the gate of the SCR 39 by way of the chain of photo-diodes and cause the SCR to conduct. This completes a circuit to the solenoid 23 which moves the strike 21 to the &#34;unlatched&#34; position allowing the door to be opened. The completed circuit is by way of leads 51 and 53, SCR 39, lead 55, solenoid 23 and lead 57. The key may be removed to remove member 45 out of engagement of contacts 47 and 49. The SCR will continue to conduct holding the strike 21 in an unlatched position. When the door is closed it may be locked by closing switch 75. This deactivates the SCR 39 which deenergizes solenoid 23 and allows the strike 21 to move to a latched position whereby the latch of the door is held in place. When it is necessary for a person in the security area to exit through the door, he simply opens the door by turning the door knob on the security side as he would on any other door. 
     If the key employed is not made for the lock, then at some point along the chain of photo-diodes one or more will not have light falling on it and it will have a high resistance. This will prevent the flow of current through the chain of photo-diodes whereby the SCR 39 will not conduct and the strike 21 will not be unlatched. 
     Although the reflecting means 43 was described as a crystal it is to be understood it could be made up of a plurality of small mirrors positioned to reflect light in the unique pattern as defined by the positions of the photo-diodes 37A-37F. The reflecting means 43 also could be made of many small light reflecting flakes embedded in plastic and which would reflect light in a unique pattern. 
     Referring now to FIG. 4, the lock comprises a board 35&#39; having an arrow of photo-diodes. In the board of FIG. 4, the array comprises five rows of photo-diodes with each row having four photo-diodes. The photo-diodes are identified as D1-D20. Switching circuits 1 and 2 are electrically connected to each of the photo-diodes by way of leads 81-89. Also provided are a microcomputer comprising a microprocessor and memory, an analog to digital circuit, a parallel interface, and a keyboard. The lock also comprises the strike 21, solenoid 23, power supply 31, laser 33, key 41, contacts 47 and 49, switch 75 and SCR 39. Leads 69 and 71 will not be employed. The rest of the circuitry will be as shown in FIG. 1, with the output of the microcomputer connected to the gate of the SCR 39. The board 35&#39; does not have the aperture 36 and will be located to the side of the laser beam 34. 
     In use, the key 41 will be positioned such that member 45 engages contacts 47 and 49 to turn on the laser 33. The reflecting means 43 will be positioned such that it will reflect the beam 34 as points of light in a unique pattern on the diodes on the board 35&#39;. The board 35&#39; will be scanned by the system and the binary code which is produced is compared with a code stored in the memory. The areas which receive little or no reflected light from the reflecting means 43 produce a very low voltage current which causes the analog to digital converter to produce a smaller number. The lighted areas create a larger number. As the processor scans each column of the board, it will then proceed to compare the code with those stored in its memory. If the code for a column matches one stored in memory, then the system proceeds to the next column. If the codes of all of the columns of board 35&#39; are matched with those stored in memory, the system applies an output to activate the SCR 39 to release the door latch. If the code for one of the columns is not matched with a code stored in memory, then the SCR will not be activated and the lock will not release the door latch. 
     In a more detailed description of the operation, the lock will go through a number of processes. First, the key is inserted into the lock which turns it on as described above. An interrupt signal is sent to the microprocessor to inform it that a key has been inserted. As soon as the processor has finished with the current task it is performing, it goes to the memory location where instructions and data for the lock are stored. Next it waits for the person operating the lock to punch in a number which identifies his key. Upon receiving the number, the processor sends a signal to the switching circuit 1 which causes it to supply a small current to the first column of photo-diodes. The second switching device then allows the current from the first photo-diode in row one to be applied to the input of the analog to digital converter which then generates a digital output. The output travels through the parallel interface to the microprocessor which compares the number with the first number stored in its memory for that key. If the numbers match up, then the processor instructs the switching circuit 2 to allow the current from the first photo-diode in the second row to go to the analog to digital converter. The process then continues as it did for the first photo-diode and the resulting number is compared with the second number in the computer&#39;s memory, etc. When the last photo-diode in column one has been read then the processor causes the switching circuit 1 to now supply current to the second column of the photo-diodes and the process continues until the last photo-diode in row five has been read. If all the numbers in the memory match up with those supplied by sampling the photo-diode, the computer opens the lock. 
     With this system, it is possible to have many different keys for one lock, as many as the memory space will allow. The codes for the different keys will be stored in different sections of the memory. 
     Since each key could be given a number which corresponds to a section in the memory, it would be possible to delete a key&#39;s code from memory if it were lost or stolen. If new keys were desired, it would be a simple operation to add their codes to the lock&#39;s memory. This could be done by inserting a new key in the lock and allow the system to scan the crystal&#39;s light pattern as reflected on the board 35&#39; and store it in its memory. 
     The electric door strike comprising strike 21 and solenoid 23 is a commercially available device. 
     In the embodiment of FIG. 4, the light sensitive devices were referred to as photo-diodes, however, they could be any type of photo-sensitive devices which could change the voltage of the current going to the analog to digital converter. Such means as photo-resistive devices could be used.