Programmable key and improved lock assembly

An improved key and lock assembly in which an electronically coded circuit is embedded in the handle of a conventional key and at least one electrical terminal extends from the handle adjacent to and electrically isolated from the key shank so as to contact a similarly located and biased terminal on the lock assembly when the key is fully inserted therein.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present inventions relates to the field of security devices and more 
specifically to the area of key locks. 
2. Description of the Prior Art 
Recently, several concepts have been patented in which a conventional 
tumbler actuating key is combined with an auxiliary coding mechanism in 
order to provide a higher degree of security by increasing the number of 
codes beyond those available on conventional tumbler actuated keys. 
In U.S. Pat. No. 4,200,227, a conventional tumbler actuating key is 
described as containing a coded electrical circuit that is responsive to 
short wave radiation. The circuit is embedded within a plastic assembly 
that is welded or otherwise bonded to the key handle so that the 
electrical circuit is isolated away from the surface of the key. 
In U.S. Pat. No. 4,298,792, a conventional key is shown as containing a 
coded track along its shank. The key is shown to contain a single code 
track composed of alternating light and dark fields that are read by 
sensors in the vicinity of the receiving aperture of the lock. The sensors 
read the track as the key is inserted into the lock. 
In U.S. Pat. No. 4,366,466, the use of a conventional key is described, 
which additionally includes a housing for a data carrier. The data carrier 
is described as containing information on, for example, a recording tape, 
a recording wire, an optically scannable medium or other conventional 
medium. The data carrier is further said to include either an unerasable 
portion containing data reflecting vehicle-related information or an 
erasable portion containing arbitrary information. 
SUMMARY OF THE INVENTION 
The present invention is considered an improvement over the prior art keys. 
It utilizes a tumbler actuatable shank cut to correspond to the unlocking 
tumbler configuration of a corresponding lock. The handle portion of the 
key contains an electrical terminal extending therefrom so as to be 
adjacent and electrically isolated with respect to the shank. An 
electrical coding circuit is embedded within the handle and connected to 
the electrical terminal adjacent the shank. In the described embodiment, 
the key shank serves as one electrical terminal connected to the 
electrical coding circuit within the key handle and two electrical 
terminals are shown to extend from each side of the handle adjacent the 
shank. The two electrical terminals adjacent the shank are commonly 
connected within the handle so that the key may be inserted into the lock 
in either of two orientations for a double cut key. 
The lock mechanism is further improved to include a biased electrical 
terminal configured to mate with the electrical terminal extending from 
the handle on the key and electrical conductors to provide interconnection 
between the biased electrical terminal and an connector for communication 
to the security system control module (not shown) of the vehicle.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
In FIG. 1, the improved key 10 and the improved lock assembly 20, which 
embody the present invention, are illustrated. The key 10 includes a 
conventional cut shank 14 preferably of steel or brass in a double cut 
pattern. A handle portion 12 is formed at the upper end of the shank 14 
and contains an electronically coded circuit 100 embedded therein. 
Electrical terminals 16 and 18 are shown provided as extending from the 
handle 12 adjacent to and electrically isolated from the shank 14. 
The lock assembly 20 includes an electrically isolated receptacle end 21 
with an aperture 24 and an opening 23 for receiving the shank 14 of the 
key 10 when inserted therein. Provided the cuts on the shank 14 conform to 
the tumbler arrangement within the lock mechanism 20, the shank 14 will 
continue to be inserted fully into the body 22 of the lock 20. Upon full 
insertion, the electrical terminal 16 and 18, as well as the leading edge 
of the handle 12 will be received into the opening 23. If the key is 
inserted as shown in FIG. 1, electrical terminal 18 will contact a biased 
electrical terminal 25 extending from the isolated portion 21 of the lock 
20. The electrical terminal 25 is biased through a conducting spring 26 
and is in electrical connection with a fixed terminal end 27 and a 
conductor 28. The end of the conductor 28 is shown terminated into a 
conventional electrical connector 200. The body 22 of the lock mechanism 
20 is preferably formed of a conducting metal and provides intimate 
electrical contact with the shank 14 of the key 10 when it is properly 
inserted. The lead wire 30 provides a ground connection between the body 
22 and the connector 200. 
A mechanical actuator 29 is shown extending from the body 22 on a shaft and 
is typical in mechanical locks of this type to provide mechanical 
connection to other mechanical or electrical actuated devices In an 
automotive vehicle, the actuator 29 is typically connected to an ignition 
switch and a mechanism for freeing the steering column prior to start up. 
Although not shown in this application, the purpose of the improved key 
assembly shown in FIG. 1 is to provide additional security so that an 
associated anti-theft control system within the vehicle will interrogate 
the electronics of the key to verify that the key is actually the one 
intended for the same vehicle prior to enabling the start circuit for 
vehicle operation. 
FIG. 2 is an embodiment of the circuit 100 embedded within the handle 12 of 
the key 10. The circuit comprises a 10 KHz clock circuit 120, and 8-bit 
shift register 110, an 8-bit counter 130 and a permanently coded element 
formed by conductors 111-118. 
The 50 KHz clock 120 responds to a regulated DC input (5-10 volts) at 
either terminal 16 or 18 via the spring biased terminal 25 on the lock 20 
when fully inserted therein. The DC input is also regulated by the 
resistor 101 and capacitor 102 which serve to isolate the clock circuit 
120 from data modulations that are placed on the DC power line. The clock 
circuit 120 is also connected to ground through the key shank 14 when the 
key is inserted into the grounded lock assembly 20. Two multivibrator 
circuits 125 and 126 are interconnected to provide oscillation in response 
to the application of the DC input signal. Capacitors 123 and 124 are 
selected along with resistors 121 and 122 to provide appropriate RC time 
constants that determine the frequency and duty cycle of the clock signal. 
While Applicants have selected 10 KHz as the output frequency, it should 
be noted that the frequency is not critical to operation of the invention 
but is selected to synchronize with the security system module for reading 
the output signal from the key. 
The permanently coded portion of the circuit is shown as made up of printed 
circuit conductors 111-118 initially interconnected between the 5 volt 
power bus and ground. Subsequently, but prior to permanent encapsulation 
within the handle of the key, the conductors are randomly cut so that the 
potential present on the conductors is either 5 volts or ground. In the 
example shown in FIG. 2, the cuts in the conductors result in the code 
00101111 present at the I/O ports 0-7 of the 8-bit shift register 110. If 
the least significant bit of the code is always "1", 2.sup.7 code 
possibilities are available for selection. 
In operation, when the key is inserted into the lock 20 the shank is held 
to ground potential and 5 volts DC is supplied to either electrical 
terminal 16 or 18, depending upon orientation of the key. The 10 KHz clock 
120 responds to the applied potential to produce pulses which are input to 
both the "Clk" terminals of the 8-bit shift register 110 and the 8-bit 
counter 130. After each eight clock pulses, the counter 130 outputs a 
signal to the "p/s" terminal of the 8-bit shift register 110 which causes 
the shift register to read the input voltages available at the coded 
conductors connected to the I/O ports 0-7. Subsequent clock signals on the 
Clk terminal of the register 110 cause the eight voltage levels read at 
I/O ports 0-7 to be sequentially output as a binary bit stream. The output 
from the 8-bit shift register is provided to resistor 104 and through 
coupling capacitor 103 to modulate the 5 volt signal on the electrical 
terminal 16 and 18. In this manner, the 8 bit code is sequentially clocked 
back through the conductor 25 of the lock assembly 20 and conveyed through 
the electrical connector 200 to the associated security system control 
module. 
While the aforementioned circuit includes a coded device in the form of cut 
conductors on a printed circuit board, it is invisioned that electrically 
programmable or other nonvolatile memory devices may be employed where 
economy or performance requirements dictate. 
It will be apparent that many modifications and variations may be 
implemented without departing from the scope of the novel concept of this 
invention. Therefore, it is intended by the appended claims to cover all 
such modifications and variations which fall within the true spirit and 
scope of the invention.