Figures or can be arranged in a circular pattern for use meric conductors 111, 112 or 115 is engaged by teeth 14
in a cylindrical locking device such as an "Ace" lock; of key 12.
that is engaged by a cylindrical key having teeth at a FIG. 9 is an electrical schematic diagram illustrating
distal end. a circuit utilizing the switching device illustrated in
Since conductive elastomeric conductors are elasto- 5 FIG. 8. In the circuit of FIG. 9, power is supplied at
meric and are compressible, the conductors provide a positive and negative supply terminals 139 and 140.
locking device with tolerances as large as plus or minus Resistor 141 is connected between positive supply ter
0.010 inch. This is extremely advantageous since the minal 139 and terminal 134. Coil 142 of relay 143 is
compressibility of the conductors permits wear and connected between terminals 134 and 136. Terminal 138
manufacturing tolerances to be accommodated to much 10 is connected to negative supply terminal 140. Relay
greater extent than has been possible with prior art contacts 144 of relay 143 are connected to output termi
locking devices. nals 145 and 146.
The elastomeric conductors can be made presently at As shown in FIG. 9, switches 113', 114' and 116'
a cost of approximately $0,003 each, which is compata- (formed by elastomeric conductors 113, 114 and 116
ble with the production of a relatively inexpensive lock. 15 and their associated conductive runs 107,108 and 110)
In combination with a printed circuit board, spacing can are connected in series with coil 142 between terminals
be achieved between conductive elastomeric conduc- 134 and 138. For coil 142 to be energized, therefore, all
tors as close as 0.025 inches, which is much closer than three switches 113', 114' and 116' must be closed,
any existing conventional lock having a tumbler mecha- Switches 111', 112' and 115' (formed by elastomeric
nism. 20 conductors 111, 112 and 115 and corresponding con
FIG. 8 illustrates a plan view of circuit board 28 used ductive runs 105,106 and 109) are connected in parallel
in one preferred embodiment of the locking device of between terminals 134 and 138. If any one of these three
the present invention. On its front surface, circuit board switches is closed, it will shunt current flow between
28 has separated pairs of conductive runs 105a and 1056, terminals 134 and 138, and will prevent coil 142 from
106a and 1066, 107c and 1076, 108a and 1086, 109a and 25 being energized, regardless of the state of switches 113',
1096, and 110a and 1106. Positioned over and normally 114' and 116'.
spaced from the gaps between the separated pairs of The circuit of FIG. 9, therefore, permits coil 142 to
conductive runs are elastomeric conductors 111-116. be energized only when the proper combination of teeth
Elastomeric conductor 111 is positioned over the gap 14 are present on key 12. If any one of the switches
between conductive runs 105a and 1056; elastomeric 30 which must be closed (i.e. switches 113', 114' and 116')
conductor 112 is positioned over the gap between con- is not closed, or if any of the three switches which must
ductive runs 106a and 1066; and so on. Elastomeric be open (i.e. switches 111', 112' and 115') is closed, this
conductors 111-116 are normally spaced from the front indicates an improper key, and prevents coil 142 from
surface of circuit board 28, as previously illustrated in being actuated.
the embodiments shown in FIGS. 2 through 7, and are 35 The circuit of FIG. 9 is particularly advantageous
selectively brought into contact with the conductive when the contact resistance of switches 111-116 is low
runs upon pressure from teeth 14 of key 12. (preferably on the order of a few ohms when in the
Located on the back surface of printed circuit board "closed" state). FIG. 10 shows an electrical schematic
28 (and shown in broken lines) are conductive runs 117a diagram of another circuit which is usable when
and 1176. Connections are made between conductive 40 switches lll'-116' have higher closed contact resis
runs on the front and back surface by plated-through tance (for example on the order of 100 ohms). The
holes 118, 120, 122, 124, 126, 128 and 130. Plated- circuit of FIG. 10 is usable with the embodiment of
through holes 118,120 and 122 connect conductive runs circuit board 28 shown in FIG. 8, except that plated
105a, 106a and 109a, respectively, with conductive run through connector 128 is not provided, and a separate
117a. Similarly, plated-through holes 124, 126, 128 and 45 terminal 147 is connected to conductive run 1076.
130 connect conductive runs 1056, 1066, 1076 and 1096 In the circuit of FIG. 10, power is again supplied
to conductive run 1176. between power supply terminals 139 and 140. Resistors
In the embodiment of circuit board 28 shown in FIG. 148 and 149 and switches 113', 114' and 116' form a 8, conductive terminal pins 134, 136 and 138 provide series current path between terminals 139 and 140. Reconnection between the conductive runs of printed 50 sistor 148 is connected between terminal 139 and termicircuit board 28 and external circuitry of the locking nal 136. Resistor 149 is connected between terminal 147 device. Terminal 134 is connected to conductive run and terminal 140.
117a; terminal 136 is connected to conductive run 110a; Coil 142 of relay 143 is connected in a series current
and terminal 138 is connected to conductive run 1176. path between terminals 139 and 140 which includes
In the embodiment shown in FIG. 8, conductive runs 55 resistor 150 and NPN transistor 151. Resistor 150 is
107a and 108a are connected together, and conductive connected between terminal 139 arid terminal 142a of
run 1086 is connected to conductive run 1106. As a coil 142. The collector-emitter current path of transistor
result, the switches formed by elastomeric conductors 151 is connected between terminal 1426 and terminal
113,114 and 116 (and their associated conductive runs) 140. The base of transistor 151 is connected to terminal
are connected in series between terminals 136 and 138. 60 147. Diode 152 is connected in parallel with coil 142 to
The switches formed by elastomeric conductors 111, provide flyback protection.
112 and 115 (and their associated conductive runs) are Switches 111', 112' and 115' are connected with resis
connected in parallel between terminals 134 and 138. As tors 153 and 154 in a current path between terminals 139
a result, elastomeric conductors 113, 114 and 116 must and 140. Resistor 153 is connected between terminal 139
all be engaged by teeth 14 of key 12 in order to provide 65 and terminal 134, and resistor 154 is connected between
a conductive connection between terminals 136 and terminal 138 and terminal 140. Switches 111', 112' and
138. On the other hand, conductive connection between 115' control the conductive state of NPN transistor 155,
terminals 134 and 138 is achieved if any one of elasto- which has its base connected to terminal 138 and its