Electric contact structure for a locking cylinder

A contact structure of a locking cylinder comprising a pair of contact pieces each extending laterally and pivoted at its one end about a pivot axis parallel to the axial line of the locking cylinder, a pair of springs, each urging the corresponding contact piece inwardly toward the center of the locking cylinder, a pair of stoppers which limit the inward motion of the contact pieces to the positions where they protrude slightly into a bore defined at the entrance to the key hole of the locking cylinder. The radially inner surfaces of the contact pieces of the locking cylinder define contact surface which electrically contact the corresponding contact pieces provided in the side edges of the base end of the shank of the key. This contact structure provides uninterrupted electric conductance between the key and the locking cylinder. To facilitate the insertion of the key into the key hole of the locking cylinder, a guide member may be fitted into the cavity defined between the contact pieces in front of the key hole so as not to interfere with the motion of the contact pieces.

TECHNICAL FIELD 
The present invention relates to an electric contact structure for a key 
cylinder and in particular to such a contact structure in which an 
electric contact can be established between a locking cylinder and a key 
inserted therein. 
BACKGROUND OF THE INVENTION 
Copending U.S. patent application No. 121,321 discloses a key device 
combining a common mechanical key and an infrared transmitter incorporated 
in the handle of the key device. The key device may be used as a remote 
controller for opening the door of the vehicle and, also, as an electronic 
code transmitter which is used in combination with the mechanical key as 
an ignition key of improved security. In such a case, it is advantageous 
to establish an electric contact between the key device and the 
corresponding locking cylinder for transmitting electric power from the 
vehicle to the handle of the key or for exchange of signals between the 
key device and the locking cylinder. Particularly when the handle of the 
key device incorporates a transmitter for locking/unlocking the door of 
the vehicle, the key device must be incorporated with a battery and 
keeping this battery electrically charged is an important requirement for 
satisfactory performance thereof. 
Japanese Patent Laid Open Publication No. 62-1659 discloses electronic keys 
which are provided with connectors 18, 20, 40, 42, 52 and 54 which are 
electrically connected to the corresponding connectors 30, 32, 48, 50, 56 
and 58 on the vehicle when the keys are inserted into the corresponding 
locking cylinders for the purpose of electrically charging the 
rechargeable batteries for these electronic keys. 
However, according to this proposal, the mechanical key is ether unusual in 
shape or required to be made of electrically insulating material, the user 
must overcome a very unfamiliar feel, and, therefore, the commercial 
acceptability of this key structure based on this proposal may not be 
satisfactory. Further, the disclosure of this Japanese patent publication 
is limited to a conceptual structure and does not teach anything which 
assures the reliability of the electric contact between the key and the 
locking cylinder. 
U.S. Pat. No. 4,148,372 discloses a contact structure in its FIGS. 2 and 3 
for establishing an electric contact between the key and the locking 
cylinder. The key is provided with a resistor pellet 16 which serves as an 
electronic code. The electric contact is required here in order to obtain 
an electric access to the resistor pellet. According to this proposal, 
spring loaded contacts 18, 20, 22 and 24 are provided in the rotor for 
receiving the key, and are used to electrically contact not only the 
resistor pellet but also a pair of slip rings 26 and 28 provided in a 
stationary sleeve which surrounds the rotor. As shown in FIG. 1 of this 
patent, the contact structure is provided at the entrance to the locking 
cylinder. But, this structure is not suitable for applications where the 
short-circuiting of the contacts of the locking cylinder is not permitted 
because, according to the proposed invention, the contacts engage the 
metallic part of the key shank as it is inserted into the key hole and are 
electrically connected to each other. Further, each electric path contains 
two points of sliding contact (between the key shank and the contact 
engaged thereto, and between the slip ring and the contact engaged 
thereto), and the electric continuity may therefore not be kept at all 
time. 
BRIEF SUMMARY OF THE INVENTION 
In view of such problems of the prior art, a primary object of the present 
invention is to provide an electric contact structure for a locking 
cylinder which can be used in conjunction with a conventional mechanical 
key without in any way impairing the simplicity of its handling. 
A second object of the present invention is to provide an electric contact 
structure for a locking cylinder which would not unduly increase the size 
of the locking cylinder. 
A third object of the present invention is to provide an electric contact 
structure for a locking cylinder which provides an uninterrupted electric 
conduction even while the key is being turned. 
A fourth object of the present invention is to provide an electric contact 
structure for a locking cylinder in which the contacts of the locking 
cylinder would not be short-circuited as the key is inserted into the 
locking cylinder. 
A fifth object of the present invention is to provide an electric contact 
structure for a locking cylinder which is reliable and durable. 
These and other objects of the present invention can be accomplished by 
providing an electric contact structure for a locking cylinder which is 
adapted to receive the shank of a key having a contact piece at the base 
end of the shank for establishing a mutual electric contact between 
electric circuits provided in the key and the locking cylinder, 
respectively, comprising: a fixed, hollow cylindrical sleeve defining an 
axial bore therein; a cylindrical rotor which is rotatably received within 
the bore of the hollow sleeve and defines a key hole therein; and another 
contact piece which is provided in the sleeve and is radially inwardly 
urged by spring means so as to come into contact with the contact piece of 
the key shank when the key shank is received in the key hole; the contact 
piece of the locking cylinder extends laterally across a gap defined 
externally of the front end surface of the rotor, and pivotally supported 
at its one end by the fixed sleeve about a pivot axis extending along the 
axial direction of the locking cylinder. 
Thus, the size of the locking cylinder, in particular its outer diameter, 
is not required to be unduly increased for accommodating the contact 
piece, and a reliable conduction of electricity can be assured. 
According to a preferred embodiment of the present invention, the contact 
piece of the locking cylinder is received in a recess provided in an inner 
circumferential surface of the hollow sleeve, and the recess comprises a 
shoulder surface which engages a part of the contact piece of the locking 
cylinder so as to limit an inward rotational motion of the contact piece 
about the pivot axis. Thereby, the contact piece of the locking cylinder 
would not interfere with the insertion of the key into the locking 
cylinder, and the short-circuiting of the contact piece of the locking 
cylinder with a metallic part of the key shank is effectively prevented. 
When the contact piece of the locking cylinder is provided with an arcuate 
contact surface which establishes an electric contact with the contact 
piece of the key over a certain angular range defined by the expanse of 
the arcuate contact surface, the electric conduction accomplished by the 
contact pieces can be conveniently used as a source of a signal for 
indicating the angular position of the locking cylinder. 
According to a preferred embodiment of the present invention, the front end 
surface of the rotor is fitted with a key shank guide member having an 
opening for receiving the key shank and a recess provided at its side 
portion for exposing the contact piece of the key shank to the contact 
piece of the locking cylinder laterally from the recess when the key shank 
is inserted into the key hole through the opening. Thereby, the provision 
of the contact piece of the locking cylinder does not impair the facility 
of inserting the key shank into the key hole of the locking cylinder which 
tends to be located relatively deeper in a socket defined by the outer 
sleeve for accommodating the contact piece.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 generally shows an engine control system to which an embodiment of 
the contact structure according to the present invention is applied. This 
system comprises a key switch unit 2, which combines a steering lock 
cylinder and an ignition key switch, mounted on the steering column of the 
vehicle 1, and a key 3 having a key shank 6 which is adapted to be 
inserted into the key switch unit 2 in the same way as a conventional 
ignition key and a handle 4 which is molded from synthetic resin material 
and provided with a pair of light emitting elements 5 on either side of 
the base end of the key shank 6 with their axial lines directed towards 
the tip of the key shank 6. The handle 4 further incorporates therein a 
control circuit 7 for the light emitting elements 5 and a rechargeable 
battery 8 for supplying electric power to the light emitting elements 5 
and the control circuit 7. The side edges of the base end of the key shank 
6 are provided with a pair of contact pieces 9 which are electrically 
connected to the control circuit 7. 
The key switch unit 2 is provided with a pair of contact pieces 10 which 
can elastically contact the contact pieces 9 of the key 3 when it is 
inserted into the key switch unit 2, and a light receiving element 11, 
consisting, for instance, of a phototransistor. These contact pieces 10 
and the light receiving element 11 are connected to a control unit 12 
provided in the vehicle 1. The control unit 12 is connected to the 
on-board battery 13 of the vehicle 1, and relays 41 and 42 for controlling 
the operation of the engine control circuit 14 and the starter circuit 15, 
respectively, when the key switch unit 2 is turned to the positions of 
"ON" and "ST", respectively. 
FIGS. 2 through 4 show essential parts of the key 3 and the key switch unit 
2 when the key 3 received in the key switch unit 2 has been turned to the 
position "ON". 
As shown in FIG. 3, the key switch unit 2 may be turned to any of a 
plurality of positions, "LOCK", "ACC", "ON" and "ST" for selectively 
permitting the actions of the engine control circuit 14, the starter 
circuit 15 and other on-board equipment according to the selected 
position. The key switch unit 2 is constructed substantially as a 
conventional locking cylinder, and is provided with a cylindrical outer 
sleeve member 16 made of synthetic resin material, and a rotor 17 which is 
likewise made of metallic material and is received in the outer sleeve 
member 16 in a rotatable manner over a certain angular range. The rotor 17 
is provided with a key hole 18 for receiving the key shank 6. 
A tubular inner cap 19 made of synthetic resin material is fitted onto the 
free end of the outer sleeve member 16 in a ooaxial manner, and covers the 
peripheral portion of the axial end surface thereof. A similar auxiliary 
cap 21 is fitted over the inner cap 19. Further, a tubular outer cap 22 
made of stamp formed sheet metal covers the axial end surface of the 
auxiliary cap 21 and surrounds the two caps 19 and 21 and the outer sleeve 
member 16 by being fixed to the outer sleeve member 16 by crimping. 
The inner cap 19 is provided with a coaxial and circular opening 23 whose 
diameter is substantially larger than the dimension of the longer side of 
the key hole 18. The auxiliary cap 21 is likewise provided with a coaxial 
and circular opening 21a whose diameter is substantially greater than that 
of the opening 23 of the inner cap 19. The width of the base end of the 
key shank 6 is slightly smaller than the diameter of the opening 23 of the 
inner cap 19. The opening 21a of the auxiliary cap 21 receives a disk 
member 45 which is described hereinafter. 
FIG. 4 shows the structure of the locking cylinder as related to the disk 
member 45. The disk member 45 comprises a circular end plate 26 which 
substantially closes the opening 21a of the auxiliary cap 21. The end 
plate 26 is provided with a key introduction slot 24 for receiving the 
base end of the key shank 6. The slot 24 terminates at its both ends 
without reaching the extreme periphery of the end plate 26. The inner end 
surface of the end plate 26 is provided with a coaxial boss 27 having a 
diametral slot 28 which is passed completely through a diametral line 
thereof and communicated with the key introduction slot 24. The axial end 
surface of the coaxial boss 27 is provided with a pair of projections 30 
which are adapted to be fitted into the corresponding holes 29 provided in 
the front end surface of the rotor 17, on either side of the key hole 18. 
Thus, the disk member 45 is adapted to rotate integrally with the rotor 
17. Since the slot 24 of the disk member 45 defines the entry hole for the 
key shank 6, the user of the key has very little difficulty in inserting 
the tip of the key shank 6 into the key hole 18 by way of the key 
introduction slot 24 even though the key hole 18 is located deeper than 
usual in a socket defined by the inner cap 19 and the auxiliary cap 21. 
A pair of terminal holders 31, having a semicircular cross section and made 
of electrically insulating material, are fixedly attached to either side 
edge of the base end of the key shank 6 and extend along the axial 
direction of the key shank 6. The terminal holders 31 are each covered, on 
the exterior, by the corresponding contact piece 9 having an arcuate cross 
section and made of electro-conductive material, and these contact pieces 
9 are fixedly attached to the outer surfaces of the corresponding terminal 
holders 31. Thus, the contact pieces 9 are insulate from the key shank 6 
by the terminal holders 31, and when the key shank 3 is inserted all the 
ay into the key hole 18, the contact pieces 9 are exposed and protrude 
radially from the diametral slot 28 of the boss 27 of the disk member 45. 
As best shown in FIGS. 2 and 3, the auxiliary cap 21 is provided with 
cavities 32 which are open to the interface with the inner cap 21 as well 
as to the inner periphery of the opening 23, for receiving the 
corresponding contact pieces 10 therein. The cavities 24 further 
accommodate therein electro-conductive support plates 25 which are partly 
fixedly molded with the auxiliary cap 21. The support plates 25 are 
provided with upright pivot shafts 34 which pivotally support the base 
ends of the corresponding contact pieces 10; the radially inner surface of 
each of the contact pieces 10 adjacent to its free end is provided with an 
arcuate contact portion 35 which extends, in an arcuate manner, along the 
inner circumferential surface of the opening 23, from the position which 
is slightly away from the position "ON" towards the position "ACC", to the 
position corresponding to the position "ST". 
To the edge of each of the corresponding contact pieces lO, opposite to the 
edge provided with the co-axial boss 35, elastically abuts a free end of a 
compression coil spring 36 which urges the corresponding contact piece 10 
away from the outer periphery towards the center of the opening 23. Each 
of these compression coil springs 36 is received in a slot 39 formed in 
the radially outward direction from the corresponding cavity 24, along 
with a terminal piece 38 which forms a part of the corresponding support 
plate 25, and the base end of each of the compression coil springs 36 is 
engaged to the terminal piece 38 which is bent perpendicularly from the 
main part of the support plate 25 towards the axial direction of the key 
switch unit 2. The terminal pieces 38 are electrically connected to the 
control unit 12 which is referred to earlier. The cavities 24 are provided 
with shoulder surfaces (stoppers) 37 (FIG. 3) which limit the extent of 
the protrusion of the contact portions 35 into the opening 23. In this 
embodiment, the contact pieces 10 are electrically connected to the 
support plates 25 by way of the compression coil springs 36, but it is 
also possible to use a pair of lead wires to electrically connect them. 
Thus, when the key shank 6 is inserted into the key hole 18 of the key 
switch unit 2, the contact pieces 9 are electrically connected to the 
control unit 12 by way of the contact pieces 10, the compression coil 
springs 36 and the support plates 25. 
As shown in FIGS. 3 and 4, the key switch unit 2 is provided with the light 
receiving element 11 which faces axially outwardly from a slot 21b 
provided in the auxiliary cap 21 and a conformal opening 22a (FIG. 4) 
provided in the tubular outer cap 22. The light receiving element 11 is so 
arranged that it can receive the light from one of the light emitting 
elements 5 of the key 3 when one of the light emitting elements 5 opposes 
the light receiving element 11 from a region located substantially between 
the positions "ACC" and "ST". The light emitting elements 5 are arranged 
symmetric with respect to the axial line, so as to allow the key 3 to be 
properly inserted into the key hole 18 even when it is inverted. 
In this ignition key system, the engine can be started by inserting the key 
3 into the key switch 2 which is located at the position "LOCK" and 
turning the key all the way to the position "ST". In this embodiment, the 
two sets of contact pieces 9 and 10 come into mutual contact when the key 
switch unit 2 is turned to the position "ON" as mentioned earlier, and the 
electric power from the on-board battery 13 then begins to be supplied to 
the control circuit 7 and the rechargeable battery 8. This triggers the 
action of the control circuit 7, and a coded signal is transmitted from 
the light emitting elements 5 in the form of infrared light to the light 
receiving element 11 of the key switch unit 2. In the control unit 12, the 
received coded signal is compared with an internal code stored therein. If 
the codes match one another, the control unit 12 activates the engine 
control circuit 14 and the starter circuit 15 by way of the relays 41 and 
42. Thus, the engine control circuit 14 and the starter circuit 15 are 
activated according to the position of the key switch unit 2, and the 
engine of the vehicle is accordingly controlled thereafter.