|Title of Invention||
"STRUCTURE OF KEYHOLE OF CYLINDER LOCK"
|Abstract||[Object] An object of the present invention is to provide a structure of a keyhole of a cylinder lock. [Constitution] A protector 17 is provided at the inlet of the keyhole of the cylinder lock for preventing entry of foreign matters; and a through hole 24 is made in the protector 17 for insertion of the key. The through hole 24 is comprised of a long side 27, a short side 28 formed at right angles with the long side 27, rounded portion 29 formed at four corners, projecting portions 31 and 32 formed on the long side 27, and a projection 33 formed at the center of the short side 28.|
|Full Text||[DETAILED DESCRIPTION OF THE INVENTION]
 [Industrial Field of Utilization]
The present invention relates to a technology for improving the structure of a keyhole of a cylinder lock..
 [Prior Art]
The cylinder lock keyhole has been proposed by for instance © Japanese Patent Publication No. Sho 59-11029 entitled "Key Cylinder" and (2) Japanese Utility Model Laid-Open No. Sho 51-27694 entitled "Cylinder Lock".
That is, a metal portion 39 of a key insertion opening
shown in Fig. 5 of the official patent gazette CD is produced of a high-hardness material, which, used at the insertion opening of the cylinder lock, will not interfere with ordinary key operation but will serve to prevent an inner tube 32 from being pulled out with such a foreign substance as a tap inserted, to thereby improve a theft-prevention performance (Refer to the left column of the official patent gazette ©, pp. 2, lines 11 to 14 . ) . The metal portion 39 at the key insertion opening is generally called a protector.
The metal portion 39 at the key insertion opening, or the protector, is provided with a rectangular, narrow through hole as shown for instance in Fig. 2 of the official patent
Fig. 6 is a plan view of a prior art cylinder lock keyhole.
A protector 100 is required to have high hardness. However, the high-hardness member is hard to cut, resulting in an increased cost of machining. In recent years there has been adopted a sintered part which satisfies both high hardness and low cost. The sintered part is produced by molding in a powdered
form and bonding by sintering. Molding a through hole 101 in the molding stage can dispense with the cutting process.
Numeral 102 ... ("..." means plurality) denotes the radius of rounding of. corners, that is, the minimum radius to be inevitably provided at the time of molding.
In the meantime, a key 105 is of a common steel and has guide grooves 106... formed by cutting after pressing. Since the key 105 is made of the common steel, its end faces 107, 107 can easily be processed by cutting.
 [Problem to Be Solved by the Invention]
The protector 100, when produced of a sintered part as stated above, must be provided with the radiuses 102. . . at the four corners of the through hole 101. According to the design of the cylinder lock, it is impossible to insert a key 105 over the radiuses 102. . . . The key 105, if inserted, will ride on the radius 102, defying further insertion and removal.
Then, there will occur a clearance SI between the end face 107 of the key 105 and a short side 103 of the through hole 101.
The key 105, when inserted from the surface side in the drawing, will possibly deviate to the left or to the right by the amount of SI. If the key 105 deviates by the amount of Si, • the projecting portion 109 of the key 105 will interfere with the projecting portion 108 of the through hole 101, checking further insertion of the key 105. In this case, it becomes necessary to move (correct) the key 105 to the right or to the
left by SI. This operation is troublesome and is not easy to perform.
 [Object of the Invention]
It is therefore an object of the present invention to present the structure of a keyhole which ensures easy key insertion and operation.
 [Means for Solving the Problem]
To accomplish the above-described object, the cylinder lock of claim 1 is provided with a protector at the keyhole opening of the cylinder lock to prevent entry of foreign substances, and is of such a structure that the key is inserted into a keyhole of the cylinder lock through an approximately rectangular, narrow through hole made in the projection. In this cylinder lock, there are provided key positioning projections at least in the vicinity of the edge of the opening of the through hole, on opposite sides of the through hole.
Thus the key can be inserted while being positioned by the opposite projections, which enables easy key insertion.
The structure of the keyhole of the cylinder lock of claim 2 is characterized in that the height of the projections agrees approximately with the radius of rounding at four corners of the through hole.
Adjusting the projection height to the radius of rounding can reduce a clearance between the through hole and the key to a minimum, thereby enabling smooth key insertion.
The structure of the keyhole of the cylinder lock of claim 3 is characterized in that the projections are provided on the opposite short sides of the through hole.
A clearance between the key and the through hole is reduced to a minimum by forming the projections on the short sides, and by bringing the long side as close to the key as possible. Also, a surface area of a large clearance between; the through hole and the key can be decreased by forming, on the short side, the large clearance produced by the radius of rounding and by forming the projections on the short side.
[BRIEF DESCRIPTION OF THE DRAWINGS]
Fig. 1 is a perspective view of a front section of a motorcycle concerning the present invention;
Fig. 2 is an exploded perspective view of the structure of a keyhole of a cylinder lock concerning the present invention;
Fig. 3 is a plan view of a protector concerning the present invention;
Fig. 4 is a sectional view taken along line 4-4 of Fig. 3;
Fig. 5 is an explanatory view of the function of the structure of the keyhole of the cylinder lock concerning the present invention; and
Fig. 6 is a plan view of a keyhole of a prior art cylinder lock.
 [Preferred Embodiments]
The embodiment of the structure of the keyhole according to the present invention will hereinafter be described with reference to the accompanying drawings. The drawings are to be viewed in the direction of numerals.
Fig. 1 is a perspective view showing the front section of a motorcycle according to the present invention. The front section of the motorcycle 1 is comprised of a fuel tank 2 and an engine 3 mounted at the central part of a vehicle frame not depicted, a front fork 5 mounted in a steerable state on a front steering head 4, a front wheel 6 mounted on the lower end of the front fork 5, a handlebar 7 mounted on the upper end of the front fork 5, grips 8, 8 fitted on both ends of the handlebar 7, and meters 9 and a main switch 10 arranged at the central part. Numeral 11 denotes a clutch lever, and numeral 12 denotes an exhaust pipe.
Fig. 2 is an exploded perspective view of the structure of the keyhole of the cylinder lock according to the present invention.
A protective body 15 provided at the inlet of the main switch 10 (Fig. 1) comprises a cylindrical protector 17, a shutter plate 19 slidably fitted in a recess 18 of the protector 17, and a cap 21 covering these parts. Numeral 23 refers to a compression spring, which is a member for pressing the shutter plate 19 towards closing. Numeral 24 denotes a through hole, through which the key is inserted into the keyhole of the cylinder lock.
Fig. 3 is a plan view of the protector according to the present invention. The through hole 24 includes long sides 27, 27, short sides 28, 28 formed at right angles with the long side 27, rounded portions 29 formed at the four corners where the long side 27 and the short side 28 meet, a projecting portion
31 formed at the center of the long side 27, a projecting portion
32 formed in parallel with the projecting portion 31, and a
projection 33 formed at the center of the short side 28.
Configuration of the projection 33 will be described later.
The protector 17 is a sintered part produced by molding in a powdered form and by bonding by sintering. The through hole 24 is formed in the stage of molding to thereby dispense with the cutting process.
The short side 28 is long enough to determine the key
position (in a vertical direction in the drawing) and to prevent entrance of foreign substances.
The rounded portion 29 has the minimum radius that enables die molding. It is necessary to round the four corners to allow die molding the protector 17. 
Fig. 4 is a sectional view taken along line 4-4 of Fig. 3, in which the projecting portion 31 and the projecting portion 32 are formed from the midpoint to the lower end of the through hole 24, and the projection 33 is formed from the upper end to the lower end.
The projecting portion 31 contacts the middle groove of the key, thereby guiding the key.
The projecting portion 32 contacts the serrations formed on the edge of the key to thereby .guide the key.
The projection 33 is for positioning the key (in the horizontal direction in the drawing) . The key is positioned at the stage before reaching the projecting portions 31 and 32 when the key is inserted from above (in the drawing).
Next, the function of the structure of the cylinder lock keyhole described above will be explained.
Fig. 5 is a drawing explaining the function of the structure of the cylinder lock keyhole according to the present invention, with a key 40 (a section) inserted in the through hole 24.
Since the clearance between the key 40 and the keyhole has been decreased by the projection 33, the key 40, if deviated
to the right or to the left when inserted, will contact the projection 33. The key 40 stops at a predetermined position, allowing the positioning of the key 40. When the key 40 is inserted while being positioned by the projection 33 , the middle groove 41 of the key 40 slides in contact with the projection portion 31, and at the same time the projecting portion 32 slides along the groove 42 to thereby guide the key 40.
Hereinafter the projection 33 will be explained in detail.
The projection 33 contacts a straight line AA between the point Al where the long side 27 and the rounded portion 29 meet and the point A2, and is formed by the radius of curvature B smoothly connecting the rounded portions 29. "R" is the minimum radius of rounding enabling die molding, indicating inscription of a size of the rounded portion 29. "D" is the height of projection, which nearly corresponds the radius of rounding R. The radius of curvature B is also nearly equal to the radius of rounding R. As a result, it is possible to reduce the clearance SI (Fig. 6) to the clearance S2 by the height of projection D to thereby prevent key deviation if the radius of rounding R is provided.
 [Effect of the Invention]
The present invention can display the following effect by the adoption of the above-described constitution.
In claim 1, the projections are provided on the opposite short sides, therefore the key can be inserted while being
positioned by the projections. It is, therefore, unnecessary to give special consideration to positioning, and can improve easiness of key handling at the time of key insertion.
According to claim 2, since the height of the projections nearly corresponds to the radius of rounding, a clearance widened by the radius of rounding can be made up for by the projection, thereby diminishing the clearance.
Furthermore, since the radius of the projection is the minimum radius which allows die molding, it is possible to produce the protector from a sintering material efficiently.
It is, therefore, possible to put an easy-to-insert, low-cost cylinder lock into commercial production.
Furthermore, according to claim 3, a projection is formed on the short side to form the long side as close to the key side as possible to thereby minimize a clearance between the key and the through hole. Also since a large clearance produced by the provision of the radius of rounding is formed on the short side, the surface area of the large clearance between the through hole and the key can be decreased in order to prevent entry of foreign substances through the clearance.
[Explanation of Reference Numerals]
10 ... cylinder lock (main switch) ; 15 ... protective body; 17 ... protector; 24 ... through hole; 27 ... long side; 28 .. short side; 29 ... rounded portion; 31, 32 ... projecting portions; 33 ... projection; 40 ... key,- B . . . radius of curvature; R . . . radius of rounding; D ... height of projection
[Claim 1] In a cylinder lock which has, at the opening of a keyhole of said cylinder lock, a protector for preventing entrance of foreign substances, and is of the structure that a key is inserted into said keyhole of said cylinder lock through an approximately rectangular narrow through hole made in said protector;
said structure of said keyhole of said cylinder lock characterized in that there is provided a projection for positioning said key on opposite sides of said through hole, in the vicinity of at least the edge of said opening of said through hole.
[Claim 2] Structure of a keyhole of a cylinder lock as claimed in claim 1, characterized in that the height of said projection nearly agrees with the radius of four rounded portions of said through hole.
[Claim 3] Structure of a keyhole of a cylinder lock as claimed -•• in claim lor 2, characterized in that said projection is provided on opposite short sides of said through hole.
4. A cylinder lock substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.
|Indian Patent Application Number||3774/DEL/1998|
|PG Journal Number||11/2008|
|Date of Filing||16-Dec-1998|
|Name of Patentee||HONDA GIKEN KOGYO KABUSHIKI KAISHA|
|Applicant Address||1-1, MINAMIAOYAMA 2-CHOME, MINATO-KU,TOKYO, JAPAN|
|PCT International Classification Number||E05B 17/14|
|PCT International Application Number||N/A|
|PCT International Filing date|