Cylinder lock

A cylinder lock has a housing with a rotatably insertable cylinder having a key passage for an insertable flat key whose front part has locking notches associated with cylinder pins arranged in openings of the cylinder for retaining the cylinder pins. The flat key is provided at both its lateral sides with longitudinal grooves for receiving longitudinal ribs provided on the lateral sides of the key passage for the lateral profile variation. The longitudinal grooves on both lateral faces of the flat key lie with their bottom faces on lines which extend parallel to and at a distance from one another. The parallel lines extending at a distance from one another are arcuate at least in one partial region, and the convexly protruding central part of one arcuate line extend at least close to a straight line connecting the end points of the second arcuate line.

BACKGROUND OF THE INVENTION 
The invention relates to a cylinder lock composed of a housing and a 
cylinder rotatably supported therein and having a key passage for the 
insertable flat key which has a front part with locking notches associated 
with cylindrical pins arranged in openings of the cylinder for retaining 
the pins, and the flat key has at its both lateral faces longitudinal 
grooves for receiving longitudinal ribs provided on the lateral faces of 
the key passage for lateral profile variation, wherein the longitudinal 
grooves at both lateral faces of the flat key lie in parallel lines 
extending at a distance from one another. In such a construction of the 
flat key the corresponding longitudinal ribs on both lateral faces of the 
above mentioned key passage also lie with their free ends on parallel 
lines extending at a distance from one another and formed by straight 
lines. A free space is thereby formed in the key passage between the 
longitudinal ribs, in which a picking pistol can be inserted, whereby the 
cylinder lock can be opened without the proper key. 
A cylinder lock was also proposed in which the longitudinal ribs on both 
lateral faces of the key passage protrude so far that they extend close to 
the longitudinal centerline of the key passage or cross the longitudinal 
centerline. Thereby a free space in the key passage is avoided so that a 
picking pistol cannot be inserted. The longitudinal grooves provided in 
the flat key for receiving the longitudinal ribs of the key passage engage 
however so deep into the flat key that its cross section is considerably 
weakened or the variation is limited. 
SUMMARY OF THE INVENTION 
The invention has the object to provide a cylinder lock of the above 
mentioned type, in which these disadvantages are eliminated, wherein the 
flat key has a sufficiently great cross section and thereby a sufficient 
strength and an actuation of the cylinder lock with a picking pistol is 
prevented. 
This object is solved in accordance with the present invention in that the 
both parallel lines extending at a distance from one another, against 
which the longitudinal grooves of the flat key lie with their bottom 
faces, extend at least in a partial region arcuately and the convexly 
protruding central part of one arcuate line extends at least close to a 
straight line which connects the end points of the second arcuate line. 
Thereby it is attained in a simple manner that the longitudinal grooves of 
the flat key do not extend too deep into the key cross section, inasmuch 
as the lines which extend parallel to one another and against which the 
longitudinal grooves of the flat key lie with their bottom faces, are 
arranged at a distance from one another. Thereby the key obtains a 
sufficient strength. The proper key passage has because of this a free 
space which however is curved as a result of the arcuate running of the 
lines, so that the actuation of the cylinder lock with a picking pistol is 
impossible inasmuch as for this actuation a rectilinearly extending free 
space is necessary. 
The lines against which the longitudinal grooves of the flat key lie with 
their bottom faces can at least in a partial region run in circularly 
arcuate manner. Because of this it is attained in a simple manner that the 
longitudinal grooves of the flat key extend with their bottom faces along 
a line having the sharp of a circular arc. 
The partial region in which the lines run in an arcuate manner can embrace 
the variation region of the locking notches of the flat key. Thereby the 
arcuate running of the lines is provided in a simple manner exactly in the 
region which embraces the variation region of the locking notches of the 
flat key, so that directly in this region the picking pistol cannot 
operate to actuate the cylindrical pins. 
The partial region in which the lines run in an arcuate manner can be 
arranged with its arc height substantially symmetrical to the longitudinal 
centerline of the cylinder pins. Because of the arcuate shape of the lines 
against which the longitudinal grooves of the flat key with their bottom 
faces lie, engages the part of the key section the ends of the cylinder 
pins facing towards the front part of the key, substantially in the region 
of their longitudinal centerline, so that the arrangement of the cylinder 
pins are not affected. 
The partial region in which the lines extend in an arcuate manner, can 
extend from the end forming the front part to the part of the key section 
forming the key back with its guide. With the exception of the part 
forming the key back with its guide, the lines against which the 
longitudinal grooves of the flat key lie with their bottom faces are 
thereby formed arcuate. 
The bottom faces of the longitudinal grooves of the flat key which lie 
against the lines can extend in correspondence with the arcuate lines also 
in an arcuate manner. Thereby the bottom faces of the longitudinal grooves 
of the flat key are formed in a simple manner arcuate. 
The lateral faces of the flat key can extend parallel to both lines which 
are spaced from one another and are curved in an arcuate manner. Thereby 
the entire cross section of the flat key can be curved arcuately in a 
simple manner. The longitudinal grooves can in this case be provided in 
the key section with an identical depth. 
The lateral faces of the flat key can also extend rectilinearly. Thereby 
the key is formed flat in a simple manner even though the lines against 
which the longitudinal grooves of the flat key lie with their bottom faces 
extend in an arcuate manner. 
The part of the key section forming the key back with its guide can be bent 
and laterally offset to extend parallel to the longitudinal centerline of 
the cylinder pin. 
Thereby the thickness of the curved flat key is reduced in a simple manner. 
Moreover, the end of the key passage section which opens at the outer 
surface of the cylinder extends substantially perpendicular to the outer 
surface. 
The key passage provided in the cylinder may have a cross section 
corresponding to the cross section of the flat key. Thereby the key 
passage has a cross section which allows the insertion of the flat key. 
The novel features which are considered characteristic for the invention 
are set forth in particular in the appended claims. The invention itself, 
however, both as to its construction and its method of operation, together 
with additional objects and advantages thereof, will be best understood 
from the following description of specific embodiments when read in 
connection with the accompanying drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The cylinder lock shown in the drawing is composed of a housing 10 and a 
cylinder 11 rotatably supported therein and having a key passage 12. The 
cylinder 11 is actuated by a key 13 insertable into the key passage 12, 
inasmuch as the front part 20 is arranged to cooperate with cylinder pins 
15 inserted into openings 14 of the cylinder 11, whereby the cylinder pins 
coincide with the outer face 16 of the cylinder 11. This position is shown 
in FIG. 1. Housing pins 19 inserted into openings 17 of the housing 10 and 
arranged under the action of helical pressure springs 18 extend in the 
event of the removed key 13 with their front ends into the openings 14 of 
the cylinder 11 so that the cylinder 11 is locked against rotation. 
For actuating the cylinder lock, the key 13 must have a shape corresponding 
to the shape of the key passage 12 to allow the insertion of the key 13 
into the key passage 12. Moreover, a front part 20 of the key 13 must have 
locking notches 21 corresponding to the length of the cylinder pins 15, so 
that the cylinder pins 14 coincide with the outer face 16 of the cylinder 
11 and thereby a rotation of the cylinder 11 is possible. 
FIG. 3 shows a cross section of a part of the key 13, insertable into the 
key passage 12 of the cylinder 11. The key cross section is so cut through 
that it has a lateral profile variation formed by longitudinal ribs 22-27. 
Thereby, a simultaneous lateral profile variation because of longitudinal 
grooves 28-34 forming gaps between the ribs is provided. The general main 
key has all longitudinal grooves 28-34, but does not have longitudinal 
ribs 22-27. 
As can be seen from FIG. 2, the key passage 12 in the cylinder 11 is 
designed correspondingly. The key passage 12 of the cylinder 11 has 
longitudinal grooves 35-40 corresponding to the longitudinal ribs 22-27 
which serve for the lateral profile variation. The key passage 12 also has 
longitudinal ribs 41-47 which correspond to the longitudinal grooves 28-34 
of the key 13 also serving for the lateral profile variation. 
As can be seen from FIG. 3, the longitudinal ribs 22-27 and the 
longitudinal grooves 28-34 extend approximately over the entire 
longitudinal faces of the key 13 and up to the back 48 which with its 
guide groove 49 does not serve for the longitudinal profile variation. The 
key passage 12 is provided with a corresponding guide rib 50. The key back 
48 extends to the outer face 16 of the cylinder 11 and coincides with the 
latter. This means that the key passage 12 of the cylinder 11 also extends 
to the outer face 16 of the cylinder 11. 
The longitudinal grooves 28-34 on both lateral faces of the flat key lie 
with their bottom faces 51-57 on parallel lines 58 and 59 extending at a 
distance from one another. These lines 58 and 59 are shown in FIG. 3 in 
dash dot lines. Both parallel lines 58, 59 extending at a distance from 
one another, against which the longitudinal grooves 28-34 of the flat key 
13 lie with their bottom faces 51-57, extend in an arcuate manner, and 
particularly as circular arcs. The convexly protruding central part of one 
arcuate line 58 extends at least close to a not shown straight line which 
connects the end points of the second arcuate line 59. In the shown 
embodiment the convexly protruding central part of the arcuate line 58 
crosses the not shown straight line by a considerable piece. The key 
passage 12 in the cylinder 11 is formed correspondingly. The longitudinal 
ribs 41-47 engaging into the longitudinal grooves 28-34 of the key 13 lie 
with their free end faces 60-66 on two lines 67, 68 which extend parallel 
to one another in an arcuate manner, as shown in dash dot lines in FIG. 2. 
Both lines 67, 68 are arranged at a distance from one another so that the 
key passage 12 between the longitudinal ribs 41-47 has a free space 69 
which however extends in an arcuate manner so that an actuation of the 
cylinder pin 15 with a picking pistol is not possible. On the other hand, 
the key 13 obtains a relatively great cross section face because the 
distance between the lines 58, 59 so that the key can withstand all loads. 
A strip 70 of the key 13 extending between both arcuate lines 58, 59 is 
with its arc height in the variation region of the locking notches 21 
arranged substantially symmetrical to the longitudinal centerline 71 of 
the cylinder pin 15. Thereby the strip 70 is always in operative 
connection with the flattened tips of the cylinder pins 15, regardless of 
the variation region of the locking notches 21, so that despite the 
arcuate construction of the strip 70 the actuation of the cylinder pins 15 
is not affected. The variation region of the locking notches 21 is shown 
in FIG. 2 in dotted lines. 
The bottom faces 51-57 of the longitudinal grooves 28-34 of the flat key 
13, which lie against the lines 58, 59, extend in correspondence with the 
arcuate lines 58, 59 also in an arcuate manner. The end faces 60-66 of the 
longitudinal ribs 41-47 of the key passage 12 also extend correspondingly 
in an arcuate manner. 
The lateral faces 72 of the flat key 13 formed by the longitudinal ribs 
22-27 also extend parallel to the lines 58, 59 which are spaced from one 
another and curved in an arcuate manner. Correspondingly, the lateral 
faces 73 of the key passage 12 formed by the longitudinal grooves 35-40 
are also curved in an arcuate manner and extend parallel to the arcuate 
lines 67, 68. 
The part of the key section forming the key back 48 with its guides 49, 50 
is bent and extends in a laterally offset manner parallel to the 
longitudinal centerline 71 of the cylinder pins 51. Thereby the thickness 
of the key 13, despite the arcuate construction, is held as small as 
possible. 
In the second embodiment shown in FIGS. 4 and 5, the section of the part of 
the key 13 which is insertable into the key passage 12 of the cylinder 11 
is shown in FIG. 5. The key cross section is cut through so that it has a 
lateral profile variation by the longitudinal ribs 22-27. A simultaneous 
lateral profile variation is provided by the longitudinal grooves 28-34 
forming the gaps between the ribs. The general main key has all 
longitudinal grooves 28-34, but does not have the longitudinal ribs 22-27. 
As can be seen from FIG. 4, the key passage 12 in the cylinder 11 is 
designed correspondingly. The key passage 12 of the cylinder 11 has the 
longitudinal grooves 35-40 corresponding to the longitudinal ribs 22-27 
which serve for lateral profile variation. The key passage 12 also has the 
longitudinal ribs 41-47 which correspond to the longitudinal grooves 28-34 
of the key 13, also serving for the lateral profile variation. 
As can be seen from FIG. 5, the longitudinal ribs 22-27 and the 
longitudinal grooves 28-34 extend approximately over the entire lateral 
faces of the key 13 and to the back 48 with its guiding groove 49 which 
does not serve for the lateral profile variation. The key passage 12 is 
provided with a corresponding guide rib 50. The key back 48 extends to the 
outer surface 16 of the cylinder 11 and coincides with the same. This 
means that the key passage 12 of the cylinder 11 also extends to the outer 
surface 16 of the cylinder 11. 
The longitudinal grooves 28-34 on both lateral faces of the flat key lie 
with their bottom faces 51-57 on parallel lines 58, 59 arranged at a 
distance from one another. These lines 58 and 59 are shown in FIG. 5 in 
dash dot lines. The parallel lines 58, 59 extending at a distance from one 
another, against which the longitudinal grooves 28-34 of the flat key 13 
lie with their bottom faces 51-57, extend in an arcuate manner, and 
particularly as circular arcs. The convexly protruding central part of one 
arcuate line 58 extends at least close to a not shown straight line which 
connects the end points of the second arcuate line 59. 
In the shown embodiment, the convexly protruding central part of the 
arcuate line 58 crosses the not shown straight line by a considerable 
piece. 
The key passage 12 in the cylinder 11 is formed correspondingly. The 
longitudinal ribs 41-47 engaging in the longitudinal grooves 28-34 of the 
key 13 lie with their free end faces 66-66 on lines 67, 68 which are 
parallel to one another and arcuate, as shown in FIG. 4 in dash dot lines. 
Both lines 67, 68 are arranged at a distance from one another, so that a 
free space 69 is produced in the key passage 12 between the longitudinal 
ribs 41-47, the free space 60 also extending in an arcuate manner so that 
the cylinder pins 15 cannot be acutated by a picking pistol. On the other 
hand, the key 13 has a great cross section face because of the distance 
the lines 58, 59, so that the key can withstand all loads. 
The strip 70 of the key 13 produced between both arcuately extending lines 
58, 59 is with its arc height in the variation region of the locking 
notches 21 arranged substantially symmetrical to the longitudinal 
centerline 71 of the cylinder pins 15. Thereby the strip 70 is always in 
operative connection with the flattened tips of the cylinder pins 15, 
regardless of the variation region of the locking notches 21, so that 
despite the arcuate construction of the strip 70 the actuation of the 
cylinder pin 15 is not affected. The variation region of the locking 
notches is shown in FIG. 4 in dotted lines. 
The bottom faces 51-57 of the longitudinal grooves 28-34 of the flat key 13 
which lie against the lines 58, 59, extend also arcuately in 
correspondence with the arcuate lines 58, 59. Correspondingly, the end 
faces 60-66 of the longitudinal ribs 41-47 of the key passage 12 also 
extend arcuately in a similar manner. 
The lateral faces 72 of the key 13, formed by the longitudinal ribs 22-27, 
extend in this embodiment rectilinearly and parallel to the movement path 
of the cylinder pins 15. The lateral faces 73 of the locking passage 12 
formed by the longitudinal grooves 35-40 also extend rectilinearly. 
Thereby the thickness of the flat key 13 is reduced in a simple manner. 
As mentioned above, only exemplary implementations of the invention are 
illustrated by the above presented embodiments, and the invention is not 
limited thereby. Moreover, other embodiments and variations are possible. 
Thus, it is possible to curve the lateral faces 72 of the flat key 13 also 
in an arcuate manner, whereas the radius thereof deviates from the radius 
of the arcuate lines 58, 59. The lateral profile variation of the flat key 
13 can, instead of the longitudinal ribs 22-27 and longitudinal grooves 
28-34, also have only longitudinal ribs or only longitudinal grooves. 
It will be understood that each of the elements described above, or two or 
more together, may also find a useful application in other types of 
constructions differing from the types described above. 
While the invention has been illustrated and described as embodied in a 
cylinder lock, it is not intended to be limited to the details shown, 
since various modifications and structural changes may be made without 
departing in any way from the spirit of the present invention. 
Without further analysis, the foregoing will so fully reveal the gist of 
the present invention that others can, by applying current knowledge, 
readily adapt it for various applications without omitting features that, 
from the standpoint of prior art, fairly constitute essential 
characteristics of the generic or specific aspects of this invention.