Pneumatically operated disk brake

A pneumatically operated disk brake having a caliper actuated by an application through a traverse member which is displaceably guided with respect to the brake disk, at least one adjusting spindle is adjustably screwed to the traverse member and an adjusting device acts upon the adjusting spindle to maintain a desired ventilating play. A device is provided which prevents any rotating of the threaded spindle up to a specified torque. For a two spindle device the synchronization device can be locked in the released condition of the brake. Another solution is to provide on each adjusting spindle its brake-disk-side end a frontal toothing which engages in a corresponding frontal countertoothing of its pressure piece.

BACKGROUND AND SUMMARY OF THE INVENTION 
The present invention relates to a pneumatically operated disk brake which 
is provided particularly for commercial road vehicles. 
Pneumatically operated disk brakes or pneumatic disk brakes of the 
above-mentioned type are known, for example, from German Patent Document 
DE-OS 37 16 202, from German Patent Document DE-OS 40 32 885 as well as 
from German Patent Document DE-OS 42 12 384 which is no prior publication. 
In the case of these known disk brakes, a caliper which is disposed to be 
slidable in the axial direction reaches around a brake disk. On one side 
of the caliper, a pneumatically operated application device is arranged. 
When this pneumatically operated application device is actuated, a brake 
shoe situated on this side of the brake disk is pressed against the 
corresponding friction surface of the brake disk. As a result of the 
reaction forces, the caliper will be displaced in the opposite direction 
and will therefore press a brake shoe which is situated on the opposite 
side also against the brake disk. 
In the case of these known disk brakes, the application device has a rotary 
lever which operates as an actuating element and which is disposed to be 
swivellable about an axis of rotation which extends in parallel to the 
plane of the brake disk. On its side facing the brake disk, the rotary 
lever rests via an eccentric approximately in the longitudinal center 
against a traverse member which extends in parallel to the axis of 
rotation and which is guided to be slidable with respect to the brake 
disk. Two adjusting spindles with an external thread are screwed in an 
adjustable manner into a respective assigned internal thread of the 
traverse member in a parallel arrangement. Because two adjusting spindles 
are used, an application device of this type is also called a "two-spindle 
application device". 
The two adjusting spindles each act via a pressure piece disposed on their 
brake-disk-side end on the brake shoe disposed in a slidable manner with 
respect to the brake disk on the application side in the caliper. The 
ventilating play, which changes because of the wear of the lining, 
constantly maintains its correct desired value by at least one adjusting 
device. The adjusting device is coupled in an axially displaceable manner 
but rotationally fixed with one of the two adjusting spindles and acts, 
during each actuating of the rotary lever, via a sliding clutch on the 
respective adjusting spindle. The rotation of the adjusting spindle which 
is caused by the adjusting device in the case of a wear of the lining is 
transmitted by a synchronization device to the second adjusting spindle 
such that this adjusting spindle is rotated about the same angle and 
therefore reduces its distance to the brake disk by exactly the same 
amount. 
In the simplest case, only one driving device is arranged in the second 
adjusting spindle, which driving device couples this adjusting spindle in 
a rotationally fixed manner with the synchronization device. The driving 
device may be, for example, a gearwheel which engages in an internal axial 
toothing of the adjusting spindle, which gearwheel is coupled via a shaft 
with the synchronization device. However a separate adjusting device may 
also be provided for the second adjusting spindle. In this case, adjusting 
forces can be achieved that are twice as high which, however, is connected 
with correspondingly higher manufacturing costs. 
When only one adjusting spindle is present ("single-spindle" application 
device) the synchronization device is naturally eliminated. 
As mentioned above, the precise adjustment of a constantly uniform 
ventilating play is very important for the secure and reliable functioning 
of the disk brakes of this type. Although the adjusting devices which were 
developed by the Assignee of the applicant operate in a reliable and 
highly precise manner (reference is made in this respect, for example, to 
German Patent Document DE-OS 40 34 165 corresponding to U.S. Pat. No. 
5,353,896 of the Assignee of the applicant) it has been found difficult in 
practice to maintain the ventilating play in the desired tolerance range. 
In particular, in practice, an undesirable reduction of the ventilating 
play will frequently occur so that the brake may even tend to lock. 
The invention is therefore based on the object of further developing a 
pneumatically operated disk brake such that a constantly large ventilating 
play can always be achieved. 
According to the invention, this object is achieved by providing a device 
which prevents any rotation of the adjusting spindle up to a defined 
torque. 
Detailed tests have shown that the ventilating play changes, despite the 
correct functioning of the adjusting device, since the respective 
adjusting spindle, when subjected to extensive shaking stress, has the 
tendency to automatically or without any corresponding torque admission by 
the adjusting device, to rotate. The rotation is in the adjusting 
direction because the adjusting device, as a rule, has a directional 
clutch which prevents a rotation of the adjusting spindle against the 
adjusting direction. This undesirable rotational movement of the adjusting 
spindle or spindles is therefore the cause of the undesirable change of 
the ventilating play. 
The invention therefore suggests that a device be provided which prevents 
any rotating of the threaded spindle or spindles up to a defined torque. 
As a result, any shaking stress which may occur in practice will 
definitely be unable to cause an undesirable rotation of the adjusting 
spindle or spindles so that the ventilating play will always remain 
constant. At the same time, when the torque is selected in an appropriate 
manner, the adjusting device is capable of rotating the adjusting spindle 
or spindles when there is a wear of the brake lining. In which case, the 
slightly increased torque which is required for this purpose presents no 
problems in the given force relationships and drive performances of the 
adjusting device. 
According to the advantageous further development of the invention, the 
required braking torque for the respective adjusting spindle can be 
achieved, for example, an elastic element which acts upon the threaded 
surface of the concerned threaded spindle. The elastic element may, for 
example, be a friction ring made of rubber or the like which is fastened 
on the end of the corresponding threaded bore of the traverse member which 
faces the brake disk or is on the outside and whose inside diameter is 
smaller than the outside diameter of the threaded spindle. This 
arrangement is particularly simple and cost-effective, and furthermore has 
the advantage that an additional sealing is provided for the rust 
sensitive threaded surfaces of the adjusting spindle and of the traverse 
member. Naturally the mentioned friction ring may also be provided on the 
end of the bore which faces away from the brake disk or is on the inside; 
finally a simultaneous arrangement on the inner and outer end may also be 
advantageous. 
According to the advantageous further development of the invention, the 
required braking torque for the respective adjusting spindle may as an 
alternative be achieved by a counternut which is disposed in a 
rotationally secured manner on the respective threaded spindle and is 
spring-loaded in the axial direction. This arrangement can also be 
provided in a very cost-effective manner and, in contrast to the 
previously explained embodiment, has the advantage that, also after an 
extended operating time, no replacement will be required so that its 
maintenance friendliness will be correspondingly high. 
As an alternative, it is also possible to achieve the braking torque 
required for the respective adjusting spindle by a spring arranged in the 
force transmission path between the adjusting arrangement and the threaded 
spindle. The spring correspondingly increases the frictional torque of the 
force transmission path. This spring may, for example, be a coil spring 
which is wound around the drive shaft of the threaded spindle and which 
acts in the axial direction on a gearwheel disposed on the end of the 
drive shaft so that a corresponding braking torque is exercised on the 
force transmission which prevents the threaded spindle from automatically 
rotating. By this arrangement a countertorque is continuously exercised on 
the force transmitting elements of the synchronization device. Because of 
the achieved prestressing of the force transmitting elements, an increased 
wear of these elements is avoided during shaking stress. 
As another alternative, the coil spring wound around the drive shaft of the 
threaded spindle may be designed such that it is fastened at its one end 
to the housing of the application device and at its other end is actuated 
by the rotary lever. The actuating of the respective end of the coil 
spring is constructed such that a torque is exercised on the drive shaft 
only in the released condition of the brake. This arrangement is therefore 
suitable where the adjusting device and/or the synchronization device are 
to be subjected in the operation to braking torques which are as low as 
possible or in the case of which a high efficiency is endeavored. 
For a two spindle embodiment which includes a synchronization device for 
causing the synchronous adjusting rotational movement, the above-mentioned 
object of the invention may also be achieved in that a device is provided 
which locks the synchronization device in the released condition of the 
brake. Also in the event of a strong shaking stress or the like, the 
locked synchronization device prevents unintentionally rotation of the two 
adjusting spindles. A change of the ventilating play when the brake is 
released is therefore excluded under any circumstances. 
When the synchronization device is formed essentially by several 
gearwheels, the endeavored locking of the synchronization device may be 
achieved, for example, by a disk formed from an elastomer material if care 
is taken that one of the gearwheels is pressed in the released condition 
of the brake against this disk in such a manner that the synchronization 
device is locked. It is possible, for example, to actuate a leaf spring by 
the rotary lever. The leaf spring presses the concerned gearwheel in the 
released condition of the brake against the disk. 
However, when a type of synchronization device is provided in which a 
transmission device is used in the form of a link chain or of a toothed 
belt, it is recommended to cause the desired locking of the 
synchronization device by providing an element which is actuated by the 
rotary lever and which is disposed in a slidable manner. This element 
presses the link chain and the toothed belt in the released condition of 
the brake against a guide. For this purpose, a pin may be elastically 
fastened, for example, on the rotary lever. This pin projects into the 
housing of the transmission device and, when the rotary lever is actuated, 
releases the slidably disposed element. Thus, it is achieved in a space- 
saving and reliable manner that the adjusting spindles, which are coupled 
with a transmission device, do not rotate in an unintended fashion. 
According to another independent aspect of the invention each adjusting 
spindle is provided on its brake--disk-side end with a frontal toothing 
which engages in a corresponding frontal countertoothing of its pressure 
piece. When the depth of the teeth of the frontal toothings is selected 
such that it corresponds to the desired ventilating play of the brake, the 
concerned adjusting spindle cannot rotate before the ventilating play is 
larger than this desired value. An unintended adjustment of the adjusting 
spindle or of the ventilating play during shaking stress is therefore 
excluded.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In order to illustrate the problems on which the invention is based, the 
basic construction and method of operation of the disk brake of the above- 
mentioned type and its application device will be explained in detail. 
As illustrated in FIGS. 1A and 7A, a caliper 2 reaches around an 
(internally ventilated) brake disk 1 which is fastened to a axle of a 
commercial vehicle which is not described in detail. According to FIG. 1A, 
the caliper 2 is disposed by a rigid guide bearing 52 and a differential 
bearing 50 to move axially with respect to the brake disk 1 at the 
vehicle. The construction and function of the caliper are known so that 
they do not have to be explained in detail. 
On the upper side of the brake disk, which is on the right in FIG. 7A and 
on top in FIG. 1A, a two-spindle application device is arranged, which 
diagrammatically has the reference number 3. In the caliper 2, an 
essentially semicircular pivot bearing 30 is provided whose axis of 
rotation extends in parallel to the plane of the brake disk 1 and which 
receives the correspondingly rounded area of a rotary lever 4 so that the 
rotary lever 4 can be swiveled in parallel to the plane of the brake disk 
1. For actuating the rotary lever 4, a brake cylinder 42 is provided which 
is shown only diagrammatically, includes of a piston which engages in a 
suitably shaped recess of an actuating arm 4a of the rotary lever 4. When 
the brake cylinder 42 is acted upon by compressed air, the actuating arm 
4a of the rotary lever is therefore moved from a shown inoperative 
position in the representation of FIG. 7A towards the left. It is noted 
that the actuating of the rotary lever 4 may naturally also take place by 
a brake linkage so that the brake cylinder 42 may optionally be placed at 
a different location if the installation space of the brake disk is 
limited. 
The side of the rotary lever 4 which faces away from the half-shell-shaped 
pivot bearing 30 is coupled by an eccentric 6 serving as a cam with a 
traverse member 7. The traverse member 7 extends within the caliper 2 
essentially in parallel to the axis of rotation of the brake disk 1 and is 
slidably disposed in this plane. On its end which faces the brake disk 1, 
the traverse member 7 has a blind-hole-type recess which is surrounded by 
a tube-shaped projection projecting in the direction of the brake disk 1. 
This projection of the traverse member 7 is slidably disposed in a 
corresponding recess of the caliper 2 at a right angle to the plane of the 
brake disk 1 while maintaining such a play that the traverse member 7 can 
carry out slight swivel movements in the plane of projection. Within the 
recess, a coil spring 78 is arranged which is clamped between the traverse 
member 7 and the end of the caliper 2 which faces the brake disk 1 and 
therefore prestresses the traverse member 7 in the direction of the rotary 
lever 4. 
As illustrated particularly in the longitudinal sectional views of FIGS. 
1A, 2A, 3A and 4A, the traverse member 7 has a bore which is provided on 
both sides with one internal thread respectively into which bore one 
adjusting spindle 70 or 71 respectively can be screwed in a adjustable 
manner. The adjusting spindle's external thread is guided in a 
correspondingly shaped internal thread of the traverse member 7. On the 
end of each of the adjusting spindles 70 and 71 facing the brake disk 1, a 
pressure piece 72 and 73 is fastened which widens in a conical manner. 
Since the two adjusting spindles 70 and 71 extend perpendicularly to the 
plane of the brake disk 1, the pressure pieces 70 and 73 rest by their 
flat ends against a brake shoe 10. Particularly in the circumferential 
direction of the brake disk 1, the brake shoe 10 is guided to be 
displaceable transversely to the brake disk 1 by holding devices which are 
not shown. The holding devices may be assigned either to the caliper 2 or 
to a brake anchor plate. 
In the interior of the adjusting spindle 70, an adjusting device (which is 
not shown) is arranged which, because of an axial toothing, is 
non-rotatably coupled with the adjusting spindle 70 and is displaceable in 
the axial direction. The precise construction of a preferred embodiment of 
the adjusting device is described in the initially mentioned German Patent 
Document DE-OS 40 34 165 corresponding to U.S. Pat. No. 5,353,896 so that 
with respect to further details reference is made to the complete content 
of this document. 
During each actuating of the rotary lever 4, the adjusting device is 
rotated by a certain angular amount, whereby a continuous adjusting of the 
brake is ensured. The exact construction of such a rotary drive device for 
the adjusting device is described in German Patent Document DE-OS 42 04 
307 of the Assignee of the applicant so that with respect to further 
details reference is made to the complete content of this document. 
However, it should be pointed out that the type of rotary drive of the 
adjusting device is not important for the invention. It is only important 
that during each operating of the brake a sufficiently high adjusting 
torque is generated and is transmitted to the adjusting device. 
In the interior of the opposite adjusting spindle 71, no adjusting device 
is arranged but only a driving device which is formed of a gearwheel 713 
(see, for example, FIG. 4B) which engages in a corresponding axial 
toothing of the adjusting spindle 71 and is fastened on a drive shaft 711 
which is disposed in the housing in a bearing 712, which is illustrated in 
FIG. 2B. As was explained at the beginning, it is also possible as an 
alternative to provide in the adjusting spindle 71 an adjusting device 
which may have the advantage that the overall adjusting torque can be 
doubled. However this solution makes the application device more expensive 
so that preferably the driving device described here will be used. 
For a better understanding of the method of operation of the application 
device according to the invention, its operating principle will be 
explained briefly in the following. When the brake cylinder 42 is acted 
upon by compressed air, the actuating arm 4a is swivelled to the left 
according to FIG. 7A, whereby the eccentric 6 operating at the rotary 
lever 4 is also displaced to the left by a distance reduced corresponding 
to the laws of leverage. For this reason, the traverse member 7 is pressed 
against the prestressing force of the coil spring 78 by this distance in 
the direction of the brake disk 1. The pressure pieces 72 and 73, which 
are fastened to the traverse member 7 by the adjusting spindles 70 and 71, 
overcomes the ventilating play (which in practice amounts to approximately 
0.4 millimeters), and presses the brake shoe 10 against the brake disk 1. 
When the actuating arm 4a is swivelled farther towards the left, the 
caliper is displaced towards the right in FIG. 1 because of the force 
exercised on the brake disk 1 so that finally also the left brake shoe 10 
is pressed against the brake disk 1. The external thread of the adjusting 
spindles 70 and 71 and the respective assigned internal thread of the 
traverse 7 member are dimensioned such that, when pressure is admitted, a 
self-locking occurs against the application direction. Thus, the adjusting 
spindles cannot move away in this direction and the brake pressure is 
maintained until the rotary lever 4 is released. 
After the two brake shoes 10 are displaced by a predetermined distance 
corresponding to a desired ventilating play during brake application, the 
adjusting device is actuated by the rotary lever 4. If the ventilating 
play is adjusted correctly, the two brake shoes 10 will rest against the 
brake disk 1 at this point in time. For this reason, a sliding clutch 
provided in the adjusting device will respond so that the adjusting 
spindle 70 and the adjusting spindle 71 synchronized with it are not 
adjusted. When, on the other hand, an excessive ventilating play exists 
which occurs, for example, after a change of the lining or with an 
increasing wear of the brake shoes, the adjusting spindles 70 and 71 are 
rotated by the adjusting device by a certain distance and therefore bring 
the ventilating play, possibly also after a repeated operating of the 
brake, to the desired value. In this manner, it is ensured that the disk 
brake according to the invention remains operative up to a complete 
abrasion of the brake shoes 10. 
In reference to FIGS. 1A and 1B, a first embodiment of the invention will 
be explained which prevents rotating movement of the adjusting spindles 70 
and 71 even when subjected to a strong shaking stress or the like. Such a 
rotating movement would have the result that the brake shoe 10 facing the 
application device 3 would be pressed closer to the surface of the brake 
disk so that the ventilating play would be reduced correspondingly. In the 
worst case this reduction of the ventilating play could even lead to a 
locking of the disk brakes which must be prevented under any 
circumstances. 
According to FIG. 1B which is an enlarged representation of the cutout 
illustrated in FIG. 1A, a friction ring 80 made of rubber or a similar 
elastomer material is fastened to the lower edge of the threaded bore of 
the traverse member 7 into which the respective adjusting spindle 70 and 
71 is screwed. The inside diameter of this friction ring 80 is slightly 
smaller than the outside diameter of the adjusting spindle 70, 71. For 
this reason, the friction ring 80 exercises a frictional torque on the 
respective adjusting spindle which prevents rotation of the adjusting 
spindle automatically when stressed by shaking. An undesired change of the 
ventilating play can therefore be prevented in a secure manner. 
According to the representation in FIG. 1B, the interior of the application 
device is protected by bellows 90 and an interior sealing lip 91 from the 
entering of water or dirt particles. The interior sealing lip 91 is 
fastened in a recess which surrounds the threaded bore of the traverse 
member 7 on its lower end. A surrounding clamping ring 82 is provided as a 
fastening element which securely holds the sealing lip 91. The clamping 
ring 82 has an additional angular part 81 which according to the 
representation in FIG. 1B is shaped such that a pocket is formed which 
receives the friction ring 80 according to the invention. It is therefore 
possible to securely and precisely place the friction ring 80 by the shown 
relatively minor modification of the fastening of the sealing lip 91. An 
additional sealing affect is also achieved. 
Naturally, it is also possible to arrange the friction ring 80 on the 
outlet in the interior of the housing and on the respective adjusting 
spindle. Optionally, a double arrangement may be considered on the shown 
exterior as well as on the interior outlet of the adjusting spindle. 
FIGS. 2A and 2B show another embodiment of the invention in which an 
automatic rotating of the adjusting spindle is prevented by a counternut 
800. This counternut 800 is arranged slightly above the outlet of the 
adjusting spindle 70, 71 in the interior of the housing and is prevented 
from rotating by a projection, a recess of the like. The type and method 
of the respective rotational securing of the counternut 800 which is 
indicated by an interrupted line on the left-hand side of FIG. 2B is not 
important and can be modified arbitrarily. As also illustrated in FIG. 2B, 
the counternut 800 is prestressed in the axial direction by a disk spring 
801. For this reason, a defined friction occurs between the internal 
thread of the counter nut 800 and the external thread of the shown 
adjusting spindle 71. This friction is defined by the spring force of the 
disk spring 801 which generates the corresponding braking torque. As 
explained, in the case of the above-explained friction ring 80, this 
braking torque is selected such that, on the one hand, an unintended 
rotation of the adjusting spindle can be prevented and that, on the other 
hand, the adjusting movement of the adjusting spindle is not excessively 
impaired. 
The two above-described embodiments of the invention are based on the 
principle that the external thread of the respective adjusting spindle is 
acted upon by a suitable friction torque. In the following, FIGS. 3A and 
3B as well as FIG. 5 describe two additional embodiments of the invention 
which are based on the principle of generating the braking torque to be 
exercised on the adjusting spindles by arranging a spring in the force 
transmission path between the adjusting device and the threaded spindle. 
The spring correspondingly increases the friction torque of the force 
transmission path. 
In the embodiment of this variant of the invention illustrated in FIGS. 3A 
and 3B, a coil spring 810 is provided wound on a spindle 811 mounted on 
the drive shaft 711 of the threaded spindle 71. A first end, which is on 
the right in FIG. 3B, of the coil spring 810 is fastened in a recess of an 
upper housing part 31 of the application device and is prevented from 
rotating. The other or second end of the coil spring 810, which is 
illustrated on the left in FIG. 3B, rests against a pin 813 which is 
fastened to a projection 812 of the rotary lever 4. The coil spring 810 is 
dimensioned such and the position of the pin 813 is selected such that the 
coil spring 810 in the released condition of the brake, applies friction 
torque on the spindle 811 and therefore the drive shaft 711. By way of the 
gearwheel 713 disposed on the lower end of the drive shaft 711 (see FIG. 
4B), the adjusting spindle 71 is therefore prevented from rotating 
automatically during a shaking movement or the like. The second adjusting 
spindle 70 is also prevented from rotating because the locking of the 
drive shaft 711 is transmitted by the synchronization device 5 implemented 
as a chain. 
When the rotary lever 4 is actuated for the purpose of braking, the pin 813 
fastened to it is swivelled in the same manner; i.e. towards the rear 
according to the representation of FIG. 3B. As a result, the coil spring 
810 is finally relaxed to such an extent that it exercises no more 
friction torque on the spindle 811. At this point in time, the drive shaft 
711 is freely rotatable so that, if required, the adjustment can take 
place without any problems. 
FIG. 5 shows a variant of the above described embodiment in which a coil 
spring 815 is provided which is wound around the drive shaft 711 of the 
threaded spindle 71 and which acts in the axial direction on the gearwheel 
713 disposed on the end of the drive shaft 711. Since, by means of its end 
facing away from the brake disk, the coil spring 815 rests against the 
bearing 712 of the drive shaft 711, the coil spring 815 generates an axial 
tension which exercises a corresponding friction torque on the interior 
surface of the gearwheel 713. As a result, the friction torque of the 
whole force transmission path from the adjusting device arranged in the 
left adjusting spindle 71 via the synchronization device 5 across to the 
right adjusting spindle 71 is increased to the same extent. As a result, 
it is also prevented that the two adjusting spindles are adjusted 
unintentionally when acted upon by shaking stress or the like. A change of 
the desired ventilating play is therefore also excluded. 
In comparison to the above-described embodiment, the embodiment of FIG. 5 
offers the additional advantage that, because of its rotational 
elasticity, the coil spring 815 causes a permanent return rotational 
affect which has the result that the corresponding transmission elements 
of the synchronization device 5 are permanently prestressed. Particularly 
when the synchronization device 5, as in the case of the embodiment shown 
in FIG. 7A, 7B, is formed of a train of gears in the form of several 
gearwheels, this prestressing has the effect that the transmission 
elements or gearwheels of the synchronization device 5 are also not 
subjected to increased wear when there is a high shaking stress. 
All above-explained embodiments of the invention are based on the principle 
of applying a certain braking torque to the adjusting spindles 70, 71 at 
least in the released condition of the brake. When, on the other hand, a 
two-spindle application device 5 with a coupled synchronization device is 
provided, as in all embodiments of the invention, it is also possible as 
an alternative to provide a device which locks the synchronization device 
5 in the released condition of the brake. Also in this manner, it is 
achieved that the two adjusting spindles cannot rotate automatically when 
stressed by shaking so that an unintentional change of the ventilating 
play is avoided. In the following, two preferred embodiments of this 
alternative principle of the invention are described. In this embodiment, 
the torque required to rotate the adjusting spindle when locked is 
substantial. 
The first embodiment of this variant of the invention of FIGS. 6A to 6C, 
shows a synchronization device in which the force transmission takes place 
by a transmission device in the form of a link chain 51. As an 
alternative, a toothed belt or the like may also be used. According to 
FIG. 6A, a spring element 830 is fastened on the side of the rotary lever 
4, which faces away from the brake disk. A pin shaped end 832 of the 
spring element 830 extends through a bottom-side opening of the 
synchronization device 5 and rests elastically on a displaceably disposed 
element 831. As illustrated in FIG. 6A, the displaceably disposed element 
831, because of the spring force of the pin 832, presses the corresponding 
section of the link chain 51 against a wall or guide of the housing of the 
synchronization device 5. The link chain 51 is therefore clamped in so 
that it locks and prevents the adjusting spindles coupled with it from 
rotating. 
When, according to the representation in FIGS. 6B and 6C, during the 
application of the brake, the rotary lever 4 is swivelled to its left by 
an actuating rod 41 of the brake cylinder, the pin-shaped end 832 of the 
spring element 830 releases the displaceable element 831 so that this 
element will no longer be spring-loaded. The clamping of the link chain 51 
is therefore terminated so that the synchronization device can transmit a 
possibly required adjusting movement of the adjusting device. 
Instead of the displaceable element 831, an elastic part may optionally be 
provided which, when the pin 832 is in contact, dents towards the link 
chain to such an extent that this link chain 51 is clamped therein. 
FIGS. 7A and 7B show an embodiment which is provided for the locking of 
such a synchronization device in which the force transmission takes place 
by several gearwheels forming a train of gears. As illustrated 
particularly in FIG. 7B, the center gearwheel 53, for example, of the 
synchronization device 5 is rotatably disposed by a bearing journal 531 in 
a corresponding bearing bore. A leaf spring 840 is disposed on the end of 
the rotary lever 4 which faces away from the brake disk. This leaf spring 
840 contacts in the illustrated released condition of the brake the lower 
end of the bearing journal 531, whereby the gearwheel 53 is acted upon by 
an outwardly directed axial pressure. On the side of the housing cover of 
the synchronization device 5 facing the exterior side of the gearwheel 53, 
a disk-shaped element 841 is fastened which is made of an elastomer 
material. Since the gearwheel 53 is provided on its exterior surface with 
a frontal toothing or the like, the gearwheel 53, because of the pressure 
exercised by the leaf spring 840, is braked by the elastomer disk 841. The 
synchronization device 5 is therefore blocked so that an unintentional 
rotation of the adjusting spindles is prevented. When the rotary lever 4 
is swivelled to the left during the operation of the brake, the leaf 
spring 840 disengages from the lower end of the bearing journal 431 of the 
gearwheel 53, whereby the gearwheel 53 is no longer braked by the disk 
841. The gearwheel 53 can therefore rotate in an unimpaired manner so that 
the synchronization device 5 can transmit a possibly required adjusting 
movement to another adjusting spindle. 
The elastomer disk 831 may consist, for example, of a rubber material. 
FIGS. 4A and 4B also show another embodiment of the invention in which the 
end of the adjusting spindle 71 on the side of the brake disk is provided 
with a frontal toothing 821 which engages in the corresponding frontal 
counter toothing 820 on its pressure piece 73. Because of its contact with 
the brake shoe 10 as well as because of the clamping-in by the bellows 90, 
the pressure piece 73 cannot rotate. Thus, the adjusting spindle 71 is 
also prevented from rotating so that during a shaking stress no 
unintentional adjustment of the ventilating play can take place. The tooth 
depth of the frontal toothing 820 and 821 is selected such that it 
corresponds to the desired ventilating play. When the ventilating play, 
because of the abrasion of the brake shoes 10, exceeds the desired 
ventilating play, the two frontal toothings will disengage when torqued so 
that the adjusting device can rotate the adjusting spindles for a new 
adjustment of the desired ventilating play. Also, during an extreme 
shaking stress a constant desired ventilating play will always exist. In 
this embodiment, the torque required to rotate the adjusting spindles is 
substantial. 
In the embodiment of FIGS. 4A and 4B, the frontal toothing is provided only 
in the fight adjusting spindle 71 which is coupled by the synchronization 
device 5 with the left adjusting spindle 72. However, optionally it may 
also be considered to equip the left adjusting spindle 72 and its pressure 
piece 74 with a corresponding frontal toothing. Although, this is not 
absolutely required because of the coupling by the synchronization device 
5. 
Although the invention was explained for a two-spindle application device 
it may, with the exception of the embodiments aimed at the synchronization 
device 5, naturally also be used in a single-spindle application device. 
The invention can also be used in a type of synchronization device in which 
a shaft is provided which extends essentially in the area of the axis of 
the eccentric and which has a conical gearwheel on each front side which 
mates with a corresponding conical gearwheel of the adjusting device so 
that a corresponding angle drive is formed. This shaft, which replaces the 
above- mentioned toothed belts or link chains requires no additional space 
so that the synchronization device can be installed in the interior of the 
application device without any significant influence on the space 
conditions. In this case, it is also possible to lock the shaft and 
therefore the synchronization by suitable possibly rotary-lever-actuated 
clamping devices, as required or in the released condition of the brake. 
With respect to further details of such a synchronization device, 
reference is made to the complete content of the applicant's Assignee's 
German Patent Document DE-OS 43 08 704. 
Although the present invention has been described and illustrated in 
detail, it is to be clearly understood that the same is by way of 
illustration and example only, and is not to be taken by way of 
limitation. The spirit and scope of the present invention are to be 
limited only by the terms of the appended claims.