2. Prior art The prior art provides different solutions for parking brakes and handbrakes.

Parking brakes for motor vehicles in general act on the back tires of the vehicle and are activated via a sheathed cable. The brake can either be operated by a hand lever or a foot pedal. Since the operating of the parking brake partly needs a substantial effort, it is not operated as required by particularly elderly drivers.

Therefore, on the one hand a safety risk occurs, since the vehicle could roll away while parking and on the other hand the use of the parking brake is uncomfortable. To reduce this effort and to provide a comfortable operation of the parking brake, parking brakes are known in the prior art, which are for example driven by an electric motor instead manually.

So the DE 198 18 339 Cl discloses a braking system in which the brakes are operated by a cable roll, driven by an electric motor. The ends of the braking cable assemblies of the back tires are therefore connected to the opposing sides of the circumference of the cable roll. During rotation of the cable roll, equal distances of both braking cables are simultaneously rolled up to the cable roll and thereby the back tires are uniformly braked. It is a disadvantage to costly adjust the length of the braking cables, in order to guaranty a uniform operation of the brakes. In

addition, the braking cables must regularly be checked and adjusted, as they are disadjusted during use.

A further electric parking brake system for passengers cars is described in WO 98/56633. The document discloses an operating mechanism for parking brakes for passenger cars with an actuating mechanism comprising a motor-powered drive, for example an electric motor, for tightening or releasing of a braking cable of a braking system of the vehicle. The operating mechanism comprises an actuator for the braking cable, adjustable by the drive, which is related to a force measuring mechanism.

From the DE 197 55 933 an operating mechanism for parking brakes for motor vehicles is known, with an actuator comprising a motor-powered drive, for tightening or releasing of braking cable assemblies of a braking system of a vehicle. The drive is in connection with an element, that is rotatable around its longitudinal axis and not displaceable with respect to the longitudinal axis. The element is coupled with a telescopic assembly that is displaceable arranged in direction of the longitudinal axis, wherein the axial length of the telescopic assembly is increased or decreased dependent on the rotational direction of the element. Each of the axial ends of the telescopic assembly is directly or indirectly connected to one braking cable for one brake of the braking system, respectively.

Finally, from the DE 100 43 739.7 a parking brake for motor vehicles is known with at least two braking cable assemblies, comprising an actuator with couple elements, wherein two braking cable assemblies are coupled to this couple elements at two couple locations. Further an operating mechanism is provided, arranged and connected with the actuator in such a way, that the distance of the couple locations can be changed in a controlled manner, whereby a relative movement of the couple locations to or away from each other is enabled.

It is a disadvantage of this construction, that it consists of a plurality of expensively producible components. Moreover, this operating mechanism needs regular maintenance. Therefore, this prior art operating mechanism is comparatively cost effective in manufacturing and maintenance and space consuming because of the complex construction.

It is therefore the technical problem underlying the present invention, to provide an operating mechanism for a parking brake that can easily be manufactured and that guaranties a safe and malfunction free operation.

3. Summary of the invention The present invention solves the above problem by an operating mechanism for operating at least one parking brake, particularly for motor vehicles. The operating mechanism is connected with the brakes via braking cable assemblies and replaces the manual lever brake or a foot pedal. By using the operating mechanism, the brake cables within the braking cable assemblies are motor-driven tightened or released.

The operating mechanism comprises a motor unit for driving the operating mechanism and an eccentric assembly, that transforms the rotational motion of the motor unit into a linear motion, by using the eccentric principle, wherein at least one braking cable is tightened or released for operating the at least one parking brake. The eccentric assembly uses the eccentric principle, whereby rotational motions are transformed into linear motions by means of a crank gear or a cam gear.

In a first preferred embodiment according to the invention the eccentric assembly comprises a cam connected to the motor unit and a tappet displaceable by the cam.

The parking brake according to the invention thus comprises just a few components and is very robust and low maintenance. In addition the operating mechanism can be built very compact and therefore occupies only few space in or at the vehicle. In a first embodiment, the force compensation between both connected brakes is done directly via the braking cable, that is just deviated within the operating mechanism, but remains axial displaceable. Tensile forces, acting on the ends of the braking cables, are compensated. Therefore, the same force acts in each braking cable half and the brakes actuated thereby have the same braking effect.

In a further preferred embodiment, the tappet is arranged between two deviation rolls. The at least one braking cable runs via the deviation rolls and the tappet with low friction. If no deviation rolls are provided, the braking cable is guided over gliding faces. Therefore a lubrication of the gliding faces is needed.

In a further preferred embodiment, the tappet comprises at the cable guiding side a deviation roll for guiding the braking cable and to reduce the friction between tappet and braking cable. Therefore, the braking cable is bedded rolling and not just gliding at the positions within the operating mechanism, where it is deviated.

This facilitates the force compensation between the both braking cable halves and increases the lifetime of the braking cable.

According to a further preferred embodiment of the eccentric assembly according to the invention, the tappet is connected to a first and a second cable holder, displaceable in the direction of the braking cables, wherein by a displacement of the tappet a displacement of the first and the second cable holder is achieved, for tightening or releasing of respectively one braking cable half, connected to one of the cable holders. The cable holders are connected by means of a flexible connecting element, that runs via the tappet. The braking cable is divided in this embodiment. The first cable holder is connected with a first braking cable half and the second cable holder with a second braking cable half, to operate of

respectively at least one brake. The connecting element can glide on the cable guiding end of the tappet and, thus, provides the necessary force compensation between the two braking cable halves. It is one advantage of this embodiment, that both braking cable halves are guided widely straight and are not deviated. The deviated connecting element can be configured stronger compared to the braking cable halves, corresponding to the higher load.

In a further embodiment of the present invention the tappet comprises a deviation roll on the side of the connecting element for guiding the connecting element and for decreasing the friction between tappet and the connecting element. The connecting element therefore is rollingly guided by the deviation roll and not longer glidingly onto the tappet, which reduces the friction at the connecting element.

In a further preferred embodiment of-the invention the cam is shaped so that it comprises an assembly position, with minimal displacement of the tappet, and a working range, in which the at least one braking cable is tightened or released. In case the cam is situated in its assembly position, the braking cable is in its most released condition and therefore it can be easily assembled to the brake.

In a further preferred embodiment, a force measuring device is provided within the operating mechanism to determine the braking force generated by the operating mechanism, wherein said force measuring device is integrated in the braking cable, integrated in the tappet or connected to one deviation roll. The motor unit of the operating mechanism is controlled by an electronics, which receives and interprets signals of the force measuring device. Thereby it is guarantied, that during the automatic tightening of the parking brake a sufficient brake effect is achieved. Further an overload of the operating mechanism as well as the connected braking cables and brakes is prevented.

In a further preferred embodiment, the motor unit comprises a motor and a gearbox connected thereto. Further, according to the invention, the motor is provided as an electric motor and the gearbox is provided as a planetary gear.

Finally, the operating mechanism comprises a housing.

Further preferred embodiments of the invention arise from the dependent claims.

4. Short description of the drawing In the following the preferred embodiments of the present invention are described with reference to the drawing. It shows: Fig. l the operating mechanism according to the invention shown in an open housing; Fig. 2 schematically one preferred embodiment of the operating mechanism according to the invention without a housing; Fig. 3 schematically a further preferred embodiment of the operating mechanism according to the invention in a top view having an open housing.

5. Detailed description of the preferred embodiments The present invention is based on the use of the eccentric principle for tightening or releasing of the at least one braking cable for operating of at least one parking brake. The eccentric principle describes the transformation of rotational into translational motions by the use of crank or cam gears.

In a crank gear this is achieved by positioning a circular disc in a non-centric way on a turning shaft, which transmits the motion to an element to be linearly moved by means of a connecting rod. A crank gear in a combustion engine is an example

for this. In a cam gear the transformation of a rotation into a translation is achieved by the actuating of a linear guided tappet by means of a cam, which is non-symmetric in view of to its rotational axis. This is used for example for the valve control of a combustion engine.

A preferred embodiment of the operating mechanism according to the invention is disclosed in the following with refernce to the drawing shown in Fig. 1.

In a first preferred embodiment, the operating mechanism 1 of the parking brake comprises a motor unit 10,20 and an eccentric assembly 30,40, that tightens or releases the at least one braking cable. Preferably according to the invention, the eccentric mechanism 30,40 is provided as a cam gear. A cam 30 is connected to the output shaft 25 of the motor unit 10,20. The cam 30 moves a displaceable bedded tappet 40, that actuates on the cam opposing side a braking cable 70.

Thereby, the braking cable 70, that is connected to at least one brake, is tightened or released. The braking cable 70 transmits, in this manner, braking forces via two braking cable assemblies (not shown) to the connected brakes. The braking cable 70 is tightened or released by the actuation of the tappet 40 for an uniform operation of the connected brakes. The uniform operation of the connected brakes is achieved, in such a way, that the braking cable within the operating mechanism is in fact tightened and released, but still is displaceably guided via gliding phases and tappet 40. Different operating forces of the connected brakes can compensate themselves directly via the braking cable.

Preferably according to the invention, the operating mechanism 1 is driven by a motor unit 10,20. The motor unit 10,20 is comprised of any desired motor- gearbox-combination or just of a motor. If it should be done without a gearbox a step motor can for example be used as motor, which transforms electrical impulses into a defined angle position of its rotor. Preferably according to the invention, the motor unit 10,20 consists of a motor 10 with a connected gearbox 20. The rotational motion generated by the motor 10 is transformed by the

gearbox 20 so that its number of revolutions is decreased and thereby its torque is increased.

In a first preferred embodiment the motor 10 is an electric motor. Instead of an electric motor, the motor 10 could also be provided as a hydraulic motor or as a pressured air driven motor. The motor 10 drives a gearbox 20 which is preferably connected to motor 10 in this first embodiment. Further arrangements of motor 10 and gearbox 20 are conceivable. The gear box 20 is particularly preferably made as a capsuled planetary gear. Therefore, it is widely maintenance free and malfunction resistant. Additionally, the planetary gear has a compact configuration, so that the complete operating mechanism can be provided compact. The gearbox 20 is provided as a reduction gearbox, wherein the selected reduction of the gear box 20 is adapted to the motor 10. The reduction of the gearbox 20 is preferably chosen so that the motor 10 works in a torque-optimal range. Further, fast operating times can be achieved by an appropriate selection of the reduction of gearbox 20.

The cam 30 is axially mounted to the output shaft 25 of the gear box 20.

Preferably a positive connection is provided between the cam 30 and the output shaft 25 of the gear box 20, to transmit high torques. Preferably according to the invention frictionally engaged connections can be used, for example a shrinking connection. High-strength plastic materials or metals are preferably used as material for the cam 30. According to a preferred embodiment the cam 30 is made of steel. The shape of the cam 30 defines the actuation of the tappet 40 and therefore the tightening and releasing of the braking cable 70. In that way, different tensile forces can be transmitted to the braking cable 70 by different gradients of the cam 30. To this end, the cam 30 can be shaped arbitrarily. In the preferred embodiment according to the invention, the cam 30 is approximately elliptically shaped. In this embodiment, the difference between the largest and the smallest radius of the elliptical profile of the cam 30 corresponds to the maximum translational displacement of the tappet 40.

The cam 30 is shaped so that it comprises an assembly position and an operating range. The assembly position of the cam 30 is qualified in such a way, that the tappet 40 is minimally or not displaced. Therefore, the braking cable 70 is loaded minimally or not, whereby the braking cable can be installed, serviced or adjusted with minimal effort. When the cam 30 moves in its operating range, the tappet 40 is displaced and thereby the braking cable 70 is tightened, for operating the connected brakes, or the braking cable 70 is released for no further operating the brakes. The cam 30 is positioned in its assembly position for installation of the parking brake system. The braking cable 70 is therefore not tightened and can easily be assembled or adjusted. For an operation of the parking brake system, the cam 30 is turned in its operating range. In a first position of the cam 30 in its operating range, the braking cable is tightened so that the brakes are just not operated. A further turning of the cam 30 in the operating range results in an increasing displacement of the tappet 40 and thereby in an increasing tension of the braking cable 70, whereby the brake is operated. The cam 30 is turned in its operating range, until a tension being high enough exists in the braking cable 70 to achieve a sufficient braking effect. The tappet 40 is preferably displaceably bedded, wherein the displacement axis is positioned approximately perpendicular to the rotational axis of the cam 30. The outer surface of the cam 30 glides onto the outer surface of the tappet 40 and moves the same. The tappet 40 is also preferably made of a resistant material, for example steel, and is provided with a gliding face, parallelly positioned to the gliding face of the cam 30. A pressure force from the cam 30 to the tappet 40 is transmitted via these gliding faces. The tappet 40 itself transmits a force to the braking cable 70. Preferably according to the invention it is provided with a cable guiding groove at the cam opposing, rounded side, in which the braking cable 70 is guided. The cable guiding groove is adapted in its profile to the profile of the braking cable 70 and in its shape to the way of the braking cable 70, to avoid friction between braking cable 70 and tappet 40. Thereby, it is also prevented, that the tightened braking cable 70 is slipping from the tappet 40 induced by vibrations.

In a further preferred embodiment, that is shown in principle in Fig. 2, two deviation rolls 50 and 60 are provided which deviate the braking cable 70. The braking cable 70 must be pulled into the operating mechanism 1 for operating the brakes. This is done in such a way, that the tappet 40 deviates the braking cable 70 from its theoretically stretched condition in its assembly position between both deviation rolls 50 and 60, and thereby tightens the braking cable 70. The deviation rolls 50 and 60 are preferably rotatably bedded to avoid friction at the braking cable 70. They are made also of a resistant material, as they are subjected to similar high forces as the tappet 40 or the cam 30. The rotatable axis of the deviation rolls 50 and 60 are oriented so that they are on the one hand almost perpendicular to the motion direction of the tappet 40 and on the other hand almost perpendicular to the motion of the braking cable 70. Each deviation roll 50 and 60 preferably comprises a circumferencial cable guiding groove, adapted to the braking cable 70. Thereby, a safe guidance of the braking cable 70 in the operating mechanism according to the invention is realized.

In a further preferred embodiment of the present invention the tappet 40 is provided with an additional deviation roll 45, which is rotatably arranged at the cam opposing end of the tappet 40. The deviation roll 45 preferably guides the braking cable 70 in a cable guiding groove that is adapted to the braking cable 70.

By a displacement of the tappet 40, the braking cable 70 is displaced via the deviation roll 45 and thereby tightened. The friction between the braking cable 70 and the tappet 40 is minimized by the rotatable bedding of the deviation roll 45.

The force compensation between the brakes connected to both braking cable halves 72 and 74 via the braking cable assemblies is facilitated, since the braking cable can be displaced with lower friction in the operating mechanism.

In a further preferred embodiment according to the invention of the operating mechanism 1 shown in Fig. 3, the tappet 40 is connected to two displaceable cable holders 92 and 94 via a connecting element 110. A displacement of the tappet 40

causes a displacement of the cable holders 92 and 94. The flexible connecting element 110 connects both cable holders 92 and 94 with each other and allows the transmission of a tensile force between each other. It runs on the cam opposing side around the tappet 40 and will be deviated by the tappet 40. The connecting element 110 glides in a first preferred embodiment on the tappet 40 to compensate forces that act respectively to the cable holders 92 and 94.

The flexible connecting element 110 preferably is made rope or band shaped, and produced from a tear-resistant plastic material, composite material or a metal. In this embodiment the braking cable is divided and consists of two braking cable halves 72 and 74, which transmit the braking force via respectively one braking cable assembly to the connected brakes. Both cable holders 92 and 94 are displaceably bedded within the cable holder beds 102 and 104 in the direction of the way of the braking cable halves 72 and 74. The cable holder 92 and 94 connect the braking cable halves 72 and 74 with the connecting element 110. The braking cable halves 72 and 74 are preferably connected to the cable holders 92 and 94 via casted nipples and appropriate notches (not shown). The connecting element 110 is deviated by a displacement of the tappet 40. The cable holder 92 and 94 connected thereto are thereby moved to each other. Thereby, the braking cable halves 72 and 74 are tightened. For releasing the braking cable halves 72 and 74, the cable holders 92 and 94 are moved away from each other. To achieve a force compensation between both brakes, operated via the braking cable halves 72 and 74, the connecting element 110 can glide on the tappet 40, whereby the connected brakes are uniformly operated.

In this preferred embodiment, the braking cable halves 72 and 74 are moved favorably just in direction of the cable. There is no bending of the braking cable halves 72 and 74 which increases the lifetime of the braking cable halves 72 and 74. in spite of that, the connecting element 110 is loaded to the bending load. The connecting element 110, however, is suitable to be bent and to simultaneously

transmit a tensile force, based on its preferred band form according to the invention.

In a further preferred embodiment, the tappet 40 comprises a deviation roll 45 on the side of the connecting element 110, that guides the connecting element 110 and that further reduces the friction between the tappet 40 and a connecting element 110. The deviation roll 45 is rotatably bedded within the tappet 40 and circumferencially adapted to the respectively installed connecting element 110.

Thereby, a safe guidance of the connecting element 110 is guarantied, to prevent the connecting element 110 from slipping from the deviation roll 45 of the tappet induced by vibrations.

As shown in Figure 1, the operating mechanism 1 preferred according to the invention is surrounded by a housing 80, which is shown in an open condition.

The housing 80 is used for the fixing of the components of the operating mechanism 1 and for the assembly of the complete operating mechanism 1 to the vehicle. In addition, it protects the elements of the operating mechanism 1 from environmental influences, since the operating mechanism 1 is preferably mounted according to the invention near to the tires to be braked, and since the mounting position can possibly be at an unprotected position on the outside of the vehicle.

To guaranty a safe operation of the parking brake system, the cable tension within the braking cable 70 or the braking cable halves 72 and 74 is measured by means of a force measuring device in a further preferred embodiment according to the invention. In a first embodiment the tensile load is measured directly within the braking cables 70,72, 74. To this end, the braking cables 70,72, 74 respectively comprise two cable halves, which are connected by means of a translatably bedded force measuring device. In a further preferred embodiment, the force measuring device is integrated into the tapped 40. Therefore the tapped 40 consists of two parts, that are connected via a force measuring device. The one part of the tapped 40 is operated by the cam 30, wherein the other part of the

tapped 40 displaces the braking cable 70 or the connecting element 110. Thereby the pressure force is measured, that is transmitted by the tappet 40. In a third preferred embodiment, the force measuring device is connected to one or both deviation rolls 50 and 60 and measures the force, which acts on the deviation rolls 50 and 60.

The force measuring device is connected electrically with the controller of the parking brake system, to control the braking force. The measuring of the force can be done by a arbitrary physical principle. This can be reached for example by resistance strain gauges, the displacement of a spring or piezo electric gauges.

List of reference signs 1 Operating mechanism 10 Motor 20 Gear box 25 Output shaft of the gearbox 30 Cam 40 Tappet 45 Deviation roll of the tappet 50 First deviation roll 60 Second deviation roll 70 Braking cable 72 First braking cable half 74 Second braking cable half 80 Housing 92 First cable holder 94 Second cable holder 102 First cable holder bedding 104 Second cable holder bedding 110 Connecting element