Parking brake device of a railway vehicle having high efficiency

A brake device for a railway vehicle, comprising:

• at least one service brake cylinder having at least one service brake piston actuated by a pressurized medium, said piston actuating a service brake piston rod coaxial with a brake cylinder axis;
• and
• a pivotably mounted actuating lever, the rotary motion of which being transmitted to a shaft arranged perpendicularly to the brake cylinder axis and rotatably mounted on a housing by at least one shaft bearing,
• wherein the rotary motion of the shaft induced by the actuating lever is converted to a linear motion, directed parallel to the brake cylinder axis, of at least one support roller rotatably mounted, by a support roller bearing, on a rotational axis arranged parallel to the shaft as a result of at least one cam connected to the shaft for conjoint rotation therewith and provision of an effective cam surface interacting with a radially outer support roller surface of the support roller during an application or release stroke of the parking brake device,
• wherein the linear motion of the support roller is transmitted to the service brake piston rod,
• wherein the effective cam surface is designed as a circumferential segment of a cylindrical surface, a center axis of the cylindrical surface following a circular path of motion about a shaft axis during an application or release stroke of the parking brake device, wherein a transmission ratio is smallest at the beginning of an application stroke,
• wherein a point of intersection of said path of motion with the brake cylinder axis exists that is associated with a maximum parking brake force,
• wherein the at least one cam is one of two cams, which are arranged symmetrically with respect to the brake cylinder axis are connected to the shaft for conjoint rotation therewith and constitute involute contoured cams,
• wherein the at least one support roller is one of two support rollers, wherein the two involute contoured cams each have an involute contour arranged on the shaft and are in engagement on both sides of a piston rod tube and interact with the two support rollers mounted on the piston rod tube, wherein the two support rollers are arranged symmetrically with respect to the brake cylinder axis, and
• wherein the two cams and the two support rollers are rotatable about a common rotational axis.