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A locking apparatus, particularly of a parking brake device for a vehicle with an automatic transmission, which has a piston unit positioned inside a housing and is axially displaced and locked in a pre-defined axial position, and a catch device that automatically activates when the piston unit is l

A locking apparatus, particularly of a parking brake device for a vehicle with an automatic transmission, which has a piston unit positioned inside a housing and is axially displaced and locked in a pre-defined axial position, and a catch device that automatically activates when the piston unit is locked to hold the piston unit. The catch device has at least one spring arm actively connected with the piston unit when the piston unit is locked, the spring arm abuts the piston unit in locked position with a catch area. The spring arm has a recess in a longitudinal plane of the spring arm. The piston unit penetrates the recess of the spring arm at least approximately in a radial direction with a section that forms the catch area, so that when the piston unit is locked, the catch area within the longitudinal plane of the spring arm.

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1. A locking apparatus (1) of a parking brake device for a vehicle having a drivetrain with an automatic transmission, the locking apparatus comprising: a piston unit (4) positioned inside a housing (3) and being axially displaceable and lockable in a pre-defined axial position; anda catch device (5

1. A locking apparatus (1) of a parking brake device for a vehicle having a drivetrain with an automatic transmission, the locking apparatus comprising: a piston unit (4) positioned inside a housing (3) and being axially displaceable and lockable in a pre-defined axial position; anda catch device (5) being automatically activated when the piston unit (4) is in a locked position to hold the piston unit (4), the catch device (5) having at least one spring arm (5A, 5B) in active connection with the piston unit (4) when the piston unit (4) is in the locked position, the at least one spring arm being abutted by the piston unit (4) in the locked position with a catch area (27), the at least one spring arm (5A) being substantially planar and comprising a radially outer surface which defines a longitudinal plane, and the spring arm (5A) having a through hole (41) extending radially through the spring arm (5A) and the catch area (27) of the piston unit (4) extends at least partially, in a radial direction, through the through hole (41) of the spring arm (5A) so that when the piston unit (4) is in the locked position, the catch area (27) of the piston unit (4) intersects the longitudinal plane defined by the outer surface of the spring arm (5A). 2. The locking apparatus according to claim 1, wherein a contact surface (26) of the spring arm (5A) abuts the catch area (27) of the piston unit (4) and is a side surface that limits an axial extent of the through hole (41) in the longitudinal plane of the spring arm (5A). 3. The locking apparatus according to claim 1, wherein the through hole (41) extends radially through the spring arm (5A) and is manufactured by a punch method. 4. The locking apparatus according to claim 1, wherein the through hole (41) is manufactured by sectionally punching and bending a lug (42) with respect to the longitudinal plane of the spring arm (5A), where the piston unit (4), in the locked position, contacts the lug (42), which has been bent out of the longitudinal plane of the spring arm (5A) and loads the lug (42) in the direction of bending. 5. The locking apparatus according to claim 3, wherein a punch radius (R41A, R41B) in a contact surface area has a radius which minimizes a stress placed on a lug (42) by a holding force applied on the lug (42) by the catch area (17) of the piston unit (4). 6. The locking apparatus according to claim 1, wherein the spring arm (5A), at least in sections, comprises a planar longitudinal support area (33) and radial and tangential bends (32) such that the spring arm has a substantially U-shaped cross-section. 7. The locking apparatus according to claim 1, wherein the spring arm (5A) is at least sectionally designed with at least one stiffening bead (34) that extends axially along the spring arm (5A) and laterally adjacent the through hole (41). 8. The locking apparatus according to claim 1, wherein the spring arm (5A) is at least sectionally designed with at least one stiffening area (35A, 35B) that extends basically in the longitudinal direction of the spring arm (5A). 9. The locking apparatus according to claim 1 wherein, between a contact surface (26), which when the spring arm (5A) is installed, overlaps with the catch area (27) of the piston unit (4), and at least a linear contact exists in the catch area (27) of the piston unit (4) when the catch device (5) is activated. 10. The locking apparatus according to claim 9, wherein the contact surface (26) of the spring arm (5A) has a curved contour that corresponds to a curved exterior shape of the piston unit (4) such that an area of overlap between the catch area (27) of the piston unit (4) and the contact surface (26) of the spring arm (5A) is greater in comparison to an area of overlap between the catch area (27) of the piston unit (4) and a contact surface (26) of another spring arm (5A) having a straight contour that, other than the straight contour, is identical to the spring arm (5A) having the curved contour. 11. The locking apparatus according to claim 9, wherein the contact surface (26) and the catch area (27) within a region of overlap are each designed such that a plane (15), which is normal to a direction of motion of the piston unit (4), and a contact plane (16) of the overlap region intersect between the catch area (27) and the contact surface (26) at operational load at an angle (a) of 0° to 5°. 12. The locking apparatus according to claim 1, wherein the spring arm (5A) is manufactured from spring steel. 13. The locking apparatus according to claim 1, wherein the least one spring arm (5A, 5B) is parallel to the central axis when the piston unit (4) is in the locked and an unlocked positions. 14. A locking apparatus (1) of a parking brake device for a vehicle having a drivetrain with an automatic transmission, the locking apparatus (1) comprising: a piston unit (4) located within a housing (3) and being slidable along a central axis between a locked position and an unlocked position, the piston unit (4) having a catch (27) with a catch surface that extends essentially normal to the central axis;a catch device (5) having at least one spring arm (5A, 5B, 5C) that is substantially planar and comprises a radially outer surface, axially opposite ends, and a through hole (41), the outer surface being radially opposite the central axis and the through hole (41) being axially located in the at least one spring arm (5A, 5B, 5C) between the axially opposite ends and radially extending completely through the at least one spring arm (5A, 5B, 5C), the outer surface of the at least one spring arm (5A, 5B, 5C) defining a longitudinal plane which is parallel to the central axis, the at least one spring arm (5A, 5B, 5C) comprises a contact surface (26) that extends radially inward from the outer surface and essentially normal to the longitudinal plane; andthe catch surface of the piston unit (4) passes, via the through hole (41), through the at least one spring arm (5A, 5B, 5C) and the longitudinal plane and abuts with the contact surface (26) of the at least one spring arm (5A, 5B, 5C) to automatically engage and retain the piston unit (4) when the piston unit (4) is in the locked position. 15. The locking apparatus according to claim 14, wherein a remote end of the contact surface (26) of the at least one spring arm (5A, 5B, 5C) has arcuate contour when viewed from along the central axis. 16. The locking apparatus according to claim 14, wherein longitudinally opposite sides of the at least one spring arm (5A, 5B, 5C) comprise bends (32) that define planes which are essentially parallel to the central axis. 17. The locking apparatus according to claim 1, wherein longitudinally opposite sides of the at least one spring arm (5A, 5B, 5C) are axially bent such that the opposite sides are at an angle with respect to the longitudinal plane. 18. The locking apparatus according to claim 14, wherein the through hole (41) has a profile along the longitudinal plane which comprises punch radii located at opposite sides of the contact surface (26). 19. The locking apparatus according to claim 14, wherein the at least one spring arm (5A, 5B, 5C) is parallel to the central axis when the piston unit (4) is in the locked and the unlocked positions. 20. The locking apparatus according to claim 14, wherein the at least one spring arm (5A, 5B, 5C) comprises a portion of the at least one spring arm (5A, 5B, 5C) that is bent with respect to the longitudinal plane of the spring arm (5A), the contact surface (26) being the outer surface of the portion of the at least one spring arm (5A, 5B, 5C) that is bent with respect to the longitudinal plane, the catch surface of the piston unit (4), in the locked position, contacts the contact surface and loads the portion of the at least one spring arm (5A, 5B, 5C) that is bent with respect to the longitudinal plane.