Headrest

1. A headrest retained on a vehicle seat part, the headrest comprising:

at least one headrest adjustment part carried on and movable relative to the seat part;

at least one drive mechanism for moving the adjustment part relative to the seat part and comprising a first drive having at least one first drive element that is fixed to the adjustment part and a second drive having a second drive element that is fixed to the seat part;

an overload safety device having a coupling connected between one of the drive elements and the respective part and movable between a coupling position coupling the one drive element to the respective part and a decoupling position decoupling the one drive element from the respective part when a force acting on the adjustment part exceeds a limit;

a latch in the overload safety device and movable between an unlocked position permitting movement of the adjustment part and a locked position blocking movement of the adjustment part; and

a connection between the coupling and the latch that moves of the latch from the unlocked position into the locked position by movement of the coupling from the coupling position into the decoupling position.

2. The headrest defined in claim 1 , wherein the drive elements are a spindle and a spindle nut engaged by the spindle.

3. The headrest defined in claim 2 , wherein the overload safety device has a spring that holds the device in the coupling position and, when the maximum force is exceeded, the device can be moved into the decoupling position by deformation of the spring.

4. The headrest defined in claim 3 , wherein the spring is provided with first frictional connecting elements that can be engaged with second frictional connecting elements of a spring seat part in a frictionally connected releasable manner.

5. The headrest defined in claim 1 , wherein the latch has at least one first locking element that is fixed to the seat part and that can be engaged with at least one second locking element that is fixed to the adjustment part.

6. The headrest defined in claim 5 , wherein the first locking element is formed by a slide and the second locking element by gear teeth.

7. A headrest that is retained on a vehicle seat part, the headrest comprising:

at least one adjustment part carried on and movable relative to the seat part;

at least one drive mechanism for moving the adjustment part relative to the seat part and comprising a first drive having at least one first drive element that is fixed to the adjustment part and a second drive having a second drive element that is fixed to the seat part and that directly and permanently engages the first drive element, the drive elements being a spindle and a spindle nut thereon; and

an overload safety device connected between one of the drive elements and the respective part and movable without disengaging the drive elements from each other between a coupling position coupling the one drive element to the respective part and a decoupling position decoupling the one drive element from the respective part when a force acting on the adjustment part exceeds a limit for, in the decoupling position of the overload safety device, at least partially relieving the drive mechanism of the force acting on the adjustment part, the overload safety device having on the spindle nut a spring that holds the overload safety device in the coupling position and, when the maximum force is exceeded, allows the device to move into the decoupling position by deformation of the spring.