Many types of headrests are known which include a cushion whose position relative to the back-rest of the seat is adjusted by moving a pair of brackets in sleeves, with some of them having the brackets fixed firmly to the cushion in which case the sleeves are fixed in the back-rest of the seat, whereas others have the brackets firmly fixed in the backrest of the seat in which case the corresponding sleeves are seated in the supporting structure of the cushion. At least one bracket is equipped with a series of positioning cavities used with an elastic element placed in the collar of the sleeve. Some sleeves have buttons placed in the collar which control the retracting movement of the elastic element from the positioning cavity in order to enable headrest position change. In the known solutions the elastic element used with the positioning cavities has the form of a spring bent in such a way as to have a shape similar to the shape of the letter U, while one of its arms is fixed in the collar of the sleeve and the other one is used with the cavities. This active arm can be released with the control button.

This solution has the disadvantage of allowing uncontrolled movement of the active end of the spring out of the positioning cavity during a road accident, which may cause a change in the position of the headrest and subsequently result in a situation where the head of the user is not protected during rapid backward movement.

The aim of the invention is to eliminate the fault of the known solutions by designing a position adjustment unit which would be reliable in operation and at the same time simple in terms of manufacturing requirements and subsequently which would represent an optimal economical solution.

This aim has been achieved by equipping the collar of the sleeve with an elastic element bent to have the known shape of the letter U, whose working parts in both arms are designed for use with positioning cavities. In one version these are two series of positioning cavities placed at the opposite sides of the longitudinal axis of symmetry of the bracket. In the other version the positioning cavities are made as perimeter cavities. The elastic element is placed in the known slidable, spring- supported controlling element whose button is situated outside the collar of the sleeve.

The advantage of this solution is the ability to ensure that at least one arm of the elastic element remains in contact with the corresponding positioning cavity in a road accident situation, which subsequently ensures that the head of the user is protected against rapid backward movement.

The object of the invention in the example version is explained in greater detail in the drawing in which Fig. 1 shows the sleeve in section view, Fig. 2-the collar in C-C section view, and Fig. 3 the bracket with its perimeter positioning cavities.

The position adjustment unit as per the invention consists of a bracket 1 equipped with two series of positioning cavities 2 and 2'placed at the opposite sides of the transverse axis of symmetry 3 of the bracket 1 and the positioning spring 4.

The bracket 1 is placed within a sleeve 5. The sleeve 5 in the collar 6 contains a controlling element 7 placed slidably and supported with a spring 8. In the controlling element 7, there is a positioning spring 4 with a shape similar to the shape of the letter U, whose both arms are used with corresponding positioning cavity 2 and 2'of the bracket 1.

The operation of the position adjustment unit is shown below.

In order to change the position of the headrest usually from a higher position to a lower one in relation to the back-rest of the seat, it is necessary to move the control element 7 along with the positioning spring 4 it contains, inside the collar 6 of the sleeve 5, which will result in the working parts of the arms of the positioning spring 4 moving out of the positioning cavities 2 and 2'of the bracket 1. After force is applied to the cushion of the headrest and after selecting another position pressure is no longer applied on the controlling element 7 which under the action of a spring 8 returns to its initial position and the working parts of the arms of the positioning spring 4 come into contact with another pair of positioning cavities on the bracket 1.