Longitudinal seat adjuster

1. A seat length adjuster ( 3 ), especially for a vehicle seat, comprising at least:

two rail pairs ( 10 ) arranged at a distance from each other, formed respectively by two rails, an upper rail ( 11 ) and a lower rail ( 12 ),

wherein the upper rail ( 11 ) is provided with openings ( 16 , 16 ′) and the lower rail ( 12 ) has through holes ( 14 ), and

at least one spring-loaded, movable locking member ( 21 ), which is held on the upper rail ( 11 ) and which blocks a movement of the upper rail ( 11 ) in the lower rail ( 12 ) in a locked position (VS), and which carries toothlike protrusions ( 15 ) on its two opposite lengthwise sides, which are movable from a released position (FS) into the locked position (VS) both into the openings ( 16 ) and into the through holes ( 14 ),

wherein the locking member ( 21 ) secures the upper rail ( 11 ) and lower rail ( 12 ) in the locked position (VS),

wherein the openings ( 16 ) and/or the through holes ( 14 ) have contact regions (K) for the toothlike protrusions ( 15 ) of the locking member ( 21 ) and at least some of the toothlike protrusions ( 15 ) have a respective undercut ( 15 . 1 ) on opposing tooth flanks (ZF 1 , ZF 2 ),

wherein in the locked position (VS) of the locking member ( 21 ) a projecting edge ( 15 . 2 ) resulting from the undercut ( 15 . 1 ) on the respective tooth flank (ZF 1 , ZF 2 ) lies opposite the contact region (K) in the respective opening ( 16 ) or in the through hole ( 14 ) and/or touches this contact region (K),

wherein the respective opening ( 16 ) and/or the respective through hole ( 14 ) have slanted inner wall surfaces (WF 1 , WF 2 ) facing each other, wherein said slanted inner wall surfaces provide a wider bottom entrance for said opening and/or through hole compared with an upper portion of said opening and/or through hole and the projecting edges ( 15 . 2 ) of the two tooth flanks (ZF 1 , ZF 2 ) of at least one of the toothlike protrusions ( 15 ) in the locked position (VS) lie against the upper portion of the inner wall surfaces (WF 1 , WF 2 ) in the respective contact region (K) without a gap or lie opposite this contact region (K) with a gap (S);

wherein said undercut provides said at least some of said toothlike protrusions with a T-shape, wherein a vertical bar forming said T-shape is located below a horizontal bar forming said T-shape and wherein said horizontal bar has a wider width than a width of said upper portion of said inner wall surfaces for selective deformation of said inner wall surfaces by said horizontal bar to secure said upper rail to said lower rail.

2. The seat length adjuster ( 3 ) as claimed in claim 1 , wherein during a horizontal movement of the upper rail ( 11 ) and lower rail ( 12 ) relative to each other or of the lower rail ( 12 ) and the locking member ( 21 ) relative to each other in a direction of the horizontal movement (X) respectively in the locked position (VS) of the locking member ( 21 ) as a result of a mechanical stress, the projecting edge ( 15 . 2 ) and the contact region (K) are arranged in such a way that the projecting edge ( 15 . 2 ) deforms the contact region (K) and/or penetrates into it.

3. The seat length adjuster ( 3 ) as claimed in claim 1 , wherein the respective projecting edge ( 15 . 2 ) and the corresponding contact region (K) are arranged in such a way that, during a horizontal movement of the upper rail ( 11 ) and lower rail ( 12 ) relative to each other or of the lower rail ( 12 ) and the locking member ( 21 ) relative to each other in the lengthwise direction (X) respectively in the locked position (VS) of the locking member ( 21 ) as a result of a mechanical stress, at least one of the projecting edges ( 15 . 2 ) comes into engagement or into further engagement with the inner wall surface (WF 1 , WF 2 ) in the corresponding contact region (K).

4. The seat length adjuster ( 3 ) as claimed in claim 1 , wherein the respective projecting edge ( 15 . 2 ) and the inner wall surface (WF 1 , WF 2 ) are arranged in such a way that, during a horizontal movement of the upper rail ( 11 ) and lower rail ( 12 ) relative to each other or of the lower rail ( 12 ) and the locking member ( 21 ) relative to each other in the lengthwise direction (X) respectively in the locked position (VS) of the locking member ( 21 ) as a result of a mechanical stress, the projecting edge ( 15 . 2 ) in the corresponding contact region (K) penetrates into this inner wall surface (WF 1 , WF 2 ) and/or deforms this inner wall surface (WF 1 , WF 2 ).

5. The seat length adjuster ( 3 ) as claimed in claim 4 , wherein the projecting edge ( 15 . 2 ) deforms the corresponding contact region (K) in such a way and/or penetrates into this corresponding contact region (K) in such a way that the locking member ( 21 ) remains in the locked position (VS) between upper rail ( 11 ) and lower rail ( 12 ).

6. The seat length adjuster ( 3 ) as claimed in claim 1 , wherein at least the contact regions (K) of the lower rail ( 12 ) and/or the upper rail ( 11 ) are formed from a softer material than the material of the locking member ( 21 ) and/or the toothlike protrusions ( 15 ).

7. The seat length adjuster ( 3 ) as claimed in claim 1 , wherein all toothlike protrusions ( 15 ) on both tooth flanks have an undercut ( 15 . 1 ).

8. The seat length adjuster ( 3 ) as claimed in claim 1 , wherein the undercut ( 15 . 1 ) is introduced into the respective toothlike protrusion ( 15 ) by means of a forming step in a pressing tool by means of a cutting gap or in a punching tool or in an embossing tool by means of a punch or in a cutting press tool or by means of shaping.

9. The seat length adjuster as claimed in claim 1 , wherein a material strength of the toothlike protrusion is higher than a material strength of the inner wall surfaces.