A child safety seat (1) comprising an extendible protective element (10),
wherein the extendible protective element (10) comprises:
a first thread component (11) comprising a first external thread (11 a) and a first internal thread (11 b), and
a second thread component (12) comprising a second external thread (12a);
wherein the first thread component (11) is rotatably connected to the second thread component (12) via the first internal thread (11 b) of the first thread component (11) and the second external thread (12a) of the second thread component (12),
wherein the first thread component (11) is configured to be rotationally coupled to a third internal thread provided in a shell of the child safety seat (1), wherein the first external thread (11 a) of the first thread component (11) is a counter-thread of the third internal thread provided in the shell of the child safety seat (1),
wherein a friction occurring between the first internal thread (11 b) of the first thread component (11 ) and the second external thread (12a) of the second thread component (12) when rotated relatively to each other is different from a friction occurring between the first external thread (11 a) of the first thread component (11) and the third internal thread provided in the shell of the child safety seat (1) when the first thread component (11) is rotated relatively to the third internal thread.