The jack for the change of a position of the seat base in a wheelchair, characterized by the fact that in the lower frame ( 1 ) the driving system of the screw jack with a vertical screw ( 14 ) is fixed； and the upper end of the screw ( 14 ) is pivotally fixed in the main arms (3) of the scissors system. The driving system of the screw ( 14 ) of the screw jack is fixed to the base ( 11 ) attached slideably to the lower frame ( 1 ) in the tracks ( 8 ) in such a way that the screw ( 14 ) is permanently in a perpendicular position to the lower frame ( 1 ) and the upper frame ( 2 ) with maximum deviation of ±10°； and the base ( 11 ) is driven by the arms ( 17 ), with their first ends fixed pivotally in the main arms ( 3 ), and the other ends fixed pivotally in the base ( 11 ). The driving system of the screw ( 14 ) of the screw jack consists of the engine ( 9 ), which drives the nut ( 10 ) of the screw jack by means of gear transmission, and in the gear transmission a small wheel ( 13 ) is positioned on the engine pivot ( 9 ), and the big wheel ( 12 ) is joined coaxially with the nut ( 10 ). The engine ( 9 ) is an electric engine. In the driving system of the screw jack two engines ( 9 ) are used, simultaneously geared with a gear wheel ( 12 ), of the nut ( 10 ). The driving engines (9) are electric engines. The screw (14) of the screw jack is fixed to the main arms ( 3 ) by means of a bed ( 15 ) fixed pivotally in the main arms ( 3 ) of the scissors system.
