B60D1/24—Traction couplings; Hitches; Draw-gear; Towing devices characterised by arrangements for particular functions
B60D1/30—Traction couplings; Hitches; Draw-gear; Towing devices characterised by arrangements for particular functions for sway control ; Sway alarm means
B60D1/34—Traction couplings; Hitches; Draw-gear; Towing devices characterised by arrangements for particular functions for sway control ; Sway alarm means involving springs
B60D1/345—Traction couplings; Hitches; Draw-gear; Towing devices characterised by arrangements for particular functions for sway control ; Sway alarm means involving springs the springs being of the bar or leaf type