A hopper for a weighing machine which has a tubular body and a closing valve which is comprised of several plates which are pivotably mounted around the bottom of the hopper for movement in a plane transverse to the axis of the hopper. The plates are simultaneously driven between open and closed positions by a common belt or chain so that the closing forces of the plates are balanced. The belt is coupled to a driving mechanism through a lever mounted on the hopper which disconnects from the driving mechanism when the plates are fully closed so that the hopper is freely suspended for weighing purposes. The plates scrape against the bottom of the hopper when opening so that material clinging to the plates is scraped off.