Sand spreader on a rail vehicle

A sand gritting system for a railway vehicle has a vertical hopper with a tapering bottom end (2) to duct sand to a pneumatic dosing valve to a Venturi valve (7) to mix into a vertically downwards directed air stream. The sand is ducted into a mixing chamber (5) by radial ducts (6) and with the flow rate controlled by a rotating sleeve with an outer control flange (9). The compressed air feed (17) is ducted to the top of the valve from where it is ducted vertically downwards. The sand and air mixture is ducted vertically onto the rails.