Pumping apparatus

A process for the controlled delivery of a pumpable material which comprises the steps of:

• providing a pumping apparatus comprising:
• a first cylindrical pumping chamber having an open end adapted to allow the entry of material to be pumped from a common hopper and in connection thereto, and a first movable piston within the pumping chamber connected by a shaft to first hydraulic piston within a first hydraulic piston and cylinder unit wherein the first hydraulic piston divides the interior of the first hydraulic piston and cylinder unit into an upper side and a lower side;
• a second cylindrical pumping chamber having an open end adapted to allow the entry of material to be pumped from said common hopper and in connection thereto, and a second movable piston within the pumping chamber connected by a shaft to second hydraulic piston within a second hydraulic piston and cylinder unit wherein the second hydraulic piston divides the interior of the second hydraulic piston and cylinder unit into an upper side and a lower side;
• a discharge conduit having two ends, one end of which is switchably connectable to the open end of either the first or second cylindrical pumping chamber;
• and a hydraulic circuit which includes;
• a first switching valve having an inlet connected by means of a hydraulic line to a supply of fluid and further having;
• a first outlet connected by means of a hydraulic line to the lower side Of the first hydraulic piston and cylinder unit and in fluid communication therewith, and,
• a second outlet connected by means of a hydraulic line to the lower side of the second hydraulic piston and cylinder unit and in fluid Communication therewith,
• a first hydraulic line providing fluid communication with and connecting the upper side of the first hydraulic piston and cylinder unit with the upper side of the second hydraulic piston and cylinder units and further with the inlet of pressure relief valve,
• and,
• a two-way valve having two inlets and one outlet,
• one inlet of which is in fluid connection with the hydraulic line connecting the the first outlet of the first switching valve and the lower side of the first hydraulic piston and cylinder unit,
• the second outlet of which is in fluid connection with the with the hydraulic line connecting the the second outlet of the firsts switching valve and the lower side of the second hydraulic piston and cylinder unit,
• and, the outlet of which is in fluid connection with a the said first hydraulic line,
• and;
• operating the hydraulic circuit to bring the first pumping piston to a position within the first cylindrical pumping chamber wherein iris fully charged with material to be pumped from the common hopper prior to the complete discharge of the material from the second pumping piston.