Process and device for adjusting the quantities of product dosed and dispensed by a doser-dispenser

A process for adjusting the quantities of a liquid or pasty product dosed and dispensed by doser-dispensers, incorporated in an installation for packing dosed product in recipients made by thermoforming a thermoplastic web that are advanced with respect to said doser-dispensers, the doser-dispensers being arranged in a row extending above the thermoplastic web and transversely with respect to the direction of advance of said web containing successive transverse rows of recipients parallel to the doser-dispensers, the recipients advancing step by step with said web in the direction of advance thereof, each doser-dispenser being of the type comprising:

• a first cylinder enclosure having an upper chamber, a lower dosing chamber, a doser piston and an admission valve, said upper chamber having a supply conduit for the product to be dosed, said dosing chamber having an outlet, said doser piston sliding tightly in said first enclosure and separating said upper chamber from said dosing chamber, the doser piston having a central passage which constitutes an admission valve seat in said upper chamber, said admission valve movably mounted to open and close said central passage, said doser piston being movable in said first enclosure between an ascending end-of-stroke position corresponding to an upper position of the doser piston and a descending end-of-stroke position corresponding to a lower position of the doser piston, at least one of the end-of-stroke positions being adjustable,
• a first control tube, and a first control jack having a first piston, a first cylinder and a rod, said first control tube penetrating tightly in said first enclosure and being fixed in said first enclosure in said doser piston and outside said first enclosure to said rod and said piston of said jack, said cylinder of the first control jack being mounted on the first enclosure,
• a second control tube, and a second control jack having a second piston slidably mounted in said first control tube, said second control tube having a lower end and an upper end, said lower end penetrating tightly in said first enclosure, being fixed to said admission valve and being guided in said first control tube, said upper end being fast with said second piston of the second control jack, said second control jack being formed in said first control tube,
• a dispenser chamber, and an ejection valve having a flap and at least one ejection pipe, said dispensing chamber being connected to said outlet of the dosing chamber and to said at least one ejection pipe, said flap of the ejection valve being adapted to obturate said at least one ejection pipe and means for controlling said first jack, said second jack and said ejection valve such that when said doser piston moves during an ascending stroke, said ejection valve is closed and said admission valve is open to transfer the product from the upper chamber to the dosing chamber and when said doser piston moves during a descending stroke, said admission valve is closed and said ejection valve is open to transfer a determined quantity of product in the dosing chamber to the ejection pipe while simultaneously admitting another quantity of product into said upper chamber, said process comprising the following steps:
• providing a standard value for the weight of at least one recipient filled with the product, and providing a limit value;
• measuring the actual weight of at least every nth one of the recipients filled by the same doser-dispenser with a dosed quantity of the product, the number n being an integer between 1 and 1000,
• comparing said actual weight measured with said standard value, and
• adjusting said at least one end-of-stroke position of the doser piston to increase or decrease the stroke of said doser piston when the difference between the actual weight measured and the standard value exceeds said limit value and,
• effecting said adjusting, step by step, during operation of the doser-dispenser until said difference disappears.