DOSING PUMP Drawing Figure
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ABSTRACT A dosing pump (1) is created allowing to accurately dose a medium to be dosed as a function of time or of a flow rate. The dosing pump (1) utilizes a predelivery obtained by a diaphragm (11) as well as a piston-cylinder-pump for dosing. The pump cylinder is connected with the suction conduit so as to prevent any pressure drop when the piston emerges from the cylinder. A crystallization or polymerization of the dosing agent in the piston-cylinder-means is thereby prevented. DESCRIPTION The invention refers to a dosing pump comprising a pump cylinder connected at its inlet side with a predelivery chamber and at its outlet side with a dosing point and a dosing piston cooperating therewith as well as a diaphragm, whereby the predelivery chamber is positioned above the pump cylinder and is connectable with a container for dosing agent via a suction conduit comprising a suction valve and a return conduit comprising a pressure valve. In a known dosing pump with dosing piston-cylinder-means and predelivery diaphragm the predelivery chamber is connected with a container for dosing agent via a suction conduit comprising a suction valve and a return conduit comprising a pressure valve. The predelivery is performed via the suction conduit and the suction valve to the predelivery chamber. The dosing piston takes the required amount of dosing agent from the predelivery chamber. The excess amount of dosing agent is transported back into the container for dosing agent via the pressure valve and the return conduit. In a known dosing pump the pump cylinder is connectable with a dosing point via a pressure valve. When the piston is withdrawn from the cylinder a vacuum is drawn which causes volatilization of the dosing agent. In using certain dosing agents such as silicates, hydrates of soda or the like this leads to a crystallizing-out within the pump cylinder and thus to a destruction of the dosing pump. In using other dosing agents such an evacuation leads to a polymerisation and thus also to a destruction of the piston-cylinder-means. It is the object of the invention to create a dosing pump of the kind described at the outset where the above discussed drawbacks are avoided. In particular the expansion within the pump cylinder during the emersion of the piston shall be avoided. This object is achieved with a dosing pump according to the generic part by a connection of the pump cylinder with the suction conduit. Preferably the pump cylinder is conne