DOSING PUMP Drawing Figure
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cted with the suction conduit by means of a conduit comprising a sump. It is in particular the advantage gained by the invention that by avoiding the evacuation the above-mentioned drawbacks are avoided and thus the piston-cylinder-means will have a substantially longer lifetime and hence the dosing pump in general will be less susceptible to maintenance. An embodiment of the invention is shown in the drawing and in the following described in greater detail. The FIGURE shows a schematic and partly sectional representation of a dosing pump connected with a water supply and having a container for dosing agent. The dosing pump 1 comprises a pump cylinder 2 having an inlet positioned above as seen in vertical direction and an outlet 3 positioned close to its lower end. Above the pump cylinder 2 there is provided a dosing piston 4 being reciprocated relative to the pump cylinder by means of a schematically represented piston drive means 5 and thus is inserted into the cylinder and withdrawn from the cylinder, resp. The piston drive means 5 is connected with a pulse generator 7 by means of a control line 6, the pulse generator providing control pulses to the piston drive means as a function of the fluid amount flowing through a conduit 8. At its upper side the pump cylinder 2 is connected with a predelivery chamber 9 constituted by a housing 10. The walls of the housing 10 may be formed as diaphragm clamps 12, 13 laterally gripping a diaphragm 11. The lower part of the housing 10 is hermetically connected with the wall of the pump cylinder. In a distance from the wall of the pump cylinder there is provided an inlet 40 connected with a tube-shaped suction conduit 41, which is connectable with a container 16 for dosing agent. The suction conduit comprises a suction valve 42 preventing backflow from the predelivery chamber 9 into the container 16. The inlet 40 is disposed on a level, as seen from the fluid level formed in the predelivery chamber, vertically above the inlet side of the pump cylinder 2. There is further provided a return conduit 43 being as well connectable with the container 16 and comprising a pressure valve 44. The return conduit 43 is connected with the predelivery chamber 9 at an outlet 45, whereby the outlet 45 is disposed, as seen in vertical direction and relative to the new fluid level formed in the predelivery chamber, above the inlet side of the pump cylinder 2 and preferably above the inlet 40. Preferably the containe