Patent ID: 8313313

Claim:
A pumping device ( 1 ) by means of which fluids ( 10 ) or pourable materials stored in a reservoir tank ( 9 ) can be transported to a spray gun ( 11 ) in a metered fashion, the device comprising: a piston rod ( 5 ) mounted in an axially moveable arrangement in a housing ( 2 ), a reciprocating piston ( 25 ) mounted on an end of the housing, a piston ( 7 , 8 ) connected to said piston rod ( 5 ) and moveable between first and second housing sections ( 3 , 4 ), by means of which first and second pressure chambers ( 21 , 21 ′, 22 , 22 ′) are enclosed by means of said piston ( 7 , 8 ) together with the first and second housing sections ( 3 , 4 ), pressure lines ( 17 , 17 ′) disposed in each of the two housing sections ( 3 , 4 ) such that the pressure lines debouch in one of the pressure chambers ( 21 , 21 ′ or 22 , 22 ′), a working medium ( 19 ), by means of which said piston ( 7 , 8 ) can be driven and pressed into the corresponding pressure chamber ( 21 , 21 ′, 22 , 22 ′) alternately through said pressure lines ( 17 , 17 ′) by a changeover valve ( 18 ), a diaphragm ( 12 , 13 ) having a central area ( 14 ) connected to said piston rod ( 5 ) and an outer area ( 15 ) connected to the housing ( 2 ), and a flexible ring area ( 16 ) disposed between said central and outer areas ( 14 , 15 ), and provided as a compensation and sealing element, and a pumping chamber ( 20 ) enclosed by said diaphragm ( 12 , 13 ) and the housing ( 2 ), into which the fluid ( 10 ) or pourable material is alternately drawn or from which the fluid ( 10 ) or pourable material is pressed in the direction of the spray gun by the axial movement of said reciprocating piston ( 25 ), wherein the second housing section and said diaphragm ( 12 , 13 ) form a control chamber ( 31 ) in which a negative pressure prevails, and wherein a negative pressure condition of the control chamber ( 31 ) can be monitored from the outside, wherein a control line ( 32 ) debouches in the control chamber ( 31 ), wherein a line is connected to a measuring device ( 33 ) and communicates therewith such that the measuring device ( 33 ) allows the negative pressure condition in the control chamber ( 31 ) to be measured, and the control chamber ( 31 ) is temporarily or permanently connected with a suction device ( 37 ) by means of the control line ( 32 ), and the suction device ( 37 ) allows the control chamber ( 31 ) to be evacuated, and said flexible ring area ( 16 ) of said diaphragm ( 12 , 13 ) is drawn into the control chamber ( 31 ) due to the negative pressure prevailing in the control chamber ( 31 ) and has a curvature ( 38 ) projecting in the direction of the control chamber ( 31 ).