Patent ID: 6871996

Claim:
A mixing device ( 1 ) for mixing pulverulent and liquid substances with each other for the manufacture of medical products, the mixing device defining a first space ( 18 ) and a second space ( 20 ), wherein the pulverulent substance ( 19 ) is provided in the first space ( 18 ) on one side of a displaceably mounted piston ( 17 ) and the liquid substance ( 21 ) in is provided in the second space ( 20 ) on the opposite side of the piston ( 17 ), wherein the piston ( 17 ) is displaceable by a displacement means ( 6 ), wherein the piston ( 17 ) has at least one groove ( 22 ) extending around the piston ( 17 ), at least one sealing ring ( 23 ) being located in the groove ( 22 ), wherein the sealing ring ( 23 ) is provided to cooperate, in a sealing position (A), with the piston ( 17 ) and with a wall ( 1 a ) of the mixing device ( 1 ), the wall ( 1 a ) surrounding the piston ( 17 ), whereby the piston ( 17 ) and sealing ring ( 23 ) sealingly separate the first and second spaces ( 18 , 20 ) from each other for preventing the pulverulent substance ( 19 ) and the liquid substance ( 21 ) from mixing with each other when mixing should not occur, and wherein the sealing ring ( 23 ) is provided, when loaded by the liquid substance ( 21 ) during displacement of the piston ( 17 ) in a direction (B) towards the second space ( 20 ) containing the liquid, to be pressed inwards in a direction (C) in the groove ( 22 ) by the liquid substance ( 21 ) and thereby at least partially being brought to leave the sealing position (A) such that the liquid substance ( 21 ) may flow into the first space ( 18 ) containing the pulverulent substance ( 19 ) for mixing therewith, characterized in that at least one connecting passage ( 22 e ) is provided to permit flow of the liquid substance ( 21 ) out of an inner space ( 22 d ) in the groove ( 22 ) behind the sealing ring ( 23 ), for preventing the liquid substance ( 21 ) from generating such a pressure in the inner space ( 22 d ) that the pressure presses the sealing ring ( 23 ) in a direction (F) outwards relative to the groove ( 22 ) towards the surrounding wall ( 1 a ) and prevents flow of the liquid substance ( 21 ) in a direction (E) from the second space ( 20 ) to the first space ( 18 ) when the piston ( 17 ) is displaced by the displacement means ( 6 ) in direction (B) towards the second space ( 20 ), the sealing ring ( 23 ) leaving the sealing position (A) against the wall ( 1 a ) so that the liquid substance ( 21 ) may flow between the sealing ring ( 23 ) and the wall ( 1 a ) into the first space ( 18 ) containing the pulverulent substance ( 19 ) for mixing therewith.