Pump device

A double-acting pump device comprising:

• a piston arrangement being slidably arranged in a pump housing, the pump housing being separated into a drive section with a drive fluid inlet and a drive fluid outlet and a pump section with an inlet and an outlet for a pump fluid, and wherein the drive section comprises a switch mechanism which utilizes the difference between the drive fluid supply pressure and the drive fluid outlet pressure to reciprocate the piston arrangement, such that axially acting forces are transferred to the pump fluid which thereby achieves a desired pressure increase,
• wherein the piston arrangement comprises a drive piston being displaceable in a cylindrical guide in the drive section and having a piston rod being slidably arranged through a partition wall in a fluid-tight manner between the drive section and the pump section, such that the drive section is separated into two drive chambers (IV,V) having different cross-sections, and wherein the drive chamber (IV) with the smallest cross-section is permanently open towards the drive fluid inlet,
• wherein the switch mechanism comprises a switch valve and an initiating valve cooperating with the drive piston via an actuating lever which is subjected to an alternating pull and push each time the drive piston approaches an end point, whereby the initiating valve switches between pressurizing and exhausting a chamber in the switch valve and thereby provide a switch between a first operating condition, wherein the drive chamber (V) having the largest cross-section has an open connection with the inlet and is closed from the outlet, and a second operating condition, wherein the drive chamber (V) is closed off from the inlet and has an open connection with the outlet,
• the piston arrangement further comprises a displaceable first element being connected to the piston rod on the inside of the pump section and displaceable in relation to a rigidly mounted second element, and the first element cooperates with to sliding seals) such that a first (I), a second (II) and a third chamber in the pump section are separated by fluid-tight barriers, wherein
• the first chamber (I)) is connected with the pump fluid inlet via at least one directional valve, the directional valve being closed when the first chamber is compressed and opens for supply of liquid from the pump fluid inlet when the first chamber (I) is expanded,
• the second chamber (II) has a smaller cross-section than the first chamber and is compressed and expanded in counter-phase with the first chamber (I),
• the second chamber (II) is connected to the first chamber (I) via at least one directional valve which opens when the first chamber (I) is compressed, whereby a part of the liquid provided from chamber (I) is taken up into the second chamber (II) and the remaining part of the liquid is let out via a pump fluid outlet, and which closes when the first chamber (I) is expanded whereby the liquid in the second chamber (II) is let out via the pump fluid outlet,
• the third chamber (III) is a pressure compensation chamber having an open connection with the drive fluid outlet or with the pump fluid inlet depending on the function which the pump device is configured for.