Double seat valve

Abstract

A double seat valve comprises a housing having a fluid inlet, a fluid outlet and two axially displaced valve seats between the inlet and the outlet. A pair of valve discs are moveable independent from each other between open and closed positions with respect to the valve seats, one of the valve discs engaging during its opening movements the other of the valve discs and forming in the closed position with the other valve disc a chamber from which a leak fluid passage leads to the surrounding air. A tubular displacement rod is connected at one end to the one valve disc and extends with a radially enlarged end portion into a cylinder of a main displacement mechanism which is axially displaced from the housing. The radially enlarged portion forms at the junction with the remainder of the tubular rod a shoulder and a piston is connected axially displaced from the shoulder to the enlarged portion. A first coil compression spring cooperates with the piston and the tubular connecting rod for biasing the one valve disc to the closed position. A second displacement rod connected to the other valve disc extends through the tubular connecting rod and through an opening in the piston beyond the latter. A second coil spring located in the enlarged portion engages with one end the shoulder and with the other end a ring coaxially fixed to the second displacement rod. Stroke assuring means are provided which may be constituted by the second compression spring when compressed to a block or by a second shoulder in the enlarged portion and engageable with the peripheral portion of the ring.