Switchover valve

A valve for switching over from one supply of pressure fluid to another supply thereof in response to failing or failure of the one supply, said valve comprising:

• a valve body;
• a first cylinder in the body extending endwise thereof;
• two inlets in the body for connection thereto of the respective supplies, one communicating with one end and the other with the other end of said first cylinder;
• an outlet in the body extending radially outward from the first cylinder generally at the center of length of the first cylinder;
• a second cylinder in the body extending outward from said first cylinder intermediate its said ends and open to said outlet for exposure to the pressure of fluid in the outlet;
• a piston constituting a switchover valve member slidable in the first cylinder between a position establishing communication for delivery of fluid from one inlet to the outlet and blocking flow from the other inlet to the outlet and a position establishing communication for delivery of fluid from the other inlet to the outlet and blocking flow from the one inlet to the outlet;
• said piston being subject to pressure of fluid supplied to said one inlet for moving it from the first-mentioned position to the second-mentioned position and to pressure of fluid supplied to the other inlet for moving it from the second-mentioned position to the first-mentioned position;
• a latch piston slidable in said second cylinder having a latch thereon for latching the valve member in one or the other of said positions, said latch being movable between a latching position engaging the valve member and a retracted position clearing the valve member for movement;
• said latch being biased toward said retracted position and being held in latching position against the bias by pressure of fluid delivered by the valve member in one or the other of its said positions, said latch moving to said retracted position under the bias upon a drop in pressure of fluid delivered by the valve member in either of its said positions;
• and
• said switchover piston and said latch piston having a cooperating recess and detent arrangement for holding the switchover piston in one or the other of its two positions.