Temperature control system and pushbutton controlled pneumatic actuator

A pushbutton actuated pneumatically operated actuator, said actuator comprising:

• (a) body means, said body means defining
• (i) a fluid chamber, and
• (ii) a plurality of spaced fluid outlet ports extending through a wall of said body means and in fluid communication with said chamber, with each of said ports connected to an associated outlet fluid passageway, said passageways being adapted for connection to a fluid pressure sink, said plurality of fluid ports including at least one intermediate fluid port and two outermost fluid ports on either side of said intermediate fluid port;
• (b) piston means slidably received in said chamber, said piston means including seal means located around the periphery thereof and in generally sealing engagement with said outlet fluid passageways;
• (c) inlet means for communicating fluid pressure into said chamber on opposite sides of said piston seal means;
• (d) valve means disposed in each of at least three of said passageways, said valve means each having a valve member adapted for selective actuation and movable between a normally closed position in which said passageway is isolated from said fluid outlet port and an open position in which said passageway communicates with said fluid outlet port, said valve means in said open position permitting fluid in said passageway to escape therefrom at a flow rate substantially greater than said inlet port means permits fluid to enter said passageway, said piston means movable upon actuation of one of said valve means to a position in which said seal means straddles said outlet port and substantially prevents further fluid flow to said outlet passageway;
• (e) said inlet means is defined by a vent passage in each of said valve members, said valve means in fluid communication with said outermost fluid ports, said vent passage closed upon said valve means being actuated to said open position;
• and
• (f) check valve means disposed intermediate said valve means and said at least one intermediate fluid port, said check valve means preventing atmospheric air from venting into said passageway through said intermediate fluid port.