holes 34 and 36 in that plate as seen in fig3 4a a weld forms the joinder between the plate and the two conduits the other solid plate 38 has circular holes located at 40 and 42 and aligned generally with the holes 34 and 36 in the first plate 32 the conduits 24 and 26 welded to the plate 38 surround the holes 40 and 42 respectively as shown most clearly in fig4 a the bolts and nuts 44 and 46 serve to hold the two plates 32 and 38 together while the spacers 45 maintain the space between them located between the two metal plates 32 and 38 the plastic disk 48 acts as the closing member of the valve the pin 50 serves to locate the plastic disk 48 centrally between the two plates 32 and 38 while at the same time permitting rotation of the disk 48 about that pin the pin 50 of course passes through openings 52 and 54 in the plates 32 and 38 respectively and the hole 56 through the plastic disk 48 the disk 48 also has an opening 58 into which is inserted a cross pin of piston 60 and bushing 62 the latter of which may also be a ball bearing the piston 60 moves parallel to the web 48 and carries the cross pin shown in bushing 62 which passes into an opening 64 in the plate 32 the piston 60 attaches to the actuating mechanism 65 located adjacent to the plate 38 the actuating mechanism 65 serves to move the piston back and forth in the direction indicated.