the seal at 49 and permitting equalizing pressure across the closure disc 44 in the manner described above axial displacement of the mounting pin 42 also assures clearance between the rotor 24 and the body 16 during rotation of the rotor 24 rotation of the assembly 69 at the top of the mounting pin 42 accomplishes an unlocking function the numeral 70 identifies a locking lug which protrudes radially inwardly from the surrounding lower body component 12 the rotor 24 supports a collar 71 which extends partially around the lower end thereof the collar 71 has a top face or surface 72 when the rotor 24 is forced downwardly the top surface 72 is located below the lug 70 whereby relative rotation is permitted the collar 71 is slotted at 74 thereby permitting the lug 70 to move relatively upwardly and downwardly in the slot 74 to assure proper alignment of the curved conduits 26 and 30 as shown in fig3 a pair of stop lugs 76 are located on the rotor 24 the stop lugs 76 extend above the surface 72 of the collar 71 providing an abutment surface for limiting rotational movement of the rotor 24 a stop lug is located adjacent each end of the collar 71 and spaced therefrom defining a slot 78 thereby permitting the lug 70 to.