Tamperproof rotary valve

A tamperproof rotary valve comprising:

• a valve body having a fluid flow passage extending therethrough, the passage being intersected by an actuator opening in the body and defining a valve chamber thereat;
• a rotary valve disposed in the chamber for opening and closing the fluid flow passage in the valve body;
• an actuator journaled in the actuator opening and coupled to the rotary valve for rotating the valve, the actuator having a top and bottom and being assembled by moving the actuator into the actuator opening in an insertion direction until the actuator is in a seated position, the actuator having a lengthwise axis and an outer surface with a first diameter;
• and
• tamperproof means between the actuator and the valve body for inhibiting removal of the actuator, said tamperproof means including a groove circumscribing the outer surface of the actuator, a chamfered surface portion on a lower edge of the groove, a contractible/expanding locking ring in the groove and projecting partially outwardly of the groove beyond the bounds of the outer surface of the actuator and resting on said chamfered surface when in a free unbiased condition, a locking groove in the actuator opening in the valve body and into which the locking ring expands when biased by the chamfered surface portion due to a force exerted on the actuator opposite to the insertion direction, a cam surface means located in the actuator opening on a lead-in side of the locking groove for engaging and contracting the locking ring automatically in response to inserting the actuator in the actuator opening during assembly, said cam surface means having a second diameter substantially equal to the first diameter, the locking ring being contractible fully into the groove by the cam surface means to allow clearance for the locking ring over the locking groove only during assembly of the actuator, said actuator surface and said cam surface means of said first and second diameters, respectively, being disposed outwardly of said groove to prevent tampering with said locking ring from externally of the valve, whereby when the actuator is inserted into the seated position, the locking ring returns to the unbiased condition on the chamfered surface wherein the partially outwardly projecting locking ring engages the locking groove such that with force exerted on the actuator opposite the insertion direction, the chamfered surface expands the locking ring outwardly against the locking groove thereby positively blocking further axial movement of the actuator.