Locking mechanism; mounting pyrometers

摘要

A pyrometer 1 has a lock nut 31 that engages a threaded sighting tube 5. The lock nut 31 encloses a ratchet mechanism formed by two coaxial collars 36 and 37 with inclined ratchet teeth (38 and 39) Fig 3 (not shown) at their ends. The teeth (38 and 39) are urged together by a helical spring 40, one of the collars 36 being prevented from rotation relative to the nut 31 by means of a pin 49 that engages a slot 48 in the collar. The other collar 37 has an annular face 54 which is urged by a disc spring 43 against a washer 51 locked with the body 18 of the pyrometer so as to form a friction clutch. The ratchet allows the nut to be tightened but it can only be untightened by overcoming the friction of the clutch.