Casing

A two-part housing, especially for an air filter, has a twist-locking system with two groups of locking devices, one for sustaining the joint between the two parts and the other for adjusting the opening and closing torque. In a two-part housing, especially a filter housing, preferably an air filter housing, the two parts have corresponding locking devices which enable them to be joined together and separated by rotating one relative to the other. In this system, a first group of locking devices have means of sustaining the bond between the parts and a second group has means of adjusting the torque for opening and closing the housing. Independent claims are also included for the following (1) a first housing part (P1) as above with, in the region of the coupling point to the second part (P2), two similar locking devices arranged so as to engage with corresponding locks on the second part; and (2) a second housing part (P2) with two different locking devices, one of which (L1) locks the joint by engaging with the first device on P1 while the other (L2) (in combination with the first device on P1) undertakes torque-adjustment functions for opening and closing the housing. .