Patent ID: 8177874

Claim:
A filter assembly for removing material entrained in a fluid stream, comprising: a filter element for removing material entrained in the fluid stream; a housing having a head part and a body part in which the filter element can be removably received, and inlet and outlet ports for the fluid that is to be filtered, the head part and the body part in which the filter element can be received each having locking formations which enable the head and body parts to be connected to one another and separated by relative rotation about an axis which is coaxial with a head axis and a body axis; keying formations associated with each of the head and body parts, in the form of at least one recess and at least one projection, in which the body part keying formations are provided on the filter element when it is positioned in the body part, arranged so that, (i) when the head part and the body part, with the filter element positioned in the body part, are initially offered to one another to assemble the housing, the keying formations on the head part and the filter element engage one another with the projection located within the recess, thereby restricting relative rotation between the head part and the body part, (ii) continued movement of the head part and the body part towards assembly of the housing causes the projection to be moved out of the recess so that the keying formations are disengaged, allowing relative rotation of the head and body parts without restriction by either the keying formations or the locking formations, and (iii) the said relative rotation of the head and body parts after the keying formations have become disengaged allows the locking formations to be aligned and to engage one another so that the head and body parts can be rotated to become sealingly connected to one another, the angle through which the said free relative rotation prior to engagement of the locking formations is possible being greater than the angle through which relative rotation is possible when the keying formations are engaged with one another.