Patent ID: 7066338

Claim:
A filter element comprising: a rigid injection moulded generally cylindrical canister formed about a male mould member, the canister having an internal diameter, an open end and a side wall, the side wall having an outer surface and an inner surface; and a paper roll as filter media, wherein at least five spaced anti-tracking ribs project from the inner surface of the side wall a distance sufficient to enable the canister to be removed from the male mould member during a moulding process and while still sufficiently flexible, at least five of said ribs being unevenly spaced such that there is a unique distance between every two immediately adjacent ribs, the paper roll has a marginally greater diameter than the internal diameter of the canister prior to insertion into the canister, and the canister is sufficiently rigid and the paper roll is sufficiently tightly wound that the paper roll, when inserted into the canister using a press, is substantially compressed to the internal diameter of the canister without distortion of the canister.