Centrifugal filter unit for a washing machine having a removable portion shaped to scrape against a side wall during its removal

1. A centrifugal filter unit for an apparatus, wherein the apparatus is for use in the treatment of a substrate with a treatment formulation, the centrifugal filter unit comprising;

a) a housing having an outlet that allows a filtrate to exit the centrifugal filter unit;

b) an inlet that allows a feed comprising a liquid and solid material to enter the centrifugal filter unit;

c) a filter rotatably mounted in the housing, wherein the filter comprises a first end proximate a first end of the housing, a second end proximate a second end of the housing and a side wall connecting the first end of the filter and the second end of the filter, wherein the first end, second end and side wall of the filter define a filter chamber, and wherein the side wall comprises perforations that allow the liquid to pass through but to prevent the solid material from passing through;

d) an aperture in the filter that cooperates with the inlet to allow the feed to enter the filter chamber; and

e) a drive means for rotating the filter; wherein a portion of the centrifugal filter unit in the filter chamber is removable, and, which when removed from the centrifugal filter unit following operation takes with it at least a portion of the solid material prevented from passing through the perforations;

wherein the centrifugal filter unit is arranged such that the feed is drawn into the filter chamber from the inlet through the aperture and the liquid is expelled through the perforations to the outlet and the solid material is retained in the filter chamber, and

wherein the removable portion is shaped to scrape against the side wall during removal of the removable portion from the filter chamber.

2. The centrifugal filter unit according to claim 1 , further comprising a lid, wherein the lid is openable.

3. The centrifugal filter unit according to claim 1 , further comprising a cap at the first end of the filter, wherein the cap comprises the aperture.

4. The centrifugal filter unit according to claim 3 , wherein the removable portion comprises the cap.

5. The centrifugal filter unit according to claim 4 , further comprising an impeller disposed in the filter chamber, wherein the removable portion comprises the impeller and the cap.

6. The centrifugal filter unit according to claim 1 , wherein the removable portion rotates with the filter.

7. The centrifugal filter unit according to claim 1 , wherein the removable portion comprises a plunger.

8. The centrifugal filter unit according to claim 1 , wherein the removable portion has substantially the same shape as a cross-section of the filter chamber taken through the side wall of the filter.

9. The centrifugal filter unit according to claim 1 , wherein at least a portion of the removable portion has substantially the same shape as a cross-section of the filter chamber taken through the side wall of the filter.

10. The centrifugal filter unit according to claim 1 , wherein the removable portion comprises a plurality of bristles, wherein the bristles are arranged on the removable portion proximate the side wall of the filter.

11. The centrifugal filter unit according to claim 1 , further comprising an impeller disposed in the filter chamber.

12. The centrifugal filter unit according to claim 11 , wherein the impeller is coupled to the filter such that the impeller rotates at the same speed as the filter.

13. The centrifugal filter unit according to claim 11 , wherein the removable portion comprises the impeller.

14. The centrifugal filter unit according to claim 1 , wherein the removable portion is detachable from the filter by a twist-lock mechanism.

15. The centrifugal filter unit according to claim 1 , wherein the perforations in the filter have an average largest dimension of no more than 70 μm.