Abstract: A filter apparatus having an apparatus for clamping a cylindrical air filter element in place against a fixed surface within a filter housing. The apparatus includes a clamping plate arranged to be moved between a first position in which the clamping plate presses the filter element against the fixed surface, and a second position in which the filter element is released from contacting either the plate or the fixed surface. To move the clamping plate into each position an arrangement of rotatable cam rods, support fins and bearing saddles are provided. Both the clamping plate and the fixed surface are substantially planar and oriented in the support structure so that when the filter is not clamped therebetween it can be removed from the support structure in a direction perpendicular to its main axis.