Filter cartridges and filter cells

A filter cartridge including a plurality of filter cells, arranged in a contiguous and stacked relationship,

• each filter cell including an inner separator disc having a central aperture surrounding a central axis and a plurality of upstanding members extending axially outwardly from opposite sides of each said disc and being arranged about said central aperture,
• filter medium for covering opposite sides of each said disc,
• spacer means for spacing adjacent filter cells from each other,
• means for holding said plurality of filter cells in position to form said cartridge,
• wherein,
• said plurality of upstanding members comprising pins or teeth,
• said spacer means comprising spacer rings surrounding said central axis, each said spacer ring having a circumferential land, wherein a radially outer periphery of each said land is bounded by a circumferential wall, each said land being engaged by the pins or teeth of adjacent filter cells, wherein said pins and teeth are arranged in an interlocking position with the respective said circumferential wall to prevent movement of any of said filter cells in a radial direction of said central aperture.