Hepa filter unit having a metallic membrane

Claim 1

A filter unit of the Hepa type adapted to filter out of a gas passing therethrough minute particles carried by the gas, said unit comprising: (a) a media pack, free of contaminant-producing bonding and sealing agents, having a membrane created by a continuous metal sheet accordion-folded to define a series of pleats having an entry face and an exit face, said sheet being fabricated of sintered metal constituted by metal powders whose interstices form pores dispersed throughout the sheet, the sizes of the pores being such as to block said minute particles, the dimensions of the sheet being such as to provide a multitude of pores resulting in a relatively low pressure drop in a gas passing through said membrane; and (b) means to interpose said media pack between a source of pressurized gas carrying said particles and a work processing region whereby the pressurized gas is applied to the entry face of the pack and is filtered therethrough to yield at the exit face a laminar flow of gas providing an environment for said region which is free of particles and contaminants.