Clean air zone

Claim 2

Apparatus for generating a clean air zone comprising: a rectangular housing having a plenum chamber and a lower face and perimetral lateral side walling including a plurality of side faces each having an air inlet therethrough, a filter below the inlets within the housing between the plenum chamber and lower face, a fan in each corner of the housing for drawing air from the surrounding area and through the inlets and into the plenum chamber, the lower face including a diffuser constituting an air delivery means having areas of different permeabilities for supplying air to the space therebeneath, the areas of different permeabilities being determined by differing numbers of apertures and/or differing sizes of apertures in the different areas, all adapted and arranged with air discharged through the air delivery means passing firstly through the areas of different permeabilities and downwardly into the corresponding spaces therebelow and secondly laterally outwardly and thirdly upwardly toward the inlets for sweeping a volume greater than the volume of the said spaces in the generation of a clean air zone having a perimeter outside the perimeter of the lower face.

Claim 3

Apparatus for generating a clean air zone comprising: a housing having a lower one face and perimetral lateral side walling, an air delivery means having an air outlet in the one face for supplying air to the space beneath the one face, and air inlets distributed about the perimetral lateral side walling so that air from the outlet passes firstly downwardly into the space directly below the one face and secondly laterally outwardly of the space and thirdly back and upwardly towards the inlets so as to sweep a volume greater than the volume of the space directly beneath the one face to generate a clean air zone whose perimeter lies outside the perimeter of the one face, with the lateral side walling of the housing including a plurality of faces, each face having at least one of the inlets, the housing being rectangular and a fan being provided at each corner thereof, each fan having an extended inlet in the respective side wall of the housing on either side thereof; each fan discharging air into a plenum chamber within the housing above a filter which lies above the air delivery means; the delivery means being in the form of a diffuser, the different permeabilities being achieved by the provision of areas having different numbers of apertures.

Claim 4

Apparatus for generating a clean air zone comprising: a housing having a lower one face and perimetral lateral side walling, an air delivery means having an air outlet in the one face for supplying air to the space beneath the one face, and air inlets distributed about the perimetral lateral side walling so that air from the outlet passes firstly downwardly into the space directly below the one face and secondly laterally outwardly of the space and thirdly back and upwardly towards the inlets so as to sweep a volume greater than the volume of the space directly beneath the one face to generate a clean air zone whose perimeter lies outside the perimeter of the one face, with the lateral side walling of the housing including a plurality of faces, each face having at least one of the inlets, the housing being rectangular and a fan being provided at each corner thereof, each fan having an extended inlet in the respective side wall of the housing on either side thereof; each fan discharging air into a plenum chamber within the housing above a filter which lies above the air delivery means; the delivery means being in the form of a diffuser, the different permeabilities being achieved by the provision of areas having different numbers of apertures.