Treating airborne web material

Claim 3

An installation for treating airborne web material passing through the installation, comprising blow boxes for supplying air at an elevated pressure relative to the pressure on the upper surface of the web, said blow boxes including: pairs of spaced apertures arranged in upper surfaces of the blow boxes along the conveying path of the material for supplying primary air to said web, said apertures being designed to eject the primary air in pairs of streams facing away from each other and along the conveying path of the web, whereby in the space between said apertures a static underpressure in relation to the pressure on the upper surface of the material tends to arise and to cause deflection and; passages or pipes mounted in each blow-box and extending transversely therethrough and open at one end toward said conveying path between said ejection apertures for the primary air for sucking in a great volume of secondary air having substantially the same static pressure as that prevailing on the upper surface of the material, whereby said secondary air is taken along by ejector effect by the primary air streams ejected from said apertures, the area of said opening at said one end being substantially greater than the areas of the ejector apertures to afford variation in the volume of secondary airflow without substantially affecting its static pressure.

Claim 4

An installation for treating airborne web material passing through the installation, comprising blow boxes for supplying air at an elevated pressure relative to the pressure on the upper surface of the web, said blow boxes including: pairs of spaced apertures arranged in upper surfaces of the blow boxes along the conveying path of the material for supplying primary air to said web, said apertures being designed to eject the primary air in pairs of streams facing away from each other and along the conveying path of the web, whereby in the space between said apertures a static underpressure in relation to the pressure on the upper surface of the material tends to arise and to cause deflection and; passages or pipes mounted in each blow-box and extending transversely therethrough and open at one end toward said conveying path between said ejection apertures for the primary air for sucking in a great volume of secondary air having substantially the same static pressure as that prevailing on the upper surface of the material, whereby said secondary air is taken along by ejector effect by the primary air streams ejected from said apertures, the area of said opening at said one end being substantially greater than the areas of the ejector apertures to afford variation in the volume of secondary airflow without substantially affecting its static pressure.

Claim 5

A device according to claim 2, including special ejector apertures in said passages or pipes having angular openings to eject primary air at elevated pressure from the blow-box into said passages or pipes upstream of said one end in the flow direction of the secondary air, thereby compensating for the pressure drop in the passages or pipes and maintaining said same static pressure at said one end.

Claim 6

A device according to claim 2 characterized in that passages or pipes communicate with a zero pressure space in a part of the blow-box which is separated from the ambient and has substantially the same pressure as on the upper surface of the material, and means to supply said space with air by returning a part of the primary air from between the material and the blow-box.

Claim 7

A device according to claim 4, characterized in that said means for returning air is disposed on both sides of the blow-box.

Claim 8

A device according to claim 4, characterized in that said means for returning air is disposed on only one side of the blow-box.

Claim 9

In an installation for treating airborne web material passing through the installation, having blow boxes where the air is supplied through pairs of primary apertures arranged in upwardly-facing surfaces along the conveying path of the material, which apertures are designated to eject the air in pairs of streams facing away from each other, whereby in the space between said primary apertures a static underpressure in relation to the pressure on the upper surface of the material tends to arise and to cause deflection, characterized in that passages or pipes for sucking in a great volume of secondary air having substantially the same static pressure as that prevailing on the upper surface of the material, are mounted in each blow-box and extend transversely therethrough and open at one end toward said conveying path between said ejection apertures for the primary air and open at the opposite end directly with ambient air to suck in atmospheric air, whereby said secondary ambient air is taken along by ejector effect by the primary air streams ejected from said apertures, said blow-box including special secondary ejector apertures opening into said passages or pipes between said one end and said opposite end to eject air from the blow-box into said passages or pipes in the flow direction of the secondary ambient air, thereby compensating for the pressure drop in the passages or pipes and maintaining said same static pressure at said one end.

Claim 10

In an installation for treating airborne web material passing through the installation, having blow boxes where the air is supplied through pairs of primary apertures arranged in upwardly-facing surfaces along the conveying path of the material, which apertures are designated to eject the air in pairs of streams facing away from each other, whereby in the space between said primary apertures a static underpressure in relation to the pressure on the upper surface of the material tends to arise and to cause deflection, characterized in that passages or pipes for sucking in a great volume of secondary air having substantially the same static pressure as that prevailing on the upper surface of the material, are mounted in each blow-box and extend transversely therethrough and open at one end toward said conveying path between said ejection apertures for the primary air and open at the opposite end directly with ambient air to suck in atmospheric air, whereby said secondary ambient air is taken along by ejector effect by the primary air streams ejected from said apertures, said blow-box including special secondary ejector apertures opening into said passages or pipes between said one end and said opposite end to eject air from the blow-box into said passages or pipes in the flow direction of the secondary ambient air, thereby compensating for the pressure drop in the passages or pipes and maintaining said same static pressure at said one end.