# US 4,396,529 A · Method and apparatus for producing a foam from a viscous liquid > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 4,396,529 A - Document ID: US4396529A - Status: Granted - Kind: A - Application number: 06/193,722 - Filed: 1980-10-03 - Granted: 1983-08-02 - Earliest claimed: 1978-11-13 - Assignees: Nordson Corporation - Inventors: Richard P. Price; Charles H. Scholl - Web page: https://patentgrep.com/patent/US4396529A ## CPC - B29B 7/7438: {Mixing guns, i.e. hand-held mixing units having dispensing means (B29B7/761, B29B7/7678 take precedence)} - B01F 23/235: for making foam - B27G 11/00: Applying adhesives or glue to surfaces of wood to be joined - Y10S 261/26: Foam - B29B: PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS - B01F: MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING (mixing paints B44D3/06) - B27G: ACCESSORY MACHINES OR APPARATUS FOR WORKING WOOD OR SIMILAR MATERIALS; TOOLS FOR WORKING WOOD OR SIMILAR MATERIALS (tools for grinding B24D; sawing tools B27B33/00; tools for slotting or mortising machines B27F5/02; tools for the manufacture of wood shavings, chips, powder or the like B27L11/00); SAFETY DEVICES FOR WOOD WORKING MACHINES OR TOOLS - Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS ## Abstract A method and apparatus for producing a coherent or extruded output stream of viscous liquid containing a dispersed gas to form a foam. The liquid is pressurized and delivered to apparatus having an internal chamber which presents a flow space for the flow of the liquid through it as an integral stream. A gas is introduced under pressure into the liquid, through an opening to the chamber across which the liquid sweeps, to form an unstable mixture of the gas in the liquid. The gas and liquid mixture is not further pressurized by pumping once the gas and liquid have been contacted, but the unstable mixture is maintained under pressure while it flows from the chamber to a restricted outlet orifice which can be closely adjacent to the chamber. At the outlet the pressure of the gas and liquid mixture is suddenly reduced by forcibly ejecting the mixture through the restricted orifice. A coherent stream of the gas/liquid mixture is produced wherein the gas substantially expands to form a foam. ## Claims ### Claim 1 A method of foaming a viscous liquid which comprises: separately pressurizing the liquid and a gas to at least several hundred pounds pressure and delivering them through separate passages to an applicator having an internal chamber which is connected to a restricted outlet orifice close to the chamber, introducing the gas into said liquid through minute passage means opening to said chamber, passing the liquid through said chamber as an integral stream which flows past the opening of said passage means to said chamber, so that the liquid stream segments the incoming gas to form a mixture of gas bubbles in the liquid, maintaining the gas and liquid mixture under pressure but without further increasing the pressure of the mixture while it flows from said chamber to said orifice, and suddenly reducing the pressure of the gas and liquid mixture by releasing it to atmosphere through said restricted orifice, the mixture being released as a stream which is coherent in passage to a substrate, whereby a foam will be produced one said substrate. ### Claim 2 (depends on 1) The method of claim 1 wherein the pressure under which the gas and liquid mixture is maintained while it flows from said chamber to said orifice is sufficiently high to prevent pre-expansion of said bubbles upstream of said outlet orifice. ### Claim 3 (depends on 1) The method of claim 1 wherein said mixture is discharged through a restricted orifice which is in the form of a tubular opening having a length to diameter ratio less than 1. ### Claim 4 (depends on 1) The method of claim 1 wherein said liquid passes through said chamber as an annular column. ### Claim 5 (depends on 1) The method of claim 1 wherein said gas is introduced to said chamber through passages having minute openings thereto, the gas flow being segmented by the flow of said liquid past said minute openings. ### Claim 6 (depends on 1) The method of claim 1 wherein said gas is introduced to said chamber in a direction at a right angle to the direction of flow of said liquid. ### Claim 7 (depends on 1) The method of claim 1 wherein said mixture is further mixed between said chamber and said orifice by passing it through paths which divide and recombine said mixture. ### Claim 8 (depends on 1) The method of claim 1 wherein said liquid is pressurized to a pressure of about 300 to about 700 psi. ### Claim 9 (depends on 1) The method of claim 1 wherein said gas is introduced to said chamber at a pressure about 100 psi greater than the pressure of said liquid. ### Claim 10 (depends on 1) The method of claim 1 wherein the volumetric gas flow rate, expressed at standard conditions, is in the range of about 1 to 50 times the volumetric flow rate of the liquid, but at actual conditions is only a fraction of the liquid flow rate. ### Claim 11 A method of producing a coherent output stream of liquid adhesive containing a dispersed gas which after discharge will expand to form a foam, comprising, pumping the liquid adhesive, under several hundred pounds pressure, as an integral stream into a chamber, separately introducing a gas into said chamber at a pressure greater than said adhesive, through passages having minute openings to said chamber that are swept by the stream of the pressurized adhesive, the flow of liquid across said openings segmenting the gas entering therefrom as microbubbles entrained in the stream, thereby forming an unstable gas/liquid mixture, conveying the mixture to a discharge orifice which is adjacent the chamber, without further pressure increase but while maintaining sufficient pressure on the mixing so formed to prevent pre-expansion of said gas during such conveying, and abruptly reducing the pressure by expelling the mixture to atmosphere through a restricted discharge orifice, the mixture exiting the discharge orifice as a stream in which said microbubbles then expand to form a foam. ### Claim 12 (depends on 11) The method of claim 11 wherein the gas is supplied to said chamber at a volumetric flow rate which, expressed at standard conditions, is in the range of about 1-50 times the volumetric flow rate of the adhesive but wherein the volumetric gas flow rate at actual conditions is only a fraction of the adhesive flow rate. ### Claim 13 (depends on 11) The method of claim 11 wherein said liquid adhesive is supplied at a pressure in the range of 300 to 700 psi. ### Claim 14 (depends on 11) The method of claim 11 wherein said gas is introduced to said chamber in a direction that is substantially at right angles to the direction of flow of the liquid adhesive through said chamber. ### Claim 15 (depends on 11) The method of claim 11 wherein the gas flow is restricted by passing the gas through an annular space defined by an axial wire in a capillary tube. ### Claim 16 (depends on 11) The method of claim 11 wherein said restricted orifice has a length to diameter ratio less than about 1. ### Claim 17 A method of foaming a viscous liquid which comprises: supplying a viscous liquid to a chamber of an applicator at a first pressure which is substantially above atmospheric pressure, causing said liquid to flow through the chamber as an integral stream, supplying a gas to said chamber at a second pressure which is above the first pressure, delivering the gas into the integral stream of the liquid, the movement of the liquid stream through the chamber segmenting said gas into microbubbles in the liquid, further dispersing said microbubbles in the liquid by providing static mixing in a tortuous flow path, delivering the dispersion of the microbubbles in the liquid from said chamber to a restricted outlet orifice which is close to and in communication with the chamber, said delivery to the orifice being effected without mechanically increasing the pressure of the dispersion, and releasing the dispersion to the outside of said applicator from said chamber through said restricted orifice as a stream which is coherent in passage to a substrate, whereby a foam will be produced on said substrate. ### Claim 18 Apparatus for foaming a viscous liquid which comprises means for pressurizing the liquid to several hundred pounds pressure and delivering it under pressure to an applicator having an internal chamber wherein it is mixed with gas, said chamber presenting an internal flow space for the flow of said liquid therethrough as a continuous stream, passage means for introducing the gas under pressure into said liquid in said chamber through minute transverse openings to said chamber past which the liquid flows as a continuous stream, to form an unstable mixture of the gas and the liquid, means for maintaining the gas and liquid mixture under pressure but without further pressure increase while it is conducted from said chamber to an orifice, and said orifice being a restricted outlet orifice close to the chamber for dispensing the gas and liquid mixture to atmosphere as a coherent stream. ### Claim 19 (depends on 18) The apparatus of claim 18 wherein said restricted orifice is in the form of a tubular opening having a length to diameter ratio less than 1. ### Claim 20 (depends on 18) The apparatus of claim 18 wherein said restricted orifice is in the form of a tubular opening having a length to diameter ratio in the range of about 0.1 to 0.9. ### Claim 21 (depends on 18) The apparatus of claim 18 wherein said chamber defines an annular flow space through which said liquid passes, said transverse openings entering to said annular flow space. ### Claim 22 (depends on 18) The apparatus of claim 18 wherein said passage means opens to said chamber in a direction at a right angle to the direction of flow of said liquid in said chamber. ### Claim 23 (depends on 18) The apparatus of claim 18 including mixing means presenting flow paths which divide and recombine said mixture downstream of said chamber, said mixing means disposed between said chamber and said orifice. ### Claim 24 Apparatus for foaming a viscous liquid which comprises means for pressurizing the liquid to several hundred pounds pressure and delivering it under pressure to an applicator having an internal chamber wherein it is mixed with gas, said chamber presenting an internal flow space for the flow of said liquid therethrough as a continuous stream, pressure means for introducing the gas under pressure into said liquid in said chamber through minute transverse openings to said chamber past which the liquid flows as a continuous stream, to form an unstable mixture of the gas and the liquid, means for maintaining the gas and liquid mixture under pressure but without further pressure increase while it is conducted from said chamber to an orifice, said orifice being a restricted outlet orifice close to the chamber, for dispensing the gas and liquid mixture to atmosphere as a coherent stream, and a flow restrictor which is adjacent said openings to said chamber, said restrictor comprising a capillary tube having an axial bore and a wire extending into said bore, an annular flow space being defined around said wire in said bore. ### Claim 25 A system for producing a coherent output stream of liquid adhesive containing a dispersed gas which will expand to form a foam bead, comprising a source of liquid adhesive under several hundred pounds pressure, a liquid conduit connected to said source, a contacting chamber communicating with said liquid conduit for flow of said liquid adhesive therethrough, a source of gas under pressure greater than the liquid pressure, a gas conduit connected to said gas source, said gas conduit including a gas flow restrictor, said flow restrictor positioned closely adjacent said chamber and communicating with it through minute gas injection openings across which the liquid adhesive stream flows, and passage means leading from said chamber directly to an adjacent discharge orifice, said discharge orifice being a short, restricted orifice having a length to diameter ratio which is less than 1. ### Claim 26 An attachment mountable to a hot melt adhesive dispenser to adapt it for producing a coherent output stream of hot melt adhesive containing a dispersed gas which will expand to form a foam, said dispenser being of the type including a body, a delivery passage through which said adhesive is delivered under high pressure, and a valve for controlling delivery of said adhesive through said delivery passage, said attachment comprising, a head mountable to said body for dispersing a gas in said adhesive in the head, a contacting chamber communicating with said delivery passage and through which said adhesive flows as an integral stream, a gas conduit for connection to a source of gas under pressure, said conduit including a gas flow restrictor, said flow restrictor positioned adjacent said chamber and communicating with it through minute laterally disposed gas injection openings across which the adhesive stream flows in a generally axial direction, and passage means leading from said chamber directly to a discharge orifice close to said chamber, said discharge orifice being a restricted orifice having a length to diameter ratio which is less than 1. ### Claim 27 (depends on 26) The attachment of claim 26 wherein said flow restrictor is effective to restrict the flow of said gas under pressure to a volumetric rate which, expressed at standard conditions, is in the range of about 1 to 50 times the volumetric rate of flow of the adhesive. ### Claim 28 (depends on 26) The attachment of claim 26 wherein said chamber defines an annular flow space through which said adhesive passes. ### Claim 29 (depends on 26) The attachment of claim 26 wherein said minute openings direct said gas into said chamber in a direction at right angles to the direction of flow of said adhesive in said chamber. ### Claim 30 An attachment mountable to a hot melt adhesive dispenser to adapt it for producing a coherent output stream of hot melt adhesive containing a dispersed gas which will expand to form a foam, said dispenser being of the type including a body, a delivery passage through which said adhesive is delivered under high pressure, and a valve for controlling delivery of said adhesive through said delivery passage, said attachment comprising, a head mountable to said body for dispersing a gas in said adhesive in the head, a contacting chamber communicating with said delivery passage and through which said adhesive flows as an integral stream, a gas conduit for connection to a source of gas under pressure, said conduit including a gas flow restrictor, said flow restrictor positioned adjacent said chamber and communicating with it through minute laterally disposed gas injection openings across which the adhesive stream flows in a generally axial direction, said flow restrictor comprising a capillary tube having an axial bore and a wire extending into said bore, an annular flow space being defined around said wire in said bore, and passage means leading from said chamber directly to a discharge orifice close to said chamber, said discharge orifice being a restricted orifice having a length to diameter ratio which is less than 1.