High pressure mixing head for continuously producing polymeric foam

A method for continuously producing polymeric foam using a high pressure mixing head comprising:

• a body including a mixing chamber and injectors for injecting at least two polymeric liquids, wherein a spool is moveable in the mixing chamber in a longitudinal direction thereof between a retracted position in which the injectors are able to inject jets of polymeric liquids into the mixing chamber to be mixed under turbulent conditions so that a reactive polymeric mixture is expelled from an output opening of the mixing chamber, and an advanced position in which the spool is advanced in the mixing chamber beyond the injectors and the polymeric liquids from the injectors are returned to be recycled via recycling channels, and
• a delivery duct which is disposed transversely to the mixing chamber, wherein a rod is slidably received in an internal passageway of the delivery duct and is connected to a piston of an actuator configured to move the rod along a longitudinal axis of the delivery duct between a retracted position in which the internal passageway along the delivery duct is in flow communication with the mixing chamber to receive the reactive polymeric mixture expelled from the output opening for conveying the reactive polymeric mixture along the internal passageway and into a distributor connected to an output end of the delivery duct for dispensing the polymeric foam resulting from the reactive polymeric mixture, and an advanced position in which the rod is moved all along the internal passageway for cleaning the internal passageway, wherein the rod is of complementary cross-sectional shape to the internal passageway of the delivery duct so that the rod closes the internal passageway up to the position the rod is moved to,
• wherein an alternate delivery duct extends transversely to the delivery duct and to the mixing chamber, and wherein the delivery duct and the alternate delivery duct are in flow communication with the mixing chamber via a switchable flow connection, and a control unit is configured to control the switchable flow connection and the positions of the rods in the delivery duct and the alternate delivery duct such that flow from the output opening of the mixing chamber can be selectively directed either to the delivery duct or to the alternate delivery duct, the method comprising:
• during a first phase of a continuous production run, setting the switchable flow connection of the high pressure mixing head to direct polymeric mixture expelled from the mixing chamber through the delivery duct for dispensing the polymeric foam resulting from reactive polymeric mixture through the distributor onto a moving substrate below the distributor,
• for terminating the first phase and for initiating a second alternate phase of the continuous production run, switching the switchable flow connection and the positions of the rods in the delivery duct and the alternate delivery duct over such that flow from the output opening of the mixing chamber is directed to the alternate delivery duct to thereby immediately switch over to the alternate delivery duct as active output component for dispensing the polymeric foam through the through distributor of the alternate delivery duct onto the moving substrate for continuing the continuous production run in the second phase, and
• during the second phase of the production run, cleaning the delivery duct and cleaning or replacing a distributor of the delivery duct.

A polymeric foam distribution system including:

• a conveyor configured to transport a substrate in a transport direction;
• and
• a multiple mixing head assembly comprising at least two high pressure mixing heads, wherein in each mixing head includes
• a body including a mixing chamber and injectors for injecting at least two polymeric liquids, wherein a spool is moveable in the mixing chamber in a longitudinal direction thereof between a retracted position in which the injectors are able to inject jets of polymeric liquids into the mixing chamber to be mixed under turbulent conditions so that a reactive polymeric mixture is expelled from an output opening of the mixing chamber, and an advanced position in which the spool is advanced in the mixing chamber beyond the injectors and the polymeric liquids from the injectors are returned to be recycled via recycling channels, and
• a delivery duct which is disposed transversely to the mixing chamber, wherein a rod is slidably received in an internal passageway of the delivery duct and is connected to a piston of an actuator configured to move the rod along a longitudinal axis of the delivery duct between a retracted position in which the internal passageway along the delivery duct is in flow communication with the mixing chamber to receive the reactive polymeric mixture expelled from the output opening for conveying the reactive polymeric mixture along the internal passageway and into a distributor connected to an output end of the delivery duct for dispensing the polymeric foam resulting from the reactive polymeric mixture, and an advanced position in which the rod is moved all along the internal passageway for cleaning the internal passageway, wherein the rod is of complementary cross-sectional shape to the internal passageway of the delivery duct so that the rod closes the internal passageway up to the position the rod is moved to,
• wherein an alternate delivery duct extends transversely to the delivery duct and to the mixing chamber, and wherein the delivery duct and the alternate delivery duct are in flow communication with the mixing chamber via a switchable flow connection, and a control unit is configured to control the switchable flow connection and the positions of the rods in the delivery duct and the alternate delivery duct such that flow from the output opening of the mixing chamber can be selectively directed either to the delivery duct or to the alternate delivery duct,
• the multiple mixing head assembly comprising a mounting frame including a longitudinal structure on which the mixing heads are mounted spaced apart from each other in a linear arrangement extending transversely to the transport direction of the substrate, wherein each of the mixing heads is arranged on the longitudinal structure to deliver a part of the polymeric foam that forms a foam layer on the advancing substrate, thereby distributing the foam in a direction transverse to the transport direction of the substrate, wherein the multiple mixing head assembly is further provided with a distributor replacement mechanism for detaching a set of distributors which are associated with one of the delivery ducts and the alternate delivery ducts of the mixing heads and for moving the detached set of distributors in a transverse direction to the transport direction of the substrate out of the zone above the substrate to allow replacement of the distributors while production continues utilizing the other one of the delivery ducts and the alternate delivery ducts for delivering polymeric foam.