Acoustic window and method for making the same

A method of making from a moldable polyurethane material an acoustic window that is free of imperfections that can distort acoustic energy, said method comprising the steps of:

• preparing a mold cavity having the form of the acoustic window for the receipt of the polyurethane molding material;
• preparing the polyurethane molding material for injection into the mold;
• positioning the mold cavity with the first port located above the second port;
• simultaneously applying a vacuum to the first port and supplying the polyurethane molding material from a first reservoir to the second port such that the pressure differential created by the vacuum displaces the polyurethane molding material into the cavity thereby to fill the mold;
• removing the vacuum from the first port and applying a second reservoir thereto after polyurethane molding material begins to overfill the mold;
• adding additional polyurethane molding material into the cavity through the first reservoir and second port so as to displace polyurethane molding material through the first port into the second reservoir;
• simultaneously applying heat to the mold and external pressure to the polyurethane molding material in the first and second reservoirs so as to heat and compress the polyurethane molding material and curing the molding material into a solid cured polyurethane acoustic windows by placing it in an oven operating at about 100.degree. C. and at a pressure of about 75 psig;
• and
• thereafter removing the solid cured polyurethane acoustic window from the mold.

A cured polyurethane molded product formed of a polyurethane molding material in a mold wherein the mold defines a molding cavity and has first and second spaced ports to the molding cavity, said product being formed by the process comprising the steps of:

• preparing the mold cavity for the receipt of the molding material;
• positioning the mold cavity with the first port located above the second port;
• simultaneously applying a vacuum to the first port and supplying the molding material from a first reservoir to the second port such that the pressure differential created by the vacuum displaces molding material into the cavity;
• removing the vacuum from the first port and applying a Second reservoir thereto after molding material begins to exit the first port;
• adding additional molding material to the molding cavity through said first reservoir to displace molding material through the first port into the second reservoir;
• simultaneously applying heat to the mold and external pressure to the first and second reservoirs so as to heat and compress the molding material and curing the molding material into a solid cured polyurethane article by placing it in an oven operating at about 100.degree. C. and at a pressure of about 75 psig;
• and
• thereafter removing the solid cured polyurethane article from the mold.

A molded polyurethane acoustic window that is free of imperfections that can distort acoustic energy formed by the process comprising the steps of:

• preparing a mold cavity having the form of the acoustic window for the receipt of the polyurethane molding material;
• preparing the polyurethane molding material for injection into the mold;
• positioning the mold cavity with the first port located above the second port;
• simultaneously applying a vacuum to the first port and supplying the polyurethane molding material from a first reservoir to the second port such that the pressure differential created by the vacuum displaces the polyurethane molding material into the cavity thereby to fill the mold;
• removing the vacuum from the first port and applying a second reservoir thereto after polyurethane molding material begins to overfill the mold;
• adding additional polyurethane molding material into the cavity through the first reservoir and second port so as to displace polyurethane molding material through the first port into the second reservoir;
• simultaneously applying heat to the mold and external pressure to the polyurethane molding material in the first and second reservoirs so as to heat and compress the polyurethane molding material and curing the molding material into a solid cured polyurethane acoustic window by placing it in an oven operating at about 100.degree. C. and at a pressure of about 75 psig;
• and
• thereafter removing the solid cured polyurethane acoustic window from the mold.