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Abstract

A method and apparatus for use with a sewing machine by which a liquid is injected between lapped layers of material being sewn. A supply of the liquid at atmospheric pressure is fed by gravity to a constant displacement pump, the pump being actuated by a driven part of the sewing machine so that pumping rate is proportional to sewing rate. The outlet of the pump passes through a line which divides under the control of valve means. One branch of the line leads to a tube that is disposed in a folder, the tube having a discharge end projecting from the folder and disposed just upstream of the sewing machine needle(s). A further flattening roller is disposed after the presser foot through which the needles reciprocate. The other branch of the line is a return line that leads back to the reservoir. Thus pressurized metered liquid such as sealant is injected between the layers of material and the liquid is hydrostatically pressurized by the pressure foot so that when the needle passes therethrough, the liquid is forced into the space in each needle hole surrounding the thread. A subsequent flattening or repressurizing step is provided for the seam after it has left the pressure foot. The flow of liquid is interrupted just before the end of the seam is reached, such as two inches, to prevent the discharge of an excessive amount of liquid.

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