Patents by Inventor David H. Dawson

David H. Dawson has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Centrifugal extrusion apparatus which heat plastifies material by mechanical shearing action
    Patent number: 4050874
    Abstract: A centrifugal extruder is provided with a friction generating element within a hollow rotor of the extruder. The material to be extruded is heated by shear generated by differential rotation between the extruder rotor and a shear generating element. Heat plastification is obtained adjacent the periphery of the rotor and a very short heat history is added to material treated in the apparatus.
    Type: Grant
    Filed: February 25, 1976
    Date of Patent: September 27, 1977
    Assignee: The Dow Chemical Company
    Inventors: Douglas S. Chisholm, David H. Dawson
  • Tube treating and apparatus therefor
    Patent number: 4028037
    Abstract: Synthetic resinous thermoplastic tubing is reduced radially in diameter with minimal increase in length by passing the tube through a plurality of successively smaller dies wherein a minor portion of the die moves relative to a major portion of the die during the reduction step. Plastic tube is obtained which has a tendency to expand radially with a minimal alteration in its length. Such tubing is particularly suitable for lining of pipe.
    Type: Grant
    Filed: May 26, 1976
    Date of Patent: June 7, 1977
    Assignee: The Dow Chemical Company
    Inventor: David H. Dawson
  • Method for the preparation of plastic lined pipe
    Patent number: 3959424
    Abstract: Plastic lined pipe and fittings are prepared by forming a liner of a plastic material having a diameter greater than the inside diameter of the pipe or fitting to be lined, reducing the diameter of the liner by hydrostatically swaging the liner and inserting the swaged liner into the pipe or fitting and permitting the plastic memory of the liner to cause expansion and form an interference fit of the liner with the pipe.
    Type: Grant
    Filed: December 7, 1973
    Date of Patent: May 25, 1976
    Assignee: The Dow Chemical Company
    Inventors: David H. Dawson, Douglas S. Chisholm
  • Tube treating and method
    Patent number: 3939243
    Abstract: Synthetic resinous thermoplastic tubing is reduced radially in diameter with minimal increase in length by passing the tube through a plurality of successively smaller dies wherein a minor portion of the die moves relative to a major portion of the die during the reduction step. Plastic tube is obtained which has a tendency to expand radially with a minimal alteration in its length. Such tubing is particularly suitable for lining of pipe.
    Type: Grant
    Filed: August 19, 1974
    Date of Patent: February 17, 1976
    Assignee: The Dow Chemical Company
    Inventor: David H. Dawson