One of the U.S. pioneers of injection molding machinery, William Lester, died March 12 at his home in Delray Beach, Fla. He was 97.
The engineer was inducted into the Plastics Hall of Fame in 1986.
According to an obituary in the New York Times, Lester died from injuries suffered after a fall. The newspaper contacted his wife, Gloria Genin Lester.
Back in the 1930s and 1940s, Cleveland-made Lester machines were among only a handful of U.S.-made presses available.
The history of Lester Engineering Co. is recorded in Injection Molding of Plastics by Islyn Thomas.
Lester designed his first injection press in 1934, as a partner in Commonwealth Plastics Co., a joint venture in Leominster, Mass., according to the Plastics Hall of Fame. Most presses at the time were hand-crank versions, but Lester developed a hydraulic machine with a 4-ounce shot that could mold parts on a six-second cycle.
William's father, Nathan Lester, founded Lester Engineering in 1936. He had a background in die-casting. In 1931, he successfully had injected plastic material into a die on one of his die-casting machines.
Nathan Lester got excited about the fledgling plastics industry. He developed a horizontal press with what Thomas called a ``radically different'' design, a vertical injection unit. Like other early presses in the days before the reciprocating screw, the Lester machines used a plunger inside a heated cylinder to ram plastic into the mold, similar to rubber molding technology.
The first Lester injection molding presses used tie bars to guide the platens - in fact, except for the unusual vertical heating cylinder, they looked much like today's machines.
But engineers discovered the tie-bar frame required large nuts to join the tie bars to the body of the press, a difficult, costly process. Molding pressure also tended to misalign the frame.
So the firm improved the design and came out with a ``beam frame'' press, a much more sturdy frame that used thick metal beams to carry the platens.
Another important feature was a patented mechanism to adjust the moving platen so the operator could adjust for molds of different thicknesses.
Irvin Rubin knew William Lester in the 1950s when both were active in the Society of Plastics Engineers. Rubin bought a few Lester machines for his molding company, Robinson Plastics Corp. in Hoboken, N.J.
``He was a very open, congenial guy and very focused on whatever he did,'' Rubin said.
Lester also founded Pyro Plastics Corp. and ran the custom molder for many years. After selling Pyro Plastics in 1972, Lester focused on tamper-evident packaging. One of his patented inventions was the dispensing closure for squeezable containers.
Lester also was a longtime supporter of the Technion - a technological institute in Israel. He was a founding member of the American Technion Society.
Rubin said Lester Engineering did make the transition from plunger to reciprocating-screw machines - that's the type he bought for Robinson Plastics.
``It was a good machine, by the way,'' he said.