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The Development of the Molded Diaphragm

A groundbreaking invention

This is the story of a technological quantum leap. In the early 1970s, KNF develops a new type of diaphragm which breaks all the ultimate vacuum and gas tightness records of the past. This new invention is called a molded diaphragm.

Previously, KNF has only implemented flat diaphragms in its work. The flat, round rubber discs are mounted to the connecting rod using a retainer plate and a bolt, which is fed through a hole in the middle of the diaphragm. However, this design limits gas tightness and pneumatic capacity. By contrast, molded diaphragms offer the major advantage that they combine with the connecting rod head to form a closed, compact element, which is completely closed off from the pump chamber. The molded diaphragm’s malleable surface means that it can be adjusted to fit any working chamber, thereby reducing dead volume and significantly improving the vacuum.

The molded diaphragms are developed in KNF’s then recently opened testing laboratory in Munzingen in the early 1970s. The goal is to design a new model series for flow rates of approximately 25 to 80 l/min which achieve an ultimate vacuum of less than 100 mbar – the standard for KNF pumps until that time. The end result is a system capable of reaching an ultimate vacuum of below 1.33 mbar, equating to 99.8% vacuum.

Ambitious endeavors: Erich Becker’s project group brainstorms new product ideas.
Ambitious endeavors: Erich Becker’s project group brainstorms new product ideas.

Josef Waibel has just started at KNF and is helping to set up the testing laboratory, when he is tasked with developing the NMP7 – the first molded diaphragm pump. He still clearly remembers the initial difficulties. “The greatest problem was that the molded diaphragms did not hold. The strain was too much because of the high vacuum.” He and Heinz Riedlinger, then director of the testing department, try out many different solutions until they finally get a handle on the issue. “Back then, we didn’t work with drawings. We just did things, only making a sketch afterwards to be brought down to the drafting office, where the details would be fleshed out.”

The first pump with a molded diaphragm enters the market in 1973 and is immediately met with great interest. Thanks to its high gas tightness, the pump represents a breakthrough in analysis technology. One year later, the mini NV 72 E pumps are already being used in laboratories and in measuring instruments in industry and medical technology. They are also used to study cigarette smoke.

But this technology is not the last groundbreaking invention to come from KNF’s testing laboratory. In addition to flat and molded diaphragms, KNF has since added structured diaphragms, zone diaphragms, convoluted diaphragms and oval diaphragms to its portfolio. All of these options are available depending on the application.

Various models: The development of different types of diaphragm contributes considerably to KNF’s success.
Various models: The development of different types of diaphragm contributes considerably to KNF’s success.
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