The Development of the 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.

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.