Rubber Diaphragms
Rubber diaphragms are flexible seals that are resistant to a variety of media at different pressures. Molded rubber diaphragms in particular are characteristically tough, versatile and dynamic, capable of eliminating virtually all of the limitations that are associated with other sealing methods such as
o-rings, metal bellows or u-cups. Typically, rubber diaphragms act as a barrier between two chambers and function to transmit pressure between systems without exchanging media. As a result, rubber diaphragms are considered to be essential in many flow control applications. Rubber diaphragms are commonly constructed from elastomers such as
silicone,
natural rubber, viton, fluoroelastomers, flurosilicone, styrene butadiene rubber (SBR), nitrile rubber (NBR) and EPDM rubber. The type of rubber often affects the application of the diaphragm; however, typical applications include vacuum sealing, pressure switches, synthetic nipples, flow regulators, regulators, activation mechanisms, fluid control valves, pumps and accumulators. A cost-effective product, many industries utilize rubber diaphragms including automotive, petrochemical, pharmaceutical, food processing, industrial, commercial, textile and semiconductor.
Three common molding processes that can be used to form rubber diaphragms include compression molding, injection molding and transfer molding. Compression molding squeezes the rubber material which has been placed within a heated mold cavity until excess material comes out as flash or sprue, at which time the mold is removed to set in open air. Transfer molding is similar to compression molding, except that the mixed resin is first placed in a heated transfer chamber until it is liquefied, then it is pressed into the heated mold by a plunger until a flash forms; rubber transfer molding is unique in its ability to mold other materials, such as strengthening fabric, within a rubber part. Injection molding is the latest advancement in rubber diaphragm molding, producing high tolerance, highly repeatable parts with short production times. In addition, there are several different types of rubber diaphragm configurations, the most common of which include flat, top hat, and dish shapes. Flat rubber diaphragms offer a limited stroke capability and are made from various calendared rubber materials. Top hat diaphragms offer the longest stroke capability; however, they are limited by their height. Dish shape diaphragms have a sidewall that slopes gradually that allows them to be flexed in both directions.