What are push-pull circular connectors?

Push-pull circular connectors feature a spring-action cylindrical sleeve surrounding or within the integral connector housing that self-latches when the connector is pushed into position. The connection is released through a squeeze-and-pull, rotate-and-pull, or other specific unlocking action that prevents accidental disconnection. Push-pull circular connectors are available in numerous sizes, voltages, and pin counts, and in coaxial, triaxial, fluidic, and pneumatic configurations.

Look around any healthcare setting and you will see push-pull circular connectors everywhere. The medical market relies on these versatile, user-friendly, dependable connectors to connect handheld devices and stationary equipment. They aren’t just for healthcare equipment, though; push-pull circular connectors serve the industrial, Test & Measurement, A/V, communication, and other markets where reliability and easy handling are equally important.

The push-pull circular connector was invented by engineer and LEMO Connectors founder Léon Mouttet after he attended a 1954 electronics exhibition in Milan. At the show, he surveyed the standard circular connector selection — mainly screw-thread or bayonet-locking circular connectors — and noticed a problem: Those connector types require time and two hands to mate. Mouttet developed a quick-locking alternative solution, taking inspiration from the spring action used in car cigarette lighters. His new circular connector design eventually became the Push-Pull LEMO B Series connector.

Since then, many connector companies have launched proprietary push-pull circular connectors with unique properties that serve specific markets and applications.

Handling Advantages

Ergonomic handling is the hallmark of this circular connector type. The push-pull locking mechanism allows users to easily mate or disconnect equipment with just one hand or in blind mating situations. An audible or tactile “click” assures the user that the connection is complete and secure; no double-checking or visual confirmation is needed. This enables users at every skill level to quickly and reliably connect equipment. Keying, color coding, and LED options increase that reassurance.

Design Notes

• Standards No single certification or standard guides the design of push-pull circular connectors, leading to a huge range of variation and very few examples of interoperability across manufacturers. Many push-pull products are designed and tested to meet market-specific standards such as the medical electrical safety standard IEC 60606-1 and the military durability standard MIL-STD-810F.

• Mating Cycles Push-pull circular connectors are designed to have a minimum of 2,000 mating cycles for plastic versions and 5,000 mating cycles for metal versions, depending on manufacturer.

• Spacing Since no bulky tools are needed to connect push-pull connectors they may be mounted closely together, as they only require two fingers to grip the shell to connect or disconnect. (Additional clearance is needed for push-pulls that require a twist motion to disconnect.)

• Materials Metals used for circular push-push shell materials include copper, stainless steel, gold, and alloys. In the medical market, plastic or polymer options are favored for cleanability and aesthetics. The materials used in this market are typically crush-proof as well as able to withstand autoclave, UV sterilization, and other disinfection processes. In some cases, biocompatible materials may be required. Push-pulls used in space and other markets may need to meet outgassing requirements.

• Ruggedization Push-pull circular connectors and their cable assemblies are available with specific durability attributes to ensure rugged performance in high-reliability and harsh environment applications, including those that feature temperature extremes, radiation, rough handling, chemicals, and other environmental factors.

• Sealing Many manufacturers offer IP-rated protection against fluid and particulate ingress. Hermetic sealing within the connector can be enhanced with silicone O-rings and flexible polymer jacketing surrounding the cable assembly.

• Interference Electromagnetic interference (EMI) or radio-frequency interference (RFI) is a significant concern for devices used in environments filled with electronic equipment, such as medical settings and aviation. The use of metal in the shell and ground terminal helps mitigate this concern and enhanced shielding is available from some manufacturers.

Markets, Sectors, and Applications:

Medical (portable, handheld, diagnostic equipment), industrial (automation controls, robotics), Test & Measurement (analyzers, test equipment), A/V (event wiring, broadcast equipment), communications (antennas, radar, radio equipment), automotive (diagnostic and production equipment), mil/aero (soldier-worn equipment, portable devices), transportation (rail signaling, monitoring and control systems)