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They are found everywhere today. In distribution systems for air, water, steam, hydraulic fluids, vacuum, oil, grease, paint, liquid food – in fact almost anything that flows through a hose or tube. If a hose or tube in a system is going to be connected or disconnected more than once a week, a Quick-Disconnect Coupling will save money and labor by speeding up the job. Although they are simple in concept, Quick Disconnect Couplings are precisely engineered for specific fluid applications. The more one understands about their design, construction and principles of operation, the more valuable they become in solving fluid-line problems.

There are three basic types of quick couplings; single shut-off, double shut-off, and straight-through.

Single shut-off couplings - sometimes referred to as One-Way shut-off or Pneumatic couplings

As the term implies, single shut-off couplings have a check valve in one half, usually the socket half and no valve in the mating half referred to as plug (Figure 1). This design is normally used in systems where spillage of fluid on the down-stream side is unimportant. Single shut-off couplings are normally installed with the valved half on the pressure side of the circuit to provide automatic shut-off flow when the coupling is disconnected.

This type of coupling is commonly associated with compressed air systems. However, the coupling is used on many other applications including lubrication, paint spray, and carpet cleaning equipment.

Single shut-offs normally have low working pressure capabilities ranging from 100 to 300 PSI.

1. Industrial Interchange Types (65% of market volume). This type of air coupler was the basis for the original patent on quick disconnect type couplers by Fred Hansen, founder of the Hansen Coupling Company, in 1915. The patent was based upon the position of the locking balls and their grip on the plug half of the coupling.  At present, all companies domestically and most European and Asian Quick Coupler Manufacturers catalog this design. Hansen’s products are the 1000 and 3000 series.
2. Truflate Type (10% of market volume). This type of air coupling, characterized by its very short plug nose, was developed by the Doerge brothers in Oakland, California during the 1920’s for the purpose of superseding the Hansen patent which was still in effect. They started the Truflate Coupling Co. and achieved wide acceptance on the West Coast and east to Denver. Also, since their specialty market was the automotive aftermarket, this coupling design received great acceptance in the automotive parts stores, muffler shops and tire garages. Today the Truflate coupling is a part of the Parker Quick Coupling Division. Truflate having been bought by Parker in 1965 as their first, and at that time, their only Quick Coupling product line. Its best 1993 markets are still the automotive MRO market and the Staple and Nailing Industry. All major manufacturers have now cataloged this design.  Hansen uses the Auto-flo 23
3. Aro Type (9% of market volume).  This type of air coupling works essentially the same way as other One-Way couplers.  It is characterized by a comparatively long plug nose and does not interchange with the two previous types.  It was developed by the ARO Coupling Company of Byron, Ohio, and purchased by Tuthill Coupling Group in 1998. The European interchange for the ARO coupler is made by Orion of France. Most major coupler manufacturers have picked up this design.
4. Schrader Type (4% of market volume). This coupling was developed during the late ‘30’s as an automatic push to connect not susceptible to accidental disconnect due to snagging the sleeve while pulling the hose line across rough surfaces. To disconnect, the sleeve has to be twisted instead of sliding back and forth. This coupling received acceptance in many industries where this twist feature was saleable, i.e. military-industrial and dental-medical industries. This company was located in Waterbury, Connecticut before being bought by Parker, and thus the coupling received its widest acceptance in New England. Hansen has no interchange
5. Lincoln Type (4% of market volume). The Lincoln “long nose” was developed during the 1930’s to supersede the Hansen patent (expired during 1938). It was sold through Lincoln Lubricator Distribution and many industrial supply stores. It also received acceptance in the automotive industry because of Lincoln’s distribution in that industry. Hansen has no interchange.
6. European Designs (3% of market volume). Various European manufacturers have established in the U.S. with proprietary designs; most importantly Cejn-Sweden, and Obac-Germany. These European manufacturers have not had any great success with their proprietary type designs and have had to copy one of the above U.S. types to get market share. Hansen uses the Auto-flo 24.
7. Japanese Designs (2-3% of market volume). Metric based plug dimensions essentially sold by Nitto, mainly through distribution active with Japanese care and associated supplier plants utilizing Japanese production equipment. Hansen has no interchange for these types.
8. For more information please see Hansen's FAQ page on http://coupling.tuthill.com/Support/TrainingDocument/quickcouplings.asp