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No "Elbow" Room? Ultra-Miniature Pneumatic Elbow Fitting Fits Critical Medical Product To A "Tee"

(This article was authored by Michael J. Donati, VP of Sales/Marketing, Beswick Engineering Co., Inc. It was published online at www.ipb.com and on print by Industrial Product Bulletin in October 2004.)

In today's business world engineers are challenged to design products that are faster, lighter and incorporate more features into a smaller space. Successful products are often the ones that provided the desired functions in the smallest overall package. Miniaturization can mean the difference between success and failure in the marketplace. This is readily apparent in products such as semiconductors, cell phones, notebook computers, hard drives, PDAs, and flat screen TVs. Miniaturization is also a driving force in the pneumatic fitting industry.

The development of Beswick Engineering Co., Inc.'s ultra-miniature, low profile, adjustable position elbow fitting is an example of the miniaturization trend in pneumatic components. The development of this elbow fitting was initiated by a telephone call from a desperate design engineer at a large medical company. The design engineer explained that a regulatory agency had halted the production of their surgical stapler due to the failure of a plastic pneumatic fitting. He had noticed a Beswick press release describing a metal 10-32 threaded elbow fitting and wondered if Beswick could make something similar but, to fit into their application, it would have to be much smaller than the elbow fitting described in the press release.

MLA series - Ultra-miniature fixed position elbow

Beswick's first solution was an ultra-miniature, fixed position, elbow fitting ("MLA" series) with a built-in hose barb. The built-in hose barb feature was accomplished by soldering the barb to the fitting body. This concept eliminated the need for the body to the big enough to accept a female (internal) thread and allowed the selection of a 5/16-in. hexagonal body instead of a larger rectangular body. The resulting design reduced installed height by 44% (from 0.5500-in. to 0.281-in.) and reduced volume by more than 70% compared to conventional designs.

In addition to the built-in hose barb innovation, Beswick designed a precision-machined O-ring gland at the base of 10-32 thread to insure a leak-tight joint. This unique "captured" O-ring face seal design prevents leakage, even when the fitting is only finger tight, and provides a firm mechanical contact as well as a self-locking tendency. It eliminates the problems inherent with conventional gasket style fittings such as leaks, loose fittings, extra assembly costs, and the need to use messy thread sealants.

The "MLA" prototype was delivered to the customer and low volume production was initiated. Although the fitting physically fit into the application., because it was a fixed position design, the customer soon found that the hose barb did not always line up in the proper orientation after installation. The customer had not anticipated this issue but he now knew it would have to be solved before full production could resume.

MLAS series - Ultra-miniature adjustable position elbow

Beswick engineers went back to the drawing board. The application required an adjustable position fitting but how would this be achieved in such a small package? The answer was found by nesting the head of the screw stud into the 5/16-in. hexagonal body of the fitting.

This approach allowed Beswick to maintain the 0.281-in. installed height. Beswick was also able to retain the leak-tight O-ring seal design by incorporating a precision-machined gland under the head of the screw stud. This fitting was named the "MLAS" series and, as with the "MLA" series elbows, the hose barb was jointed to the fitting body with a solder joint. [Note: solder is no longer used on Beswick Engineering fittings.]

The space-saving features designed into the MLAS fitting make it the smallest 10-32 threaded adjustable position elbow in the world. It can be used in tight areas when nothing else will fit. Another benefit is its minimal weight. It weights only 0.11-oz.

SMLS series

The success of the "MLAS" elbow fitting lead to development of the "SMLS" series elbows. The "SMLS" is slightly bigger than the "MLAS" fitting, but is easier to manufacture especially in stainless steel alloys. The concepts pioneered in the development of the "MLAS" elbow has also been applied to the design of an even smaller M3 metric threaded elbow fitting.