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ORIGINATOR OF THE ROLLING DIAPHRAGM

THE ROLLING DIAPHRAGM CONCEPTCONQUERING FRICTION

The Bellofram Rolling Diaphragm
âœ£ () is a tough, flexible seal with a unique configuration that permitsrelatively long piston strokes while completely eliminating sliding friction.Formed in the shape of a truncated cone, or top hat, the diaphragm is turned in on itself when installed so that,during the stroke, it rolls and unrolls alternately on piston skirt and cylinder wall. The rolling action is smooth and effortless, completely eliminating sliding contact and breakaway friction. With the outer flange clamped to the cylinder and the center fastened to the piston head, the forms aperfect barrier, preventing blow-by leakage and pressure loss. Depending on the materials and geometry selected, can function effectively with applied pressures of3000 pounds. Operating temperatures may range from –120 º F to +600 º F. Diaphragms are available which arehighly resistant to oil, ozone, acids, alkalies, steam and other corrosive fluids. R Fig. 1: Rolling Diaphragm installed in cylinder
OLLING D
IAPHRAGM C
ONSTRUCTION diaphragm material is essentially a layer of specially woven fabric, impregnated with a thinlayer of elastomer. Total thickness is usually 0.015 to 0.045 inches. The fabric, which lends high ten-sile strength to the diaphragm, is designed to permit free circumferential elongation (allowing freerolling action) while preventing axial distortion. This eliminates stretching or ballooning during thestroke.The flex life of the rolling diaphragm depends on operating pressures, amount of axial and cir-cumferential stress applied during the stroke, and the materials which form it. In general, aproperly installed will provide a life of millions of cycles. Fig. 2: Construction R
OLLING D
IAPHRAGM A
PPLICATIONS Because of its unique properties, the is widely used in controls and actuators requir-ing high sensitivity to small pressure changes and excellent accuracy and reproducibility. Theyare also used where no leakage can be tolerated, and where more liberal machining tolerancescan significantly reduce hardware costs. Typical products using the include:pressure regulators, linear actuators, demand valves, dashpots, measuring instruments,gauge protectors, air relays, etc.
*Patent numbers 3,137,215 and 3,373.236

ROLLING DIAPHRAGM OPERATING FEATURES & BENEFITS

•Friction-Free Sliding friction is completely eliminated •No Breakaway Friction No resistance to start-up motion even after long periods in one position •No Spring Rate No change in resistance to applied pressure throughout stroke •High Sensitivity Extremely responsive to small pressure variations •Long Life Smooth, non-abrading operation and tough construction ensure long operating life •Leak-Proof No blow-by leakage •Versatile Can be furnished for a broad-range of pressures, temperatures and fluids •Low Hysteresis Provides consistent positioning with identical applied pressures, regardless of stroke direction