Bellows Couplings

Bellows couplings are connectors for shafts and equipment that require flexibility and non-linear alignment. These devices are composed of a rigid bellow and a coupling that transmits mechanical power between shafts, maintains constant velocity and compensates for axial motion and parallel or angular misalignment.

Typically the bellows are made from stainless steel which is an excellent transmitter of torque. The coupling is made of aluminum which makes these devices exceptionally lightweight and durable. Bronze is also sometimes used. The walls are thin enough to allow the coupling to flex while remaining relatively rigid.

Bellows couplings are cylindrical with flexible rings acting as the coupling. On either side are solid metal ends that connect to shafts or other components. They are typically quite short in length and range in diameter size from 1/8 inch to a full inch; custom or specialty sizes are available but do not greatly vary in construction or function.

Like shaftwheel couplings they are constructed to reduce vibration when used in applications with high rotations per minute (rpm). Mostly used in industrial machinery, bellows couplings create a quiet, smooth operation in systems with high levels of torsional integrity like encoder drives, closed loop servo systems, motion control instrumentation, robotics, CNC machine tools and precision positioning.

Cross Slot Bellows Couplings
Bellows Couplings – Helical Products Company, Inc.

Mechanical flexible couplings are made of loose fitting parts that move in a sliding and rolling manner; bellows couplings fit this category because they have a coil that allows them to move. Unlike other mechanical flexible shaft couplings, these generally need no lubrication. They offer a near-infinite life span and are virtually maintenance free. Their connection is hidden within the fit-length of the hub, enabling exact transmission of angular motion and torque.

Bellows couplings operate at high speeds anywhere from 12,000 to 32,000 rpm and absorb eccentricity and angularity. They are oil- and chemical-resistant, have thin and lightweight yet strong walls and offer easy and simple mounting and dismounting. Bellows couplings exhibit high torsional stiffness and zero backlash. The most common methods of construction for flexible couplings such as these include electroforming, chemical deposition, mechanical forming and welding.

Electroformed bellows couplings are made by adding layers of metal on a mandrel until the desired thickness is reached and the mandrel is melted away to leave behind the bellows. Chemical deposition is a similar method except that the materials are added by electrodeposition. Mechanical forming includes roll-forming or extrusion. Welded bellows couplings are made by welding a series of rings or washers on both their inside and outside.