Serviceable Servomotor Couplings

• backlash free

• misalignment compensation

Servomotors are usually mounted to a gearbox or other drive element with either a rigid quill mount or a coupling inside a flange. Using a metal bellows coupling compensates simultaneously for axial, lateral and angular misalignment. These couplings normally require an access hole on the side of the flange, allowing a technician get a wrench into the flange to tighten a clamp screw in order to mount the coupling onto a shaft. During maintenance, the motor often must be removed by two people — one rotating the motor shaft while the second, holding a flashlight, tries to get a wrench lined up with the clamp screw of the coupling. Sometimes the coupling is on so tight it is extremely difficult to pull apart, or alternately the motor shaft may not rotate, requiring destruction of the flange to gain access to the coupling. Both scenarios are costly and time consuming.

Incorporating a Blind Mate feature into a bellow coupling design, the BK5 coupling consists of two halves. One half is comprised of a clamping hub, a stainless steel bellow and a female taper segment, while the other half consists of the male taper segment with a clamping hub. The male segment is made of a glass-reinforced polymer molded onto an aluminum or steel clamping hub. It has equally spaced “driving segments” built into the design. When the two halves are mounted and properly pre-tensioned the connection is absolutely backlash free. The male segment is generally mounted onto the motor and the other half onto the driven element. When maintenance is required the motor is simply unbolted and the coupling pulls effortlessly apart. A technician no longer has to turn a motor shaft to align a flange access hole with a coupling mounting screw.

BK5 couplings are available in sizes to accommodate a torque range of 15 to 500 Nm (133 to 4425 in. lbs.) and shaft sizes of 8 to 60 mm (0.31 to 2.375 in.). An axial mounted BK6 version is also available for applications where a flange access hole is not possible. The BK6 incorporates tapered clamping segments that are tightened from the end of the coupling and not from the side (see illustration). It is suited for tight spaces where other machine components block side access to the coupling.