Magnetic brake meets servopneumatics

Wednesday, August 30, 2000

Moving beyond the rough "bang-bang" linear motion of servopneumatics has been wrought with tough engineering work over the years. Air has traditionally been difficult to control because of its compressibility. Therefore, controlling the velocity, acceleration, and position of the carrier is inherently difficult.

Tol-o-matic claims it has overcome these technical challenges in linear motion by incorporating a proportional brake system that directly controls the position of the carrier. When valves are opened or closed at either end of the stroke, air enters the piston chamber applying a pressure force causing the piston to accelerate. A continuously controllable Rheonetic(R) brake, supplied by Lord Corp., provides a smooth resistance torque that finely controls the movement of the carrier.

The brake resistance torque is directly proportional to the current flowing in the coil. "The apparent viscosity of the fluid changes depending on the alignment of the spheres within the fluid," says Eddy Houchin, product manager at Lord. "If 1A is supplied to the brake, the fluid becomes a heavy cream, at 1.5A it is like peanut butter and at 2A it is like putty." For more information see http://www.tolomatic.com or http://www.lordcorp.com.