Tubular Linear Motor

Novel design features integral ball bearings
and just one moving part

Linear motors have evolved quickly in their short lifetime, so much so that they have applications in nearly all industries. Not only have their speed and torque capabilities changed, but they have been packaged in a number of configurations.

California Linear Devices, Inc. (CLDI), Carlsbad, CA, adds yet another linear motor design into the mix. A culmination of several years of development, the tubular linear motor boasts features like integral ball bearings and just one moving part. At first glance, the motor resembles a hydraulic or pneumatic cylinder. To achieve the design, CLDI engineers took the basic concept of a 3-phase, rotary brushless DC motor and rearranged the ring-shaped permanent magnets in an alternating polarity along the length of the shaft. The stator was then developed as cylindrical coils and pole pieces placed around the shaft. The length and diameter of the stator determine the force level. By taking this approach, electromagnetic interaction takes place over the entire surface of the shaft, producing high linear forces per volume with no backlash or compressibility effects to compromise positioning accuracy. The motor uses neodymium-iron-boron magnets, and maximum frequency response -- acceleration and deceleration -- is 60 Hz over a distance of 1/8 in.

The first motor to be offered by the company, designated 5020-4, has a peak force of 750 lbs (with 30A excitation), with a selection of standard linear stroke lengths ranging from 2- to 12-in., in 2-in. increments. Peak acceleration with no load is more than 24,000 in./sec/sec. The case size of the 5020-4 is 12-in. long by 7.1-in. dia., and the mass of a 2- x 12-in. shaft is 11.125 lbs. These motors have been optimized for an operating voltage 340 VDC and a supply voltage of 220 VAC. Applications can be in automation and robotics, packaging equipment, vibration simulation, and process or pumping equipment.

--RM

For more information: Circle 555 - California Linear Devices, Inc., or connect directly to their website via the Online Reader Service Program at http://www.1rs.com/011df-555