Typically linear actuators are electromechanical devices that provide linear mechanical motion in response to receiving electrical energy. Linear actuators may be utilized in many high-force and high-precision applications. One configuration of a linear actuator consists of a cylindrical core that is free to move axially. An air gap is formed between the cylindrical core and a cylindrical shell that surrounds the core. Both the cylindrical shell and coil are made of soft iron. A pair of magnets made of permanent magnet material are affixed to opposite ends of the core. The magnets are radially magnetized and orientated on the core such that the magnets are opposite in polarity. A coil assembly is positioned circumferentially about the core. The coil assembly consists of two coils connected together in series, each coil being wound in opposite directions. Current applied to the coil generates a magnetic field, which is aided by the static magnetic field produced by the magnet pair, moving the core axially. The core moves bi-directionally in response to the orientation of the current applied to the coil.
The coil assembly described above adds unnecessary manufacturing complexity to the actuator design. For example, such an assembly requires one coil to be wound in one direction (clockwise) and while the other coil is wound in the opposite direction (counterclockwise). The process of winding two separate coils and connecting the coils adds additional manufacturing steps, adding to the overall cost of the actuator. Moreover, the inherent resistance associated with this type of coil construction is somewhat high due to the series connection of the two coils. The high resistance of the coil requires a relatively high voltage power supply to achieve a desirable power density (force output per unit volume) for the actuator. Consequently, a heavier wire is typically utilized with this type of coil assembly to lower the total resistance. However the heavier wire is more difficult to wind; yielding complex manufacturing techniques with the associated high costs.
The present invention is directed to overcoming one or more of the problems as set forth above.