Abstract: A process for manufacturing highly wear and fatigue resistant steel components for power tools includes melting and mixing together a readily available base steel and alloying elements. The molten steel is cast into near-net-shape in an investment casting process. This method is cost competitive with forming the same component from steel with fewer alloying elements. In particular, clutch plates for a drill/driver or screw gun can be formed in this manner from a steel containing relatively large amounts of nickel and chromium, such as SAE 9310 steel, or from a steel containing a relatively large total amount of molybdenum and tungsten, such as AISI M2 steel.

Abstract: A simple, inexpensive yet highly versatile hair trimming device, particularly adapted for self use, comprises of a comb-frame (20), a blade-holder (22), and a detachable handle (24). The comb-frame having a comb portion with plurality of comb-teeth (32) flanked on either side by side-arms (26) has a rectangular horizontal through-hole (34) in its top portion to receive a shaft (46) of the detachable handle which may be temporarily fixed on any one of its two sides, right or left, thereby offering option of right-hand or left-hand use. The side-arms of the comb-frame have grooved tracks (28) to allow slidably mounting of the blade-holder. The blade-holder has a cutting blade (36) fixed on its inside surface.

Abstract: An induction motor drive uses direct vector control for zero speed start up. According to the invention, a speed sensorless induction motor is controlled at all speeds, including zero or substantially zero speed, using direct vector control. In order to utilize direct vector control at all speeds, it is necessary to derive accurate stator flux vectors at all speeds. This is accomplished in the present invention by calculating two sets of stator flux vectors in diverse manners. A first set of flux vectors is derived from measured stator terminal voltage quantities, and a second set of flux vectors is derived from measured stator current quantities. The first set of flux vectors is valid at non-zero speed and the second set of flux vectors is valid at substantially zero speed. The direct vector control utilizes one of the two sets of flux vectors in accordance with predetermined criteria indicative of zero and non-zero speed conditions.

Abstract: A speed sensorless hybrid vector control starts from zero speed by using indirect vector control with stator frequency equal to slip frequency. As soon as the rotor begins to rotate, the drive is converted to direct vector control for normal operation. The direct vector control uses several low pass filters. The first is a harmonic reducing filter for the sensed motor phase current and voltage signals. The others comprise integration apparatus used in the calculation of motor flux quantities from the motor phase current and voltage signals.