Hand drilling

Abstract

.Iadd.A hand drill includes an induction motor energized by a multi-phase electrical power source with the angle between consecutive phase maintained substantially constant over a wide frequency range by energizing logical circuitry comprising a number of flip-flops intercoupled by AND GATES. .Iaddend.

What is claimed is: 
     
       1. Hand drilling apparatus comprising: means defining a casing that can be held in one hand,   means secured to said casing for supporting a bit for high speed rotary motion,   an electric brushless motor having a rotor inductively coupled to a stator and supported by said casing for imparting rotary motion through means including the bit supporting means to a bit when supported by the latter,   a source of multi-phase electrical power of controllable frequency,   leads coupling said electrical power source to said electrical brushless motor,   and means for adjusting the frequency of said electrical power to control the speed of said rotary motion to a maximum in the range of 200,000 r.p.m..Iadd.,   said source of multi-phase electrical power of controllable frequency comprising,   a pulse source of variable frequency,   at least first and second flip-flops having set and reset inputs and set and reset outputs,   and means including a plurality of AND gates for intercoupling said pulse source and said flip-flops for providing from like outputs of said first and second flip-flops signal waveforms of frequency determined by said pulse source with phase displaced from each other by a fraction of the period at said frequency independent of said frequency over a wide frequency range,   and first and second power amplifiers with respective inputs coupled to respective like outputs of said first and second flip-flops and respective outputs coupled to respective windings of said brushless motor for establishing a rotating field in said motor causing said rotor to rotate at a frequency related to that of said pulse source,   and said means for adjusting comprises means for adjusting the frequency of said pulse source.Iaddend..   
     
     
       2. Hand drilling apparatus in accordance with claim 1 wherein said frequency is in the audio frequency range. 
     
     
       3. Hand drilling apparatus in accordance with claim 2 and further comprising: means for also adjusting the magnitude of said electrical power.   
     
     
       4. Hand drilling apparatus in accordance with claim 2 and further comprising: a single control for simultaneously adjusting both said electrical power frequency and magnitude.   
     
     
       5. Hand drilling apparatus in accordance with claim 1 wherein: said casing defines a contra-angle,   said means for supporting the bit being secured to one end of the casing and the motor being secured to the other end of said casing,   drive and driven pulleys secured to the motor and means for supporting the bit, respectively,   idler pulleys mounted in the casing adjacent the angle in the casing,   and a belt connected between the drive and driven pulleys and guided by the idler pulleys.   
     
     
       6. Hand drilling apparatus in accordance with claim 1 wherein: the means for adjusting the frequency of said electrical power provides continuous frequency adjustment in the audio frequency range.   
     
     
       7. A method of high speed drilling with controlled speed which method includes the steps of: applying multiphase electrical power of continuously controllable frequency to an electrical brushless motor with a stator inductively coupled to a rotor that rotates the drilling bit,   and adjusting said continuously controllable frequency to control the speed of rotation while maintaining the phase angle between the phases of the electric power substantially the same.Iadd.,   the step of applying multiphase electrical power of continuously controllable frequency including applying pulses from a pulse source of controllable frequency to at least first and second flip-flops having set and reset inputs and set and reset outputs through gating means,   and applying output potentials from each of said set and reset outputs to respective ones of said gating means to sequentially enable respective ones of said gating means to transmit pulses from said pulse source to respective ones of said set and reset inputs to produce on like outputs of said first and second flip-flops waveforms of a frequency determined by said pulse source displaced in phase by a fraction of the period at the frequency of said waveforms independent of said frequency over a wide frequency range,   and power amplifying respective output waveforms from said first and second flip-flops to respective stator windings of said electrical brushless motor to establish a rotating electrical field that causes said rotor to rotate at a frequency determined by that of said pulse source.Iaddend..   
     
     
       8. A method of high speed drilling in accordance with claim 7 and further including the step of also adjusting the magnitude of said electrical power to control said speed of rotation. 
     
     
       9. A method of high speed drilling in accordance with claim 8 wherein said controllable frequency and said magnitude are adjusted simultaneously. .Iadd.10. Hand drilling apparatus in accordance with claim 1 wherein said logical circuitry includes a first AND gate for enabling the transmission therethrough of a pulse from said pulse source to the set input of said first flip-flop when said second flip-flop is in a first of its two stable states, a second AND gate for enabling the transmission of a pulse from said pulse source to the set input of said second flip-flop when said first flip-flop is in a second of its two stable states,   third gating means for transmitting a pulse from said pulse source to the reset input of said first flip-flop when said second flip-flop is in a second of its two stable states,   and fourth gating means for transmitting a pulse from said pulse source to the reset input of said second flip-flop when said first flip-flop is in a first of its two stable states. .Iaddend. .Iadd.11. A method of high speed drilling with controlled speed in accordance with claim 7 and further including the steps of enabling a first of said gating means to transmit pulses from said pulse source to the set input of said first flip-flop when said second flip-flop is in a first of its two stable states;   enabling a second of said gating means to transmit pulses from said pulse source to the set input of said second flip-flop when said first flip-flop is in a second of its two stable states,   enabling a third of said gating means to transmit pulses from said pulse source to the reset input of said first flip-flop when said second flip-flop is in a second of its two stable states,   and enabling a fourth of said gating means to transmit pulses from said pulse source to the reset input of said second flip-flop when said first flip-flop is in a first of its two stable states. .Iaddend.