Trigger switch speed control with electrical feedback

Claim 2

A power control and feedback regulating system providing continuous control of electrical power supplied from an alternating current source to a load device starting from zero power and continuing over a substantial range of power values comprising: a control semiconductor means having a primary current path and a secondary, control current path having a portion common with said primary current path at one side thereof; means for connecting said primary current path in circuit with the load device across the source with at least the responsive portion of the load device being connected to said common portion; a variable time delay means energized from the source for providing a firing signal to the control current path for rendering said semiconductor means conducting in its primary current path at controlled times when half-cycles of positive source voltage are being applied to the primary current path comprising: a firing control capacitor connected across said control current path; adjustable reference voltage means for controlling the conduction angle of said semiconductor means; means comprising a unidirectional conducting element coupling said adjustable reference voltage means to the common junction of said firing control capacitor and said control current path; a feedback loop circuit including said adjustable reference voltage means, said unidirectional conducting element, said firing control capacitor and a responsive portion of the load device wherein the latter provides a voltage proportional to the load device operation and is poled with respect to said reference voltage to afford, in a compensating manner, a resultant voltage for charging said firing control capacitor to a pedestal voltage level early on each positive half-cycle of the source voltage; and ramp voltage control means connected between the other side of said primary current path and said common junction for controlling charging of said capacitor in response to each sine wave positive half-cycle of source voltage to a ramp voltage having a cosine characteristic which is superimposed on said pedestal voltage to afford a large change in firing angle in response to a relatively small change in pedestal voltage.

Claim 3

The invention defined in claim 1, wherein said adjustable reference voltage means comprises: a unidirectional conducting device poled to block current flow into said adjuStable reference voltage means on each negative half-cycle of the source voltage thereby to prevent any negative current from flowing in shunt of said responsive portion of the load.

Claim 4

The invention defined in claim 1, wherein said adjustable reference voltage means comprises: phase shifting means for providing said reference voltage with a leading phase angle relative to each positive half-cycle of the source voltage whereby to afford rapid charging of said firing control capacitor to the full value of said pedestal voltage very early at the beginning of each positive half-cycle of source voltage.

Claim 5

The invention defined in claim 1, wherein said adjustable reference voltage means comprises: a capacitor and a potentiometer connected in series and the adjustable tap of said potentiometer being connected to said unidirectional conducting element, the combination of said capacitor and said potentiometer providing the reference voltage at said movable tap with a leading phase angle relative to each positive half-cycle of source voltage to assure the attainment of a proportionately constant peak voltage early in said positive half-cycle.

Claim 6

The invention defined in claim 4, wherein said adjustable reference voltage means also comprises: a trimming resistor connected across said potentiometer having a selected resistance value that compensates for variations in component values in the circuit from nominal values.

Claim 7

The invention defined in claim 1, together with: a unidirectional conducting discharge circuit of predetermined impedance connected in parallel with said ramp voltage control means affording discharging of said firing control capacitor uniformly to the same voltage level during each nonconduction period of the semiconductor means so that the firing control capacitor always recharges through said unidirectional conducting element to the resultant pedestal voltage thereby to insure accurate control of firing of the semiconductor means on each cycle of positive source voltage through a substantial range of conduction angles.

Claim 8

A motor control and speed regulating system comprising: an electric motor adapted to be supplied from an alternating current source and having series-connected armature and field windings; a solid state controlled rectifier having an anode-cathode circuit and a gate-cathode circuit; reference voltage control means including selectively adjustable means for deriving a variable reference voltage; a first circuit comprising means connecting said anode-cathode circuit and said armature winding and said field winding in series; a second circuit comprising means connecting said reference voltage control means and said field winding in series; means for connecting said first circuit and said second circuit in parallel across the alternating current source; firing voltage control means connected across said gate-cathode circuit; ramp voltage control means connected between the anode and gate of said controlled rectifier so that said ramp voltage control means and said firing voltage control means are connected in series across said anode-cathode circuit with their junction connected to the gate of said controlled rectifier; unidirectional conducting means coupling said selectively adjustable means to said junction for applying reference voltage to said firing voltage control means on positive anode voltage half-cycles; a speed signal feedback circuit including said armature winding, an adjustable portion of said reference voltage control means, said unidirectional conducting means and said firing voltage control means wherein a feedback voltage proportional to motor speed is compared with the reference voltage to afford a resultant voltage that is applied to said firing voltage control means to develop a pedestal voltage that regulates the firing voltage in a direction compensating for variations in motor speed due to changes in motor load; and said ramp voltage beiNg superimposed on said pedestal voltage to control the firing angle of said controlled rectifier in response to changes in magnitude of said pedestal voltage.

Claim 9

A motor control and speed regulating system comprising: an electric motor adapted to be supplied from an alternating current source and having series-connected armature and field windings; a solid state controlled rectifier having an anode-cathode circuit and a gate-cathode circuit; reference voltage control means including selectively adjustable means for deriving a variable reference voltage; a first circuit comprising means connecting said anode-cathode circuit and said armature winding and said field winding in series; a second circuit comprising means connecting said reference voltage control means and said field winding in series; means for connecting said first circuit and said second circuit in parallel across the alternating current source; firing voltage control means connected across said gate-cathode circuit; ramp voltage control means connected between the anode and gate of said controlled rectifier so that said ramp voltage control means and said firing voltage control means are connected in series across said anode-cathode circuit with their junction connected to the gate of said controlled rectifier; unidirectional conducting means coupling said selectively adjustable means to said junction for applying reference voltage to said firing voltage control means on positive anode voltage half-cycles; a speed signal feedback circuit including said armature winding, an adjustable portion of said reference voltage control means, said unidirectional conducting means and said firing voltage control means wherein a feedback voltage proportional to motor speed is compared with the reference voltage to afford a resultant voltage that is applied to said firing voltage control means to develop a pedestal voltage that regulates the firing voltage in a direction compensating for variations in motor speed due to changes in motor load; and said ramp voltage beiNg superimposed on said pedestal voltage to control the firing angle of said controlled rectifier in response to changes in magnitude of said pedestal voltage.

Claim 10

The invention defined in claim 7, together with: switch means for shunting said solid state controlled rectifier to connect said motor directly across the source for full speed operation; and said reference voltage control means comprising unidirectional conducting means poled to block current flow on negative voltage half-cycles therethrough in shunt of the motor armature winding.

Claim 11

The invention defined in claim 7, wherein said reference voltage control means comprises: a high impedance adjustable voltage divider circuit.

Claim 12

The invention defined in claim 9, wherein said high impedance adjustable voltage divider circuit comprises: a phase shifting capacitor and a potentiometer connected in series to provide a leading reference voltage.

Claim 13

The invention defined in claim 7, wherein said ramp voltage control means comprises: a resistor having a value determinative of the gain of the system, that is, the slope of the ramp voltage.

Claim 14

The invention defined in claim 7, together with: a diode-resistor circuit connected between the gate and anode of said controlled rectifier, said diode being poled to block current in response to a positive anode voltage on the controlled rectifier and to pass current in the opposite direction in response to the voltage on the firing voltage control means on nonconduction periods of the controlled rectifier.

Claim 15

In a series-motor operated portable tool connectable to an alternating current power source and having a hand grip including an opening therein for an operating trigger; a speed control unit having automatic feedback speed regulation comprising: an insulating base having an open top cavity therein; components of a motor speed control system mounted within said cavity; an insulating mounting plate at the top of said cavity and having electrical connectors on the lower surface thereof connecting said motor speed control components in circuit and to a plurality of electrical conductors extending through holes in the base, which conductors are adapted for connecting said system to the power source and the tool motor; an operating trigger and a frame clamping said trigger for sliding movement over said mounting plate; potentiometer means mounted on the upper surface of said mounting plate; switch means mounted on the upper surface of said mounting plate; means extending through said mounting plate for connecting said potentiometer means and said switch means to said connectors therebelow; a pair of contacts movable by said trigger for operating said potentiometer means and said switch means to said connectors therebelow; a pair of contacts movable by said trigger for operating said potentiometer means and said switch means, respectively, to effect operation and speed adjustment of the motor when said trigger is depressed; and said components of said motor speed control system that are housed within said base comprising: a semiconductor controlled rectifier having an anode-cathode circuit forming a power circuit therein and a gate-cathode circuit forming a firing control circuit therein; a reference voltage circuit that includes said potentiometer means; means including two of said conductors that extend through holes in the base for connecting said switch means, said controlled rectifier and the armature and field windings of the motor in series circuit across the power source; means including a third one of said conductors for connecting said reference voltage circuit in parallel with the portion of said series circuit that includes said controlled rectifier and the armature winding of the motor; firing control means including resistance means and a firing control capacitor connected in series in that order across said anode-cathode circuit with the common junction thereBetween being connected to the gate of the controlled rectifier for operation in response to each positive half-cycle of source voltage applied to the anode to develop a ramp voltage; unidirectional conducting means connecting the movable contact of said potentiometer means to said common junction for applying an adjustable reference voltage to said capacitor upon which said ramp voltage is superimposed; and a feedback loop circuit including a portion of said potentiometer means and the movable contact thereof, said unidirectional conducting means and said capacitor connected across the motor armature winding wherein the motor counter voltage that is proportional to motor speed is subtracted from the reference voltage for speed regulation purposes.

Claim 16

In a series-motor operated portable tool connectable to an alternating current power source and having a hand grip including an opening therein for an operating trigger; a speed control unit having automatic feedback speed regulation comprising: an insulating base having an open top cavity therein; components of a motor speed control system mounted within said cavity; an insulating mounting plate at the top of said cavity and having electrical connectors on the lower surface thereof connecting said motor speed control components in circuit and to a plurality of electrical conductors extending through holes in the base, which conductors are adapted for connecting said system to the power source and the tool motor; an operating trigger and a frame clamping said trigger for sliding movement over said mounting plate; potentiometer means mounted on the upper surface of said mounting plate; switch means mounted on the upper surface of said mounting plate; means extending through said mounting plate for connecting said potentiometer means and said switch means to said connectors therebelow; a pair of contacts movable by said trigger for operating said potentiometer means and said switch means to said connectors therebelow; a pair of contacts movable by said trigger for operating said potentiometer means and said switch means, respectively, to effect operation and speed adjustment of the motor when said trigger is depressed; and said components of said motor speed control system that are housed within said base comprising: a semiconductor controlled rectifier having an anode-cathode circuit forming a power circuit therein and a gate-cathode circuit forming a firing control circuit therein; a reference voltage circuit that includes said potentiometer means; means including two of said conductors that extend through holes in the base for connecting said switch means, said controlled rectifier and the armature and field windings of the motor in series circuit across the power source; means including a third one of said conductors for connecting said reference voltage circuit in parallel with the portion of said series circuit that includes said controlled rectifier and the armature winding of the motor; firing control means including resistance means and a firing control capacitor connected in series in that order across said anode-cathode circuit with the common junction thereBetween being connected to the gate of the controlled rectifier for operation in response to each positive half-cycle of source voltage applied to the anode to develop a ramp voltage; unidirectional conducting means connecting the movable contact of said potentiometer means to said common junction for applying an adjustable reference voltage to said capacitor upon which said ramp voltage is superimposed; and a feedback loop circuit including a portion of said potentiometer means and the movable contact thereof, said unidirectional conducting means and said capacitor connected across the motor armature winding wherein the motor counter voltage that is proportional to motor speed is subtracted from the reference voltage for speed regulation purposes.

Claim 17

The invention defined in claim 13, wherein said reference voltage circuit comprises: a capacitor connected in series with said potentiometer means externally of said feedback loop circuit for providing the reference voltage in said feedback loop circuit with a leading phase angle relative to the source voltage.

Claim 18

The invention defined in claim 13, together with: a low resistance discharge path effective on negative half-cycles of source voltage for discharging said firing control capacitor into said source.

Claim 19

In a power control and feedback regulating system providing continuous control of electrical power supplied from an alternating current source to a load device starting from zero power and continuing over a substantial range of power values, the combination comprising: a controllable semiconductor device for controlling a load circuit and comprising a pair of main current conduction electrodes and a control electrode; means for supplying said controllable semiconductor device from the alternating current source; a variable time delay means energized from the source for providing a firing signal to the control electrode for rendering said semiconductor device conducting in its main electrodes path at controlled times when half-cycles of source voltage are being applied to the main electrodes path comprising; a firing control capacitor connected between said control electrode and one of the main electrodes; adjustable reference voltage means for controlling the conduction angle of said semiconductor means; means comprising a unidirectional conducting element coupling said adjustable reference voltage means to the control electrode side of said firing control capacitor; a feedback loop circuit including said adjustable reference voltage means, said unidirectional conducting element, said firing control capacitor and a responsive portion of the load device wherein the latter provides a voltage proportional to the load device operation and is poled with respect to said reference voltage to afford, in a compensating manner, a resultant voltage for charging said firing control capacitor to a pedestal voltage level early on each said half-cycle of source voltage when said semiconductor device is to be rendered conducting; and ramp voltage control means supplied from said source for controlling charging of said capacitor in response to each said half-cycle of source voltage when said semiconductor device is to be rendered conducting to a ramp voltage which is superimposed on said pedestal voltage to afford a large change in firing angle in response to a relatively small change in pedestal voltage.

Claim 20

In a power control and feedback regulating system providing continuous control of electrical power supplied from an alternating current source to a load device starting from zero power and continuing over a substantial range of power values, the combination comprising: a controllable semiconductor device for controlling a load circuit and comprising a pair of main current conduction electrodes and a control electrode; means for supplying said controllable semiconductor device from the alternating current source; a variable time delay means energized from the source for providing a firing signal to the control electrode for rendering said semiconductor device conducting in its main electrodes path at controlled times when half-cycles of source voltage are being applied to the main electrodes path comprising; a firing control capacitor connected between said control electrode and one of the main electrodes; adjustable reference voltage means for controlling the conduction angle of said semiconductor means; means comprising a unidirectional conducting element coupling said adjustable reference voltage means to the control electrode side of said firing control capacitor; a feedback loop circuit including said adjustable reference voltage means, said unidirectional conducting element, said firing control capacitor and a responsive portion of the load device wherein the latter provides a voltage proportional to the load device operation and is poled with respect to said reference voltage to afford, in a compensating manner, a resultant voltage for charging said firing control capacitor to a pedestal voltage level early on each said half-cycle of source voltage when said semiconductor device is to be rendered conducting; and ramp voltage control means supplied from said source for controlling charging of said capacitor in response to each said half-cycle of source voltage when said semiconductor device is to be rendered conducting to a ramp voltage which is superimposed on said pedestal voltage to afford a large change in firing angle in response to a relatively small change in pedestal voltage.

Claim 21

The invention defined in claim 16, wherein: said ramp voltage control means is adjustable to allow selective variation in the gain thereof.

Claim 22

In a power control and regulating system providing continuous control of electrical power supplied from an alternating current source to a load device starting from zero power and continuing over a substantial range of power values, the combination comprising: a current control means having a primary current path and a control electrode; means for connecting said primary current path in circuit with the load device across the source; a variable time delay means providing a signal to the control electrode for rendering the primary current path of said current control means conductive for a portion of each alternation of the source voltage, comprising: a control capacitor connected to said control electrode so as to provide storage and timed response to currents applied there to; an adjustable reference voltage means; a voltage source responsive to said load device operation; coupling means for joining said control capacitor, adjustable reference voltage means and voltage source in a feedback loop circuit wherein said voltage source is poled with respect to said reference voltage to afford, in a compensating manner, a resultant voltage for charging said control capacitor to a pedestal voltage level during the off periods of said current control means; and a ramp voltage control means for adding charge to said control capacitor in synchronism with the source voltage alternations, wherein said ramp voltage is superimposed on said pedestal voltage to afford a large change in said conducting portions of subsequent alternations of the source voltage in response to a relatively small change in pedestal voltage.

Claim 23

In a power control and regulating system providing continuous control of electrical power supplied from an alternating current source to a load device starting from zero power and continuing over a substantial range of power values, the combination comprising: a current control means having a primary current path and a control electrode; means for connecting said primary current path in circuit with the load device across the source; a variable time delay means providing a signal to the control electrode for rendering the primary current path of said current control means conductive for a portion of each alternation of the source voltage, comprising: a control capacitor connected to said control electrode so as to provide storage and timed response to currents applied there to; an adjustable reference voltage means; a voltage source responsive to said load device operation; coupling means for joining said control capacitor, adjustable reference voltage means and voltage source in a feedback loop circuit wherein said voltage source is poled with respect to said reference voltage to afford, in a compensating manner, a resultant voltage for charging said control capacitor to a pedestal voltage level during the off periods of said current control means; and a ramp voltage control means for adding charge to said control capacitor in synchronism with the source voltage alternations, wherein said ramp voltage is superimposed on said pedestal voltage to afford a large change in said conducting portions of subsequent alternations of the source voltage in response to a relatively small change in pedestal voltage.

Claim 24

The invention defined in claim 18, wherein said voltage source responsive to the load device operation is a portion of said load device.

Claim 25

The invention defined in claim 18, wherein said ramp voltage control means is adjustable to allow selective variation in the gain thereof.