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US 4,635,927 AGranted
Low power treadmill
AssigneeDel Mar Avionics
InventorStephen K. Shu
Life of this patent
Estimating the term…
Abstract
The specification discloses an exercise treadmill for diagnostic and therapeutic purposes incorporating an improved drive and control system. High efficiency at low rpm is effectuated through the use of a DC motor which maintains the belt speed constant by varying the width of the applied pulse duration as a function of load. Additional load buffering between the belt and motor is effectuated by a double flywheel configuration.
Claims8
A treadmill for diagnostic and therapeutic purposes comprising:
- an endless belt supported at each end by a cylindrical roller;
- a DC motor;
- a DC reference voltage;
- velocity sensing means responsively coupled to said DC motor for generating a voltage which is proportional to the angular speed of said DC motor;
- pulse width control means responsively connected to said velocity sensing means for generating a gating pulse having a duration which is proportional to the difference between the voltage generated by said velocity sensing means and said reference voltage;
- means for coupling said DC motor to said endless belt;
- power supply means for converting a standard 110 volt 60 cps household power to a unidirectional potential;
- switching means having its main terminals series connected between said DC motor and the output of said power supply means and its gating terminal responsively connected to said pulse width control means, for controlling the duration of the DC voltage applied to said DC motor in response to the width of the pulses generated by said pulse width control means
- at least one semiconductor switching device;
- a choke means having a low DC resistance;
- a resistor connected in parallel with said choke means;
- means for connecting said switching device in series with the parallel combination of said resistor and said choke means, and;
- means for connecting the network comprised of said semiconductor switching device and said choke means and said resistor in parallel with said DC motor, and;
- means for actuating said switching device so as to cause said switching device to short circuit said choke means and resistor network across the terminals of said DC motor.
11 more elements
In a treadmill of the type employing a variable speed drive, the improvement which comprises:
- a DC motor;
- a DC power supply;
- switching means connected between said DC power supply and said DC motor, and having a control terminal and a pair of main terminals for chopping the output of said DC power supply so as to generate a succession of equal amplitude pulses for operating said DC motor;
- control means for generating a reference voltage which is proportional to the desired angular motor velocity;
- detector means for generating a voltage which is proportional to the actual angular velocity of said DC motor;
- gating means responsively connected to said detector means and said control means for generating a signal having a duration which is proportional to the difference between the magnitude of the voltage produced by said control means and said detector means;
- said gating means comprises a pulse width modulator and further including;
- means for generating a sawtooth voltage;
- comparison means for detecting when the amplitude of the sawtooth voltage reaches a predetermined level which is functionally dependent upon the difference between the magnitude of the output generated by said control means and the magnitude of the potential generated by said detector means;
- means for generating a pulse having a time width equal to the time required for the sawtooth voltage to rise from a predetermined base value to the potential required to actuate said comparison means;
- coupling means operatively connected between the output of said gating means and the input to the control terminal of said switching means for applying the gating signal generated by said gating means to the control terminal of said switching means so as to cause the duration of the DC pulses applied to said DC motor to increase in proportion to the difference between the magnitude of the voltage generated by said control means and the voltage generated by said detector means.
8 more elements
Dependencies are inferred from the claim text.