US2713120A - Electronic stimulator - Google Patents

Description

July 12, 1955 D. MOSTOFSKY ET Ai.

ELECTRONIC STIMULATOR 3 Sheets-Sheet l Filed OCT.. 22, 1952 July 12, 1955 D. MOSTOFSKY ET A1. 2,713,120

ELECTRONIC STIMULATOR Filed om. 22, 1952 s sheets-sheet 2 JWM EN .Www NW .m mw N- l1- i 4| Q3 H 11| Si @n m bvwl www X823 XN mi EN w QQ m -TLV www THE/R HTToR/vsys July 12, 1955 D, MOSTOFSKY ET AL 2,713,120

ELECTRONIC STIMULATOR Filed Oct. 22, 1952 3 Sheets-Sheet 3 u LLI IS I-l United States Patent O ELECTRONIC STIMULATOR David Mostofsky, Brooklyn, and Alexander Sandow, New York, N. Y., assignors, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Application October 22, 1952, Serial No. 316,292

10 Claims. (Cl. Z50- 27) This invention relates to electronic Stimulators and is directed particularly to a high current output, dual pulse, electronic stimulator for physiologic purposes.

Physiologie Stimulators heretofore used were generally electronic devices which produced variously shaped voltage pulses for application directly through wires to living structures such as nerve or muscle. A voltage output was suitable in such cases, for the living tissue involved opposed the ow of current with a high impedance (of the order of 1000 ohms or more), and the electric power required, therefore, was insigniiicantly small.

A new stimulation technique has recently been developed in which a physiologic structure, a muscle, for example, is immersed in an electrolytic bath containing two large so called massive silver-silver chloride electrodes symmetrically anking the muscle. An electric stimulating pulse must pass from electrode to electrode through the intervening electrolytic solution and on its way stimulate the muscle supported in the electrolyte. The actual impedance of such a massive electrode system is in the order of 9 ohms. To cover the varied needs of the physiologic experiments, currents ranging from a fraction of an ampere to as high as 5 amperes are required to activate the contractile response of the muscle. It is manifest that under such conditions of stimulation, high impedance output voltage generators heretofore employed in direct connection with the muscle have inappropriate characteristics.

Accordingly, it is one object of this invention to provide an electric stimulator that can produce high-current pulses across an uncommonly low impedance.

it is @other object to provide a stimulator of the character described that can produce a unit-cycle consisting of two rectangular pulses each of which is independently variable, in duration from 30 to 25,00() microseconds, and in amplitude.

It is another object to provide a stimulator of the above nature wherein the individual pulses comprising the unitcycle can be set, selectively, to be of either the same or opposite relative polarity.

t is another object to provide a stimulator of the character described wherein the interval separating the individual pulses of the unit-cycle is independently variable in duration from zero to 25,000 microseconds.

It is a further object ofthe invention to provide such a stimulator wherein the timing variables are smoothly and continuously adjustable.

It is a further object of the invention to provide such a stimulator wherein the unit-cycle can be obtained on demand either once, or repetitively at rates from one every ten seconds to 600 per second for an indefinite or limited time interval.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the following drawings wherein:

2,713,120 Patented July 12, 1955 Fig. 1 is a block diagram of the improved stimulator illustrating pulse wave shapes from circuit to circuit.

Fig. 2 is an electrical schematic diagram of the pulse generator and synchronizer circuits of the improved stimulator.

Fig. 3 is an electrical schematic diagram of the power amplifier circuit of the improved stimulator; and

Fig. 4 illustrates the massive electrode arrangement for stimulation of a muscle experimented upon in accordance with the invention.

The overall operation of the stimulator as illustrated in Fig. 1 will first be given. The rst pulse of a unit-cycle is initiated by a positive trigger pulse 10 of about 30 volts supplied by a separate trigger generator, (not shown). The trigger generator can be, for example, a variable frequency thyratron-controlled relaxation oscillator. Such pulse generators are well-known in the art and therefore not further described herein. The input pulse l() triggers the iirst phantastron 12, the time interval of which determines the time of the first pulse.

The output wave-form of the phantastron circuit 12 is trapezoidal, as indicated by the numeral 14. Therefore two shaping circuits 16 and 18 follow, the first providing an output wave-shape as indicated by the numeral 20, and the second the required substantially rectangular wave-shape 22. The second Shaper 18 also functions as a mixer when it is desired that the two unit-pulses be of the same polarity, (as hereinbelow more fully described); the second pulse being introduced in its output circuit. The shaper-'nixer stage 18 is followed by a driver stage 24, which produces a large rectangular pulse 26 of about 230 volts for input to a power amplifier stage 2S.

The output of the first phantastron 12 is also fed through a cathode follower 30, the output wave-form of which is indicated by the numeral 32, to a differentiating circuit or peaker 34. The output wave-form of the peaker, indicated by the numeral 36, comprises a positive spike corresponding to the trailing edge of the first phantastron pulse 14, and is used toV trigger a blocking oscillator circuit 38 to provide a narrow pulse 4i) of the order of l microsecond in duration. This pulse, in turn, is fed into an interval phantastron 42, which determines the interval between the individual pulses of the unit-cycle.

The output 44 of the interval phantastron 42 is fed through a cathode follower 46, the output 48 of which is fed into a second differentiating circuit peaker 50. The output 52 of the peaker 5l) comprises a sharp positive voltage pulse that is used to trigger a second blocking oscillator 54. A sharp trigger voltage 56 is obtained from the second blocking oscillator. This marks the trailing edge of the output wave-form 44 of the interval phantastron and initiates the action of a third phantastron 58, thereby determining the beginning of the second output pulse of the unit-cycle. Therefore, the interval between the trailing edge of the first pulse and the beginning of the second pulse is determined by the time of the interval phantastron 4 2. Y

The output 66 of the third or pulse 2 phantastron S8 is trapezoidal, like that` of the lirst or pulse l phantastron 12, and is followed by an amplier-shaper 62 to obtain a rectangular pulse 64, which is fed selectively through a single-pole double-throw switch 66 either to a mixer-Shaper 63 or a Shaper 70, depending upon whether it is desired to have the individual pulses of the unit-cycle of the same or opposite polarity. Thus, if the switch 66 is thrown to the right, as shown in the drawing, the pulse 64 from the amplifier-Shaper 62 is fed through the shaper 70, the output of which is a negative rectangular pulse 72, into a driver stage 74,

0 the output 76 of which is a positive rectangular pulse 46, thence directly into the power amplier 28, whereby an output unit-cycle 78 having individual pulses of opposite relative polarity is produced, as hereinbelow more fully described. If the switch 66 is thrown to the left, as indicated by the dotted-line position, the pulse 64 is ted through the mixer-Shaper 68, the output of which Pulse generator and synchrolzzer circuit description The basic timing and pulse-forming action of the stimulator is performed by the identical phantastron circuits comprising the pentodes 82, 84 and S6 for the pulse l phantastron, the interval phantastron, and the pulse 2 phantastron, respectively (see Fig. 2). Since the action of phantastron circuits has been fully described in the literature (see, for example, the article: Design of Phantastron Time Delay Circuits, published in the April 1948 issue of Electronics page 10G) it is deemed sufcient to say here that the output of such a circuit is a negative trapezoidal pulse, smoothly variable over a wide range and with a fall and rise time that is quite rapid. Individual diodes comprising the vacuum tube 88 are included in they grid circuits of each of the phantastron circuits to permit operation at rates up to 600 or more unit-cycles per second with the relatively wider pulses and intervals. These diodes peru mit a more rapid recovery of the grid voltage after the pulse.

The timing of the phantastron pulses is determined by the voltage applied to the pentode plates, and, except for extremely narrow time intervals, there is a linear relationship between this voltage and the pulse width. Thus, inthe pulse 1 phantastron circuit, the control voltage is applied to the plate of the pentode 82 through a diode 9i) which isolates the plate from `the `control voltage during the phantastron cycle when the plate voltage is lowered. The two 500) ohm potentiometers 92, 94 in the phantastron circuit are adjustw ments that determine the maximum and minimum voltage obtained from the 20,000 ohm potentiometer 96, which is the phantastr'on pulse width control. rThe 50i) ohm potentiometer 9d is a tine control. The condenser 100, connected from the cathode of the diode 9i? to ground, makes the adjustment of the `potentiometers smooth, and permits the location of the potentionieters to be remote from the phantastron circuit.

The output of the pulse 1 phantastron is taken from the cathode of the pentode d2.' This trapezoidal voltage pulse (see pulse 14 of Fig. l), goes to the grid of pulse.

20 of Fig.Y 1). This pulse is coupled to the next stage through a large time constant network comprising the condenser 164i, the resistor 106 and potentiometer E158. The diode 116 connecting the grid side of the condenser 104 to ground is a clamper or D C. restorer which keepsV the D. C. level on the grid of the succeeding Stage fixed, despite wide changes in pulse rate, pulse width, and setting of the potentiometer 1% connected to the grid of the triode112 comprising the following stage. The potentiometer lt determines the ,amplitude of the output pulses. The triode 112 is biased to cut- O so hat only the positiveY part of the pulse is amplifled. The negative overshoot portion, therefore, is not obtained in the plate circuit of this tube. It will be noted that the plate of the triode 112 is connected to the plate of the triode 114, but since these tubes are each biased to cut-ofi they do not load each other. It can be seen, however, that a pulse introduced on the Agrid of the triode 114 will appear at the plate of the triOde 112.

From the plate of the triode 112, the rectangular i When pulses in the unit-cycle of opposite polarity are pulse, which is now negative (see pulse 22, Fig. 1) is applied to the grid of a vacuum tube 116, which is the driver stage for the power amplifier, to be described hereinbelow. driver tube 116 supplies its own restorer action, since its cathode is directly connected to ground and the pulses are negative at the grid.

The pulse interval is the time from the trailing edge of the iirst pulse to the beginning of the second pulse. This interval is determined by the duration of the intervai phantastron circuit comprising the pentode 84.Y This phautastron is triggered by a spike that corresponds to the trailing edge of the first phantastron output pulse (see pulse 49 of Fig. l). Y

The pulse on the cathode of the rst phantastron pentode 82 not only is connected to the shaping circuits, as hereinabove described, but also goesto a trigger-forming circuit by way of a cathode follower circuit comprising the triode 11S, which isolates the rst phantastron circuit from the circuits that follow. The action of the triode 12% following the cathode follower stage is to diterentiate the trapezoidal pulse. Thus, on the secondary of the pulse transformer 122 in the plate circuit ofV phantastron. The tlow of current through the triode 121i` passes through a blocking oscillator transformer 132 whence, by transformer action, this current is applied regeneratively to the grid of the triode 1.23 to initiate the blocking oscillator action. The blocking oscillator triode 123 is biased to cut-oir by the network comprising voltage divider resistors 134 and 136 which supplies voltage v to the second grid of the interval phantastron pentode 84. The sharp positive pulse (see pulse 4@ of Fig. l), from the cathode of the blocking oscillator triode i223 is directly coupled to the interval phantastron pentode S4, which it triggers. The time from the beginning to the end of the interval phantastron pulse (see pulse 4e of Fig. l), determines the time interval between'the two output pulses of the stimulator.

The output of the interval phantastron'comprising the pentode 84 is Vdiii"erentiated and a blocking oscillator pulse corresponding to the trailing edge is obtained iu the same manner as described above. Thus, the circuits associated with the tubes 138, 149, 142, and 144 are the same as those of tubes 11S, 120, 124 and 123, respectively. The output voltage spike of the blocking oscillator comprising the triode 144 triggers the pulse 2 phantastron pentode 86, the output pulse of which after shaping, determines the second rectangular output pulse.

The output of the pulse 2 phantastron is shaped in the amplienshaper comprising the triode 146 and then is utilized in one of two ways, selectively. lf a unitcycle of two rectangular' output pulses of the same polarity is reguired, the pulse from the triode 1.45 is switched, by means of the double-pole doublethrow switch 148, to the grid of the triade 11d from which, by way of the plate register 155? common to the triode 112, it is applied to the driver comprising the triode i316.

desired, the pulse from the triode 146 is switched to a Shaper circuit comprising the triode 152, from the piate of which it goes to the grid of a second driver comprising the tube 154. The reason for this switching will be apparent in the following description of the power amplier stage. Thus, either two pulses are obtained at the driver tube 116, or one each at tubes 116 and 154. Y

It should be noted that the grid of the Fig. 3 is a schematic drawing of the power amplifier' circuit. The amplifier derives its plate power directly from a 117 volt D. C. service line. It comprises a plurality of triodes connected in parallel and, either in single-ended or push-pull arrangement, depending upon whether output pulses of the same or opposite polarity are desired. The single-pole double-throw switch 156 and the double-pole double-throw switch 158 control the operation of the amplier. Thus, when the switches are at their solid-line position as shown in Fig. 3, the operation of the amplider is such as to provide a unit-.cycle having individual pulses of opposite polarity.

The circuit comprises a row (row 1), of triodes 160 havingindividual plate resistors 162 and grid isolating resistors 164. The triodes 160 are heavily biased beyond cut-oit by connection of the isolating resistors 164 to a source of negative voltage supply of about 120 volts through a common bias resistor 166,` A diode 168 across the bias resistor 166 clamps the bias at this lixed value. Thus, no current ilows through the tubes except when a pulse is received from the pulse generator and synchronizer circuit (Fig. 2). r[he circuit is arranged as a cathode follower, the output load being connected across the common cathode resistor 170 connected between the cathodes of the triode 162. and ground. The parallel triodes 160 of row 1 serve to amplify the positive output pulse of the unit-cycle. A similar circuit comprising a plurality of triodes 172 (row 2) is connected to receive the second pulse from the pulse generator and synchronizer circuit and deliver across a common cathode resistor 174 the second 0r negative output pulse of the unit-cycle. The cathode resistors 170 and 174 are of about 200 ohms each so that there is no appreciable loading ofthe massive electrode device.

Though the rows 1 and 2 as illustrated comprise tive triodes each, it is to be understood that more could be aded to each row to increase the output power of the amplier.

When the switches 156 and 158 are at the dotted-line position as shown in Fig. 3, the operation of the amplitier is such as to provide a unit-cycle having individual pulses of positive polarity. In this case it will readily be seen that the triodes 172 of row 2 are switched to operate in parallel with the triodes 160 through the common cathode load resistor 170; the low impedance output terminal being connected to ground.

Operation Fig. 4 illustrates the method of stimulating a muscle in accordance with the invention. The muscle M immersed in an electrolyte E is clamped in position at its lower end, and its upper end is mechanically connected to a recording transducer (not shown), which can be a piezoelectric device, for example. Actuation of the transducer by the contractile response of the muscle to stimulation produces a proportional outputl voltage that is recorded by suitable electrical recording apparatus. The massive plates or electrodes X and Y are connected to the output of the electric stimulator.

lf pulses in the unit-cycle of opposite polarity are desired, the switches in Figs. 2 and 3 are set to their full-line positions. if pulses of the same polarity are desired, the switches will be set at their dotted-line positions. Pulse and interval widths are controlled by adjustment of the respective potentiometers in the pulse l" phantastron circuit comprising the pentode 32, the interval phantastron comprising the pentode 84, and the pulse 2 phantastron comprising the phantastron 85. The amplitudes of the first and second pulses are independently controlled by adjustment of the potentiometers 108 and 302. in the plate circuits of triodes 102 and 146, respectively.

In order that the invention can be practiced with the least amount of routine circuit design, the Afollowing list of circuit element values found to be satisfactory in a practical embodiment of the invention is given:

POTENTIOBIETERS v ohms 92 5,000 94 5,000 96 20,000 9s 500 10s 50,000 23s 20,000 240 500 244 5,000 246 5,000 282 20,000 284 500 28s 5,000 292 5,000 302 50,000

RESISTORS 106 500,000 134 50,000 136 5,000 50,000 162 50 164 10,000 166 1,000 170 200 174 200 176 50,000 17s 5,000 180 15,000 182 5,600 134 1,000 186 5,000 18s 10,000 190 25,000 192 12,000 194 3,000 196 33,000 19s 500,000 200 40,000 202 2,700 204 150,000 206 1,200 20s 15-,000 210 47,000 212 8,200 214 500,000 216 60,000 21s 50,000 220 500,000 222 27,000 224 27,000 226 15,000 22s 5,600 230 1,100 232' 5,000 234 10,000 236l 25,000 242 12,000 24s 3,000 250. 500,000 252- 60,000 254 *50,000 256 y 500,000 25s Y 270,000 260 10,000 262 27,000 264 270,000 266 50,000 26s 5,000 270 15,000 272 .5,600

Ohms

276 Y 5,000 278 10,000 280` 25,0007V 286 12,000 292 D 3,000 294 Y Y Y 33,000 296 `500,000 298 4 n v Y 40,000 300 500,000 304 i K Y Y Y 150,000 306 2,700 308 Y, V50,000 310 A 2,700 312 150,000 314` 1,200 V316 15,000

Y CONDENSERS 100 microfarads 16 104 do 4 130 do 50 318 micromicrofarads 200 320 microfarads 0.09 Y 322 do V1 324 i do 4 326 d0 2. V328 do 0.2 330 do 0.5 332V Ydo 16 334 Y do 0.05 336 rnicromicrofarads 500 338 microfarads 0.09 340 l do 16 342 do 0.2 344j do 0.5 345 Y do `16 346 do 348 Y Y do V 0.05 350 micromicrofarads 500 352 microfarads y0.09 354 do i1 356 do Y 4 358 do 4 360 do -Y 2 368 d0 V16 VACUUM TUBES 82` "6SA7 6SA7 6SA7 '6SN7'GJ/z) r102 6SL7'(1/2) 6H6(1/2) Y 112 v 6s77-(1/2) 114 "6'SL7(1/1`) 116V `6V6 Y 118 `6SN7'(1/2) 120 i V6SN7(1/2) 123 '6SN7(1/2`) 124 '6SN7(1/2) 138 `6SN7(1/z) 140 SNTU/) 142V 6SN7(1/'2) 144 6SN7(%) 146. 6SL7(1/2) 152 V6SL7(12) 154 V 6AS7 168 l6H6(1/2) 172 V6AS7 362 6SN7(1/2) 364 6SN7v(1/2') 366 `6SN7(1/2) 368 6SN7.(1/2) Ohms 370 6SN7,(1/2 372 6H6(Vz) 374 6H6(%) gerjvoltage impulses, for producing a lirst output pulse,

means for deriving a second trigger voltage impulse coincident with an edge of said first output pulse, means actuated by said trigger voltage impulse for producing a second output pulse, means for deriving a third trigger voltage impulse coincident Vwithan edge'of said second output pulse, means, actuated by said third trigger vol*- age impulse, for producing a third outputpulse, a power amplifier, and means `for combining said irst and third output pulses in saidjpower amplifier to produce an outi put unit-cycle voltage wherein the rst pulse, an inter- Y val determinedY by the width of the second pulse, and

the third pulse appear in sequence.

2. A generator for producing rectangular pulses in a unit-cycle consisting of first and second pulses -separated by a time interval comprising a source of trigger voltage impulses, means, actuated by an impulse from said source of trigger voltage impulses, for producing a rst rectangular output pulse, rmeans for deriving a second trigger voltage impulse coincident with the trailing edge of said lirst rectangular output pulse, means, actuated by said second trigger voltage impulse lfor produc-V ing a second rectangular output pulse, means for deriving a third trigger voltage impulse coincident with theV 3. The invention as defined in claim 2 wherein means is provided for independently varying the duration of each of said first, second and third rectangular pulses.

4. The invention as defined in claim 2 including switch means in said power Yamplifier for changing the relative polarity of said first and third pulses so as to be of the same or opposite relative polarity, selectively.

5. A generator for producing rectangular pulses in a unit-cycle consisting of rst and second pulses separated by a time interval comprising a source of trigger voltage impulses, each of which is adapted to initiate a unit-pulse cycle, a 'first phantastron circuit triggered by an impulse from said source whereby an output pulse of trapezoidal configuration is obtained, means for shaping the trape zoidal pulse output of said rst phantastron into a rst rectangular pulse, an interval phantastron circuit, means controlled by the voltage change comprising the trailing edge of the output pulse of said iirst phantastron for initiating a second trapezoidal output pulse from said interval phantastron, a third phantastron, means `controlled by the voltage change comprising the trailing edge of the output pulse of said interval phantastron for initiating a third trapezoidal output pulse from said ythird phantastron, means for shapingthe trapezoidal pulse Voutput of said third phantastron into a second rectangular an output unit-cycle voltage wherein the iirst rectangular pulse, the interval and the second rectangular pulse appear in sequence.

6. The invention as dened in claim 5 including means for independently varying the duration of each of said first interval and second output pulses.

7. The invention as defined in claim 5 including switch means in said power ampliiier for changing the relative polarity of said iirst and second pulses so as to be of the same or opposite polarity, selectively.

8. A generator for producing rectangular pulses in a unit cycle consisting of two pulses each of which is independently variable in duration and amplitude, the time interval between the two pulses of each unit being also variable, said generator comprising a source of synchronizing impulses each of which is adapted to initiate a unit pulse cycle, a iirst phantastron triggered by a synchronizing impulse from said source and designed to yield an output pulse of trapezoidal configuration, means for shaping the trapezoidal pulse output of said rst phantastroninto a iirst rectangular pulse, a first driver circuit, a power amplifier to which the said rectangular pulse is applied through said rst driver circuit, means for diierentiating the trapezoidal pulse output of said iirst phantastron, a first blocking oscillator, means for employing the diiferentiated iirst phantastron pulse to trigger said iirst blocking oscillator and thereby yield a further trigger impulse, a second phantastron, means for employing the trigger impulse from said rst blocking oscillator to initiate conduction of said second phantastron at a time corresponding to the instant of occurrence of the trailing edge of said first rectangular unit pulse, a second blocking oscillator, means for employing the pulse output of said second phantastron to trigger said second blocking oscillator and produce a still further pulse which marks the leading edge of the second rectangular unit pulse, so that the operation of said second phantastron determines the time interval between the said two unit pulses, a third phantastron triggered by the said second blocking oscillator pulse and yielding an output pulse of trapezoidal configuration and means for shaping the trapezoidal4 pulse output of said third phantastron into a rectangular pulse.

9. A pulse generator according to claim 8, further comprising means for applyingthe rectangular pulse output from said third phantastron to said power ampliiier through said iirst driver circuit, whereby an output is obtained from said amplifier in which the iirst and second pulses of each unit cycle are of the same polarity.

l0. A pulse generator according to claim 8, further comprising a second driver circuit, and means for applying the rectangular pulse output from said third phantastron to said power amplifier through said second driver circuit, whereby an output is obtained from said amplier in which the first and second pulses of each unit cycle are of opposite polarity. Y

No references cited.

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