Nov. 5, 1946. ‘ . J. c. HINSEY ET ALI- ' _ 2,410,499 ' STVIMULAT‘OR Filed May 16, 1945' E" __ 5 Sheets-Sheet 1 ma.50gmh? mm,wd? l. ./e z MH , Ge. Nov; 5, 1946. 2,410,499 J. C. HINSEY EI‘AL ' ' STIMULATOR Filed May 16, 1945 3 Sheets-Sheet 3 5 wueml'om W Jase WWW/Q 3 cA an m Q ,mwmug.» n .v Patented Nov. 5, 1946 2,410,499 UNITED‘ STATES PATENT 'Ge‘oheg'an, Mamair'oneck, N. Y., assignors to the Government 'of'the United ‘States Application May 16, 1945, Serial No. 594,046 ‘3 Claims. (Cl. 128-421), 1. 2 _. Thisinvention relates generally to stimulating apparatus ‘but more particularly to a neurological stimulator designed primarily ‘for use in the op-‘ erating room when it is desired to stimulate vari ous parts of the nervous system eitheras a means of exploration or in experimental work. 7 H One object of the invention is to provide a stimulator in which the nature and strength of the stimulus can be accurately controlled and duplicated whenever necessary; f , I - . An'other object of the invention is to provide a stimulator which operates on an alternating cur rent of constant frequency and wave form. Another object of the invention is to provide a device of the class described - which provides a stimulus of constant ‘uniform strength. ' . v V A further object of the invention is to provide this apparatus, wave form and frequency are subject to wide variation from day to day and even from minute to minute. The voltage de livered varies widely with’ the resistance vof_ the tissues stimulated and‘vmay also ‘change materially as the battery ages. Thyratron andnsimilar stimg ulators supply relatively uniform frequency and wave form over awshort period but do not hold their calibration well. In addition, the voltage .10 delivered under no-load conditions is apt to be much higher than that under vactual stimulating conditions and for accurate results the voltage must be ‘measured by means of a-cathode'raygos cillograph orvacuum» tube voltmeter during-stim ulation. Sixty cycle sine wave stimulators have: been used previous to this invention but in gen eral, while theylmaybe safe for use by someone familiar with their construction, they are notsafe a stimulating device of the class described ‘which is of simple construction and which may be easily for use routinely by surgeons ‘not familiar with operated with a maximum of safety. ' electrical apparatus. ' , With these and other objects ‘in view, the inven tion consists of the construction and the ‘com bination of parts as well as of the detail an'dar-Q rangement of parts ‘as will be more particularly set forth vin ‘the speci?cation relative to the .ac companying drawings. ' . , Effectiveness’ of a stimulus depends upon fre~ quency, wave form and voltage delivered at the electrodes during stimulation.‘ Frequently, [re ported results ofqstim'ula'ting various parts of the nervous system are of little or no value'to other . workers because the conditions of stimulation are Referring to ‘the drawings in which like ‘parts not stated completely or accurately. For ex are in'dicated'by similar reference characters; ample, the v'oltageimay be stated withoutmention' Figure 1 is a perspective view showing the entire of whether it was measured atno-load, or during apparatus mounted in a container having side 30 stimulation, and in the case of stimulators with compartments forthe connecting cords; ‘Figure 2 is a plan View showing the under sur face of the lower panel and thefarrangement of high source-impedance, there may be a wide dif ference between the two. _.Where a sine wave stimulus was used, it‘ is frequently not clear thevarious electrical elements thereon; ' . ' whether it was measured in root mean square Figure 3 is a perspective view o'f'the fuse housing 35 volts, or peak-to-peak volts. It is seldom con-_ showing the fuses, a lower portion of the power venient to measure ‘an characteristics of the stim switch and ?lters; and Figure 4 is a diagrammatic View showing the electrical circuits of the apparatus. . ulus in ‘the operating room. The instrument de scribed ‘herein, which is designed to operate from ' 100—120 volt, 50-60 cycle power-lines, derives the Brie?y stated, the device comprises a stimulator 40 stimulus directly from the power source, and the which is operated by the ordinary house current, voltmeter for the range in use (which reads in and‘ which furnishes uniform stimulation at a R. M. S‘. volts) is connected directly across the predetermined voltage, wave form and frequency. electrodes. It is necessary, therefore, only to It is frequently'important thatthe surgeon know read the voltmeter during stimulation to present‘ the effective strength of the 'stimulushe is de 45 a clear ‘statement of the stimulus employed. An livering, for example,‘ if he stimulates a motor appropriate statement would bev as follows: “The nerve central to an injury and fails to elicit a stimulus employed was a sixty cyclesine wave at response from the muscles it is important that he 1.6 R. IV‘LS. volts, measured under load.” know whether this failure of response is due to The instrument has a low source-impedance nerve injury or to an inadequate stimulus; It 60 so that the voltage under load ‘will: ordinarily is further important that the stimulus be such deviate only slightly from'the ‘no-load. setting. that its nature and strength can be accurately To assure safety in the operationlof therdevice, recorded'and duplicated by other workers. the line voltage is passed through two‘trans ‘Much -_of the previous Work of stimulation has formers before application ‘to the patient to pre-. been‘ done with the Harvard Inductorium. "With 55 vent direct contact with the line even'inthe event 2,410,499 3 4 of insulation breakdown in one transformer. Power supply leads have been isolated in a Bake stat 43 (see Fig. 2). The other end of the variable resistance 42 is connected to the switch blade 44. lite compartment to prevent their direct contact The switch blades 44 and 45 of the switch 38 are connected by a conductor 45 which in turn is connected through conductor 41 to switch blade 48 of the magnetic switch or relay 49 as will be with the output circuit even in the event of breakage of one of the wires. In the opinion of the designers, this instrument is safer from the - standpoint of accidental shock than are most electrical instruments used in operating rooms. The device is adapted for use with a high and a, low range of voltages. The low range will be adequate for most work, and should be used‘ wherever possible. The high range is intended primarily for stimulation of the sensory cortex where 15-20 volts may sometimes be required. The high range should not be used on thefmotor‘ cortex. further explained. , , It will be noted that the switch blade 44 is adapted to contact the switch terminals 35 and 36, and switch blade 45 is adapted to contact switch terminals 39'and 40. These blades 44 and 45 operate simultaneously so that by setting the ' blades on the desired pair of contact terminals the circuit may be completed through either the 15 terminals'36 and 39 or the terminals 35 and 4B. ‘ The switch blade 5|! of the rheostat 43 is con . nected through conductor 5| to switch blade 52 . To furnish power supply, the instrument may be plugged directly into any 100-120 volt, 50-60 cycle A. 0, outlet. It may be operated from of , an electromagnetic switch or relay 49. tained by removing the six front-paneltscrews, and lifting the panel out of the case’. Spare fuses terminal 63 is connected through the conductor 61 and thence through conductors 68 and 21 to terminal 25 of the secondary winding 24 of the transformer IT. The other terminal 63 of the switch 66 is connected to terminal 26 of the sec ondary winding 24 of the transformer IT by The switch blades '48 and 52 of the relay, when ac 200-240 volt supplies by the use of an appropriate 20 tuated by energization of magnet 53 thereof, con tact terminals 54 and 55, and connect the leads step-down auto-transformer. The power supply 4‘! and 5| through conductors 56 and, 51 to the ground is used to dissipate static charges. The two applicator electrodes 58>and 59 of the hand instrument should, therefore, be used on power piece 60. The conductors 56 and 51 are bridged supplies which have one side grounded, and the step-down transformer, if used, should be of the 25 by a resistance 55' and a resistance 5'!’ is con nected from conductor 51 to conductor 5|. auto-transformer type.» , The magnetic switch on relay 49 comprises a ‘The instrument is protected by one-ampere central magnetic core wrapped by a coil 5| con fuses, mounted beneath thepanel. These should nected to the terminals 62 and 63. The terminal blow only if the instrument itself develops a de feet, or if it is plugged into‘ the wrong type of 30 52 is connected through conductor 54 to the ter minal 65 of the push button switch 66 and the power supply. Access to the fuses may be ob are provided, and will be found; in clips near the working fuses. _ ‘v ' i The apparatus includes an input circuit and an output circuit which ‘are inductively coupled bytwo transformers. Referring to Fig. 4, which shows a-diagrammatic outline of the circuits, the means of conductors ‘I0 and 28. numerals 10 and 11 indicate the terminals of a plug l2 which is adapted to be inserted into a wall socketor other connection tocouple the ap-_ paratus to the usual 110 volt A. 0. current supply. The terminal I0 is connected through the con ductor-3H to fuse 14 which in turn is connected through conductor l5 to the terminal l5’ of the primary coil [6 of the transformer‘ IT. The other plug terminal H is connected through conductor l8, fuse l9, conductor 20, switch 2| and conductor 22 to the terminal 23 of the primary coil I5. The numeral 24 indicates the secondary coil of the transformer IT. The terminals 25 and 26 of the secondary coil 24 are connected through con ductors 21 and 28 to terminals 21' and‘ 28' of primary coil 29 of the transformer 30. The trans; former 30 is provided with a split secondary coil 3| ‘which is provided with terminals 32, 33 and 34 and which functions to effect a greater.‘ and a lesser degree of stimulation aswill be further described. The majorvportion 0f the Split sec ondary coil 3| is connected to terminals 32 and 33 which in turn are connected respectively to switch terminals 35 and 3B. The terminal 34 of the minor portion of the split secondary coil ' _ In order to energize the magnet53, the button 1! of the push button switch is pressed inwardly thus spreading apart the contact members'l2 and '13, which are connected by conductor 13', until they are in contact with the stationarycon tact members 14 and 15, allowing current to pass through the conductively connected contact members 12 and ‘I3 to thusv complete, the circuit from the power lines 21 and 28- through the coil 6|. 50 . J The ?lament terminals ‘I1 and 18 of a pilot lamp 19 are connected to the conductors 68 and 1'0 so that the lamp remains lighted so long as the instrument is plugged into a source of power and the power switch is turned on. . ' The conductors 4'1v and 5| which are adapted to be ‘connected to the electrodes to furnish the desired stimulation may be bridged by either of two voltmeters which are designated by the nu merals 80 and BL'depending on the setting of blade 45 of switch 38. Of these voltmeters, 8| is for a high range measurement and 80’for a low range. When bridging voltmeter 8| across'the lines 47 and 5|, the connections are through con ductor 45, switch blade 45, conductor 82, volt— meterv 8|, conductor 83 to conductor 5|, and when bridging voltmeter" 80 across the lines 41 and 5| the connections are through conductor 46, switch 3| is connected to the ?xed resistance 31. To place a portion of the ‘secondary coil 3| or the entire secondary coil in' the stimulating blade 45, conductor 84, voltmeter 80, conductor 85 to conductor 5|. » . - > circuit a switch 38 is provided. This switch is of the cam operated type and provided with two Five ?lters, each consisting of a condenser‘ and blades 45 and 44 whichareadapted to contact 70 a resistance are used to filter out high frequency currents which may be picked up by the line: from simultaneously. either the terminals 36 and 39, or terminals 35 and 40. ' , t v a‘ ' generators, X-ray, radio apparatus, and similar; sources of interference. Filter. 83, consisting of Thev ?xed resistance 31. is connected between the terminal 34 of the secondary coil, 3| andthe 7 . resistance 81 and condenser 88, is inserted in the‘ terminal 4| of a variable‘ resistance 42 of a'rheo 5, return line designated’ by the numerals 89 and 2,410,499 5 6 99; ?lter 9|, consisting of resistance 92 and con denser 93, is inserted between conductor I5 and conductor 90; and ?lter 9Q, consisting of re sistance 95 and condenser 96, is inserted between tively connecting said output circuit with groups of secondary coils of said output transformer, meters for measuring high and low range volt conductors 22 and 99. Filters are also inserted in the output circuit in proximity to the stimu lating electrodes and the relay. Filter 91, con sisting of resistance 98 and condenser 99, bridges ages bridging said coil groups, a switch circuit connected with said transformer circuit,’ an elec-. tromagnetic switch and a manually operated switch included in said output circuit adapted to , control the operation of said electrodes. 2. A stimulator of the class described compris conductors 67 and 5|, it being connected to con ductor 91 by conductor I09, and ?lter Iill, which 10 ing an input circuit, high frequency ?ltering means associated with said input circuit and comprises resistance I02 and condenser I133, is means for connecting said circuit to a source of inserted between conductors II‘! and I09, the latter alternating current . of predetermined voltage, being connected to conductor 6?. The foregoing wave form, and frequency, having one side resistances along with resistances 56' and 51” provide a leakage path for dissipation of static 15 grounded, a transformer circuit including input charges so that such charges cannot collect on the electrodes. A foot switch (not shown) may also be used ' to control the circuit of the electrodes. Termi nals I64 and I05 for connection of a foot switch are therefore provided. The apparatus is contained within a casing and output transformers provided with primary and secondary coils, an output circuit, high fre quency ?ltering means associated with said out put circuit, applicator electrodes included in said circuit, a switch circuit connected to said trans former circuit,'a two-way switch connected to said output circuit, said switch adapted to se lectively connect said output circuit with groups I06 which is'divided into a main central com~ of secondary ‘coils of said output transformer, a partment It? and two small side compartments I98 and I69 which are provided for retention of 25 high frequency ?lter associated with said switch circuit, meters for measuring high and low range the input and electrode conductors l3 and I8, voltages bridging said coil groups, an electro and 56 and 51, respectively. The various ele magnetic switch, and a manually operated switch ments of the apparatus are attached either to included in said output circuit adapted to control an upper panel H9, a lower panel II I or the side theo-peration of said electrodes. walls H2 and H3 which, with the lower panel 3. A stimulator of the class described compris and the front and a side wall of the casing, form ing an input circuit, high frequency ?lters asso a small insulated compartment to enclose the ciated with said input circuit and means for con fuses I4 and I9, power switch 2|, and ?lters 9i necting said circuit to a source of alternating and 84. The spaced upper and lower panels H9 current of predetermined voltage, wave form, and and I I I, as shown in Fig. 3, provide for the better frequency, a transformer circuit including an in arrangement and protection of the wiring be put transformer provided with a primary and a tween the various parts of the apparatus. secondary coil and an output transformer pro The casing or cabinet is provided with a hinged vided with a primary and a split secondary coil, lid, a carrying handle, and locks so that the ap said split secondary coil being adapted to provide paratus may be readily transported and pro tected. ' ' Having thus described our invention,‘ what we claim as new and wish to secure by Letters Pat ent is: 1. A stimulator of the class described compris ing an input circuit, high frequency ?lters asso ciated with said input circuit and means for connecting said circuit to a source of alternating current of predetermined voltage, wave form, and frequency, having one side grounded, a trans former circuit including input and output trans formers provided with primary and secondary coils, an output circuit, high frequency ?lters as sociated with said output circuit, applicator elec trodes included in said circuit, means for selec a greater and a lesser degree of stimulation, an output circuit, high frequency ?lters associated with said output circuit, applicator electrodes in cluded in said circuit, means for selectively con necting said'output circuit with groups of sec ondary coils of said output transformer, meters for measuring high and. low range voltages bridg ing said coil groups, a switch circuit connected with said transformer circuit, an electromagnetic switch and a manually operated switch included in said output circuit adapted to control the op eration of said electrodes. 1 JOSEPH C. I-HNSEY. WILLIAM A. GEOHEGAN.