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Nov. 5, 1946. ‘
_ 2,410,499 '
Filed May 16, 1945'
5 Sheets-Sheet 1
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Nov; 5, 1946.
Filed May 16, 1945
3 Sheets-Sheet 3
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Patented Nov. 5, 1946
'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),
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
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;
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
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‘
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
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|.
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
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
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
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.
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