U.S. patent number 3,631,542 [Application Number 04/848,919] was granted by the patent office on 1972-01-04 for myoelectric brace.
This patent grant is currently assigned to Iowa State University Research Foundation. Invention is credited to Allan G. Potter.
United States Patent |
3,631,542 |
Potter |
January 4, 1972 |
MYOELECTRIC BRACE
Abstract
A myoelectric brace consisting of a fixed wrist-hand splint
portion having a movable finger support portion pivotally secured
thereto which is operated by a hydraulic actuator. The actuator is
hydraulically coupled to a pump which is driven by a battery
powered, direct current motor. Three skin electrodes are positioned
on the patient's arm and sense muscle potentials in the patient's
arm when the patient tenses a muscle in the immediate area of the
skin electrodes. The resulting myo-potentials are then amplified by
a muscle potential amplifier and are transformed into a slowly
varying control signal by a detector circuit and a filter circuit.
The control signal enters a differential amplifier where it causes
the motor to drive the hydraulic pump until a predetermined
pressure is reached. Actuation of the hydraulic pump causes the
hydraulic actuator to pivotally move the finger support towards the
fixed splint portion. The motor stops when the differential
amplifier receives a signal from the pressure transducer equal in
amplitude to the control signal. This causes the differential
amplifier output signal to go to zero. Relaxation of the patient's
muscle causes the finger support to pivotally move away from the
fixed splint portion.
Inventors: |
Potter; Allan G. (Ames,
IA) |
Assignee: |
Iowa State University Research
Foundation (Ames, IA)
|
Family
ID: |
25304621 |
Appl.
No.: |
04/848,919 |
Filed: |
August 11, 1969 |
Current U.S.
Class: |
623/25; 601/40;
602/21; 623/26 |
Current CPC
Class: |
A61F
2/72 (20130101); B25J 9/0006 (20130101); A61F
5/013 (20130101); A61F 2002/5075 (20130101); A61F
2002/701 (20130101); A61F 2002/741 (20130101); A61F
2002/745 (20130101); A61F 2002/748 (20130101) |
Current International
Class: |
B25J
9/00 (20060101); A61F 2/72 (20060101); A61F
2/50 (20060101); A61F 5/01 (20060101); A61f
001/00 (); A61f 005/10 () |
Field of
Search: |
;3/1-1.2 ;128/26,77 |
Foreign Patent Documents
Other References
"Myo-Electric Control of Powered Prostheses" by A. H. Bottomley,
The Journal of Bone & Joint Surgery, Vol. 47B, No. 3, Aug.
1965, pp. 411-415 .
"Gas-Powered Sources and Actuators for Prosthetic and Orthotic
Devices" by J. R. Pearson, The Control of External Power in
Upper-Extremity Rehabilitation, Nat. Academy of Sciences-Nat.
Research Council, Wash., D.C., 1966, pp. 196-197 (FIG. 5) .
"Myoelectric Control Systems" by W. Waring et al., Orthopedic &
Prosthetic Appl. Journal, Vol. 21, No. 1, Mar. 1967, pp. 27-32
.
"Myo-Electrically Controlled Electric Torque Motor for the Flexor
Hinge Hand Splint" by C. Trombley et al., Orthopedic &
Prosthetic Appliance Journal, Vol. 21, No. 1, Mar. 1967, pp.
39-43.
|
Primary Examiner: Gaudet; Richard A.
Assistant Examiner: Frinks; Ronald L.
Claims
I claim:
1. In a myoelectric brace, comprising,
a splint means adapted to be secured to a person's arm and having a
fixed wrist-hand splint portion and a movable finger support means
pivotally connected thereto,
a hydraulic actuator means mounted on said fixed wrist-hand splint
portion and being connected to said movable finger support means to
cause said finger support means to be moved with respect to said
fixed splint portion,
a hydraulic pump means fluidly connected to said actuator means
adapted to cause said actuator means to move said finger support
means,
a motor means for operating said pump means,
an electrode means adapted to be placed on the wearer's skin
surface adjacent a muscle capable of being tensed by the
wearer,
a circuit means connected to said electrode means adapted to sense
the myo-potentials created by the tensing of said muscle and to
transform the potentials into a control signal whereby said
electric motor, said pump and said actuator will be operated so
that said finger support means will be moved towards said fixed
splint means, and
said pump means including a hollow piston head housing having a
fluid compartment provided therein, said fluid compartment being in
fluid communication with said actuator means, a cylinder housing
connected to said piston head housing, a bellowfram between said
piston head housing and said cylinder housing, a piston means in
said cylinder housing connected to said bellowfram for movement
therewith, a ball bearing screw rotatably mounted in said cylinder
housing, a screw nut operatively connected to said piston means in
engagement with said screw whereby rotation of said screw will
cause said piston and said bellowfram to be moved, said motor
having a drive shaft connected to said screw.
2. The brace of claim 1 wherein a pressure transducer is in
communication with said fluid compartment in said piston head
housing, said pressure transducer being electrically connected to
said circuit means to stop said motor when a predetermined pressure
is reached in said fluid compartment.
Description
Electrically powered orthotic devices or braces for quadraplegic
patients are convenient because the electrical power is readily
available and is easily stored in the batteries which drive the
electric motors on wheel chairs used by such patients. The
utilization of other types of energy storage techniques by these
patients requires the handling of another source of energy and
thus, another set of operating conditions which is highly
undesirable. In order to utilize the electrical energy stored in
the wheel chair batteries to effectively power orthotic devices,
one must optimize several conflicting requirements. First, both the
weight and size of the brace-mounted actuator must be small.
Second, the response and control of the limb brace when driven by
the actuator must be normal. Third, minimum size, weight, and power
consumption is desired for the complete device.
Therefore, it is a principal object of this invention to provide a
myoelectric brace for quadraplegic patients.
A further object of this invention is to provide a myoelectric
brace which is powered by a unique hydraulic system driven by a
direct current battery operated motor.
A further object of this invention is to provide a myoelectric
brace which is light weight.
A further object of this invention is to provide a myoelectric
brace which has a minimum size and consumes a minimum of power.
A further object of this invention is to provide a myoelectric
brace which is operated by the muscle potentials in the patient's
arm.
A further object of this invention is to provide a myoelectric
brace wherein muscle potentials are sensed by surface electrodes
and are used to control finger position and tension in a
proportional manner.
A further object of this invention is to provide a method of
actuating a myoelectric brace.
A further object of this invention is to provide a myoelectric
brace which is economical of manufacture, durable in use and
refined in appearance.
These and other objects will be apparent to those skilled in the
art.
This invention consists in the construction, arrangements, and
combination of the various parts of the device, whereby the objects
contemplated are attained as hereinafter more fully set forth,
specifically pointed out in the claims, and illustrated in the
accompanying drawings in which:
FIG. 1 is a side elevational view of the brace mounted on the
patient's arm;
FIG. 2 is a top view of the brace as seen along lines 2--2 of FIG.
1;
FIG. 3 is a longitudinal sectional view of the hydraulic actuator
as seen along lines 3--3 of FIG. 1;
FIG. 4 is a fragmentary longitudinal sectional view of the
hydraulic pump as seen along lines 4--4 of FIG. 1;
FIG. 5 is a block diagram of the electrical circuitry of this
invention; and
FIG. 6 is a schematic view of the electrical circuitry of this
invention.
The numeral 10 generally designates a fixed wrist-hand splint of
this invention which is adapted to be secured to the patient's
lower arm, wrist and hand. Splint 10 includes a splint portion 12
which is secured to the patient's arm 14 by a strap 16 extending
therearound and selectively closed by a Velcro fastener means 18
(FIG. 1). The upper end of splint portion 20 is pivotally connected
to the lower end of splint portion 12 by a pin 22. Thumb support 24
extends downwardly from one end of splint portion 20 and is adapted
to have the patient's thumb received therein (FIG. 1). A curved
support 26 is pivotally secured at its upper end to splint portion
20 by a pin 28 and has spaced-apart, finger supports 30 and 32
extending laterally therefrom. As seen in FIG. 1, finger support 30
is adapted to have the patient's fingers extending therethrough
while finger support 32 is adapted to extend over the patient's
fingers. An arcuate hand support 34 is secured to splint portion 20
and extends laterally therefrom adapted to cup or support the
underside of the patient's hand. Strap 36 extends around the
patient's hand to firmly maintain the device thereon.
A hydraulic actuator 38 is secured to splint portion 20 by bracket
40 and has a push rod 42 slidably extending therefrom which is
pivotally secured by a pin 44 to one of the adjustment holes 46
formed in ear 48 which extends from the rearward end of support 26.
Thus, extension of push rod 42 from the hydraulic actuator 38
causes support 26 to pivot towards thumb support 24. Conversely,
the withdrawal of push rod 42 into the actuator 38 causes support
26 to pivot away from the thumb support 24.
Hydraulic actuator 38 includes a piston head portion 50 secured to
cylinder housing 52 by head screws 54. A bellowfram 56 is
positioned between piston head portion 50 and cylinder housing 52
as seen in FIG. 3. A U-shaped piston 58 is secured to bellowfram 56
by a piston cap screw 60 extending through piston cap 62,
bellowfram 56 and into piston 58.
Push rod 42 is secured to piston 58 and extends through spaced
apart ball bushings 64 and 66 to reduce friction. A helical
compression spring 68 embraces push rod 42 between piston 58 and
support 70 and yieldably resists the extension of push rod 42 from
housing 52. Nipple 72 extends from piston head portion 50 and is
adapted to have a fluid line 74 connected thereto to place the
fluid chamber 76 in actuator 38 in communication with pump 78. Pump
78 includes a hollow piston head 80 having a nipple 82 extending
therefrom adapted to receive the fluid line 74 thereon. Pump 78
includes a fluid chamber 84 having a pressure transducer 86
extending thereinto. Pressure transducer 86 is provided with an
electrical lead 88 which extends to a differential amplifier which
will be discussed hereinafter.
A bellowfram 90 is positioned between piston head 80 and cylinder
housing 92 by means of cap screws 94. A U-shaped piston 96 is
secured to the center of bellowfram 90 by cap screws 98 extending
through cap 100, bellowfram 90 and into piston 96.
The other end of piston 96 has an end plate 104 secured thereto
which bears against the ball bearing screw nut 102 which runs in a
groove of a grooved helical screw 116. Screw 116 is secured to the
drive shaft 105 which rotatably extends from a battery operated,
direct current motor 106. The numeral 108 refers to a coupling
housing positioned between motor 106 and housing 92 and maintained
therebetween by screws 110. An oldham coupling 120 connects motor
106 to screw 116.
Energization of the motor 106 causes power shaft 105 to rotate ball
bearing screw 116. The rotation of screw 116 causes screw nut 102
to be moved along the groove of the screw 116 to cause spring 118
to drive piston 96 to the right as viewed in FIG. 4. Movement of
piston 96 to the right causes the fluid in chamber 84 to be forced
therefrom, through line 74 and into the fluid compartment of
actuator 38. The fluid entering fluid compartment 76 in actuator 38
causes piston 58 to be moved to the left, as viewed in FIG. 3,
which causes push rod 42 to be extended from the actuator 38 which
in turn causes support 26, and hence the patient's fingers, to be
moved towards the thumb support 24.
The numerals 112, 114 and 116 refer to the skin electrodes which
are placed adjacent the skin surface of the patient's arm as
indicated in FIG. 1 and maintained thereon by suitable means such
as tape or the like. The electrodes are connected to a muscle
potential amplifier generally referred to by the reference numeral
118 in FIGS. 5 and 6. If the patient desires to close his fingers,
he tenses a muscle located near the skin surface electrodes. The
resulting muscle potentials are then amplified by the muscle
potential amplifier 118. This amplifier, FIG. 6, consists of a pair
of operational amplifiers in a unity gain to common mode type
circuit followed by a differential amplifier circuit, a parallel
"T" rejection filter circuit, and a Darlington amplifier circuit.
The amplified myopotentials are then put into a detector circuit
120, consisting of a Schmidt trigger circuit followed by a low-pass
filter circuit. This detector circuit transforms the amplified
muscle potentials into a slowly varying control signal whose
amplitude is related to the muscle tension causing it. If the
output of the differential amplifier 124 is sufficiently large the
motor control circuit 126 causes the motor 106 to drive the
hydraulic pump 78 until a pressure related to the desired finger
position plus tension is reached. The motor control circuit
contains two identical control circuits consisting of a relaxation
oscillator circuit which drives a hybrid timing circuit and a
transistor bridge circuit. In this way both clockwise and
counterclockwise rotation can be obtained depending upon which
control circuit drives the transistor bridge circuit. The motor 106
stops when the signal from the pressure transducer 86 causes the
differential amplifier 124 output signal to go below a set
threshold level. If the patient wishes to open his fingers, he
simply relaxes and the signal from the pressure transducer 86
causes the motor 106 to reduce the pressure so that the brace is
driven to its zero muscle voltage position by the spring 68
contained in the actuator 38.
In summary, it can be seen that the myoelectric brace is driven by
muscle potentials. The muscle potentials are created by tensing or
contracting of the muscle which causes polarization of the muscle.
The electrodes on the skin detect the E.M.G. differential and
relays the same to the circuitry illustrated in the drawings. The
pump 78 and actuator 38 are especially designed to reduce friction
through the use of the ball bushings 64 and 66 and through the use
of the foldable bellowfram incorporated therein.
A brace has been provided which is lightweight and which requires a
minimum of power to be consumed during the operation thereof. The
size of the brace is relatively small and is conveniently secured
to the patient's arm. Finger position and tension is controlled in
a proportional manner due to the muscle potentials being sensed by
the surface electrodes and the relationship of the pressure
transducer to the motor control circuit.
Thus it can be seen that the device accomplishes at least all of
its stated objectives.
* * * * *