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BACKGROUND OF THE INVENTION
The present invention relates generally to the field of electrical
neuromuscular stimulation for the treatment of incontinence. In
particular, the present invention is a method of construction for a solid,
molded electrode having increased effectiveness.
Electrical neuromuscular stimulation is widely used to assist persons
afflicted with motor dysfunctions in performing muscle contraction
maneuvers. Motor nerve fibers are electrically stimulated by means of
transcutaneously applied pulses of electrical current to cause
contractions of the innervated muscles. This technique is also used to
re-educate patients in the proper use of dysfunctional muscles.
For example, in cases in which urinary incontinence in women is caused by
the patient's inability to properly contract the external sphincter of the
urethra, it has been shown that neuromuscular stimulation of the
dysfunctional muscles by means of a vaginal electrode can effectively
prevent the unwanted flow of urine. By use of such an electrode, some
patients can educate themselves to voluntarily or automatically impede the
flow of urine.
A more important application of pelvic force stimulation is the exercise
and toning of the muscles of the pelvic floor which support the bladder,
the vagina, urethra and other organs. Muscles which have become lax or
stretched through the process of child birth or natural aging, can be
strengthened and tightened to properly support these structures, thus
positively affecting the patient's ability to maintain continence.
Electrical stimulators for controlling incontinence generally include a
plug with one or more electrodes in the form of conductive metal rings or
polymer bands. A wire harness, including connector pins and lead wires,
extends from the plug to a controller or stimulator which generates
stimulation signals. The controller is usually worn externally, attached
to the user's clothing.
There is a continuing need for a lightweight, flexible device which can
re-train the dysfunctional muscles responsible for incontinence. In
addition to being effective, the stimulator must be durable, hygienic and
inexpensive to manufacture.
SUMMARY OF THE INVENTION
The present invention is an improved method of manufacturing a solid, yet
flexible, electrode adapted for insertion into a body cavity for
stimulating and constricting the muscles adjacent the cavity, in order to
retrain the muscles and prevent incontinence. An electrode made in
accordance with the method of the present invention includes an elongated
contoured body, handle and bulbous end molded from a relatively compliant
non-conductive polymer. The elongated body includes a plurality of
conductive sections which are formed from a conductive polymer. The
conductive sections are spaced along a longitudinal axis of the elongated
body. Electrical connectors may be molded with or inserted into each
conductive section to form a secure and durable mechanical/electrical
connection.
The method of the present invention includes forming a skeleton of
conductive sections, connector pins and lead wires. The conductive
sections are made by molding a conductive polymer to define an annular
shape and include a pin receptacle. An electrical connector pin and its
corresponding lead wire is positioned within the receptacle. The resulting
skeleton of conductive sections, connector pins and lead wires is placed
in a mold which defines the general shape of the electrode. A
non-conductive polymer is then molded to the skeleton to form an integral
electrode.
In a first embodiment of the method of the present invention, forming the
skeleton includes molding each conductive section and then inserting an
electrical connector pin and corresponding lead wire into an appropriate
receptacle in each conductive section.
In a second embodiment of the method of the present invention, forming the
skeleton includes molding the connector pins and lead wires into the
conductive sections. More particularly, the wire harness (i.e. the
connector pins and corresponding lead wires) is positioned within the mold
for the conductive sections. As each conductive section is molded, the
conductive polymer surrounds the electrical components so that the result
is the skeleton of conductive sections, connector pins and lead wires.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a side view of an electrode made in accordance with the method
of the present invention.
FIG. 1A is a cross-sectional view of the electrode taken along line A--A of
FIG. 1.
FIG. 1B is a cross-sectional view of the electrode taken along line B--B of
FIG. 1.
FIG. 1C is a cross-sectional view of the electrode taken along line C--C of
FIG. 1.
FIG. 2 shows the steps of the first embodiment of the method of the present
invention.
FIG. 3 shows the steps of the second embodiment of the method of the
present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 is a side view of a preferred embodiment of an electrode made in
accordance with the methods of the present invention. Electrode 10 is used
for muscle stimulation within a body cavity and generally includes
elongated contoured body 12, handle 14, electrical wire harness 16 and
electrical stimulation controller 18. Elongated body 12 includes first
conductive section 20, second conductive section 22, third conductive
section 24, non-conductive sections 26 and 28 and bulbous end 32, all of
which are longitudinally spaced along axis X.sub.1.
Wire harness 16 extends from sleeve 15 of handle 14 and delivers leads
L.sub.1, L.sub.2 and L.sub.3 to elongated body 12 of electrode 10. Each
lead wire is attached to a pin connector by any acceptable manner, such as
crimping and/or soldering. Pin connectors P.sub.1, P.sub.2, and P.sub.3
are formed of metal, such as gold coated brass.
Also shown are an inner diameter D.sub.1 of 0.250 inches, an outer diameter
D.sub.2 of 0.500 inches and an end diameter D.sub.3 of approximately 0.750
inches. The overall length of electrode 10, measured along axis X.sub.1
from sleeve 15 to bulbous end 32, is approximately 2.5 to 3.0 inches.
Elongated body 12 has an hourglass-like shape with outer surface 30 being
radially tapered through regions 22, 24 and 28. Body 12 has a narrow waist
region (i.e. non-conductive section 28) having a minimum diameter of 0.265
inches. Elongated body 12 is contoured to provide bulbous end 32, which
facilitates a traumatic insertion of electrode 10 within a body cavity.
When electrode 10 is positioned within a body cavity adjacent the
dysfunctional muscles, electrical current from controller 18 is delivered
to conductive sections 20, 22 and 24 via wire harness 16. This electrical
current induces the muscles to contract causing the surrounding muscles to
bear down on body 12 in a non-uniform manner so as to conform to the
hourglass shape of exterior surface 30. The hourglass (i.e. contoured)
shape of body 12 thereby aids in maintaining electrode 10 in a desired
location.
FIG. 1A shows a cross-sectional view of electrode 10 taken along line A--A
of FIG. 1. Connector pin P.sub.1, its accompanying lead wire L.sub.1 and
lead wires L.sub.2 and L.sub.3 are shown positioned within pin receptacle
40 and wire receptacle 42, respectively in conductive section 20. More
particularly, lead L.sub.1 extends from connector pin P.sub.1. Lead wires
L.sub.2 and L.sub.3, are connected to pins P.sub.2 and P.sub.3 (not
shown), respectively.
In this embodiment, lead wires L.sub.1 and L.sub.2 are positioned below
connector pin P.sub.1. The location of the lead wires and connector pins,
however, is dependent upon the position of the receptacles in the
conductive sections. Each receptacle has a longitudinal axis parallel to
longitudinal axis X.sub.1 of elongated body 12. Pin receptacle 40 is
directly above wire receptacle 42. However, the pin and wire receptacles
may be in any configuration which allows each pin receptacle to be in
communication with each wire receptacle in the same conductive section.
Solid line 32 represents outer diameter D.sub.2 of electrode 10 while
solid line 34 is end diameter D.sub.3 which is defined by bulbous end 32.
FIG. 1B shows a cross-sectional view of electrode 10 taken along line B--B
of FIG. 1. In this view, connector pin P.sub.2 and lead wires L.sub.2 and
L .sub.3 are shown within second conductive section 22. Lead wire L.sub.2
extends from connector pin P.sub.2 while lead wire L.sub.3 is shown
positioned below pin P.sub.2. As shown in the figure, pin P.sub.2 is press
fit within pin receptacle 44 and wire L.sub.3 is positioned within wire
receptacle 46. Receptacles 44 and 46 must be in communication with each
other. As in the previous figure, solid line 32 is outer diameter D.sub.2
and solid line 34 is end diameter D.sub.3 of electrode 10.
FIG. 1C shows a cross-sectional view of electrode 10 taken along line C--C
of FIG. 1. Connector pin P.sub.3 and lead wire L.sub.3 are shown press fit
within pin receptacle 48 in third conductive section 24. Lead wire L.sub.3
extends from connector pin P.sub.3. Also shown is solid line 32
representing outer diameter D.sub.2 and solid line 34 which is end
diameter D.sub.3. L.sub.3 extends from connector pin P.sub.3. Also shown
is solid line 32 representing outer diameter D.sub.2 and solid line 34
which is end diameter D.sub.3.
FIG. 2 shows the steps of a first embodiment of the method for
manufacturing electrode 10 in accordance with the present invention.
In step 40, first conductive section 20, second conductive section 22 and
third conductive 24 are molded. In this embodiment of the method, the
conductive sections are formed by injecting a medical grade thermoset
conductive polymer, such as Rhodorsil RS 1316, into molds which define the
shape of each conductive section. The conductive sections are injection
molded (or molded by any acceptable processing technique) at a temperature
of 350.degree. F. and then post cured for approximately 16 hours, so that
the annular shape of the conductive section may be retained. The resulting
conductive sections 20, 22 and 24 have a durometer of 65 shore A and a
volume resistivity of approximately 5.5 ohm-cm. Although, the diameter of
second conductive section 22 and third conductive section 24 may vary
because these sections are tapered to produce the hourglass-like shape of
elongated body 12, the greatest diameter of any molded conductive section
is approximately 0.500-0.600 inches.
Each conductive section includes a pin receptacle. First conductive section
20 and second conductive section 22 also include wire receptacles. The
dimensions of the pin receptacle and the wire receptacle, however, may
change in accordance with the brand of the electrical component used. In
this embodiment, the mold for first conductive section 20 defines a pin
receptacle 40 having a diameter of 0.076 inches. A smaller elliptical wire
receptacle 42 has a major axis of 0.04 inches and minor axis of 0.020
inches. Receptacles 40 and 42 receive connector pin P.sub.1 /lead wire
L.sub.1 and lead wires L.sub.2 and L.sub.3, respectively. Receptacle 40
opens into
The mold for second conductive section 24 includes pin receptacle 44 and
wire receptacle 46. However, wire receptacle 46 receives only one wire
(L.sub.3) in conductive section 22. Thus, wire receptacle 46 has a
diameter of 0.020 inches in second conductive section 24. Pin receptacle
44 has the same diameter as pin receptacle 40. As in first conductive
section 20, receptacles 44 and 46 are arranged so that they are in
communication with each other (see FIG. 1B):
The mold for third conductive section 24 includes a single blind or through
pin receptacle 48 having a diameter of 0.076 inches. Pin receptacle 48
receives connector pin P.sub.3 and its accompanying lead wire L.sub.3.
(see FIG. 1C).
In step 42, connector pins P.sub.1, P.sub.2, and P.sub.3 and their attached
lead wires L.sub.1, L.sub.2 and L.sub.3, respectively are inserted into
the appropriate receptacles in each conductive section.
Each connector pin has a diameter slightly larger than the diameter of each
pin receptacle. Although each connector pin may still pass through a pin
receptacle when sufficient force is applied in a longitudinal direction,
the larger diameter of the connector pins provides a durable
mechanical/electrical connection between the conductive section and the
connector pin. Thus, despite "stress creep" (elastomeric relaxation) of
the polymer compounds of electrode 10, or flexing of electrode 10 due to
the contractive forces of the surrounding muscles, the insertion of pin
connectors P.sub.1 -P.sub.3 into their respective receptacles provides a
continuous mechanical and electrical contact.
In accordance with step 42, pin P.sub.3 and its attached lead wire L.sub.3
are fed through pin receptacle 40 in first conductive section 20 and pin
receptacle 44 in second conductive section 22 so that pin P.sub.3 may be
permanently inserted into pin receptacle 48 in third conductive section
24.
Upon insertion of pin P.sub.3 into pin receptacle 48, however, lead wire
L.sub.3 is still positioned within pin receptacles 40 and 44. Therefore,
lead wire L.sub.3 must be manually pushed into wire receptacle 42 in first
conductive section 20 and wire receptacle 46 in second conductive section
22 so that it is press fit into the appropriate wire receptacle in first
conductive section 20 and second conductive section 22.
Next, connector pin P.sub.2 and its attached lead wire L.sub.2 are fed
through pin receptacle 40 in first conductive section 20 so that connector
pin P.sub.2 may be permanently inserted into pin receptacle 44 in second
conductive section 22. Upon insertion of pin P.sub.2 into pin receptacle
44, however, lead wire L.sub.2 is still positioned within pin receptacle
40 in first conductive section 20. Therefore, lead wire L.sub.2 must be
manually pushed into wire receptacle 42 in first conductive section 20. In
a final insertion step, connector pin P.sub.1 and its attached lead wire
L.sub.1 are inserted into pin receptacle 40 in first conductive section
20.
In step 44, the skeleton including first conductive section 20, second
conductive section 22, third conductive section 24 and their respective
connector pins/lead wires is positioned within a second mold defining
elongated body 12, handle 14 and bulbous end 32 of electrode 10.
In step 46, a medical grade non-conductive polymer, such as Dow-Corning
Silastic Q-7-4565 combined with a catalyst such as dicumyl peroxide, is
injected (or molded by any acceptable processing technique) into the
second mold in regions which define handle 14 non-conductive sections 26
and 28 and bulbous end 32. Non-conductive sections 26 and 28 are molded to
connect with conductive sections 20, 22 and 24 so that elongated body 12
of electrode 10 is formed. After molding each non-conductive portion,
electrode 10 is cured for approximately 2 hours at 350.degree. F. to
effect the chemical bonding of conductive sections 20, 22 and 24 to
non-conductive sections 26 and 28 and to retain the general shape of
elongated body 12, handle 14 and bulbous end 32. The non-conductive
portions of the electrode have a durometer of about 67 shore A.
FIG. 3 shows the steps of a second method for manufacturing electrode 10 in
accordance with the present invention.
In step 50, wire harness 16 is placed within a first mold which defines
first conductive section 20, second conductive section 22 and third
conductive section 24.
In step 52, a conductive polymer such as Santoprene 199-87 (a thermoplastic
polymer) is used to mold the first, second and third conductive sections.
More particularly, Santoprene is injection molded (or molded by any other
acceptable processing technique) at approximately 375.degree. F. Each
resulting conductive section has a durometer of 87 shore A and a volume
resistivity of 100-200 ohm-cm.
The conductive polymer actually molds around the wire harness such that it
surrounds connector pins P.sub.1, P.sub.2, P.sub.3 and lead wires L.sub.1,
L.sub.2 and L.sub.3 so that receptacles are not required in the conductive
sections. Hence, there is no need to insert electrical components into
each conductive section.
In step 54, the resulting skeleton including first conductive section 20,
second conductive section 22, third conductive section 24 and wire harness
16 is positioned in a second mold which defines elongated body 12, handle
14 and bulbous end 32 of electrode 10.
In step 56, a non-conductive polymer such as thermoplastic Santoprene
281-87 is molded at a temperature between 350.degree.-450.degree. F. into
regions of the second mold which define non-conductive portions of
electrode 10. Non-conductive sections 26 and 28 are molded to connect
first conductive section 20, second conductive section 22 and third
conductive section 24 to form elongated body 12 of electrode 10.
Santoprene 281-87 is also used to mold the regions which define handle 14
and bulbous end 32. Each non-conductive section has a durometer of 87
shore A.
An electrode made in accordance with the method of the present invention
may be of a single or dual durometer. A single durometer electrode implies
that the electrode is made of polymers which have the same durometer and
hence, the same amount of flexibility throughout the electrode. A dual
durometer electrode, however, implies that polymers of differing durometer
are used to fabricate the electrode.
For example, in an alternative embodiment, a non-conductive polymer having
a durometer ranging from 75-87 Shore A may be used to mold the narrow
waist area of the electrode (i.e. non-conductive section 28) while a
non-conductive polymer having a durometer ranging from 65-70 Shore A may
be injected at the bulbous end and handle area of the same electrode. In
this manner, precise bending stiffness is provided at the waist area while
perceived comfort for the patient is enhanced at the bulbous end and
handle area. Other variations of multiple durometer electrodes may be
employed to obtain a desired level of flexibility of the electrode.
The method of the present invention teaches a process for manufacturing a
solid electrode which does not require labor intensive
mechanical/electrical connections. The resulting electrode is a solid, yet
flexible, device which provides reliable neuromuscular stimulation and a
hygienic appearance with prolonged use.
Although the present invention has been described with reference to
preferred embodiments, workers skilled in the art will recognize that
changes may be made in form and detail without departing from the spirit
and scope of the invention.
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