U.S. patent number 4,634,432 [Application Number 06/733,556] was granted by the patent office on 1987-01-06 for introducer sheath assembly.
Invention is credited to Nuri Kocak.
United States Patent |
4,634,432 |
Kocak |
January 6, 1987 |
Introducer sheath assembly
Abstract
An introducer sheath includes a connector body having an inlet
and an outlet; a flexible tube for intravenous use at the outlet,
including a helical coiled spring having a plurality of coils, each
coil spaced from an adjacent coil, and a thin cylindrical wall
prepared from a protective coating composition completely
surrounding the spring to define an inner and an outer wall
surface, the portion of the cylindrical wall surrounding each coil
having a first thickness and the portion of the cylindrical wall
between the spaced coils having a second, smaller thickness, with
the inner and outer wall surfaces being indented thereat, the
coating composition comprising a thermoplastic polymeric material
dissolved in a solvent solution, the composition having a solids
content ranging from about 4% to about 18%, and said solution
comprising a solvent selected from the group consisting of
tetrahydrofuran, dioxane, methyl ethyl ketone, dimethylformamide,
cyclohexane, and mixtures thereof, formed on a helical coiled
spring by dipping the latter therein and then drying at room
temperature; and a valve assembly including a first elastic
membrane having a central aperture, and a second elastic membrane
in sealing contact with the first elastic membrane and having a
slit extending therethrough at an angle to the direction of fluid
flow in the introducer sheath, the slit being in fluid
communication with the central aperture.
Inventors: |
Kocak; Nuri (Cliffside Park,
NJ) |
Family
ID: |
24948118 |
Appl.
No.: |
06/733,556 |
Filed: |
May 13, 1985 |
Current U.S.
Class: |
604/167.04;
137/846; 138/174; 604/526 |
Current CPC
Class: |
A61M
25/005 (20130101); A61M 25/0662 (20130101); A61M
39/0606 (20130101); A61M 2039/062 (20130101); Y10T
137/7882 (20150401); A61M 2039/064 (20130101); A61M
2039/0653 (20130101); A61M 2039/0686 (20130101); A61M
2039/0633 (20130101) |
Current International
Class: |
A61M
25/00 (20060101); A61M 25/06 (20060101); A61M
39/02 (20060101); A61M 39/06 (20060101); A61M
005/00 () |
Field of
Search: |
;604/167,169,280,282
;128/657,658 ;137/845-849 ;138/174 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Pellegrino; Stephen C.
Attorney, Agent or Firm: Jackson; David A.
Claims
What is claimed is:
1. A flexible tube for the introduction of catheters and like
devices into a vascular system, comprising:
a helical coiled spring having a plurality of coils, each of a
plurality of said coils being spaced from at least one adjacent
coil; and
a thin cylindrical wall prepared from a protective coating
composition completely surrounding said spring to define an inner
wall surface and an outer wall surface, the portion of said
cylindrical wall surrounding each of said coils having a first
thickness and the portion of said cylindrical wall between said
spaced coils having a second, smaller thickness, with said inner
and outer wall surfaces being indented thereat;
said coating composition comprising a thermoplastic polymeric
material dissolved in a solvent solution, said composition having a
solids content ranging from about 4% to about 18%, and said
solution comprising a solvent selected from the group consisting of
tetrahydrofuran, dioxane, methyl ethyl ketone, dimethylformamide,
cyclohexane, and mixtures thereof.
2. A flexible tube according to claim 1; wherein said solvent
solution comprises a mixture of dioxane and tetrahydrofuran in a
relative ratio ranging from 1:9 to 6:4 by weight.
3. A flexible tube according to claim 2; wherein said relative
ratio is 1:1.
4. A flexible tube according to claim 1; wherein said polymeric
material is selected from the group consisting of polyurethane,
polyvinyl chloride, latex and silicone.
5. A flexible tube according to claim 1; wherein said composition
has a solids content of 10%.
6. A flexible tube according to claim 1; wherein said polymeric
material is a solid material having a Shore A hardness rating
ranging from about 70 to about 95.
7. A flexible tube according to claim 1; wherein the number of
coils per inch is not greater than 200.
8. A flexible tube according to claim 1; wherein the first
thickness of said cylinder is at least as small as 0.005 inch.
9. A flexible tube according to claim 1; wherein said cylindrical
wall further includes a thromboresistant coating on at least one of
its surfaces.
10. A flexible tube according to claim 9; wherein said
thromboresistant coating is a polyvinylpyrrolidone-polyurethane
interpolymer.
11. In an introducer sheath valve assembly, the improvement
comprising:
a first elastic membrane having a first exterior surface, a first
interior surface and an aperture extending between said first
exterior and interior surfaces; and
a second elastic membrane having a second exterior surface in
sealing contact with said first interior surface of said first
elastic membrane, a second interior surface, and a slit extending
between said second exterior and interior surfaces at an angle to
the direction of fluid flow in said introducer sheath, said slit
being in fluid communication with said aperture.
12. A valve assembly according to claim 11; wherein said aperture
converges from said first exterior surface toward said first
interior surface.
13. A valve assembly according to claim 11; wherein said aperture
is centrally positioned within said first elastic membrane.
14. A valve assembly according to claim 11; wherein said first
elastic membrane has a circular configuration, and includes an
interiorly directed circumferential flange.
15. A valve assembly according to claim 14; wherein said second
elastic membrane has a circular configuration with a circular end
wall, and is positioned within said flange such that said end wall
is in sealing contact with said flange.
16. A valve assembly according to claim 14; wherein said flange is
spaced inwardly along said first interior surface.
17. An introducer sheath comprising:
connector means having opposite ends, one of said ends defining a
first inlet and the other end defining an outlet, an opening
extending end to end therethrough to fluidly connect said first
inlet and said outlet, and a second inlet in fluid communication
with said opening;
a flexible tube fluidly connected to said outlet, said flexible
tube including a helical coiled spring having a plurality of coils,
each of a plurality of said coils being spaced from at least one
adjacent coil, and a thin cylindrical wall prepared from a
protective coating composition completely surrounding said spring
to define an inner wall surface and an outer wall surface, the
portion of said cylindrical wall surrounding each of said coils
having a first thickness and the portion of said cylindrical wall
between said spaced coils having a second, smaller thickness, with
said inner and outer wall surfaces being indented thereat, said
coating composition comprising a thermoplastic polymeric material
dissolved in a solvent solution, said composition having a solids
content ranging from about 4% to about 18%, and said solution
comprising a solvent selected from the group consisting of
tetrahydrofuran, dioxane, methyl ethyl ketone, dimethylformamide,
cyclohexane and mixtures thereof; and
a valve assembly mounted at said first inlet, said valve assembly
including a first elastic membrane having a first exterior surface,
a first interior surface and an aperture extending between said
first exterior and interior surfaces, and a second elastic membrane
having a second exterior surface in sealing contact with said first
interior surface of said first elastic membrane, a second interior
surface, and a slit extending between said second exterior and
interior surfaces at an angle from the direction of fluid flow in
said introducer sheath, said slit being in fluid communication with
said opening and said aperture.
18. An introducer sheath according to claim 17; wherein said
solvent solution includes dioxane and tetrahydrofuran in a relative
ratio ranging from 1:9 to 6:4 by weight.
19. An introducer sheath according to claim 18; wherein said
relative ratio is 1:1.
20. An introducer sheath according to claim 17; wherein said
polymeric material is selected from the group consisting of
polyurethane, polyvinyl chloride, latex and silicone.
21. An introducer sheath according to claim 17; wherein said
aperture converges from said first exterior surface toward said
first interior surface and is centrally positioned within said
first elastic membrane.
Description
BACKGROUND OF THE INVENTION
The present invention relates generally to introducer sheaths and,
more particularly, to a novel intravenous tube and valve assembly
for use therewith.
It is well known to medically treat a patient by intravenously
introducing fluids into an artery or vein. In this regard, an
introducer sheath or hemostasis cannula assembly is generally
provided, for example, similar to that disclosed in U.S. Pat. No.
4,000,739. As shown and described in this patent, the main body
portion of the assembly has a tapered portion at the outlet side
thereof within which is positioned a length of flexible tubing. The
catheter is inserted into the assembly through the gasket assembly
at the inlet side of the main body, whereby the gasket assembly
provides a fluid-tight seal. After the catheter is in position,
fluid may be injected through the catheter into the vascular system
for treatment of the patient.
A problem with conventional flexible tubes used with introducer
sheath assemblies is that the tube walls tend to collapse or kink
when flexed, such as may occur when the patient moves, and flow
reduction or stoppage may result. Recent developments have
attempted to overcome this problem by utilizing a helical coiled
spring as part of the flexible tube, for example, as shown in U.S.
Pat. Nos. 3,618,613; 3,841,308; 3,963,856; 4,044,765; 4,052,989;
4,068,660; and 4,368,730. For related, but less relevant subject
matter, see also U.S. Pat. Nos. 2,437,542; 2,472,483; 4,362,163;
and 4,425,919. Generally, however, the formation of such inert
plastic tubing with the helical coiled spring requires either that
the plastic be heat shrunk or heat bonded to the spring or force
fit with respect thereto. The problem with using a force fit or
extrusion coating method is that, if the wire of the spring has an
extremely small diameter, which is generally necessary, it cannot
withstand the forces applied during such methods. In addition, the
use of heat to cure the plastic material could not be used with a
plastic spring since the coil itself would melt. Accordingly, it is
generally necessary to provide relatively large gauge coils,
thereby reducing the density of the coils and the kink resistance
properties.
U.S. Pat. No. 4,044,765 discloses an outer tubular sheath formed of
a heat-shrinkable material, while an inner coating or lining is
deposited by a solution, emulsion or dispersion of the same type of
inert plastic as that used for the outer sheath and which is dried
or cured by heating the entire unit to about 250.degree. F. for
about 10 minutes. The outer sheath, however, is still necessary in
this patent for the purpose of forming a base on which the inner
coating or lining can be formed. This patent also suffers from the
deficiencies aforementioned since the solution must be cured by
heating.
Although U.S. Pat. No. 3,618,613 does disclose curing by air
drying, the patent still requires the use of an inner tubing to
provide a base on which the outer coating can be formed. This
results in force fitting of the spring over the inner tubing, which
suffers from the disadvantages of providing undue forces on the
spring and which also greatly increases the wall thickness, thereby
lessening the kink resistance properties.
With respect to known hemostasis valves, U.S. Pat. No. 4,000,739
provides a pair of juxtaposed flexible gaskets mounted in the
posterior end of the main body of the introducer sheath. The
exteriorly positioned gasket of the pair is provided with a central
opening which forms a seal around the catheter inserted
therethrough, and the second interiorly positioned gasket is
provided with a "Y" slit, the center of which is aligned with the
axis of the central opening of the first gasket. The second gasket
is compressed against the first gasket to seal the passage when the
catheter is removed. A problem with such "Y" slit arrangement is
that the slit extends through the second gasket generally in line
with the longitudinal axis of the introducer sheath. As a result,
when the catheter is inserted therethrough, back pressure from
fluid within the introducer sheath may leak out through the slit;
that is, the gaskets often do not form a complete seal against
blood loss. See also U.S. Pat. No. 4,430,081. Other patents which
are less relevant are U.S. Pat. Nos. 584,091; 3,620,500; 4,342,315;
4,405,316; 4,405,320; and 4,468,224.
U.S. Pat. No. 4,436,519 discloses an arrangement in which a single
slit at the apex of a hemispherical projection of a gasket is
provided through which the catheter is inserted. Because of the
hemispherical outer surface of the projection, fluid back pressure
tends to close the slit around the catheter and provide a
fluid-tight seal. However, such construction is relatively
complicated and also requires the use of reinforcing ribs about the
hemispherical projection which further complicates the
construction.
OBJECTS AND SUMMARY OF THE INVENTION
Accordingly it is an object of the present invention to provide an
introducer sheath having a flexible tube for intravenous use which
is kink resistant and crush resistant, without increasing the
resistance to bending.
It is another object of the present invention to provide an
introducer sheath having a flexible tube which has a resistance to
linear compression.
It is still another object of the present invention to provide an
introducer sheath having a flexible tube formed with a helical
coiled spring surrounded by a protective coating, with the number
of reinforcing coils per inch of tubing length being as high as
200.
It is yet another object of the present invention to provide an
introducer sheath having a flexible tube formed with a helical
coiled spring and a protective coating defining a cylindrical wall
completely surrounding the spring, with a wall thickness as little
as 0.005 inch, regardless of the diameter of the tube.
It is a further object of the present invention to provide an
introducer sheath having a flexible tube formed by dipping a
helical coiled spring into a liquid coating and withdrawing and air
drying the coating at room temperature to form a protective coating
defining a cylindrical wall completely surrounding and defining an
inner and an outer wall surface therefor.
It is a still further object of the present invention to provide an
introducer sheath having a valve assembly formed of a first elastic
membrane having a central aperture and a second elastic membrane in
sealing contact therewith and having an angled slit therein.
In accordance with an aspect of the present invention, a flexible
tube for the introduction of catheters and like devices into a
vascular system, includes a helical coiled spring having a
plurality of coils, each of a plurality of the coils being spaced
from at least one adjacent coil; and a thin cylindrical wall
completely surrounding the spring and defining an inner and outer
wall surface, the portion of the cylindrical wall surrounding each
coil having a first thickness and the portion of the cylindrical
wall between the spaced coils having a second, smaller thickness,
with the inner and outer wall surfaces being indented thereat; the
cylindrical wall prepared from a coating composition comprising a
thermoplastic polymeric material dissolved in a solvent solution,
said composition having a solids content that may range from about
4% to about 18%. Suitable polymers include polyurethanes, vinyl
polymers such as polyvinylchloride, and elastomeric materials such
latex and silicone polymers. Solvents may be selected from the
group consisting of tetrahydrofuran, dioxane, methyl ethyl ketone,
dimethylformamide, cyclohexane and mixtures thereof.
In accordance with another aspect of the present invention, a
method of forming a flexible tube for the introduction of catheters
and like devices into a vascular system, includes the steps of
preparing a liquid coating comprising the composition of the
present invention, by dissolving 4-18% by weight of a suitable
thermoplastic polymeric material in a solvent solution comprising
solvents selected from the group consisting of tetrahydrofuran,
dioxane, methyl ethyl ketone, dimethylformamide, cyclohexane and
mixtures; dipping a helical coiled spring having a plurality of
coils into the composition, each of a plurality of the coils being
spaced from at least one adjacent coil; withdrawing the spring from
the composition at a rate ranging from one foot per minute to eight
feet per minute to form a protective coating thereover; and drying
the resulting coating at room temperature to form a cylindrical
wall coating completely surrounding the spring and which defines an
inner and outer wall surface, such that the portion of the
cylindrical wall surrounding each coil has a first thickness and
the portion of the wall between the spaced coils has a second,
smaller thickness, with the inner and outer surfaces being indented
thereat.
In accordance with still another aspect of the present invention, a
valve assembly for an introducer sheath includes a first elastic
membrane having a first exterior surface, a first interior surface
and an aperture extending between the first exterior and interior
surfaces; and a second elastic membrane having a second exterior
surface in sealing contact with the first interior surface of the
first elastic membrane, a second interior surface, and a slit
extending between the second exterior and interior surfaces at an
angle from the direction of fluid flow in the introducer sheath,
the slit being in fluid communication with the aperture.
The above, and other, objects, features and advantages of the
present invention will become readily apparent from the following
detailed description thereof which is to be read in connection with
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a longitudinal cross-sectional view of an introducer
sheath according to one embodiment of the present invention;
FIG. 2 is an enlarged cross-sectional view of a portion of the
flexible tube of the introducer sheath of FIG. 1;
FIG. 3 is a plan view of the interior surface of the first elastic
membrane of the valve assembly shown in FIG. 1; and
FIG. 4 is a plan view of the exterior surface of the second elastic
membrane of the valve assembly shown in FIG. 1.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
Referring to the drawings in detail, and initially to FIG. 1, an
introducer sheath assembly or hemostasis cannular assembly 10
generally includes a cylindrical hub or main body portion 12 and a
gradually tapered portion 14. Cylindrical hub portion 12 is open at
its free end 16 and is formed with a frusto-conical configured
central aperture 18 which diverges from free end 16 and extends
partly through tapered portion 14. The latter tapered portion 14 is
formed with a longitudinal aperture 20 of constant diameter, in
fluid communication with aperture 18 and which extends to the open,
free end 22 of tapered portion 14 at the outlet side of introducer
sheath assembly 10. As will be appreciated from the discussion
hereinafter, the diameter of longitudinal aperture 20 is slightly
greater than that at the smaller diameter end of frusto-conical
configured aperture 18 so as to define a circumferential shoulder
24 directed toward the outlet side of introducer sheath assembly
10.
The free end of cylindrical hub portion 12 is cut away, as at 26 to
define a circumferential shoulder 28 directed toward the inlet side
of introducer sheath assembly 10, and so as to also form a
circumferential flange 30, as shown in FIG. 1.
In addition, an extension 32 is formed at an angle on cylindrical
hub portion 12 and defines a secondary inlet port 34 formed by an
aperture therein. A smaller diameter aperture 36 formed in
cylindrical hub portion 12 provides fluid communication between
secondary inlet port 34 and the chamber defined by frusto-conical
configured aperture 18. A tube 33 is positioned within inlet port
34 for introduction of fluids therein.
In accordance with an aspect of the present invention, a flexible
tube 38 for the introduction of catheters and like devices into a
vascular system, is provided with a helical coiled spring 40
completely surrounded by a protective coating that defines
cylindrical wall 42, as shown more clearly in FIG. 2. Although not
shown, the free end of flexible tube 38 can be attached to a
conventional introducing tube (not shown).
In particular, helical coiled spring 40 includes a plurality of
coils, each being spaced from an adjacent coil, although it is
possible that some of the coils are tightly wound in contact with
each other such that only each of a plurality of the coils is
spaced from at least one adjacent coil. Helical coiled spring 40
may be constructed of any suitable material, such as stainless
steel, or even a plastic material, each coil having a diameter as
low as 0.002 inch.
Because of the fineness of the coils that can be used, an extrusion
coating method cannot be used for forming cylindrical wall 42 about
helical coiled spring 40. Also, for this same reason and because
the coils could be constructed of a plastic material, a heat
treatment for forming protective coating thereover cannot be
used.
It is important in forming the protective coating that defines
cylindrical wall 42, that the wall thickness thereof be relatively
reduced, for example as low as 0.005 inch, while retaining the
structural integrity of kink resistance, crush resistance and
linear compression resistance and, at the same time, providing
sufficient flexibility of tube 38.
Accordingly, cylindrical wall 42 is formed from a protective
coating composition comprising a thermoplastic polymeric material
dissolved in a solvent solution. Generally, the composition
possesses a solids content ranging from about 4% to about 18%, with
a 10% solids content preferred. The thermoplastic polymeric
material may be selected from the group consisting of
polyurethanes, vinyl polymers such as polyvinylchloride, and
elastomeric materials such as latex and silicone polymers. The
hardness of the polymeric material may vary, with hardness as
expressed in Shore A Durometer ratings capable of ranging from
about 70 to about 95. Naturally, materials possessing lower
Durometer ratings are softer and will exhibit greater
flexibility.
For example, a polyurethane polymer sold under the U.S. Registered
Trademark "PELLETHANE CPR" No. 2103-85AE by the CPR Division of the
Upjohn Company can be used as the thermoplastic polymeric material.
This material has a hardness of approximately 87.+-.4 measured in a
Shore A Durometer Test (ASTM D 2240 Test Method).
Suitable solvents are selected from the group consisting of
tetrahydrofuran, dioxane, methyl ethyl ketone, dimethylformamide,
and cyclohexane, and mixtures thereof. Preferably, the solvent
solution comprises a mixture of dioxane and tetrahydrofuran in a
relative ratio ranging from 1:9 to 6:4, and preferably a ratio of
1:1.
Flexible tube 38 is formed by first forming the helical coiled
spring 40 such that the coils thereof are spaced from each other,
as previously discussed. The helical coiled spring 40 is then
dipped into the aforementioned liquid coating composition, and
spring 40 is then withdrawn from the composition at a rate ranging
from one foot per minute to eight feet per minute, whereupon the
coating is dried at room temperature to form cylindrical wall 42
that completely encloses spring 40. Drying of the coating takes
approximately 15 to 30 minutes. Preferably the steps of dipping
spring 40 and drying at room temperature are repeated three or four
times.
Although spring 40 may remain in the solution a few seconds, it is
the rate at which spring 40 is withdrawn from the solution rather
than its residence time that is important. This is because a faster
rate of withdrawal of spring 40 from the solution assists in
retaining a greater amount of solution on spring 40. This faster
withdrawal appears to counteract the forces of capillary action
that tends to draw the deposited solution away from spring 40 and
back into the vessel into which spring 40 was initially dipped. It
has been found that a rate of between one foot per minute to eight
feet per minute is a satisfactory withdrawal rate, and preferably a
rate of four feet per minute is used.
As shown in FIG. 2, cylindrical wall 42 is thereby formed with a
first wall thickness D surrounding each coil and a second, smaller
wall thickness d at positions between adjacent spaced coils of
spring 40. Accordingly, cylindrical wall 42 effectively defines an
inner wall surface 44 and an outer wall surface 46, with both inner
surface 44 and outer surface 46 being indented at positions between
adjacent spaced coils of spring 40. As a result, the smaller wall
thickness acts a hinge and thereby permits tube 38 to be highly
flexible. At the same time, relatively small diameter coils can be
used, and the wall thickness of flexible tube 38 can be made
relatively small. This is distinguishable, for example, from U.S.
Pat. No. 3,618,613 which requires the use of an inner tubing about
which the spring is friction or interference fit, and whereby a
larger wall thickness is provided, with less flexibility.
Preferably, tube 38 and more particularly protective coating 42, is
further coated with an interpolymer 41 that preferably consists of
polyvinylpyrrolidone and polyurethane. This coating 41 is
hydrophilic and reduces the coefficient of friction significantly,
which is important when the catheter is being introduced through
the introducer sheath. The coating is also thromboresistant which
is important for products of this type that are to be left in the
human body for relatively long periods of time. In this regard,
other thromboresistant coatings that can be used are described in
U.S. Pat. Nos. 3,746,683; 3,759,788; and 4,378,803.
In accordance with another aspect of the present invention, a valve
assembly 48 is provided at the inlet end of introducer sheath
assembly 10 and is formed of a first elastic membrane 50 and a
second elastic membrane 52 in sealing contact therewith. In
particular, first elastic membrane 50 has a circular configuration
and is formed with an exterior surface 54 and an interior surface
56, with a circumferential flange 58 extending from interior
surface 56 and spaced inwardly from the outer circular edge 60 of
membrane 50. As shown in FIGS. 1 and 3, first elastic membrane 50
is formed with a central aperture 62 which converges from exterior
surface 54 toward interior surface 56. The diameter of central
aperture 62 at the interior surface 56 is as small as 0.032 inches
which will seal around the guide wire that is introduced into an
artery.
Second elastic membrane 52 is formed in a circular configuration
and includes an exterior surface 64 and an interior surface 66 with
a slit 68 extending between exterior surface 64 and interior
surface 64 and interior surface 66. Slit 68 passes through the
center 70 of exterior surface 64 and is angled toward interior
surface 66, as shown in FIGS. 1 and 4. Because of such angle, when
a catheter is withdrawn, the back pressure of fluid within the
chamber defined by frusto-conical configured aperture 18 provides a
positive closure and sealing arrangement to prevent the escape of
fluid.
In constructing and mounting valve assembly 48, the outer diameter
of second elastic membrane 52 is substantially equal to the inner
diameter of flange 58 such that second elastic membrane 52 fits
within flange 58 to provide a sealing contact therewith. At the
same time, the exterior surface 64 of second elastic membrane 52 is
positioned in sealing contact with the interior surface 56 of first
elastic membrane 50. In such position, it will be appreciated that
center 70 of exterior surface 64, through which slit 68 passes, is
in axial alignment with the central axis of aperture 62 of first
elastic membrane 50.
In this regard, the present invention provides a relatively simple,
yet novel, construction of a valve assembly, which provides
positive prevention of fluid, that is, prevents fluid loss.
In operation of the valve assembly, first elastic membrane 50
having central aperture 62 will maintain a sealing relationship
with a catheter introduced into an artery. Upon withdrawal of the
catheter from the passage, second elastic membrane 52 having slit
68 will provide a sealing arrangement with the catheter, thus
preventing blood leakage.
Having described a specific preferred embodiment of the present
invention with reference to the accompanying drawings, it is to be
understood that the present invention is not limited to that
precise embodiment, and that various changes and modifications may
be effected therein by one of ordinary skill in the art without
departing from the spirit or scope of the present invention as
defined by the appended claims.
* * * * *