Catheter with interior balloon

A catheter includes a body having tubular walls defining a lumen extending along an axis from the distal end of the body to a proximal end of the body. Portions of the walls define at least one balloon hole extending from the lumen through the walls of the body. Elastomeric material restrained to the hole defining portions interiorly of the body expand outwardly of the (catheter) body to form a balloon when the lumen is pressurized with fluid. The elastomeric material my take the form of a patch or a full lining of the catheter walls defining the lumen. A method for making the catheter includes the step of retaining portions of an elastomeric layer around the hole interiorly of the lumen. A preferred method of manufacturing the catheter includes the step of providing the catheter body and an inner layer of elastomeric sheet material simultaneously in a co-extruder.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates generally to catheters adapted for use in surgical 
procedures and more specifically to catheters having inflatable balloons. 
2. Discussion of the Prior Art 
In many surgical procedures it is desirable to introduce an elongate 
flexible object into a body conduit and to enlarge the distal end of that 
object at an operative site. Catheters are well known to perform this 
function, and in one common variety a balloon is disposed at the distal 
end of the catheter to provide for the desired enlargement. When this 
balloon is inflated, it typically exceeds the radial diameter of the 
catheter. 
Several surgical procedures, such as embolectomy and angioplasty 
procedures, take advantage of this balloon catheter construction. In an 
embolectomy procedure, the distal end of the catheter is introduced beyond 
a thrombus or embolus, the balloon is inflated, and the catheter with 
enlarged balloon is withdrawn. In this procedure, the enlarged balloon 
pushes the thrombus or embolus out of the vessel as the catheter is 
withdrawn. 
In an angioplasty procedure, the balloon of the catheter is inflated in 
proximity to athroscorotic plaque. In this common procedure, the pressure 
of the balloon forces the plaque against the vessel walls hereby enlarging 
the flow path through the vessel. These and other techniques benefiting 
from balloon catheter technology are disclosed in the following patents 
which are incorporated herein by reference: 
______________________________________ 
U.S. Pat. No. Inventor 
______________________________________ 
3,438,375 R. Ericson 
3,866,599 C. Johnson 
4,217,903 R. Witherow 
4,254,774 J. Boretos 
4,823,812 U. Eshel 
4,913,701 A. Tower 
5,036,868 A. Berggren 
______________________________________ 
In all of these procedures, the initial diameter of the catheter is of 
particular interest. This elongate flexible structure is typically 
introduced through long, sometimes torturous, conduits in order to reach 
the operative site. In some cases, these conduits are quite narrow so that 
the diameter of the catheter is of critical importance. Such is the case 
with arteries in the hand of a patient. An embolectomy procedure performed 
in these environments might require a catheter having a diameter as small 
as 1 French. 
The problem with achieving catheter diameters of this size has been 
significantly compounded in the case of balloon catheters. With these 
devices, the balloon structure has typically been provided on the outside 
of the catheter thereby increasing the diameter of the device. An 
inflation hole extends through the catheter wall into an inflation lumen 
of the catheter. The balloon with a cylindrical configuration is disposed 
over this hole and wound on the catheter body to form a seal on either 
side of the hole. By pressurizing the inflation lumen, an inflation fluid 
passes through the hole to inflate the balloon beyond the outer surface of 
the catheter body. 
Attempts have been made to reduce the overall thickness of this balloon 
structure. The catheter wall has been thinned so that the diameter of the 
balloon windings can be formed in a recess. This has weakened the catheter 
walls so that the balloon windings tend to compress the lumen of the 
catheter. In some instances, metal bushings have been placed over the 
recess to prevent the collapse of the catheter walls. In such a 
combination, the total thickness of the catheter is determined by the 
thickness of four separate structural elements, the catheter wall, the 
bushing, the balloon and the winding. Since each of these elements has a 
cylindrical configuration, the wall thickness of each element is doubled 
in defining the diameter of the total construction. Thus, the catheter 
body provides two wall thicknesses in the overall diameter of the 
catheter. Similarly, the bushings, the balloon, the windings and any glue 
associated with the winding structure each add two thicknesses of material 
to the diameter of the catheter. As a consequence, eight layers of 
material have typically contributed to the overall thickness of the 
catheter. 
In spite of the many disadvantages relating to the overall size of such 
catheters, the methods for constructing the catheter have demanded this 
configuration. The catheter body has typically been extruded, and any 
recesses provided in the catheter wall have been machined along with the 
inflation hole. Bushings have been placed over the recesses. The balloon 
in the initial form of a cylindrical elastic material has been positioned 
across the inflation hole and the balloon has been stretched and wound 
over the bushings. Gluing these windings in place has completed formation 
of the balloon structure. 
Based on this method, typical of the prior art, the entire balloon 
structure has been formed on the exterior of the catheter body because of 
its accessibility. The detrimental effect on the overall diameter of the 
catheter has been accepted without recourse, but it has necessarily 
limited any possibility of providing balloon catheters in sizes smaller 
than 2 Fr. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, an elongate catheter body is 
provided with an inflation lumen. Importantly, the balloon material is 
disposed interiorly of the catheter body in the inflation lumen. This 
material is restrained around a balloon hole which extends through the 
wall of the catheter into the inflation lumen. The balloon hole may be 
provided at the distal end of the catheter or in the side wall of the 
catheter body. When the inflation fluid is introduced into the inflation 
lumen, the balloon material expands through the balloon hole, outwardly of 
the catheter body. 
When the catheter is initially inserted, the balloon material is disposed 
interiorly of the catheter body so that the maximum diameter of the 
catheter is dictated solely by the outside diameter of the catheter wall. 
There need be no bushings, windings or glue on the outside of the catheter 
wall to increase this diameter. In its thinnest configuration, the entire 
catheter structure can be formed with only three thicknesses of material, 
two thicknesses resulting from the cylindrical catheter wall and a single 
thickness of elastic material restrained around a side hole in the 
catheter. 
With only three wall thicknesses, as opposed to the eight wall thicknesses 
of the prior art, significantly smaller diameters of catheters can now be 
formed making this important technology available in many new areas of the 
body anatomy. 
These and other features and advantages of the present concept will be more 
apparent with a description of preferred embodiments and the best mode of 
the invention, and reference to the associated drawings.

DESCRIPTION OF PREFERRED EMBODIMENTS 
A catheter is illustrated in FIG. 1 and designated generally by the 
reference numeral 10. This catheter 10 includes a balloon structure 12 and 
is representative generally of any elongate medical instrument which is 
insertable through a body cavity or conduit to provide an inflatable 
structure at a distal location. Such instruments may include not only 
catheters but also endoscopes. 
In the case of a catheter, a balloon structure is known to provide 
advantages in both embolectomy and dilatation procedures. In an 
embolectomy procedure, the catheter is inserted into a vessel and guided 
so that its distal tip extends beyond an embolus or thrombus. At this 
location a distal balloon is inflated to fully occupy the interior lumen 
of the vessel. As the catheter is withdrawn through the incision in the 
vessel, the balloon pushes the embolus or thrombus thereby removing it 
from the vessel. 
In dilatation procedures, the catheter is inserted into a conduit, such as 
the urethra, and inflated to push the conduit walls outwardly thereby 
enlarging or dilating the conduit. In one type of dilatation procedure 
atherosclerotic plaque coats the interior walls of a vessel and blocks 
blood flow. In this procedure, the catheter is inserted into the vessel to 
the point where the blockage occurs. At this location, the balloon is 
inflated pressing the plaque against the vessel walls thereby dilating the 
vessel. In all of these cases, the balloon structure provides means for 
producing a pressure or force exteriorly of the body to perform some 
function at an operative site within a body conduit. 
The catheter 10 will typically include an elongate catheter body 14 having 
some degree of flexibility. The body 14 is typically formed along an axis 
16 which extends between a proximal end 18 and a distal end 21 of the 
catheter 10. A hub 27 is disposed at the proximal end 18 of the catheter 
10 and may include at least one Luer fitting 30. The fitting 30 permits 
attachment of the catheter 10 to various external systems, such as a 
source of inflation pressure (not shown). 
The catheter body 14 will typically take the form of an elongate cylinder 
having an outer wall 36 which at least partially defines an inflation 
lumen 38 that extends from the hub 27 to the balloon structure 12. In many 
catheters, the inflation lumen 38 will merely be one of several lumens 
which perform various functions in a particular embodiment of the catheter 
10. The opening 34 is configured such that it extends through the catheter 
wall 36 providing a passage from the inflation lumen 38 through the wall 
36 to regions exterior of the catheter 10. 
In a preferred embodiment, the balloon structure 12 includes a membrane 41 
of elastomeric material, and means for retaining that membrane 41 around 
the opening 34. In the form illustrated in FIG. 1, this retention means 
include a bead of glue 43 which fixes the membrane 41 to the catheter wall 
36 and any other portions of the catheter body 10 which define the opening 
34. The retention means may form a seal around the opening 34 but these 
sealing characteristics may not be required in a particular embodiment. 
In the embodiment illustrated in FIG. 1, the membrane 41 forms a balloon 45 
which is operable between a deflated state (shown by the solid lines 47 in 
FIG. 1) and an inflated state (shown by the dotted lines 50 in FIG. 1). 
The balloon structure 12 can be located anywhere along the catheter body 14 
but will typically be disposed at the distal end 21 in proximity to an 
opening 34 in the catheter body 14. In the embodiment illustrated in FIG. 
1, this opening 34 is located at the end of the catheter body 14 where the 
opening 34 is formed in a radial plane and faces axially of the catheter 
10. In other embodiments, the opening 34 may be formed in the side of the 
catheter body as illustrated in FIG. 2. 
It is of particular importance to the present invention that in the 
deflated state, the balloon structure 12 is disposed entirely within the 
circumferential dimension defining the outer surface of the catheter wall 
36. There is no balloon membrane or other elastomeric material or any 
retention adhesive or windings which exceed this diameter of the catheter 
wall 36. In the illustrated embodiment, the balloon structure 12 is 
disposed entirely within the inflation lumen 38 where the bead of glue 43 
retains the membrane 41 circumferentially of the lumen 38. 
In operation, a source of inflation pressure (not shown) is coupled to the 
Luer fitting 30 and a pressurizing medium, such as saline, is introduced 
into the inflation lumen 38. As this inflation medium is pressurized, the 
membrane 41 associated with the balloon 45 expands through the opening 34 
to the inflated state shown by the dotted lines 50. When the inflation 
medium is withdrawn or depressurized, the elastomeric characteristics 
associated with the membrane 41 cause it to retract back from the enlarged 
inflated configuration. 
When the balloon 45 is initially inflated, the inflation pressure forces it 
against the catheter wall 36 forming a seal around the circumference of 
the opening 34. This seal, designated by the reference numeral 52, may 
form regardless of any sealing characteristics which may be associated 
with the retention means, such as the bead of glue 43. 
In the embodiment of FIG. 2, the distal end 21 of the catheter body 14 is 
closed by an end cap 56 which can be molded with, glued to, or otherwise 
attached to the catheter wall 36. As previously noted, the opening 34 in 
this embodiment is formed in the side of the catheter body 14 where it 
extends radially of the catheter wall 36 and faces laterally of the 
catheter 10. 
As in the previous embodiment, the membrane 41 is retained to the catheter 
wall 36 around the opening 34 and interiorly of the inflation lumen 38. In 
this particular case, the membrane 41 will have a more planar 
configuration in axial cross-section than the balloon 45 in the FIG. 1 
embodiment. Nevertheless, as the inflation lumen 38 is pressurized, the 
membrane 41 will expand outwardly through the opening 34 to form the 
inflated balloon 50. As in the previous case, the inflated balloon 50 will 
extend in the same direction as the opening 34 which in the case of the 
FIG. 2 embodiment is laterally of the catheter 10. 
The embodiment of FIG. 2 is of particular interest since it provides 
potentially the most narrow configuration for the catheter 10. In this 
particular embodiment, the cross-section of the catheter includes only 
three layers of material. Two of the layers result from the catheter wall 
36 but only a single layer of the membrane 41 is required for this 
embodiment. In contrast, it will be noted that the embodiment of FIG. 1 
includes four layers of material, two each associated with the catheter 
wall 36 and the membrane 41. 
With reference to FIG. 2A it will be apparent how this reduced thickness is 
achieved. As illustrated, the bead 43 which retains the membrane 41 to the 
catheter wall 36 is formed on only one side of the axis 16. It follow that 
along any cross-sectional diameter of this embodiment, there is only a 
single thickness of the membrane 41. Nevertheless, this embodiment forms a 
fully inflatable balloon 50 as long as the bead 43 fully circumscribes the 
opening 34. 
In the further embodiment of FIG. 2, a lateral balloon such as that 
illustrated in FIG. 2 can be formed with a radially glue bead 43 similar 
to that illustrated in FIG. 1. In this case, the opening 34 is formed 
laterally of the axis 16 as in the FIG. 2 embodiment, but the membrane is 
provided with the more spherical configuration as in the FIG. 1 
embodiment. Although the membrane 43 does not closely circumscribe the 
opening 34, it is nevertheless attached to those portions of the catheter 
wall 36 that define the opening 34. This embodiment benefits from ease of 
manufacture as will be more apparent from the following discussion of 
manufacturing techniques. 
The radial glue bead 43 may be closely spaced to the opening 34 as 
illustrated in FIG. 3 or it may be distantly spaced from the opening 34 as 
illustrated in FIG. 4. The only requirement for this relationship between 
the radial bead 43 and the opening 34 is that the bead 43 be disposed 
proximally of the opening 34. In the embodiment of FIG. 4 an injection 
port 61 is provided between the glue bead 43 and the opening 34. This port 
61 provides access to lumen 38 and facilitates introduction of an 
injectate into the catheter 10 and outwardly through the opening 34. 
This introduction of an injectate would most easily be accomplished with 
the balloon 45 in the deflated state shown by the solid lines 47. In this 
state, the injectate entering the port 61 would be forced between the 
membrane 41 and the catheter walls 36, as shown by the arrow 63, to exit 
the catheter 10 through the opening 34. 
In the embodiment of FIG. 5, a more conventional catheter is illustrated to 
include a catheter wall 70 and a balloon 72 which is glued or wound on the 
outside of the catheter wall 70. In this case, a sheath 74 is provided to 
enclose the catheter wall 70 as well as the balloon 72. The opening 34 is 
provided in the sheath 74. As the balloon 72 is inflated (through a lumen 
formed by the catheter wall 70) it is restricted in all directions by the 
sheath 74 except in the area of the opening 34. As a result, the balloon 
72 expands through the opening 34 forming the seal 52 with the sheath 74. 
It is apparent that a lateral balloon could also be formed by a lateral 
opening 34 similar to that illustrated in FIG. 2. 
In a further embodiment of the invention, multiple balloons can be formed 
by providing more than one opening 34 in the catheter wall 36 or sheath 
74. The embodiments of FIGS. 6 through 10 are representative of such 
multiple balloon configurations. In FIG. 6, a pair of radially spaced 
openings 34a and 34b are formed in the catheter wall 36. In the manner 
previously discussed, the application of pressure to the inflation lumen 
38 results in inflating the membrane 41 through the openings 34a and 34b 
to form the respective inflated balloons 50a and 50b. These balloons 50a, 
50b are radially spaced as best shown in FIG. 7. 
Multiple balloons can also be radially spaced to form a single balloon 
structure that fills the entire circumference around the catheter 10. Such 
an embodiment is illustrated in FIG. 8 wherein the balloon structure 12 
includes three separate balloons 50c, 50d, and 50e formed from a single 
membrane 41 deployed through respective openings 34c, 34d, and 34e. The 
resulting balloon configuration provides a substantially constant pressure 
radially outwardly around the entire circumference of the catheter 10. 
This embodiment will be of particular interest in dilatation and 
embolectomy procedures which are typically conducted in a blood vessel, 
such as that designated by the reference numeral 81. 
In the same manner that the balloons 50a-50e are radially spaced, the 
balloons can also be axially spaced as illustrated in FIG. 9. In this 
case, a pair of balloons 50f and 50g can be inflated through the 
respective openings 34f and 34g. Of course various combinations of 
radially and axially spaced balloons will now be apparent. For example, 
two of the triple balloon structures illustrated in FIG. 8 could be 
axially spaced as illustrated in FIG. 9 to provide a substantially 
constant circumferential pressure at two axial locations. 
The embodiment of FIG. 10 illustrates that the openings 34 can be 
substantially any shape, not just the circular configuration previously 
discussed. In FIG. 10, the opening is longitudinal in configuration and 
spirally oriented with respect to the catheter body 14. This opening is 
divided by several bridges 85 which divide the opening into segments 34h, 
34i and 34j. These bridges 85 may be desirable to increase the column 
strength and structural rigidity of the catheter 10. With the openings 
divided into segments 34h through 34j, the resulting balloon is also 
segmented into spiral balloon portions 50h, 50i, and 50j respectively. As 
with the embodiments of FIGS. 6 through 9, the multiple balloons 50h-50j 
can be formed from a single membrane 41. 
The methods for manufacturing the foregoing embodiments of the concept are 
quite diverse. The embodiment of FIG. 5 can be most easily manufactured 
since a large portion of this embodiment is a conventional catheter 
construction including the catheter wall 70 and the balloon 72 which is 
wound on the outer surface of the catheter wall 70. This structure is then 
inserted into the sheath 74 which has been appropriately apurtured to form 
the opening 34 either laterally or axially of the sheath 74. 
Embodiments of the invention which require an elastomeric tube within an 
outer tube, such as the embodiments of FIGS. 1 and 3 through 10, can be 
formed in several manners. As illustrated in FIG. 11, a mandrel 81 can be 
provided with a diameter generally equivalent to the diameter desired for 
the inflation lumen 38. The length of the mandrel 81 should be such that 
it can extend from the proximal end 18 of the catheter body 14 to the 
distal end 21. 
A vessel 83 containing the elastomeric material desired for the membrane 41 
can be provided and heated to give the material 41 fluid characteristics. 
Then the distal end of the mandrel 81 can be dipped in the heated material 
of the membrane 41 to form a coating on the mandrel. This coating can be 
partially cured to provide it with a more solid configuration for the 
balloon 45. 
Of particular importance to this process is the axial insertion of the 
coated mandrel 81 into the catheter body 14 as illustrated in FIG. 12. 
This catheter body 14 can be formed in accordance with conventional 
extrusion methods. After the balloon 45 is in place, the mandrel 81 can be 
removed leaving the balloon 45 within the catheter body 14. The step of 
withdrawing the mandrel 81 can be facilitated by initially coating the 
mandrel with a release agent so that it can be easily removed, leaving the 
balloon 45 in place. 
This method may be preferred since the end of the balloon 45 is 
automatically formed in the dipping step of the process. No additional 
action need be taken in order to close the inflation lumen of the balloon 
45. However, as a final step in this process, the distal end of the 
catheter body 14 will need to be closed if an lateral opening 34 is 
contemplated. This closure of the catheter body 14 can be accomplished by 
melting and molding the catheter material over the distal end of the 
catheter body or otherwise preforming a distal tip and attaching the tip, 
such as the end cap 56, to the catheter body 14. 
A coextrusion process can also be used to form an elastomeric tube within 
the catheter body 14. As illustrated in FIG. 13, the materials associated 
with the catheter body 14 and the membrane 41 can be loaded into 
respective hoppers 83 and 85, heated, and forced by way of respective 
screws 87, 90 into a crosshead 92. The crosshead 92 is configured in 
accordance with known techniques to extrude an inner tube from the 
material in the hopper 85 and an outer tube from the material in the 
hopper 83. The result is a tubular membrane 41 within a more rigid 
catheter body 14. This coextrusion can be cut to length and the distal end 
formed to produce the embodiments of FIGS. 3 and 4. In this process the 
elastic membrane 41 can to be closed at the distal end in order to form 
the balloon 45. If a lateral opening 34 is provided, the distal end of the 
catheter body 14 also can be closed in accordance with methods previously 
discussed. 
If a particular method can accommodate formation of the opening 34 prior to 
inserting or otherwise forming the elastic membrane 41 within the outer 
tube 14, this is desirable. For example, in the method of FIG. 12, the 
lateral opening 34 can be formed prior to insertion of the coated mandrel 
81. 
If the prior formation of the opening 34 is not possible, that opening 
needs to be carefully formed in the catheter wall 36 without puncturing 
the membrane 41. This can be most easily accomplished using a laser 96 
which can be carefully operated to control the depth of the cut. By 
limiting this depth to the thickness of the catheter wall 36, any cutting 
of the membrane 41 can be avoided. 
Another alternative for cutting the catheter wall 36 without penetrating 
the membrane 41 is to mechanically drill the catheter wall 36 with a flat 
end drill bit 98, as illustrated in FIG. 15. 
This cutting either by the laser 96 or the drill bit 98 can be further 
facilitated by use of a vacuum 98 to draw the balloon 45 into a collapsed 
configuration as illustrated in FIG. 16. This will withdraw the balloon 45 
from proximity to the catheter wall 36 so that the cutting steps 
illustrated in FIGS. 14 and 15 need not be as carefully controlled. 
The materials associated with the present invention are of particular 
interest not only to facilitate their functions in a preferred embodiment 
of the catheter 10, but also to enable the foregoing processes of 
manufacture. In general the materials associated with the catheter body 14 
and the membrane 41 can be any thermoplastic or thermoset material. 
Depending on the process of manufacture, these materials are formable in 
that they can be molded. Some of these materials are also extrudable which 
facilitates the process illustrated in FIGS. 13 and 13a. In most 
embodiments, both the catheter body 14 and the membrane 41 will be 
flexible although rigid and semi-rigid configurations may also benefit 
from the concept. 
The material associated with the membrane 41 will typically be more 
flexible than the material associated with the body 14 which is relied on 
for additional column strength. The durometer of the material forming the 
body 14 will preferably be in a range from Shore 5A to Shore 100D. A range 
of particular advantage occurs from a Shore hardeess of 35D to 100D. 
In comparison, the material forming the membrane 41 will preferably have a 
durometer between Shore 5A and Shore 100D. A preferred range of durometer 
might be between Shore 25A and Shore 100D. Regardless of the durometer of 
the material, the flexibility of the catheter 10 is of primary 
consideration. In embodiments wherein the wall thicknesses of the body 14 
and the membrane 41 are quite small, higher durometers such as Shore 50D 
may still provide the desired flexibility. 
The thermoplastic and thermoset materials which are of particular interest 
for the body 14 include rubbers, elastomers, silicones and polycarbonates. 
Materials of interest for the membrane 41 include rubber, elastomers 
including urethanes, polyethylene, polyethyleneterethalate, 
polyvinylchloride, silicone, nylon and latex. 
In a preferred embodiment the catheter body is formed from Hytrel, a 
trademark of DuPont de Nemours. This material is coextruded with an 
outside diameter of about 1 Fr. to 10 Fr. and an inside diameter of about 
0.005-0.100 inches. The membrane 41 is coextruded from Craton, a trademark 
of Shell Oil Company. The membrane 41 is coextruded in juxtaposition to 
the inner surface of the catheter body 14. An inflation lumen of about 
0.003-0.080 inches diameter is formed in this particular embodiment so 
that the membrane 41 has the thickness of about 0.001 to 0.020 inches. 
Beyond these considerations, the materials forming the catheter body 14 and 
the membrane 41 can be selected for their compatibility with each other. 
Generally it is felt that the materials are compatible if the membrane 41 
does not automatically adhere to the material forming the catheter body 
14. This permits the membrane 41 to freely move relative to the catheter 
wall 38 so that it can stretch through and beyond the opening 45 to form 
the expanded balloon 50. If it is preferrable to use materials which are 
not compatible in this sense, a release agent can be coextruded or applied 
to the balloon 45 on the dipped mandrel 81. Such a release agent would 
typically provide the characteristics required for these otherwise 
incompatible materials. 
Many variations in the concept of this invention will now be apparent to 
those skilled in the art of balloon catheter design. Certainly different 
materials can be contemplated for the membrane 41 as well as the catheter 
body 14. Similarly, steps in the manufacturing processes can be altered 
all within the skill of the art. Many different embodiments of the 
invention can be formed by adjusting the various positions for the opening 
34 as mentioned with respect to the examples of FIGS. 6-10. 
It will also be noted that in a particular catheter construction, multiple 
lumens can be formed each with its own membrane 41 or balloon 45 which 
would be independently inflatable and deflatable to achieve the advantages 
of the present concept. In such an embodiment, multiple balloons could be 
provided around the circumference of the catheter body 14 in the manner 
illustrated in FIG. 7. By independently inflating each of the balloons 
around the circumference, the distal tip of the catheter could be guided 
in a direction opposite to the inflated balloon. In such an embodiment, 
the catheter could function not only for embolectomy or dilatation 
purposes, but also as a guiding catheter. 
Given the wide variety of substitutions, all within the breadth of this 
concept, the broad scope of the invention should not be limited to the 
drawings and the described embodiments, but should be ascertained only 
with reference to the following claims.