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APPARATUS AND METHOD FOR FORMING
COMPLEX-SHAPED COMPONENTS IN A
HEATED POLYMERIC FILM
CROSS-REFERENCE TO RELATED 5
This application is a divisional of pending U.S. patent application Ser. No. 08/948,615, filed Oct. 10, 1997 now abandoned.
The present invention is directed toward a method of making medical components, and more particularly toward a method of making contoured, thin-walled, complex- 15 shaped medical components usable with intrabody medical devices.
BACKGROUND OF THE INVENTION
The use of intrabody medical equipment, such as endoscopes, catheters, and the like, for diagnostic and therapeutic indications is rapidly expanding. To improve performance, the equipment has been optimized to best accomplish the selected purpose. As an example, endo- 2J scopes have been optimized and refined so as to provide upper endoscopes for the examination of the esophagus, stomach, and duodenum, colonoscopes for examining the colon, angioscopes for examining blood vessels, bronchoscopes for examining the bronchii, laparoscopes for exam- 3Q ining the peritoneal cavity, arthroscopes for examining joints spaces, nasopharygoscopes for examining nasal passages and pharynx, and intubation scopes for examination of a person's airway.
Optimization of the intrabody medical devices for such 35 therapeutic and diagnostic procedures has resulted in sterile, inexpensive disposable equipment that is used alone or with non-disposable equipment. In the field of endoscopes, a conventional endoscope 10, shown in FIG. 1, has an insertion tube 12 that is connected at its proximal end 14 to a 40 handle or control body 16. The insertion tube 12 is adapted to be inserted into a patient's body cavity to perform a selected therapeutic or diagnostic procedure. The insertion tube 12 contains an imaging system 18 having optical fibers or the like extending along the length of the insertion tube 45 and terminating at a viewing window 19 in the insertion tube's distal end 20. The imaging system 18 conveys an image from the viewing window 19 to an eyepiece 22 on the control body 16 or to a monitor (not shown), so the user can see into a selected body cavity during an endoscopic pro- 50 cedure. The endoscope 10 is described in greater detail in U.S. Pat. No. Re 34,110 and U.S. Pat. No. 4,646,722, which are incorporated by reference herein.
Disposable endoscopic sheath assemblies are used to cover the insertion tube 12 and protect it from being con- 55 taminated. Accordingly, the sheath assemblies alleviate the problem and cost of cleaning and sterilizing the. insertion tube 12 between endoscopic procedures. As seen in FIG. 1, a conventional sheath assembly 24, shown partially cut away for illustrative purposes, includes a flexible, elastic 60 sheath 26 that tightly surrounds the endoscope's insertion tube 12. The sheath 26 may also contain one or more working channels 32 that extend along the insertion tube 12 and that are adapted to receive conventional endoscopic accessories therethrough without contaminating the endo- 65 scope itself during the endoscopic procedure. The sheath 26 has a distal end portion 21 that includes an endcap 34 having
a transparent window 28 positioned to cover the viewing window 19 at the insertion tube's distal end 20 when the sheath assembly is installed. The endcap 34 formed of a relatively rigid material and is sealably secured to the sheath's distal end portion 21.
Endoscopic sheath assemblies used with insertion tubes that have a complex cross-sectional shape, such as C-shaped, often must have an endcap with a corresponding complex cross-sectional shape to snugly fit over the insertion tube's distal end 20. The complex-shaped endcap can be a costly and laborious component to manufacture for the sheath assembly. Other thin-walled components that would be required to have a complex shape if used with endoscopic sheaths or other medical devices having complex shapes may include precision detent mechanisms and short-pitched threads that are manufactured with the necessary accuracy and tolerances required for intricate medical devices.
U.S. Pat. No. 5,443,781 to Saab teaches a method of forming a disposable sheath with an. optically transparent window that is integral with the sheath. The transparent window is formed so as to maintain a thin-walled, relatively inelastic, yet flexible sheath for an optical medical instrument. Saab teaches forming the sheath by heating a sheet or film of optically transparent polymeric material until the material's viscosity is substantially reduced and the film is malleable. As shown in FIG. 2, a mandrel 35 having a relatively simply cylindrical shape is thrust into the heated film 37 causing the film to stretch and to generally conform to the mandrel's shape. As a result, the heated film 37 is formed into a closed-end sheath 39 having sidewalk 36, a flange or collar 38 at its open proximal end 40, and a closed distal end 42. The mandrel 35 is selected based upon its simple geometrical shape to define the shape of the sheath 39. Accordingly, sheaths having different shapes and sizes are formed using different mandrels with the corresponding shapes and sizes.
The sheath and technique of making the sheath as discussed in Saab, however, results in the film being heated, stretched, and then cooled to remain the shape that generally corresponds to the mandrel's simple. The resulting sheath is limited to having a relatively simple geometrical shape. The method of Saab does not sufficiently allow for making complex-shaped components having close tolerances.
In the design of intrabody medical devices and accessories, including optical and non-optical devices, the need for components having a complex geometry has become more and more apparent. As an example, there is a need for highly-detailed components, such as endcaps, used with more complicated endoscopes. There is further a need for precisely manufactured catheter components or the like with accurately positioned detents or close-pitched threads. Other medical devices and accessories would be benefited by inexpensive thin-walled components with close tolerance demands.
SUMMARY OF THE INVENTION
The present invention provides a method capable of forming complex-shaped medical components in a heated polymeric film to provide thin-walled, durable, low-cost components that may be manufactured to close tolerances, which has been problematic in the prior art. In an exemplary embodiment of the present invention, the method of forming a thin-walled polymeric component includes the steps of heating a portion of the polymeric film to a malleable temperature, and using a forming tool to form a protrusion in the film's heated portion while the polymeric film is
malleable. The formed protrusion has an open proximal end, a distal end spaced apart from the proximal end, and sidewalls extending between the proximal and distal ends. The sidewalk and distal end define a first shape of the protrusion and also define an interior of the protrusion. The 5 forming tool has a shaping portion that may have a selected complex shape that is different than the protrusion's first shape. The method further includes the step of exerting a force radially inwardly on the protrusion and moving the protrusion into firm engagement with the forming tool's 10 shaping portion so the protrusion moves from the first shape to a second shape that closely conforms to the selected shape of the forming tool's shaping portion.
In the exemplary embodiment, the radially inward force exerted on the protrusion is achieved by creating a differ- 15 ential pressure so the pressure within the interior of the protrusion is less than the pressure outside the protrusion, thereby causing the protrusion's sidewalk to move inwardly to the second shape. In one embodiment, the step of exerting a differential pressure on the protrusion is achieved by 20 drawing a partial vacuum inside the protrusion. The partial vacuum may be drawn through the forming tool and through at least one vacuum port in the forming tool.
The present invention is also directed toward a polymeric medical component that may have a selected complex shape 25 that is made by the above-described process.
The present invention is also directed toward a vacuumforming tool capable of forming the medical component from a malleable polymeric protrusion. The vacuumforming tool includes a shaft having an air passageway and a forming portion, and the forming portion has a shape corresponding to the selected shape of the medical component. The forming portion has an outer surface and a plurality of apertures extending from the outer surface to the air passageway. The shaft is connectable to a vacuum source so the air passageway communicates with the vacuum source to allow the vacuum source to draw air through the apertures into the air passageway, thereby forming a partial vacuum within the malleable polymeric protrusion during the formation of the medical component.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an isometric view of a prior art endoscope and endoscopic sheath assembly.
FIG. 2 is an isometric view of a thermal plastic film of the prior art stretched by a mandrel.
FIG. 3 is an isometric view of a distal portion of an endoscopic sheath having a thin-walled, polymeric endcap formed in accordance with one embodiment of the present 5Q invention.
FIG. 4 is an isometric view of a heated thin-walled polymeric film with a funnel-shaped projection formed therein in accordance with one embodiment of the present invention and shown in an extended position, and a 55 complex-shaped forming tool is shown positioned in the protrusion and connected to a vacuum source.
FIG. 5 is an isometric view of the heated polymeric film of FIG. 4 with the projection shown in a contracted position in solid lines on the forming tool, and the projection is 60 shown in the extended position in phantom lines.
FIG. 6 is an isometric view of the protrusion of FIG. 5 shown with a distal portion of the protrusion being separated from a proximal to provide the selected thin-walled polymeric endcap with complex shape. 65
FIG. 7 is an isometric view of an alternate embodiment of the present invention with the thin-walled component having
close-pitched threads formed therein by a complex-shaped threaded forming tool shown in phantom lines.
FIG. 8 is an isometric view of an alternate embodiment of the present invention with the thin-walled component having detents formed therein by a forming tool shown in phantom lines.
DETAILED DESCRIPTION OF THE
A thin-walled polymeric medical component 50 having a complex shape made in accordance with one embodiment of the present invention is described herein with reference to the attached drawings. An exemplary embodiment of a thin-walled medical component 50, shown in FIG. 3, is attached to a distal end 52 of a sheath 54. The sheath 54 is shaped and sized to receive and isolate, as an example, an endoscope insertion tube 56 shown in phantom lines. The illustrated medical component 50 is a sheath endcap 51 that is sealably attached to the sheath's distal end 52 so as to provide a viewing window therein that allows clear imaging through the endoscope's imaging system 58, also shown in phantom lines.
The distal end portion 55 of the illustrated insertion tube 56 has a generally C-shaped cross-section and the endcap 51 is formed with a corresponding complex geometrical shape that closely conforms to the insertion tube's distal end portion. More specifically, the C-shaped cross-section of the illustrated endcap 51 is defined by a curved outer axial wall 60 that has. a selected radius and a curved inner axial wall 62 that is integrally connected to the outer axial wall 60. The inner axial wall 62 has a radius which is smaller than the radius of the outer axial wall 60. The inner axial wall 62 defines a receiving area 64 that is shaped and sized to receive one or more selected working channels 66, shown in phantom lines, extending through the sheath 54. As an example, the illustrated endoscopic sheath 54 includes a tubular working channel 66 that extends through the sheath and that is sealably connected to the sheath's distal end 52. The tubular working channel 56 snugly fits in the endcap's receiving area 64, while the distal end of the endoscope's insertion tube 56 is snugly received in the endcap 51 between the inner and outer walls. Accordingly, the thinwalled endcap 51 is provided with a complex geometrical shape that receives and retains the insertion tube's distal end therein and retains the working channel 66 adjacent to the distal end while minimizing the cross-sectional area of the sheath and insertion tube combination which is to be inserted into a patient.
While the medical component 50, such as the end cap 51, and the method of making the component is discussed herein with reference to an endoscopic sheath, the method of the present invention is equally applicable to medical components used in procedures for medical devices other than endoscopic procedures. As an example, the medical component 50 in alternate embodiments are complex-shaped components used with catheters, optical medical equipment, and non-optical imaging medical equipment.
The thin-walled polymeric medical component 50 is made by forming a thin polymeric film into the desired shape. The preferred polymeric film used with the present invention is a thermoplastic material including PVC, acrylic, polycarbonate, polyethylene terephthalate, or other thermoplastic polyester material. The polymeric material used by the present invention allows for thin-walled medical components that are substantially inelastic, flexible, and have, high strength, and that can be easily, inexpensively, and
quickly manufactured. The polymeric film is selected so the medical component 50 has a wall thickness in the range of approximately 0.0005 to 0.015 inches, inclusive, and preferably in the range of approximately 0.0008 to 0.005 inches, inclusive.
In the exemplary embodiment illustrated in FIGS. 3,4 and 5, the medical component 50 is formed from a material that is optically transparent to visible light. The polymeric film, however, may be selected to provide a desired degree of transparency to electromagnetic radiation in the visible spectrum, or in the non-visible spectrum, e.g., radar, laser, or microwave. The polymeric film may also be selected, when needed, to provide a desired degree of transparency to sound waves, such as for use with ultrasound devices.
As best seen in FIG. 4, the polymeric film 68 is retained in a selected position so as to substantially define a plane. An interior portion of the film 68 is heated by a conventional heating device 72 to a selected malleable temperature to form a malleable, heated portion 70 of the film. The heated portion 70 is then stretched and formed into a protrusion 80, as discussed in greater detail below, by a forming tool 74. The forming tool 74 has a contoured shaping portion 78 with a complex geometrical shape that corresponds to the shape of the endcap or other medical component to be formed. In the illustrated embodiment, the forming tool's shaping portion 78 has a C-shaped cross-section with curved inner and outer surfaces that correspond to the endcap's C-shaped cross-section discussed above.
After the film's heated portion 70 is malleable, the forming tool's shaping portion 78 is pressed into the heated portion generally perpendicular to the plane defined by the film 68, and the forming tool stretches the heated portion away from the plane to form a thin-walled, generally funnelshaped protrusion 80.
The protrusion 80 has an open proximal end 82, a closed distal end 84 spaced away from the open proximal end and sidewalk 86 extending between the proximal and distal ends. The closed distal end 84 and the sidewalk 86 define an interior 88 of the protrusion 80 that contains the forming tool's shaping portion 78 as the protrusion is formed.
As the protrusion 80 is formed, the protrusion has a generally tubular shape that only roughly conforms to the outer shape of the forming tool's shaping portion 78, but the protrusion's sidewalk 86 do not yet closely conform to the complex shape of the forming tool's shaping portion. As an example, the protrusion's sidewalk 86 conform to the shaping portion's outer curved surface but do not conform to the shaping portion's inner curved surface, such that the protrusion has a generally D-shaped cross-section, rather than the C-shaped cross-section of the shaping portion.
While still malleable, the protrusion's sidewalk 86 and the closed distal end 84 are then brought into firm and close engagement with the forming tool's shaping portion 78, as shown in FIG. 5, thereby closely conforming to the shaping portion's complex geometrical shape. In the exemplary embodiment, the protrusion 80 is brought into firm engagement with the shaping portion 78 by drawing a partial vacuum within the projection's interior 88. The partial vacuum causes a differential pressure in the protrusion that is exerted on the sidewalk 86, so the pressure within the protrusion is less than the pressure outside of the protrusion. Accordingly, the partial vacuum moves the protrusion's sidewalk 86 against the forming tool's shaping portion 78 to achieve the selected complex geometrical shape for the medical component 50. After the protrusion 80 has moved to the contracted position and has cooled from the malleable
temperature, the forming tool 74 is removed from the protrusion's interior 88 and the protrusion remains in the contracted position.
As best seen in FIGS. 4 and 5, the forming tool 74 is a
5 partially hollow member with at least one and preferably a plurality of vacuum ports 89 formed in the shaping portion 78. The forming tool 74 is connected to a conventional vacuum source 90 by a vacuum line 92. The vacuum source is adapted to draw air into the forming tool's shaping portion
1° 78 through the vacuum ports 89, thereby creating the partial vacuum within the interior.
As best seen in FIG. 6, after the forming tool 74 is removed, a distal portion of the protrusion 80, which has the complex-shape formed therein, is cut or otherwise separated
15 from the remaining portion of the protrusion, and that distal portion is the thin-walled polymeric medical component 50. The component 50, such as the illustrated C-shaped endcap 51, is then connected to the selected medical device, such as the distal end 52 of the endoscopic sheath 54, as illustrated
20 in FIG. 3.
In an alternate embodiment (not shown), the protrusion 80 is moved to the contracted position by exerting substantially uniform, exterior pressure on the protrusion in a radially
25 inward direction. As an example, the distal portion of the protrusion 80 and the forming tool's shaping portion 78 are positioned, as a unit, within a pneumatic pressure-generating device or other suitable device that exerts the exterior pressure, and the pressure generating device moves the
30 protrusion's sidewalk 86 from the expanded position to the contracted position and into close engagement with the forming tool's shaping portion 78. Accordingly, the radially inward directed forces on the protrusion 80 may be achieved by generating a vacuum in the protrusion's interior or by
35 creating a pressure external to the protrusion. The preferred method, however, is to use the partial vacuum within the protrusion's interior 88 because the partial vacuum does not disturb the temperature profile of the heated polymeric film. In addition to forming medical components having com
40 plex contoured shapes, such as the C-shape cross-sectional shape, the disclosed embodiment of the present invention also allows easy and inexpensive formation of a thin-walled, polymeric medical component 50 having close-pitched, accurately-located threads formed therein. As best seen in
45 FIG. 7, the forming tool 74 has a plurality of close-pitched threads 100 formed in the shaping portion 78. The forming tool 74 is pressed into the heated portion 70 of the polymeric film 68 when at malleable temperature, thereby forming the protrusion 80. Accordingly, the protrusion's sidewalk 86 are
50 generally adjacent to the threads 100 on the forming tool 74, but do not yet closely conform to the threads. The differential pressure is then generated in the protrusion's interior 88, moving the sidewalk 86 to the contracted position and into close engagement with the threads 100, thereby forming the
55 close-pitched, accurately positioned threads 102 in the protrusion. The forming tool 74 is then removed preferably by rotating it so the shaping portion 78 unscrews from the threads 102 formed in the protrusion 80.
The present invention also allows for easy and inexpen
60 sive formation of a thin-walled polymeric medical component 50, as shown in FIG. 8, having precisely located detents 120 formed in selected positions that correspond to detent receiving portions on a selected medical device, not shown. The medical component 50 may also have a concave-shaped
65 distal end 122 that follows the contour of the selected medical device. The medical component 50 illustrated in FIG. 8 is formed using a forming tool 74 with a shaping