Patent Application
20050033237
1. Field of the Invention
The present invention relates to medical systems and devices. More specifically, the present invention relates to catheter assemblies which include catheters and catheter adapters produced as a single part or produced as integrated assemblies of multiple parts. The invention further includes methods of injection molding and apparatus for producing such catheter assemblies from a single material and from multiple materials.
2. Description of Related Art
In an age of medicine in which injectable pharmaceuticals are ubiquitous in patient treatment regimens, indwelling catheters are a critical tool used in hospitals daily. Many medical treatments are dependent on devices and methods which allow the introduction of fluids into the body of a patient. Advances in catheter-related technologies have allowed a larger number of medical procedures to be performed intravenously instead of surgically. Indeed, procedures such as angioplasty and exploratory surgery may now be completed without making any incisions other than the puncture necessary to access a blood vessel and insert a catheter.
One type of commonly-used catheter is a peripheral intravenous catheter. These short, indwelling intravenous catheters are often used to provide an entry route for medications, fluid for hydration, and in some cases, for parenteral feeding. Such catheters are generally short in length, ranging from about one-half to about three inches in length. These catheters are generally made of flexible biocompatible materials. In some cases, these catheters additionally include a radiopaque compound such as barium sulfate to allow the location of the catheters to be tracked once inside the body.
Injection molding technologies have become very popular for use in producing plastic components, including many medical devices. The speed, efficiency, and consistency of these processes often results in time or cost savings to a manufacturer. Long, thin, tubular objects such as catheters have traditionally been very difficult to produce using such injection molding technologies. This difficulty arises for a number of reasons. First, the extremely high pressures involved in injection molding processes generally render proposed processes unusable. Typically, to provide a rapid fill, the molten plastic must be pressurized to several thousand pounds per square inch. As a result, when flows of the highly-pressurized plastic are allowed to enter the cavity of the injection mold, any imbalance in the flows, regardless of how slight, may deflect the core pin used to produce the tubular lumen of the component from its proper position. This often results in a damaged, and potentially unusable, product.
In answer to this problem, injection molding systems have been produced which have multiple gates through which the molten plastic is introduced. This results in multiple flows of molten plastic flowing into the mold. By providing multiple flows of molten plastic, imbalances in flow may generally be reduced. Despite this, however, flow imbalances may still occur. In many such cases these flow imbalances occur at least in part because the multiple flows may not enter the cavity in a simultaneous manner. In addition, imbalanced flows may occur when the flows of plastic are not evenly distributed about the core pin.
Another attempt to compensate for these factors has involved the production of injection molds and associated equipment which utilize a core pin which is placed in tension. Use of such systems and additional research have shown, however, that even in systems where the core pin is placed in high tension, imbalanced material flows may deflect the core pin, thus causing the part produced in the mold to have a number of undesirable characteristics. In many cases, these qualities include poor molecular orientation, excessive production of flash, internal stresses, and the like. In many cases, these flaws may be significant enough to impair the performance of the part or render it inoperative.
As a result of these difficulties, many thin tubular parts are produced using manufacturing processes such as extrusion which do not involve high-pressure injection-molding. Often, these alternate manufacturing procedures reduce ability of the producer to vary the shape, size, and overall geometry of the parts to be produced. As a result, thin tubular parts are first produced, and then in subsequent steps attached to other parts through separate processing steps. As discussed above, such post-production processing and the use of supplementary parts may be disadvantageous because of increased material and labor costs which may be associated with them.
Catheter assemblies comprising a catheter linked to a catheter adapter have typically been produced in a multi-step process such as those discussed above. Generally, the adapter portion is produced separately from the catheter portion and later attached. Following production of the components, the catheter is joined to the catheter adapter by threading the catheter into the adapter and attaching them to each other using a swage. In addition to this attachment step, the catheter portion may require a separate tipping process to provide a catheter with suitable tip geometry.
The apparatus of the present invention has been developed in response to the present state of the art, and in particular, in response to the problems and needs in the art that have not yet been fully solved by currently available catheter assemblies and catheter assembly manufacturing methods and equipment. Thus, it is an overall objective of the present invention to provide injection-molded catheter assemblies including a catheter adapter and a catheter tube, as well as methods of manufacture and associated equipment by which such injection-molded catheter assemblies may be produced.
In accordance with the invention as embodied and broadly described herein, catheter assemblies are provided which include a catheter and an adapter either produced as a single component or separately in such a fashion that the final product is an integrally-joined assembly. The invention further provides methods and associated apparatus for producing these catheter assemblies by injection molding. The catheter assemblies of the invention include a catheter adapter or “catheter hub” and a catheter tube or “cannula.” In some embodiments, the hub and cannula of the catheter assembly may be formed as a single component of a single material in a single step. In such a catheter assembly, the hub and cannula are continuous with each other, and are integrally formed. The invention includes methods and apparatus for producing such single-material one-piece catheter assemblies.
In other embodiments of the invention, the catheter assembly comprises a hub portion and a cannula portion which may be produced of different materials and in separate steps, but which are integrally attached to each other in the completed catheter assembly. This may generally involve producing one of the components first, and then subsequently overmolding the second component onto the first. In some embodiments, the hub is produced first and the catheter is subsequently overmolded. In others, the catheter portion is produced first and the hub is later molded about the catheter. The catheter assemblies of the invention may also be produced using injection molding methods in which the catheter and hub portions are produced substantially simultaneously.
In some embodiments, the hub portion and the cannula portion are attached to each other by bonds formed between the materials used to produce each portion during manufacturing. These bonds generally include non-covalent bonds such as electrostatic bonds, van der Waals interactions, or other chemical interactions or bonds. In addition, the hub portion and the cannula portion may be attached to each other by physical entanglement of the polymers used in the separate components.
In other embodiments, the hub portion and the cannula portion are attached to each other using a mechanical interlock interface created during manufacture of the components. In still other embodiments, the hub portion is attached to the cannula portion using a combination of the bonding of the materials, physical interaction of the polymers used in the components, and mechanical interlocking interfaces.
In the catheter assemblies of the invention, the hub portion of the catheter assembly is a generally tubular component used as an interface between the cannula portion and devices for introducing or withdrawing fluid from the body such as syringes. The hub portion includes a hub barrel, hub base, and a hub adapter. The hub barrel is the main tubular body of the catheter hub and includes a lumen for receiving a tip portion of a fluid withdrawal/introduction device such as a syringe or IV line, and for conveyance of fluid. The hub barrel is generally tapered internally and externally. The hub base protrudes from an end of the hub barrel in the form of a ridge. This ridge may further include flanges such as luer threads for locking the catheter assembly to an external device such as a syringe or an IV line in a secure, and often sealed, fashion. The flanges may also assist a user in grasping the hub barrel of the catheter assemblies of the invention.
The present invention also provides a method and related apparatus by which the single-material, single-part catheter assemblies of the invention may be manufactured through the use of injection molding processes. The invention provides a mold used for the injection molding of a single-material catheter assembly. This mold generally includes an A-side and a B-side which mate to form a cavity shaped to form a catheter assembly. The mold is configured to be coupled to a nozzle of a plastic injection system in order to receive a flow of molten plastic which is channeled to the cavity to form the catheter assembly. The A-side may have a cavity plate for receiving the flow or flows of molten plastic and for forming the catheter assembly. The B-side of the mold may have a floating plate for transmitting a flow or flows of molten plastic, as well as a base plate.
As briefly discussed above, the sides of the mold are configured to mate to produce a cavity into which plastic can be injected to form the catheter assembly. The cavity may be sealed in plastic-tight fashion such that gas can escape the cavity during injection, but plastic is unable to escape. A core pin generally protrudes into the cavity from the floating and base plates such that the cavity has a generally annular shape. The cavity may have a hub portion in which the hub is formed, and a catheter portion in which the catheter is formed. In molds for producing the single-material single-part catheter assemblies of the invention, the hub portions and catheter portions of the mold may be continuous with each other. The core pin may traverse the hub and catheter portions of the mold to define the lumen of the hub and the catheter. The cavity of the mold is further configured to provide a proper geometry to the tip of the completed catheter assembly.
The invention also provides methods and apparatus for forming the multi-material integrated catheter assemblies of the invention. Such methods include methods for producing an integrated two-piece (and hence potentially two-material) catheter assembly using two-shot or multi-shot injection molding techniques or using simple overmolding techniques. In each case, the mold is similar to that described above, with the exception that the cavity is configured to allow individual molding of either the catheter portion or the hub portion of the assembly first, and then to subsequently allow the molding of the remaining component or components about the first-molded part. This may be accomplished in a two-shot or multi-shot injection molding process by providing a modular cavity which segregates regions of the cavity until a first component has been molded, and then opens the remainder of the cavity to allow overmolding of the remaining part.
Similarly, overmolding techniques of providing a separate mold for the first component and a second mold configured to retain the molded first component and overmold the remaining one are taught. With overmolding, as above, either the catheter portion or the hub portion may be produced first, and then the remaining part subsequently overmolded about the first-produced part.
The molds of the invention may form the catheter assembly with a high degree of molecular alignment along its length by providing a comparatively even flow of molten plastic around the circumference of the annular cavity defining the catheter assembly. Such an even flow may be provided by providing a plurality of flows that converge and flow into the annular cavity substantially simultaneously.
In one example of this, floating plates of the molds of the invention may have a pair of substantially symmetrical flow paths through which molten plastic is able to travel from the nozzle to the hub portion of the cavity. Opposite sides of the hub portion of the cavity may have a gate region through which molten plastic emerges from the flow paths to enter the hub region of the cavity. The molten plastic may then travel through the hub in a substantially uniform manner. The molten plastic may thus fill the hub in a manner such that it is substantially evenly distributed about a circumference of the hub. From the hub, the plastic may enter the catheter portion of the cavity and move to the tip portion while maintaining an even distribution about the circumference of the cavity.
Thus, the two flows of molten plastic may reach the end of the tip portion simultaneously. Since molecules of molten plastic tend to align themselves with the direction in which the plastic flows, the result is a high degree of molecular alignment along the length of the catheter assembly, including the tip. The strength of the molded plastic part is generally greatest in the direction with which the molecules are aligned. Thus, the catheter assembly of the invention has a comparatively high resistance to axial tension and compression. In alternate methods, the molten plastic may be injected into the cavity such that it first fills the catheter portion of the cavity and then proceeds to fill the hub portion.
The use of even flows of molten plastic makes it unnecessary to employ extra steps to protect the core pin against bending. Some traditional injection molding processes utilize an external mechanism, such as a hydraulically operated clamp, to tension a core pin or other protrusion to form a bore in the injection molded part. Such mechanisms add to the complexity of the molding apparatus and increase the cycle time of the injection molding process, thereby increasing the cost of the injection molded parts. The present invention avoids this requirement, thus avoiding cost and reducing production time requirements,
After the plastic has been injected into the cavity, forming the catheter assembly, the mold may be disassembled to allow removal of the completed catheter assembly product. This often includes moving the B-side of the mold away from the A-side to expose the molded part. The completed catheter assembly may then be ejected from the core pin and cavity manually, by ejector pins, stripper plates, robotic removal, or other equipment and techniques known to one of ordinary skill in the art.
The cavity of the mold may be shaped such that the catheter assembly produced therein may have accurate tip geometry that promotes easier and more comfortable insertion of the catheter into a blood vessel. The catheter assembly may be rapidly and inexpensively manufactured by the injection molding process described above, without the need for separate attachment or tipping operations. Consequently, the catheter assembly and method of the present invention may contribute to the comfort, reliability, and cost effectiveness of medical care.
These and other objects, features, and advantages of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.
In order that the manner in which the above-recited and other advantages and objects of the invention are obtained will be readily understood, a more particular description of the invention briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments of the invention and are not therefore to be considered to be limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:
The presently preferred embodiments of the present invention will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. It will be readily understood that the components of the present invention, as generally described and illustrated in the figures herein, could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of the embodiments of the apparatus, system, and method of the present invention, as represented in
The present invention includes advances in catheter design, material selection, and mold design which combine to enable production of a catheter assembly, including a catheter hub and a catheter tube, using injection-molding technologies. The invention further provides catheters which may be constructed using a single material, or using multiple materials. Among others, the invention provides single-material, bi-material, and tri-material integrally formed catheter assemblies and methods and molds for their DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The presently preferred embodiments of the present invention will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. It will be readily understood that the components of the present invention, as generally described and illustrated in the figures herein, could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of the embodiments of the apparatus, system, and method of the present invention, as represented in
The present invention includes advances in catheter design, material selection, and mold design which combine to enable production of a catheter assembly, including a catheter hub and a catheter tube, using injection-molding technologies. The invention further provides catheters which may be constructed using a single material, or using multiple materials. Among others, the invention provides single-material, bi-material, and tri-material integrally formed catheter assemblies and methods and molds for their the hub portion 20 of the assembly 10 of
The hub 20 of the catheter assembly 10 of
The hub portion 20 may further include a gate region 34 which corresponds to the region through which molten plastic was introduced into the mold used to form the catheter assembly 10. The position of this gate region 34 may be widely varied within the scope of the invention. In some embodiments of the catheter assembly 10, the hub 20 may include at least one gate region 34. In other embodiments of the catheter assembly 10, the hub 20 includes two or more such gate regions 34, indicating multiple flows of molten plastic into the mold used to form the catheter assembly 10. The gate regions 34 are generally positioned on the hub 20 of the assembly 10, and may be specifically located on the hub barrel 26, hub base 32, or luer threads 33. These gated regions 34 may appear as small bumps, small depressions, or even as surface irregularities on the surface of the hub 20 which are byproducts of the process of stripping the catheter assembly 10 from the mold used to produce it. The position of the gated regions 34 may be specified to optimize the function and appearance of the catheter assembly 10. The function and origin of these gate regions 34 and the mold used to produce the catheter assembly 10 will be described in greater detail below.
The hub 20 of the catheter assembly 10 further includes a hub barrel 26 which extends in a longitudinal direction 12 from the hub base 32. At an end of the hub barrel 26 opposite the hub base 32, the hub region 20 joins a transition region 42 which has a shape that links the generally wider catheter hub region 20 to the catheter region 50 of the catheter assembly 10. The hub portion 20 further includes a hub lumen (not shown) that runs the length of the hub portion 20, and which is continuous with an interior lumen 68 of the catheter region 20.
The catheter region 50 of the catheter assembly 10 joins the hub portion 20 at the transition region 42. The catheter region 50 extends outwardly in a longitudinal direction 12 from the transition region 42 in the form of a narrow tubular catheter cannula 56. The catheter 56 is integrally formed with the hub region 20 of the catheter assembly 10. The catheter portion 50 includes a catheter lumen 68 which is in fluid communication with the lumen (not shown) of the hub portion 20. The length of the catheter 56 of the assembly 10 may be varied widely within the scope of the invention, but is generally from about one-half to about three inches in length. The catheter 50 terminates in a tip 62. The geometry of the tip 62 may be varied within the scope of the invention.
The tip 62 of the cannula 56 of the catheter 50 may be configured to have any of a variety of geometries to facilitate its insertion into the bloodstream of a patient. The catheter assembly 10 is generally inserted into a bloodstream by placing the catheter assembly 10 over a needle, catheter introducer or other similar device, pushing the needle through the skin of the patient, and withdrawing the needle, thus leaving the catheter assembly 10 in place for use in withdrawing fluid or introducing fluid into the bloodstream of the patient.
The catheter assembly 10 may be designed and produced such that the hub portion 20 and the catheter portion 50 both include at least a slight draft angle, so that the hub portion 20 and the catheter portion 50 are each slightly wider at their proximal ends than at their distal ends. This draft angle may be varied to aid in steps of the production of the catheter assembly 10, including removal of the finished product from a mold.
Referring now to
As above, the hub portion 120 may include a gate region 134. In other embodiments of the catheter assembly 110, the hub 120 includes two or more such gate regions 134. In this embodiment, the gate region 34 is shown positioned on the hub base 132 of the assembly 110. The catheter portion 150 of the catheter assembly 110 may also include a gate region 176 on its surface. In some embodiments, the gate region 176 may be positioned on the attachment sleeve 174 of the catheter region 150, as shown in
The joint 152 of the catheter assembly 110 is shown in cross-sectional detail in
The joint 152 may be produced relying upon a variety of factors to produce a strong, sealed joint 152. First, the materials used to produce the hub and catheter portions 120, 150 may be selected such that the materials will adhere to each other during the manufacturing process. Examples of materials having suitable characteristics will be discussed in greater detail below. As discussed briefly above, the materials selected for the hub and catheter portions 120, 150 may be selected to give each individual portion a physical property that may be desirable. In some embodiments, it may be desirable to produce the hub portion 120 out of a material demonstrating rigidity to assist in attaching the assembly 110 to other equipment. In addition, in some embodiments, it may be desirable to produce the catheter portion 150 out of a substantially flexible material to allow insertion and use of the catheter 150 without damage to the catheter 150 or injury to the circulatory system of the patient.
As above, the catheter assembly 110 may be designed and produced such that the hub portion 120 and the catheter portion 150 both include at least a slight draft angle, so that the hub portion 120 and the catheter portion 150 are each slightly wider at their proximal ends than at their distal ends. This draft angle may be varied to aid in steps of the production of the catheter assembly 110, including removal of the finished product from a mold.
Referring now to
The strength of the joint 152 of the catheter assembly 110 of
The interface 154 of the joint 152 of the catheter assembly 110 may be configured to provide a tensile strength zone 155a and a shear strength zone 155b. Specifically, the tensile strength zone 155a may be defined as the surface area of the ring shown at the interface 154. This surface area may be varied by extending or reducing the radii of the interior and exterior of the hub portion 120. When the hub 120 and the catheter 150 are made of compounds which chemically bond, e.g. via electrostatic bonds, van der Waals interactions, or other chemical interactions or bonds; or when the hub 120 and catheter 150 are made of compounds such as polymers which my physically entangle, this may increase or reduce the tensile strength of the joint 152.
The shear strength zone 155b is the surface area of the sleeve projecting in a longitudinal direction 12 from the tensile strength zone 155a. The area of the shear strength zone 155b may similarly be varied by extending the longitudinal length of the shear strength zone 155b, or by expanding its radius. When the hub 120 and the catheter portion 150 are made of compounds which bond in any of the manners described above, this may increase or decrease the strength of the joint 152. These principles may be applied in many of the embodiments of the two-piece integrated catheter assemblies of the invention to provide adequate tensile and shear strength with various pairs of compounds used to form the individual components of the catheter assembly 110.
The catheter portion 250 of the assembly 210 has a catheter attachment face 274 configured to be joined to the hub adapter face 238. The catheter portion 250 further includes a gate region 276 positioned on the transition region 242. In this embodiment of the assembly 210, the attachment of the catheter attachment face 274 and the hub adapter face 238 forms a butt-joint 252. In this embodiment of the catheter assembly 210, the butt-joint 252 includes an interface 254 having a surface area which may be smaller than that of the catheter assembly 110 of
Referring now to
The hub adapter face 338 of the catheter assembly 310 is configured as an internal interlock sleeve joint to allow use of a relatively short attachment sleeve 374. Despite their short length, the hub adapter face 338 and the attachment sleeve 374 form an interface 354 having a relatively large surface area because both the inward-facing and outward-facing surfaces of the attachment sleeve 374 interface with the hub adapter face 338. Various other structural conformations of the attachment sleeve 374 and the hub adapter 338 may be used within the scope of the invention to provide a large surface area for the interface 354 of the joint 352.
Referring now to
The strength of the joints 152, 252, 352 of embodiments of the invention shown in
Referring now to
The catheter portion 450 of the assembly 410 includes an attachment sleeve 474 extending from the transition region 442. In this embodiment, the attachment sleeve 474 includes a gate region 476. The catheter assembly 410 of
As in previous embodiments, the catheter portion 450 of the assembly 410 further includes a catheter cannula 456, also extending from the transition region 442, which terminates in a tip 462. The catheter portion 450 also has a lumen 468 which is continuous with the lumen 446 of the hub portion 420 of the catheter assembly 410 when assembled.
Referring next to
The catheter portion 550 of the assembly 510 includes an attachment sleeve 574 extending from the transition region 542. The catheter portion 550 here includes two gate regions 576 (only one of which is visible) which resulted from the production methods used to produce in the assembly 510. The catheter assembly 510 of
Referring next to
In this embodiment of the catheter assemblies of the invention, the catheter assembly 910 further comprises a flexible pivot portion 980. The flexible pivot 980 is positioned between the hub 920 and the catheter 950 and interfaces with them at joints 952a, 952b. The flexible pivot 980 is configured to allow manipulation and movement of the hub portion 920 of the catheter assembly 910 while minimizing disturbance or displacement of the catheter portion 950 of the catheter assembly 910.
In the catheter assembly 910 of
The three-component configuration of the catheter assembly 910 adds further flexibility in the design of the catheter assemblies of the invention. Specifically, in the two-component assemblies 110, 210, 310, 410, and 510 discussed previously, the materials of the hub and catheter portions were generally selected for their ability to bind to each other. In the three-component configuration of the catheter assembly 910, the materials of the hub 920 and catheter 950 may not bond well to each other, but may instead bond well to the material used to form the flexible pivot 980 of the assembly 910.
The pivot 980 of the catheter assembly 910 of
As discussed previously, the size and geometry of the interfaces 954a, 954b may be varied to vary the strength of the bond. In addition, the specific type of mechanical interlock used in catheter assemblies such as 410, 510, and 910 may be varied by one of skill in the art. Those of skill in the art will recognize that numerous other catheter assemblies may be made within the scope of the present invention.
Various materials have been tested for suitability for use in producing the catheter assemblies of the invention. Several components have been tested for use in producing the single-part, single-material catheter assemblies such as 10, and the catheter portions of multi-part catheter assemblies such as 110, 210, 310, 410, 510, and 910. These complete catheter assemblies and catheter portions have been produced of polyurethane materials. In specific embodiments of the catheter assemblies of the invention, a low viscosity polyurethane is desirable. In some specific embodiments of the invention, a proprietary polyurethane Vialon™ is used.
Vialon™ is a polyurethane biomaterial used in catheter products. Vialon™ may be molded to produce a smooth surface which reduces catheter drag during insertion and prevents catheter-related thrombosis during use as an indwelling catheter device. Catheter products produced with Vialon™ soften after insertion into the circulatory system of a patient, allowing the catheter to better conform to the natural shape and form of the blood vessel into which it has been inserted. This helps to reduce injury to or irritation of the lining of the vessel.
In specific embodiments of the invention, the catheter portion 150 is produced using Vialon™ modified to reduce its viscosity. The process used to modify the viscosity of the Vialon™ may include reducing the molecular weight of the Vialon™ using multiple pass extrusion.
Other materials are also suitable for use in producing the single-part single-material catheter assemblies (such as 10 of
Several materials have been tested for use in the hub and catheter portions of the catheter assemblies (such as 110, 210, 310, 410, 510, and 910) of the invention. In some embodiments, the hub portion has been produced of polycarbonate and polyurethane materials. In addition to these materials, however, PET, nylon 12 homopolymer, and nylon 12 copolymer have been tested. The resulting experimental data indicates that they would be suitable for use in producing the catheter hub 120 of the assemblies 110 of the invention. Specifically, such materials provide a relatively rigid base to allow for secure attachment of the assembly 110 to outside apparatus.
In addition to the above materials, other materials have been tested for use in the hub and catheter portions of the catheter assemblies (such as 110, 210, 310, 410, 510, and 910) of the invention. In some embodiments, the hub portion may be produced of materials such as nylon, polymethyl-methyacrylate, polyester, acrylo-nitrile butadiene styrene, polyurethane, polyethylene, polypropylene, polyether block amides (“PEBAX”), poly vinyl chloride, polycarbonate, acrylic, polystyrene, and polymethylpentene.
The catheter assemblies of the invention may alternatively be produced using reaction injection molding technologies, in which prepolymers are injected into the mold instead of using molten polymeric materials. After injection, the prepolymers polymerize and cure to form the completed catheter assemblies of the invention. Reaction injection molding processes often operate at temperatures lower than those required for traditional injection molding technologies. This may also reduce the energy expenditures required to produce the catheter assemblies of the invention. In addition, since prepolymers are generally less viscous than molten polymers, they may flow more easily into molds, reducing tooling costs. This may make reaction injection molding useful in catheter assembly designs using complex joints or tip geometries. Reaction injection molding cycle times are also generally short, resulting in cycle times of less than about one minute. Materials suitable in reaction injection molding methods generally include polyurethanes, nylons, and other fast-reacting prepolymers. Generally, amine-extended polymers form more quickly, while diols may require up to 60 seconds for sufficient polymerization.
Material bond strength studies were conducted using various combinations of several of the above-listed materials to produce catheter assemblies according to the catheter design of
Although predicted failure loads for the first two materials appear less favorable, catheter designs providing a larger interface/contact area may likely be suitable. In addition, it is believed that Vialon™ having less of the radiopaque compound (here barium sulfate), and thus, adhesion will be improved.
Additional data were obtained from materials testing studies. The data obtained is shown in Table 2 below.
In these materials testing studies, catheters were produced with either Vialon™ or Vialon™ including a radiopaque compound, referred to herein as “filled Vialon™” and a second adapter material. These catheters were then subjected to pull-testing to test adhesion quality. It is believed that the stess at failure exhibits sufficient adhesion to resist a 3-pound pullout force.
The following discussion returns to the catheter assembly 10 of
Referring now to
The mold 610 may have an A-side 612 that may be coupled to an injection nozzle of the injection molding machine. In embodiments in which the nozzle is coupled to the A-side 612, the nozzle is attached so as to be continuous with an orifice 650a configured to receive molten plastic. The molten plastic may then be channeled to the cavities 660 of the A-side 612 via a region 650b continuous with the orifice 650a which directs the molten plastic to runner pathways 648. The mold 610 is configured to receive molten plastic from such a nozzle. The mold 610 may also have a B-side 614 that is configured to translate with respect to the A-side 612.
The B-side 614 of the mold 610 may have a floating plate 624 slidably mounted with respect to a base plate 622. The base plate 622 may remain fixed in place, while the floating plate 624 may be configured to move a limited distance away from the base plate 622. The motion of the floating plate 624 with respect to the base plate 622 may be used to help remove a completed catheter assembly (not shown) from the mold 610. The base plate 622 may be configured to retain core pins 640 which may travel through the floating plate 624 and extend from the B-side 614 of the mold 610 into the A-side 612 of the mold 610 when the sides 612, 614 are mated for use. The floating plate 624 may additionally include runner paths 648 traveling away from a point 650b at which the runner paths 648 interface with the orifice 650a when the mold 610 is assembled. The floating plate 624 may further include core pins 640 extending from the base plate 622 through the floating plate 624. The floating plate 624 may additionally include a plate seal 632 to isolate the center of the mold 610 where the actual molding occurs.
The B-side 614 of the mold 610 may be configured to translate relative to the A-side 612 to allow selective mating or disengagement of the sides 612, 614. The A-side 612 may include a cavity plate 626. The A-side 612 of the mold 610 includes individual cavities 660 which receive the core pins 640 and leave space for receiving the molten plastic that defines the shape of the one-piece catheter assembly produced by the mold 610. In addition, the cavity plate 626 may include alignment bores 618 for receiving the pins 616 extending from the B-side 614 of the mold 610. One of ordinary skill in the art will add additional plates if needed to provide or support components of the mold such as the core pins, or to add components such as ejector pins.
The orientation of the A-side 612 and the B-side 614 of the mold 610 may be stabilized by a set of leader pins 616 extending from either the floating plate 624 or the base plate 622. The leader pins 616 are configured to pass through alignment bores 618 present in plates such as the floating plate 624 (if mounted to the base plate 622), or the cavity plate 626. These pins 616 stabilize the mold 610 to provide proper alignment of the individual plates 622, 624, and 626. In addition, the pins 616 allow translation of the individual plates 622, 624, and 626 relative to each other.
In use, the floating plate 624 is mated to the cavity plate 626 such that the cavities 660 define the space needed to produce the catheter assembly. The nozzle of an injection molding machine is attached to the cavity plate 626 having an orifice 650a. The injection molding machine injects molten plastic into the mold. For purposes of this discussion, the nozzle is connected to the orifice 650a of the cavity plate 626, and injects molten plastic into the orifice 650a. Having traveled through the orifice 650a, the molten plastic emerges on the surface of the floating plate 624. The molten plastic then travels across the floating plate 624 along runner pathways 648. The runner pathways 648 convey the molten plastic toward the core pins 640 and the cavities 660.
Referring now to
One of skill in the art would understand that the runner pathways 648 shown in
Referring now to
The cavity plate of the A-side 612 of the mold 610 includes a cavity 660 having a hub cavity region 662 and a catheter cavity region 664. During use, a core pin 640 may extend from the B-side 614 of the mold 610 into the hub cavity region 662, and then into the catheter cavity region 664. The core pin 640 defines the lumen of the resulting catheter assembly 10. In
The core pin 640 extends from the floating plate 624 into the cavity 660 of the cavity plate 626 in a manner such that molten plastic is unable to escape from the cavity 660. The core pin 640 may even extend from the floating plate 624 in an airtight manner, if desired. Alternatively, the core pin 640 and the floating plate may be made to fit together such that air is able to pass between them to exit the cavity 660.
In some embodiments, it will be desirable to apply a vacuum to the cavity 660 prior to injection of molten plastic into the cavity 660. This evacuates air from the cavity 660 to allow the molten plastic to entirely fill the cavity 660. The cavity plate 626 may thus include a vacuum channel 644 accessible from outside the mold 610. Vacuum fittings (not shown) may be attached to such a vacuum channel to draw air out of the cavity 660. If desired, the core pin 640 or pilot 629 may even be made slightly porous to expedite the expulsion of air from the cavity 660. The vacuum fitting may be coupled to a vacuum source, such as a vacuum pump, as is known in the art. In each of these situations, however, the core pin 640 is able to slide relatively freely through the floating plate 624 into the cavity 660 of the cavity plate 626.
In some embodiments of the mold 610 of the invention, it may be desirable to provide mold components which may be rapidly and inexpensively replaced in order to speed repairs and reduce repair costs. Thus, in some embodiments, the mold 610 may include modular blocks such as a taper lock stripper block 628, a modular pilot block 629, and a modular catheter block 630. These modular blocks 628, 629, 630 are mounted such that they are positioned in the appropriate plates 622, 624, 626 of the mold 610. One such mounting configuration of the modular blocks 628, 629, and 630 is shown in
In one example, catheter block 630 may be substituted to allow the production of a catheter with a different length or width. The modular pilot block 629 may also be substituted to allow variation of the tip geometry of the catheter assembly produced by the mold. These modular blocks may be produced using methods known to one of ordinary skill in the art. The methods of the invention allow production of catheter assemblies having tip geometries equivalent to those previously produced using secondary tip processing methods.
The mold 610 may further include components to assist in the removal of the catheter assembly 10 from the mold 610, as well as components configured to remove any runner 648 formed during the process. Such removal methods include manual removal; mechanical removal by ejector pins, stripper plates, or robotic removal; or using other equipment and techniques known to one of ordinary skill in the art.
The hub and catheter cavity portions 662, 664 of the mold 610 form a cavity 660 into which a molten plastic may be injected. As illustrated in
In a next example, the invention further provides methods and apparatus for producing multi-part, and potentially multi-material integrated catheter assemblies. The following discussion proceeds with reference to the catheter assembly 110 of
In many of these methods of the invention, either the catheter portion 150 or the hub portion 120 of the assembly 110 is first injection molded, and then in a subsequent step, the remaining component is overmolded onto the previously produced part. In the method of the invention illustrated in
In addition to the above, in alternate embodiments of the invention, the overmolding process may be completed in a single mold which makes use of replaceable or rotating cores, rotating cavities on plates, or other similar technologies known to one of skill in the art in order to allow sequential production of the two components within a single mold. One mold suitable of functioning in such a fashion is shown in
Referring first to
The mold 710 includes an A-side 712 and a B-side 714 which mate as shown to provide a cavity 760 for injection molding a catheter hub portion. The B-side 714 includes a base plate 722, and a floating plate 724, while the A-side 712 includes a cavity plate 726. Other plates may be used in molds of the invention, as known in the art and described above, to add function to the mold. The plates 722, 724, 726 are aligned using leader pins 716 which extend from the base plate 722 through alignment bores 718 in the floating plate 724 and the cavity plate 726. In many embodiments of the mold 710 of the invention, the plates 724, 726 are slidable along the leader pins 716 such that the floating and cavity plates 724, 726 may be mated and separated during the steps of the method of the invention to provide a cavity 760 prior to injection of molten plastic, and then to allow removal of a molded component.
To produce a catheter hub 120 as shown in
Referring now to
Referring now to
The overmold 810 includes a cavity 860 including a hub cavity portion 862 and a catheter cavity portion 864. The hub cavity portion 862 is generally positioned in the cavity plate 826. According to variations of the method of the invention, the two-piece integrated catheter assemblies of the invention may be produced by first molding the catheter hub 120 and then using an overmold such as 810 to integrally mold a catheter portion to the hub 120. Thus, in
With the catheter hub 120 placed in the hub cavity portion 862, the hub adapter portion 138 of the catheter hub 120 may be configured to extend into the catheter cavity portion 864 of the overmold 810 such that when the catheter portion 150 is molded about the hub portion 120, a secure joint 152 is formed. As discussed above, such a joint 152 may be formed simply by providing an adequate interface between the two portions 120, 150 of the catheter assembly 110 to allow the materials of the hub portion 120 and the catheter portion 150 to adhere. In addition, in some embodiments such as catheter assemblies 410 and 510 of
Referring now to
The core pin 840 may be anchored to the base plate 822 in a variety of ways. In
The cavity plate 826 may include a distal anchor 844, into which the core pin 840 extends when the A-side 812 and the B-side 814 of the mold 810 are mated, as shown in
The tip 62 of the catheter assembly 110 may be formed within the distal anchor 844. In the alternative to complete formation of the tip 62 within the distal anchor 844, the tip 62 may be created in roughened form in the injection molding process and further shaped through subsequent processing. For example, the tip 62 may be injection molded with a tubular shape similar to that of the remainder of the catheter portion 150. The tip 62 may then be tapered through reheating and shaping, mechanical cutting, or other similar operations.
The distal end 870 and the distal anchor 844 may be made to fit together such that air is able to pass between the distal anchor 844 and the distal end 870 to exit the cavity 860. In some embodiments, it will be desirable to apply a vacuum to the cavity 860 prior to injection of molten plastic into the cavity 860. This evacuates air from the cavity 860 to allow the molten plastic to entirely fill the cavity 860. The cavity plate 826 may thus include a vacuum channel (not shown) accessible from outside the mold 810. Vacuum fittings (not shown) may be attached to such a vacuum channel on the cavity plate 826 to be in gaseous communication with the distal anchor 844 to draw air out of the cavity 860 through the distal anchor 844. If desired, the distal anchor 844 may even be made slightly porous to expedite the expulsion of air from the cavity 860. The vacuum fitting may be coupled to a vacuum source, such as a vacuum pump, as is known in the art.
As described previously, the mold 810 may incorporate ejector pins capable of extending into the cavity 860 to aid in removal of a completed catheter assembly 110 from the mold 810. Additionally, ejector pins may be provided to eject the runners and the sprue from the mold 810. The runners are solidified plastic pieces formed in the runner pathways 848, and the sprue is a solidified plastic piece formed in a sprue orifice (not shown) of the cavity plate 826. The runners and the sprue are ejected to avoid interference with the next injection cycle; they may be discarded or recycled for use in future injection cycles.
In addition, as is taught in the art, the catheter assembly 110 may include a slight draft angle on the external and internal surfaces to provide a slightly tapered shape. The draft angle may, for example, be on the order of 0.125°. In the alternative, the catheter assembly 110 may be molded with a draft angle of 0°. In any case, the mold 810 may be shaped to produce the desired, draft angle.
Referring now to
In some embodiments of the overmold 810 and method of the invention, it is desirable to provide multiple flows of molten plastic to the cavity 860 using multiple gate regions. In some specific embodiments, it is desirable to provide first and second flows of molten plastic to the cavity 860 to prevent deflection of the core pin 840. In some such embodiments, the first and second flows enter the cavity 860 from two sides of the catheter cavity region 864. In such embodiments, the first and second flows may converge in such a manner that the molten plastic is substantially evenly distributed about the circumference of the catheter cavity region 864. The molten plastic then flows through the catheter cavity region 864 substantially evenly. This helps the molten plastic to maintain a substantially even distribution about the core pin 840.
When such even flows are produced, the core pin 840 is under substantially the same pressure from all sides, and no significant deflection of the core pin 840 occurs. The molten plastic may continue to flow evenly to form the tip 62 of the catheter assembly 110. Injection molding machines used with the molds of the invention may be configured to rapidly step down the pressure of molten plastic within the molds of the invention such as 810 at a time selected to induce the molten plastic to stop flowing as soon as the catheter tip 62 of the catheter assembly 110 is formed.
These production methods may yield a catheter assembly 110 with a high degree of longitudinal molecular alignment, or molecular alignment in the longitudinal direction 12. Longitudinal molecular alignment may be desirable to prevent failure of the catheter assembly 110 under the stresses of insertion and subsequent use. The circumferential molecular alignment, or alignment in the lateral and transverse directions 14, 16, may be somewhat smaller than the longitudinal molecular alignment because the lateral and transverse directions 14, 16 are perpendicular to the direction in which molten plastic flows through the cavity 860 during the injection molding process.
The plastic that is used to form the catheter portion 150 may be optimized to the pressure and temperature characteristics of the molding process as well as to the geometry of the cavity 860. For example, the plastic may have a melt flow high enough to ensure that the entire cavity 860 is filled within a reasonable cycle time, yet low enough to avoid excessive flash or circulation within the cavity 860 after filling.
The method of the invention may be tuned such that the cavity 860 may be completely filled within a predetermined period of time. In some embodiments of the invention, such a time period may be from about 0.10 to about 0.20 seconds. After the cavity 860 has been filled, the molten plastic within the cavity 860 may be permitted to cool and solidify. Heat exchangers or the like, as known in the art, may be coupled to the mold 810 to facilitate cooling of the plastic within the cavity 860. Cooling may require a few seconds of time.
After the catheter portion 150 has been overmolded onto the hub portion 120 of the catheter assembly 110, the mold is partially disassembled to release the completed catheter assembly 110. In a first step of such disassembly, the core pin 840 is withdrawn from the A-side 812 of the overmold 810. Withdrawal of the core pin 840 generally results in removal of the completed catheter assembly 110 from the cavity 860, still attached to the core pin 840. The completed catheter assembly 110 may then be removed from the core pin using ejector pins, stripper blocks, or robotics which have been omitted from
Referring now to
The mold 1010 is shown in an exploded perspective view. The cavity plates 1026a, 1026b include cavities 1060a, 1060b. In this embodiment of the mold 1010, cavity plate 1026a is configured to produce a hub portion of a catheter assembly (not shown), and cavity plate 1026b is configured to accept the previously-molded hub portion and provide a cavity 1060b configured to overmold the catheter portion of a catheter assembly (not shown) onto the hub. One of skill in the art would understand that the mold could easily be configured to first produce the catheter portion and then allow overmolding of the hub portion of a catheter assembly within the scope of the invention.
In operation according to methods producing the hub portion first, the mold 1010 would receive a first injection of molten polymer or prepolymer into the first set of cavities 1060a. Upon filling and curing of the polymer, the plates of the mold 1026a, 1026b, 1024 would be separated. The base plate 1024 would then be rotated to position the completed hub portions (not shown) in alignment with cavities 1060b, after which the plates of the mold 1026a, 1026b, and 1024 would be mated again. When the plates are properly mated, molten polymer may be injected into both of the cavities 1060a, 1060b, thus simultaneously completing one set of catheter assemblies in cavities 1060b and forming the hub portions of another set in cavities 1060a.
The injection molding method and molds presented herein enable the production of catheter assemblies of the invention with a high degree of reliability, rapidity, and cost effectiveness. Through the use of a uniform distribution of molten plastic, the longitudinal molecular alignment of the plastic can be maintained, and excessive flash can be avoided.
The present invention may be embodied in other specific forms without departing from its structures, methods, or other essential characteristics as broadly described herein and claimed hereinafter. The described embodiments are to be considered in all respects only as illustrative, and not restrictive. The scope of the invention is, therefore, indicated by the appended claims, rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims are to be embraced within their scope.
