Background of the Invention

The subject invention generally relates to injection molding methods and devices formed thereby and more specifically relates to two-material, two-component devices formed by injection molding in which a first component acts as a part of the mold to produce a second component.

Those skilled in the art of injection molding are typically faced with a variety of injection molding problems which relate directly to a particular type of component it is desired to manufacture. Thus, various techniques have been developed in the past to be able to form various types of pro¬ ducts based on a given need. For example, U.S. Patent No. 4,507,258, to Aoki describes a method of forming polyethylene bottles in which a neck portion of the bottle is formed by in¬ jection molding an outer layer of the neck and then injection molding an inner layer and body portion of the bottle. The outer layer of the neck acts as a partial mold for the inner layer of the neck of the bottle. An advantage of using the outer layer of the neck as part of the mold for the inner layer is that no deviation occurs between the outer and inner layers of the neck of bottle. One feature of the device and method as taught by the Aoki reference is that the outer and inner layers of the neck of the bottle are not separable from one another after they have been formed.

Another technique of injection molding as described in U.S. Patent No. 4,155,972 to Hauser et al. This patent describes molding three separate plastic materials on top of

each other to produce a unitary molded product such as a multi¬ colored push button on a telephone or typewriter. According to the method described by Hauser et al., a first material having a high melting point is molded in a first form to form a first component. Subsequently, a generally lower melting point material is molded using the first component as a mold to form a subassembly. Finally, a lower melting point material is molded over the subassembly to produce the unitary molded pro¬ duct. One advantage of the method as described by Hauser et. al is by molding in the designated order is it possible to mold a single product having multiple plastic materials without having the materials bleed into one another. However, the method described by Hauser et al. is similar described by Aoki in that the final product is a single unitary product which cannot be separated after manufacture.

Similar techniques are taught by U.S. Patent No. 3,354,249 to Morln and U.S. Patent No. 3,387,282 to Bonis et al. In each of these methods, multicolored or multimaterialed parts are injection molded. However, the final product cannot be separated into its original individual parts after manufacture. In some instances it is desirable to be able to produce multiple parts that are closely fitting yet are capable of separation after manufacture. This invention is directed to such applications.

SU MA Y OF THE INVENTION

It is an object of the subject invention to provide a method for injection molding multiple component parts in which a first component acts as part of the mold to produce a second component.

It is another object of the subject invention to pro¬ vide a method for injection molding multiple component parts in which the components are maintainable in a fixed relationship with one another until the components are manually separated from one another.

It is yet another object of the subject invention to provide a method of -injection molding two component parts in which a sterile barrier is formed between first and second components of the parts during manufacture. It is still yet another object of the invention to provide two component parts formed by a two-material injection molding process in which the components are chemically bonded such that bond strength will be dependant upon varying con¬ centrations of slip agents added to one or more" ^' of the component plastic materials.

In accordance with the subject invention, a method of injection molding a two-component part is provided. The method includes the steps of: first, injection molding a first component in one cavity of a multicavity mold utilizing a dual-injection unit molding machine; second, mechanically transferring a transport plate containing the first component, to a second cavity in the machine; and third, injection molding a second component over the first component in the second cavity wherein the first component, a core, and the second cavity together act as a mold to produce the second component during the injection molding of the second component. The first and second components are manually separable from each other after the second component has been molded.

Other objects, advantages, and novel features of the present invention will become apparent from the following de¬ tailed description of the invention when considered in

conjunction with the accompanying drawings. Before explaining the embodiments of the invention in detail, it is to be under¬ stood that the invention is not limited in its application to the details of construction and to the arrangement of components as set forth in the following description, or as il¬ lustrated in the accompanying drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Furthermore, it is to be understood that the phraseology and terminology employed are for the purpose of description and should not be regarded as Limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG.l illustrates a cross-section of a mold in accordance with the subject invention in the closed position; and FIG.2 is a cross-section of a two-material mold in the open position to be run in a dual injection unit molding machine illustrating the preferred embodiment of the subject invention;

FlG.3 is a side view of a device manufactured in ac- cordance with the subject invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates a two-material injection mold 10 designed in accordance with the subject invention. The mold consists of a pair of support plates 12 that are used to sup- port the core retainer plate 14 and the cavity retainer plate 20. The core retainer plate 14 contains core inserts 16 and 18, sucker pin 40, sucker well bushing 44, and two leader

pins 38 located 180 degrees apart. A transfer plate 19 is attached to a shaft that is contained in the support plate 12 on the core half of the mold. Transfer plate 19 contains cavity inserts 30 and 32, two leader pin bushings 34 located 180 degrees apart, and a sucker well bushing 44. .Cavity re¬ tainer plate 2U contains cavity inserts 22 and 24, runners 26 and 28, and two leader pin bushings 42 located 180 degrees apart.

FIG. 2 illustrates the same mold illustrated in FIG. 1 in the open position depicting the first molded plastic component 46 and the second (finished) molded plastic component 48 sitting in cavity inserts 30 and 32 respectively. Also shown in FIG. 2 are molded runners 50 and 52 after they have been removed from the cavity retainer plate 20. The mold components used in FIG. 2 refer to the same mold components illustrated in FIG. 1. The method of the subject invention will now be described using the mold illustrated in FIGS. 1 and 2.

In accordance with the subject invention, a method of injection molding a two-component part is provided which in¬ cludes a first step of injection molding a first component 46 in a first cavity 22 of multicavity mold 10. This injection molding step is performed when the mold is in the closed position as illustrated in FIG.l. A first material is injected through runner 26 to till cavity 22 during the first step.

The mold is then opened by a hydraulic system (not shown) that is provided in a conventional injection molding machine. The hydraulic system causes the transfer plate 19 to be forced away from core retainer plate 14 to cause component b to be separated from core 16. The transfer plate is then rotated to cause component 46 to be positioned in alignment with core 18. The injection mold is then closed using leader

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pins 38 to properly align the transfer plate 19 with cavity re¬ tainer plate 20 and core retainer plate 14 and a second material that is semi-compatible with the first material is subsequently injected into runner 28 to form a second component 48 over the first component 46 in cavity 24. In accordance with the subject invention, the first component and the second cavity together act as a portion of the mold to form the second component. After the second component is formed, the hydraulic system again opens the mold and a knock-off device (not shown) knocks the completed two-component part out of the mold.

In the preferred embodiment, the first and second components will remain bonded together until the second component is removed from the first. It is possible to main¬ tain the first and second components in a fixed, yet separable, relationship with one another in accordance with the subject invention due to the materials chosen Tor each molding step. The choice of materials is a key feature of the subject in¬ vention. In order for the first component to act as a portion of the mold for the second component yet produce a two-component device in which the components are separable from one another, it is necessary to use "semi-compatible" materials.

In this context, the term "semi-compatible" means that only weak molecular bonds are formed between the two materials when one material is molded over the other. Such a weak molecular bond will allow components manufactured using semi-compatible materials, in accordance with the subject in¬ vention and to be maintainable in a fixed position relative to one another until force is used to separate the two components. The subject invention includes the provision that a second component will be weakly bonded to a first component

after injection molding of the second component over the first component. These weak bonds are used to maintain the second component in a fixed relation to the first component until forcefully separated. In the preferred embodiment, a force of 1.0 to 15.0 pounds is needed to separate the second component from the first.

In the preferred embodiment, it is necessary that the two materials chosen are such that the material used for the second component has a lower melting point than the material used for the first component. The need for the second material having a lower melting point than the first material has been recognized in the past as discussed above in the Background of the Invention. However, the need to use "semi-compatible" materials to form the weak molecular bonds as taught by the subject invention is considered to be unique.

A variety of materials may be chosen to form each of the first and second components and in some instances it may be desirable to add a slip agent to the base material chosen to enhance separability of the components after manufacture. Some materials that have been found to be useful for forming the first component include acrylonitrile butadiene styrene (ABS) and nylon 6,6. Other materials may be used provided that they have a high melting point relative to the material used for the second component, semi-compatibility with the second material and capable ot being injection molded. Materials that have been found to be useful in forming the second component in ac¬ cordance with the subject invention include low density

3 (0.91-0.94 g/cm. ) polyethylene and polypropylene.

As noted above, a slip agent may be added to the material used to form either the first or second component.

Useful slip agents include N,N ethylene bis stearamide, erucyl

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amide powder, and oleamide of alaic acid. The percentage of slip agent added to the material used to fabricate each component will affect the force required to separate the first and second components from each other after manufacture. In general, a higher concentration of slip agent will decrease the force required to separate the two components. It has been shown that a slip agent concentration of 0.5 to 1.5% will give an acceptable removal force for the application specified. In the preferred embodiment, 0.5% oleamide of alaic acid is used as the slip agent. If high concentrations of slip agent are used in the materials used to form the components during manu¬ facture, the components could actually separate spontaneously after manufacture. This may be desirable in some applications but highly undesirable in others. While the techniques described herein to form multiple component parts can be used for a wide variety of applications, these techniques are particularly desirable for forming low-cost parts in the medical industry. This is because a sterile barrier is inherently formed between the first and second components during the manufacturing process due to the high processing temperatures used during the injection molding process. This characteristic of the subject invention makes the techniques described herein extremely useful for forming multiple-component plastic devices for medical applications such as administration set components. In particular, a two-material molded, needle adapter/tip protector assembly can be easily manufactured using the techniques described herein. Needle adapters are typically attached to one end of the ad¬ ministration set tubing and are used to complete a sterile pathway for fluid introduction to a patient. A needle adapter consists of a male luer at one end of the adapter and a tubing

interface opposite the male luer. The luer portion of the needle adapter is typically covered with a tip protector after manufacture to maintain sterility of the luer and the fluid path of the administration set until it is desired to be used. Needle adapters and tip protectors manufactured in the past using conventional techniques have been produced on separate machines. Each tip protector is then manually placed on a needle adapter to form an unsterile assembly. One problem en¬ countered with assemblies manufactured using conventional techniques is that the fit between the needle adapter and tip protector is not as consistent as desired. The subject in¬ vention eliminates this problem by molding the tip protector directly onto the needle adapter. In order to more fully com¬ prehend the details of the subject invention-; an example is provided below illustrating the use of the subject invention to manufacture tip protectors and needle adapters.

EXAMPLE Needle adapters and tip protectors are manufactured in various embodiments of the subject inventions using the fol- lowing procedures:

Cyclolac CTB is dried at 18U degrees Fahrenheit for four hours to remove moisture from the material. The dried material is then introduced into the barrel of injection unit number one of a two injection unit molding machine. The Cyclolac CTB is plasticated at approximately 430 degrees Fahrenheit and then injected into a first cavity ,22, FIG. 2 with an injection pressure of approximately 500 pounds per square inch. The molded needle adapter 46 is allowed to cool in the cavity long enough for the plastic to solidify. The mold then opens, a transfer plate 19 is mechanically moved

clear of the leader pins 38 and rotated 180 degrees, thus positioning the needle adapter 46 in line with cavity 24. Sub¬ sequently the mold closes. Low density polyethylene containing 0.5 percent oleamide of alaic acid additive as a slip agent is plasticated at 305 degrees Fahrenheit and then injected into cavity 24 with an injection pressure of approximately 300 pounds per square inch thus, forming a tip protector over the needle adapter. The tip protector is cooled in the mold long enough to allow for the finished piece part to be ejected from the mold without distortion. The mold opens, the finished part is ejected, and the above process is then repeated.

It should be noted that during the injection phase of the two-material molding process, material is injected through injection units one and two into cavities 22 and -24 simul- taneously. This is necessary to minimize cycle time.

Other applications in which the technique described herein include forming tip protectors over medical spikes for insertion into a medical solution container, and friction tit- ting protector over-caps for injection molded commercial dis- pensers.

Although the invention has been described and illus¬ trated in detail, it is to be clearly understood that the same is by way of illustration and example only, and is not to be taken by way of limitation; the spirit and scope of this in- vention being limited only by the terms of the appended claims. Other objects, advantages, and novel features of the present invention will become apparent from the following de¬ tailed description of the invention when considered in con¬ junction with the accompanying drawings. Before explaining

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the embodiments of the invention in detail, it is to be under¬ stood that the invention is not limited in its application to the details of the construction and to the arrangement of com¬ ponents as set forth in the following description, or as il- lustrated in the accompanying drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Furthermore, it is to be understood that the phraseology and terminology employed are for the purpose of description and should not be regarded as limiting. Although the invention has been described and il¬ lustrated in detail, it is to be clearly understood that the same is by way of illustration and example only, and is not to be taken by way of limitation; the spirit and scope of this in¬ vention being limited only by the terms of the appended claims.