Abstract:
The invention includes a method of using a cap containing an internal thread form matching an external thread form on a flexible throat for a collapsible tube enclosing at least one contained product. Twisting the cap engages the internal thread form and the external thread form. These collectively urge the cap and the flexible throat to seal the contained product into the collapsible tube. Deforming the flexible throat through squeezing the collapsible tube dispenses essentially all the product. The collapsible tube may preferably include an external thread form on a flexible throat coupled to a flexible shoulder. The external thread form mates to a cap with an internal thread form urging the flexible throat to seal against the cap when the cap is twisted onto the flexible throat. The flexible throat and flexible shoulder flatten to dispense essentially all of the product.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to screw and cap mechanisms with particular application to forming collapsible tube dispensers. 
     2. Background Information 
     The earliest collapsible tube dispensers in the US patent database date from the early nineteenth century. Since that time, there has been continued innovation, leading to the various collapsible tube dispensers used for pharmaceuticals, personal care products, toothpaste, foods, artist&#39;s paints, glues, hazardous chemicals, grease products and viscous plastics, to name some of the more common uses of these tubes. As used herein, personal care products include, but are not limited to, cosmetics, facial care products, skin care products, and/or hair care products. 
     There are problems with the collapsible tube technologies of the prior art. They do not lend themselves both to being reusable and supporting the complete, controlled dispensing of their contents. As the term is used herein, reusable will refer to the capability to dispense small, or controlled, portions of the contents multiple times, perhaps on different occasions. Reusable may further refer to the capability to refill the contents multiple times. And reusable may further refer to a container, which can be cleaned, and refilled with differing contents. 
     One prior art collapsible tube dispenses all the tube&#39;s contents and is reuseable. The tube is not cylindrical but a two-sided pouch of soft plastic material. The tube has a mechanism of closing the throat, requiring no conventional screw and cap. The throat contains a soft plastic sheet insert that effectively sucks itself closed when pressure is released. This tube may be limited to applications in which there is no unexpected or forceful pressure applied to the tube. Example applications where it is not applicable include being packed in a suitcase, or purse, since the closure responds to finger pressure. The tube may also be limited to applications in which a high degree of barrier to the environment is not critical, such as pharmaceuticals, because the opening does not clean itself when closing except to the degree that it draws contents outside the tube to the inside of the tube. It may be undesirable for personal care products or other products demanding a high degree of aesthetic features, such as oversized caps allowing the tube to stand vertically. 
     There are some one-time use containers made essentially of a squeeze tube with a narrow end, which is cut to open the tube. All of the contents are then squeezed out, and the tube is discarded. These one-time use containers are not reusable, and represent a significant amount of overhead both for the manufacturer and for the ecology of people and systems, which must cope with these discarded containers. 
     With the exception of some one-time use containers, collapsible tube dispensers typically possess a rigid shoulder and a rigid throat. The rigid throat provides an exterior, rigid screw. This exterior rigid screw mates with a cap providing a matching interior screw pattern. When the cap is screwed onto the exterior screw of the throat, a seal is formed, which seals in the contents of the collapsible tube. 
     For the last century or two, screws have been built with either threads that taper away from the body, or remain of constant thickness. These screw threads will be referred to herein as open threads. Up until now, using these open thread screws requires that the throat of a collapsible tube be essentially rigid. An essentially rigid throat on a collapsible tube dispenser virtually guarantees that some of the tube contents will not readily leave the tube, causing the tube to waste some of its contents. The rigid shoulder further guarantees this waste. 
     The use of tubes for carrying food in sports and wilderness exploration environments is well-known. None on the market, however, are both reusable and completely collapsible. Thus, they do not dispense all their contents. A refillable tube that does dispense all its contents is especially desirable when food is otherwise scarce. 
       FIG. 1A  shows a prior art exterior screw  20  with a prior art external thread form  22 . The prior art external thread form  22  is shown in an expanded view through the following examples shown in  FIGS. 1B  and C with a matching internal thread form  24 . 
     There is a local coordinate system in  FIG. 1A , which will be used throughout this document. The z axis  10  extends through the center of the cylinder of the prior art exterior screw  20 , and is the central axis of the cylinder. The r axis  12  is the radial direction of the thread at a point, which, for the sake of discussion, is referred to as thread point  22  in FIG.  1 A. The n axis  14  is normal to the thread point  22 . When the screw is turned in the n direction, it engages more of the threads. 
     The engagement of an exterior screw thread and matching interior screw is shown in the expanded view of the prior art open screw thread  22  in  FIG. 1A . The expanded view is a cross-section of the threads taken in the plane of the z axis  10  and the r axis  12 . 
       FIG. 1B  shows an example of  FIG. 1A  using a standard acme thread for the external thread form  22  and the matching internal thread form  24 . A first external acme thread  22 - 1  matches the first internal acme thread  24 - 1 . A second external acme thread  22 - 2  with the second internal acme thread  24 - 2 . 
       FIG. 1C  shows an example of  FIG. 1A  using a standard buttress thread for the external thread form  22  and the matching internal thread form  24 . A first external buttress thread  22 - 3  matches the first internal buttress thread  24 - 3 . A second external buttress thread  22 - 4  with the second internal buttress thread  24 - 4 . 
       FIG. 1D  shows an example of  FIG. 1A  using a box thread for the external thread form  22  and the matching internal thread form  24 . A first external box thread  22 - 5  matches the first internal box thread  24 - 5 . A second external box thread  22 - 6  with the second internal box thread  24 - 6 . 
     One skilled in the art will recognize that  FIGS. 1B to 1D  show some of the many variations in open threads in use today. Other commonly used threads include various “V” shaped threads, as well as variations in angles of the walls, variations in the shape of the peaks and troughs of the threads. 
     To summarize, what is needed is a reusable collapsible tube, which can dispense essentially all of its contents. There is a need for reusable collapsible tubes which may be reopened to load the contents, particularly for food containers for use in travel and wilderness settings. 
     SUMMARY OF THE INVENTION 
     The invention includes a method of using a cap containing an internal thread form matching an external thread form on a flexible throat for a collapsible tube enclosing at least one contained product. Twisting the cap engages the internal thread form and the external thread form. These collectively urge the cap and the flexible throat to seal the contained product into the collapsible tube. Deforming the flexible throat through squeezing the collapsible tube dispenses essentially all of the contained product. 
     This method of using a collapsible tube permits dispensing essentially all of the contained product. The collapsible tube is also reusable, permitting its use in a variety of fields where today everyone is forced to waste the last part of the contained product. This is valuable in such diverse areas of application as pharmaceuticals, personal care products, toothpaste, foods, artist&#39;s paints, glues, hazardous chemicals, grease products, and viscous plastics. 
     The collapsible tube may preferably include an external thread form on a flexible throat coupled to a flexible shoulder mating to a collapsible tube body. The external thread form mates to a cap with an internal thread form urging the flexible throat to seal against the cap when the cap is twisted onto the flexible throat. The flexible throat and the flexible shoulder flatten with the collapsible tube body to dispense essentially all of the product. 
     The external thread form may preferably include at least two external threads. Each of the external threads may be external ridged threads. A ridged thread will refer to a thread that has its terminating end(s) bulge and/or bend. Various examples of ridged threads are shown in  FIGS. 2A to 3B . 
     The external thread form may be preferred to have at least one break in the external threads. The break may form a column, a canted column, or a fluted column. The fluted column may widen toward the flexible shoulder, or away from the flexible shoulder. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  shows a prior art exterior screw with a prior art external thread form; 
         FIG. 1B  shows a prior art example of  FIG. 1A  using a standard acme thread for the external thread form and the matching internal thread form; 
         FIG. 1C  shows a prior art example of  FIG. 1A  using a standard buttress thread for the external thread form and the matching internal thread form; 
         FIG. 1D  shows an example of  FIG. 1A  using a box thread for the external thread form and the matching internal thread form; 
         FIGS. 2A to 2I  show various matching ridged screw thread forms in the normal cross-section perspective; 
         FIGS. 3A and 3B  show aspects of the invention to further include collapsible tubes with a flexible throat made with at least one ridged thread exterior screw, and locked by a cap possessing at least one essentially rigid interior ridged thread screw; 
         FIG. 4A , the invention&#39;s collapsible tubes employ a shape including the flexible throat coupled to the flexible shoulder which mates to a collapsible tube body; 
         FIG. 4B , the invention&#39;s collapsible tubes employ a shape including the flexible throat coupled to the flexible shoulder, which mates to itself; 
         FIG. 4C , the flexible throat of  FIGS. 4A and 4B  including multiple external threads; 
         FIG. 5A  shows a top view of a collapsible tube as in  FIG. 4B  showing a first break forming a canted column; 
         FIG. 5B  shows a front view of the collapsible tube in  FIG. 5A  showing a first break and a second break; 
         FIG. 5C  shows a side view of the collapsible tube in  FIG. 5A  with the first break forming rectangular column; 
         FIG. 5D  shows a detail of  FIG. 5C  showing the flexible throat with a thread form including at least two, and in this case four open threads, which could be by way of example, external acme threads, external buttress threads, external V threads, external box threads, or combinations or modifications of these well known open threads; 
         FIG. 5E  shows the first break forming a fluted column expanding toward the flexible shoulder; 
         FIG. 5F  shows the first break  600  forming a fluted column expanding away from the flexible shoulder; 
         FIG. 5G  shows the collapsible tube as in  FIGS. 5B to 5D  with a cap; 
         FIG. 5H  shows the collapsible tube of  FIG. 5G  with the cap engaged and filled contents; 
         FIG. 5I  shows a cross section of  FIG. 5H  of the collapsible shoulder, flexible throat engaging the internal thread form and the external thread form using buttress threads; 
         FIG. 5J  shows the collapsible tube of  FIG. 5G  with a second cap engaged and filled with contents; 
         FIG. 5K  shows a cross section of  FIG. 5J  with the collapsible shoulder and flexible throat of  FIG. 5I  engaging a hollow version of the second cap; 
         FIG. 5L  shows a cross section of  FIG. 5J  with the collapsible shoulder and flexible throat of  FIG. 5I  engaging a filled version of the second cap; 
         FIGS. 6A to 6D  show the front view of a collapsible tube with none, one, two, and three breaks in its external threads, respectively; 
         FIGS. 7A to 7D  shows the front view of the collapsible tubes of  FIGS. 6A to 6D  partially deformed by squeezing the collapsible tube bodies and flexible shoulders; 
         FIGS. 8A to 8D  show the further squeezing of the collapsible tube of  FIGS. 6A and 7A , which has no breaks in its external threads; 
         FIGS. 8E to 8H  show the further squeezing of the collapsible tube of  FIGS. 6C and 7C , which has a first break and a second break; 
         FIGS. 9A to 9D  show the side view of the squeezing of the collapsible tube shown in  FIGS. 7C , and  8 E to  8 H, with the contained product being dispensed; and 
         FIGS. 10A and 10B  show two implementations of a collapsible tube including a flexible cone narrowing from the flexible throat away from the flexible shoulder and including a narrow opening for dispensing essentially all of a contained product. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 2A to 2I  show various matching ridged screw thread forms in the normal cross-section. In certain embodiments, the ridged thread form on the left side, known hereafter as the left ridged thread form, may be preferred as the internal thread form. The ridged thread form on the right side, known hereafter as the right ridged thread form, would be the external thread form. Alternatively, the right ridged thread form may be preferred as the internal thread form and the left ridged thread form would be the external thread form. A ridged thread will refer to a thread that has its terminating end(s) bulge and/or bend. 
     In  FIGS. 2D to 2I , the ridged thread form on either the left side or right side may not be immediately repeated. The thread pattern of the left ridged thread form is not immediately repeated in the thread pattern of the right ridged thread form. In  FIGS. 2E ,  2 G,  2 H and  2 I, the right ridged thread form varies in each successive ridged thread. 
     In  FIG. 2A , the left ridged thread form includes a first left screw thread  102  and a second left screw thread  104 . The right ridged thread form includes a first instance of first right screw thread  202 - 1  and a second instance of first right screw thread  202 - 2 . The first left screw thread  102  matches the first instance of first right screw thread  202 - 1 . The first left screw thread  102  may differ from the first instance of first right screw thread  202 - 1 . A second left screw thread  104  matches a second instance of first right screw thread  202 - 2 . 
     In  FIG. 2E , the right ridged thread form varies successively in each of the sixth right thread  212 , the seventh right thread  214 , and the eighth right thread  216 . 
     The ridged thread pattern on one or both of the right ridged thread form and the left ridged thread form may be immediately repeated. In  FIGS. 2B ,  2 C, and  2 D both the left side ridged thread and matching right side ridged thread immediately repeat. In  FIG. 2E , the sixth left thread  112  is seen to immediately repeat in the seventh left thread  114 , whereas the matching ridged threads on the right side vary. These matching right ridged threads are the sixth right thread  212 , the seventh right thread  214 , and the eighth right thread  216 . The number of ridged threads on one side may differ from the number of ridged threads on the other side. In  FIG. 2E , two left side ridged threads match to engage three ridged threads on the right side. In  FIGS. 2F to 2I , two left side ridged threads match to engage one ridged thread on the right side. 
     In  FIGS. 2D ,  2 G,  2 H, and  2 I, ridge bumps are provided. Often the ridge bump, shown in these Figures on the right, acts to urge a ridged thread on the left side to engage a matching, and neighboring, ridged thread on the right side. One skilled in the art will recognize that while the ridge bumps are only shown on the right side in these drawings, this is done to simplify the figures and discussion, and is not meant to limit the scope of the invention. Ridge bump  208  urges left side thread  110  to engage with matching ridged thread  210  in  FIG. 2D . Ridge bump  220  urges left side thread  116  to engage with matching ridged thread  218  in  FIGS. 2G and 2H . Ridge bump  224  urges left side thread  118  to engage with matching ridged thread  218  in  FIGS. 2G and 2I . 
     The materials of which the left side and right side of  FIGS. 2A to 2I  are made may vary from rigid, to essentially rigid, to somewhat flexible, to flexible. By way of example, the ridged threads of  FIG. 2A  may preferably be at least essentially rigid. The ridged threads of  FIG. 2B  may preferably be more flexible than  FIG. 2A . The ridged threads of  FIG. 2C  may preferably be somewhat flexible to flexible. The left and right side may preferably be made of different materials, one more rigid and the other more flexible. 
       FIGS. 3A and 3B  show aspects of the invention to further include collapsible tubes with a flexible throat  350  made with at least one ridged thread exterior screw  352 , and locked by a cap  300  possessing at least one essentially rigid interior ridged thread screw  302 . In certain aspects of the invention, the flexibility of the collapsible tube and the throat may be essentially the same. In certain other aspects, the flexibility of the collapsible tube and the throat may differ. These collapsible tubes are reusable and support the complete, controlled dispensing of their contents. One skilled in the art will recognize that the ridged threads in these Figures are on a flexible throat with conical shape. 
       FIG. 3A  shows a flexible throat  350  with at least two ridged threads  352  and  354 . In  FIG. 3A , cap  300  has two interior ridged threads  302 - 1  and  302 - 2 , whose ridges face downward. In  FIG. 3B , the preferred cap  300  has two interior ridged threads  302 - 3  and  302 - 4 , which face upward. In general it is believed that caps with at least one interior ridged thread facing upward are preferred. 
     The invention&#39;s collapsible tubes preferably utilize a flexible shoulder  504 , shown in  FIGS. 4A to 9H , being squeezed toward the flexible throat  502 , which concentrates the contents  900  so that very little is wasted in normal use. 
     In  FIG. 4A , the invention&#39;s collapsible tubes employ a shape  500  including the flexible throat  502  coupled to the flexible shoulder  504  which mates  506  to a collapsible tube body  508 . The collapsible tube body  508  terminates in a tube closure  510 , which may be permanent or reopenable. 
     In  FIG. 4B , the invention&#39;s collapsible tubes employ a shape  500  including the flexible throat  502  coupled to the flexible shoulder  504 , which mates  506  to itself. 
       FIG. 4C , the flexible throat  502  of  FIGS. 4A and 4B  including multiple external threads  352 - 1  to  352 -N. 
       FIGS. 5A to 9D  show various embodiments of the collapsible tubes similar to  FIG. 4B .  FIGS. 5A to 9D  show at least a first break  600  forming various columns in the radial axis of the flexible throat  502 . 
       FIG. 5A  shows a top view of a collapsible tube as in  FIG. 4B  showing a first break  600  forming a canted column.  FIG. 5B  shows a front view of the collapsible tube in  FIG. 5A  showing a first break  600  and a second break  602 .  FIG. 5C  shows a side view of the collapsible tube in  FIG. 5A  with the first break  600  forming rectangular column. 
       FIG. 5D  shows a detail of  FIG. 5C  showing the flexible throat  502  with a thread form including at least two, and in this case four threads. These threads may include open threads, ridged threads, or combinations of open threads and ridged thread. The open threads could be, by way of example, external acme threads, external buttress threads, external V threads, external box threads, or combinations or modifications of these well known open threads. The ridged threads are defined and shown in many examples throughout this document. 
       FIG. 5E  shows the first break  600  forming a fluted column expanding toward the flexible shoulder. 
       FIG. 5F  shows the first break  600  forming a fluted column expanding away from the flexible shoulder. 
       FIG. 5G  shows the collapsible tube as in  FIGS. 5B to 5D  with a cap  800 . 
       FIG. 5H  shows the collapsible tube of  FIG. 5G  with the cap  800  engaged and filled with at least one content. 
       FIG. 5I  shows a cross section of  FIG. 5H  of the collapsible shoulder  504 , flexible throat  502  engaging the internal thread form and the external thread form. The internal thread form includes internal buttress threads  804 - 1  to  804 - 4 . The external thread form includes external buttress threads  702 - 1  to  702 - 4 . The internal thread form and the external thread form collectively urge the cap  800  and the flexible throat  502  to seal the contained product into the collapsible tube. The cap  800  further, preferably includes an interior bulge  802  which acts upon the flexible throat  502  to urge the flexible throat  502  to engage the internal thread form and the external thread form. 
     As shown and discussed herein, the threads on the flexible throat  502 , the flexible shoulder  504 , and when applicable, the collapsible tube body  506 , and the flexible cone  520 , are preferably made of flexible materials. These flexible materials include, but are not limited to, at least one flexible thermoset elastomeric and/or flexible thermoplastic elastomer. Elastomeric plastics include, but not limited to, urethane, polyvinyl chloride, ThermoPlastic elastomer Olefin (TPO), Thermal PolyVinyl chloride (TPV), ThermoPlasRubber (TPR) and/or Silicone based compounds. An elastomeric plastic is typically a polymer blend or compound, which above its melting temperature, exhibits a thermoplastic behavior enabling it to be shaped into a fabricated article, such as a collapsible tube or cap. When the article is within its design temperature range, it exhibits elastomeric behavior without cross-linking during fabrication. The fabrication process is reversible. The article can be reprocessed and remolded. The method of making these collapsible tubes  500  may include, but is not limited to, using a mold, into which the material(s) are injected and/or blown. The material may be injected one or more times. When material is injected more than one time, the process is often known as a multi-shot molding. The ridged thread forms may preferably be bumped or unscrewed from the mold(s). 
     In  FIGS. 5I ,  5 K  5 L,  10 A, and  10 B, the internal thread form slides along the external thread form, and the external thread form slides along the internal thread form to slide along each other, when the internal thread form and the external thread form engage. After they engage, continued sliding causes the internal thread form and the external thread form to lock, sealing the contained product into the collapsible tube. 
     One skilled in the art will recognize that various bumps and ridges in the cap and throat may be used to enhance engagement. As used herein the engagement enhancing bumps and ridges are not part of the screw sliding operations. 
       FIG. 5J  shows the collapsible tube of  FIG. 5G  with a second cap  820  engaged and filled with contents.  FIG. 5K  shows a cross section of  FIG. 5J  with the collapsible shoulder  504  and flexible throat  502  of  FIG. 5I  engaging a hollow version of the second cap  820 .  FIG. 5L  shows a cross section of  FIG. 5J  with the collapsible shoulder  504  and flexible throat  502  of  FIG. 5I  engaging a filled version of the second cap  820 . Note the interior rim  822  included in the second cap  820  may preferably extend to below at least the first external thread  804 - 1  to aid in urging the reforming of the flexible throat  502 . It may further preferred that the interior rim  822  extend below the second external thread  804 - 2 , etc. One skilled in the art will recognize that many variations in the caps  820  and  800  are preferred in different situations, causing variation in at least their size, shape, number of threads, and whether or not they are hollow. 
       FIGS. 6A to 6D  show the front view of a collapsible tube with none, one, two, and three breaks in its external threads, respectively. 
       FIGS. 7A to 7D  shows the front view of the collapsible tubes of  FIGS. 6A to 6D  partially deformed by squeezing the collapsible tube bodies  506  and flexible shoulders  504 . 
       FIGS. 8A to 8D  show the further squeezing of the collapsible tube of  FIGS. 6A and 7A , which has no breaks in its external threads. 
       FIGS. 8E to 8H  show the further squeezing of the collapsible tube of  FIGS. 6C and 7C , which has a first break  600  and a second break  602 . 
       FIGS. 9A to 9D  show the side view of the squeezing of the collapsible tube shown in  FIGS. 7C , and  8 E to  8 H, with the contained product  900  being dispensed. 
     This method of using a collapsible tube permits dispensing essentially all of the contained product. The contained product may be any of the following: a pharmaceutical, a personal care product, a toothpaste, a food, an artist&#39;s paint, a glue, a hazardous chemical, a grease product, and/or a viscous plastic. 
     Substances will be referred to herein as viscous plastics when they are viscous enough to be pressed out of a collapsible squeeze tube to form a blob or a line for various purposes, such as caulk or other sealants, compounds used to create a braille letter, or other identifying mark on items for the blind, or decorative substances that are not simply paint but create texture and mass when applied, or compounds that dry when exposed to air forming durable shapes, marks, seals, decorations, and the like. 
     The collapsible tube  500  may have the tube closure  510 , repeatedly opened and sealed shut by using a mechanical device (sometimes known as a key). Versions of a key typically include a plastic cylinder with a slit in its center that slides over the open end of the tube, rolls toward the flexible throat  504  of the collapsible tube  500  to seal the tube closure  510 , and locks itself in the closed position. 
       FIGS. 10A and 10B  show two implementations of a collapsible tube  500  including a flexible cone  520  narrowing from the flexible throat  502  away from the flexible shoulder  504  and including a narrow opening  522  for dispensing essentially all of a contained product (which is not shown). 
     In  FIG. 10A , the flexible throat  504  has a thread form which includes a first external ridged thread  356 - 1  and a second external ridged thread  356 - 2 , which match the first internal ridged thread  306 - 1  and the second internal ridged thread  306 - 2 . The cap  840  includes the first internal ridged thread  306 - 1  and the second internal ridged thread  306 - 2 . 
     In  FIG. 10B , the flexible throat  504  has a thread form which includes a first external open thread  706 - 1  and a second external open thread  706 - 2 , which match the first internal open thread  806 - 1  and the second internal open thread  806 - 2 . The cap  840  includes the first internal ridged thread  806 - 1  and the second internal ridged thread  806 - 2 . 
     The collapsible tube  500  shown in the preceding Figures may preferably be made of at least one flexible thermoset elastomeric and/or flexible thermoplastic elastomer. Elastomeric include, but not limited to, urethane, polyvinyl chloride, ThermoPlastic elastomer Olefin (TPO), Thermal PolyVinyl chloride (TPV), ThermoPlasRubber (TPR) and/or Silicone based compounds. The cap to which the flexible threads mate may also be manufactured using existing collapsible tube manufacturing technology and materials. 
     The cap  800 , the cap  820 , and the cap  300  shown in the preceding Figures may preferably be made of at least one rigid thermoset elastomeric and/or thermoplastic elastomer. Elastomeric plastics include, but not limited to, urethane, polyvinyl chloride, ThermoPlastic elastomer Olefin (TPO), Thermal PolyVinyl chloride (TPV), ThermoPlasRubber (TPR) and/or Silicone based compounds. The cap to which the flexible threads mate may also be manufactured using existing cap molding technology and materials. The interior bulge  802  on the cap that inserts into the flexible throat  502  may also be a standard cap design. The interior rim  822  on the cap that inserts into the flexible throat  502  may also be a standard cap design. These caps may also be made from conventional cap materials. 
     There are two manufacturing options for a cap with ridged threads, such as cap  300 . The ridged thread cap may be made of a flexible material, molded using a special process allowing the delicate uniquely shaped interior ridged threads to be popped or bumped off the mold, or unscrewed from the mold. 
     Alternatively, the ridged thread cap may be made of a standard rigid material, or a slightly flexible material, with the uniquely shaped interior ridged threads bonded to the ridged thread cap via a second injection into the mold of a different material. This form of injection molding is often referred to as “co-molding” and allows for a molded product with two distinctly different types of material to be manufactured. An example is the rigid toothbrush with a squeezable grip on its handle commonly found in supermarkets. This type of molding is extremely expensive because custom molds and tools must be created to allow for multiple shots of plastic to be injected with precision. The first shot forms a cap in any rigid shape suitable for injection molding. The second shot is of a flexible plastic which forms the threads of the ridged thread cap in a continuous or interrupted pattern, which threads engage with the tube tip&#39;s flexible, ridged threads, forming a seal. The rigid or semi-rigid ring on the under side of the ridged thread cap, as in the first rigid cap case, will help to re-form the cylindrical shape of the flexible tube tip. 
     The preceding embodiments have been provided by way of example and are not meant to constrain the scope of the following claims.