1. Field of the Invention
The illustrated embodiments of the invention relate to the field of expandable tubing and particularly lined expandable tubing of enhanced degradation resistance.
2. Description of the Related Art
Some tubing such as latex tubing is produced in production quantities by repeatedly dipping a mandrel through a bath of liquid which solidifies on the mandrel. The mandrel may be produced from a material to which the solidified liquid will not adhere or is coated with a material that prevents the solidified liquid from adhering to the mandrel when the mandrel is removed from the finished latex tube.
Production of tubing such as latex tubing is most often an automated process in which a continuous length of mandrel is led by a series of rollers through a liquid bath of material and subsequently through a drying or curing area after which the process is repeated. Each repeated “dipping” results in an increase in the wall thickness of the tube being produced. This process may be repeated until the wall thickness reaches the desired dimension. The finished tube may then be subjected to additional curing processes after which the mandrel is removed from the interior of the tubing. The finishes product is a tube of homogeneous material such as latex rubber.
In practice, it has been possible to alter the composition of the first few layers of deposited such as latex by mixing other compatible materials such as liquid nitrile rubber with the primary material in an attempt to improve compatibility with materials that would come in contact with the interior of the finished tubing. This approach is limited, however, by the increased difficulty in extracting the mandrel from the finished tube, which can commonly have a length in excess of 100 feet. Typically, only a small percentage of materials other than the primary material can be added before it becomes impossible to remove the mandrel from the finished tubing. The addition of blended materials to the primary material also affects the properties of the finished product, often decreasing the desirable properties of the finished tube. Therefore, a need exists in the industry for an integrally lined expandable tube and a method and apparatus for the manufacture thereof.
The illustrated embodiments describe an expandable tube having superior degradation resistant qualities and systems and methods for manufacturing such tubing.
Tubing such as latex tubing may be employed in many applications in which it comes in contact with oils and chemicals. For example, a latex tubing may be used to dispense frosting in the cake decorating art. The inherent expandability and “memory” of latex results in an even feed pressure and smooth flow of frosting within the tube out of the decorating tip. In a further example, a latex tube may be used in the pump mechanism of a soap dispenser. In these and other examples, however, oils and other chemicals in the dispensed material may cause degradation and disintegration of the latex, shortening the life of the tube and contaminating the material in the tube with latex particles.
A properly composed liner can protect the latex from exposure to materials within the tube. To be effective, the liner must be able to adhere to the latex tubing either by natural adhesion or through an intermediary coating applied to the liner. Additionally, the liner material must have sufficient expansion capacity to meet the expansion requirements of the application for which the tubing will be used. For example, a similar expansion rate of the latex tubing and the liner prevents separation of the liner material from the body of the latex tube. In such a scenario the tube may supply the memory that the non-latex liner may lack in returning to the original dimensions.
The prior art, however, has failed to supply such tubing, or a method and apparatus for the manufacture thereof. Attempts to produce such tubing have been defeated by the lack of a means for of applying the liner either to the mandrel upon which the expandable tubing will be deposited or directly to the interior of the expandable tubing.
The present invention addresses the aforementioned challenges in the prior art. In certain embodiments a mandrel is inserted into a liner tube. In one embodiment, the liner is placed within an open ended rigid chamber having gas permeable walls. The ends of the liner may be stretched over and sealed against a surface on each end of the chamber. A vacuum is drawn surrounding the chamber, causing the atmospheric pressure within the liner tube to force the liner tube to expand against the inner walls of the chamber. A mandrel is subsequently inserted into the lumen of the expanded liner. After insertion of the mandrel, the vacuum is removed allowing the liner tube to contract around the mandrel. The liner may be thermal plastic or other appropriate material.
In another embodiment, the liner material may be extruded over the outside diameter of the mandrel. The prepared mandrel may be fed through a specially prepared die that centers the mandrel within the extrusion path of the liner material. The described process enables production of a very thin liner.
In a further embodiment, the liner and mandrel may be co-extruded in a single processing system. Other methods may also be employed to arrive at the liner mandrel combination, producing a liner that is physically supported by the mandrel during a variety of subsequent operations and from which the mandrel may be removed when desired.
In one embodiment, an expandable tubing material is applied to the liner clad mandrel by a repeated dipping process standard in the industry. Once the wall thickness of the combined liner and applied tubing material reaches the required dimension, the finished tube may be removed from the production equipment. The post curing process may be performed in a manner similar to that employed for homogeneous expandable tubing. In a further embodiment the post curing process may be modified to be compatible with the liner material used. The mandrel is then removed from the inside of the tubing using processes common for the removal of a mandrel from homogeneous expandable tubing. In one embodiment the expandable tubing comprises latex. In further embodiments the expandable tubing may comprise other material appropriate for the proposed use.
In order that the advantages of the invention will be readily understood, a description of the invention will be rendered by reference to specific embodiments that 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 embodiments of invention will be described and explained with additional specificity and detail through the use of the accompanying drawings, in which:
Reference throughout this specification to “one embodiment,” “an embodiment,” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in one embodiment,” “in an embodiment,” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.
Furthermore, the described features, structures, or characteristics of the invention may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided, to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, and so forth. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.
Samples:
Sample product has been produced using a liner made from a Thermal Plastic Elastomer material that was purchased from Kent Elastomer as their product K3826. This material has elongation properties that closely approximate those of latex rubber. In one test run approximately 25 feet of this material was installed over a ½″ diameter, thick walled, silicone tube that was used as a mandrel. The liner was installed using the open ended vacuum chamber method described above. The mandrel with the applied liner was sent to a major manufacturer of latex tubing where the finished tube was produced using standard production equipment.
Latex was applied over the supplied mandrel with liner to a finished diameter of approximately one inch. The finished assembly was returned to the inventor's facility where the mandrel was removed using a standard forced air procedure. The adhesion of the latex to the liner was found to be excellent, with the liner and latex appearing to be inseparable by mechanical means. The finished product was tested and found to have properties closely approximating a homogeneous latex tube of the same dimensions. The liner provided complete resistance to vegetable oil with which the finished lined tube was tested. A homogeneous latex tube was tested in conjunction with the testing of the lined tube. The homogeneous latex tube was not resistant to the vegetable oil and the inside surface of the tube quickly degraded with repeated expansion and contraction.
The expandable tube 102 provides the strength, expandability, and configurational memory required by various uses. The expandable tube 102 may comprise a flexible, durable material with good configurational memory, such as a pure latex rubber. In certain embodiments, the expandable tube 102 comprises a latex rubber with various additives, nitrile, or an other suitable material known in the art.
The liner 104 protects the interior of the expandable tube 102 from contact with oils and other chemicals that may cause degradation of the tube 102. The liner 104 is composed of an elastic, degradation-resistant material selected to bond with the expandable tube 102. The liner may be composed of various thermal plastic elastomers, thermo set elastomers such as silicone a, urethane, or other suitable materials known in the art.
In one embodiment, the liner 104 and expandable tube 102 have similar expansion capabilities and are bonded to resist mechanical separation. Thus, the expandable tube 102 and the liner 104 may function as an integral unit, preventing separation of the two elements during use.
The mandrel 202 supplies a support matrix upon which the expandable tube 102 may be deposited or extruded. The mandrel may be a pipe or a solid rod and may be composed of or coated with a variety of non-bonding materials selected for easy release of the tube, including silicone rubber and polypropylene. The liner 104 is applied to the mandrel 202 before deposition or extrusion of the expandable tube 102. The expandable tube 102 is applied over and may bond with the liner 104.
In the illustrated embodiment, the central chamber 302 is defined by the central chamber wall 304, with the perforations 306 in the central chamber wall 304 rendering the chamber wall gas-permeable. Other embodiments include a central chamber wall 304 of rigid mesh. In a further embodiment the central chamber wall 304 may include slits, louvers, or other openings.
The outer chamber 308 surrounds the central chamber wall 304. The outer chamber wall 310 defines the outer chamber 308. The ends of the outer chamber wall 310 may be sealed to the central chamber wall 304 with an air-tight seal 312. In the depicted embodiment the outer chamber wall 312 includes the evacuation port 314.
Air may be evacuated from the outer chamber 308 through the evacuation port 314. Air may pass into the outer chamber through the perforations 306 in the central chamber wall 304 and be evacuated, creating a vacuum in the central chamber.
In the illustrated embodiment a mandrel extrusion die 902 receives the mandrel extrusion material 904 and extrudes a mandrel 906. The extruded mandrel 906 is fed through a liner extrusion die 908, which is loaded with the liner extrusion material 910. The extruded liner 912 is then applied to the moving mandrel 906, creating an extruded liner-clad mandrel 914.
The mandrel 202 and the extruded mandrel 906 may be functionally equivalent, or may be manufactured of different material. Likewise, the liner clad mandrel 802 and the extruded liner-clad mandrel 914 may be functionally equivalent, or may be manufactured of different materials as appropriate to the method of manufacture and end use.
The illustrated system of manufacture enables a pre-formed mandrel to be inserted into a pre-formed liner tube. The pre-formed mandrel 202 may be composed of various materials known in the art designed to resist adherence to a liner tube 104, or may be treated with a release material. The liner tube 104 may be composed of thermal plastic elastomer or other material known in the art. An expandable tubing material such as latex may be applied to the liner-clad mandrel 802 through industry standard latex tube manufacture 1002 such as successive dipping in a latex bath, or other methods known in the art. In a further embodiment the material such as latex may include performance enhancing or other additives. The industry standard removal 1004 of the mandrel 202 may comprise forcing air between the mandrel 202 and the liner 104, or other procedure known in the art.
The illustrated system of manufacture enables the creation of a liner-clad mandrel 914 through a two step successive extrusion operation. Latex or other expandable tubing material may be applied to the liner-clad mandrel 914 through industry standard latex tube manufacture 1002 such as successive dipping in a latex bath, or other methods known in the art. In a further embodiment the latex or other expandable tubing material may include performance enhancing or other additives.
The industry standard removal 1004 of the mandrel 906 may comprise forcing air between the mandrel 906 and the liner 112, or other procedure known in the art. In a further embodiment the system may include a mandrel degradation device such as a chipper and the mandrel material 904 may be recycled through the mandrel extrusion die 902.
The schematic flow chart diagrams that follow depict order and labeled steps indicative of one embodiment of the presented method. Other steps and methods may be conceived that are equivalent in function, logic, or effect to one or more steps, or portions thereof, of the illustrated method. Additionally, the format and symbols employed are provided to explain the logical steps of the method and are understood not to limit the scope of the method. Arrow types and line types are understood not to limit the scope of the corresponding method. Indeed, some arrows or other connectors may be used to indicate only the logical flow of the method. For instance, an arrow may indicate a waiting, curing, or monitoring period of unspecified duration between enumerated steps of the depicted method. Additionally, the order in which a particular method occurs may or may not strictly adhere to the order of the corresponding steps shown.
The mandrel insertion apparatus may be similar or different in form to the mandrel insertion device 300. In one embodiment, the mandrel insertion apparatus may be constructed of metal. Alternatively, the mandrel insertion apparatus may be constructed of rigid plastic or other appropriate material. The mandrel insertion apparatus may also be constructed of a combination of materials.
In one embodiment, the mandrel 202 may be a polypropylene tube. The mandrel 202 may also be a silicon tube, a solid cylinder, a rope or cord or other appropriate support structure. The liner tube 104 may be thermoplastic or may be composed of other material formulated to bond to expandable tubing, release easily from a mandrel and match the expansion properties required for the end use of the expandable tubing.
In one embodiment, pure latex may be applied to the liner clad mandrel 802. Alternatively, latex with additives or other types of natural or synthetic rubber or other expandable tubing material.
In one embodiment, the extrusion system employs a dual extrusion apparatus such as depicted in
In one embodiment, the extrudable liner material may be thermoplastic. In other embodiments, the extrudable liner material may be composed of other compound formulated to bond to latex, release easily from a mandrel and match the expansion properties required for the end use of the latex tube.
In one embodiment, pure latex may be applied to the liner clad mandrel 802. In other embodiments, latex with additives other types of natural or synthetic rubber or other expandable tubing material may be applied.
The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. 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 which come within the meaning and range of equivalency of the claims are to be embraced within their scope.