Pipes and tubular conduits – Flexible – Corrugated
Reexamination Certificate
2000-06-02
2002-04-09
Brinson, Patrick (Department: 3752)
Pipes and tubular conduits
Flexible
Corrugated
C138S122000, C138S129000, C138S150000
Reexamination Certificate
active
06367510
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to plastic tubing and, more particularly, to apparatus and methods for making such tubing which is flexible and includes an external helical rib or bead.
2. Related Technology
Tubing which is flexible, and has a relatively thin wall and an integral helical supporting bead is known in the art. Such a flexible support-bead tubing construction provides substantial crush resistance while leaving the tube wall flexible enough to permit short-radius bends without collapsing or kinking the tube. The versatility of this kind of tubing is evidenced by its wide applicability in construction, ventilation, manufacturing processes, auto washes, medical devices, hospitals and other fields.
The walls of a support-bead tubing can be quite thin to minimize overall weight. This light weight for the tubing is an important feature when, for example, the tubing is used with an inhalation machine to provide a patient with more comfort during oxygen or medicated air delivery. Two other features of known thin wall support-bead or bead-reinforced tubing are transparency and smoothness of bore. Transparent plastic material permits inspection of the fluid coursing through the tube, to detect, for example, the presence of moisture in an anesthetic or patient oxygen delivery application. A smooth inner surface of such a tube is desirable to keep the tube free from deposits of contaminants and to discourage non-laminar flow. Also, this smooth inner surface makes the tubing product more desirable for applications in which the tubing is to be re-used. The smooth inner surface promotes easy and effective cleaning, sanitizing, and sterilizing of the tubing product.
U.S. Pat. No. 3,910,808 to Steward, discloses apparatus for forming a thin-walled, flexible, crush resistant tubing having a support-bead. Steward discloses a method for extruding a plastic strip having a longitudinal rib, and the method and apparatus for helically winding the strip about an axis to produce a corrugated flexible tubing having a smooth bore and a helical external support bead.
Many applications, however, require or are enhanced by the presence of controlled heating of such tubing. Neonatal patients, for example, as well as patients in shock or who are sustained on breathing equipment, are among those who benefit from gas flowing through heat-conditioned tubing.
U.S. Pat. No. 5,454,061 to Lenart Carlson, provides a helically wound and helically ribbed plastic tubing incorporating an electrically conductive heating wire and an apparatus and method for making the tubing. In this patent a plastic ribbon is wound about an axis into a tube with one edge of each lap overlapping and heat bonded to an edge of the preceding lap as the tubing is rotationally formed. A conductive wire is embedded in the ribbon and a bead is applied and heat-bonded onto the tubing, encapsulating the conductive wire during rotation of the tubing, and providing a unitary structure including a conductive wire integral to a flexible tubing. Again, the tubing has a corrugated crevice-free outside surface and a smooth inside surface. Coolant is applied to the tubing for cooling the unitary ribbon, wire, and bead during formation of the tubing, and also to assist in advancing the tubing along the axis of the manufacturing apparatus.
One prior application of a hollow ribbed pipe can be found in U.S. Pat. No. 5,051,081 assigned to Toyox. In this patent hollow ribs are produced by extrusion, and are then wrapped around the outer periphery of an extruded pipe. This construction of a tubing product has several deficiencies. For example, the interior walls of the hollow rib produced by this apparatus contain connection lines through which a gaseous material could escape into the ambient, and the rib is extruded in such fashion that it would not be possible to separate it from the tube and attach it to a hose barb. That is, the shape of the lumen or passage in this rib is not generally round.
SUMMARY OF THE INVENTION
A new application for such flexible tubing requires that a second lumen or passage be available for communication between the ends of the tubing. A preferred way of providing this second lumen or passage is to provide a lumen or passage inside and integrally defined by the support bead.
No prior product, method of manufacture, or apparatus is known which provides a transparent, sterilizable, thin-walled, smooth bore tube having a contemporaneously wound supporting and encapsulating bead defining a lumen, or defining plural lumens, each suitable for communicating a fluid between the ends of the tubing product, and with the bead, and tube forming a unitary structure with a smooth, crevice-free outer surface.
In view of the deficiencies of the related art as discussed above, it is a primary object of the present invention to provide a flexible, lightweight, crush-resistant tubing having one or plural supporting bead helically wound about and integral with the surface of the tubing. The is constructed with smooth walls free from joints or connection lines. The bead defines one lumen or plural lumens capable of transporting or communicating a fluid or gas without leakage to the ambient.
It is another object of this invention to provide apparatus and method for inexpensively making a tubing product, supporting bead with at least one interior lumen, and tube wall as a unitary body free of adhesive and binders and having a smoothly corrugated outer surface free of crevices.
Yet another object for this invention is to provide a method and apparatus for terminating the tubing product, providing for each of the central passage of the tubing and the lumen of the support bead to be connected to respective fittings in fluid flow relation.
These and other objects are achieved by the present invention which provides apparatus for combining a thin film or ribbon, and a supporting bead defining one lumen or plural lumens to make a flexible tubing, and provides a method for producing the tubing in a single winding and bonding operation. The present invention employs a winding mechanism which accepts in sequence: an extruded plastic flat ribbon, and one or plural extruded supporting bead(s). The ribbon is helically wrapped so that its edges overlap and simultaneously heat-bond to themselves to form a lap joint. A bead is laid atop the ribbon and heat-bonded to the ribbon at the lap joint, forming a unitary body as described below. If plural beads are used each in turn is wound around the tube parallel with the first in similar fashion. One or more of the beads defines a single or plural lumens extending helically along the tubing product. Each lumen inside the bead will retain the same approximate size and shape free from obstruction for the entire length of the tubing product. As the bead is extruded a small amount of regulated air or gas pressure is introduced into the lumen in such a fashion as to keep the lumen open, and to insure that it retains a uniform cross sectional size and shape.
Another embodiment of the invention utilizes the tubing body construction and support bead type as described above with the added feature of having a pair of electrical conductors encapsulated within the tubing body and immediately under the support bead. One use for such electrical conductors is as an electrical resistance heating conductor to offset heat loss to ambient from warmed tidal air flow in the tube. Another use for such an electrical conductor pair would be as an electrical link between an electrical sensor and a device responsive to this sensor.
While other heat-bondable plastics may be successfully used to make the flat ribbon which becomes the wall of the present tubing product, for a variety of medical applications a polyolefin plastomer such as EXACT™ is preferable. The properties of this material include chemical purity, reusability, transparency and resistance to damage from sterilization. Thermoplastic rubbers such as SANTOPRENE™, or thermoplastic elastomer such as SARLINK™, are sui
Brinson Patrick
Miller Terry L.
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