Flexible Corrugated Tubing Having Improved Performance Characteristics

Abstract

Flexible corrugated tubing, preferably formed of a thermoplastic material having a plurality of thin strips or beads of the same plastic material used to form the tubing. The stripes or beads are arranged at discrete angular positions along the interior surface of the tubing and extend from internal peak to internal peak for the length of the tubing section. The introduction of the thin plastic beads has no measurable effect upon the flexibility of the tubing and is extremely effective in eliminating whistling in operation. The tubing may be formed in a continuous process, for example, in the manner described in U.S. Pat. No. 3,280,430, issued Oct. 25, 1966, which is further provided with means for either extruding beads of plastic material to form the plastic stripes or is provided with scraping means for scraping small portions of plastic material utilized to form the corrugated configuration and extending the scraped material from internal peak to internal peak along the length of the continuously formed tubing.

Description

The present invention relates to flexible corrugated tubing and more particularly to flexible corrugated tubing having a unique configuration which provides improved operating characteristics and further relates to a novel method and apparatus for producing such tubing.

Flexible corrugated tubing is a well-known commercial product and is utilized in a wide variety of industrial, as well as nonindustrial applications.

For example, flexible corrugated tubing, preferably formed of a suitable plastic material, is quite frequently utilized as vacuum cleaner hose and also finds similar application with swimming pool equipment. In use, a suitable accessory is coupled at one end thereof, while the other end is secured to the vacuum source of the vacuum cleaning apparatus. When utilized in such applications, the flexible corrugated tubing has been found to generate an annoying whistle which is even greater in volume in large commercial apparatus.

The present invention is characterized by providing a novel method and apparatus for forming flexible corrugated tubing which retains all of the advantageous characteristics of conventional tubing while being further provided with a unique configuration which has been found to eliminate the annoying whistle in both large and small scale vacuum apparatus.

In one preferred embodiment, the flexible corrugated tubing is formed in a continuous process in which extruded plastic material, in molten form, emerges from an extruder die which cooperates with coacting mold cavities provided in associated die members to receive and form the extruded plastic material. A pressure source causes the extruded plastic material to be urged against the corrugated surfaces of the coacting die members, thereby forming the corrugated tubing configuration.

In one preferred embodiment, a skimmer apparatus is mounted adjacent the output end of the extruder for lightly skimming or scraping against the corrugated configuration being formed for scraping a very small amount from each interior peak of the corrugation and stretching the small amount being scraped thereby from each peak to the next adjacent peak, thereby forming a thin bead or stripe of plastic material extending the entire length of the tubing being formed. In cases where a cuff is provided at predetermined intervals along the length of the tubing, actuator means may be provided for drawing the skimmer members inwardly to prevent the skimmer members from scraping along the interior surface of the cuff. One or more such beads may be formed at spaced intervals around the interior periphery of the tubing. The bead is quite thin so as to have an insignificant effect upon the flexibility of the tubing.

In another preferred embodiment, the skimmer assembly may be replaced by a bead applicator member provided with a plurality of openings arranged near the periphery thereof. The bead applicator is positioned adjacent the output end of the extruder assembly and causes a small portion of the extruded molten plastic material to be ejected through said openings to form a thin bead or stripe along the peaks of the interior corrugated surface of the tubing being formed. Tubing thus formed has the same advantageous features as described above for tubing employing a skimmer assembly.

It is, therefore, one object of the present invention to provide flexible corrugated tubing, preferably formed of plastic material, having a unique interior configuration designed to provide improved operating characteristics as compared with conventional tubing in that whistling which occurs in connection with the use of vacuum or blower apparatus is eliminated.

Another object of the present invention is to provide a novel method and apparatus for forming flexible corrugated tubing, preferably formed of a plastic material, in which thin beads are formed along the interior surface configuration of the corrugated tubing to yield tubing having a unique interior configuration which eliminates whistling.

Still another object of the present invention is to provide a novel method and apparatus for forming flexible corrugated tubing, preferably formed of a plastic material, in which a thin bead of plastic material of the same type employed in the normal extruding process is formed along the inner peaks of the tubing corrugated surface to provide a unique tubing configuration which eliminates whistling.

Still another object of the present invention is to provide a novel method and apparatus for forming flexible corrugated tubing, preferably formed of a plastic material, in which the plastic material, while being extruded and urged into the corrugated die members, is lightly scraped along the peaks of the interior surface configuration thereof to form one or more stripes extending from interior peak to interior peak to provide a unique interior configuration for the tubing which eliminates whistling.

These, as well as other objects of the present invention will become apparent when considering the accompanying description and drawings in which:

FIG. 1 is a perspective view of a section of novel corrugated tubing formed in accordance with the method and apparatus of the present invention, a portion of which has been broken away to facilitate an understanding of the internal configuration.

FIG. 1a is a sectional view of an alternative embodiment relative to the embodiment shown in FIG. 1.

FIG. 2 is an elevational view of one preferred embodiment of the present invention, namely the skimmer actuator assembly shown in conjunction with coacting die members for forming the novel tubing of FIG. 1.

FIG. 2a is a side view partially sectionalized, of a portion of the assembly of FIG. 2.

FIG. 2b is an end view of the elements of FIG. 2a.

FIGS. 2c and 2d are sectional and end views respectively, of the actuator plunger of FIG. 2.

FIG. 3a is a sectional view of another preferred embodiment of the present invention, namely the bead extruding assembly shown in conjunction with the extruder and die members which are employed for forming tubing of the type shown in FIG. 1.

FIG. 3b shows a front view of the bead disc employed in the embodiment of FIG. 3a.

Referring now to the drawings, FIGS. 1 and 1a show two alternative embodiments of a portion of the novel flexible corrugated tubing which may be formed through the method and apparatus of the present invention.

A portion of the tube section 10 has a substantially corrugated configuration comprised of a plurality of separate continuous rings 11 which form the peaks of the exterior corrugated configuration, which rings are joined by interposed circular sections 12 forming the valleys of the exterior configuration.

The thickness of the corrugated section is reasonably uniform such that the corrugated configuration appears along the interior surface of the tubing with the rings 11 comprising the valleys 11a along the interior surface and with the circular sections 12 forming the peaks 12a of the interior surface.

The interior surface is further provided with a plurality of stripes or beads 13 and 14 running the entire length of the corrugated portion and being jointed to and extending from interior peak to interior peak 12a. The beads 13 and 14 have a substantial narrow width W and a thickness T which is less than the thickness or, alternatively, no greater than the thickness T' of the corrugated section. Both the corrugated section and the beads are formed of the same plastic material simultaneously with the forming of the tubing which is preferably produced in a continuous process.

While FIGS. 1 and 1a show a rather short section of tubing, it should be understood that extremely long lengths of tubing may be formed through such a continuous process with the particular length required for any application being dependent only upon the needs of the user.

FIGS. 1 and 1a further show a cuff section 15 integrally formed and joined to one end of the corrugated section. The cuff section has a substantially circular cross-sectional configuration and is provided for joining or coupling a length of tubing to a piece of industrial equipment. For example, a tubing section may be provided with cuff portions 15 at opposite ends thereof, one cuff section being provided for coupling to the output of an industrial vacuum cleaning apparatus and the other cuff section being utilized for joining an accessory brush nozzle or other implement thereto. The webs 13 and 14 of FIG. 1 are substantially straight while the webs 13' and 14' of FIG. 1a are arranged in a helical pattern.

Exhaustive experimentation has shown that conventional tubing which is of the type shown in FIG. 1 with the exception that the beads 13 and 14 are omitted, generates undesirable whistling which is quite annoying and is of substantial volume when such tubing is employed in large size and/or industrial type vacuum cleaning apparatus. Exhaustive experimentation has shown that the provision of the beads 13 and 14 eliminates the whistling. Although the preferred embodiments of FIGS. 1 and 1a provide two beads which are arranged at opposite ends of a common diameter, it should be understood that a fewer or greater number of such beads may be arranged at spaced intervals around the interior corrugated surface of the tubing.

FIG. 2 shows one particular apparatus which may be employed for the purpose of forming the bead or strip 13 (and/or 14) substantially simultaneously with the formation of the corrugated tubing. For purposes of understanding the present invention, a simplified description of the apparatus for forming the corrugated plastic tubing will be set forth herein. A detailed description of such apparatus is set forth in U.S. Pat. No. 3,280,430, issued Oct. 25, 1966 and assigned to the assignee of the present invention. The apparatus is comprised of an extruder means which includes an elongated core member 21 and an annular-shaped jacket 22 arranged concentrically with core member 21 and cooperating therewith to form an annular hollow passageway 23 for urging the freshly extruded thermoplastic material 24 from the extruder toward the tube forming apparatus. The forward end of core 21 and jacket 22 are brought into alignment with the longitudinal axis of a path defined by a plurality of moving die blocks 25-26 and 25a-26a which are coupled by means, shown best in FIG. 1 of the above-mentioned U.S. patent, to chain drive means which act to move each of the die block pairs such as 25-26 in the direction shown by arrow A. It should be understood that the chain drives, as shown in FIG. 1 of the above-mentioned U.S. patent, are closed-loop chains which support and move the die blocks past the extruder means so as to receive the extruded thermoplastic material and form this material into the corrugated tubing. The die blocks move in separate closed loop paths which cooperatively come together in the region of the extruder assembly so as to coact and thereby form unitary mold cavities having surface configurations 27 and 28 which shape the extruded thermoplastic material into the corrugated configuration. Each die block pair, as shown best in FIGS. 7 and 8 in the above-mentioned issued patent, forms one-half of the mold cavity and these die block pairs are urged firmly into surface contact with the one another by means of pressure plates 47, shown best in FIGS. 1 and 3 of the above-mentioned U.S. patent.

The forward ends of core 21 and jacket 22 are coterminous. Core member 21 is provided with an axially aligned air passage comprised of a first axial portion 29 having a first diameter which communicates with a second axial portion 29a of a slightly increased diameter which further communicates with a third axially aligned passageway portion 29b of a still further increased diameter 29c and a final axially aligned portion 29c of a still further increased diameter.

Axial passageway portion 29d is provided with a tapped interior surface for threadedly engaging a threaded mounting bushing 30 having a substantially circular-shaped cross-sectional configuration and a head portion 30a for retaining a spacer member 31 against the left-hand face of core member 21. Spacer 31 is provided with a head portion 31a for aiding and directing the flow of extruded thermoplastic material in a manner to be more fully described.

The axial passageway portions 29 and 29a have positioned therein an elongated hollow cylindrical tube 32 also shown in FIGS. 2a and 2b. The left-hand end of tube 32 communicates with an opening 33 in the left-hand portion 34 of the extruder apparatus, which opening communicates with the hollow tube 32 at 35. A suitable seal such as an O-ring 36 is provided to prevent the escape of any air introduced into opening 33 for a purpose to be more fully described. Hollow tube 32 is secured within axial passageway portion 29a by means of a disc-shaped member 37 shown best in FIGS. 2, 2a and 2b. Member 37 is provided with a centrally located opening 37a for receiving and supporting tubular member 32 within the axial passageway 29a. The exterior periphery of member 37 is threaded for the purpose of threadedly engaging a tapped portion 29b. Member 37 is further provided with a plurality of small openings 37b arranged at spaced intervals around central opening 37a to enable the passage of air therethrough for a purpose to be more fully described.

The disc-shaped member 37 is attached to tubular member 32 on both sides of the tube which surround the central opening 37a of member 37. The right-hand end of tubular member 32 is secured (such as, for example) by brazing to a small tubular section 38 which, in turn, is further secured to the left-hand end 39a of a collapsible bellows section 39. The right-hand end of bellows section 39 is brazed to the left-hand end of a short tubular section 40 which, in turn, receives and surrounds a circular-shaped projection 41a of actuator plunger 41.

The actuator plunger 41 is shown best in FIGS. 2, 2c and 2d and is further provided with a central portion having an axially aligned passageway 42 open at 42a, the right-hand end of the plunger relative to FIGS. 2 and 2c, and communicating with two radially aligned openings 43 and 43a to permit the passage of air therethrough in a manner to be more fully described. A pair of similar openings 43b (only one of which is shown in FIG. 2c) are arranged at right angles to and a spaced distance from openings 43 and 43a for the same purpose. The central portion of plunger 41 has integrally joined thereto a pair of arms 44 and 44a whose outer peripheries are tapered at 45 and 45a, respectively. Plunger 41 is slidably received by bushing 30 which threadedly engages a tapped aperture in axial passageway portion 29c. The head portion 30a of bushing 30 secures a pair of resilient metallic fingers 46 and 46a sandwiched between head portion 30a of bushing 30 and the right-hand surface of spacer member 31.

The operation of the actuator plunger assembly is as follows:

Connection of a vacuum source (not shown) to opening 33 creates a vacuum condition within the confined interior space defined by opening 33, the central opening of tube 32 and the interior of bellows 39 (whose right-hand end is airtightly sealed to tube portion 42 so as to draw plunger 41 inwardly or toward the left, causing the finger members 46 and 46a which slidably engage portions 45 and 45a, respectively, to occupy the solid line positions designated by the numerals 46 and 46a of FIG. 2). In this position, the fingers will scrape against the extruded plastic material being ejected into the mold members for a purpose to be more fully described.

In instances where it is desired to withdraw the finger members from the scraping position, an air pressure source (not shown) is coupled to opening 33 which communicates with the hollow interior of tubular member 32 and of bellows 39 causing plunger 41 to move outwardly or to the right to occupy the solid line position shown in FIG. 2. Fingers 46 and 46a which are both normally biased toward the longitudinal axis 47 of the extruded structure, are released from the scraping position and moved to the inward position 46' and 46a ' causing a termination of the scraping action.

The communicating passageways 29-29b, 43, 43a and 42 serve, in a manner to be more fully described, to aid in the corrugated tube forming operation in a manner to be more fully described. Although not shown in FIG. 2, an opening similar to opening 33 is provided in extruding assembly portion 34 which is aligned at an angle to opening 33 and is arranged to communicate with the left-hand end of axial passageway 29. Through this opening (not shown) air is forced into the annular-shaped interior region defined by the interior surface of axial passageway 29 and the exterior surface of hollow tubular member 32. This air is passed through this passageway and into axial passageway portion 29a where it then passes through the openings 37b provided in member 37. After passing through openings 37b the compressed air passes through the interior space defined by the remainder of the passageway 29a and passageway 29b and the exterior surface of tube 32, tube section 38 and bellows 39. The air then enters through the radially aligned openings 43 and 43a provided in actuator plunger 41 and then enters into the axial passageway 42 where it exits through openings 42a to enter into the region defined by the mold cavities 25 and 26, for example. This compressed air aids in the formation of the corrugated tubing by urging the thermoplastic material into the undulations formed in the mold cavity members 25 and 26 in a manner to be more fully described.

It can thus be seen from the foregoing description that two separate air passageways are provided, which passageways are clearly isolated from one another so as to provide compressed air for the extruding operation on the one hand and to provide on the other hand, a passageway for activating the actuator plunger 41.

A suitable opening (not shown in FIG. 2) is provided for introducing thermoplastic material into the annular-shaped passageway 24 in the enlarged region 24a thereof. This extruded thermoplastic material is urged in a direction shown by arrow 47 through the tapered portion 24b and the straight portion 24 of the passageway where the extruded plastic material urged through the passageway is ejected in a region of spacer 31 at an elevated extruder temperature. The head portion 31a of spacer member 31 directs the extruded thermoplastic material 48 radially outward to move the material adjacent the undulated molding surfaces 27 and 28 of the mold cavity blocks 25 and 26, respectively. Air of a pressure of about 5 p.s.i. from a source not shown is admitted into the air passageway beginning at opening 33 so as to ultimately pass out through opening 42a in plunger 41 and thereby be dispersed within the hollow interior defined by the mold cavities so as to assist in urging the thermoplastic material against the undulations formed in the mold cavities. The air pressure effectively operates to conform the annular body of thermoplastic material to the mold surfaces 27 and 28, thereby forming the annular corrugations in the wall thereof including the alternating peak and valley portions. It should be understood that the forward free end of the extruded and molded corrugated tubing may be crimped or tied to make the tubing airtight so that the air pressure introduced into the cavity through openings 42a is effective in conforming the wall of the extruded plastic tubing to the mold surfaces.

As the successive pairs of die blocks 25-25a, 26-26a, etc., move in a direction shown by arrow 50 in unison with the movement of the drive sprockets shown, for example, in FIG. 1 of the previously mentioned U.S. Pat. No. 3,280,430, the freshly formed corrugated tubing is rapidly cooled by means of a series of atomizer sprays shown in FIG. 3 of the above-mentioned U.S. patent so as to adequately cool the hot molded tubing within a relatively short time interval which, for example, is about the time that it takes one pair of coacting die blocks (25 and 26, for example) to pass by the annular-shaped exit opening of the extruder. The corrugated tubing T may be continuously wound upon a suitable takeup reel (not shown), if desired. The die blocks are obviously coordinated with the size of the extruder core 21 and jacket 22 to form tubing of the desired diameter and depth of corrugation.

The slender beads or stripes 13 and 14, show best in FIG. 1 are formed within the interior of the corrugated tubing by means of the actuator plunger fingers 46 and 46a by air pressure activation of the plunger to move the fingers to their outermost position shown in FIG. 2, causing the resilient fingers to lightly scrape against the extruded thermoplastic material as it conforms to the mold undulations. The fingers thereby remove and redistribute a very small portion of the thermoplastic material causing it to extend from internal peak to internal peak, thereby forming a substantially continuous and substantially straight web of thermoplastic material extending the entire length of the corrugated section.

The corrugated mold sections such as 25 and 26, for example, may be automatically removed and replaced by other mold portions such as, for example, mold portions 52 and 53 which have smooth, semicylindrical-shaped interior surfaces 52a and 53a for the purpose of forming a cuff or coupling portion for a section of corrugated tubing of any desired length. Since these cuff portions have interior diameters which may be less than the interior diameters of the interior peaks of the corrugated tubing, the actuator plunger has been provided with the reciprocating action described hereinabove for the purpose of withdrawing the resilient spring members 46 and 46a from the region of engagement with the thermoplastic material so as to prevent a scraping action from occurring in the region in which the corrugated tubing cuff portions are formed by mold cavities such as 52 and 53.

Obviously, if desired, a single web (either 13 or 14) may be formed within the corrugated tubing portion interior or more than two such webs may be formed within the interior (depending upon the particular needs of the user).

FIGS. 3a and 3b show views of another alternative embodiment which may be employed for forming the beads referred to in FIGS. 1 and 1a. The alternative embodiment 60 (in which like components are designated with like numerals) utilizes mold sections 25-26, 25a-26a, etc., arranged in substantially the same fashion as described hereinabove with regard to FIG. 2 as well as with regard to the above-mentioned U.S. patents. The primary distinction between the embodiments of FIGS. 2 and 3a-3b is that the actuator assembly is replaced by a bead applicator member 61, to be more fully described.

The core member 21 is provided with an annular-shaped hollow passageway 62 coaxial with the extruder longitudinal axis 47 and is adapted to receive air at an elevated pressure. As was the case with the embodiment of FIG. 2, the annular-shaped passageway 24 between core 21 and jacket 22 receives the extruded thermoplastic material. A small disc-shaped spacer member 63 is mounted to the right-hand end of core member 21 and has an outer diameter substantially equal to the diameter D of the inner wall of annular passageway 62. Bead nipple disc 61 is secured by suitable fastening means (not shown) to core member 21. The disc is substantially circular in shape, is provided with an arcuate-shaped circular periphery 64 and is further provided with a pair of diametrically opposed openings 65 and 65a. The left-hand ends of these openings are substantially in alignment with the annular passageway 24 which guides the extruded thermoplastic material.

In operation, the mold cavity members 25-26, 25a-26a, etc., move in the direction shown by arrow A by means of an assembly referred to hereinabove and shown in detail in the previously mentioned issued patent in conjunction with movement of the extruded plastic through the annular passageway 24. The bead nipple disc 61 deflects the exiting thermoplastic material 48 toward the convolutes 27 and 28 in the mold cavities. A portion of the extruded thermoplastic material passes through openings 65 and 65a in bead nipple disc 61 so as to be laid upon the extruded thermoplastic material which has previously been deposited upon the interior peaks of the mold cavity so as to form a substantially continuous, straight web or bead extending from peak to peak within and along the interior surface of the corrugated tubing section.

To aid the extruded thermoplastic material in conforming to the convolutes of the mold cavity, air at an elevated pressure which may be of a value as was previously described, is urged out of annular passageway 62 to fill the cavity hollow interior and thereby firmly urge the thermoplastic material to closely conform to the mold cavity configurations. The remaining apparatus employed in the formation of the corrugated tubing, as was previously described with respect to FIG. 2 and with reference to the above-mentioned U.S. patent, would, likewise, be employed in the embodiment of FIGS. 3a and 3b. For example, the forward end of corrugated tubing being formed would obviously be crimped to provide an airtight seal for the air being introduced at elevated pressures.

Obviously, a greater or lesser number of beads or webs may be laid down along the interior surface of the corrugated tubing by providing fewer or greater numbers of openings of the type shown as 65 and 65a in FIGS. 3a and 3b.

The helical webs of FIG. 1a may be formed by slowly rotating the cylindrical portion 21 of FIG. 3a, as shown by arrow 66, so as to slowly rotate disc 61 and thereby form two webs (13' and 14') arranged in a helical manner. The spring members 46 and 46a of FIG. 2 may be rotated in a similar fashion. Obviously, combinations of the helical and straight beads may be provided if desired. For example, the helical pattern may be modified to form a "zigzag" pattern or the helical pattern and straight bead pattern may be laid down in an alternating fashion.

It should further be noted that the webs 13 and 14 (and/or 13' and 14') need not have clean sharply defined edges and surfaces and may even have some discontinuities, since tests indicate that roughly formed beads do yield the best attenuation of whistling.

It can be seen from the foregoing description that the present invention provides a novel corrugated tubing construction and method of manufacture so as to yield a unique tubing configuration which eliminates whistling.

Although this invention has been described with respect to its preferred embodiments, it should be understood that many variations and modifications will now be obvious to those skilled in the art, and it is preferred, therefore, that the scope of the invention be limited not by the specific disclosure herein, but only by the appended claims.

Claims

The embodiments of the invention in which an exclusive privilege or property is claimed are defined as follows:

1. Flexible conduit means employed as a confined passageway for a fluent medium comprising:

a hollow tubular-shaped member formed of a thermoplastic material having a resiliency enabling said member to be bent or compressed and to cause said member to return to its normal tubular shape upon release of bending or compressional forces, said tubular-shaped member having a corrugated configuration such that the exterior peaks and valleys of the exterior surface respectively form the interior valleys and peaks of the interior surface, said corrugations further contributing to the aforementioned resiliency characteristics;

at least one slender elongated web of plastic material being provided within the interior of said tubular member along an appreciable portion of the entire length of the corrugated configuration;

said web extending from interior peak to interior peak and being joined to each of said peaks;

said web being formed of the same thermoplastic material as said tubular member.

2. The conduit means of claim 1 wherein said web is arranged in a substantially helical manner.

3. Flexible conduit means employed as a confined passageway for a fluent medium comprising:

a hollow tubular-shaped member formed of a thermoplastic material having a resiliency enabling said member to be bent or compressed and to cause said member to return to its normal tubular shape upon release of bending or compressional forces, said tubular-shaped member having a corrugated configuration such that the exterior peaks and valleys of the exterior surface respectively form the interior valleys and peaks of the interior surface, said corrugations further contributing to the aforementioned resiliency characteristics;

at least first and second slender elongated webs of plastic material being provided within the interior of said tubular member along an appreciable portion of the entire length of the corrugated configuration;

said webs being arranged at spaced intervals and extending from interior peak to interior peak and being joined to each of said interior peaks;

said webs each being formed of the same thermoplastic material as said tubular member.

4. The conduit means of claim 3 wherein said webs are each arranged in a substantially helical manner.

5. The conduit means of claim 1 wherein at least a portion of said web is arranged in a substantially helical manner.