US2731070A - Method and apparatus for forming reinforced tubing - Google Patents

Description

-Jan. 17, 1956 w. E. MEISSNER 2,731,070

METHOD AND APPARATUS FOR FORMING REINFORCED TUBING Filed Nov. 20, 1952 rlmxrlllllwllln VI 2a INVENTOR.

WILL/A M E. M516 .SNER

2a a 203 20c W BY 30 F g-z -32 rra/wvry.

United States Patent METHOD AND APPARATUS FOR FORMING REINFORCED TUBING William E. Meissner, New York, N. Y.

Application November 20, 1952, Serial No. 321,672

20 Claims. (Cl. 154--5) In my prior patents numbered 2,608,720 and 2,609,002 I have disclosed an improved form of flexible tubing and methods for making it. The tubing comprises walls of one or two thicknesses of plastic material reinforced by a-helical strand or wire either of plastic or metallic material.

The primary object of the present invention is to provide an improved method and apparatus for producing a flexible tube of this type. Another object of the invention is to provide a method and apparatus for producing such tubing in which the plastic wall material is extruded concurrently with the spiral winding thereof about the rotating mandrel. An ancillary object is to provide a method and apparatus for producing such tubing in which the helical reinforcing element may be preformed into its helical configuration and sprung into proper relationship with the spiral wrapping of the plastic wall material in a continuous operation. This makes it possible to utilize a tempered metallic wire spring in the formation of such tubing. It also permits the use of a plastic reinforcing element which has been preformed in the helical configuration and set in such configuration by tempering or annealing operations which require a different temperature of heating than could be performed upon the element after it is incorporated in the tubing because of the different thermal characteristics of the plastic wall material thereof. Other objects and advantages of the invention will be apparent from the drawing and description thereofv hereinafter.

In the drawing, which is illustrative of the preferred embodiment of the invention,

Figure l is an elevation view, with parts in section, of one embodiment for carrying out the invention,

Figure 2 is a section taken on line II-II of Figure 1,

Figure 3 is a longitudinal section through a portion of one wall of the tubing showing the relationship of the reinforcement to the wall material in a preferred embodiment of the tubing formed; 7

Figures 3a, 3b and 3c are views similar to Figure 3 of modified embodiments of the tubing; Y

Figure 4 is a longitudinal cross section of the lower end of the mandrel sleeve; and

Figure 5 is a section of a wall forming strip and cooperating belt.

As shown in the drawing, the present invention provides a mandrel comprising a sleeve 14 rotatable on a stationary downwardly projecting member 3, preferably of cylindrical shape, which is fixedly supported in a yoke or bracket 4 and is preferably in the form of a hollow tube. v

The member 3 may be simply a cylindrical rod for operation with some materials. -However, it may be desirable for some materials to heat the mandrel 14 in ternally. For this purpose, the mandrel 14 and member 3 should be of heat-conductive materials and the member 3 is a hollow tube having the associated structure shown. Thus, theupper end of the hollow tube 3 may communicate with a vessel 5 and a partition 6 may be 2,731,070 Patented Jan. 17, 1956 disposed within the vessel 5 so as to divide the lower portion thereof into two parts. The partion 6 may extend downwardly into the tube 3 to a point 6a which is just short of the closed end wall 7 of the tube 3. The partition 6 thus divides the chamber within the tube 3 into two semi-cylindrical'halves which communicate at the lower end of tube 3 below the edge 6:: of the partition. In addition, each of the semi-cylindrical passages or spaces within the tube 3 communicates with a respective one of the'two parts or regions within the lower portion of vessel 5 on either side of the partition 6. An agitator 8 may be disposed on the shaft 9 of a motor 10 mounted upon a transverse bar 11 carried on the upper walls of the vessel 5. In addition, heating element 12, such as a helical heating element or a hollow tube or coil for conveying a heat transfer fluid, such as steam, therethrough may be disposed in the vessel 5 and if desired it may extend clear down into one of the semi-cylindrical spaces within the tube 3. A thermostat 13 may be pro- 'vided within the vessel 5 so that its effective element, such as a bi-metallic switch element, is within a body of the heat transfer medium contained within the vessel 5 and tube 3. A heat transfer medium of any suitable type such as glycerine, molten salt, such as any of the salts mentioned in my prior Patent 2,608,720 or any of the salt mixtures mentioned therein may be provided in the vessel 5 and the thermostat 13 may be disposed in any suitable position within the vessel 5 or within one of the semicylindricalchannels within tube 3 depending upon the circulatory eifect of the agitator 8. The thermostat 13 is connected to the heating means in conventional fashion to control the operation thereof in accordance with the temperature within the vessel 5. For example, the thermostat may be connected in the circuit to the electrical heating coil 12 so as to open the heating circuit when the temperature exceeds a certain value and closes the circuit when it decreases to a point below a predetermined value. The agitator 8 is arranged to cause circulation of the fluid medium within vessel 5 down one side of the partition 6 and up the other and over its top. The vessel 5 may be lagged with a heat-insulating material but the tube 3 and mandrel 14 are of a highly conductive metal so as to effect rapid heat transfer through its walls.

. A mandrel sleeve 14 is rotatably mounted about the tube 3 and extends downwardly about the tube 3 to a point 15 considerably beyond the end 7 of tube 3. The sleeve 14 is provided with a flange 16 at its upper end which is mounted in a radial and thrust bearing 17 to facilitate the-rotationof the sleeve 14 about the tube 3. The lower end of tube 14 maybe turned inwardly as at 18 (see Figure 4) and provided with a terminal cap 19 of heat-insulating material for the purposes hereinafter described.

A strip or band 20 of the plastic material intended to form the wall proceeds about a guide roll 21 and, if desired, a guide 22 to a position adjacent the mandrel and extending in a direction at an inclination to the axis of the sleeve 14 underneath a belt 23 which is wound several times in helical fashion about the sleeve 14 with the edges of its convolutions abutting against each other until it leaves the sleeve 14 and proceeds about a power driven pulley or roller 24. The belt 23 returns back to the guide pulley 25 on the other side of the sleeve 14 and as it passes from roller 24 to pulley 25 it must be twisted in a fashion tocompensate for the twists imparted during the helical winding about the mandrel or sleeve 14. The belt 23 therefore while wrapping the strip 20 in helical convolutions about the sleeve 14 exerts pressure upon the wall-forming strip 20.

The strip 20 may be formed concurrently by means of the extrusion apparatus 26 which may be of any convcntional form and provided with a forming slit adapted to provide the desired cross-section ofthe strip 20. Various cross-sections may be employed, those in Figures 3, 3a 3b and 5 being preferred. The extrusion apparatus 26 may errtrude a molten mass of a plastic material or a solution of plastic material in a volatile solvent, the strip 20 being set in its proper form by the rapid cooling or evaporation of solvent from the material after it leaves the orifice or slit of the extrusion system.

The strip 20 as it reaches the guides 21 and 22 and the mandrel sleeve may be warm orhot but is preferably at a temperature-below its .point of .tackiness so that it does not tend to adhere to the : guides 21 and 22 appreciably. Thisgpreheatedeondition of the 'strip'20 as it reaches the mandrel '14 allows the rate of winding about the mandrel to be increased since a correspondingly lesser rise in temperature of therplastic strip 20 is needed to bring it to the tacky or partially fused condition required to cause it to coalesce at its edges.

To prevent sticking of the strip 20 to the sleeve 14 when the latter is internally heated, and/or to facilitate the sliding of the spirally wrapped strip axially of the sleeve, a lubricating liquid, such as .glycerine, may be applied to the strip 20 by means of a'wick-26a connected to a container or vessel27 for thelubricant.

The helical reinforcing element 28, such as a tem pered metallic spring or a plastic mono-fil having a greater resiliency and stiffness than the plastic material which makes up the strip 20, is supplied by a tubular receptacle 29. The receptacle 29 is somewhat larger in diameter than the spring helix, and may support a great length of the helical coil in a straight line. Receptacle 29 may be rotatably mounted in one or more bearings 30 and has a discharging opening 31 adjacent the mandrel 14 just above the position in which the belt 23 winds on the strip 20. The 'outer diameter of the mandrel 14 should be approximately the same as the inside diameter of the helix of the preformed reinforcing element 28, though some dilference in these diameters may be permissible. If the mandrel 14 is of somewhat greater diameter, it may serve to compensate for any failure of the element 28 to return completely to the-original size of helix after springing about the rnandrel. A guide 32 may bedisposedadjacent the mandrel about 150 to 170 or so around from the center of the discharge opening 31. This difference in diameter may be necessary or desirable when the reinforcing element is made of certain plastic materials or 'even of highly flexible metallic springs.

Heating means, such as'a heat-transfer coil or electrical heating coil 33 is preferably provided 'about'the discharge-end of tube 29 for heating the springelerne'nt 28 to a temperature-sufiiciently 'high'tocause'coalescence of the adjoining or -overlapped"edges of the convolutions of the plastic material 20. The guide 32 is 'disposedso that when the wire or strand 28 is drawn from'itshelix within the tube 29'through the guide 32 to the mandrel -14, the strand or wire is directed at-the properangle of helix and into alignment with the upper marginal edge of strip 20 just before the strip enters the second convolution from the top where it is abutted with, or covered or overlapped by, the lower marginal edge of the approaching portion of the strip 20. This lays down the wire or strand 28 between the adjoining or overlapped edges as shown inv Figures 3, 3a, 3b, or 3c. A blast of heated air may be directed by nozzle 37 into the space between the edges of the plastic strip 20 just before they areoverlapped with thestrand 28 therebetween.

As the belt23 proceeds to wind the strip'20 and reinforcing 'element 28 about the mandrel, the heat introduced by the element 28 alone or by the-internal mandrel 14 alone, or by the nozzle or nozzles 37 aloneor by any two or all three of these'expedients,:.causes coalescence of the adjoined or ovcrlappededges and the cmbedding of the reinforcing element 28 within the coalesced "mass.

As the formed tubing proceeds downwardly out of the embrace of the belt 23, a blast of cooling air may be provided by one or more nozzles 38 provided on a conduit 39 connected to a suitable source for a cool or refrigerated air. This serves to set the juncture of the tubing before it leaves the insulated end 19 of the mandrel 14.

Figure 3 shows in section a portion of a preferred form of the finished tubing of which the plastic strip 20 has an outer arched surface 20a and one of its edges 2% is overlapped by the other edge 200 of the next convolution of the plasticstrip and the reinforcing element 28 is embedded within the coalesced edges 2% and 2th. The strip 20 from which such material is made may have the cross-sectional shape shown in Figure 5 when initially formedand before being made into the tube. The cross-section of the belt 23 adapted to cooperate with. the :strip 20 is shown-also in Figure 5 within the dotted outline. By providing such a belt with a concavity between its edges which is complementary in shape to the convexity of the surface 20a pressure is properly applied to the overlapped edges 20b and 200 of the tubing.

{Figure 3a shows a modification in which the edges 20b and 20c of adjacent or contiguous convolutions of the wall strip 20 are joined to the intervening reinforcing element 28 of plastic material adapted to form a .good adhesive bond with the wall material when coa lesced therewith. Figure 3b shows a modification in which theadjacent edges 20b and 200 are in contact and the reinforcing element 28 is laid upon the juncture therebetween so that coalescence causes the element to become partially or completely embedded therein. Figure 3c shows -a modification using a plurality of superposed strips. The first 20d to be laid down has no over- :lap between adjacent helical convolutions but rather they preferably abut against one another. The strand or wire 28 is wound helically thereabout with its body about midway of the width'of its convolution of 20d. A-s'econd strip 20a -is helically wrapped between'the convolutions of the strand 28 and a third strip 20 is then belie-ally wrapped about the whole with its abutting edges about midway of strip 20c.

It is to be understood that the cross-sections of strip 20-shown in Figures 3t, 3:1,3b, 3c, and Sare representative and can be varied widely. As pointed out in :my prior patents, the portion of the tubing between adjacent convolutions of the reinforcing strand, such as strand 28, should have the center ofgravity disposed outwardly from the-cylinder of the helix of the strand :so that when the tubing is bent, thezportion 0f the wall material-20 between adjaeentconvolutions ofthe reinforcing strand bows outwardly.

By the system ofthe present invention, the reinforcing element 28 may be preformed in itshelicalconfiguration beforeincorporation within the tubing. This has the advantage that the reinforcing element can be tempered, if it is of a-metallic wire, or properly heat-treated, if it is a plastic strand, to impart to it the desired resiliency and stiffness-for providing good husky reinforcement to the final tubing. If a reinforcing strand or wire were to be initially formed into helical configuration by wrapping about the'tube simultaneously with the wrapping of the plastic strip 20, there would be a tendency for the strand material to flex outwardly from its helical configuration a'fte'r leaving'theinitial windingposition andgenerally the plastic material'of the strip 20 forming-the walls of the tube is such-that it wouldnot be'possible toheat-treat or temper the reinforcing elementafter the formation of the tube without damaging the wall portions thereof.

While a-single thickness of plastic-material 20has been shown spirally wrapprd about a mandrel to form a tube :in Figures 3, 3a, and 3b, additional thicknesses-of such "a material may be employed, as in Figure 30, so that the final tube may comprise two or more layers of the plastic strip material with the reinforcing element embedded therein. The angle of helix of the several layers may be the same or opposite. While a single reinforcing element is shown, a plurality thereof may be employed and fed to the mandrel so that their convolutions would be in side-byside relationship either in contact or somewhat spaced apart as shown in my prior patent 2,609,002. It will be of course understood that the leading end of the plastic material 20 and the reinforcing element 28 may be initially applied to the rotating mandrel by hand or any suitable mechanical means.

It is to be understood that changes and variations may be made without departing from the spirit and scope of the invention as defined in the appended claims.

I claim:

1. A method for forming a flexible tube comprising helically wrapping a plastic strip into a tubular shape with its edgesin contiguity while concomitantly guiding a preformed helical reinforcing element longitudinally into position along the contiguous edges of the strip, coalescing the material of the contiguous edges to the element, and then setting the tubular assembly of element and strip.

2. A method for forming a flexible tube comprising helically Wrapping a plastic strip into a tubular shape with its edges in contact while concomitantly guiding a preformed helical reinforcing element longitudinally into position along the contacting edges of the strip, coalescing the material of the contacting edges to the element, and then setting the tubular assembly of element and strip.

3. A method for forming a flexible tube comprising helically wrapping a plastic strip into a tubular shape with its edges overlapping while concomitantly guiding a preformed helical reinforcing element longitudinally into position between the overlapped edges of the strip, coalescing the material of the overlapped edges to embed the element therein, and then setting the tubular assembly of element and strip.

4. A method for forming a flexible tube comprising continuously extruding a mass of plastic material through a slit to form a continuous band or strip, continuously wrapping the strip in helical fashion into a tubular shape with its edges in contiguity, directing a preformed helical reinforcing element longitudinally into position along the contiguous edges of the strip, applying heat at least to the contiguous edges adjacent the element to eflect adhesion thereof to the element, and then setting the tubular assembly of element and strip.

5. A method in accordance with claim 4 in which the element is heated as it proceeds to said position along the contiguous edges of the strip to a temperature sufiicient to render the edges adhesive.

6. A method as defined in claim 4 in which heat is applied internally of the tube formed of the strip and element.

7. A method as defined in claim 4 in which heat is applied to the edges of the adjacent convolutions of the strip adjacent the point where they first approach each other.

8. A method in accordance with claim 4 in which the element is heated as it proceeds to said position along the contiguous edges of the strip to a temperature suflicient to render the edges adhesive, and the edges are overlapped with the element therebetween.

9. A method as defined in claim 4 in which heat is applied internally of the tube formed of the strip and element, and heat is applied to the edges of the adjacent convolutions of strip adjacent the point where they first approach each other.

10. A method in accordance with claim 4 in which the element is heated as it proceeds to said position along the contiguous edges of the strip to a temperature sufiicient to render the edges adhesive, and heat is applied to the edges of the adjacent convolutions of the strip adjacent the point where they first approach each other.

11. Apparatus for-forming flexible tubing comprising a mandrel, means for helically Winding a continuous strip about the mandrel and simultaneously advancing the convolutions thereof axially of the mandrel, means adjacent the position of said winding means for guiding a preformed helical reinforcing element into helical disposition about the mandrel, and means adjacent the winding means for applying heat to the element before it reaches the guiding means.

12. Apparatus for forming flexible tubing comprising a hollow mandrel, means for mounting the mandrel for rotation about a vertical axis, means for helically Winding a continuous plastic band about the mandrel and simultaneously advancing the convolutions thereof downwardly and axially of the mandrel, means adjacent the upper end of the winding means for guiding a preformed helical reinforcing element into helical disposition about the mandrel with its convolutions adjacent the edges of the convolutions of the helically wound band, and means for applying heat to the preformed helical element, said heating means being positioned outside the mandrel adjacent the guide means.

13. Apparatus as defined in claim 12 comprising means for directing heat against the mandrel adjacent the point where the edges of the convolutions of the band first come into proximity with each other about the mandrel.

14. Apparatus as defined in claim 12 comprising means above the winding means for supplying a lubricant to the band.

l5. Apparatus as defined in claim 12 comprising a receptacle for storing said preformed helical reinforcing element, said receptacle comprising a tubular conduit terminating alongside the mandrel adjacent the upper end of the winding means associated therewith, and said guide means comprising a guide disposed in fixed position adjacent the mandrel and the discharge end of the conduit.

16. Apparatus as defined in claim 15 comprising cooling means disposed alongside the lower end of the mandrel below the winding means.

17. Apparatus as defined in claim 16 in which the lower end of the mandrel comprises a heat-insulating portion disposed below the cooling means.

18. Apparatus as defined in claim 17 in which the means for supporting the mandrel rotatably comprises a vertically mounted fixed cylindrical conduit having its lower end closed and having a vertical partition extending transversely of the conduit down to a point spaced above the closed end thereof, a heat transfer fluid contained within the conduit, means for circulating the fluid down one side of the partition and up the other to heat the conduit, means for heating the fluid, and thermostatic means for controlling said heating means.

19. Apparatus as defined in claim 11 comprising means for extruding a plastic material to form a continuous strip, and means for directing said strip to said helically winding means.

20. Apparatus for forming flexible tubing comprising a mandrel, means for helically winding a continuous strip about the mandrel and simultaneously advancing the convolutions thereof axially of the mandrel, a tubular receptacle for a supply of a preformed helical reinforcing element and having a discharge opening adjacent one side of the mandrel, means adjacent the position of said winding means for guiding the element discharged from said opening into helical disposition about the mandrel, and means about the receptacle near the discharge opening thereof for applying heat to the element therein.

References Cited in the file of this patent UNITED STATES PATENTS 1,985,997 Keeran Jan. 1, 1935 (Other references on following page) 7 =8 UNITED STATES PATENTS 1,539,853 Meyprs at B1. .muvmvwmr. Jan. 30, 1951 2 173 99 Campbell "Se-PL 1939 261:5,491 rris t a1 9% 18, 195 2 250 430 d July 22 1941 '2;620,51'4 Sampsdnet B1- DBC.-9, 1952 2 260 054 n O 21 1941 34625979 Harris "6t 1111. Jan. 20, 1953 2,7-07;01-7 Beare et'al. Apr. 26, 1955 2,489,503 'Sa'mpsOnet a1 Nov. 29,1949

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