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Publication numberUS3173196 A
Publication typeGrant
Publication dateMar 16, 1965
Filing dateNov 2, 1959
Priority dateNov 2, 1959
Publication numberUS 3173196 A, US 3173196A, US-A-3173196, US3173196 A, US3173196A
InventorsGrimm Donald F
Original AssigneeFromson H A
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Method of producing a double-walled tube with one of the tubes having integral therewith projecting fin means radially separating the tubes
US 3173196 A
Abstract  available in
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Claims  available in
Description  (OCR text may contain errors)

March 16, 1965 D. F. GRIMM 3,173,196

METHOD OF PRODUCING A DOUBLE WALLED TUBE WITH ONE OF THE TUBES HAVING INTEGRAL THEREWITH PROJECTING FIN MEANS RADIALLY SEPARATING THE TUBES Filed Nov. 2, 1959 2 Sheets-Sheet l /0 F 5 Z5 226 w /////J m II/IIIIIIIIIII/I March 16, 1965 D. F. GRIMM METHOD OF PRODUCING A DOUBLE WALLED TUBE WITH ONE OF THE TUBES HAVING INTEGRAL THEREWITH PROJECTING FIN MEANS RADIALLY SEPARATING THE TUBES 2 Sheets-Sheet 2 Filed Nov. 2, 1959 INVENTOR.

Unified States Patent 4i 3,173,196 I I l METHOD OF PRODUCING A- DOUBLE WALLED TUBE WITHONEDF TETUBESHAVEWG INTE- GRAL THEREWITH PRQIEC'I'ING F IN MEANS .RADIALLY SEPARATEJG THE TUBES Donald F. Grimm, Southfield, Micln, .assignor, by mesne assignments, to Howard A. From'son, Easton, Conn. FiledNov. Z, 1959, Ser. No. 850,156 11 Claims. (Cl. 29-1573) The present inventio'n relates to a method of producing a double-walled tube having a radially separated inner and outer tubes.

One object of the present invention is to provide a new and improved method of making a double-walled tube having radially separated inner and outer tubes.

In accordance with certain aspects of the present invention, one of the tubes is so formed as to define integral therewith radially extending spacer fins. If the inner tube is-the one provided with the fins, these fins extend radially outwardly from the outer surface of the inner tube. Where the outer tube is the one provided with the fins, these fins extend radially inwardly from the inner surface of the outer tube; The inner tube is collapsed, inserted into the outer tube and inflated outwardly to form the inner tubular component of the double-walled tube. The inner and outer tubes are so dimensioned, that upon inflation of the inner tube, the fins on one tube come into direct contact with the adjacent surface on the other tube.

Other objects and features of the invention will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawings, illustrating preferred embodiments of the invention, wherein:

FIGURE 1 is a fragmentary perspective view of'tubular stock used in the practice of the present invention.

FIGURE 2 is an end view of the stock shown in FIG- URE 1 after it has been flattened.

FIGURE 3 is an end view of the stock shown in FIGURE 2 after it has been elongated by rolling.

FIGURE 4 is an end view of reformed tube produced by expanding the rolled stock of FIGURE 3.

FIGURE 5 is a view of stock produced by flattening the tubular stock as shown in FIGURE 2, and there after folding the flattened stock preparatory to rolling.

FIGURE 6 is an end view of the stock shown in FIGURE 4 after it has been reduced in thickness and elongated by rolling.

FIGURE? is an end view of reformed tubing produced by expanding the stock shown in FIGURE 6.

FIGURE 8 is an end view of stock of the type shown in FIGURE 2 provided with a double fold.

FIGURE 9 is an end view of the stock shown in FIGURE 8 after it has has been reduced in thickness and elongated by rolling. I

FIGURE 10 is an end view of the partially and completely reformed tube produced by expanding the rolled stock of FIGURE 9.

FIGURE 11 is a view of stock produced by simultaneously collapsing and folding tubular stock of the type shown in FIGURE 1.

FIGURE 12 is an end view of the stock shown in Ice FIGURE 15 is a view similiar to FIGURE '14 showing a double walled tube assembly resulting from tubes 'of slightly different fin configuration;

The present invention'relates generally to a; type of tubing produced by first providing relatively. thick Walled tubular stock 10 as shown in FIGURE 1.] Stock of this type may be producedby extrusion orotherwise. This tubular stock is first collapsed to produce the fiat stock shown at 14 in FIGUREZ whereit will'be' observed that the central cylindrical opening 12 of the stock.-l0' now appears as a closedslit 16. .The ,flatstock 14 ofFIG- URE 2 isnow further processed. by passing. it through pairs of reducing rolls'tnot shown) which hasthe effect of reducing the wall thickness of the stock and wire spondingly, elongating the stock .to. the. relatively. thin closed tube in the form of a ribbon. By ribbon is meant astrip having a Width greater than the thickness indicatedatlS. in FIGURE 3. It willbe observed that the initial wall 'thickness .of the tubular stock or ribbon of FIGURE 1 determines the height of 'fin portions 29 of the rolled strip tubing shown in FIGURE. 3.

Finally, the. rolled strip tubing 18. is reformed into tubing by opening up the closed slit 16 by suitable processes which .form no part of the present invention.

However, it will be .noted that the tubing may be-re formed by internal fluid pressure, mandrels, or the like.

A comparison 'of FIGURES'S and 4 .makes vit apparent that the fin portions 20 of the flattened strip tubing shown in FIGURE 3 will appearv as radially. outwardly projecting axially extending fins 22 on the reformed or expanded tube 24. i

.The foregoing process and product is at present known and the i'mprovementherein involves an improvement in the finished reformed tube residing in the provision of additional radially projecting axially extending integral fins, at least two-of which project radially outwardly and one or more of which project radially inwardly. 1 1

.Reference is now made to FIGURES 5-7 illustrating the present invention. In this case tubular stock is flattened and folded to produce relatively thick walled stock 26 having a closed slot 28. The stock 26 is elongated by rolling tov produce the relatively thin,walled stock-3tl having fin forming portions .32, 34, '36. and 38. When the stock 30 of FIGURE 6 is expanded to formthe tube 4% the. fins 32, 34. and 36 are. radially outwardlyprojecting axially extending fins and the fin 38 is a radially inwardly projecting axially extending fin. Referring now to FIGURES 8-10 the tubular stock is flattened and provided with. a.double :fold to produce the substantially S shape stock-42 of FIGURE 8. This stock is reduced in thickness and is elongated by-rolling to form the relativelythin walled stock 44 ofFIGURE 9.

When this rolled stock is reformed into generally tubular shape some of the tin forming portions providednby the folding operation will appear at the inside of the tube and some of the fin forming portions will appear at the outside ofthe tube. Specifically,.relatively thick fin forming portions 46 and 4-8will .appear at the outside of the reformed tube 50. Relatively thinner fin forming portions52 and 54 will also appear at diametrically opposite portions on the outside of -the tube 50. The relatively thinner fin forming portions 56 and 58 appear at dia metrically opposite portions at the inner surface of the tube 50. t I

Referring now to FIGURES 11 13 there is. illustrated a variation of the foregoing. .In this case relatively thick tubular stock is simultaneously folded and flattened to produce the stock illustrated at 60 in FIGURE 11.. It willbe appreciated that stock of this shape may be produced by forming diametrically opposite lateral portions of tubular stock inwardly to produce the folds or creases 62 while the stock is simultaneously flattened.

After the stock is flattened and folded to the shape shown in FIGURE 11, it is rolled to reduce the wall thickness and to elongate the stock. After rolling the flattened and folded material is in the condition illustrated at 64 where it will be observed that it includes fin forming portions 65, 66, 67, 68, 69 and '70. In this case it will be observed that all of the fin forming portions 65, 66, 67, 68, 69 and 70 are of substantially equal thickness. \Vhen the material 64 is reformed into the tube illustrated at 72 it will be apparent that the fin forming portions 67 and 68 appear at the inside of the tube, whereas the fin forming portions 65, 66, 69 and 70 appear at the outside of the tube.

A review of the FIGURES 3-13 indicates that in general, where the rolling operation is carried out in such a way as to produce elongation without increasing the width of the stock, the thickness of the fins is usually twice the thickness of the tube wall after the material has been reshaped in tubular form. In some cases, as for example the fins 32 of FIGURE 7 and the fins 46 and 48 of FIGURE 10, the fin thickness is equal to approximately four times the wall thickness of the finished tube.

Similarly, the height of the tube is approximately equal to the original wall thickness of the tubular stock prior to the rolling operation.

While the production of round tubes is illustrated herein, it will of course be appreciated that the tubes may be opened up to square, oval, or other non-circular shape.

It will also be understood that the flattened tubes may be partially rolled, then folded, and thereafter rolled to final form in folded condition.

Referring now to FIGURES 14 and there is illustrated a modified construction made possible by the use of internally and externally finned tubes produced in accordance with the foregoing description.

In FIGURE 14 there is shown a compound tube structure comprising an inner tube 80 and an outer tube 81 in which the inner tube is nested. The inner tube 80 is provided with a single radially inwardly projecting axially extending fin 82 and three radially outwardly projecting axially extending fins 84, 85 and 86. The outer tube 81 is provided with a single radially inwardly projecting axially extending fin 87 and three equally spaced radially outwardly projecting axially extending fins 88, 89 and 90. It will be recognized that the inner and outer tubes 80 and 81 are essentially of the form shown in FIG- URE 7.

The inner and outer tubes are assembled together in such a way that the inwardly projecting fin 87 of the tube 81 is adjacent the inwardly projecting fin 82 of the tube 80. Thus, the fins 84, 85,86 and 87 constitute struts interconnecting the inner and outer tubes 80 and 81, maintaining the inner tube in properly centered relation in the outer tube, and also constituting both heat conducting elements extending between the inner and outer tubes as well as means defining four circumferentially separated axially extending passages 91, 92, 93 and 94.

In FIGURE 15 there is shown a similar arrangement which differs only in that the inner and outer tubes 95 and 96 are each provided with two radially inwardly projecting fins 97 and 98 respectively and four radially outwardly projecting fins 99 and 100 respectively.

While FIGURES 14 and 15 show both the inner and outer tubes provided with fins, it will of course be apparent that either of the tubes may be plain, and only one provided with fins.

The double wall tubing may be constructed by first shaping the outer tube to its tubular form, thereafter inser'ting the inner tube in folded and flattened form, and subsequently expanding the inner tube by fluid pressure or otherwise into the final position.

Alternatively, both inner and outer tubes may be brought to tubular condition after which they may be assembled together in approximately concentric relation. Thereafter, force may be applied to the inner surface of the inner tube by fluid pressure or otherwise, expanding the inner tube so as to bring about positive firm metal to metal contact between the free edges of the fins extending between the inner and outer tubes.

The drawings and foregoing specification constitute a description of the improved tubing having a plurality of inwardly and/or outwardly extending axial fins and the method of producing the same in such' full, clear, concise and exact terms as to enable any person skilled in the art to practice the invention, the scope of which is indicated by the appended claims.

What I claim as my invention is:

l. The method of making double walled tube struc ture which comprises flattening and folding a first tubular stock, rolling the flattened and folded stock to reduce wall thickness and to elongate the stock, and thereafter opening the rolled stock to form a first thin walled tube having at least one longitudinally and radially inwardly extending integral fin; flattening a second tubular stock of slightly smaller transverse dimensions than said first tubular stock, rolling the second tubular stock to reduce wall thickness and to elongate the stock; inserting the rolled second tubular stock into the first thin walled tube, and thereafter opening the second rolled tubular stock to form a second thin walled tube disposed within said first tube and having at least a pair of longitudinally and radially outwardly extending fins, the fins of both of said tube cooperating to space the second inner tube from the first outer tube.

2. The method of making double walled tubing which comprises flattening and folding tubular stock in such a way as to provide at least three outwardly folded creases, rolling the stock to reduce its wall thickness and to elongate stock, inserting the rolled stock in a tubular member, and opening the rolled stock to form an inner tube having at least three longitudinally and radially outwardly extending positioning fins, spacing the inner tube from said tubular member.

3. The method of making double walled tubing which comprises flattening and folding tubular stock in such a way as to provide at least three outwardly folded creases, rolling the stock to reduce its wall thickness and to elongate the stock, inserting the rolled stock in a tubular member of predetermined size, and opening the rolled stock to form an inner tube having at least three longitudinally and radially outwardly extending positioning fins dimensioned to engage the inner surface of said tubular member, spacing the inner tube from said tubular memher.

4. The method of making double walled tubing which comprises flattening and folding tubular stock in such a way as to provide at least three outwardly folded creases, rolling the stock to reduce its wall thickness and to clon gate the stock, inserting the rolled stock in a tubular member of predetermined size, opening the rolled stock to form an inner tube having at least three longitudinally and radially outwardly extending positioning fins dimensioned to engage the inner surface of said tubular member, spacing the inner tube from said tubular member, and applying internal pressure to said inner tube to expand the same to provide firm metal to metal contact between the fins of said inner tube and said tubular member.

5. The method of making double walled tubing which comprises folding and flattening a metal inner tube to cause it to have a cross-sectional shape such that in folded and flattened condition it can be inserted within an outertube having an internal diameter no greater than the external diameter of the opened up inner tube, rolling the inner tube in a direction to increase its length without. appreciably increasing its internal diameter thereby reducing the wall thickness of the inner tube and producing both internal and external rib-forming portions, inserting the elongated flattened folded inner tube into the outer tube, opening up the inner tube into contact with the inner surface of the outer tube by the application of internal pressure therein, and selecting the dimensions of the tubes such that when the inner tube is fully opened up the contact between the inner and outer tubes is limited to the outer edges of the outer ribs on said inner tube.

6. The method of making double-walled tube structure which comprises providing an outer tube, inserting a collapsed inner tube within said outer tube, both of said tubes having integral radial fin-forming projections extending toward the other of said tubes, and opening up said inner tube by the application of internal pressure to produce firm contact between the free edges of the fins formed on one tube with the adjacent surfaces of the other tube, and to thereby radially separate the tubes in the regions of said fins.

7. The method of making double-walled tube structure which comprises providing an outer tube, inserting a collapsed inner tube within said outer tube, at least one of said tubes having integral radial fin-forming projections extending towards the other of said tubes, and opening up said inner tube by the application of internal pressure to produce firm contact between the free edges of the fins formed on one tube with the adjacent surface of the other tube, and to thereby radially separate the tubes in the regions of said fins.

8. The method as described in claim 7, wherein the collapsed inner tube has integral therewith said fin-forming projections.

9. A method of making a double-walled tube comprising the steps of producing a combination consisting of an outer tube, and a ribbon in the form of a collapsed inner tube inside the outer tube and having an opening defining the inner periphery of the inner tube when said ribbon is inflated, and having also side marginal sections integral therewith and extending laterally of the ribbon beyond said opening, the lateral width of said marginal sections being greater than the thickness of the tube Walls in the ribbon between said marginal sections, whereby said marginal sections form outer fins when said ribbon is inflated, and shaping said double-walled tube from said combination into a form in which said outer tube is wide open and including the step of inflating said ribbon while in said combinaton to form the inner tube with said marginal sections in the form of fins extending between said tubes from the outer periphery of said inner tube to the inner periphery of said outer tube to space said tubes substantially radially in the regions of said fins, the

inner diameter of the outer tube being so related to the outer diameter of the inner tube and to the height of said fins as to cause said fins to extend to the inner surface of said outer tube in firm contact therewith in shaped condition of said double-walled tube.

10. The method as described in claim 9, wherein said ribbon has folds defining internal fins when said ribbon is inflated.

11. A method of making a double-walled tube comprising flattening and folding a metal inner tube With sufficient folds to form a ribbon having a width substantially less than the width said inner tube would have if said inner tube were merely flattened to bring the two opposite halves of the inner tube in face to face contact, said ribbon also having an opening defining the inner periphery of the inner tube when inflated and two fin-forming side marginal sections extending laterally of the ribbon beyond said opening, rolling the flattened, folded ribbon in a direction to reduce the thickness of the walls of the inner tube While maintaining the lateral widths of said fin-forming sections greater than the thickness of said Walls, said fin-forming sections being located to define diametrically opposite fins upon inflation of said inner tube, inserting the rolled, flattened, folded inner tube into an outer tube, and inflating the inner tube inside said outer tube by the application of internal pressure therein to form an opened up inner tube with diametrically opposite fins extending radially outwardly therefrom, and spacing said tubes in the regions of said fins, the internal diameter of the outer tube being so related to the transverse dimensions of the rolled, flattened, folded inner tube as to permit said rolled, flattened, folded inner tube to be inserted into said outer tube and being so related to the external diameter of the inner tube and to the height of said fins when inflated as to cause said fins to firmly contact the inner surface of the outer tube.

References Cited by the Examiner UNITED STATES PATENTS 167,688 9/75 Pufi'er 29421 813,918 2/06 Schmitz 138-62 X 904,189 11/08 Everson 29-523 2,001,643 5/35 Wilcox 29534 2,132,565 10/38 Graham 29523 2,611,585 9/52 Boling. 2,633,414 3/53 Boivinet 29523 2,643,027 6/53 Fink 13853 X 2,780,000 2/57 Huet 29534 FOREIGN PATENTS 190,585 12/22 Great Britain.

WHITMORE A. WILTZ, Primary Examiner. EDWARD V. BENHAM, Examiner.

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US3243986 *Oct 1, 1963Apr 5, 1966Halstead Metal Products IncProduction of large diameter thin-walled tubing
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Classifications
U.S. Classification29/890.36, 29/890.49, 138/114, 72/370.18, 138/109, 29/421.1, 165/154, 165/179, 138/148, 138/112, 72/368, 29/523, 29/455.1
International ClassificationB21C37/06, B21C37/14, F16L9/18
Cooperative ClassificationB21C37/14, F16L9/18
European ClassificationF16L9/18, B21C37/14