US3688375A

US3688375A - Machine for manufacturing heat exchanger tube

Info

Publication number: US3688375A
Authority: US
Inventors: Herbert J Venables
Original assignee: Individual
Current assignee: Individual
Priority date: 1970-07-13
Filing date: 1970-07-13
Publication date: 1972-09-05
Anticipated expiration: 1989-09-05
Also published as: US4124125A

Abstract

Apparatus is disclosed for forming heat exchanger tubes having two helically wound foil strips each of which is provided with two lanced legs extending substantially perpendicular to the base tube. The foil stock is supplied from the interior of a coil consisting of two interleaved strips wound in a spiral form. The strips are separately fed and formed and are subsequently wound on an axially movable non-rotating tube. The winding head subassemblies are symmetrically positioned to provide dynamic balancing.

Description

145! Sept.5,1972

United States Patent Venables, III

3,134,166 5/1964 Venables ...........29/l57.3 AH 3,160,129 12/1964 Venables.................29/202D Primary Examiner-Thomas H. Eager Attorney-Harry B. O'Donnell, 111 et a1.

Herbert J. Venables, 111, Cleveland, Ohio [22] Filed: July 13, 1970 ABSTRACT Apparatus is disclosed for forming heat exchanger App1.No.: 54,304

tubes having two helically wound foil strips each of 'i 2: which is provided with two lanced 1egs extending sub- 1573 Manually perpendicular to the base tube. The foil [58] Field of Seareh....l13/1;

stock is supplied from the interior of a coil consisting of two interleaved strips wound in a spiral form. The strips are separately fed and formed and are sub- [56] References Cited UNITED STATES PATENTS sequently wound on an axially movable non-rotating tube. The winding head subassemblies are symmetrically positioned to provide dynamic balancing.

3,005,253 10/1961 Venables ...........29/157.3 AH

8 Claims, 14 Drawing figures P'A'IENTEBsEP' m: 3.688.375

SHEEY 3 BF 5 INVENTOR.

BY Mq/euwf Anne/M67044 A542: #4020041 1477 walls):

PATENTED E 5 i9 SHEET t [If 5 MACHINE FOR MANUFACTURING HEAT EXCHANGER TUBE BACKGROUND OF THE INVENTION This invention relates generally to the manufacture of heat exchanger tubes and more particularly to a novel and improved method and apparatus for forming such tubes and to a novel and improved heat exchanger tube produced by such method and apparatus.

PRIOR ART The present invention is an improvement of the inventions disclosed in my prior U.S. Pats; No. 3,005,253 of Oct. 24, 1961; No. 3,134,166 of May 26, 1964; and No. 3,160,129 of Dec. 8, 1964. Each of these prior patents relates to the manufacture of heat exchanger tubes in which the tube is helically wound with a strip of metal foil stock so as to provide a large external heat exchange surface for the efficient heat transfer through the tube wall. Although such tubing finds its greatest use in heaters and air conditioners, it may be used in many other types of equipment where efficient heat exchange is required.

SUMMARY OF THE INVENTION The apparatus for forming heat exchanger tubing in accordance with the present invention involves means for the simultaneous winding of a tube with more than one continuous strip of metal foil from a rotating winding head. In the illustrated embodiment, two strips engage the tube at tangentially and diametrically opposite points of the tube and are simultaneously wound on the tube with a double helix, so that each turn of the winding head produces twice the length of wound tubing when compared to the prior machines of my patents referred to above.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of the winding head of a preferred embodiment of this invention;

FIG. 2 is a plan view of the gear train drive for the various forming and feeding subsystems of the winding head;

FIG. 3 is a fragmentary broken section taken along 3-3 of FIG. 1;

FIG. 4 is a fragmentary section illustrating the foil lancing station;

FIG. 4a illustrates a strip after lancing;

FIG. 5 is an enlarged fragmentary section of one of the stations at which the foil is initially formed to a U- shape;

FIG. 6 is an enlarged fragmentary section illustrating the structure of one of the hemming stations;

FIG. 6a is an enlarged fragmentary section illustrating the forming operation which occurs at the throat of the hemming station;

FIG. 7 is an enlarged fragmentary section of one form of a novel and improved tube in accordance with this invention;

FIG. 7a is an enlarged fragmentary section of another form of a novel and improved tube in accordance with this invention; and

FIGS. 8-11 are schematic views progressively illustrating the manner in which the coils of foil stock are unwound as the machine operates.

DETAILED DESCRIPTION OF THE DRAWINGS My prior US. Pat. No. 3, l 34,166 discloses a winding machine for the manufacture of heat exchanger tubing in which the tubing is fed up through the machine along the center of a winding head. Such machine is provided with feed rollers which operate to straighten the tubing and to insure that the tubing is circular in section. In such prior machine a single strip of foil stock is fed into the winding head and is lanced along opposite lateral extremities. The lanced foil strip is then formed to a U- shape and is subsequently hemmed to provide a base having a lateral width greater than the spacing between the lanced legs. The formed strip is then wrapped around the tubing in a single helix.

The method and apparatus in accordance with the present invention also utilizes strips which are first lanced, are subsequently formed to a U-shape, and are thereafter hemmed to the shape substantially as illustrated in such patent. However, the illustrated apparatus in accordance with the present invention is supplied with a coil consisting of two interleaved spiral strips of stock and the two strips are simultaneously formed and simultaneously wound onto the tube with a double helix rather than the single helix of such patent.

A number of distinct advantages are obtained with the present invention when compared to my prior machines as will be discussed in detail below. However, reference should be made to all of my prior patents, listed above, for a clear understanding of the background of the present invention and of the various advantages and features realized with the inventions disclosed therein. Therefore, such prior patents are hereby incorporated by reference.

In order to simplify the understanding of this invention only the winding head is illustrated and discussed in detail. Such winding head is preferably supported on a main frame as illustrated in my prior [15. Pat. No. 3,134,166 and is driven by a lower drive gearing system as disclosed therein. The drive for feeding the tubing up through the winding head of such patent need only be modified to increase the rate of tube feeding compared to the rate of rotation of the winding head. For example, when the base width of the strip is the same as the base width of the strip formed on such prior machine, the rate of feeding of the tube is doubled by appropriate changes in the tube feed gear drive to accommodate the two strips which are simultaneously wound on the tube.

Referring to FIG. 1, the winding head, designated generally as 10, is joumaled for rotation about a vertical central axis 11. The tube 12 to be wound is fed vertically upward through a stationary guide 13 along the central axis 11. The entire winding head along with a stock support table 14 rotate in a counterclockwise direction as viewed in FIG. 1. However, the winding head 10 rotates at a speed slightly slower than the rotational velocity of the table 14. The tube 12 moves only in a vertical direction and does not rotate.

Two separate but continuous strips of

foil stock

16 and 17 indicated schematically by dotted lines, feed into diametrically opposite sides of the winding head 10. The manner in which the supply coil is wound to provide two separate strips and the manner in which the strips move from the supply coil into the head is discussed in detail below.

Each of the

strips

16 and 17 moves along a separate path to the tube 12. However, the two paths are similar and are symmetrically arranged with respect to the central axis 11. Since the two paths are similar, only one will be discussed in detail with the understanding that the detailed description applies equally to both paths. The strip 16 enters the winding head by passing around a guide roller 18 at the periphery of the winding head. The strip then extends past a guide 19, a pair of

guide rolls

21 and 22, and along a guide 23 to a lancing station 24 which is located substantially adjacent to the central axis 11. The structure of the elements forming the lancing station and the operation of lancing is discussed in detail below.

From the lancing station 24 the lanced strips 160 then passes to a first forming station 26 where the lanced strip 160 is bent to a generally U-shaped configuration. From the first forming station 26 the U- shaped strip 16b passes to a hemming station 27 wherein the strip is further formed to provide a hem at the edges of the base of the strip. From the hemming station 27 the hemmed strip 160 passes around an inclined guide roll 28 which positions the hemmed strip for winding around the tube 12.

Because of the composite movement resulting from the rotation of the winding head in a plane perpendicular to the axis 11 and the axial movement of the tube along the axis 11, the hemmed strip is wound around the tube in a helical manner wherein the lead of the helix is equal to the amount of movement of the tube which occurred during one compiete revolution of the winding head 10. The strip 17 is similarly processed and moves along a similar but opposite path through a lancing station 24, a first forming station 26 in which it is formed to a U-shape, and a hemming station 27. From the hemming station 27 associated with the strip 17 the hemmed strip 17c passes around an inclined guide roller 28 and passes to the tube 12 engaging the tube 12 tangentially directly opposite the engagement of the strip 160 with the tube.

The various elements forming the winding head 10 are symmetrically positioned with respect to the central axis 11. Therefore, the two lancing stations 24 are located on diametrically opposite sides of the axis 1 1 an equal distance therefrom. The two forming stations 26 are similarly located on diametrically opposite sides of the axis 11 equal distances therefrom. Similarly, the two hemming stations are equally spaced and diametrically opposite each other. In each instance the structure at each forming station is identical to the structure at the corresponding forming station for the other strip. Therefore, the basic structure of the winding head provides complete dynamic balancing with respect to the central axis 11. It should be understood that dynamic balance is extremely important in such machine since the winding head and the structure associated therewith is relatively large and heavy and rotates at a speed in the order of 1,600 rpm or more.

Referring to FIG. 4, the two lancing stations 24 are provided by a drive lancing roll 31 which is joumaled for rotation about the central axis 11. Similar idler rolls 32 and 33 are joumaled on the winding head 10 on opposite sides of the drive roll 31 and each cooperates with the drive roll 31 to provide one of the lancing stations 24. With this arrangement, two lancing stations 24 are provided with only three lancing rolls since the single drive lancing roll 31 functions as part of each of the lancing stations.

Each of the lancing rolls 31, 32, and 33 is formed with upper lancing teeth 34 and lower lancing teeth 36 separated by a space 37. The lancing teeth intermesh so that the idler rolls 32 and 33 are driven by the drive roll 31 at the same rotational velocity as the drive roll 31 but in an opposite direction. The lancing teeth lance opposite sides of the strip 16a as illustrated in FIG. 40 so that the strip has

cuts

41 and 42 extending in from the adjacent opposite edges, respectively, and terminating at spaced locations to provide a central uncut portion 43. Between each cut 41 and 42 is a separate fin 44 which is joined to the uncut section 43 at its inner end.

From the lancing station 24 the strips 16a and 17a move to the respective first fonning stations 26 one of which is illustrated in FIG. 5. Located at each first forming station 26 is a driven roller 40 and an idler roller 42 which are respectively joumaled for rotation about spaced and

parallel axes

43 and 45. The driven roller 40 is formed with a shallow annular groove 46 and

cylindrical surfaces

47 and 48 on either side thereof. The total height of the space 46 and surfaces 47 and 48 is at least as great as the lateral width of the lanced strips so that the fins 44 are not damaged as the lanced strips engage the periphery of the roll 40.

The idler roll 42 has a lateral width or height equal to the desired width of the U-shaped strip 16b and 17b. This roll projects into the groove 46 and cooperates with the side walls 49 to deform the strip to a U-shape in which the strip has a base 51 and substantially

parallel legs

52 and 53 extending from the opposite edges of the base 51. The two strips 16a and 17a engage their respective driven rollers 40 at a tangential location spaced from the associated idler rollers 42 and are carried along the drive rollers until they engage the idler rollers 42. At this location where the idler roller 42 projects into the groove 46, the respective strips are deformed to a U-shaped condition.

From the first forming station each of the strips passes to a second forming or hemming station having a mechanism as illustrated in FlGS. 6 and 60. Located at each hemming station 27 is a hemming assembly 56 which provides three interconnected forming

rolls

57, 58, and 59 which cooperate with an idler roll 61 illustrated in FIG. 6a. The hemming assembly 56 is a separate assembly which may be installed in the wind ing head or removed therefrom as a unit. This greatly facilitates the servicing of the machine since a separate hemming assembly 56 can be serviced and adjusted while the machine operates with another hemming assembly in position.

The hemming assembly includes an upper housing member 62 and a lower housing member 63 which are bolted together and are in turn bolted to the winding head by bolts 64. Journaled on the lower frame 63 in an antifriction bearing assembly 66 is an input drive shaft 67 provided with an internal spline adapted to fit over and be drivingly connected to a drive shaft 68. The upper end of the shaft 67 is provided with a miter gear 69 which meshes with a miter gear 71 which is journaled for rotation about a horizontal axis 72. The miter gear 71 is provided with a support shaft 73 joumaled in

bearings

74 and 76 in the lower housing 63. The roller 57 is removably mounted on the forward face of the miter gear 71 by bolts 77.

The upper end of the miter gear 71 also meshes with a miter gear ring 78 which together with the base roll 58 and a second miter gear ring 79 form a ring assembly which is mounted on the outer race 81 of an antifriction bearing assembly 82. The bearing assembly 82 is in turn supported by a pin 83 mounted between the two housings 62 and 63 on a vertical axis intersecting the axis 72. The miter gear ring 79 meshes with a miter gear 84 which is similar to the gear 71 and which supports the upper roll 59. Here again the miter gear 84 is provided with a shaft section 86 joumaled in

bearings

87 and 88 for rotation about a horizontal axis 89 which intersects the axis of the pin 83 and is parallel to the axis 72 and vertically spaced therefrom.

The three rolls 57, 58, and 59 all have substantially the same diameter and rotate at the same velocity to minimize any tendency for skidding to occur when the strip is engaged. With this gear drive the adjacent surfaces of the three rolls move in the same direction. The various elements are proportioned so that the U-shaped strip 16b and 17b engages the base roll 58 ahead of the two rolls 57 and 59. As the strip is carried into the throat as illustrated in FIG. 6a, the two legs of the strip are deformed to provide a hem portion 91 extending inwardly from the edge of the base 51. The inner faces 92 of the two rolls 57 and 59 are formed with a shallow conical shape and cooperate with the conical side faces 90 of the idler roll 61 to insure that the fins 44 are substantially coplanar with their adjacent fins and to insure that the two legs diverge slightly.

The roll 61 is joumaled for free rotation in response to engagement with the associated strip on a mounting spindle (not illustrated for purposes of simplification) which permits both vertical and radial adjustment of its position. With such adjustment the exact desired relative positioning of the side faces 90 with respect to the associated inner faces 92 can be obtained. Radial adjustment, because of the conical shape of the faces 90 and 92, provides adjustment of the total spacing therebetween and vertical adjustment permits equalizing of the spacing.

The hemmed strip 16c or 17c then passes around the associated inclined roll 28 which is positioned so that the respective strips are inclined upwardly toward the tube 12 at an angle substantially equal to the helix angle of winding. As the strips are wound on the tube the outer wall of the hem 91 is pulled tighter than the inner wall because of the difference in diameter, so the fins 44 are pulled inward and become substantially parallel.

FIG. 7 illustrates one form of a final heat exchanger tube which consists of the tube 12 and the two

strips

160 and 170 which are wound on the tube with a double helix. The helix angle is such that the lead of the helix of each strip is equal to twice the width of the base 51 of each strip and the base 51 of the strip 16c is directly opposite the base 51 of the strip 170. With such a helix angle the bases of the two strips engage opposite sides of the tube. In some instances where a spacing is desired between the two bases, the helix angle may be further increased by increasing the rate of feed of the tube during winding. This produces a space between the adjacent bases 51. In other instances where a wide space is desired, the winding head can be supplied with a single strip without changing the rate of tube feeding and a space will occur between the base of the strip along one turn and the adjacent turn which is equal to the width of the base which would otherwise be provided by the second strip.

FIG. 7a illustrates a modified form of tube wherein two strips of hemmed foil 16c and 170' are again wound on the tube 12 with a double helix. However, the base 51' of the strip 17c is wider than the base 51' of the strip 16c and the fins 44' of the strip 170' are correspondingly shorter. In this form the stock for the two strips has the same initial width even though they are formed in different proportions. The two strips, however, do not have to have the same width when the strip shapes are not identical.

Reference should now be made to FIGS. 2 and 3 which illustrate the basic drive for the various elements of the winding head 10. The entire winding head 10 is supported on a tube 101 which is rotated about the central axis 11 by a drive system as illustrated in my prior US. Pat. No. 3,160,129. The drive in the illustrated embodiment causes clockwise rotation of the winding head as viewed in FIG. 2 in response to rotation of the drive tube 101.

Extending up through the drive tube 101 is an inner drive tube or torque tube 102. Here again this tube is driven by the lower drive unit in a clockwise direction as viewed in FIG. 2, but at a slower velocity than the winding head 10. A nonrotating guide tube supports the guide 13. The drive tube 102 is formed with an internal spline 103 which engages a spline on a shaft 104journaled in

bearings

106 and 107, so that the shaft 104 is driven by the tube 102. The drive lancing roll 31 is carried by a shaft 104 and rotates therewith. Also mounted on the shaft 104 is a center drive gear 108.

Because the rate of rotation of the center drive tube 102 is slower than the rate of rotation of the winding head 10, the gear 108 and the lancing roll 31 rotate in an anticlockwise direction as indicated by the arrow 109 with respect to the winding head even though the absolute rotation of the gear 108 and lancing roll 31 is in a clockwise direction. For purposes of discussion the following description of the winding head drive refers to the rotation of the various elements of the winding head with respect to the main winding head frame as if the winding head frame were stationary and the various components of the winding head were rotated in a stationary winding head frame. It must be understood, however, that in fact the winding head itself is rotating and that the absolute rotational movement of the components is not necessarily in the directions set forth.

Because the gear 108 and the lancing roll 31 rotate about the central axis 1 1 the support bearings for these elements are not subjected to any substantial centrifugal force. Mounted in the frame assembly 111 of the winding head 10 is a pivot assembly 1 12 for each of the idler lancing rolls 32 and 33. This pivot assembly includes a pivot pin 113 supported by spaced bushings 114 and 116. During the operation of the machine the pivot pin 1 13 is clamped in its adjusted position, but it can be rotated with respect to the frame 1 1 1 for adjustment of the radial spacing of the associated

idler lancing roll

32 or 33. The pin 113 is provided with an eccentric cylindrical surface 117 which supports the inner race of a bearing assembly 118. Mounted on the external race of the bearing assembly 118 is the idler roll 32. As the drive lancing roll 31 is rotated by the drive, the idler roll 32 is caused to rotate about the axis of the eccentric portion 117. Radial adjustment of the idler roll 32 is provided by loosening a clamp nut 1 19 to release the clamping force of a clamp washer 121 to permit the, pivot pin 113 to be rotated. When the proper position is achieved, the nut 119 is tightened causing the clamp washer 121 to be pulled up against the lower side of the bushing 116 and causing it to be axially gripped by a spacer 122 which extends between a flange 123 and the upper side of the bushing 1 16. The adjustment of the pivot pin 113 is easily accomplished by the use of a wrench on wrenching flats formed at 124 on the pin.

lt should be recognized that this adjustment and mounting wherein the pivot pin 1 13 is not joumaled for rotation with respect to the frame 1 11 permits the use of smaller bearings because the mass which must be supported by the bearings 118 is the roll 32 and the mounting parts adjacent thereto. Consequently, the only centrifugal forces which must be supported by the bearings 118 as the winding head rotates are the forces resulting from the relatively small mass of the lancing roll 32 and adjacent rotating parts. Of course, these bearings must also sustain the lancing loads.

Meshing with the central gear 108 are a pair of opposite gears 126 associated with each of the hemming assemblies. These gears are located at diametrically opposite locations with respect to the central axis 11 and both rotate in a clockwise direction with respect to the frame assembly 111. FIG. 3 is a broken section so only one of these gears appears in the section.

The gear 126 is mounted on the shaft 68 which is in turn joumaled in bearings 127 and 128. The upper end of the shaft is provided with a spline which fits into the drive shaft 67 of the associated hemming assembly 56. The clockwise rotation of the gear 126 is therefore transmitted to the first miter gear 69 illustrated in FIG. 6 as movement indicated in the direction of the arrow 129. This causes movement of the lower portion of the miter gear 71 in a direction out of the plane of FIG. 6 and movement of the upper portion in the opposite direction or into the plane of FIG. 6 which is the desired direction of rotation for the roll 57. Because of the interconnection of the three rolls discussed above, the movement of the adjacent portions at the hemming station is all in the same direction.

Each of the gears 126 meshes with an associated gear 131 which powers the roll 41 on a first forming station. Because of the clockwise rotation of the gears 126, each of the gears 131 rotates in an anticlockwise direction with respect to the winding head frame assembly 111. The gears 131 are connected through a shaft 132 to the drive roll 40 of the associated first forming station. This produces rotation of the drive rolls 40 in the correct direction with respect to the head. The drive shaft 132 is also provided with a smaller diameter gear 133 which also rotates in an anticlockwise direction and meshes with an idler gear 134 causing it to rotate in a clockwise direction at a velocity substantially slower than the velocity of the shaft 132 due to the difference in diameter of the two gears. The gear 134 meshes with a ring gear 136 which is mounted on the stock support table 14 to cause rotation of the stock support table 14 in a clockwise direction with respect to the winding head frame assembly 11 1.

Preferably, the two first forming stations 26 are both provided with a gear 133 even though only one gear 134 is provided. With this arrangement the structure of the elements of the first forming stations are identical and interchangeable. Further, such an arrangement improves dynamic balance of the machine. The only nonsymmetry in the winding head is the single gear 134 which is not duplicated on the opposite side of the winding head. However, a weight 135 of identical mass is located opposite the gear 134 in the same physical location with respect to the central axis so complete dynamic balancing of the machine is achieved. Such dynamic balancing is, of course, important since the winding head rotates with a relatively high velocity and imbalance would cause extreme loads on the various bearing support systems.

Because the various gear elements are arranged so that proper rotational direction is obtained without need of idler gears or the like to reverse directions, a very simple gear train is provided even though the winding head is arranged to simultaneously process two strips of foil. The center gear 108 because of its central location, can be used to drive both of the gears 126. Similarly, the gears 126 for each of the hemming stations are used to drive the gears 131 associated with the two first forming stations. The size of the gears are selective with respect to the size of the various rollers so that the strips are tensioned as they pass from one operation to the next and are actually stretched slightly at the time they are wrapped around the tube 12. Consequently, the internal stress in each strip insures that each of the strips tightly adheres to the tube and a good heat exchange contact is provided. When the foil strips are formed of the same material as the tube these strips are directly wound onto the tube. However, when the tubing and the foil are formed of two difi'erent materials, such as aluminum and a ferrous metal, it is preferable to coat the tubing with a dielectric adhesive layer at 130 to prevent galvanic action between the two dissimilar metals. Such dielectric material is pumped into the tube and coats the tube 12 as it passes therethrough. Such a layer is not required, however, for its adhesive function, although it tends to provide a bond between the tube and the foil strips.

Reference should not be made to FIGS. 8 through 11 which progressively illustrate the manner in which the stock of interleaved strips of material is fed into the winding head. in FIG. 8 a coil of stock 141 is illustrated on the stock support table 14 in a position around the winding head 10 and coaxial with the central axis 11. This coil of stock consists of the two

strips

16 and 17 wound in an interleaved double spiral. The strip 16 is illustrated in solid line and the strip 17 in dotted line for purposes of illustration. The strip 16 is threaded into the winding head 10 around the roller 18 and enters the head at 142. The strip 17 however extends around the winding head over its associated roller 18 and enters the winding head at 143, a location diametrically spaced from the location 142.

Initially, the coil stock is spaced from the winding head 10 and has a thickness indicated at A. As the machine commences to wrap the tubing, the coil of stock 141 carried by the table 14 rotates in a clockwise direction at the same time the winding head rotates in a clockwise direction at a slower velocity. The two

strips

16 and 17 unwind from the inner diameter of the coil 141 at a faster rate than the stock feeds into the winding head. This causes some of the stock to build up around the winding head and form an inner coil at B where it is guided by the rollers 18 carried by the winding head. The buildup of an inner coil continues until approximately one-half of the stock has been removed from the inside of the coil 141. At this point in the cycle of operation illustrated in FIG. 10, the thickness of the inner coil B is at a maximum thickness.

Continued operation of the machine approaching the condition of FIG. 11 wherein the outer coil 141 is almost exhausted results in the decreasing thickness of the inner coil as illustrated in FIG. 11. Since the two strips are of substantially the same length, both strips are exhausted at about the same time. Of course, the inner of the two interleaved strips is shorter than the outer strip because it is wound on a spiral of smaller radius. However, the difference in length does not produce any problem since the manner in which the strips unwind from the outer coil and rewind on the inner coil accommodates the difference in length as illustrated by the progressive separation of the two strips extending from the outer coil to the inner coil. So long as the difference in length of the zone of interfacial contact between the two strips does not exceed the peripheral length of the outermost layer of such interfacial contact, the free portion of the outer strip 17 will not reach the free portion of the inner strip 16 and the two strips will feed properly. The manner in which the coils unwind and form an inner coil is described in more detail in my US. Pat. No. 3,134,166. The principal difference however, is that the two coils are not of the same length and it is necessary to accommodate this difference in length by arranging the mechanism so that the two strips can separate as they move from the outer supply or stock coil to the inner coil around the head.

With a machine in accordance with the present invention the lineal output of wound tube is doubled when compared to a prior single strip machine. The double wound tubing because of its greater helix angle tends to increase the turbulence of air flowing over the fins and thereby improves the heat exchange capacity of the tube. Further, the layer of the dielectric coating between the strips and tubes is more uniform since the lateral forces of the strips are balanced and the tube 12 is not pulled over against the guide 13. Further, the double helix winding of the tube increases the helix angle of the stress zones which the strips produce in the base tube. Consequently, the tube is not as susceptible to rupture when it is bent for installation in the associated equipment.

The illustrated embodiment of the machine obtains such increased output with a simplified gear drive system. The machine is also arranged so that it may be easily serviced. For example, the idler lancing rolls can be easily removed and replaced and the hemming assembly can be easily removed and replaced. Since the load on the bearing of the lancing rolls is the greatest load involved in the fonning operation, the central location of the lancing stations close to the central axis 11 reduces the load on the bearings by reducing the centrifugal force. Further, the two lancing operations are accomplished with only three lancing rolls. The use of hemming rolls located at right angles to each other further simplifies the structure of the machine and the drive of the various rolls.

Although preferred embodiments of this invention are illustrated, it is to be understood that various modifications and rearrangements of parts may be resorted to without departing from the scope of the invention disclosed and claimed herein.

What is claimed is:

l. A machine for winding strip material around a tube or the like comprising:

a winding head rotatable about an axially disposed passage therein,

means for advancing said tube at a governed rate through said axial passage,

a coil support around said winding head supporting and rotating a coil consisting of a plurality of long strips wound in interleaved spirals,

said winding head including feed means operable to separately and simultaneously feed said strips from the interior of said coil, fomiing means operable between said feed and winding means for forming each of said strips into a cross section having a base section and at least one leg section, and means to simultaneously wind the formed strips on the tube in a multiple helical form.

2. A machine as set forth in claim 1 wherein the rate said tube is advanced through said axial passage is at a rate timed with respect to the winding head rotation to wind said formed strips as a multiple helix in which the base sections of adjacent turns touch.

3. A machine as set forth in claim 2 wherein the forming means forms each of said strips into substantially U-shaped cross section having a base section and two spaced leg sections.

4. A machine as set forth in claim 3 including lancing means for separately and simultaneously lancing the edge portions of said strips fed from said coil,

and said forming means includes means for separately and simultaneously forming said lanced strips into said U-shape with said lanced portions forming said legs, and hemming means operable to separately and simultaneously form a hem on each of said leg sections adjacent said base section.

5. A machine as set forth in claim 1 wherein the means for feeding, forming and winding of each of said strips are generally located on opposite sides with respect to said axis of said winding head.

6. A machine for winding strip material around a tube or the like comprising:

a winding head rotatable about an axially and vertically disposed passage therein,

means for advancing said tube at a governed rate vertically through said axial passage,

a coil support around said winding head supporting and rotating a coil consisting of two strips wound in interleaved spirals,

feed means including a pair of lancing stations symmetrically positioned with respect to said central axis for separately lancing a strip,

a pair of first forming stations symmetrically positioned with respect to said central axis for initially {owning a lanced strip,

7. A machine as set forth in claim 6 wherein the rate said tube is advanced through said axial passage is at a rate timed with respect to the winding head rotation to wind said formed strips as multiple helix in which the base sections of adjacent turns touch.

8. A machine as set forth in claim 7 wherein the formed strips tangentially engage diametrically opposite sides of said tube during winding of said strips onto said tube.

I I ll l

Claims

1. A machine for winding strip material around a tube or the like comprising: a winding head rotatable about an axially disposed passage therein, means for advancing said tube at a governed rate through said axial passage, a coil support around said winding head supporting and rotating a coil consisting of a plurality of long strips wound in interleaved spirals, said winding head including feed means operable to separately and simultaneously feed said strips from the interior of said coil, forming means operable between said feed and winding means for forming each of said strips into a cross section having a base section and at least one leg section, and means to simultaneously wind the formed strips on the tube in a multiple helical form.

4. A machine as set forth in claim 3 including lancing means for separately and simultaneously lancing the edge portions of said strips fed from said coil, and said forming means includes means for separately and simultaneously forming said lanced strips into said U-shape with said lanced portions forming said legs, and hemming means operable to separately and simultaneously form a hem on each of said leg sections adjacent said base section.

6. A machine for winding strip material around a tube or the like comprising: a winding head rotatable about an axially and vertically disposed passage therein, means for advancing said tube at a governed rate vertically through said axial passage, a coil support around said winding head supporting and rotating a coil consisting of two strips wound in interleaved spirals, feed means including a pair of lancing stations symmetrically positioned with respect to said central axis for separately lancing a strip, a pair of first forming stations symmetrically positioned with respect to said central axis for initially forming a lanced strip, and a pair of second forming stations symmetrically positioned with respect to said central axis for further formings of each strip, said lancing stations being provided by a drive roll journalled for rotation around said central axis and two cooperating idler rolls journalled for rotation about axes on opposite sides of said central axis, each idler roll cooperating with said drive roll to provide a lancing station on opposite sides of said drive roll.