US3464101A - Method and apparatus for helically winding strip material - Google Patents

Description

Sept. 2, 1969 A. ZUBAL. ETAL 3,464,101

METHOD AND APPARATUS FOR HELICALLY WINDING STRIP MATERIAL Filed March 30, 1967 I5 sheets sheet l FIGZ FlGl

STOCK HEAD STOCK THEIR ATTORNEY.

Sept. 2,1969 A, UBAL ETAL 3,464,101

METHOD AND APPARATUS FOR HELICALLY WINDING STRIP MATERIAL Filed March 30, 1967 I 3 Sheets-Sheet 2 INVENTORS ANTHONY ZUBAL, HARRY F. DAVIS,

BY AM) M THEIR ATTORNEY.

Sept. 2, 1969 A. ZUBAL ETAL 3,464,101

rmaon AND APPARATUS FOR HELICALLY wmnms STRIP MATERIAL Filed March 30. 1967 3 Sheets-Sheet 5 FIG.7

INVENTORS'.

ANTHONY ZUBAL,

HARRY F. DAVIS,

B-Y Ki j THEIR ATTORNEY.

United States Patent 3,464,101 METHOD AND APPARATUS FOR HELICALLY WINDING STRIP MATERIAL Anthony Zubal, Latham, and Harry F. Davis, Amsterdam,

N.Y., assignors to General Electric Company, a corporation of New York Filed Mar. 30, 1967, Ser. No. 627,109 Int. Cl. B2ld 11/06 US. Cl. 29157.3 Claims ABSTRACT OF THE DISCLOSURE Gripping mechanism to force continuous thin metal strip through an arcuate path defined by a shoe. Resulting spiral of strip is continuously applied to the outer surface of a rotating-translating cylindrical tube.

Background of the invention This invention relates to a method and apparatus for helically winding a continuous thin metal strip, and mor particularly, to a method and apparatus for helically winding a continuous thin metal strip around the outer surface of a tube to form a heat exchanger element.

US. Patents 3,062,267 and 3,283,399, issued to Benjamin F. Hart and Roland P. Carlson, disclose a method and apparatus for helically winding strip material. In the apparatus shown in those patents, the strip material is motivated through the winding mechanism by the positive action of clutching members of the mechanism abutting against teeth extending from the strip material. In the patents there shown, the strip material is generally core iron and is wound in the form of a cylinder, the aforementioned teeth ultimately defining armature slots for the stators of dynamoelectric machines.

In the present invention, the strip material to be helically wound is continuous and uniform with no teeth extending therefrom. One effect of this is to create a need for a method of motivating the strip through the winding mechanism different from the prior art just discussed.

An additional feature of the present invention is that the helically wound strip is continuously applied around the outer surface of a cylindrical tubing which is continuously fed through the apparatus.

In the art of finned tubing manufacture, the process is typically performed by a rotating tube pulling around itself an edgewise disposed strip material. The strip is usually guided and set in place by one or more grooved rollers. An example of this can be seen in US. Patent No. 2,988,628Hall, particularly in FIGURES 3 and 4. This winding method gives rise to localized stresses in the strip material. These stresses can cause buckling at the inner diameter of the resulting fin and stretching or tearing at the outer diameter if the fin is too high. That is, the strip material must be kept below a certain limiting width if it is to be applied by this prior art method.

By means of the present invention, the strip material is gripped at many points uniformly and urged into a helical configuration around a tube. This method and means greatly reduces the localized stresses aforementioned and permits wider strips of a soft material such as copper to be wound around tubing to form higher and improved fins.

It is an object of the present invention to provide an improved method and apparatus for the edgewise continuous winding of strip material on a tubular workpiece.

Another object is to provide a clutching mechanism to motivate a strip material through a helical winding mechanism.

Other objects, advantages and features of the present invention will become apparent from the following de- Patented Sept. 2, 1969 ice scription when taken in connection with the accompanying drawing.

Summary of the invention Briefly, the method of the present invention is practiced by motivating a continuous strip material through an arcuate path about one of its edges and continuously applying the same to a rotating tube which is moving axially through the aperture of the arcuate path of th strip. The result is a continuous spiral application of strip to tubing. The apparatus of the present invention includes a headstock having an axial passage for tubing. A tailstock is operatively connected to the tubing and is movable in an axial direction pulling the rotating tubing through the headstock. A clutch member with drive pins indents and clutches strip material which is introduced transversely to the axis of the tubing. The strip material is forced into an arcuate path and applied edgewise to the rotating-translating tubing to form a helical finned heat exchanger tube.

Drawing In the drawing:

FIG. 1 is a schematic of the environment of the present invention,

FIG. 2 is a perspective view of the edgewise strip winding mechanism of the present invention,

FIG. 3 is an exploded view of the operating members shown in FIG. 2,

FIG. 4 is a sectional view of the driving head of the present invention,

FIG. 5 is a perspective view of a single drive pin used in the driving head,

FIG. 6 is a view taken along the line VIVI of FIG. 3,

FIG. 7 is a front view of the cam member, and

FIG. 8 is a front view of the face of driving member in association with a strip-workpiece.

Description Referring to FIG. 1, the environment of the present invention is shown schematically to include a machine bed 1, a head stock 3 and a movable tail stock 5. A tubular workpiece 10 is mounted rotatably and translatably by means such as tail stock 5 operatively mounted on bed 1.

Referring now to FIG. 2, a driving head, generally indicated at 2, is shown in operative relationship to a stationary mounting frame 4 which is part of head stock 3, an anvil or shoe 6, and a strip or workpiece 8. A tubular workpiece 10 is fed through frame 4 and driving head 2 with a uniform axial velocity imparted to it as by tail stock 5. Driving head 2, which is rotatable relative to frame 4 clutches strip workpiece 8, which is being fed transversely to tube workpiece 10, and pulls the strip 8 up around the rotating and translating tube 10 resulting in a continuous spiral of constant pitch of the strip 8 around and abutting the tube 10. The means by which strip 8 is clutched and motivated around tube 10 is the subject of the present invention and will now be described in greater detail.

Referring now to FIG. 3, an exploded view is shown of the driving head 2, frame 4, and anvil or shoe 6. Driving head 2 includes a shaft portion 12 with an enlarged head portion 14 mounted integral therewith. Both shaft portion and head portion are cylindrical having a cylindrical passage or aperture through their centers for the accommodation of tubular workpiece 10. Head portion 14 has a plurality of axially directed holes 16 passing therethrough and circumferentially spaced an equal distance from the axis of head 14. The abutment of shaft portion 12 to head portion 14 of the driving head 2 interferes with the clear passage of holes 16 (see FIG. 4) for a purpose to be described.

Referring now to FIG. 5, a single drive pin 18 is shown in perspective. Drive pin 18 has a pointed tip 20 on one end thereof, which tip is rectangular or elongated in cross section. On the opposite end of drive pin 18 from. tip 20, a shoulder is formed by the removal of material so that pin 18 extends through hole 16 and outward there from over the interfering abutting shaft member 12. Mounted in this fashion, it will be apparent that drive pin 18, while revolvable with head member 14, is nonrotatable relative to head member 14.

Referring again generally to FIGS. 3 and 4, stationary frame 4 is shown and is fixedly mounted on a machine tool bed 1. Frame 4 defines a cylindrical hole in which driving head 2 is mounted rotatably. An annular cam member 22 is fixedly mounted relative to frame 4. Cam 22 has an axially facing cam surface 24. Cam surface 24 is in direct contact 'with pin 18, though the drawing, for the sake of clarity, shows a slight clearance between the two members. In practice, there typically will be a ball thrust bearing between rotatable head member 14 and nonrotatable cam member 22. This too is left out of the drawing for the sake of clarity.

In FIG. 7, showing a front view of cam member 22, the cam surface 24 is shown as consisting of segments A and B. Segment A is slightly depressed relative to segment B. At point 26, the transition from the higher segment B to the lower segment A is shown and is approximately 90 in advance of transition 28 from segment A to segment B. The cam surface 24 at segment B is axially displaced relative to segment A by a dimension of the order of .004 inch.

Referring now to FIG. 6, the anvil or shoe member 6 is shown as it appears looking in the direction of movement of tube 10. Shoe 6 defines an aperture 30 which is coaxial with the aperture in driving head 2. Shoe 6 also has a guide or way 32 machined therefrom which extends from the edge of shoe 6 in a direction perpendicular to the axis of aperture 30 and tangential thereto. Guide 32 follows the aperture circumferentially around shoe member 6, for approximately 180. Shoe 6 also has a radially extending projection 34 which extends inward toward aperture 30. Projection 34 is substantially a wedge-shaped member in cross-section having a relatively pointed edge at its upper portion.

FIG. 8 shows a frontal view of the driving head 2 in its relation to the shoe 6 and the strip or workpiece 8 being fed thereto. Lines 260 and 28a are shown as phantom lines to correspond with transition lines 26 and 28 in FIG. 7 which represent the transition portions of cam surface 24.

The operation of this machine will now be described. Assume as a starting point the presence of a suitable heat exchanger tube 10 passing through the aperture 30 of driving head 2 and shoe 6, such a tube being operatively connected to a tail stock by which the tube is rotated and translated. Concurrently, a continuous strip material is fed into the guide 32 of shoe 6 in a direction generally perpendicular to the direction of movement of tube and tangential to the tube member itself.

As driving head 2, with its shaft 12 and head 14, retates relative to frame 4 and cam surface 24, drive pins 18 are actuated by the cam surface. As seen in FIGS. 6 and 8, when the head 14 rotates in a counterclockwise direction as shown, pins 18 are driven forward into the strip material 8 at a point corresponding to point 28 on the cam surface. When the pins 18 are in this forward position, they grip strip material 8 by the positive action of their tips 20. Rotating head 2 with tips 20 thus grip and pull the strip material 8 around a path defined by the guide 32 of shoe 6. Approximately 270 following point 28 on the cam surface, transition point 26, the cam surface recedes so as to permit pins 18 to recede into the holes 16. The pins 18 are so motivated to recede into their holes by the inclined planar surface of projection 34. The pins are thus in a retracted position between points 26 and 28 (on the cam surface) during the rotation of the head 14. As each pin again passes point 28, it is forced forward to repeat the gripping action on strip material 8. As pins 18 release the strip material 8 at point 26, the strip material emerges from shoe 6 on the downstream side of projection 34.

The pins 18 move forward only about .004 so as to clutch, but not puncture, strip 8. Furthermore, pins 8 are nonrotatable relative to head 14 so that the broad side of tips 20 are always doing the clutching. This, of course, provides stronger clutching action.

Since tube member 10 is constantly moving forward and rotating by means of the tail stock 5, it will be seen that the continuously winding strip 8 is wound edgewise around and abutting the tube in a helical configuration relative thereto. The tail stock motor applying torque to the tube 10 keeps the strip material 8 taut around the tube. The strip material 8 which is thus helically wound edgewise around strip of tube 10 may then be pulled through a straightening fixture to straighten out the material if necessary. The strip is then brazed or welded to the tube. These latter processes are not material to the present invention.

The present invention enables the strip material 8 to be wound around tube 10 on its edge without the benefit or without the necessity of a preformed foot or flange on strip 8. The effect of this is a greater overall diameter of tube 10 and strip 8 than could be obtained if strip 8 were required to be bent into a flanged configuration.

It will be apparent that the invention herein described provides an improved method and apparatus for the edgewise helical winding of strip material around tubing for the production of heat exchanger tubes.

It may occur to others of ordinary skill in the art to make modifications of the present invention which will remain within the concept and scope thereof and not constitute a departure therefrom. Accordingly, it is intended that the invention be not limited by the details in which it has been described but that it encompass all within the purview of the following claims.

What is claimed is:

1. A mechanism for winding continuous strip material in helical disposition around a tube, said mechanism comprising:

means to impart rotational and translational motions to a tubular workpiece,

means to introduce said strip material in a direction substantially normal to the direction of translation of said tubular workpiece and substantially tangential to said tubular workpiece, and

means external to said tubular workpiece to motivate said strip material around a helical path to continuously surround and edgewise abut said tubular workpiece,

said last named means including a revolvable circumferential array of axially movable drive pins having pointed tops arranged so as to indent and clutch said strip material on one surface thereof and cam means to actuate said drive pins into and out of their gripping position.

2. A mechanism for winding continuous strip material edgewise in helical disposition around a tube, said mechanism comprising:

means to impart rotational and translational motions to a tubular workpiece,

a driving head defining an axial aperture for the passage therethrough of said tubular workpiece,

said driving head rotatably mounted relative to a fixed cam member on one end thereof and to a fixed shoe member on the opposite end thereof,

said shoe member defining a circular helical guide path around said aperture,

said driving head defining circumferentially spaced coaxial holes in which are supported axially slidable drive pins having pointed tips,

said pins disposed in abutting relation to said cam member and being longer than said holes,

rotation of said driving head relative to said cam and said shoe imparting a reciprocating motion to said drive pins so that when said strip material is introduced to said guide path, said pointed tips of the clutching said strip material concurrently at a pludrive pins indent and clutch said strip on one surrality of surface locations.

face thereof and continuously motivate the same through said guide path around and in edgewise abutting relation to said tubular workpiece. 10 3. A winding mechanism as defined in claim 2 in which said drive pins are forced by said cam member into their References Cited UNITED STATES PATENTS c 2,374,144 4/1945 Stikeleather 29-1573 positions during approxlmately 270 of their 2,398,172 4/1946 gg 72 701 X 2 604 138 7/1952 Harrison 29-157 3 X 4. A Wmdlng mechamsm as defined in claim 2 in which 15 3062267 11/1962 H t l 72 172 said reciprocating motion has an amplitude of under .010". 3152629 10/1964 g zg ;6 X 5. A method for hellcally winding thin strip material 3,206,964 9/1965 Hart et a1 29 605 X of uniform cross-section around the outer surface of a tube, said method comprising the steps of:

concurrently rotating and translating a tubular work- 2 piece through a fin winding mechanism, said fin winding mechanism including a plurality of gripping members having pointed tips, introducing said strip material to said fin winding mechanism in a direction substantially normal to the 0 JOHN F. CAMPBELL, Primary Examiner D. C. REILEY, Assistant Examiner U.S. Cl. X.R.

Images