US1019485A - Butt-seamed metal tube and method of making the same. - Google Patents

Description

R. KOENIG. BUTT smmnn METAL TUBE AND METHOD OF MAKING THE SAME.

APPLICATION I'ILED JULY 27,1910.

l tentea Mar. 5, 1912.

" United States divided herefrom UNITED strATEs PATENT OFFICE.

ROBERT KOENIG, OF BROOKLYN, NEW YORK, ASSIGNOR TO PHENLX TUBE COMPANY, OF BROOKLYN, NEW YORK, A. CORPORATION OF NEW JERSEY.

.BUTT-SEAMED METAL TUBE ND METHOD or MAKING THE sAME.

To all whom it may concern.- I

Be it known that I, ROBERT KOENIG, a citizen of the United States, and resident of Brooklyn, in the co'untyof Kings and State of New York, have invented new and useful Improvements in Butt-Seamed Metal Tubes" and Methods of Making the Same, of which the following is a specification.

My invention relates to the construction of prismatic sheet metal tubes, and consists in a method of forming butt seamed tubes of sheet metal, and in the tube which is the product of-the said method.

The object which I have in view is to make prismatic metal tubing which,though simply formed with a butt seam, without welding or of shapes, until the two edges of the strip meet, when the residual elasticity of the metal suffices to spring the edges of the seam apart. By my invention the operation of rolling and drawing the tube produces in it such internal strains that the normal condition at the seam is one of mutual pressure between the meeting edges, so that the tube is and remains a closed tube.

T he essence of the method is the production' by rolling or drawing the metal, of longitudinally disposed narrow regions wherein the metal is in a condition of permanent internal strain, of which the resultant is a bending moment which tends to alter the periphery of the tube as a whole and therefore closes the seam tightly, and likewise, the characteristic which distinguishes my new product, is the presence in the structure of a butt-seamed, sheet metal tube, of such longitudinally disposed narrow regions of internal stress I The mechanism by which the method is performed and the structure produced, which mechanism forms the subject matter of an application for Letters Patent of the Serial No. 615,542, filed March 20, 1911, is characterized by an internal mandrel and external complementary die-members, which are all Specification of Letters Patent.

so proportioned and disposed as to have internal and external clearances at the places Patented Mar. 5, 1912. Application filed July 27, 1910. Serial No. 574,076.

where the'angles of the prismatic tube are formed, and to exert forming pressure on the sides of the prismatic tube so as to cause a flow of the metal of which the tube is composed, from each side outward toward the clearance-spaces wherein the angles of the tube are formed.

The structural condition presented by a butt-seamed, sheet metal tube having longitudinally disposed narrow regions of internal stress may be, and I believe is best, produced-by compressing the tube at intervals around its periphery, bet-ween the dies or rollers on the one hand, and an internal mandrel on the other, so that the metal flows slightly in both directions out of the compressed regions, each local flow meeting an oppositely directed flow proceeding from an adjoining region of compression. meeting place of these two opposed flows of metal thus becomes a region of internal strain which when the tube emerges from the restraint of ,the instruments which formed it, holds .the two edges of the seam tightly pressed together, producing an apparently seamless tube, instead of the openderstood from a description of the method of forming a square tube, of the instruments used to carry out the method, and of the structure of the tube itself.

A concrete example of .my invention is illustrated in'the drawings hereto annexed, in which Figures 1 to 1 represent diagrammatically three preliminary stages of the manufacture of a prismatic tube out of fiat sheet metal; Fig. 2 represents, partly in cross section, onalarger scale, the instrmnents for fornnn a s uaretube and the tube therein b 7 7 I projection or bur indicated at 6 along the cut edges on one side of the strip. For purposes presently to be explained, I so place the strip of metal in the bending machine that when the cylindrical tube is formed, the burs lie on the outside. The formation of the cylindrical tube involves a rolling and drawing in any of the well known machines 'suited to the purpose, which first shapes the tube in channel form having a rounded U section as indicated in Fig. 1 and then further rolls and draws the metal so that the cylindrical tube shown in cross section in Fig. 1 is the result. The mandrel and die which give the final cylindrical shape to the metal bring the two edges of the strip close together, but then the residual elasticity of the metal causes the two edges of the seam to spring apart slightly leaving a gap such as shown at g in Fig. 1. The cylindrical, open-seam tube is then placed in the machine which is to convert it into a prismatic tube with a closed butt seam.

For purposes of illustration, I take the case of a square tube to be made from the round tube above described. A drawbench machine such as used for squaring seamless drawn tubing, will serve my purpose, with changes in the mandrel and roller dies, as hereinbelow described. The tools or instruments in the machine for forming the square tube which immediately perform the work, consist of an internal mandrel marked M in Fig. 2 and a roller die or former composed of four external rolls R which are op posed to the sides of the mandrel. This mandrel is held in position by a rod M which is laid in the cylindrical tube of metal and is anchored outside the end of the tube to a convenient portion of the frame of the drawing machine. The forward-end of the tube is gripped by the traveling jaws of the drawing machine in the usual manner. The arrangement of four 'rolls which constitute the external former or die is in general the same as that shown in Figs. 1 and 2 of Carrs United States Patent No;.402,140, and the positional relationship of the mandrel and sheet metal tube to each other and to the rolls is much the same as that shown in Fig. 1 of Ostranders United States Patent No. 113,332.

The mandrel M and rolls R operate upon all portions of themetal tube except at and near thecorners of the prism which is formed by the rolling and drawing operation. Thus the edges of the rolls R as shown in Fig. 2 are well inside of the salient angles of the square tube and the edges of the mandrel M are chamfered OK at the corners at m, so that the active pressure and drawing friction is exerted on the inside by the sides m of the mandrel M and on the outside by the rolls R.

The provision of clearance between the operating instruments at the corners thereof or rather at the places where the salient angles or edges of the tube are formed, together with the heavy pressure brought to bear between the mandrel and the rolls bends and compresses the metal of which the round tube was formed and which is being squared in the machine, at the sides of the squared tube and this causes a flow of the metal of which the tube is composed from the sides toward the angles, the direction of this flow being indicated by the'arrows in Fig. 2. Therefore at each corner C of the square tube the flow of metal coming from two directions produces a region which is set in compression at each salient angle of the tube; these compression regions are indicated conventionally by heavy shading at the points C in Fig. 2.

The dimensions of the mandrel M and rolls R are properly adapted to the peripheral dimensions of the round tube shown in section at Fig. 1, so that in forming the prismatic tube the edges of the gap' 9 are brought together. But when the prismatic tube has been formed as above described, the presence at the salient angles of the tube of regions in which the metal of which the tube is formed is under internal compressive strain produces a resultant of contractile effort as contrasted with the residual expansive elasticity manifest in the round tube shown in Fig. 1 and the edges of the seam at g' are held in close mutual abutment. As the burs b were left at the outside of the tube, these are rolled into the seam 9 so as to fill the slight irregularities due to imperfect cutting of the strip in the first place.

Butt-seamed prismatic tubes formed as above described present to the eye the appearance of seamless drawn tubes and are amply strong for many light structural purposes, such as the manufacture of metal bedsteads or other furniture, and by reason of the simplicity of their method of manufacture, can be made more rapidlyand cheaply .What I claim andde sire to secure by .Let- 't"'t'S Patent is:

1. The method, of makin buttseamed tubes, which consists in hen ing a sheet of s metal into tubular form and then producing in the sheet a permanent peripherally con-- tractile internal strain.

-2. The method of making butt-seamed tubes, which consists in bending 5; metal *aeet into prismatic tubular. form and'pro nucing in the metal of the sheet at the salient angles 'of the prism a permanent, internal, compressive strain. t

3. The method of making butt-seamed 15 prismatic metal tubes,- which consists in bend sing a strip of metal intothe desired tubular form, and compressing the metal at the sides of the rismcausing internal flow toward the salient angles sufiicient to produce at said angles a condition of permanent internal compressive strain.

4. A tube consisting of a sheet of metal bent in prismatic form with edges in one of the faces of the prism abutting under mu tual pressure.

5. A tube consisting of a bent sheet of metal in prismatic form with abutting edges on one of the faces of the prism, thematerial of which the sheet is composed being under permanent internal compressive strain atthe salient angles of the rism.

Signed by me at Broo yn Kings Co. New York this 20th day of July 1910. 4

ROBERT KOENIG.

Witnesses:

A. P, ALVORD, CHAS. A. FoLLn'r'r.

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