US2227820A - Process of forming a bellmouth on a metal tube - Google Patents

Description

Jan. 7, 1941. O B Z I 2,227,820

PROCESS OF FORMING A BELLMOUTH ON A METAL TUBE Filed June 5, 1937 INVENTOR 'ATTORNEY Patented Jan. 7, 1941 UNITED STATES PATENT OFFICE PROCESS or FORMING A BELLMOUTH ON A METALTUBE Application June 5, 1937, Serial No. 146,584

Claims.

The present invention relates to a novel process of flaring an end of a metallic tube and increasing the strength of the flared portion by thickening the wall section of the same.

5 The invention is particularly useful in preparing tubing for standard union couplings of the type having opposed conical gripping surfaces, and to this end the invention has for an object to provide a flared end having smooth conoidal inner and outer surfaces adapted to serve as seats for such gripping surfaces.

My process is particularly adapted for flaring of steel tubing such as is used for fuel lines of motor driven vehicles. However, the invention is not limited to such tubing but may also be applied to tubing of other metal and for other purposes.

Heretofore, it has been the practice to flare the ends of steel tubing without increasing the thickness of the metal of the flared portions. The metal is apt to'be reduced in thickness and be rendered brittle by the ordinary flaring processes, so that cracks are apt to develop at the flared ends particularly if the tubing is subjected to constant vibration in service.

I am aware that steel tubes have been flared and the flared ends folded inwardly to form a double layered bell at the end of the tubing, but such folding of the metal merely provides an enlarged body to be gripped by the union coupling without increasing the strength of the tubing at the neck of the flare where the fracture is most apt to occur.

It is an object of my invention to provide a process of flaring and thickening the wall of the flared portion without folding the metal upon itself, and to produce an increase in the crosssection of the metal at the flared end which extends from and includes the neck of the flare.

Other objects and advantages of my invention will appear in the following description of my preferred process and preferred means for carrying out the same and thereafter the novelty and scope of my invention will be pointed out in the claims. I

In the accompanying drawing;

partly diagrammatic showing means for performing the flrststage of my process; 5 Fig. 2 is a view largely in longitudinal section of the end of a tube as it appears after having been subjected to said first stage of the process;

Fig. 3 is a view in longitudinal section of certain apparatus employed in performing the sec- 55 0nd and final stage of the process; and

Fig. 4 is a view in longitudinal section of a standard union fitting applied to the finished tube.

In my flanging process I prefer to perform the first stage of the process with the metal heated and the second stage with the metal cold, although, as will be explained hereinafter, the entire process can be performed in a single operation with the metal hot.

In Fig. 1, I show a piece of tubing III under- 10 going the first stage of the process. The tube is gripped by a pair of opposed electrodes II and I2, each of which is provided with a semicircular socket I3 so that when the two electrodes are in gripping position they will completely en- 15 circle the tube. These electrodes are preferably made of copper or other material which is a good conductor of electricity and heat.

Immediately adjacent to the electrodes is a die of harder metal, preferably steel, which com- 20 prises a pair of jaws I4 and I5 each formed with a diametric half of a bell shaped socket I6 so as to completely encircle the tube when the jaws are in closed position. The jaws I4 and I5 may be directly connected to the electrodes 25 II and I2 respectively, so that they will be closed simultaneously therewith. When the die jaws are closed they grip the tube III at the inner end I1 of the socket. The latter is formed with an enlarged cylindrical portion I8 at its 30 outer end and with an intermediate conoidal surface I9 which is transversely curved at one end to merge into the gripping portion I1 and at the other end to merge into the cylindrical surface I8. 35

Another electrode 20 is provided which has a conical end 2| adapted to enter the end of the tube I0, and, cut in the conical face of the electrode, is an annular step forming a shoulder 22 adapted to engage the inneredge of the end 40 of the tubing III, as shown in Fig. 1. Obviously, the conical portion of the electrode 20 need not necessarily be carried to a point, but may be truncated if so desired.

Current is supplied to the electrodes from a 45 I g transformer comprising a primary coil 24 and a Figure 1 is a view in longitudinal section and secondary coil 25. Oneend of thesecondary coil is connected by a line 26 to the electrodes II and I2, while the other end of the coil is' connected by a line 21 'to-the electrode 20. The transformer is energized from a suitable source of alternating electric'current under control of a switch indicated at 28. Y

In operation, the tubing I0 is gripped by the electrodes II and I2 and by the die jaws and the point of electrode 20 is inserted into the end of the tube so as to seat the inner end edge thereof against the shoulder 22. Current is now supplied to the electrodes and flows through the tubing in, heating that portion of the tubing which lies between the step 22 and the electrodes 1 I and i2. The tubing is thus softened by the heat developed therein. Pressure is then applied to cause relative approach of electrode 20 to electrodes l l and I2, with the result that the heated portion is bent substantially to the form shown in Fig. 2. In other words, it bulges outwardly between shoulder 22 and the point where it is gripped by the die jaws. The tube will be hotter intermediate its points of contact with the electrodes because of the high thermal conductivity of said electrodes which chill the metal at said points, so that the tube will be bulged between said points and forced into contact with the conoidal surface I! of the die. The outer extremity of the tubing is thereby turned inwardly by reason of its engagement with the shoulder 22 and the end face 29 of the tubing is given a conical form by the conical face of the electrode 20.

In the first stage of the process it will be observed that the thickness of the tube wall is increased toward the end due to the compressive forces exerted. As shown in Fig. 2, the neck of the flared portion of the tubing is formed exteriorly in longitudinal section on the radius A while the inner surface of the tubing is curved on a radius B which exceeds the radius A by an amount considerably greater than the normal thickness of the tube wall. It will be noted also that the thickening of the tube wall starts from the very neck of the flared portion.

It is desirable to further thicken the end of the tubing so as to extend the surface 29 and this may be done by continuing the inward pressure of the electrode 20 until the tubing assumes the form shown in Fig. 3. However, I have found that better results have been obtained by performing this stage of the process with other apparatus while the tubing is cold. By so doing, I am able to obtain smoother inner and outer surfaces to be gripped by the union couplings. The second stage of the operation is shown in Fig. 3. The bulged end of the tubing as formed by the first stage, is gripped in a steel die consisting of opposed jaws 32 and 33 which completely encircle the tubing. This die is provided with a socket very similar in form to the socket [6 shown in Fig. 1, having a conoidal surface 24 adapted to give the outer side of the flared end a smooth seating surface 35 for the union coupling. A punch 36 formed with a frusto-conical end 31 is introduced into the end of the tubing. This tubing in its original bulged form is shown in dot and dash lines. As the punch 26 is forced inwardly with respect to the die 32 and 33 a thrust is developed substantially normal to the face 29, and the metal is compressed until it forms a thickened head 32 with an extended conical seat 2911 substantially parallel to the conical seat 25.

Fig. 4 illustrates the tubing with a standard union coupling connected thereto. This coupling consists of a tubular member 40 of substantially the same bore as the main body of the tubing, such member being formed with a threaded socket ll into which a nipple 42 is screwed. At the inner end of the socket there is a protruding annular lip 42 of conical form adapted to seat against the face 29a of the head 38. The nipple 'true seat with the conical tool 36.

42 is provided at its inner end with a conical seat 44 adapted to fit against the conical surface 35 of the flared end of the tubing. The nipple 42 is screwed into the socket ll until the head 38 is firmly gripped therebetween. It will be observed that the gripping surfaces bear against a thickened portion of the tubing III which is not formed by folding the metal back upon itself but by plastically deforming the metal to increase its integral thickness. With the tubing thus formed there is no tendency for cracks or fractures to develop because the tubing is actually stronger at its flared end than elsewhere and this increase of strength includes the neck of the flare as well.

It is of utmost importance that the conical seat 29a be true, since it is intended to fit the conical face of lip 43 accurately so as to form a fluidtight joint therewith. It will be noted that unlike structures in the prior art which form a conical seat on a side surface of the tube, my process forms a conical seat on an end surface of the tube. The end surface is formed initially by severing the tube from a length of tubing and in the ordinary commercial practice this surface is true enough to start with to insure the formation of a However, were the seat formed on a side surface of the tube initial irregularities in said surface might not be ironed out by the forming tools. For instance, in a tube having a seam forming either a ridge or a hollow on the inside or the outside or both, such irregularity might leave a trace in the conical seat which could be eliminated only by a separate finishing process. With my process irregularities of the inner or outer surfaces of the tube do not in any way affect the final conical seat because this seat is formed on an end surface which is substantially true to start with. Thus, my process may be applied to seamed as well as seamless tubing without resorting to a separate finishing or truing operation.

Having thus described my invention what I claim as new and desire to protect by Letters Patent is as follows:

l. The method of forming an outwardly flaring conoidal seat interiorly on the end of a tube which consists in seizing the tube and restraining radial expansion thereof at a point spaced from the end of the tube to provide suflicient tube material for the formation of a bulge adjacent the end of the tube, in heating and softening the tube adjacent its end leaving the end of the tube relatively cool and hard, and in applying pressure normal to and only on the inner circumferential section of the end face of the tube to cause the wall of the tube adjacent the end of the tube to bulge outwardly and the end face to turn inwardly.

2. The'method of forming an outwardly flaring conoidal seat interiorly on the end of a tube which consists in seizing the tube and restraining radial expansion thereof at a point spaced from the end of the tube to provide sufficient tube material for the formation of a bulge adjacent the end of the tube, in heating and softening the tube adjacent its end leaving the end of the tube relatively cool and hard, and in applying pressure normal to and only on the inner circumferential section of the end face of the tube to cause the wall of the tube adjacent the end of the tube to bulge outwardly andthe end face to turn inwardly against a conoidal die.

3. The method of forming an outwardly flaring conoidal seat interiorly on the end of a tube which consists in seizing the tube and restraining radial expansion thereof at a point spaced from the end of the tube to provide suflicient tube material for the formation of a bulge adjacent the end of the tube, in heating and softening the tube adjacent its end leaving the end of the tube relatively cool and hard, in applying pressure normal to and only on the inner circumferential section of the end face of the tube to cause the wall of the tube adjacent the end of the tube to bulge outwardly and the end face to turn inwardly against a conoidal die, and in pressing a conoidal die against said inturned end face to thicken the wall of the bulged portion of said tube.

4. The method of forming an outwardly flaring conoidal seat interiorly on the end of a tube which consists in seizing the tube and restraining radial expansion thereof at a point spaced from the end of the tube to provide suflicinet tube material for the formation of a bulge adjacent the end of the tube, in heating and softening the tube adjacent its end leaving the end of the tube relatively cool and hard, in applying pressure normal to and only on the inner circumferential section of the end face of the tube to cause the wall of I the tube adjacent the end of the tube to bulge outwardly and the end face to turn inwardly, and in limiting the radial dimension of said bulged portion by expanding said bulged portion against a cylindrical die surface.

5. The method of forming an outwardly flaring conoidal seat interiorly on the end of a tube which consists in seizing the tube and restraining radial expansion thereof at a point spaced from the end of the tube to provide sufficient tube material for the formation of a bulge adjacent the end of the tube, in heating and softening the tube adjacent its end leaving the end of the tube relatively cool and hard, in applying pressure normal to and only on the inner circumferential section of the end face of the tube to cause the wall of the tube adjacent the end of the tube to bulge outwardly and the end face to turn inwardly, and in shaping the side of the bulged portion adjacent the point at which the tube is seized by expanding the same against a conoidal die OTTO J. BRATZ.

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