Process For Cold Forming A Metal Tube With An Inwardly Thickened End

Abstract

Placing a short tubular metal blank into an open die, having an inner, annular extrusion shoulder, and partially pressing the blank through the shoulder to extrude an elongated, uniform wall thickness tube portion. Then placing a second blank into the die in end to end contact with the remaining portion of the first blank, and pressing the second blank similarly part way through the die extrusion shoulder to simultaneously extrude the remaining portion of the first blank through the shoulder to form it with the same OD as its first extruded portion, but with a smaller ID, to form an inwardly thickened end portion on the extruded part, while also extruding the uniform wall thickness portion on the second blank, and then repeating the cycle.

Description

BACKGROUND OF INVENTION

The invention herein relates to a process for cold forming or extruding a metal tube having a thickened or inwardly flanged end. While the process herein may be used to form tubes for a variety of purposes, it is particularly adaptable in the manufacture of rear axles for trucks, such as is commonly called a "Salesbury axle." In such type axles, it is common to forge or machine or both, an elongated tube having an end portion of reduced outer and inner diameters and formed with steps or shoulders for connection to wheel bearings and the like. The main portion of the axle is formed as a relatively thin wall uniform diameter tube and the opposite end is formed with an inwardly directed flange or thickened portion. Such end is normally inserted into a socket formed on a housing, such as a truck differential housing.

The forming of such a type axle requires a number of forging steps and then a number of machining steps to provide the accurate sizes required and also proper surface finishings. Since the axle is made of one piece of metal, a number of compromises as to the type of metal selected and the proper heat treating, must be made to maximize the different strength and other characteristics required from the opposite ends of the axle.

Hence, the process herein is concerned with the manufacturing of part of such a type axle, namely, the body or barrel portion with the thickened end, wherein such an axle may be made in two parts rather than in one as is conventional, to thereby reduce manufacturing steps and costs and provide for a better product. Such process may also be used to produce metal parts which generally are uniformly tubular in shape with an inwardly extending flange or thickened portion at one end.

SUMMARY OF INVENTION

The invention herein contemplates forming a uniform cross-section tube with an inwardly directed flange or thickened portion at one end, starting with a short, tubular blank which is cold formed or extruded through a die in a press. The die, mounted upon a press bed, is formed with an open blank receiving portion, beneath which is an annular shoulder or extrusion throat with a smaller opening through which the blank may be extruded. The press ram is provided with a ram punch member for pressing the blank through the shoulder and its opening.

The process herein includes first pressing the blank partially through the extrusion shoulder so that a substantial portion of the blank is extruded into a uniform, relatively thin wall, tubular section, leaving an outwardly flanged remaining blank portion in the die blank receiving part. Then a new blank is placed into the die and it too is pressed downwardly through the shoulder or die opening. In so doing, the previous, partially pressed blank is pushed through the extrusion shoulder. As it goes through, its thickened outwardly directed flange portion cold flows inwardly to form an inwardly thickened or flanged portion.

Meanwhile, the new blank is partially extruded and takes the place of the preceding blank. Then the cycle is repeated by again adding a new blank, etc. Thus, each new blank acts as if it is part of the ram punch, making the contact with the preceding blank and consequently permitting much faster production as compared to a single blank by blank operation, but also reducing wear and breakage of the ram punch itself.

The ram punch may be provided with properly sized, smaller extension members which fit into the blank for sizing the inner diameters of the blank during the extrusion thereof. Hence, the finished product can be held to a very accurate tolerance with respect to its OD and ID, thereby eliminating machining and surface finishing steps which have been required in the past, in connection with forming such devices by forging or machining processes.

Where the finished product is to be used as a portion of the above mentioned Salesbury type axle, the axle portion containing the various stepped configurations and the like, may be separately made, as for example, by the process described in my prior U.S. Pat. No. 3,739,620, issued June 19, 1973 for a Process for Forming a Flared End Tubular Metal Part.

The two separate pieces, namely, the piece made by the invention of this application and the second piece may then be welded together such as by means of inserting the end of one into the other and spinning one piece relative to the other to generate sufficieint friction and heat for a good spin formed weld. In this way, a finished axle or similar device may be made, with the advantage that the two pieces may be separately made of separate types of metal and/or separately heat treated to thereby improve the desired strength and characteristics of each end portion of the finished part.

These and other objects and advantages of this invention will become apparent upon reading the following description, of which the attached drawings form a part.

DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view of a truck axle made in accordance with the invention herein.

FIG. 2 is a view similar to FIG. 1 but shows the two parts of the axle separated.

FIG. 3 illustrates in cross-section, the press apparatus for carrying out the process herein, with the ram opened and a blank ready for insertion into the die.

FIG. 4 schematically illustrates the position of the blank in the die with the ram moved downwardly.

FIGS. 5-8 show successive steps in the process.

DETAILED DESCRIPTION

FIGS. 1 and 2 illustrate a hollow, tubular axle 10, commonly referred to as a "Salesbury axle" and typically used as the rear axle of a light truck. Such axles typically are formed with a reduced or configured end portion 11 having various diametrical portions for receiving and engaging with wheel or bearing parts, and an elongated tubular central or barrel portion 12 having an inwardly flared or inwardly thickened end portion 13. Such axles have in the past been manufactured in one piece through a variety of forging and/or machining operations.

The process herein contemplates forming the axle in two separate pieces, namely, a first piece 15 which encompasses the reduced end portion 11, and a second piece 16 which includes the barrel portion 12 and the thickened portion 13. Thus, the two pieces are separately made with the piece 16 made in accordance with the process of this application and the piece 15 made by some other process. To asemble the two pieces to make a complete axle, their respective ends 17 and 18 may be abutted and welded together by a suitable conventional welding processes.

The process herein contemplates maing the piece 16, or similarly shaped pieces, from a metal blank 20 which is in the form of a short, tubular piece of metal, such as steel. As shown in FIG. 3, the manufacturing equipment includes a die 21 mounted upon a press bed 22 of a convention press. The die has an upwardly opening blank reciving chamber or portion 23, beneath which is an annular extrusion should 24 to provide a central extrusion opening or throat 25, beneath which is a relieved exit end opening 26. An opening 17 in the bed or in blocks built up upon the bed provides space for downward movement of the extrusion.

The die is aligned with a conventional press ram 30, which is schematically shown as the press itself forms no part of the invention herein. The ram includes a downwardly extending press ram punch 31 sized to fit into the die opening 23. The punch also includes a smaller diameter, downwardly extending sizing punch 32 and a second, even smaller diameter lower sizing punch 33.

With reference to FIGS. 3 through 8, the process herein includes the following steps: First, as shown in FIG. 3, a blank 20 is dropped into the die opening 23. The press ram 30 is then lowered, as shown in FIG. 4, so that the lower end of the ram punch 31 engages the upper end of the blank and the sizing punch 32 extends through the opening in the center of the blank. Next, as shown in FIG. 5, the ram is moved downwardly against the press bed, to extrude the blank partially through the extrusion shoulder and its opening 25, thereby extruding a relatively thin wall, uniform diameter wall thickness tube or barrel portion 12.

The downward movement of the ram is stopped before the blank is completely extruded through the shoulder so as to leave an enlargemenet or outwardly extending flange portion 35 within the die opening 23, this portion being the unextruded portion of the blank.

Next, the ram is retracted, i.e., lifted upwardly, and a new blank 20a, identical to the original blank 20 is dropped into the die opening 23, as seen in FIG. 6. The new blank is now in end to end contact with the upper end of the original blank 20, that is the remaining enlarged portion 35 thereof.

Thereafter, as shown in FIG. 7, the ram is again lowered to press the blank 20a downwardly into the die, which thereby presses the original blank through the die opening completely. In this step, the material which formed the remaining portion of the original blank, that is the enlargement 35, is forced inwardly, now being positioned in an inwardly directed enlargement, namely, the thickened portion 13 whose ID is sized by the sizing punch 33.

Meanwhile, the ram continues moving downwardly, as shown in FIG. 8, so that the second blank 20a is extruded, in the same way as was the first blank, and simultaneously pushes the completely extruded original piece downwardly and out of the die completely. The press continues downwardly until the second blank assumes the shape and position of the first blank as is illustrated in FIG. 5 and thereafter a new blank is inserted as shown in FIG. 6 and the cycle repeats.

Hence, as can be seen, each blank functions as a portion of the ram to push the preceding blank during the time it itself is being extruded. This permits rapid operation, as well as preserving the press equipment and die against much of the normal wear which would be encountered in a one-by-one blank pressing operation.

Essentially, the process herein is carried out with the metal being cold. Actually, it is preferable to heat the metal so as to warm it to a point below its metallurgical transition points to thus permit easier flow of the metal under pressure and thereby reduce the required ram pressure. Thus, by cold forming, it is meant that the blanks are either at room temperature or at relatively low temperatures, i.e., below transition points.

Although the figures illustrate the extrusion of a tube of circular outer and inner diameters, the shape in cross-section of the tube may be varied. In addition, it is possible in this process to form inner or outer surface configurations on the tube, such as longitudinally extending gear teeth, by suitably profiling either the shoulder throat or opening 25 or the surfaces of the sizing punches 32 and 33.

Claims

Having fully described an operative embodiment of this invention, I now claim:

1. A process for extruding a tubular metal part having an inwardly flared end portion, in a press, having a support base and a pressure ram movable towards said base, comprising:

positioning a relatively short tubular blank within a die mounted upon the base in alignment with the ram, the die having an open inlet end with a blank receiving portion and an outlet end having an inwardly extending annular shoulder whose inner cross-sectional dimension is smaller than that of the blank receiving portion to form an extrusion throat, and with the die being open at the outlet end for passing the extruded blank therethrough;

ram pushing the blank partway through the die shoulder for thereby extruding a portion of the blank therethrough to form a substantially uniform, relatively thin wall tubular barrel portion on the blank, with the end portion of the blank remaining in the die blank receiving portion thereby forming an outwardly flared, that is, thicker outwardly extending wall portion on the blank end;

next, inserting a second, identical blank into the die blank receiving portion in end to end contact with the first mentioned blank;

then ram pushing the second blank towards the die shoulder, thereby forcing the said end portion of the first mentioned blank completely through the die shoulder and out of the die outlet opening, to simultaneously force the thicker wall portion thereof to move radially inwardly, that is, causing the thicker wall portion to reverse and extend inwardly relative to the said barrel portion, so that the now finished extruded first blank is formed as an elongated tube of uniform external cross-section and with its inner cross-sectional shape having a portion which is of smaller cross-sectional size at an end of the tube, relative to the inner cross-sectional size of the remaining portion of the tube;

and then continuing the ram pushing of said second blank to repeat the steps of pushing the blank partway through the die shoulder and then repeating the cycles of inserting a new blank and ram pressing for thereby continually extruding such tubular parts.

2. A process as defined in claim 1, and including the step of accurately sizing the inner cross-sectional periphery of the tubular part by connecting upon the ram a pre-sized punch portion so that the ram punch portion is arranged within the blank opening and extends through the shoulder during the ram pushing of the blank through the shoulder for controlling and holding the inward movement of the metal material during its extrusion through the shoulder.

3. A process as defined in claim 2, and including the step of accurately sizing the inner smaller cross-sectional periphery, namely, that of the thickened end, by applying a second, smaller size punch portion upon the free end of the first mentioned punch and locating said second punch portion within the shoulder during the time that the ram pushes the second blank to correspondingly push the remaining first blank portion through the shoulder.