Abstract:
In the present invention a tubular blank and an article such as a bushing to be assembled are loaded into a die. The tube is hydroformed using typical methods and, while the blank is still pressurized, a punch pierces a hole in the tube. The punch also has an article loaded onto it and, as the punch advances, the article is pushed into the tube through the pierced hole. The punch continues to advance such that it pierces a hole in the opposite side of the tube. The punch then retracts leaving the bushing in the tube. The article may alternately be inserted by means separate from the punch.

Description:
FIELD OF THE INVENTION 
     This invention relates to hydroforming a tube and, more particularly, to a forming such a tube with an article inserted therein. 
     BACKGROUND OF THE INVENTION 
     Hydroforming is well known for its ability to form an integral hollow beam with a complex shape, something which would otherwise have to be fabricated from several pieces and/or bent to shape. Typically, a round tubular blank is inserted between a pair of dies which have an internal cavity in the form of the desired exterior shape of the final part. Then the ends of the tube are plugged and the interior chamber of the tubular blank is pressurized, generally with water or hydraulic fluid, to force it into the shape of the die cavity. The completed part is then de-pressurized and removed. 
     The hydroformed part often, in its final application, will require that one or more holes or openings to be provided in it, a task which is sometimes accomplished by cutting or drilling after the tube is formed. It is also known, however, to pierce or cut the holes while the tube is still pressurized and held in the die or mold. For example, U.S. Pat. No. 4,989,482 to Mason discloses punching the wall of an internally pressurized tube. Similarly, U.S. Pat. No. 5,666,840 to Shah et al. discloses piercing two aligned holes in a hydroformed tube. 
     Once the holes are punched, functional elements such as bushings or threaded nuts often must be inserted to permit, say, a fastener to attach to the hydroformed part. Other articles may be required to be inserted. In all cases, however, once the hole(s) have been pierced (or cut, etc.), after the part is removed from the die cartridge, the bushing, etc. is inserted and then welded to the hydroformed part. While other methods of attachment are known, each method requires a separate operation after the part is hydroformed and the hole is cut. Not only do such additional cutting, fitting and welding steps add process cost and time, but also have a tendency to introduce errors such as additional dimensional variation or missed process steps, both of which can be detrimental to the function and economics of the part. 
     Accordingly, there is a need for an improved method and apparatus for inserting articles into hydroformed tubes which can decrease process cost and time, as well as increase the accuracy and repeatability with which mass manufactured parts are fabricated. 
     SUMMARY OF THE INVENTION 
     In a first aspect, the present invention provides 1.A method for hydroforming a tubular member comprising the steps of providing a die having a cavity therein, the cavity having an internal surface corresponding to a configuration of a desired final tubular member, providing a tubular blank; the tubular blank having an internal chamber, confining the tubular blank in the cavity, sealing the internal chamber, pressurizing the internal chamber to cause the blank to conform to the internal surface of the cavity to create the tubular member having a wall, making a hole in the wall of the tubular member while the tubular member is in the die; and inserting an article into the hole while the tubular member is in the die. 
     In a second aspect, the present invention provides an improved method of hydroforming a tube, the method having the steps of providing a die having a cavity therein, providing a blank having an internal chamber, confining the blank in the cavity, sealing the chamber and pressurizing the chamber to create a hydroformed tube, the tube having a wall, an improvement comprising the steps of, making a hole in the wall while the tube is confined in the die, and inserting an article at least partially into the hole while the tube is confined in the die. 
     In a third aspect, the present invention provides an apparatus for hydroforming a tubular member comprising a die having a cavity therein for confining a tubular member, pressurizing means for internally pressurizing the tubular member to a desired pressure, a hole-making member for making a hole in a wall of the tubular member and an article insertion member for inserting an article at least partially into the hole wherein the hole-making member is disposed in a passageway in the die, the passageway communicating with the cavity to provide the hole-making member access to the wall of a tubular member confined in the cavity, and wherein the article insertion member is disposed in a passageway in the die, the passageway communicating with the cavity to provide the article insertion member access to a hole in the tubular member while the tubular member is confined in the cavity. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a better understanding of the present invention, and to show more clearly how it may be carried into effect, reference will now be made by way of example to the accompanying drawings. The drawings show components made according to a preferred embodiment of the present invention, in which: 
     FIG. 1 is a sectional side view of a hydroforming die set according to the prior art; 
     FIG. 2 is a sectional side view of the apparatus of the present invention; 
     FIGS. 3-6 are sectional side views of the apparatus of FIG. 2, shown in various stages of its operation; 
     FIG. 7-9 are sectional side views of a part made according to the present invention; 
     FIG. 10 is an exploded isometric view of an automotive sub-frame made in accordance with the present invention; and 
     FIGS. 11-13 are enlarged side views of parts made in accordance with alternate embodiments of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Hydroforming forming presses and dies are well known in the art and thus it is necessary only to describe such equipment briefly here. Referring to FIG. 1, a hydroforming apparatus according to the prior art is shown at  10 . Apparatus  10  has a pair of die halves  12  which co-operate to form an interior cavity  14  for forming a tubular blank (not shown) into a tubular member  16  having an interior chamber  18  and a desired shape molding cavity  14 . Means for pressurizing the tubular blank during the process are also provided, but not shown in the Figure. 
     Referring to FIG. 2, a hydroforming apparatus according to the present invention is shown generally at  20  and has a first die half  22  and second die half  24  which co-operate to form an interior cavity  26  having an internal surface  27 . Apparatus  20  also has a first passage  28  and a second passage  30  disposed in an aligned fashion across cavity  26 . A die button  32  having a central hole is disposed at the intersection of second passage  30  and cavity  26 . A punch apparatus  34  has a hydraulic or pneumatic cylinder  36  for controllably reciprocatingly actuating a hole forming apparatus, such as a punch  38 , in passages  28  and  30 . Punch  38  (shown in FIG. 2 in a ‘withdrawn’ position) is capable of forming a hole or holes in a tube or tubular member  40 , having an interior chamber  41 , and which is retained in cavity  26 , as will be described further below. Means for sealing and controllably pressurizing a tubular blank (not shown) from which tubular member  40  is formed are also provided, but not shown in these Figures. Punch  38  has a cutting tip  42 , a first shank  44  and a shoulder  46 . As one skilled will understand, cutting tip  42  and die button  32  are sized to cooperate with one another to provide a hole of desired configuration in tubular blank  40 . 
     A magazine  48  is provided for supplying a plurality of articles  50  to the apparatus for insertion into a tubular blank  40  held in cavity  26 . In this embodiment, article  50  comprises a collar  50  having a bore  52  therethrough. As shown in FIG. 3, first shank  44  is sized to permit punch  38  to be inserted into bore  52  of collar  50 . In this position, shoulder  46  bears against collar  50 . Shoulder  46  on punch  38  acts as an insertion member for the article in that, as the punch apparatus advances, shoulder  46  causes collar  50  to also advance toward, and ultimately be inserted into tubular member  40 , as will be described in more detail below. 
     Referring again to FIG. 2, in use a tubular blank (not shown) is pressurized (by sealing and pressuring its internal chamber) and is hydroformed according to known techniques to yield a tubular member  40 . Typically this process comprises placing a tubular blank (not shown) in cavity  26 , with die halves  22  and  24  open, closing die halves  22  and  24  and then internally pressurizing the blank to a desired pressure so as to cause the tubular blank to assume the shape of cavity  26  to thereby yield tubular member  40 . 
     Referring to FIG. 3, once tubular member  40  has been formed in cavity  26 , punch  38  is advanced by cylinder  36  through first passage  28  to insert punch  38  into bore  52  of collar  50  and advance punch  38  until collar  50  bears against shoulder  46 . Punch  38  is further advanced through first passage  28 , thereby also advancing collar  50  through passage  28 . 
     Referring to FIGS. 3-6, as punch  38  is progressively advanced, cutting tip  42  contacts the wall of tubular member  40  (FIG.  3 ), then cutting tip  42  pierces the wall of tubular member  40  to make a first hole  60  (FIG.  4 ), then collar  50  engages the edges of first hole  60  and widens first hole  60  by partially extruding the edges to create flanges  62  as collar  50  is inserted into first hole  60  (FIG.  5 ), and then cutting tip  42  contacts and pierces a second hole  64  in the wall of tubular member  40  (FIG.  6 ). A pair of slugs  66 , created by the punching of first hole  60  and second hole  64  is ejected through die button  32  and through second passage  30 . As shown in FIG. 6, punch  38  is advanced until collar  50  is preferably fully inserted into interior chamber  41  of tubular member  40 , such that the leading edge of collar  50  abuts the surface of the wall of tubular member  40 . Punch  38  is then returned to its withdrawn position (FIG. 2) and the die is opened to yield the part. 
     Referring to FIG. 7, a part  70  formed in accordance with the above invention has a tubular member  40  and collar  50  inserted therein. Holes  60  and  64  cooperate with bore  52  in collar  50  to offer a complete through-hole  72  through the part. As one skilled in the art will appreciate, flanges  62  tend to retain collar  50  by a press-fit within the part. Part  70  may be used in this state as a component in a further assembly, or more preferably is enhanced by a weld  74  (FIG. 8) between collar  50  and at least one side. The part  70  may then be fastened to another workpiece  76  (see FIG. 9) by means of a fastener  78 , such as a bolt and nut. 
     The present invention may be used in forming structural components of almost any description. Referring to FIG. 10, a portion of an automobile subframe assembly is shown at  80 , which comprises a tubular member  40  having a plurality of collars  50  for mounting subframe assembly  80  to the automotive body (not shown). Collars  50  are inserted at multiple locations subframe assembly  80  in accordance with the present invention. Preferably, a plurality of punch apparatuses  34  are provided on apparatus  20  for subframe  80 , one at each location a collar  50  is required. It is desirable to have all such punch apparatuses operate simultaneously, since once a first punch pierces the part, the internal pressure in the tube may be released. 
     While the above description constitutes the preferred embodiment, it will be appreciated that the present invention is susceptible to modification and change without departing from the fair meaning of the accompanying claims. 
     For example, apparatus  20  may be modified to fully insert collar  50  through first hole  60  and second hole  64 , as shown in FIG.  11 . Referring to FIG. 12, punch  38  and die button  32  can be modified to provide flangeless first and second holes  60 ,  64 . In this embodiment, it will be understood that a leading edge  82  of collar  50  acts, in effect, as cutting tip  42  in forming holes  60  and  64 . (In FIG. 12, collar  50  is shown both in a phantom position, prior to piercing and insertion, and in its fully inserted position). Referring to FIG. 13, only one hole  60  is formed and a different article, such as a threaded nut  50 , is inserted. Other articles may also be inserted, such as pierce nuts and bushings. Still other articles may be inserted, with generally cylindrical articles being preferred, but not required. 
     One skilled in the art will recognize that the holes  60  and  64  need not be formed by a punch but may be formed by other suitable means, such as drilling, laser cutting or other known means. 
     The present invention may be employed with any known hydroforming technique, and may be used equally with low-pressure and high-pressure hydroforming. It will be understood that the particular means of hydroforming tubular member  40  is not important to the present invention and, further, that the tubular member need not be formed at all in the cavity, but rather its initial shape may be maintained. Non-cylindrical blanks may also be used. 
     It will be understood that, while it is preferable to operatively associate the insertion of the article with the forming of the hole(s) in tube  40 , that the insertion of the article need not be so associated, and may be accomplished by other means. For example, means (not shown) may be provided in second passage  30  for inserting an article into one or more of holes  60  and  64  in tube  40 . 
     Still other modifications may be apparent to those skilled in the art but these are not intended to depart from the scope of the appended claims. It will be understood in the claims that the step of pressurizing the internal chamber of the blank may be performed either before or after the step of confining the blank in the die cavity.