Abstract:
A hydroforming assembly has a plurality of die structures that are mounted on a press for reciprocating movement between open and closed conditions. The die structures have cooperating die surfaces defining a die cavity when in the closed condition and receive a metallic tube blank when in the open conditions. A hydroforming fluid supply system has tube-end engaging structures that are movable to selectively and sealingly engage opposite ends of the tube blank. The hydroforming fluid supply system provides pressurized fluid into an interior of the tube blank in order to expand the tube blank outwardly into conformity with the die cavity. A punch extends within a passage of at least one of the die structures. The punch is movable between retracted and extended positions. A punch driving assembly drives the punch between the retracted and extended positions to punch a hole into the expanded tube blank. A flushing system communicates with the die cavity providing a flushing fluid flow through the interior of the expanded tube blank.

Description:
This application is the National Phase of International Application PCT/CA01/00164 filed Feb. 13, 2001 which designated the U.S. This application is also based on U.S. Provisional Application Ser. No. 60/183,783, filed on Feb. 22, 2000, the entire contents of which are hereby incorporated herein by reference thereto. 
    
    
     FIELD OF INVENTION 
     This invention relates to a system for flushing hydroformed parts to remove debris from inside the part. 
     BACKGROUND OF THE INVENTION 
     In recent years, hydroforming technologies have become more and more important in manufacturing, particularly in the automotive industry. In one application of hydroforming, a tubular metal blank (usually steel) is placed in a die cavity. The opposite ends of the tube are sealed by a pair of hydraulic rams having central ports through which extremely high pressure fluid is injected into the tube. The high pressure fluid expands the tube into conformity with the surfaces defining the cavity. As a result of this hydroforming process, high strength parts can be made into complex tubular shapes that could otherwise not be achieved in any practical economic fashion. Such hydroforming processes are disclosed in U.S. Pat. Nos. 4,567,743; 5,070,717; 5,107,693; 5,233,854; 5,239,852; 5,333,755; and 5,339,667. 
     In even more advanced forms of hydroforming, the hydraulic rams are forced inwardly toward one another to create metal flow within the tube as the tube is being expanded in order to maintain the wall thickness of the tube within a predetermined range throughout the expansion process. Such hydroforming processes are disclosed in U.S. Pat. Nos. 5,718,048; 5,855,394; 5,899,498; 5,979,201; and 5,987,950. 
     For certain applications, it is desirable to produce a finished part that has a plurality of holes therein that can be used to mount other components. For example, in the automotive industry it is known to hydroform a tubular blank in order to form an engine cradle assembly used to mount an automotive engine. The finished tubular part must be provided with holes to enable fasteners to pass therethrough for mounting engine mounting brackets and the like. To facilitate the provision of holes in the part, it is known to perform a hole piercing operation in the hydroforming die itself. Typically, a hole is punched through the tube while under pressure. In one method, the portion of the tube cut out by the punch (sometimes referred to as the “slug”) has an edge portion thereof left connected to the tube, depending into the tube. This is problematic because it adds unnecessary weight to the part, which is always a concern in the automotive industry. In another method, after the hole is formed, the punch is withdrawn out of the tube, and formed by the punch is maintained in engagement with the punch under the force of fluid pressure as the punch is withdrawn from the tube. The slug is then flushed by fluid to a scrap collector. One such typical operation is disclosed by U.S. Pat. No. 5,816,089. One problem associated with the aforementioned technique is that on occasion the slug does not exactly align with the hole it came from as it is withdrawn and may fall into the tube. It must then be retrieved by other means. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to a system for removing scrap from an interior of a hydroformed part. 
     Accordingly, the present invention provides a hydroforming assembly that has a plurality of die structures mounted on a press for reciprocating movement between open and closed conditions. The die structures have cooperating die surfaces defining a die cavity when in the closed condition and receive a metallic tube blank when in the open condition. A hydroforming fluid supply system has tube-end engaging structures that are movable to selectively and sealingly engage opposite ends of the tube blank. The hydroforming fluid supply system provides pressurized fluid into an interior of the tube blank in order to expand the tube blank outwardly into conformity with the die cavity. A punch extends within a passage of at least one of the die structures. The punch is movable between retracted and extended positions. A punch driving assembly drives the punch between the retracted and extended positions to punch a hole into the expanded tube blank. A flushing system communicates with the die cavity providing a flushing fluid flow through the interior of the tube blank. 
     According to another aspect of the invention, there is provided a method of forming a hole in a hydroformed metallic tube blank and removing a punched scrap therefrom. A plurality of die structures is provided on a press for reciprocating movement between open and closed conditions. The die structures have cooperating die surfaces defining a die cavity when in the closed condition. The die structures are provided in the open condition. A metallic tube blank is placed into the die cavity. The die structures are closed. An interior of the tube blank is pressurized with a fluid so as to expand the tube blank into conformity with the die cavity and thus form an expanded tube blank. A punch is forced through the expanded tube blank so as to punch a hole therein. The interior of the expanded tube blank is depressurized. Fluid is flowed through the expanded tube blank so as to flush a punched portion of expanded tube blank out from the interior thereof. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic cross sectional view of the hydroforming apparatus having an in-die hydropiercing, and slug disengaging system in accordance with the principles of the present invention, and showing a tubular metallic blank inserted into the hydroforming apparatus in preparation for hydroforming; 
     FIG. 2 is similar to FIG. 1, but shows the expanded metallic tube after hydroforming; 
     FIG. 3 is an enlarged partial view of the hydroforming apparatus shown in FIG. 2 providing a detailed view of a hydropiercing punch assembly with the punch in the retracted position; 
     FIG. 4 is similar to FIG. 2, but shows the punch in its extended position after punching a hole into the expanded metallic tube; 
     FIG. 5 is an enlarged partial view similar to FIG. 3, but showing the punch in an extended position after punching a hole into the expanded metallic tube; and, 
     FIG. 6 is similar to FIG. 4, but showing a punched slug being flushed out of the expanded metallic tube. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now more particularly to the drawings, there is shown therein in FIG. 1 a schematic cross-section view of a hydroforming apparatus generally indicated at  10 , which embodies the principles of the present invention. The hydroforming apparatus  10  includes a hydroforming press, generally indicated at  12 , with an upper support structure  14 , a lower support structure  16 , and vertical support structures  18 . The hydroforming apparatus  10  is equipped with cooperating die structures, which may include an upper die structure  20 , and a lower die structure  21 . The upper die structure  20  can be raised and lowered so that the die structures  20 ,  21  are moveable between open and closed positions. The die structures  20 ,  21  are shown in the closed position in FIG.  1 . The dies  20 ,  21  provide die surfaces  22 , defining a sealed die cavity  23  when the dies  20 ,  21  are in the closed position. The shape and size of the die cavity  23  is configured to form the desired shape and size of the part to be hydroformed. FIG. 1 shows a tubular metal blank  24 , which has been placed into the die cavity  23  to be hydroformed. The opposite ends of the tubular metal blank  24  are sealingly engaged by a pair of hydraulic tube-end engaging structures, or “hydraulic rams”  25 , which are movable into varied positions driven by a hydraulic actuator  26 . Each ram  25  has a cental port  27  through which extremely high pressure hydroforming fluid (e.g., approximately 10,000 atms.) is injected into the tubular metal blank  24 . 
     Incorporated into at least one of the die structures  20 ,  21 , is a reciprocating hydropiercing punch assembly, generally indicated at  50 , which is shown in detail in FIG.  3 . 
     The hydroforming apparatus  10  is equipped with a flushing fluid system, generally indicated at  30 , which communicates with the die cavity  23 . The flushing fluid system  30  is used to remove at least one punched out portion, or “slug”  86 , of the expanded metallic tube  24 , (as shown in FIG.  4 ). The flushing fluid system  30  includes a flushing fluid inlet port  32  which is located at on e end of the die cavity  23  and a flushing fluid outlet port  33  which is located at the opposite end of the die cavity  23 . Preferably, both of these ports  32  and  33  are formed into the lower die structure  21  as shown. The flushing fluid system  30  preferably includes a scrap separator generally indicated at  34  with a mesh or screen  36 . Also, the flushing fluid system preferably includes a fluid reservoir  38  which can be used for storing and/or recycling the flushing fluid, if desired. The flushing fluid system  30  also includes connecting plumbing lines  42  and a circulator  40  for circulating the flushing fluid through the flushing fluid system  30 . 
     Referring now to FIG. 3, the hydropiercing punch assembly  50 , is shown in greater detail. The punch assembly  50  is used to punch a hole  84  (as shown in FIG. 4) into the expanded metallic tube  24 . Any number of similarly designed punch assembly  50  may be incorporated into one or more of the die structure(s)  20 ,  21 . The punch assembly  50  includes a punch receiving passage  51  that is incorporated into the die structure(s) and through which a punch  52  may be moved between a retracted and an extended position. The punch  52  is movable in slidable, sealed relation with respect to the passage  51  by virtue of an annular seal member  53  therebetween. The punch assembly  50  includes a punch driver assembly generally indicated at  54 , which is used to drive the punch  52  between the retracted and extended positions. In the retracted position, the distal end surface  55  of the punch  52  is flush with the die surfaces  22 , and helps to define the die cavity  23 . The punch driver assembly  54  includes a punch driver  56 , which may be a hydraulic cylinder, that is connected to a punch piston  58 . The proximal end  59  of the punch  52  is secured to and connected to the punch piston  58 . The punch piston  58  is movable between a retracted and an extended position. The punch  52  traverses through an opening  62  in a punch driver housing  60  in slidable relation with respect to the opening  62 . 
     The flushing fluid system  30  may include a slug disengaging system, generally indicated at  70 , which can provide a means of disengaging the slug  86  from the end working surface  55  of the punch  52 . At least one of the die structures  20 ,  21  is mounted to a slug disengaging fluid bulkhead  72 . A peripheral seal  74  between the die structure  20 ,  21  and the bulkhead  72  surrounds the slug disengaging system  70  so that the slug disengaging system  70  is sealed from atmosphere and can be pressurized with slug disengaging fluid. The slug disengaging system  70  includes a slug disengaging fluid input port  76  which is located on the slug disengaging fluid bulkhead  72 . The slug disengaging fluid input port  76  can be connected to any suitable high pressure pump to provide pressurized slug disengaging fluid to the slug disengaging system  70 . The slug disengaging fluid input port  76  is connected to a slug disengaging fluid passageway  78  which can be common to several punch assemblies  50 . The passageway  78  can be any suitably sized groove formed into the die structure(s)  20 ,  21 . The passageway  78  communicates with a slug disengaging fluid pressure chamber  79  that can be formed into the die structure(s)  20 ,  21 . The punch  52  includes a slug disengaging fluid port  80  which traverses longitudinally through the punch  52 . The slug disengaging fluid port  80  originates at a slug disengaging fluid inlet  82  located on the side of the punch  52  and terminates with an outlet  83  at the punch working surface  55 . The slug disengaging fluid inlet  82  can be located so as to communicate with the slug disengaging fluid pressure chamber  79  when the punch  52  is in the extended position so that the slug disengaging fluid port  80  can be pressurized with slug disengaging fluid as desired. 
     Operation of the hydroforming apparatus  10  will now be described. Referring to FIG. 2, the metallic tube  24  is expanded under hydroforming fluid pressure into conformity with the inner surfaces  22  of the die cavity  23  and into engagement with the working surface  55  of the punch  52  which is in the retracted position. So as to maintain predetermined wall thickness of the expanded metallic tube  24 , the hydraulic rams  25  are forced inwardly toward one another to create metal flow within the tube  24  as the tube  24  is being expanded. 
     In FIG. 4, the punch driver or cylinder  56  is actuated and drives the punch piston  58  into the extended position. This action drives the punch  52  from the retracted position to the extended position after the metallic tube  24  has been expanded into conformity with the die surfaces  22 , thus forcing the punch  52  through the expanded metallic tube  24  so as to punch a hole  84  in the expanded metallic tube  24 , and so as to form the slug  86 . Hydroforming fluid is maintained under high pressure within the expanded metallic tube  24  to provide interior support to the tube  24  during the hole punching sequence in order to prevent deformation of the expanded metallic tube  24  by the punch  52  at areas adjacent to the punched hole  84 . The die structures  20 ,  21  are maintained in the closed position, and the expanded metallic tube  24  maintains engagement with the surfaces  22  of the die cavity  23 . In the extended position, the punch  52  serves to seal the hole  84  that has been punched into the tube  24  thus aiding to maintain fluid in the tube  24  so as to inhibit the escape of fluid from the tube  24  during a subsequent slug flushing operation. 
     FIG. 5 shows the punch  52  in the extended position in greater detail. The slug disengaging fluid inlet  82  communicates with the slug disengaging fluid pressure chamber  79  thus permitting flow of the slug disengaging fluid through the slug disengaging fluid port  80 . 
     Referring now to FIG. 6, at least one of the hydraulic rams  25 , that is, at least the ram adjacent to the outlet port  33 , but preferably both rams, is movable out of sealed engagement with the end(s) of the expanded metallic tube  24 , thus permitting the hydroforming fluid in the tube  24  to become depressurized. The hydraulic rams  25  are now positioned so as to facilitate flow of flushing fluid and removal of the slug  86  from the tube  24 . The die structures  20 ,  21  remain in the closed position and the flushing fluid system  30  communicates with the die cavity  23  to provide flow of flushing fluid to the interior of the expanded metallic tube  24 . 
     Typically, the slug  86  may remain engaged to the end working surface  55  of the punch  52 . If this is the case, the invention provides various means for disengaging the slug  86  from the end working surface  55  of the punch  52 . 
     In one embodiment, the slug  86  can be forcibly disengaged from the end surface  55  of the punch  52  by pressurization of the slug disengaging system  70  which forces fluid through the fluid port  80  and detaches the slug  86  from the working surface  55  of the punch  52 . Alternatively, the punch driver  56  may be used to rapidly reciprocate the punch  52  to disengage the slug  86  from the working surface  55  of the punch  52 . 
     In yet another embodiment, the slug  86  can be forcibly disengaged from the end working surface  55  of the punch  52  solely by rapid flow of flushing fluid through the tube  24  as provided by the flushing fluid system  30 . 
     The flushing fluid circulator  40  and the connecting plumbing lines  42  provide sufficiently high flow rate of flushing fluid so as to flush the detached metal slug  86  through the expanded metallic tube  24  and to remove the slug  86  from the tube  24 . The flushing fluid flows through the inlet port  32 , passes through the tube  24  and carries the slug  86  out through the opposite end of the tube  24  and out through the outlet port  33 . The outlet port  33  and the connecting plumbing lines  42  are suitably sized with wide enough inner diameter so as to permit the unobstructed flow of the flushing fluid and the slug  86  out of the die  21 . Once the metal slug  86  is removed from the die  21 , the slug  86  can be separated from the flushing fluid by the mesh or screen  36  in the scrap separator  34 , and the fluid can be recovered into the fluid reservoir  38 . During the flushing fluid sequence, the punch  52  is maintained in the extended position so as to prevent leakage of flushing fluid through the punched out hole  84  in the tube  24 . 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not limiting in character, it being understood that the preferred embodiment has been shown and described and that all changes and modifications that come within the scope of the appended claims are to be protected.