Abstract:
A hydroform seal assembly includes a seal housing and an annular nozzle carried by the seal housing and sized to insert into a tube end. A first actuator moves the seal housing to insert the nozzle. A plurality of jaws are carried by the seal housing and are movable radially inward into clamping engagement with the tube to clamp the tube onto the annular nozzle. A cam bushing is movably mounted within the seal housing, surrounds the jaws, and has cam surfaces complimentary with cam surfaces provided on the jaws so that movement of the cam bushing relative the jaws will cam the jaws radially inward. A backup cam is movable within the seal housing. The cam bushing and backup cam have complimentary cam surfaces by which movement of the backup cam will forcibly move the cam bushing relative the seal housing. A second actuator moves the backup cam.

Description:
RELATED APPLICATION 
     This application is a continuation-in-part of U.S. Ser. No. 11/674,271 filed Feb. 13, 2007. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to hydroforming and, more particularly, to a hydroform die tube sealing assembly sealing the end of a tube during hydroforming. 
     BACKGROUND OF THE INVENTION 
     It is known that a tube may be hydroformed to a desired complex shape. The tube is placed between a pair of dies having cavities which will define the resultant shape of the tube. The ends of the tube are accessible through the die and a seal is connected to each end of the tube. Pressurized fluid is injected through one of the seals to force the tube to expand into the shape of the die cavity. 
     It is desirable that the seal be sufficiently able to withstand the high operating pressures required for hydroforming. It is also desirable that the seal be durable to permit its repeated use without excessive maintenance, repair or replacement in the harsh manufacturing environment of high pressure hydroforming. 
     As a result, it would be desirable to provide a new and improved hydroform die sealing assembly of high durability and consistently assured sealing against leakage. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is a hydroform die tube sealing assembly. The hydroform seal assembly includes a seal housing and an annular nozzle carried by the seal housing and sized to insert into a tube end. A first actuator moves the seal housing to insert the nozzle. A plurality of jaws are carried by the seal housing and are movable radially inward into clamping engagement with the tube to clamp the tube onto the annular nozzle. A cam bushing is movably mounted within the seal housing, surrounds the jaws, and has cam surfaces complimentary with cam surfaces provided on the jaws so that movement of the cam bushing relative the jaws will cam the jaws radially inward. A backup cam is movable within the seal housing. The cam bushing and backup cam have complimentary cam surfaces by which movement of the backup cam will forcibly move the cam bushing relative the seal housing. A second actuator moves the backup cam. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a fragmentary elevation view having parts broken away and in section, of a hydroform die tube sealing assembly, according to the present invention. 
         FIG. 1A  is an enlarged view of a portion in oval  1 A of the hydroform die tube sealing assembly of  FIG. 1 .  FIG. 1B  is and end view taken in the direction of arrows  1 B- 1 B of  FIG. 1 . 
         FIG. 2  is a view similar to  FIG. 1  illustrating a first step of operation of the hydroform die tube sealing assembly of  FIG. 1 . 
         FIG. 2A  is an enlarged view of a portion in oval  2 A of the hydroform die tube sealing assembly of  FIG. 2 . 
         FIG. 3  is a view similar to  FIG. 1  illustrating a second step of operation of the hydroform die tube sealing assembly of  FIG. 1 . 
         FIG. 3A  is an enlarged view of a portion in oval  3 A of the hydroform die tube sealing assembly of  FIG. 3 . 
         FIG. 4  is a view similar to  FIG. 1  illustrating a third step of operation of the hydroform die tube sealing assembly of  FIG. 1 . 
         FIG. 4A  is an enlarged view of a portion in oval  4 A of the hydroform die tube sealing assembly of  FIG. 4 . 
         FIG. 5  is a view similar to  FIG. 1  illustrating a fourth step of operation of the hydroform die tube sealing assembly of  FIG. 1 . 
         FIG. 6  is a and elevation view of the tail end of the tube sealing assembly showing reinforcement bars in open position. 
         FIG. 7  is a view similar to  FIG. 6  but showing the reinforcement bars in closed position. 
         FIG. 8  is a perspective view showing the mechanism for operating the backup cams and reinforcement bars. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to the drawings and in particular  FIGS. 1 and 1A , a tube sealing assembly  10 , according to the present invention, is shown for hydroforming a tube or tubular member  12 . The tube sealing assembly  10  includes a seal unit, generally indicated at  14 , to seal the open end of the tube  12 . A similar tube sealing assembly  10  and seal unit  14  would be provided at the other end of the tube  12 . 
     A die set, generally indicated at  16 , is comprised of an upper die half  18  and a lower die half  20 . The upper die half  18  includes a cavity portion  19  and the lower die half  20  includes a cavity portion  21  for receiving the tubular member  12 . It should be appreciated that the upper die half  18  and lower die half  20  will be progressively closed from the position of  FIG. 1  so that the tubular member  12  will be captured within the cavity portions  19  and  21  of the die set  16 . 
     An upper mounting plate  22  is connected to the upper die half  18  and a lower mounting plate  24  is connected to the lower die half  20 , by suitable fasteners (not shown). The mounting plates  22  and  24  are generally rectangular in shape. The mounting plates  22  and  24  are made of a rigid material such as metal. The mounting plates  22  and  24  extend longitudinally from the die halves  18  and  20  and are spaced from and oppose each other. 
     An upper support block  26  connected to the upper mounting plate  22  and a lower support block  28  connected to the lower mounting plate  24  by a suitable fasteners (not shown), and will be discussed further hereinafter. 
     The tube sealing assembly  10  is mounted on a seal unit elevator member  30  supported on the mounting plate  24  attached to the lower die half  22 . The seal unit elevator member  30  includes a bed  31  that is mounted on the lower mounting plate  24  by a plurality of springs  35 , which are preferably nitrogen filled die springs that will allow the elevator member  30  to rise and fall somewhat relative the lower mounting plate  24  so that the seal unit  14  can align itself with the end of the tube  12 . The lower support block  28  engages the end of the bed  30  and supports the bed against movement left and right while allowing up and down movement on the springs  35 . 
     The seal unit  14  includes a seal housing  42  that is slidably supported on the elevator member  30 . In particular, the bed  31  of the elevator member  30  has rails  33  which engage in channels  34  provided in the seal housing  42  so that the housing  42  can slide left and right on the bed  31  of elevator member  30 . As seen in  FIG. 1 , the seal housing  42  is hollow and carries within it an annular nozzle  60 , an annular collet retainer  80  that surrounds the annular nozzle  60 , and an annular cam bushing  49  that surrounds the collet retainer  80 . The annular nozzle  60  and the collet retainer  80  are bolted together by bolts  61 , and the collet retainer  80  is bolted to the seal housing  42  by bolts  63 . Thus the annular nozzle  60  and collet retainer  80  are fixed to the seal housing  42  and move therewith as the seal housing  42  slides left and right on the bed  31  of the elevator member  30 . The annular nozzle  60  has an outer surface that is sized to fit closely within the inside of the tube  12 . 
     The elevator member  30  has a tail  39  that extends upwardly from the bed  31  of the elevator member  30  and mounts a hydraulic cylinder  38 . The hydraulic cylinder  38  has a shaft  40  that is connected to the annular nozzle  60  by a bolt  41  so that energizing the hydraulic cylinder  38  will push or pull the annular nozzle  60  and the seal housing  42  to slide left and right on the rails  33  of the elevator bed  31 . 
     Referring again to  FIG. 1 , it is seen that the annular cam bushing  49  surrounds the collet retainer  60  and has an outer surface that slides with a bore  44  provided in the seal housing  42 . A plurality of coil springs  58  are disposed between the housing  42  and the cam bushing  49 . The springs  58  extend longitudinally between a shoulder  54  of the cam bushing  49  and a first shoulder  46  of the seal housing  42  and act to urge the cam bushing  49  axially rightward as viewed in  FIG. 1 . 
     As seen in  FIGS. 1 ,  1 A, and  1 B, a plurality of jaws  70 A,  70 B,  70 C and  70 D are captured between the outside of the annular nozzle  60  and the inside of bore  50  of the cam bushing  49 . As best seen in  FIG. 1A , the jaw  70 D is coupled to the collet retainer  80  by a loose fitting interlocking structure including an annular flange  78  on the jaw  70 D that fits in an annular groove  84  on the collet retainer  80 , and an annular flange  86  on the collet retainer  80  that fits into an annular groove  76  on the jaw  70 D. In this manner, the jaw  70 D is effectively captured against removal and connected for axial movement with the collet retainer  80 , while the jaw  70 D can pivot or rock and shift axially somewhat relative to the collet retainer  80 . The inside of the jaws  70  D rests upon an O-ring seal  88  that is seated in an annular groove  68  in the outer surface of the annular nozzle  64 . The outside of the jaw  70 D has a cam surface  87  thereon and a corresponding cam surface  89  is provided on the bore  50  of the cam bushing  49 . 
       FIG. 1  also shows that seal housing  42  has a vertical cavity  48  provided therein in which a pair of backup cams  90  and  91  are vertically slidable. These backup cams  90  and  91 , as well as the mechanism for moving the backup cams  90  and  91  are best shown in  FIG. 8 . As seen in  FIGS. 1 and 8 , the back up cams  90  and  91  are spaced apart to straddle the annular nozzle  60  and the collet retainer  80 , and are moved vertically up and down, transverse to the axial direction of movement of the cam bushing  49 . A hydraulic cylinder  36  is mounted on the underside of the seal housing  42  and a shaft  37  that carries a connector bar  93 . Backup cam  90  has a rod  95  attached to the connector bar  93 , and backup cam  91  has a rod  97  attached to the connector bar  40 . As seen in  FIG. 1 , forward face of the backup cams  90  have inclined surfaces  92  that bears upon a complimentary inclined surface  56  provided on the cam bushing  49 . Thus, as the backup cams  90  and  91  are moved up and down by the cylinder  33 , the cam bushing  49  will travel right and left. And as the cam bushing  49  travels left and right, the jaws will be shifted radially inward or outward. 
     Referring to  FIGS. 6 ,  7  and  8 , it is seen that reinforcement bars  94  and  96  are pivotally mounted at their lower ends to the seal housing  42  by pivot bolts  98  and  100 . A connecting arm  104  has a slot  106  at its left end which fits over a pin  108  carried on an offset arm  110  of the reinforcement bar  90 . The right hand end of the connecting bar  104  has a slot  112  that fits over a pin  114  mounted on an offset arm  116  of the reinforcing bar  96 . As best seen in  FIGS. 3 and 6 , a connecting rod  120  reaches from the connector bar  93  of the shaft  37  of the hydraulic cylinder  36  to the connecting bar  104 . Accordingly, when the hydraulic cylinder  36  is in its extended position, the connecting rod  120  will establish the connecting arm  104  and the reinforcement bars  94  and  96  at the swung open position of  FIG. 6 . However, when the hydraulic cylinder  36  is actuated to pull down on the backup cams  90  and  91 , the connecting rod  120  is simultaneously pulled downwardly to pull down on the connecting rod  104  and thereby pivot the reinforcing bars  94  and  96  inwardly about their respective pivots  98  and  100  to the positions of  FIG. 7 . 
     Operation 
     Referring to  FIG. 1 , it is seen that the upper die  18  is raised and a length of tube  12  has been placed into the lower die cavity  21  of lower die  20 . Seal unit  14  is poised with its annular nozzle  60  spaced away from the end of the tube  12 , but is generally aligned with the end of the tube  12 . 
     In  FIG. 2 , the hydraulic cylinder  38  has been actuated and its shaft  40  extended to push the seal housing  42  leftwardly to the position shown in  FIG. 2 , where the end of the annular nozzle  60  has been inserted into the inside of the tube  12 , and the jaws  70 A,  70 B,  70 C and  70 D are poised about the outer surface of the tube  12  as shown in  FIG. 2A . 
     In  FIG. 3 , the hydraulic cylinder  36  has been actuated to pull down on the backup cams  90  and  91 , thereby forcing the cam bushing  49  leftwardly relative to the seal housing  42 , so that, as shown in  FIG. 3A , the cam surface  89  of the cam bushing  49  has become engaged with the corresponding cam surface  87  provided on the outside of the jaw  70 D, thereby forcing the jaw  70 D to bodily shift radially inward into clamping contact with the outside of the tube  12 . Simultaneously the other jaws  70 A, B and C are also bodily shifted into clamping engagement so that the tube  12  is tightly clamped onto the outside surface of the annular nozzle  60  to provide a pressure tight seal between the tube and the nozzle  60 , as shown in  FIG. 3A . 
     As seen in  FIG. 3 , the hydroforming fluid at high pressure will then be introduced into the tube  12  in order to expand the tube  12  outwardly into the die cavities  19  and  21 . It will be recognized that the hydroforming pressure will act on the seal unit  42  urging it to move rightwardly against the holding force of the hydraulic cylinder  38 . However, as seen in  FIG. 3  the actuation of the hydraulic cylinder  36  to pull down on the backup cams  90  and  91  has also caused the reinforcement blocks  94  and  96  to be swung into position of  FIG. 7 . And, as best seen in  FIG. 3 , when the reinforcing blocks  94  and  96  are swung in to be engaged against the seal housing  42 , and then the upper die  16  is lowered, the upper support block  26  will be lowered into engagement with the reinforcing blocks  90  and  91 , as best seen in  FIG. 3 . Accordingly, it is seen that the reinforcing bars  94  and  96 , when engaged by the upper support blocks  26 , will effectively block and restrain the seal housing  42  against any rightward movement that may be induced by the hydroforming pressure applied within the tube  12 . 
     After the hydroforming pressure has been applied to the inside of the tube  12  and the tube  12  fully expanded, the pressure will then be released from the tube  12  so that the seal unit  14  may be removed. Accordingly the hydraulic cylinder  36  is actuated to lift the backup cams  90  and  91  upwardly, as shown in  FIG. 4 , thus permitting the springs  58  to shift the cam bushing  49  rightwardly to release the jaws  70 A,  70 B,  70 C and  70 D from their clamping engagement against the outside of the tube  12 , as shown in  FIG. 4A . Simultaneously the upward movement of the backup cams  90  and  91  will, acting through the connecting rod  120  and the connecting arm  104 , cause the reinforcement blocks  94  and  96  to swing outwardly from their backup positions of  FIG. 7  to their resting positions of  FIG. 6 . 
     The upper die  18  can be opened either before or after the cylinder  36  is extended to raise the backup cams  90  and  91  and swing open the reinforcement blocks  94  and  96 . 
     After the backup cams  90  and  91  have been raised to release the jaws  70 A,  70 B,  70 C, and  70  D from clamping the tube  12 , the hydraulic cylinder  38  energized to retract the shaft  40  which in turn pulls the entire seal unit  14  rightwardly on the bed  31  so that the nozzle  60  is withdrawn from the end of the tube  12 . Then the tube  12  can be removed from the die. 
     Thus, it is seen that the invention provides a new and improved seal unit for use in a hydroforming operation. 
     The present invention has been described in an illustrative manner. It is to be understood that the terminology, which has been used, is intended to be in the nature of words of description rather than of limitation. 
     Many modifications and variations of the present invention are possible in light of the above teachings. Therefore, within the scope of the appended claims, the present invention may be practiced other than as specifically described.