The present invention relates generally to the stretching and bending of symmetric and non-symmetric elongated hollow wor pieces (in cross section) and particularly to quick release mandrels and jaws that seal and secure the ends of workpieces in clamp assemblies of stretch bend apparatus for high volume production of stretched and bent workpieces.

Elongated hollow members can take many shapes in cross section. This is particularly true for hollow aluminum extrusions that are employed in constructing spaceframes for motor vehicles/ for example, as shown in U.S. Patent No. 4,618,163 to Hasler et al. Such extrusions are stretched and bent to provide lineals having appropriate shapes for forming a vehicle frame, as a frame cannot be constructed with straight pieces only. The underlying principle of stretch forming involves applying tension to a generally straight workpiece such that it yields plastically, and deformation is imposed by bending or wrapping the workpiece around the curved surface of a die that results in proper modes of plastic flow so that the workpiece retains the desired linear configuration after

stretching and bending. Stretch bend apparatus includes plugs or mandrels that seal and support the ends of the extrusion workpiece when the ends are gripped by jaws of the apparatus. The plugs or mandrels and the jaws must have the configuration in cross section of the workpiece ends if they are to properly seal and support the ends. If spaceframes consisted of members having one configuration in cross section, there would be no problem in regard to changing mandrels and jaws of the stretch bend apparatus, as only one mandrel and jaw set would be required. However, since spaceframe extrusions take a variety of shapes, mandrels and jaw sets are needed to match each of these shapes for the stretching and bending process. In an eight- hour work shift, for example, different shapes are required to be formed. This requires rapid removal from and the insertion of tooling into the stretch bend apparatus so that production downtime is kept to a minimum.

The invention includes two unitary mandrels for receiving opposed ends of a hollow elongated workpiece, the mandrels being quickly inserted into and removed from two tool holders respectively located in clamp assemblies. The invention includes, further, upper and lower jaws for each clamping assembly, the jaws including jaw holders that permit quick release from and insertion of the jaws and holders into the clamping assemblies.

The rapid installation of the mandrel must also provide rapid orientation of its cross section to match that of the extrusion ends and the jaws that grip the ends. It is desirable, therefore, to provide means that allows accurate, rapid rotational orientation of the

mandrel. The purpose of mandrels is to support the walls of the workpiece ends when the mandrel enters the ends and are gripped by the above jaws in the clamp assemblies. It is also desirable to provide an effective seal in the end of a hollow workpiece/extrusion after the mandrels enter the ends, and means for rapid pressurization of the workpiece interior by use of a dedicated opening in each mandrel for supplying a fluid medium directly to the workpiece interior without obstruction.

The objectives and advantages of the invention will be better understood from consideration of the following detailed description and the accompanying drawings in which:

Figure 1 is a generally schematic view of a conventional stretch-wrap or bend forming process and apparatus;

Figure 2 is a longitudinal sectional view of a clamp assembly of stretch bend apparatus, the assembly containing the quick release mandrel and jaws of the present invention;

Figure 3 is an end elevation of the apparatus of Figure 1 taken along lines 3-3 of Figure 2 and includes, in cross section, a non- symmetric workpiece mounted on the mandrel of Figure 2;

Figure 4 is a plan view of a lower jaw and jaw holder taken along lines 4-4 of Figure 3;

Figure 5 is a sectional view of the lower jaw of Figures 3 and 4 taken along lines 5-5 of Figure 4; and

Figure 6 is a side elevation view of a

nose piece of the mandrel shown in Figure 3.

Referring now to Figure 1 of the drawings, a fragmentary portion of a conventional stretch forming apparatus is shown in which a pair of opposed clamp assemblies 10 grip an elongated workpiece 12 to bend the same around the curved surface of a die 14. The clamp assemblies, in addition, apply a tension T to the workpiece using known tensioning means such as hydraulic piston cylinders (not shown) connected to the clamping assemblies. The amount of tension applied exceeds the elastic limit of the workpiece material. Such apparatus is shown in U.S. Patent Nos. 2,464,169, 4,704,886, 4,803,878, 4,815,308, and 4,827,753 to Bentley, Evert et al., and Moroney, respectively.

Heretofore, clamping assemblies have employed jaws bolted to the clamp assemblies to grip the outside surfaces of workpiece ends such that such jaws were not quickly and easily removed, and new jaws not easily inserted in place of those removed. If a workpiece was hollow such that the interior thereof could support a fluid medium under pressure to keep the wall of the workpiece from collapsing during stretching and bending, either separate plugs, i.e., separate from the clamp assemblies, were inserted in the workpiece ends to seal the same, such as shown in the above U.S. Patent Nos. 4,704,886 to Evert et al. or multiple piece mandrels, again bolted in the clamping assemblies, were used, as shown in the above U.S. Patent No. 4,803,878 to Moroney. In the present invention, separate plugs and permanently bolted tooling are not used. Rather, as shown in Figure 2 of the

drawings, the rear of a clamping assembly 10 is provided with a fixed tooling adapter or mount 15 that receives a mandrel 16 and secures the same in a quick release manner in the clamping assembly, i.e., tooling mount 15 has two opposed openings 17 that receive the ends of opposed, quick disconnect plungers 18. Plungers 18 are secured in opposed openings 19 provided near the rear of an integral extension 20 of the mandrel, the extension fitting over a hollow nipple 22 of tooling mount 15. The structure of each plunger is such that it is captured in a respective opening 19 in mandrel extension 20 and is provided with a mechanism (not shown) that retains the plunger in a withdrawn position and permits forward release of the plunger when it is rotated by a workman. Openings 17 and 19, when aligned with each other, allow quick insertion of plungers 18 into openings 17. With such insertion, mandrel 16 is quickly secured in the clamping assembly and is quickly removed when a production change is required.

The process of insertion and rapid connection of mandrel 16 in clamping assembly 10 requires also that the mandrel be correctly oriented (rotated) relative to the jaws of the assembly (discussed below) . This is effected by a small pin 23 extending from the rear surface of mandrel extension 20 and a matching corresponding opening or recess 24 provided in tooling mount 15. Hence, when a workman inserts the mandrel over nipple 22 of the tooling mount, the mandrel is quickly properly oriented by the workman by simply rotating the mandrel until pin 23 seats into opening 24. Plungers 18 cannot be used for this purpose, as they are retracted during insertion of the mandrel, and are not

easily seen by the workman when inserting the mandrel.

Mandrel 16 includes a main body portion 25 having the same configuration in cross section as that of a workpiece 26, as seen in Figure 3 of the drawings. As explained earlier, workpieces can have non-symmetrical shapes, including an integral flange or arm 27, as shown in Figure 3. Only one mandrel 16 is depicted in

Figures 2 and 3 since a second mandrel (not shown) located in a second clamp assembly (not shown) opposite that of 10 is identical to the mandrel shown. Each mandrel is provided with a dedicated opening 28 (Figure 2) for supplying a fluid medium, such as plant air, to the interior of workpiece 26 receiving the body portion 25 of the mandrel. A fluid medium can be used to support the walls of 26 while it is being stretched and bent by the apparatus of Figure 1. Opening 28 is completely unobstructed and is dedicated to supplying such a medium to the interior of a hollow workpiece to rapidly pressurize the same for the bend stretch process, if needed. This is quickly accomplished by the use of a fitting 30 that allows quick connection and disconnection of an air hose (not shown) to 30.

The main body portion 25 of mandrel 16 includes a nose member 31 that is separate from 25 but is an integral part thereof through the agency of an elongated, translatable bolt 32 and an elastomer gasket 33 compressible between 25 and 31 by the bolt. The shape of 31 and 33 is that of the main body 25 of the mandrel, which is that of the workpiece (26) to be formed over die 14 (Figure 1) . Bolt 32 is connected to an

actuator (not shown) located behind clamping assembly 10. The actuator is operative to move the bolt in both directions along the bolt axis in a manner explained hereinafter. When the interior of the workpiece is to be pressurized, bolt 32 is translated rearwardly to move nose piece 31 against the main body 25 of the mandrel. This squeezes gasket 33 and expands it, as shown in phantom in Figure 2; the squeezing and expansion of the gasket occurs after the mandrel is moved forward and into the end of the workpiece.

When mandrel 16 is mounted in a clamp assembly 10, it is slipped over translatable bolt 32. This requires the mandrel to be provided with an opening 34 dimensioned to receive bolt 32. The mandrel includes, of course, nose member 31 and gasket 33. To retain the nose member and gasket on bolt 32, a nut 35 is threaded on the end of the bolt. For this purpose, nut 35 is preferably a hand tightenable torque nut so that the installation and removal of the mandrel is toolless. Nose piece 31 and gasket 33 can be retained together on mandrel 25 when not mounted on a bolt by two pins 31A and B(Figure 6) that extend from the rear of 31, through gasket 33, into the mandrel body 25.

The main body 25 of each mandrel 16 receives one end of a workpiece 26 and supports the end wall thereof against the clamping force of upper and lower jaws 38 and 39 that grips the ends of a workpiece (26) for stretching and bending. Again, like the exterior surfaces of the mandrel, the jaws have inner surfaces 36 that are configured to the exterior surfaces of workpiece 26, including two opposed flat surfaces 37 that engage between them the

extension 27 (Figure 3) of the workpiece.

Again, when a workpiece (26) having a cross section different from the one currently in production is required to be formed by the stretch bend apparatus of Figure 1, the jaws 38 and 39 in current use must be quickly removed from clamping assemblies 10 and replacement jaws inserted into 10 that match the configuration of the different workpiece. This is effected by jaw holders 48 and 49 that seat and secure the respective jaws 38 and 39 in the clamping assemblies, and four retractable, quick change plungers 42 (Figures 2 and 3) secured in the jaw holders. More particularly, jaw holders 48 and 49 comprise a frame 46 having a rectangular internal hollow recess 47 (Figure 4) sized to receive and hold a jaw 38 or 39.

Each jaw holder 48 and 49 seats on a round adapter nipple or mount 50 secured in upper and lower portions 52 and 54 of the clamping assemblies 10 by bolts 56 (Figure 2) . Each adapter 50 is provided with opposed recesses or openings 58 that receive the forward portions of quick change plungers 42, as seen again in Figure 2. The quick change plungers 42, like those of 18 that secure the mandrel, provide rapid removal of a jaw set from assembly 10 and the insertion of a new set. Jaws 38 and 39 are secured in the holders 48 and 49 in a manner discussed in detail hereinafter.

Lateral adjustment of jaws 38 and 39 in jaw holders 48 and 49 is effected by providing a space 60 (shown exaggerated in Figure 5) between one edge of each jaw and one end of the recess 47 in each jaw holder, and the use of shims 62 inserted into space 60, as seen in Figures 4 and 5. The proper selection of

shims provides precise lateral positioning of the jaws relative to workpiece 26 (Figure 3) . The shim(s) are held in place by two fasteners 64 threaded through a wall portion 66 of each jaw holder 48 and 49 (Figures 4 and 5) to engage and force the jaw (38, 39) against the shim(s) and the end surface of recess 47. The jaws themselves are secured in their respective jaw holders by two bolts 68 threaded into the rear wall 69 (Figure 5) of each jaw holder. Further, as seen in Figure 4, the jaws are provided with recesses 70 that permit lateral movement of the jaws relative to bolts 68 and jaw holders 48, 49 before bolts 68 are tightened against the jaws. Figure 4 shows, in addition, an eye bolt 71 threaded into frame 46 that holds jaw 39. Eye bolt 71 is employed to connect a snake tool device to the clamp assemblies before the workpiece is stretched and bent, as described in an application entitled "Snake Tool for Bending Workpieces". The inventor named in this application is Robert E. Weykamp, one of the inventors of the present application.

Shim(s) 72 (Figure 5) can also be provided in the bottom of the recess 47 of jaw holders 48, 49 if the jaws 38 and 39 are not precisely vertically located relative to the vertical position of workpiece 26. Shim(s) 72 are placed in the jaw holder before the jaw is inserted and secured in place by bolts 68.

In operation of the apparatus of the Figures, as thus far described, when it is decided that a workpiece shape 26 is required to be formed by the apparatus that is of a shape different from the one currently being formed, a workman removes the current workpiece from mandrel 16 and jaws 38 and 39, in current use,

in clamping assemblies 10. This requires the workpiece to be free of the jaws, which is effected by a piston/cylinder (not shown) that moves at least one of the jaws away from the workpiece. Such a cylinder is located in the upper portion 52 of each clamping assembly 10 such that in Figure 3 upper jaw 38 and jaw holder 48 are depicted in a position removed from the workpiece. The current workpiece is also depressurized, if pressurized, before it is removed from the clamping assemblies. This is effected by a relief valve in a pressurizing system which exhausts through dedicate opening 28 provided in mandrel 16. The translation of upper jaws 38 and that of bolts 32 is effected automatically in the operation of the apparatus depicted schematically in Figure 1, such apparatus using appropriate control devices and circuits associated with actuators of the apparatus.

With the current workpiece depressurized and its ends released from the jaws, bolt 32 is moved forward to release squeezing pressure on gasket 33, which thereby reduces the diameter of the gasket. The entire mandrel 16 is now withdrawn from the workpiece end by action of bolt 32 being translated to the rear by a cylinder (not shown) . The workman then slips the workpiece from the clamp assemblies and jaws. The current workpiece is now suitably disposed of and the workman next releases the current mandrel 16 and current jaw holders 48 and 49 by rotating quick-release plungers 18 and 42 and pulling them from the openings 19 in flanges 17 to release the mandrel, and from the openings 58 in adapter

mounts 50 to release the jaw holders. Release of the mandrel also requires removal of nut 35 from bolt 32. The released mandrels and jaw holders are suitably stored and a new mandrel and jaw holders, with jaws and shims, are obtained by the workman that fit the shape of the next workpiece to be formed. The new mandrel is slipped over bolt 32 and nipple 22 of tooling mount 15. The new mandrel has its own retained quick-release plungers 18 so that when the rear face of the mandrel abuts against the tooling mount, and the mandrel is rotated until pin 23 enters aperture 24 in the tooling mount, plungers 18 are properly oriented relative to openings 17 in the tooling mount. The plungers are rotated and released into openings 17, thereby securing the mandrels in the clamping assemblies. Nuts 35 are now threaded onto bolts 32. The new mandrels are also correctly oriented with new jaws 38 and 39 that the workman installs in the clamp assemblies. This is effected by placing new jaw holders 48 and 49 on respective mounts 50 in the clamping assemblies. (Adjustment of jaws in the jaw holders is done only once using shims 62 and 72 if needed, when the first workpiece of a particular shape is disposed in the clamp assemblies for forming.) The workman then quickly releases plungers 42 into openings 58 in the mounts to effect rapid securing of the jaw holders in the clamping assemblies. The clamp assemblies are now ready to receive the new workpiece shape (26) to be formed by the apparatus of the Figures.

When the new workpiece 26 is located in place between jaws 38 and 39, mandrels 16 are

moved to insert their main body portions 25 into the workpiece ends. Bolts 32 and nuts 35 are next translated rearwardly to move nose piece 31 of the mandrel against gasket 33. This expands the gasket into tight engagement with the inside surfaces of the workpiece walls. Jaw holders 48 and 49 are now moved toward the workpiece ends to locate jaws 38 and 39 in gripping engagement with the workpiece ends, the mandrel portions 25, 31 and 33 supporting the walls of the workpiece against the gripping force of jaws 38 and 39.

Further, if the workpiece is to be pressurized with a suitable medium, fitting 30 and dedicated opening 28 in the mandrel provides rapid entry of air into the workpiece interior. Gasket 33 seals the pressurized air in the workpiece until the workpiece is depressurized. The time required to remove mandrels and jaws in current use and insert new ones is on the order of 2 minutes for both clamp assemblies.

While the invention has been described in terms of preferred embodiments, the claims appended hereto are intended to encompass all embodiments which fall within the spirit of the invention.