Mandrel with elastic sleeve utilizing hydraulic pressure for hydroforming hollow metal cylinders

Abstract

A mandrel with an elastic sleeve utilizing hydraulic pressure for hydroforming hollow metal cylinders is disclosed. This invention simplifies the manufacturing process of the hydroforming device and reduces the associated cost, through the use of fluid pressures upon the elastic sleeve that biases forcefully against the interior of the metal cylinder being shaped. In the case where containment of the hydorforming fluid is desired, so as to prevent any contamination of the interior of the cylinder being shaped, this technology can provide that containment more reliably. The elastic sleeve material used is reasonably flexible, and more durable than other materials used in related devices.

I claim: 
     
         1 . An apparatus for radially expanding a cylinder by hydroforming the same utilizing hydraulic pressure, comprising:
 a metal cylinder to be expanded;   a mandrel provided for insertion into said metal cylinder in preparation for performance of the hydroforming function;   an elastic sleeve provided upon the mandrel at least along a portion of its length, and said elastic sleeve arranged in contiguity with the interior of the cylinder to be hydroformed;   said mandrel having an internal approximate axial pathway through which hydraulic fluids may insert during hydroforming, said mandrel having at least one approximate radial pathway extending from its axial pathway to the surface of the mandrel, and said pathways providing the means for introducing a pressurized fluid to the area between the mandrel and its elastic sleeve to expand the elastic sleeve against the interior of the cylinder being hydroformed interiorly thereof;   seals provided between the elastic sleeve and the surface of the mandrel to seal in pressurized fluid during hydroforming;   said mandrel at one end having an adapter to which a high pressure fluid source may connect therewith for introducing pressurized fluids into the mandrel in preparation for the performance of hydroforming process upon the associated metal cylinder.   
     
     
         2 . The apparatus of  claim 1  and including a series of O-rings provided upon said mandrel and the interior of said elastic sleeve to contain the pressurized fluids therein during performance of a hydroforming function. 
     
     
         3 . The apparatus of  claim 1 , wherein said elastic sleeve slides onto said mandrel and contacts the O-rings operatively associated with said mandrel to form a hydraulic fluid pressure expansion zone between said elastic sleeve, and the exterior of said mandrel, to obtain expansion of the elastic cylinder when hydroforming a metal cylinder into an expanded shape. 
     
     
         4 . The apparatus of  claim 3 , wherein said elastic sleeve extends over the substantial length of the said mandrel when assembled for a hydroforming operation. 
     
     
         5 . The apparatus of  claim 4 , and including a bushing provided at each end of the elastic sleeve, and retaining washers and threaded nuts applied to each end of the mandrel to hold the said bushings in place against the ends of the elastic sleeve to assure retention of the pressurized hydraulic fluid during performance of a hydroforming operation. 
     
     
         6 . The apparatus of  claim 5 , and including a back up ring provided between the end of the mandrel and within the adapter to maintain a seal of the pressurized fluid as it enters into the mandrel during performance of a hydroforming function. 
     
     
         7 . The apparatus of  claim 6 , and including a further O-ring provided to form the seal between the adapter and the proximate end of the mandrel to assure fluid sealing at that position. 
     
     
         8 . The apparatus of  claim 1 , wherein said elastic sleeve is formed of a polymer. 
     
     
         9 . The apparatus of  claim 8 , said polymer is a polyurethane.