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.

Claims

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.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In referring to the drawings:

[0013] FIG. 1 is an exploded prospective view of a disassembled mandrel assembly;

[0014] FIG. 2 is a longitudinal cross section of a mandrel assembly positioned in a tube located in a tube sheet ready to begin expanding;

[0015] FIG. 3 is an enlarged longitudinal cross section of the overlapping mating surfaces of an elastic sleeve and a sleeve retaining bushing;

[0016] FIG. 4 is a longitudinal cross section of the overlapping mating surfaces of an elastic sleeve and a sleeve retaining bushing described in the second embodiment; and

[0017] FIG. 5. is a longitudinal cross section of the overlapping mating surfaces of an elastic sleeve and a sleeve retaining bushing described in the third embodiment.

VARIOUS COMPONENTS OF THE INVENTION

[0018] M. Mandrel Assembly [0019] 1. Mandrel Shaft [0020] 2. Reduced OD of Mandrel Shaft between Annular Grooves [0021] 3. 3a & 3bThreaded Sections [0022] 4. 4a & 4bAnnular Grooves [0023] 5. High Pressure Connector [0024] 6. Recessed Section [0025] 7. Polyurethane Back-up ring [0026] 8. O-ring [0027] 9. 9a & 9bO-rings [0028] 10. Elastic Sleeve [0029] 11. Sleeve Retainer Bushing 11a & 11b [0030] 12. Spacer washers 12a & 12b [0031] 13. Nuts 13a & 13b [0032] 14. Axial Passageway [0033] 15. Radial Passageway [0034] 17. Mandrel AdapterThreaded [0035] 20. Mandrel Assembly Sleeve retaining bushing [0036] 21. Bushing Threads [0037] 22. Locking nut [0038] 23. Sleeve retaining bushing [0039] 24. Sleeve internal threads

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Description of the First Embodiment

[0040] Referring to FIG. 1 and FIG. 2, a mandrel assembly is made up of the following components. The components are made of appropriate high strength materials such as, but not limited to, steel, stainless steel, titanium, high strength metal alloys and plastic ceramics. An elastic sleeve, usually of a polymer, and made of polyurethane or similar materials with good machining and high elasticity properties. The choice of materials can vary based on the application and environmental requirements that the assembly may be used in it.

[0041] A mandrel shaft 1 is made up of an appropriate high strength material and is generally formed of a uniform diameter along its length where it joins with reduced diameter threaded sections 3a & 3b, and a further reduced diameter high pressure connection 5 outboard of threaded section 3b. This allows components mounted thereon to be slid off and replaced when required. Annular grooves 4a & 4b are formed in the major diameter section of the mandrel shaft 1. The mandrel shaft OD 2 between the annular grooves 4a & 4b is of a reduced OD slightly less than the major OD outboard of the grooves 4a & 4b. O-rings 9a & 9b which are made of a suitably soft material as known in the art encircle the mandrel shaft 1 and sit in the annular grooves 4a & 4b. The high pressure connection 5 is capable of joining the shaft to a variable pressure fluid supply up to 60,000 psi and has an annular recess 6 formed in it. A polyurethane backup ring 7 and O-ring 8, which is made of a suitably soft material, sits in the annular recess 6. The inner diameters of backup 7 and O-ring 8 must be slightly smaller than the annular recess 6 diameter. The outer diameter of backup 7 must be slightly smaller than the major diameter of the high pressure connector 5. The outer diameter of O-ring 8 must be slightly larger than the major diameter of the high pressure connector 5. An elastic sleeve 10 made of an appropriate material, as aforesaid, with good machining and elastic properties with an ID slightly larger than the mandrel shaft 1 major diameter allows it to slide in an axial direction on the mandrel shaft 1. The elastic sleeve 10 major OD is equal to the sleeve retainer bushings 11a & 11b OD. Sleeve retainer bushings 11a & 11b are made of an appropriate high strength material with an ID slightly larger than the OD of the mandrel shaft 1, has a major diameter to allow it to slide freely in an axial direction on the mandrel shaft 1. The mating surfaces 16a & 16b of the elastic sleeve 10 and sleeve retainer bushing 11a & 11b that overrides and join with the elastic expander 10 surfaces are an interference fit. The elastic sleeve 10 and sleeve retainer bushing 11a & 11b mating surfaces 16a & 16b can be an overlapping bevel surface, an overlapping step surface, or overlapping interlocking mating surfaces 16a as depicted in FIG. 3.

[0042] Outboard and adjacent to the sleeve retainer bushings 11a & 11b are retaining washers 12a & 12b are made of an appropriate high strength material with an ID slightly larger than the OD of the threaded sections 3a & 3b of the mandrel shaft 1, and an OD equal to the OD of the sleeve retainer bushings 11a& 11b. Outboard and adjacent to retaining washers 12a & 12b are nuts 13a & 13b that are secured in threaded engagement with threaded sections 3a & 3b of the mandrel shaft 1 and limits the axial movement of the components on the mandrel shaft 1 locking them in place. The mandrel shaft 1 has an axial oriented central bore 14 that intersects with a radially oriented bore 15 to provide a path for the pressurized fluid to reach the annular void between the mandrel shaft 1 and the elastic sleeve 10. Various configurations of high pressure adapters can be threaded onto the threaded end 3b of the mandrel to connect the mandrel shaft 1 to a high pressure fluid source.

[0043] The adapter 17, shown in FIG. 1 and FIG. 2, is shown as an example only and is not the sole means of connecting the mandrel shaft 1 to a high pressure fluid source. A high pressure flexible hose (not shown) may be attached directly to the mandrel assembly through an appropriately threaded mandrel adapter and used to supply pressurized fluid. This configuration allows for positioning the mandrel down a tube to a predetermined position from the tube end to hydroform the tube. The mandrel shaft 1 can be modified by continuing the axial passageway 14 through the mandrel shaft 1 instead of stopping it mid-shaft, and a high pressure connection 5 added to the threaded section 3a, may work appropriately at that end of the mandrel. This allows multiple mandrel assemblies of varying lengths to be interconnected end to end with interconnections of varying lengths. When activated, multiple locations can be hydroformed at similar or varying expansion lengths at the same time. The mandrel shaft 1 can include a safety vent passageway that allows the mandrel to be safely used to hydroform a hollow cylinder with a blind hole. The mandrel can be attached to a hand-held mandrel holder or a robotically controlled mandrel holder by changing the configuration of the mandrel adapter connections. An adjustable stop collar can be attached to the mandrel adapter by threads to facilitate fine adjustments in the mandrel insertion placement.

[0044] A technician would assemble the system as indicated above. The person would then insert the mandrel assembly into the material to be hydroformed. The person would actuate the power supply using either a remote operation switch on the mandrel holder handle or using a manual operation switch located on the power supply. Pressurized fluid would then be pumped from the power supply via a suitable umbilical capable of delivering the maximum rated output from the power supply's pump. The pressurized fluid will enter the mandrel via passageways 14 & 15 and enter the annular void between mandrel shaft 1 and the elastic expander 10. The pressurized fluid fills the void and exerts pressure radially on the elastic expander 10. The elastic expander 10 deforms radially exerting pressure on the metal cylinder, expanding it radially. The person would hold the switch until the indicators would indicate the hydroforming process is complete. When the hydroforming process is complete, the person would release the switch and then remove the mandrel assembly from the material.

Description of the Second Embodiment

[0045] Refer to FIG. 4. The sleeve retaining bushing 20 may have internal threads 21 to engage external threads on the locking nut 22, thereby combining the sleeve retaining bushing, retaining washer, and locking nut functions into one piece.

Description of the Third Embodiment

[0046] Refer to FIG. 5. The sleeve retaining bushing 23 used on the primary end of the mandrel (end nearest to the high pressure fluid source) may have internal threads 24 to match the threads on the mandrel shaft 1. It may have a major OD machined equal to or larger than the cylinder being expanded to facilitate precise positioning of the mandrel assembly, by indexing it off the end of the cylinder to be expanded. Thereby combining the sleeve retaining bushing, retaining washer, locking nut, and positioning collar functions into one piece.

[0047] Variations or modifications to the subject matter of this invention may occur to those skilled in the art upon review of the summary of the invention as provided herein, and upon undertaking a study of the description of its preferred embodiment, in view of the drawings. The subject matter of this invention as explained, is set forth for illustrative purposes only.