RUPTURE INHIBITING FLUID TRANSITION

Abstract: A fluid piping system is provided including a stepped conduit (14) having a transition portion (18) formed to define either a concaved or convexed outer surface relative to the axis (22), wherein the transition portion (18) inhibits rupturing while forces are directed upon the connection. In one embodiment, the concaved outer surface is so dimensioned as to fold over and reduce tearing while allowing the piping section to become non-concentric with the axis without rupturing.

Description: RUPTURE INHIBITING FLUID TRANSITION BACKGROUND AND SUMMARY OF THE INVENTION This invention relates to fluid piping and connector systems, and more particularly, to a fluid transition in such connector systems which inhibits rupture and does not "break" as a result of a sudden severe bending load applied to the connector system. A fluid transition, between cylindrical portions of different cross-section, can comprise a frusto-conical section or a "squared" section. Unfortunately, these sections can adversely effect pressure and not provide material to absorb bending moments. To accommodate for changes in pressure in the connector system, often the diameter of the conduit being connected is tapered or otherwise gradually reduced from a larger diameter to a smaller diameter. Many fluid piping and connector systems can be subjected to a complex combination of axial tensile forces and bending moments such that damage to portions of the fluid system may occur. The highest bending forces occur at system transitions, such as where interconnections are made (e.g., 'Tees" or elbows), or where connectors involve a rapid change in diameter, or where a rigid pipe changes to a flexible hose. The fluid connection system of an automobile involved in a car accident must not be ruptured. Accordingly, an object of this invention is provision of a low cost method of preventing rupture of a fluid system as a result of sudden severe bending. The invention is particularly applicable to certain fittings, or transitions, that involve a change in diameter from one section to another section. In accordance with this invention a "no break" fluid connector comprises a thin walled fitting of a flexible material formed to include either a concave in or a concave out transition portion between first and second longitudinally spaced cylindrical portions. The concave out transition is adapted to controllably fold over during a sudden bending moment, such as by an impact force perpendicular to the fitting axis, and augment the flexibility of the material. The portion of the transition material occurring furthest away from the center of the bend radius is placed in tension and provides material to facilitate extension, whereas the portion of the transition material occurring most proximate to the center of the bend radius is placed in compression and provides material to facilitate controlled folding, which allows for a no tear bending. The no tear bending is possible because the maximum stress subjected upon the system occurs during the fabrication of the concave in or concave out configuration. The transition herein advantageously recognizes that a tubular structure can "fold over" and progress through a series of cross-sections and configurations between a round shape and a flat ellipse or flat racetrack shape. At some point in this progression of cross- sectional shapes, portions of the transition structure, which are defined by each lateral side of the deformed cross-sectional shape, can go through a period of very high local stress. This high stress situation is avoided by the present invention in that the tubular conduit of the present invention has been pre-formed under stress conditions which are greater than those encountered by deforming the conduit. The solution herein recognizes that magnitude and the rate of this high local stress can be reduced by the material itself to a point where "folding" rather than "tearing" takes place. Advantageously, the concave transition section allows the transition to "fold" over and thus not be so sensitive to rupture. The embodiment which is concaved inwardly tends to yield a lower pressure drop and is therefore normally used. However, when the object is to have maximum flow after the transition portion has been subject to bending, the embodiment having the outwardly concaved transition portion is preferable. Additional objects, advantages and features of the present invention will become apparent from the following description and appended claims, taken in connection with the following drawings, in which: BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a fluid piping connection wherein the transition portion is concaved inwardly. Figures 2A-5A are side elevation views, in section, of a "no-break" pipe transition, wherein the transition portion is concaved inwardly. Figures 2B-5B are end views, respectively, of the pipe transitions shown in Figures 2A-5A Figure 6 shows the transition of a fluid piping connection wherein the transition portion has a convex bend. Figure 7 is a graph illustrating the forces in a conventional transition and in the "no break" pipe transition. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, Figure 1 illustrates a housing 10, such as for a transmission oil cooler, or a power steering gear, or an air conditioning component or the like. A pressure passage 12 sized to receive a hydraulic conduit 14 extends inwardly from the exterior of the housing. Only a portion of the conduit 14 is shown as relates to the invention herein. The conduit 14 is generally cylindrical and includes first, second and third portions 16, 18 and 20 generally coaxially disposed relative to a central axis 22. As more clearly shown with reference to Figures 2A-5A and 2B-5B, the first and third portions 16 and 20 are shown as being round with the first portion 16 having a central bore 21 and being smaller in diameter than that of the third portion 20 and received in the passageway 12 to pass fluid. The third portion 20 has a central bore 23 and is longitudinally spaced from the housing, and is thus exposed for receiving impact forces applied to the connection in a direction transverse to the axis, thereby placing bending moments on the conduit. A force, shown by the letter "F 1 , is applied to the third portion in a direction perpendicular to the axis. For discussion, the force "F" is disposed in a vertically plane that includes the axis 22, whereby a bending moment between the portions 16 and 20 will tend to deflect portion 20 vertically downwardly. In accordance with this invention, Figures 2-5 illustrate what is termed a "no break transition" for inhibiting material failure during a severe sudden bending such as would result by the impact transverse to the piping axis. The Figures illustrate the progressive stages wherein the material undergoes what is termed a "folded" over transition. In accordance with this invention, the second portion 18 is seen to define a transition that is generally concaved inwardly, as viewed externally, with each cross-section of the transition increasing in diameter as the transition portion extends longitudinally between the two cylindrical portions 16 and 20. The material is preferably flexible and capable of yielding. The conduit portions are preferably thin walled. The conduit may be formed of a plastic material having a somewhat thinner wall in the intermediate diameters located between the cylindrical portions 16 and 18 or, alternatively, may have a constant wall thickness formed of plastic or metal. It should be noted, however, that cast metals apparently do not possess sufficient elongation characteristics necessary for imparting the ability to bend which is essential to the present invention. In Figures 2A and 2B, the section 18 has not undergone deformation. In Figures 3A and 3B, the portion 18 is starting to deform slightly with an upper portion of the conduit material, shown at 24, undergoing slight extension to the right, and a lower portion of the conduit material, shown at 26, being compressed to the left. The wall is starting to fold. In the convex form of Figure 6, the bending occurs to the outside. In Figures 4A and 4B, the upper tension force causes increased longitudinal extension of upper portion 24 and the compression force causes increased folding of lower portion 26. In Figures 5A and 5B, the tension force is seen to have caused the upper portion to be nearly completely extended, and further causing the lower portion to bend in response to the compression forces. The inwardly concaved second portion 18 defines a "no break transition" because it has increased the length of material used for the upper portion, and more importantly, provides a unique shape that avoids the highest rupturing and tearing forces that would otherwise occur as a result of bending the lower portion through the configuration at high stress. The more abrupt the transition, the greater the pressure difference (i.e., pressure drop). The more concave the wall the better. Due to the inwardly concaved section, there is now a greater longitudinal length of material on the outside of the bends needed to form a smooth transition between its portions 16 and 20. This means the material on the upper part of the bend does not have to stretch as much because of the extra length of material. The pre-bent lower portion lowers to the compression force that also results in tensile force on the upper part. The concaved wall portion reduces the peak stresses that occurs when you fold or kink the tube, partly because there is more material which is available to be stretched out. The concaved shape effectively provides a pre-bend that is consistent with a configuration that the material will have to go through on its way to being kinked or folded. This pre- bent situation is past the point where the maximum stresses during folding take place. The concave circular transition shape allows the movement of the inside of the fold radius material to move toward, or away from the tubular axis without having to impose high tensile forces on the balance of the material. As a result of this concave circular shape, there is more material available on the outside of the fold radius for the final bend so that tensile forces are also reduced in this outside area. Since the compressional forces on the inside of the fold are vastly reduced, and the outside tensile force is reduced, bending of the ends of the flattened ellipse takes place somewhat more slowly and the radius (at the ends) is much larger. All of these factors tend to reduce the excessive tensile forces and compressional and flexing forces at end areas. This reduction can be sufficient to reduce these forces below the forces required for rupture, and so the "transition" just folds over in response to a loading situation that previously would have caused a rupture. As a result of this concave circular shape, the tensile forces on the balance of the material, and on the outside of the fold radius, provide more material for the final bend so that tensile forces are also reduced in this outside area. The no break transition slows down the rate of deformation by requiring a finite time for the tensile force and elongation of a material to develop to its maximum. Any time for a deformation that is shorter than this minimum time to develop the maximum in a material results in a material resisting with a small percentage of its maximum. In plastics, a longer time is required to develop the maximum tensile strength because of the long molecules of a polymer. Figure 6 shows the transition of a fluid piping connection wherein the transition portion has a convex bend 18. All other features of the conduit remain the same and are labeled with the same reference numerals. Figure 7 compares a conventional transition and the no break transition as provided by the present invention. The graph demonstrates the differences between the two forms of conduits with reference to the force on a wall segment versus the fold over transition. Not all materials will work, partly because of the wall thickness being too great, or due to material properties (e.g., elongation, tensile strength and rupture strength). Preferably and in accordance with this invention, ductile metals and yieldable polymer materials will provide the necessary collapse. Brittle materials such as cast metals do not provide the necessary collapse. While the above description constitutes the preferred embodiment of the invention, it will be appreciated that the invention is susceptible to modification, variation, and change without departing from the proper scope or fair meaning of the accompanying claims.

Claims: CLAIMS 1. A fluid conduit for passing fluid, said conduit including longitudinally spaced first, second and third portions arranged coaxially and characterized in that said second portion includes upper and lower portions and connects said first portion to said third portion, said first portion being greater in diameter than said third portion and said second portion being adapted to collapsibly yield upon a sudden severe bending moment applied to said first and third portions, wherein the portion located furthest from the center of the radius of bend of the transition portion provides material to facilitate tension forces to extend the transition material and the portion located most proximate to the center of the radius of bend of the transition providing material to facilitate compression forces to cause the transition material to fold upon itself. 2. The conduit as claimed in Claim 1, wherein the second portion forms an inwardly concaved transition portion. 3. The conduit as claimed in Claim 1, wherein the second portion forms an outwardly concaved transition portion relative to the axis of the transition. 4. The conduit as claimed in Claim 1, wherein each of the portions are thin walled and of substantially the same thickness. 5. The conduit as claimed in Claim 4, wherein the wall of transition portion is thinner than the rest of the conduit. 6. The conduit as claimed in Claim 1, wherein said material is a ductile metal. 7. The invention as claimed in Claim 1, wherein said material is formed of a polymer. 8. A fluid conduit having a transition section which includes excess material located between a first portion and a second portion, the transition section being adapted to inhibit material rupture due to a bending moment in a vertical plane through the conduit axis, said excess material allows the transition section to gradually yield in a vertical plane through the conduit axis, wherein the excess material above the axis extends longitudinally and material below the axis compresses longitudinally and folds over, thereby allowing the cross-section of the conduit to yield without the material tearing and allowing the fluid flow to continue. 9. A method of forming a fluid conduit resistant to bending moments, comprising the steps of: (a) providing a tubular starting material; (b) expanding a longitudinal portion of said tubular starting material by roll swaging the starting material; and (c) shaping the elongated portion of said tubular starting material such that the exterior surface thereof forms a generally spherical section that is concaved inwardly relative to the conduits axis. 10. The method as claimed in Claim 10, wherein said tubular starting material is comprised of a polymer. 11. A method of forming a fluid conduit resistant to bending moments, comprising the steps of: (a) providing a tubular starting material; (b) reducing a longitudinal portion of said tubular starting material by cold forming the starting material; and (c) shaping the reduced portion of said tubular starting material such that the exterior surface thereof forms a generally spherical section that is convexed outwardly relative to the conduit's axis. 12. The method as claimed in Claim 11, wherein said tubular starting material is comprised of a polymer.

Inventors: BARTHOLOMEW DONALD DEKLE, BARTHOLOMEW, DONALD, DEKLE
Applicants: BARTHOLOMEW DONALD DEKLE, PROPRIETARY TECHNOLOGY INC, PROPRIETARY TECHNOLOGY, INC.
Application year: 1992
Main classification: F16L11
IPC codes: F16L11, F16L25, F16L33, F16L37, F16L57