Abstract:
A longitudinal stringer type exhaust flex pipe assembly is provided having two end pieces and multiple interlaced interlocking longitudinal stringer elements forming a flexible cylinder. Every other longitudinal stringer element is affixed to each end piece, such that each stringer element is affixed to only one end piece. The stringer elements each have a male and a female interlocking feature that allows them to slide freely between each other while maintaining a relatively airtight seal. This provides a flex pipe assembly that is compliant in the compression, extension, axial bending, and torsional directions. It is emphasized that this abstract is provided to comply with the rules requiring an abstract that will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. 37 CFR 1.72(b).

Description:
BRIEF DESCRIPTION OF THE DRAWINGS 
       [0001]    FIG.  1 —Vehicle having an engine and an exhaust system incorporating a flex pipe. 
         [0002]    FIG.  2 —Vehicle chassis and engine with an exhaust system and a flex pipe showing relative movement between the engine and chassis. 
         [0003]    FIG.  3 —Prior art bellows type flex pipe. 
         [0004]    FIG.  4 —Prior art coil type flex pipe. 
         [0005]    FIG.  5 —Longitudinal stringer type flex pipe assembly embodiment of the present invention. 
         [0006]    FIG.  6 —Section view of longitudinal stringer type flex pipe assembly embodiment of the present invention. 
         [0007]    FIG.  7 —Individual longitudinal stringer. 
         [0008]    FIG.  8 —Isometric view of longitudinal stringer type flex pipe end piece. 
         [0009]    FIG.  9 —Section view of longitudinal stringer type flex pipe end piece. 
         [0010]    FIG.  10 —Section view of portion of longitudinal stringer type flex pipe assembly. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0011]    It is often necessary in the manufacture of a vehicle having an engine subject to vibrations and movement relative to the chassis of the vehicle to provide an exhaust flex pipe between the exhaust outlet of the engine and the remainder of the exhaust system. It is advantageous to make this exhaust flex pipe as compliant as possible in compression, extension, axial bending, and torsion. 
         [0012]      FIG. 1  shows a vehicle  101  having an engine  102 , a chassis  103 , and a body  104 . The engine  102  is connected to an exhaust system  105 , by means of which exhaust system  105  exhaust generated by the engine  102  is conveyed safely away from occupants of the vehicle  101 . Due to relative movement between the engine  102 , the chassis  103 , and the exhaust system  105 , an exhaust flex pipe  106  is provided, typically at a location near the engine  102 . 
         [0013]      FIG. 2  shows an engine  102  in a chassis  103 . The engine  102  is again connected to an exhaust system  105 , which exhaust system  105  is provided with an exhaust flex pipe  106 . Vertical motion and rocking motion of the engine  102  relative to the chassis  103  and exhaust system  105  is represented graphically in  FIG. 2 . The exhaust flex pipe  106  is provided to accommodate this relative motion. 
         [0014]      FIG. 3  shows a prior art bellows type exhaust flex pipe  107 . The prior art bellows type exhaust flex pipe  107  is provided with multiple bellows  109  and two clamping sections  108 , and is shown partially cut away, such that some of the multiple bellows  109  may be seen in cross section. The multiple bellows  109  allow for a certain amount of longitudinal extension, compression, and axial bending of the prior art bellows type exhaust flex pipe  107 . Detrimentally to the performance of the prior art bellows type exhaust flex pipe  107 , the multiple bellows  109  are only minimally torsionally compliant. 
         [0015]      FIG. 4  shows a prior art coil type exhaust flex pipe  110 . The prior art coil type exhaust flex pipe  110  is formed from at least one continuous strip of flexible sheet metal formed into interlocking coils  111 . The flexible interlocking formed sheet metal coils  111  are crimped one to the next such that the sliding crimped joints  112  are able to compress and extend longitudinally, and slide tangentially. In order to prevent leaks, the sliding crimped joints  112  have to be crimped tightly, yet not tightly enough to prevent relative motion. Because of this, and because of the high ratio of width to length of the surfaces that are in sliding contact  113  within the sliding crimped joints  112 , the overall compliance of the prior art coil type exhaust flex pipe  110  to axial bending or longitudinal extension or compression is limited. This is particularly true at relatively high frequencies, such as those that occur as a result of relative movement and vibration of the engine  102  (not shown). The problem is compounded when the gaps  114  between the sliding crimped joints  112  and the flexible interlocking formed sheet metal coils  111  become filled with carbon soot from the engine  102  (not shown). 
         [0016]      FIG. 5  shows a longitudinal stringer type exhaust flex pipe assembly  200 . Interlocking longitudinal stringer elements  201  are interlaced to form a flexible cylinder  207 . The ends of the interlocking longitudinal stringer elements  201  are inserted into annular cavities  203  (not visible) in longitudinal stringer type exhaust flex pipe end pieces  202 . Alternating ends of the interlocking longitudinal stringer elements  201  are retained by a snap ring, bonded, keyed, welded, pinned, crimped, or otherwise affixed within the annular cavities  203  of each longitudinal stringer type exhaust flex pipe end piece  202 . Each longitudinal stringer type exhaust flex pipe end piece  202  is provided with an exhaust passage  215  and an exhaust pipe attachment surface  204 , and may also be provided with features such as an exhaust pipe retaining bead  205  or an exhaust pipe insertion stop  206 . Two section planes, Section Plane A and Section Plane B, are illustrated for reference in subsequent figures. 
         [0017]      FIG. 6  shows a section view of the longitudinal stringer type exhaust flex pipe assembly  200  taken through Section Plane A as shown in  FIG. 5 . Interlocking longitudinal stringer elements  201  are interlocked one to the next in a circular arrangement, thereby forming a flexible cylinder  207 . Each of the interlocking longitudinal stringer elements  201  are provided with an interlocking longitudinal stringer element outer convex surface  208 , an interlocking longitudinal stringer element inner concave surface  209 , a male interlocking feature  210 , a female interlocking feature  211 , and mating sealing surfaces  212 . The male interlocking features  210  and the female interlocking features  211  are such that the interlocking longitudinal stringer elements  201  are able to slide freely in the longitudinal direction. Interlocking longitudinal stringer elements  201  having alternate shapes may be used. In the same way, male interlocking features  210  and female interlocking features  211  of alternate design may be used. Thirty-two interlocking longitudinal stringer elements  201  are shown for the sake of illustration, though the actual number used may vary. A greater number of interlocking longitudinal stringer elements  201  would be advantageous to the flexibility of the longitudinal stringer type exhaust flex pipe assembly  200 , due to the decreased lateral bending moment of the narrower interlocking longitudinal stringer elements  201 . 
         [0018]      FIG. 7  shows an individual interlocking longitudinal stringer element  201  in a somewhat foreshortened view. The individual interlocking longitudinal stringer element  201  is again provided with an interlocking longitudinal stringer element outer convex surface  208 , an interlocking longitudinal stringer element inner concave surface  209 , a male interlocking feature  210 , a female interlocking feature  211 , and mating sealing surfaces  212 . The individual interlocking longitudinal stringer element  201  may be further provided with an interlocking longitudinal stringer element retaining feature  213 , such as a snap-ring groove as shown, or a hole for a roll-pin. 
         [0019]      FIG. 8  shows an isometric view of a longitudinal stringer type exhaust flex pipe end piece  202 . The longitudinal stringer type exhaust flex pipe end piece  202  is generally tubular to accommodate the passage of exhaust. It has an annular cavity  203  separated from the exhaust passage  215  by an inner reinforcement sleeve  214 . The longitudinal stringer type exhaust flex pipe end piece  202  is also provided with an exhaust pipe attachment surface  204 . A section plane, Section Plane C, is illustrated for reference in subsequent figures. 
         [0020]      FIG. 9  shows a section view of a longitudinal stringer type exhaust flex pipe end piece  202  taken through Section Plane C as shown in  FIG. 8 . The longitudinal stringer type exhaust flex pipe end piece  202  is again generally tubular, having an exhaust passage  215 . An annular cavity  203  is separated from the exhaust passage  215  by an inner reinforcement sleeve  214 , which annular cavity  203  is intended to receive the flexible cylinder  207  (not shown) comprised of interlocking longitudinal stringer elements  201  (not shown). Near the bottom of the annular cavity  203  is an end piece longitudinal stringer retaining feature  216 . The end piece longitudinal stringer retaining feature  216  is shown in  FIG. 9  as a snap-ring groove, but it could take the form of a series of holes for roll-pins, a keyway, or other such retaining feature. The longitudinal stringer type exhaust flex pipe end piece  202  is again provided with an exhaust pipe attachment surface  204 , and may be provided an exhaust pipe retaining bead  205  or an exhaust pipe insertion stop  206 . 
         [0021]      FIG. 10  shows a section view of a portion of a longitudinal stringer type exhaust flex pipe assembly  200  taken through Section Plane B as shown in  FIG. 5 . Only one of the two longitudinal stringer type exhaust flex pipe end pieces  202  is shown, which longitudinal stringer type exhaust flex pipe end piece  202  is again provided with an exhaust pipe attachment surface  204 , an exhaust pipe retaining bead  205 , and an insertion stop  206 . The flexible cylinder  207 , formed from multiple interlocking longitudinal stringer elements  201 , is inserted into the annular cavity  203  of the longitudinal stringer type exhaust flex pipe end piece  202 . Every other interlocking longitudinal stringer element  201  is possessed of an interlocking longitudinal stringer element retaining feature  213  at the end nearest the longitudinal stringer type exhaust flex pipe end piece  202  shown. These interlocking longitudinal stringer element retaining features  213  are engaged to a snap ring  217 , which snap ring  217  is in turn engaged to the end piece longitudinal stringer retaining feature  216 . The alternate interlocking longitudinal stringer elements  201  are possessed of interlocking longitudinal stringer element retaining features  213  at their far ends, such that they engage to a snap ring  217  and end piece longitudinal stringer retaining feature  216  in the other longitudinal stringer type exhaust flex pipe end piece  202  (not shown). The interlocking longitudinal stringer element inner concave surface  209  of each interlocking longitudinal stringer element  201  is of the same curvature as the outer surface of the inner reinforcement sleeve  214 . In the same way, the interlocking longitudinal stringer element outer convex surface  208  of each interlocking longitudinal stringer element  201  is of the same curvature as the inner surface of the outer wall of the annular cavity  203 . In this way, and due to the mating sealing surfaces  212  and the tight fit of the male interlocking feature  210  and female interlocking feature  211  of the interlocking longitudinal stringer elements  201  (see  FIG. 6 ), the air tightness of the exhaust passage  215  is preserved. Alternate contours of the outer surface and the inner surface of the interlocking longitudinal stringer elements  201  may be used, such as both inner surface and outer surface being flat, or both inner surface and outer surface being convex, provided that mating contours upon the inner reinforcement sleeve  214  and upon the inner surface of the outer wall of the annular cavity  203  are provided. Such a configuration may even be advantageous, as it may prevent overall rotation of the flexible cylinder  207  within the annular cavities  203  of the longitudinal stringer type exhaust flex pipe end pieces  202 . The inner reinforcement sleeve  214  may also have a slight inwards taper near its end towards the interlocking longitudinal stringer elements  201  in order to provide stress relief. In the same way, the longitudinal stringer type exhaust flex pipe end piece  202  itself may be slightly belled outward near its end towards the interlocking longitudinal stringer elements  201 , in order to provide stress relief. Because of the low ratio of width to length of the surfaces that are in sliding contact, and because there are no gaps to fill with carbon soot from the engine  102  (not shown), the interlaced interlocking longitudinal stringer elements  201  are able to slide easily relative to one another. The result of this is that the longitudinal stringer type exhaust flex pipe assembly  200  is compliant in compression, extension, axial bending, torsion, and translation. 
         [0022]    While specific embodiments have been described in detail in the foregoing detailed description and illustrated in the accompanying drawings, those with ordinary skill in the art will appreciate that various permutations of the invention are possible without departing from the teachings disclosed herein. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention, which is to be given the full breadth of the appended claims and any and all equivalents thereof. Other advantages to a vehicle equipped with a longitudinal stringer type exhaust flex pipe assembly may also be inherent in the invention, without having been described above.