Abstract:
A heat shield surrounds an exhaust tail pipe of an internal combustion engine so as to define a certain thickness of an insulating layer of air between the shield and the tail pipe.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to a heat shielding apparatus for an exhaust tube of an internal combustion engine vehicle and particularly to the apparatus for the exhaust tube arranged beneath a body portion of the vehicle. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a new heat shielding apparatus which is fixed around an exhaust tube of an internal combustion engine for effectively shielding heat radiation from the exhaust tube when the engine is running. 
     It is another object of the present invention to provide the apparatus which can prevent direct contact of inflammable such as dry grass on the road surface with the hot exhaust tube. 
     It is another object of the present invention to provide the apparatus which comprises a heat shielding cylindrical plate concentrically positioned and radially spaced apart from the exhaust tube by spacing means. 
     It is still another object of the present invention to provide an improved arrangement of the heat shielding apparatus to the exhaust tube, in which longitudinal thermal expansion occurring in the exhaust tube hardly effects the mechanical properties of the heat shielding apparatus. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects and advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, wherein; 
     FIG. 1A is a perspective view of elementary parts of a heat shielding apparatus of a first preferred embodiment, accompanying an exhaust tube, according to the present invention; 
     FIG. 1B is a perspective view of an assembled shielding apparatus of the first preferred embodiment; 
     FIG. 1C is a sectional view taken along line I--I of FIG. 1B; 
     FIGS. 2 and 3 are perspective views showing other arrangements of the parts, with the exhaust tube, employed in the apparatus of FIG. 1A; 
     FIG. 4 is a sectional view of a slightly modified heat shielding apparatus of the first preferred embodiment; 
     FIG. 5A is a perspective view of an assemblied heat shielding apparatus of a second preferred embodiment, accompanying an exhaust tube indicated in phantom lines, according to the present invention; 
     FIGS. 5B and 5C are sectional views taken along lines II--II and III--III of FIG. 5A; 
     FIGS. 5D and 5E are sectional views taken along lines IV--IV and V--V of FIG. 5A; 
     FIG. 6A is a sectional, partial view of an assemblied heat shielding apparatus of a third preferred embodiment, accompanying an exhaust tube indicated in phantom lines, according to the present invention; and 
     FIG. 6B is a sectional view taken along line VI--VI of FIG. 6A. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to FIGS. 1A, 1B and 1C of the appended drawings, there is shown the first preferred embodiment of the invention in which a heat shielding apparatus 10 is attached to a cylindrical exhaust tube 12 leading from an internal combustion engine (not shown). 
     As best seen from FIG. 1A, the heat shielding apparatus 10 comprises a generally rectangular heat shielding plate 14 formed with a concave recess 16 along the longitudinal center line portion thereof and a pair of upwardly extending flange portions 18 at the side edges thereof. As well shown in FIG. 1C, the radius of the concave recess 16 is suitably larger than that of the exhaust tube 12 so as to provide a certain thickness of an insulating layer of air between them as will be described hereinafter. Four corners of the heat insulating plate 14 are provided with holes 14a. 
     On both longitudinal ends of the heat shielding plate 14 are mounted two spacing or bridge members 20 each of which is bent at the generally middle portion thereof toward the bottom of the concave recess 16 and is provided with two holes 20a at both ends thereof, the holes 20a being arranged to align with the corresponding holes 14a of the heat shielding plate 14. As shown in FIG. 1C, each of the spacing members 20 has a round section 20b at the bent portion thereof to firmly receive a part of the exhaust tube 12. In this embodiment, the radius of the round section 20b is the same as that of the exhaust tube 12. 
     Two bracket members 22 having raised portions 24 at the generally middle portion thereof are used for connecting the heat shielding plate 14 and the spacing members 20 to the exhaust tube 12. Each bracket member 22 is formed at both ends thereof with respective holes 22a. On both ends of each bracket member 22 are connected respective nuts 26 each of which has a hole 26a aligning with the corresponding hole 22a of the bracket members 22. 
     These parts, such as the heat shielding plate 14, the spacing members 20 and the bracket members 22 are fastened to each other while enclosing the exhaust tube 12 by means of screw bolts 28 passing through the holes 14a, 20a, 22a and 26a, as well seen in FIGS. 1B and 1C. 
     FIG. 2 shows a slightly modified arrangement of the parts of the heat shielding apparatus to the exhaust tube 12, in which each unit consisting of the spacing member 20 and the bracket member 22 is located toward the center portion of the heat insulating plate 14. 
     FIG. 3 shows still another modified arrangement of the parts, in which the spacing members 20 and the bracket members 22 are positioned alternately along the exhaust tube 12. 
     If desired, the recess provided in the heatshielding plate 14 may be formed to have a rectangular cross section 16a, as shown in FIG. 4. 
     With the above described construction of the heat shielding apparatus 10, heat developed in the exhaust tube 12 is caused to transfer to the heat shielding plate 14 mainly through the small sized spacing members 20 which can not convey heat very well. Accordingly, the heat shielding plate 14 is prevented from being heated to an extremely elevated temperature. 
     Furthermore, when the exhaust tube 12 expands by the heat of the exhaust gases, the radial expansion of the exhaust tube 12 is preferably absorbed by the round section 20b of the spacing member 20. In this case, the round section 20b is moved downwardly toward the bottom portion of the concave recesss 16. Furthermore, in this condition, the longitudinal expansion of the exhaust tube 12 is achieved without affecting the arrangement of the parts of the apparatus 10 since the apparatus 10 is constructed to slidably receive therein the exhaust tube 12. 
     Furthermore, during running of the vehicle, the space defined between the exhaust tube 12 and the concave groove 16 is well ventilated by fresh air so that the heat shielding plate 14 is cooled well. 
     FIGS. 5A and 5E show the second preferred embodiment of the present invention. 
     In this embodiment, the heat shielding apparatus 10 comprises a generally cylindrical heat shielding plate 30 which has a radius suitably larger than that of the exhaust tube 12. At both longitudinal end portions of the heat shielding plate 30 are formed with first and second groups of embossed sections 32 and 34 which are projected inwardly so as to contact with the outer surface of the exhaust tube 12. Although, in this embodiment, each group has five embossed sections, it is also possible to provide more or fewer numbers of embossed sections to the heat shielding plate 30. 
     Embossed sections 32 of the first group are firmly connected at the inwardly projecting top ends thereof to the outer surface of the exhaust tube 12 by a suitable technique such as welding, while the embossed sections 34 of the second group are arranged to slidably contact, at the top ends thereof, with the exhaust tube 12. 
     Two clamping bands 36 and 38 are employed to firmly fasten the heat shielding plate 30 to the exhaust tube 12. Each of the clamping bands 36 and 38 has both ends connectable with each other by a bolt 36a (38a) and a nut 36b (38b). It should be noted that these clamping bands are arranged about the shielding plate 30 so as to enclose the recesses defined by the embossed sections 32 and 34, as shown in FIG. 5E. 
     In the construction of this second embodiment, the heat transfer between the exhaust tube 12 and the heat shielding plate 30 is mainly made through the embossed sections which are incapable of conveying large amounts of heat by their limited contacting area to the exhaust tube 12. Therefore, the heat insulating plate 30 is prevented from being over-heated. 
     In this second embodiment, it should be noted that there is almost no chance that some inflammable material, such as dry grass on a road, accidentally contacts the extremely heated portions of the recesses defined by the first and second embossed sections 32 and 34 to burn. This is because of the fact that all recesses are enclosed by the clamping bands 36 and 38, as mentioned before. 
     It is also to be noted that, in this embodiment, the longitudinal expansion of the exhaust tube 12 does hardly affect the shielding apparatus 10 since the second group of embossed sections 34 are not firmly connected to the exhaust tube 12 but arranged to slidingly contact with the exhaust tube 12. 
     Referring to FIGS. 6A and 6B, the third preferred embodiment of the present invention is shown, in which the heat shielding apparatus 10 of the exhaust tube 12 comprises a generally cylindrical heat shielding plate 40 having along one side portion thereof a flange section 42 with a suitable number of holes 40a and along the longitudinal inner surface thereof a suitable number of embossed sections 44. The embossed sections 44 are used for contacting with the exhaust tube 12 in such a manner that the heat shielding plate 40 is positioned concentrically and spaced apart from the exhaust tube 12. 
     Several clamping bands 46, though only one band is shown, are employed for connecting the heat shielding plate 40 to the exhaust tube 12. Each clamping band 46 has both ends formed into flange sections 48 and 50 which are respectively provided with holes 48a and 50a. The flange section 50 has at its sides downwardly bent sections 51 for increasing mechanical strength thereof. 
     In assembling these parts, a screw bolt 52, a nut 54 and a washer 56 are employed so as to not only fasten the heat insulating plate 40 to the flange section 50 of the clamping band 46, but also to firmly fasten the clamping band 46 onto the exhaust tube 12. Furthermore, the inwardly projecting top end of the embossed section 44 is firmly connected to the cylindrical outer surface of the exhaust tube 12 by means of welding. 
     Although, in this third embodiment, the heat shielding plate 40 is formed with a section of decreased diameter at one longitudinal end portion thereof, it is also possible to use a plate having generally the same diameter throughout the whole length thereof. 
     With the construction of this third embodiment, the longitudinal expansion of the exhaust tube 12 due to the heat in the tube 12 is made without damaging the arrangement of the heat shielding apparatus 10 by the same reasons stated hereinbefore. 
     Although, in the previous description, the heat shielding apparatus is stated to connect to the exhaust tube 12 having a generally circular cross section, it is also possible to use this type of heat shielding apparatus with the other members of the exhaust system such as a muffler and a catalytic converter. 
     It is to be understood that the invention is not to be limited to the exact construction shown and described and that various changes and modifications may be made without departing from the scope of the invention, as defined in the appended claims.