Patent Publication Number: US-3874366-A

Title: Exhaust manifold for asphalt concrete heating apparatus

Description:
United States Patent n91 Cutler 1 1 EXHAUST MANIFOLD FOR ASPHALT CONCRETE HEATING APPARATUS [75] Inventor: Earl F. Cutler, Lawrence, Kans.  
 [73] Assignee: Cutler Repaving Associates,  
 Incorporated, Lawrence, Kans.  
 1221 Filed: July 2,1973 21 App1.No.:375,632  
 [52] US. Cl. l26/27l.2 A, 404/95 [51] Int. Cl. F23c 5/00 {58] Field of Search. 404/95; 126/2712 A, 271.2 R, 126/2712 C [56] References Cited UNITED STATES PATENTS 1,458,070 6/1923 Long ct a1 126/2712 A X 1,571,883 2/1926 Belanger 126/2712 A 3.311.104 3/1967 Wollner ct a1. 126/2712 A X 3,382,864 5/1968 Fannin et a1 126/2712 A 3,809,060 5/1974 Shirley ct a1. 126/2712 C FORElGN PATENTS OR APPLICATIONS 978,382 12/1964 United Kingdom .1 126/2712 Primary Examiner-William F. O&#39;Dea Assistant Examiner-P. D. Ferguson Attorney. Agent, or Firm-Olson, Trexler. Wolters, Bushnell &amp; Fosse, Ltd.  
 [451 Apr. 1,1975  
 [57] ABSTRACT The embodiment of the invention disclosed herein is directed to equipment for heating the upper strata of asphalt concrete pavement. The equipment includes a chamber having a chamber-forming wall including a roof adapted to overlie an area of the pavement to be heated, and wherein the chamber-forming walls provide downwardly extending peripheral side portions having lower edges adapted to be closely spaced from the pavement. Heater means are positioned within the chamber so formed for heating the pavement therebeneath. A horizontally disposed exhaust manifold unit is secured to each side of the roof of the heating chamber and directed forwardly of the chamber. The exhaust outlet opening of the exhaust manifold is located at the forward portion of the chamber and includes a downwardly directed outwardly flaring portion through which the hot gases emanating from the exhaust manifold are directed to the surface of the asphalt concrete pavement in front of the heating unit to preheat the pavement. The outwardly directed flaring configuration of each of the exhaust manifolds provide means for preheating the edge most portion of the area beneath the chamber.  
 13 Claims, 5 Drawing Figures PATENTED I975 SHEET 2 8F 3 mm k EXHAUST MANIFOLD FOR ASPHALT CONCRETE HEATING APPARATUS BACKGROUND OF THE lNVENTlON This invention relates generally to equipment for heating the upper strata of asphalt concrete pavement of roadways. or the like. and more particularly to an improved exhaust manifold structure used in conjunction with such heating apparatus.  
  This invention deals with substantial improvements in my earlier filed copending application Ser. No. 119.404. filed Mar. 30. 197] the entire subject matter of which is included herein by reference to the extent needed for a complete teaching of road resurfacing equipment. Also. road resurfacing apparatus as set forth in my US. Pat. No. 3.361.042 teaches an apparatus for quickly and inexpensively resurfacing roadways made of asphalt concrete materials or the like. and the information in this patent. to the extent needed for a complete teaching of this application. is herein included by reference. The size of the apparatus for re surfacing roadways may be in the order of about 8 to 12 feet wide and in the order of about 40 to St) feet long. and move along the roadway at a relatively slow rate so that during a single continuous pass over the surface of the roadway. the old road surface in front of the repaving apparatus is excavated and converted to a refinished road surface at the rear of the resurfacing apparatus. A distinct advantage of repaving apparatus ofthis type is that the finished repaved strip of roadway is substantially immediately available for vehicular traffic thereby minimiving the amount of time during which the roadway is unusable.  
  The heater apparatus of this invention is advantageously used in road repaving machinery which performs the following functions during the repaying process. First. the road surface is heated to an elevated temperature by a non-oxidizing environmentconsisting substantially of all radiant heat so that heat penetration of the asphalt is obtained to a depth of one inch or more below the surface. This is followed by a scarifying operation which deeply excavates the asphalt surface and dislodges the material heated by the first step. Then a piling operation may be performed to pile the disarranged asphalt material for maximum surface exposure so it can he further heated by a second heating operation. this heating being also substantially entirely of radiant heat. Then. if needed. a quantity of asphalt material as well as minor amounts of conventional tack coat may be applied to help weld the total hot top mixture of the asphalt to the substrate from which the heated material was removed. This is followed by a tamping and screeding which. in turn. is followed by a compacting by conventional roller means. which may be part of the entire apparatus. or which may be a sepa rate unit following the apparatus.  
  Furthermore. it will be understood that the radiant heating units themselves may be formed as part of an attachment for a tractor or truck to be transported to a particular locality whereat minor road repairs are to be made.  
  He retofore. heating apparatus of this particular characteristic included upwardly standing tubular exhaust stacks through which the hot gases and products of combustion are discharged from the heating chamber. While working on roadways in open areas where there are no trees or other objects. such as telephone or power lines. extending over the road surface. there is no apparent danger that can be encountered as a result of these hot gases. However. when utilizing the heating equipment of this type in areas where relatively low overhanging trees extend immediately over the roadway. and where other objects such as telephone and power lines extend over the roadway. these hot gases from the upstanding exhaust stacks cause burning of the leaves on the tree. as well as burning or charring of the insulation on the electrical wires extending over the roadway.  
 SUMMARY OF THE INVENTION Accordingly. it is among the objects of this invention to provide a new and improved heating apparatus for use in road repaving machines as described above wherein the hot exhaust gases from a heating chamber are transferred through a horizontally disposed exhaust manifold unit to emanate from an exhaust opening of the manifold in a downwardly direction in front of the heating apparatus to function as a preheating device.  
  It is another object of this invention to provide a new and improved heating apparatus wherein the heating units of this invention can be utilized in areas where low overhanging branches of trees as well as overhead power lines are not effected by hot exhaust gases from upstanding exhaust stacks.  
  Briefly. the heating apparatus of this invention is formed of a chamber having chamber-forming walls in&#39; cluding a roof adapted to overlie the area of the pane ment to be heated. The chamber-forming walls include downwardly extending peripheral side portions having lower edges thereof adapted to be closely spaced from the pavement so as to substantially completely prevent heat within the heating chamber from coming outwardly of the chamber. and to substantially prevent ambient atmosphere from entering the chamber. The hot gases and products of combustion formed within the chamber pass upwardly through a plurality of aligned tubes which form a conduit extending between the chamber and passing through the roof thereof. These tubes extend into a horizontally disposed exhaust manifold which includes means for providing a direction of travel of the hot gases through the manifold.  
  The manifold includes a baffle extending therealong and dividing the manifold into a cold-air passage chamher and a hot-gas passage chamber. The baffle extends from the closed end of the manifold and is directed to the open end thereof in a manner to progressively change the cross-sectional area of the two chambers. the area being a progressively increasing area from the closed end to the open end within the hot-gas chamber and a progressively decreasing area from the closed end to the open end in the cold-air passage chamber. Near the closed end of the manifold in fluid communication with the cold-air passage chamber is provided means for connection to a source of air which is under pressure. A plurality of ports provided with flutes directed angularly within the manifold from the coldair passage chamber to the hot-gas passage chamber are provided so that cold air flow occurs into the hot-gas passage chamber in the direction from the closed end of the manifold to the open end of the manifold. This then provides a means by which the inherent tendencies for hot gases to go in an upward direction can be conveyed to a horizontal direction along the extent of the exhaust manifold and directed outwardly and downwardly through a turned flared exhaust opening at the front of the heating chamber.  
  In accordance with the principles of this invention there are provided two such horizontally disposed exhaust heating manifolds. one on each side of the heat ing chamber. and extending forwardly thereof. Each of the exhaust manifolds is provided with a downwardly turned outwardly flared exhaust opening so that the asphalt concrete pavement immediately in front of and beneath the heating chamber is preheated to a lateral extent to insure proper heating at the edge most portions of the asphalt concrete pavement under the chamber.  
  Many other objects, features, and advantages of this invention will be more fully realized and understood from the following detailed description when taken in conjunction with the accompanying drawings wherein like reference numbcrals throughout the various views of the drawings are intended to designate similar elements or components.  
 BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is aside elevational view of a road resurfacing apparatus utilizing the heating apparatus wherein horizontally disposed exhaust manifolds are used in accordance with the principles of this invention;  
  FIG. 2 is a fragmentary perspective view illustrating the position of the horizontally disposed exhaust manifold located on just one side of the heating apparatus, it being understood that a second manifold is located at the other lateral extremity of the heating chamber;  
  FIG. 3 is a top view of the heating apparatus of this invention utilizing the new and improved exhaust manifold configuration. here two exhaust manifolds are illustrated. one on each side of the heating chamber unit:  
  FIG. 4 is a side elcvational sectional view of a heating apparatus of this invention wherein the new and improved horizontally disposed exhaust heating manifold is utilized; and  
  FIG. 5 is a fragmentary sectional view taken along line 55 of FIG. 4 illustrating the general configuration of the conduit tubings communicating between the heating chamber and the horizontally disposed exhaust manifold DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT Referring now to FIG. I there is seen a side view of a road resurfacing apparatus wherein the new and improved structural arrangements of this invention are utilized. this road resurfacing apparatus being here designated generally by reference numeral I0. The road resurfacing apparatus It] utilizes a plurality of large pneumatic tires or wheels [3 having sufficient surface area in contact with the roadway so that the entire weight of the apparatus is distributed uniformly over a relatively large area. thereby reducing the load per unit area of the resurfacing equipment. As the road resurfacing equipment It] moves forward over a damaged road surface. the front end of the machine will heat and dig up the road surface to a depth of approximately one or two inches. more or less. The quantity of old road surface now forming loose pavement is additionally heated so that it becomes substantially compressable under the weight of the roller action. Additional quantities of asphalt material may be supplied as desired to build up the road surface to a previous height. or to a height greater than the old road surface. The rate of travel of the machine may be in the order of about 8 to 25 feet per minute. thereby providing a completely reconstructed road surface upon which vehicle traffic can commence substantially immediately after the road surface has been formed.  
  A quantity of new material 14 is delivered. via a truck. or the like. 16. into a hopper or receptacle [7 at the front end of the machine. A conveyor 18 formed along the top portion of the frame structure transports this material from the hopper to one or more of various work stations. A control station I9 is located substantially intermediate the machine. and an operator. not shown. is positioned at this control station to control the direction oftravel. as well as the rate of travel of the machine. Furthermore. the operator located at station 19 controls various functions of the apparatus such as the amount of heat supplied to the road surface by the various road heating burners associated therewith.  
  One or more diesel engines 20 are provided at the rear portion of the machine and include various control panels 20a which operate hydraulic pumps or compressors. The particular structural configuration of the road repaving apparatus I0 illustrated herein provides that the wheels I3 be motorized by independent hydraulic motors which are operated by the hydrostatic hydraulic supply pumps energized by the diesel engine 20. While this particular type of motive power is preferred. it will be understood that other types of motive power may be utilized without departing from the novel aspects of this invention.  
  A plurality of fuel tanks 2I are mounted on top of the support frame 22 of the machine and are used to carry large quantities of fuel for both the diesel engine 20 and for a pair of spaced apart heating units 24 and 26. One or more of the fuel tanks 21 may be filled with diesel fuel while one or more of the fuel tanks may be filled with pentane fuel for operating the burners associated with the heating units 24 and 26. The pair of road surfacing heating units 24 and 26 are spaced sufficiently apart so that the heated road surface thcrebetwecn can be dug up and rearranged for additional heating of the dislodged components of the road surface. Therefore. the heating apparatus 24 initially heats the road surface to a depth of about one or two inches and the space between the heating units 24 and 26 provides scarifying means for digging up the road surface. The subsequent heating is then accomplished by the second burner 26. The manner in which the road resurfacing apparatus 10 operates is more fully disclosed in my US. Pat. No. 3.361.042. and no further detailed description of operation is deemed necessary herein.  
  The pair of heating units 24 and 26. each are constructed substantially identically. and therefore. only a single heating unit will be discussed in great detail. Therefore. referring now to FIG. 2 there is seen a fragmentary perspective view of the heating unit 24 wherein the chamber-forming walls 30 thereof include a plurality of downwardly directed side members 3] and 32 and a roof portion 33. It will be seen that the downwardly directed sides 3] and 32 are fabricated of reinforced sheet material to form a strong structure. and one which can withstand substantial amounts of heatv Mounted on top of the roof 33 is an air fuel mixture distribution chamber 34 which is in fluid communication with a pair of diametrically opposed longitudinal input manifold members 36 and 37. as best seen in FIG. 3. l&#39;he main input manifold sections 36 and 37 feed a plurality of transverse feed manifolds, here being collectively designated by reference numerals 36a and 3711 as best seen in FIG. 3. Located at strategic points along each of the transverse manifold members 360 and 37a is a discrete heating unit 39 which extends downwardly within a heating chamber 40. as best seen in FIGS. 4 and S.  
  In the embodiment disclosed herein the heating units 39 each are provided with a radiant heating element 41. which preferably are formed of an lnconel material which is a nickel base, heat-and-oxidization-resistant material having approximately 13% chromium. 6% iron. and small amounts of manganese. silicon. and copper. However, it will be understood that other radiant heating element material may be utilized in the heating apparatus of this invention.  
  The air fuel mixture from the chamber 34 is delivered laterally to the longitudinal chamber 36, and therefrom through openings 42 into mating openings 43 to feed the air fuel mixture into the transversely disposed distributing channels 36a and 37a. The communication between the chamber 34 and the chambers 36 and 37 is achieved through a side opening such as the opening 44 communicating the chambers 34 and 36. The chamber 34 is supplied with an airfuel mixture inlet which is coupled to the air-fuel supply by suitable Ilange means as seen in FIG. 3. Located within the heating chamber is an upper and peripheral liner member 46 which may be formed of refractory ceramic material to aid in producing radiant heating to be directed downwardly from the heating chamber onto the surface of pavement 12 being treated.  
  Referring once again to FIGS. l and 2 the beating apparatus 24 and 26 are provided with horizontally disposed exhaust manifold members 50 and SI. While only a single exhaust manifold member is illustrated in FIGS. 1 and 2. it can be seen that FIG. 3 illustrates that each of the heating chambers of this invention are provided with a pair of spaced apart exhaust manifolds extending forwardly of the heating chamber and positioned near the side or lateral periphery thereof.  
  In FIG. 3. the exhaust manifold 50 is separately designated by reference numerals 50a and 50b. Most advantageously. the configuration and orientation ofthe horizontally disposed exhaust manifold members 50a and 50): provide means for conducting the exhaust gases and products of combustion forwardly of the heating chamber and dispensing these heated gases onto the surface of the pavement being treated. This is best seen in FIG. 4 which illustrates that the direction of travel of the hot gases and products of combustion are upwardly. as indicated by the arrowcd lilies. through aperture means such as a plurality of spaced apart aligned tube members 52. These hot gases then enter the exhaust manifold 50. by entering a hot-gas passage chamber 54. The manifold St) is divided into two passages. the hot-gas passage chamber 54 and a forccd air passage chamber 56 which. in turn. communicates with the hot-gas passage chamber 54 by means of a plurality of angularly downwardly disposed flute members 58 formed in a baflle member 53. These downwardly disposed flute members provide air flow in the direction from the closed end 60 of the manifold 50 toward the exhaust outlet end 62.  
  Forced air is delivered to the manifold 50 by means of an inlet port 64. which may be connected to any suit&#39; able supply of forced air. as for example. a squirrel cage blower. or the like. The forced air travels through the air passage chamber 56 and enters the hot-gas passage chamber 46 gradually as a result of the narrowing action provided by the baffle member 53.  
  The horizontally disposed exhaust manifold members 50 have downwardly turned. outwardly flared end portions 66 which lead into the exhaust outlet openings 62. As best seen in FIG. 2 the outwardly flared configuration ofthe horizontally disposed exhaust member Sfl is fashioned so as to project hot gases downwardly upon the road surface as close to the lateral edge of the heating apparatus as possible. This supplements heating of the entire surface area beneath the heating apparatus by preheating difficult to heat edges. Furthermore. by so dispensing the hot gases and products of combustion within the heating chamber 40 by means of the horizontally disposed exhaust heating manifold. the disadvantage of vertical exhaust stacks is substantially completely eliminated. This exhaust arrangement will in no way interfere with overhead obstacles such as branches from trees. or power lines. or the like. Therefore. not only does the unique and novel horizontal exhaust sys tem ofthis invention improve the general heating chai= acteristics of the heating apparatus by preheating the forward portion of the pavement as a heating apparatus moves in a given direction. but it also provides means for preventing damage to overhead obstacles.  
  The specific configuration of the horizontally disposed hcating apparatus is now discussed. A U-shaped elongated channel member 70 is positioned upon the roof portion 33 and in registry with a holding member 71 which. in turn, includes apertures to fit over the top portion of the tubes 52. There may be provided collar means 72 located about each of the tubes 52 to provide substantial amounts of metal for welding the structure together.  
  The top wall portion of the horizontally disposed cx haust heating member 50 is formed by a downwardly turned U-shaped member 74 which has the side por tions thereof overlapping outwardly of the upward leg portions of the U-shaped member 70. This structure can then be either secured together by a plurality of equally spaced apart rivets or screws. or it may be welded together as desired. To facilitate fabrication of the horizontally disposed exhaust manifold. the baffle member 53 is also formed as a U-shapcd member. in the cross-section. as seen in FIG. 5. and has the up wardly turned leg portions thereof secured to the inner walls of the upwardly turned leg portions of the U- shaped member 70. The baffle member can then be secured in place by rivets. screws. or welding. as desired.  
  The specific embodiment disclosed herein has the baffle member 53 oriented so that it divides the two chambers in a manner progressively changing in cross section, as best seen in FIG. 4. At the closed end 60. the chamber is divided so that the hot-gas passage 54 constitutes for a cross-sectional area in the order of about between 50% and 75%. and preferably in the order of about ril /1%. On the other hand. the cold-air passage 56 accounts for a cross-sectional area of about in the order of 25% and Sti /r. and preferably in the order of about 38 /271v Therefore. with a total height of 8 inches of the exhaust manifold the hot-gas chamber 54. at the closed end 60. will have a height of approximately 3 inches, while the cold-air passage 56 will have a height of approximately inches. On the other hand, the range of dimensions at the forward end of the horizontally disposed exhaust manifold 50. in the vicinity of the dot-dash lines 76 has the hot-gas passage chamber 54 providing a cross-sectional area constituting approxi mately tifi /r to tiS /r of the area, preferably being in the order of about 75% of the area. and the cold-air passage 56 providing a cross-sectional area of about between 157: and 35% ofthc cross-sectional area, preferably being in the order of about 259%. Therefore, with a total height of 8 inches along the extent ofthe exhaust manifold the hot-gas passage chamber 54, in the region of the vertical line 76, has a height of approximately 6 inches while the cold air passage chamber 56 has a height of about 2 inches.  
  Referring now to FIG. 3 the flared end portion 66 leading into the exhaust opening 62 is substantially 75% greater in width than the width of the horizontally disposed exhaust manifold. For example, an exhaust manifold having a width of 8 inches along the parallel side walls thereof will then have a width of approximately 14 inches at the maximum extent of the flared end 66.  
  While a single specific embodiment of this invention is here illustrated, it will be understood that a multitude of variations and modifications may be effected without departing from the spirit and scope of the novel concepts disclosed and claimed herein.  
 The invention is claimed as follows:  
  I. Equipment for heating of the upper strata of as phalt concrete pavement, or the like, comprising in combination: a heating chamber having chamberforming walls including a roof adapted to overlie an area of the pavement to be heated, said chamberforming walls including downwardly extending peripheral side portions having lower edges thereof adapted to be closely spaced to the pavement, heater means positioned within said heating chamber for heating the pavement therebeneath wherein the improvement comprises a horizontally disposed exhaust manifold means positioned over said roof and having an exhaust opening formed at one end thereof, and conduit means formed between said heating chamber and said horizontally disposed exhaust manifold, and passing through said roof, whereby hot gases formed within said chamber. as a result of the products ofcombustion produced by said heater means, pass through said conduit means to be discharged through said exhaust opening, said exhaust opening being located at an end of said horizontally disposed exhaust manifold means located adjacent a forwardmost portion of said roof and being turned downwardly in front of a frowardmost wall portion of said chamber-forming walls to direct hot gases emanating from said heating chamber onto the pavement preceding said heating chamber when moving over the asphalt concrete pavement in a for&#39; ward direction.  
  2. The equipment for heating the upper strata of asphalt concrete pavement according to claim 1, wherein said conduit means is formed of a plurality of discrete spaced apart aligned tubes extending upwardly from said chamber, through said roof and terminating within said horizontally disposed manifold means.  
  3. The equipment for heating the upper strata of asphalt concrete pavement according to claim 2. wherein said plurality ofdiscrete spaced apart aligned tubes are arranged in a direction corresponding to a forc-and-aft direction of the equipment, with regard to the direction of travel of the equipment over the pavement to be heated. said exhaust opening of said horizontally disposed exhaust manifold means being positioned adjacent the forward most portion of said roof.  
  4. The equipment for heating the upper strata of asphalt concrete pavement according to claim 2. further including gas flow direction means formed within said horizontally disposed exhaust manifold means for urging said hot gases emanating from said heating chamber in a direction from said plurality of spaced apart tubes toward said exhaust opening to provide Liniform gas flow through said horizontally disposed exhaust manifold means.  
  5. The equipment for heating the upper strata of asphalt concrete pavement according to claim 4, wherein said gas flow direction means formed within said horizontally disposed exhaust manifold means includes a baffle clement extending along the length of said horizontally disposed exhaust manifold means and extending transversely therein substantially the entire width thereof, said baffle element dividing said horizontally disposed exhaust manifold means into a cold air-flow passage and a hot gas-flow passage, said baffle element including a plurality of spaced apart flutes through which forced air passes from said cold air flow passage into said hot gas flow passage for urging the direction of air How and hot gases through said manifold toward said exhaust opening, and means connected to said hor izontally disposed exhaust manifold means for supply ing a quantity of air under pressure to said cold air flow passage.  
  6. The equipment for heating the upper strata of asphalt concrete pavement according to claim 5, wherein said baffle element extends the length of said horizontally disposed exhaust manifold and is angularly positioned therein to provide a cross-sectional area at said closed end of said hot gas flow passage which is in the order of about between IS /r and 357: the total area within the exhaust manifold, and to provide a crosssectional area of said air flow passage which is in the order of about between Sti /r and 9071 the total area within said exhaust manifold and wherein said baffle is positioned within said exhaust manifold, immediately adjacent said downwardly turned flared end, to provide a cross-sectional area of said hot gas passage which is in the order of about between and the total cross-sectional area, and to provide a cross-sectional area of said air flow passage which is in the order of about HIV! and 35% the total cross-sectional area within said exhaust manifold.  
  7. The equipment for heating the upper strata of asphalt concrete pavement according to claim I, wherein said horizontally disposed exhaust manifold means includes a pair of separate laterally spaced apart exhaust manifold units positioned on opposite sides of said roof and providing means for preheating the upper strata of the asphalt concrete pavement on both sides of said equipment preceding the direction of travel of the equipment over the pavement.  
  8. The equipment for heating the upper strata of as phalt concrete pavement according to claim 7, wherein said exhaust opening of said horizontally exposed exhaust manifolds on each side of said roof each include turned downwardly flared end portions, said turned downwardly flared end portions being directed laterally outwardly ofthe direction of travel of the equipment so as to provide preheating action of the asphalt concrete roadway in front of the equipment and sufficiently to the lateral extent thereof to insure proper heating of the entire width of the asphalt concrete pavement as the equipment passes thereover.  
  9. The equipment for heating the upper strata of asphalt concrete pavement according to claim 8, wherein said flute means formed in said baffle element are respectively positioned within said horizontally disposed exhaust manifold between selected ones of a plurality of spaced apart tubes providing said conduit means between the heating chamber and said manifold, thereby providing a contoured surface against which hot gas flow from said tubes impinge to direct hot gas flow toward said exhaust opening.  
  10. Equipment for heating asphalt concrete pavement and the like comprising a heating chamber having a roof and depending sidwalls. and exhaust manifold structure comprising in combination: an exhaust mani fold housing horizontally disposed over said roof of the heating chamber, said housing having side, top, and bottom walls, a closed end and an open end forming an outlet thereof, aperture means formed within said bottom wall, means connecting the interior of said heating chamber with said aperture means whereby hot gases to be exhausted can enter said housing and be discharged from said outlet, and gas flow directing means formed within said housing for urging said hot gases entering therein through said aperture means to flow in a direction toward said exhaust opening. said gas flow directing means including a baffle element extending along the length of said horizontally disposed exhaust manifold housing and extending transversely therein substantially the entire width thereof, said baffle dividing said housing into a cold-air flow passage and a hotgas flow passage, said baftle including a plurality of spaced apart flutes through which forced air can pass from said cold-air flow passage into said hot-gas flow passage for urging the direction of air flow and hot gases through said housing toward said exhaust opening, and means connected to said housing for supplying a quantity of air under pressure to said cold-air flow passage, whereby the hot gases entering the hot-gas flow passage through said aperture means is urged to said exhaust opening as a result of forced air passing through said flutes from said cold-air flow passage to said hot-gas flow passage.  
  II. The equipment for heating asphalt concrete pavement and the like according to claim Ill. wherein said open end outlet is turned downwardly and flared laterally to have a width at said outlet greater than the width between said side wall of said housing along the major longitudinal extent thereof.  
  [2. The equipment for heating asphalt concrete pavement and the like according to claim ll). wherein said baffle element extends the length of said housing and is angularly disposed between said closed end and said outlet to provide a cross-sectional area at said closed end of said hot-gas flow passage which is in the order of about between and the total cross sectional area within said housing, and to provide a cross-sectional area of said air-flow passage which is in the order of about between and the total area within said exhaust manifold and wherein said baftle is positioned within said housing adjacent said open end forming said outlet to provide a cross-sectional area of said hot-gas passage which is in the order of about between SO&#39;lr and 9071 the total cross-sectional area. and to provide a cross&#39;sectional area of said air-flow pas sage which is in the order of about 10% and 35% the total cross-sectional area within said housing.  
  13. The equipment for heating asphalt concrete pavement and the like according to claim 10. wherein said flute means formed in said baffle element are five in number, said flute means being positioned within said horizontally disposed housing to be located between said plurality of spaced apart aligned apertures forming said aperture means, thereby providing a contoured surface against which hot gas flow from said aligned apertures into said hot-gas flow passage toward said exhaust opening.