while this invention is susceptible of embodiment in many different forms , there are shown in the drawings , and will be described herein in detail , specific embodiments thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated . fig1 shows an agricultural combine 10 comprising a supporting structure 12 having ground engaging wheels 14 extending from the supporting structure . the operation of the combine is controlled from operator &# 39 ; s cab 15 . a harvesting platform 16 is used for harvesting a crop and directing it to a feederhouse 18 . the harvested crop is directed by the feederhouse 18 to a beater 20 . the beater directs the crop upwardly through an inlet transition section 22 to the axial crop processing unit 24 . the crop processing unit 24 threshes and separates the harvested crop material . grain and chaff fall through grates on the bottom of the unit 24 to the cleaning system 26 . the cleaning system 26 removes the chaff and directs the clean grain to a clean grain elevator ( not shown ). the clean grain elevator deposits the clean grain in grain tank 28 . the clean grain in the tank 28 can be unloaded into a grain cart or truck by unloading auger 30 . threshed and separated straw is discharged from the axial crop processing unit 24 through outlet 32 to discharge beater 34 . the discharge beater 34 in turn propels the straw out the rear of the combine . as illustrated in fig2 , the axial crop processing unit 24 comprises a rotor housing 36 and a rotor 37 located inside the housing 36 . the front part of the rotor 37 and the rotor housing 36 define the infeed section 38 of the crop processing unit . longitudinally downstream from the infeed section 38 are threshing section 39 and separating section 40 . the rotor 37 comprises a drum 100 to which crop processing elements for the infeed section , threshing section , and separating section are affixed . the drum 100 comprises a rearward cylindrical portion 102 and a forwardly extending frusto - conical portion 104 . the rotor 37 shown in fig2 is similar to the rotor explained in more detail in u . s . pat . no . 7 , 070 , 498 , herein incorporated by reference . however , in contrast to the rotor shown in u . s . pat . no . 7 , 070 , 498 , the rotor 37 within the threshing section 39 includes a long tapered profile throughout the threshing section 39 without the cylindrical portion within the threshing section as described in u . s . pat . no . 7 , 070 , 498 . alternatively , the rotor could be a rotor having the shape such as shown u . s . pat . no . 5 , 688 , 170 . the invention is useful with and encompasses all of these rotors . the rotor 37 in the infeed section 38 is provided with helical infeed elements 42 located on the frusto - conical portion of the drum 100 . the helical infeed elements 42 engage harvested crop material received from the beater 20 and inlet transition section 22 . in the threshing section 39 the rotor 37 is provided with a number of threshing elements 122 for threshing the harvested crop material received from the infeed section 38 . the separating section 40 of the rotor includes outwardly projecting tines 126 similar to the tines disclosed in fig1 and 12 of u . s . pat . no . 5 , 112 , 279 , herein incorporated by reference . the threshing section 39 of the rotor housing is provided with a concave 146 and the separating section 40 is provided with a grate 148 . grain and chaff released from the crop mat falls through the concave 146 and the grate 148 . the concave and grate prevent the passage of crop material larger than grain or chaff from entering the cleaning system 26 . the rotor is axially arranged in the combine and defines a central rotor axis ra . the rotor axis ra is a straight line passing through the infeed , threshing and separating portions of the rotor . as seen in fig7 , the infeed section 38 of the rotor housing 36 is provided with a closed cover 162 and a closed bottom 164 . the cover 162 is provided with helical indexing vanes 165 . the cover and bottom are bolted to axial rails 166 and 168 . the forward portion of the closed bottom 164 is provided with an inlet transition section which is similar to one of those disclosed in u . s . pat . nos . 7 , 070 , 498 or 5 , 344 , 367 , herein incorporated by reference . the closed cover 162 of the infeed section 38 defines an infeed axis ia . the infeed axis ia is parallel to and substantially collinear with the rotor axis ra defined by the rotor . as such , the infeed portion of the rotor is substantially concentrically arranged in the infeed section 38 of the rotor housing as defined by the cover 162 . as seen in fig8 , the threshing section 39 is provided with a closed threshing cover 172 having helical vanes 174 . the cover is bolted to axial rails 166 and 168 . the concave 146 is pivotally mounted to the frame of the combine below rail 168 at 175 . an adjustment assembly 176 for adjusting concave clearance is mounted to the frame of the combine below rail 166 . the concave 146 is provided with a closed extension 178 . the threshing cover 172 defines a threshing axis ta that is parallel to the rotor axis ra . the threshing axis is located above the rotor axis ra . in addition , the threshing axis is slightly offset to the side of the rotor axis in a downstream direction . as such , the cover of the threshing section is eccentrically arranged relative to the threshing portion of the rotor . the separating section 40 is provided with a separating cover 180 having helical vanes 182 . the cover is bolted to axial rails 166 and 168 . grate 148 is also bolted to rails 166 and 168 . grate 148 is similar to the grate disclosed in u . s . pat . no . 4 , 875 , 891 . the separating cover 180 defines a separating axis sa that is parallel to the rotor axis ra . the separating axis is located above the rotor axis ra . in addition , the separating axis is offset to the side of the rotor axis in a downstream direction . as such , the cover of the separating section is eccentrically arranged relative to the separating portion of the rotor . according to the preferred embodiment of the present invention , a frusto - conical transition section 200 is provided between the threshing section 39 and the separating section 40 , overlapping each section . the transition section 200 includes a cover 210 having a substantially frusto - conical curvature . the cover 210 includes vanes 214 a , 214 b . the vane 214 a has a relatively wide width similar to the vanes 174 of the threshing section 39 . the vane 214 a is substantially continuous with the last vane 182 a of the separating section 40 . the vane 214 b has a relatively wide width section 214 c similar to the width of the vane 174 of the threshing section 39 , and a relatively thinner width section 214 d similar to the width of the vane 182 of the separating section 40 . preferably , for smooth , energy - efficient flow , the cover 210 has a taper angle “ g ” that is substantially equal to a taper angle “ h ” of the rotor drum 100 within the threshing section 39 for the rotor shown in fig2 . some rotors provided a further , reverse taper portion 220 of the rotor drum 100 at an outlet end of the processing unit 24 having an angle of taper “ j .” a deflecting plate 180 a in the separator cover 180 can be arranged over the reverse taper portion 220 to provide for a smooth , energy - efficient flow of crop material . preferably the deflecting plate taper angle “ k ” is preferably substantially equal to the rotor angle “ j .” the rotor 37 a shown in fig2 a is substantially the same rotor in u . s . pat . no . 7 , 070 , 498 . the rotor 37 b shown in fig2 b such as shown u . s . pat . no . 5 , 688 , 170 . as can be seen in these diagrammatic side views of fig2 , 2 a and 2 b , the transition section 200 of the housing 36 allows for a smooth flow transition and a gradually increasing radial distance “ d ” between the top of the housing cover 210 and the rotor axis from the inlet of the transition section 200 to the outlet of the transition section 200 . also , for fig2 a and 2b there is a gap “ p ”, taken between the rotor and the top of the housing cover 210 from the inlet to the outlet of the transition section 200 that gradually increases within the threshing section and within the separating section . from the foregoing , it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention . it is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred .
a threshing and separating mechanism for a combine includes an elongated rotor mounted for rotation about a rotor axis on the combine within a rotor housing . the rotor has a threshing portion and a separating portion . the housing has a threshing section and a separating section corresponding to the threshing portion and the separating portion . the housing surrounds the rotor and is spaced from the rotor to form an annular space between the rotor and the housing for crop material to flow through in an axial crop flow direction from an inlet end of the housing to an outlet end of the housing . the housing includes a smooth transition section between the threshing section and the separating section of the housing .