Abstract:
A roaster for powder and granular material capable of effectively roasting powder and granular material to the inside thereof to provide high quality powder and granular material and capable of effectively avoiding the possibility of causing contamination since the possibility of dewing is less even if the material is cooled. The roaster  1  comprises an charging port  2  in which the powder and granular material is thrown, a drum  30  in which the powder and granular material thrown from the charging port  2  is stored, and a heating unit  49  heating the powder and granular material stored in the drum  30 . A preheating chamber  3  in which the powder and granular material thrown from the charging port  2  is preliminarily heated and which communicates with the drum  30  is formed between the charging port  2  and the drum  30.

Description:
[0001]     This application is based on Japanese patent application No. 2003-318093 &amp; 2003-318095 the content of which is incorporated hereinto by reference.  
       DISCLOSURE OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a roaster for powder and granular material used for roasting powder of coffee bean, tea leaf, cereals and so forth.  
         [0004]     2. Related Art  
         [0005]     It is a general practice for manufactures of powders of coffee bean, tea leaf and so forth to roast a large amount of powder using a roaster for powder and granular material, because some kinds of the powders can add aroma and taste by being preliminarily roasted. A conventional roaster for powder and granular material will now be explained referring to, for example, a coffee bean roaster (simply referred to as a “roaster”, hereinafter) used for roasting coffee bean (or powder thereof). The roaster is roughly composed of a drum having on the top portion thereof an opening through which coffee beans (or powder thereof) are charged, a burner heating the drum from the lower side thereof, and a blade stirring the powder housed in the drum. As another example of the roaster, a tea leaf roaster used for roasting tea leaves (or powder thereof) is roughly composed of a horizontally disposed drum having on one end thereof a charging port through which the powder is charged into the drum, and having on the other end thereof a discharge section through which the roasted powder is discharged, a driving device rotating the drum, and a heating device heating the powder housed in the drum. Using these roasters, coffee beans and tea leaves (or powders thereof) are roasted by the burner and the heating device, wherein the coffee bean roaster discharges the roasted coffee beans again through the opening, and the tea leaf roaster discharges the roasted powder from the discharge section.  
         [0006]     For ideal roasting, each powder preferably has a predetermined moisture content (for example, rice bran preferably has a moisture content of less than 2% or around), whereas in the above-described conventional roasters, the powder (of coffee beans, tea leaves or the like) is charged through the opening or charging port into the drum and housed therein, and is directly roasted without being adjusted to a predetermined moisture content (low moisture content), so that every grain of the powder is often roasted in black only on the surface thereof, rather than being well roasted to the core portion, only to give aroma and taste inferior to those reasonably required for the powder. In addition, the tea leaf roaster, upon being cooled by the external air, tends to cause dewing on the surface of the drum and the blade due to moisture emitted from the powder during the roasting, which may cause contamination.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention was proposed in order to solve the problems in the above-described conventional roaster for powder and granular materials, aiming at providing a roaster for powder and granular material capable of efficiently roasting every grain of the powder to its core portion to thereby make the powder a high-quality one, and of effectively avoiding a risk of dewing, which is causative of contamination, even under cooling.  
         [0008]     The present invention was proposed in order to solve the above-described problems, wherein the first invention (described in claim  1 ) provides a roaster for powder and granular material which include a charging port through which powder is charged; a drum housing the powder charged through the charging port; and a heating unit heating the powder housed in the drum; wherein a preheating chamber which preheats the powder charged through the charging port, and communicates with the drum, is provided between the charging port and the drum.  
         [0009]     The second invention (described in claim  2 ) provides the roaster for powder and granular material described in the first invention, wherein the preheating chamber has a powder support member supporting the powder charged through the charging port, and having a large number of through-holes; a hot air supply unit supplying hot air from the lower side of the powder support member; and an exhaust unit discharging the air in the preheating chamber out into the external.  
         [0010]     The third invention (described in claim  3 ) provides the roaster for powder and granular material described in the first or second invention, wherein the hot air supplied by the hot air supply unit to the preheating chamber is an air heated by a heating unit heating the powder housed in the drum.  
         [0011]     The fourth invention (described in claim  4 ) provides the roaster for powder and granular material described in any of the first, second and third inventions, wherein the drum is supported by a plurality of rotating components in a rotative manner, all of or a part of the rotating components having a plurality of stepped portions formed thereon by which the drum is agitated.  
         [0012]     The fifth invention (described in claim  5 ) provides the roaster for powder and granular material described in the fourth invention, wherein the drum has a flange portion on the outer circumference thereof, each of the rotating components has a groove allowing the flange portion to be inserted therein, and the stepped portion is formed either on the outer circumferential surface of the flange portion or on the ring-formed outer circumferential surfaces in the groove of the rotating components on which the flange portion inserted in the groove is rolled.  
         [0013]     The sixth invention (described in claim  6 ) provides the roaster for powder and granular material described in the fourth or fifth invention, wherein the rotating components are configured by a first and a second rotating components disposed on one lower lateral side of the drum and coupled with each other through one coupling axis, and a third and fourth rotating components disposed on the other lower lateral side of the drum and coupled with each other through the other coupling axis in parallel with the one coupling axis, and the stepped portions are formed on both of the first and the second rotating components disposed ahead in the direction of movement of the powder housed in the drum caused by rotation thereof, or on both of the third and fourth rotating components.  
         [0014]     In the first invention (described in claim  1 ), there is formed a preheating chamber, which preheats the powder charged through the charging port and communicates with the drum, between the charging port and the drum, so that it is made possible to lower moisture content of the powder in the preheating chamber, and thereby every grain of the powder passed through the preheating chamber is uniformly roasted to the core in an extremely effective manner in the drum, and to avoid a result that only the surface is scorched in black. Because the moisture content in the drum is kept low even when the roaster for powder and granular material is cooled, it is also made possible to sufficiently suppress the internal dewing, and to avoid a risk of causing contamination.  
         [0015]     In the second invention (described in claim  2 ), the powder charged through the charging port and supported on the support member is heated by hot air coming through a large number of through-holes formed in the support member. In other words, the powder is heated by the hot air blowing upward from under the support member. The second invention can, therefore, preheat the powder in a costless and extremely efficient manner without using a special stirring device or driving device. Because the second invention is provided with the exhaust unit discharging the air in the preheating chamber, it is also made possible to keep a low moisture content not only in the drum but also in the preheating chamber even when the roaster for powder and granular material is cooled, and to further suppress the dewing inside the roaster for powder and granular material, and to avoid a risk of causing contamination in a more effective manner.  
         [0016]     In the third invention (described in claim  3 ), the hot air supplied to the preheating chamber by the hot air supply unit is an air heated by a heating unit heating the powder housed in the drum, and is not a heating unit provided separately from that used for heating the powder housed in the drum, so that it is made possible to effectively use energy for heating, and to reduce the running cost as compared with the conventional roaster for powder and granular material.  
         [0017]     In the fourth invention (described in claim  4 ), the drum is supported by a plurality of rotating components in a rotative manner, wherein all of, or a part of the rotating components have a plurality of stepped portions formed thereon by which the drum is agitated, so that every grain of the powder housed in the drum can uniformly be roasted over the entire surface with the aid of agitation of the drum. It is not always necessary for all of the rotating components to have the stepped portion formed thereon, and instead only a part of the rotating components may be configured as having the stepped portion by which the drum is agitated.  
         [0018]     According to the fifth invention (described in claim  5 ), it is made possible not only to uniformly roast the powder while allowing the drum to roll as the rotating components rotate so as to agitate the drum, and thereby allowing the powder housed therein to agitate, but also to rotate the drum in an extremely stable and continuous manner without causing displacement of the drum due to agitation applied by the rotating components during the rotation of the drum, because the drum is supported by the rotating components as being inserted in the groove formed on the rotating components.  
         [0019]     In the sixth invention (described in claim  6 ), the stepped portion is formed on both of the first and said second rotating components disposed ahead in the direction of movement of the powder housed in the drum caused by rotation thereof, or on both of the third and fourth rotating components, so that a portion of a powder moved from the position right under the center of the drum ahead in the direction of rotation releases from the inner circumferential surface of the drum under agitation caused by the stepped portion, and returns back to the position right under the center. In other words, according to the sixth invention, motion of the powder in the drum is just like a food (such as Chinese fried rice) cooked on a frying pan which is shaken by a cook over the fire so as to toss the food at the far end of the frying pan and to return it back to the cook&#39;s side. The sixth invention therefore makes it possible to roast every grain of the powder in a more uniform manner.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]     The above and other objects, advantages and features of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings, in which:  
         [0021]      FIG. 1  is a front view of a coffee bean roaster;  
         [0022]      FIG. 2  is a side view showing a part of the internal structure of the coffee bean roaster;  
         [0023]      FIG. 3  is a left side view of the coffee bean roaster;  
         [0024]      FIG. 4  is a left sectional side elevation of the coffee bean roaster;  
         [0025]      FIG. 5  is a plan view of the coffee bean roaster;  
         [0026]      FIG. 6  is a exploded perspective view showing a support structure of a drum;  
         [0027]      FIG. 7  is a sectional side elevation showing the support structure of the drum;  
         [0028]      FIG. 8  is a perspective view showing an axis of rotation and beaters; and  
         [0029]      FIG. 9  is a sectional side elevation showing the axis of rotation and one beater. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0030]     The invention will be now described herein with reference to illustrative embodiments. Those skilled in the art will recognize that many alternative embodiments can be accomplished using the teachings of the present invention and that the invention is not limited to the embodiments illustrated for explanatory purposes.  
         [0031]     A roaster for powder and granular material according to the first embodiment of the present invention will be detailed below, referring to the attached drawings. The roaster for powder and granular material of this embodiment is one applied form of the present invention as a coffee bean roaster (simply referred to as a “roaster”, hereinafter) roasting mill-ground powder of coffee beans.  
         [0032]     As shown in  FIG. 1 , the roster  1  has a charging port  2  through which coffee beans (powdered: the same will apply also hereinafter) are charged, and the charging port  2  communicates with the preheating chamber  3 . The charging port  2  is a portion connected to the end of a flexible pipe not shown, through which the coffee beans are introduced together with an compressed air. The charging port  2  is also molded as a pipe, and is formed on a connection member  4  to which the end of the non-illustrated flexible pipe is connected. The connection member  4  is fixed, as shown in  FIG. 1 , on the side face of a cylinder  5  having a closed top. The cylinder  5  is fixed on the right side plate  1   a  of the roaster  1 , while placing therebetween a metal attachment  6  having a down-pointing-triangle shape in the front view, and having a slide plate portion (reference numeral omitted) formed on the left surface side. The internal of the cylinder  5  and the internal of the metal attachment  6  are communicated with each other, and also the metal attachment  6  and the preheating chamber  3  are communicated. On the right side plate  1   a  of the roaster  1 , an open/close lid  7  is provided in a detachable manner as shown in  FIG. 2 , on the lower side of the position of placement of the metal attachment  6 . The open/close lid  7  has a circular see-through window  7   a  made of a transparent material such as glass, which is fixed at the center thereof, so as to allow the user to confirm whether the coffee beans are properly introduced therein or not.  
         [0033]     Inside the roaster  1 , there is provided the preheating chamber  3  so as to extend from the near-center of the roaster  1  towards the right side plate  1   a  side. The preheating chamber  3  is formed using a partition plate  9  partitioning the preheating chamber  3  from a later-described main heating chamber having a drum disposed therein; a front side partition plate  10  (see  FIG. 2  or  FIG. 4 ) having the left end thereof fixed to the partition plate  9  and the right end thereof fixed to the right side plate  1   a ; a rear side partition plate  11  disposed behind the front side partition plate  10 , having the left end thereof fixed to the partition plate  9  and the right end thereof fixed to the right side plate  1   a ; the right side plate  1   a ; and a support plate  12  on which the coffee beans are supported. The support plate  12  is a support member composing the present invention, having a shape of laterally-long rectangular plate, and is configured as a punched metal having a large number of through-holes, not shown, formed therein. The large number of through-holes formed in the support plate  12  has a diameter smaller than the diameter of the coffee beans (or powder or grain thereof) so as to prevent the coffee beans from dropping therethrough under the support plate  12 . The lower end of the front partition plate  10  is fixed to the front side end portion of the support plate  12 , and the lower end of the rear side partition plate  11  is fixed to the rear side end portion of the support plate  12 . The middle portion of the right end side of the support plate  12  is fixed to the right side plate  1   a  and further projects rightward out therefrom as shown in  FIG. 1 .  
         [0034]     On the side more closer to the front (this side) than the front of the front side partition plate  10 , there is fixed a guide plate  13  guiding, in cooperation with the partition plate  10 , the hot air to the lower side of the support plate  12 . More specifically, a hot air passageway  14  guiding the hot air to the lower side of the support plate  12 , which is composed of the front side partition plate  10  and the guide plate  13 , is formed on the front side of the preheating chamber  3 . Inside the roaster  1  and above the preheating chamber  3 , there is provided a dust collector  20  as shown in  FIG. 1 . The dust collector  20  is roughly composed of a large number of bag filters  21  and a ventilating fan  23 , and thereby the roaster  1  is configured so that the air in the preheating chamber  3  is discharged out into the air after being passed through such large number of bag filters  21 , with the aid of operation of the ventilation fan  23 . More specifically, the hot air flowing into the lower portion of the support plate  12  through the hot air passageway  14  formed by the front side partition plate  10  and the guide plate  13  further enters the preheating chamber  3  through the large number of through-holes formed in the support plate  12  (so as to be blown upward), and emitted out into the air after being passed through such large number of bag filters  21 . In this process, the coffee beans coming through the charging port  2  into the roaster  1  are supported on the top surface of the support plate  12 , and are heated by the hot air blown up from the lower side. The coffee beans (or powder or grain thereof) are trapped on the outer circumferential surface of the bag filters  21 , without being emitted outside the roaster  1 .  
         [0035]     On the left side of the portion of placement of the preheating chamber  3 , there is formed a main heating chamber  29  while placing the partition plate  9  in between, and a drum  30  is disposed in the main heating chamber  29 . The drum  30  is molded as a laterally-elongated cylinder as shown in  FIG. 6 , having both ends thereof opened. One flange portion  30   a  is formed on the outer circumference of the drum  30  at a portion set back from the left end thereof, and the other flange portion  30   b  is formed on the outer circumference at the position set back from the other end. On the left end side of the drum  30  and at a position slightly closer to the front side as viewed from the just-under position, there is disposed a first rotating component  31  supporting the drum  30 . On the right end side of the drum  30  and at a position slightly closer to the front side as viewed from the just-under position, there is disposed a second rotating component  32 . The second rotating component  32  is connected to the first rotating component  31  by a horizontal shaft  33 , and is also connected with a drive shaft  34   a  of a first drive motor  34 . On the left end side of the drum  30  and at a position slightly closer to the rear side as viewed from the just-under position, there is disposed a third rotating component  35 . On the right end side of the drum  30  and at a position slightly closer to the rear side, there is disposed a fourth rotating component  36 . The fourth rotating component  36  is connected to the third rotating component  35  by the other horizontal shaft  37  provided in parallel with one horizontal shaft  33 , and is also connected with a drive shaft  38   a  of a second drive motor  38 . The roaster  1  herein is configured so that the first drive motor  34  and the second drive motor  38  rotate in synchronization with each other. The first to fourth rotating components  31 ,  32 ,  35  and  36  have ring-formed recessed grooves  31   a ,  32   a ,  35   a  and  36   a , respectively. The drum  30  is supported by the first to fourth rotating components  31 ,  32 ,  35  and  36  in such a way that one flange portion  30   a  formed on the drum  30  is inserted into the recessed groove  31   a  formed on the first rotating component  31  and into the recessed groove  35   a  formed on the third rotating component  35 , and that the other flange portion  30   b  formed on the drum  30  is inserted into the recessed groove  32   a  formed on the second rotating component  32  and into the recessed groove  36   a  formed on the fourth rotating component  36 . Each of the ring-formed surfaces (portion in contact with each of the circumferential surfaces of one and the other flanged portions  30   a ,  30   b ), composing each of the individual recessed grooves  31   a ,  32   a  formed on each of the first rotating component  31  and the second rotating component  32 , has a plurality of stepped portions  31   b  formed thereon, as shown in  FIG. 7 . In the roaster  1  of this embodiment, the third and the fourth rotating components  35 ,  36  have no stepped portion formed thereon. The partition plate  9  has a circular opening  9   a  formed therein as shown in  FIG. 2 . The coffee beans are introduced through the opening  9   a  into the drum  30 , while being heated by the hot air blown upward from the lower side of the support plate  12  in the preheating chamber  3 . The drum  30  housing the coffee beans rotates as the first to fourth rotating components  31 ,  32 ,  35  and  36  rotate, as being driven by the first and second drive motors  34 ,  38 .  
         [0036]     At a position slightly lower than the center of the drum  30 , there is disposed a rotary shaft  40  in the horizontal direction as shown in  FIG. 1 . The rotary shaft  40  is molded as a pipe, the right end thereof is supported by a non-illustrated right bearing in a rotative manner, and the portion set back from the left end is supported by a non-illustrated left bearing in a rotative manner, and the left end is projected out from a left side plate  1   c  of the roaster  1 . To the rotary shaft  40 , first to fourth beaters  41  to  44  are sequentially fixed at regular intervals from one end to the other end of the rotary shaft  40 . The first to fourth beaters  41  to  44  are respectively composed of, as shown in  FIG. 8 , axes  41   a  to  44   a  fixed normal to the longitudinal direction of the rotary shaft  40 , and nearly hemicircular stirring blades  41   b  to  44   b  formed at the ends of the axes  41   a  to  44   a . Positions of fixation of the first beater  41  and the second beater  42  are tilted from each other by 90° as viewed from one end to the other end of the rotary shaft  40 , and each of the individual stirring blades  41   b  to  44   b  is twisted 40° to the rotary shaft  40 . A non-illustrated third drive motor is fixed on the left side plate  1   c  of the roaster  1 , and the drive shaft of the third drive motor is coupled with the rotary shaft  40  by a non-illustrated chain belt. In this configuration, as the rotary shaft  40  rotates as being driven by the third drive motor, the coffee beans are stirred and moved from the right side towards the left side of the drum  30  by the first to fourth beaters  41  to  44 . The rotary shaft  40  has also first to fourth reflection members  45  to  48  supported thereon. The first reflection member  45  is disposed next to the first beater  41  on the side more closer the to the left side plate  1   c , the second reflection member  46  is disposed between the first beater  41  and the second beater  42 , the third reflection member  47  between the second beater  42  and the third beater  43 , and the fourth reflection member  48  between the third beater  43  and the fourth beater  44 . The first to fourth reflection members  45  to  48  are respectively composed of curved portion  45   a  to  48   a  curved arch-wise, each of the back surface of which being placed on the outer circumferential surface of the rotary shaft  40 , front drooped plate portions  45   b  to  48   b  continued from the curved portions and drooping on the front side of the rotary shaft  40 , and the opposite drooped plate portions  45   c  to  48   c  continued from the curved portions and drooping on the rear side of the rotary shaft  40  so as to oppose with the front drooped plate portions  45   b  to  48   b , respectively. The front drooped plate portions  45   b  to  48   b  and the opposite drooped plate portions  45   c  to  48   c  have, on the lower end portions thereof, thickened portions  45   d  to  48   d , and  45   e  to  48   e , respectively.  
         [0037]     As shown in  FIG. 1 , on the lower side of the drum  30 , there is disposed a gas burner  49  as a heating unit composing the present invention. The gas burner  49  is connected through a piping  49   a  to a non-illustrated gas supply unit, and is provided for heating the coffee beans housed in the drum  30  disposed and rotating thereabove. On the left side of the drum  30 , there is disposed a rotary valve  53  through which the coffee beans roasted in the drum  30  are discharged out of the roaster  1 , which are then transferred through a piping  52  to elsewhere. On the left side of the drum  30 , there is also disposed a discharge path  55  allowing the coffee beans discharged out from the left end of the drum  30  to pass therethrough to reach the rotary valve  53 . The rotary valve  53  has, as constituents thereof, a non-illustrated inlet port formed on the top portion thereof, allowing the roasted coffee beans to flow therethrough, a case  53   a  formed on the lower portion thereof, having a discharge port through which the coffee beans are discharged and being connected to the piping  52 , and a non-illustrated main valve unit housed in the case  53   a , and rotating as being driven by the fourth drive motor  54 . The main valve unit has a plurality of housing chambers formed thereon, into which the coffee beans coming through the inlet port are housed. The coffee beans flowing through the inlet port into the housing chambers on the main valve unit are forced to move to the discharge port as being driven by the fourth drive motor  54 , and then drop into the piping  52 .  
         [0038]     To the main heating chamber  29  having the drum  30  disposed therein, as shown in  FIG. 3 , there is fixed one end of a first duct  58  through which the air (heated air) in the main heating chamber  29  is introduced, and on the opposite end of the first duct  58 , there is disposed an intake fan  59 . The first duct  58  is connected to a non-illustrated intake port formed on the intake fan  59  as shown in  FIG. 3  and  FIG. 5 . To an outlet port  59   a  of the intake fan  59 , as shown in  FIG. 1 , there is connected one end of a second duct  60 , and the other end of the second duct  60  is connected to an auxiliary heater  61 . The auxiliary heater  61  is further connected with the hot air passageway  14  composed of the above-described front side partition plate  10  and the guide plate  13 , shown in  FIG. 2 , while placing a third duct  62  in between. More specifically, the roaster  1  is configured so as to allow the hot air in the main heating chamber  29  to reach the hot air passageway  14  through the first duct  58 , the second duct  60  and the third duct  62 , and then to flow into the preheating chamber  3  in a blown-up manner from the lower side of the support plate  12 , through a large number of through-holes formed in the support plate  12 .  
         [0039]     Operations of the above-described roaster  1  of this embodiment will be described below. The coffee beans charged through the charging port  2  with the aid of pneumatic transportation pass through the cylinder  5  and the metal attachment  6  to reach the preheating chamber  3 , and supported on the support plate  12 . The hot air flows into the preheating chamber  3  (in a blown-up manner) from the lower side of the support plate  12 , after passing through a large number of through-holes formed in the support plate  12 . The coffee beans in the preheating chamber  3 , under heating and drying by the hot air, are then thrown through the opening  9   a  formed in the partition plate  9  into the drum  30  rotating in the main heating chamber  29 . The coffee beans thrown into the drum  30  are stirred by rotation of the drum  30  and the rotation of the first to fourth beater  41  to  44 , and at the same time, gradually moved towards the left side of the roaster  1 , while being tossed up and down over a short range in the drum  30  which rolls with the aid of the first and the second rotating components  31 ,  32 , while being vibrated on the plurality of stepped portions formed thereon. More specifically, when the first to fourth rotating components  31 ,  32 ,  35  and  36  rotate counter-clockwisely, for example, the drum  30  rotates clockwisely with the aid of these first to fourth rotating components  31 ,  32 ,  35  and  36 , as shown in  FIG. 7 . The coffee beans P, which is a powder housed in the drum  30 , move ahead in the direction of rotation of the drum  30  as viewed from the position just under the center of rotation of the drum  30 , but thus forwarded coffee beans P are then forced to move back to the just-under position of the center of the drum  30  while being slightly tossed, when the drum  30  is vibrated with the aid of the steeped portions  31   b  formed on the first and the second rotating components  31 ,  32 . In such repetitive motion and with the aid of the first to fourth beaters  41  to  44 , the coffee beans P are forced to move from the right to left under stirring. Because the gas burner  49  is disposed as the heating unit under the drum  30 , the coffee beans preheated in the preheating chamber  3  are fully roasted (heated) in the drum  30 . The rotary shaft  40  has the reflection members  45  to  48  disposed thereon, so that heat from the gas burner  49  is reflected on the inner surfaces of the first to fourth reflection members  45  to  48 , and radiated towards the coffee beans P side in a focused manner. The roasted coffee beans P pass through the discharge path  55 , and are transferred by the rotary valve  53  to the piping  52 . The air heated by the gas burner  49  flows from the main heating chamber  29  through the first duct  58 , the second duct  60  and the third duct  62  to reach the hot air passageway, and then flows into the preheating chamber  3  from the lower side of the supporting plate  12  (in a blown-up manner), after passing through a large number of through-holes formed in the supporting plate  12 .  
         [0040]     As described in the above, the roaster  1  of this embodiment preheats and dries the coffee beans in the preheating chamber  3 , before roasting them in the drum  30  disposed in the main heating chamber  29 , and can effectively roast the coffee beans as the powder to the cores in the drum  30 , so that it is made possible to provide coffee beans of an extra-high quality. In particular, the preheating in the roaster  1  is effected by the hot air blown upward from the lower side of the support plate  12 , so that there is no fear of causing non-uniform preheating. Because the moisture content in the drum  30  is kept low even when the roaster  1  is cooled by virtue of such preheating in the preheating chamber  3 , it is also made possible to sufficiently suppress the dewing in the roaster  1 , and to effectively avoid a risk of causing contamination. In particular, because the air in the preheating chamber  3  is discharged to the external with the aid of the ventilating fan  23 , the roaster  1  can suppress the contamination in a more effective manner.  
         [0041]     Because the air supplied to the preheating chamber  3  is an air heated by the gas burner  49  in the main heating chamber  29 , energy of the gas burner  49  can effectively be used, demonstrating a large energy-saving effect. Again because the auxiliary heater  61  is disposed midway of the route along which the hot air in the main heating chamber  29  is supplied to the preheating chamber  3 , it is allowable to activate the auxiliary heater  61  when the temperature of the hot air to be supplied to the preheating chamber  3  is low, due to use in the wintertime, or in cold regions.  
         [0042]     In particular in the roaster  1  of this embodiment, as described in the above, the stepped portions composing the present invention are formed only on the first and the second rotating components  31 ,  32  disposed on one side of the drum  30  (the rotating components disposed ahead in the direction of movement of the powder (coffee beans P) in the drum  30  under rotation), and are not formed on the third and the fourth rotating component  35 ,  36  disposed on the opposite side, so that motion of the coffee beans P housed in the drum  30  is just like a food (such as Chinese fried rice) cooked on a frying pan which is shaken by a cook over the fire so as to toss the food at the far end of the frying pan and to return it back to the cook&#39;s side. The roaster  1  can therefore heat every grain of coffee beans in a more uniform manner over the entire surface thereof.  
         [0043]     While the roaster  1  of this embodiment described in the above is such as used for roasting the coffee beans P as the powder, the roaster for powder and granular material of the present invention is, of course, not limited to those roasting the coffee beans P, allowing those used for roasting any powder composed of tea leaf, rice bran or various cereals. The roaster  1  described in the above uses the gas burner as the heating unit composing the present invention, whereas any other heating units such as electric heater can be used so far as they can roast the powder housed in the drum.  
         [0044]     It is apparent that the present invention is not limited to the above embodiments, that may be modified and changed without departing from the scope and spirit of the invention. 
     1  coffee bean roaster      2  charging port      3  preheating chamber      9  partition plate      9   a  opening      12  support plate      14  hot air passageway      29  main heating chamber      30  drum      49  gas burner      38  first duct      59  exhaust fan      60  second duct      62  third duct