GB2197178A - Coffee roasting apparatus - Google Patents

Description

SPECIFICATION Coffee roasting apparatus This invention relates to a coffee roasting apparatus, particularly of small size.

Presently, there are two methods of roasting coffee, a hot blast method and a heat radiation method. The hot blast method is easily utilized in a coffee roaster, as disclosed in US-A-4,325,191 and US-A-4,271,603.

However, the hot blast method produces coffee which is sour and does not smell br taste like real coffee. The heat radiation method maintains the smell and flavour of coffee, but the construction of the roaster for the heat radiation method is complicated and it takes a long time to roast the coffee.

Small size coffee roasters normally use a rotating drum. Thus, as shown in Fig. 1, a drum 1, which is formed of wire cloth and has an end opening covered by a glass plate 2, is rotated by a motor 3, and coffee beans in the drum are heated by a heater 4 disposed at an outer peripheral portion of the drum 1. Alternatively, a drum 1' may be formed of heat resistant glass with wire cloth along the inner surface, as shown in Figs. 2.

In these constructions of coffee roaster, the radiation heat of the heater element cannot be used effectively, because the heater is disposed outside the roasting drum, and the heat is radiated ineffectively for the roasting. If, to resoive this disadvantage, the drum and heater are sealed within same container, the outer dimensions of the roaster are increased without improving the heating efficiency.

Another consideration is that there are two ways of roasting and cooling coffee, a continual process, and separate heating and cooling process. The continual roasting process involves proceding from roasting to cooling within one zone. In this process, the process time is excessive because the temperature control within the zone from roasting to cooling involves much time. However, this long time impairs the smell and flavour of the coffee. In the separate process, the roasting and cooling are carried out separately and follow one another so that the above mentioned disadvantage should be resolved. However, the moving of the roasted coffee beans from the roasting device to the cooling device involves much labour. Thus, efficiency is poor.Also, the cooling should be carried out not only on the roasted coffee beans but also in the interior of the roasting device in readiness for a repetition of the roasting process. Generally, therefore, the roaster is provided with two cooling air circulating devices to cool down the roasted coffee beans and the roasting device, respectively, which involves high manufacturing and operating costs.

It is a primary object of the invention to provide a coffee roasting apparatus in which radiation heat is directly supplied to roast coffee beans with high efficiency, and, in accordance with a first aspect of the invention, a coffee roasting apparatus includes a coffee roasting device comprising a cylindrical container for containing coffee beans during roasting; a cylindrical drum extending axially through the container and rotatably driven by a driving device; a plurality of blades disposed on an outer peripheral surface of the drum and extending closely to an inner peripheral wall surface of the container; and a heater element disposed within the drum.

It is another object of this invention to provide a coffee roaster in which the roasting and cooling are separately performed, but efficiently and, in accordance with a second aspect of the invention, a coffee roasting apparatus comprises an outer housing having an outer frame and a base portion; a roasting device mounted in the outer frame; a cooling space for roasted coffee beans defined between the outer frame and the base portion, and below a discharge opening from the roasting device; and a cooling air circulation way including the cooling space and the interior of the roasting device.

The invention will now be described by way of example with reference to the accompanying drawings, in which: Figures 1 and 2 are diagrammatic cross sectional view of prior roasting devices; Figure 3a is a cross sectional view of a roasting apparatus in accordance with the present invention; Figure 3b is a cross sectional view of the apparatus of Fig. 3a, illustrating the discharge of roasted coffee beans; Figure 4 is a cross sectional view of the roasting device used in Figs. 3; Figure 5a is explanatory sectional view of a discharge device of the roasting apparatus of Figs. 3 and 4; Figure 5b is a side view corresponding to Fig. 5a; Figures 6a and 6b are views corresponding to Figs. 5a and 5b, illustrating the operation of the discharge device; Figure 7 illustrates an electrical circuit for the Figs. 3 to 6 apparatus;; Figure 8 is a graph illustrating temperature and other operating parameters of the Figs. 3 to 7 apparatus; and, Figure 9 is a flow chart of operation of the Figs. 3 to 8 apparatus.

As shown in Figs. 3 and 4, a coffee roasting apparatus 10 according to the present invention has an outer housing 11 in which a roasting device 12 is disposed.

The outer housing 11 comprises an Lshaped outer frame 111 and a base portion 112, and has a cooling space 13 defined between the outer frame 111 and base portion 112. An air outlet hole 14 and a coffee bean supply opening 15 are formed on an upper portion of the outer frame 111 closely adjacent to one another and the supply opening 15 is normally closed by a cover 16. The outer frame 111 is also provided with a coffee bean discharge duct 17 which opens onto the cooling space 13.

The base portion 112 is positioned below the outer frame 111 and is formed with an air inlet portion 1 12a below the discharge duct 17. A cooling container 50 with an opening bottom is disposed on the air inlet portion 1 12a and a wire netting element 51 is disposed on the bottom opening to cover the inlet portion 112a. An interior 1 12b of the base portion functions as an air passageway, and an air duct 52, which extends vertically within the outer frame 111, is connected with the other end of the air passageway 112b.

The air passed through the air passageway 1 12b and connecting duct 52 is introduced into the roasting device 12 through an air duct 53. The air introduced into the roasting device 1 2 flows out to the exterior of the outer housing of the apparatus 10 through the air outlet hole 14. Therefore, an open air circulation way is defined by the cooling space 13, the base portion 112, the ducts 52, 53, the roasting device 12 and the outer frame 111.

The air circulated within the air circulation way is forced by a blower 55 which is disposed in the air passageway 1 12b and driven by a blower motor 56.

The roasting device 12, which is in the upper portion of the outer frame 111, comprises a cylindrical container 20 functioning as a roasting drum, a supporting frame 21 and a cylindrical drum 22 in which a heater element 23 is disposed. The cylindrical container 20 is formed of a transparent material with heat resisting characteristic, for example glass, and both end openings of the container 20 are covered by end plates 211, 212 of the supporting frame 21, respectively. The cylindrical drum 22 which is formed of porous material, for example, wire cloth, extends horizontally within the cylindrical container 20 and outwardly through the end plates 211, 212. A plurality of blades 223 are fixed on an outer peripheral surface of the drum 22, for rotating together with the drum 22, and extend to closely adjacent to the inner peripheral wall surface of the container 20.

During the heating or roasting operation, a large quantity of smoke and/or smelly vapour may emanate from the coffee beans, and as a result of this phenomenon, the inner surface of the glass container 20 may become dim or cloudy. One solution to resolve the above disadvantage, is to form the wire cloth drum of oxide catalyst. The formation of the smoke and/or vapour is then repressed by chemical reaction with the oxide catalyst.

Both ends of the drum 22 are covered by respective closure plates 221, 222, each of which is rotatably supported on a fixed shaft 24 via a bearing 25. Each shaft 24 is fixedly supported on a respective supporting frame 26 fastened on the end plate 211 or 212. An axial flange 222a is formed on one end plate 222, and a sprocket 39 is fixed on the flange.

The sprocket 39 is connected with a sprocket 27 fixed on a drive shaft of a driving motor 28 through an endless chain 29. Thus, the drum 22 is rotatably disposed within the container 20.

A coffee bean entry hole 211a, which also functions as a hot air outlet hole 211a, and a coffee bean discharge hole 211b, are formed through the end plate 211, and an air inlet hole 21 2a is formed through the other end plate 212. A coffee bean guiding plate 30 is fixed on the end plate 211 leading to the coffee bean entry hole 211a. The discharge hole 211 b is closed by a rotatable cover plate 31.

The roasting device 12 is also pivotably supported in the outer frame 111 by a device 32. As shown in Figs. 5 and 6, the supporting frame 21 is supported on the outer frame 111 by a supporting shaft 33 via supporting bearing elements 34 which are disposed on the bottom surface of the supporting frame 21 and provided with a discharge motor 35 of the discharge device 32 at one end. The motor 35 is connected with an eccentric can element 36, which is rotatably supported in a cam frame 37 on the outer frame 111, through a connecting rod. Thus the roasting device 1 2 can be swung around the supporting shaft 33 upon operation of the discharge device 32.Thus, as shown in Figs. 5a and 5b, the roasting device 12 can adopt a horizontal position, but, if the motor 35 rotates the cam through 180 , (as shown in Figs. 6a and 6b), the roasting device 12 is swung around the shaft 33 and the container 20 is inclined to discharge the roasted coffee beans.

Fig. 7 shows the control for the roasting device. A controller 40, which controls the operation of the motors, heater element 23 and other elements, is connected to an electrical power source through a main/preheating switch 41 and receives a detection signal from a thermosensor 42, which is disposed in the container 20 for detecting the temperature in the container 20. The controller 40 is connected with the driving motor 28, the discharge motor 35, the heater element 23, the blower motor 56 and a display signal 57, and controls the operation of these elements by output signals therefrom.

The roasting process will be described with reference to Figs. 8 and 9. At a normal temperature, for example 20"C, the main/preheating switch 41 is closed to start the roasting process (this is represented by step a in Fig.

9), and the controller 40 accepts the flow of a predetermined level of electrical current to operate the blower motor 56 and heater element 23. At this time, the blower motor is rotated at low speed. Thus the interior of the container is preheated for raising and its temperature is raised. During the preheating process, if temperature in the container 20 reaches a predetermined temperature, for example 1300C, the display signal 57 is energised and the supply of electrical current to the heater element 23 is cut out owing to an output signal from controller 40 (this is represented by steps b and c in Fig. 9).After the predetermined temperature is reached and the operation of the heater element 23 is cut off, the temperature in the container is maintained (insulated) in a predetermined range by operation of the controller 40, i.e. the controller 40 controls the heater element 23 upon change of temperature detected by the thermosensor 42 (this is represented by step d in Fig. 9). In this situation, the roasting apparatus is ready for the roasting operation.

In the above condition, if coffee beans are introduced into the interior of the container 20, the temperature in the container 20 is suddenly reduced. The controller 40 detects this situation through the thermosensor 42 and if the detected temperature is below the predetermined temperature, for example 1300C, the controller 40 supplies electrical current to the heater element 23 to start automtically the roasting operation (this is represented by steps e and fin Fig. 9). Therefore, the temperature in the container 20 is gradually increased, as shown in Fig. 8. Also, the wire netting drum 22 is rotated by operation of the driving motor 28. At the same time, the plurality blades 223 are rotated following rotation of drum 22 to stir up the coffee beans in the container 20.Thus the coffee beans receive directly radiant heat from the heater element 23 through the drum 22 while rolling within the container 20. As the result of the above described roasting operation, the heating and roasting are highly efficient.

After passage of time, when the temperature in the container 20 reaches the roasting operation finished temperature, for example 170"C, and the controller 40 has determined that the temperature in the container 20 exceeds a predetermined temperature, the operation of the heater element 23 is stopped by an output signal from the container 40 and then the roasting operation is finished (this situation is indicated by steps g and h in Fig.

9). At this time, the display signal 57 is energised for indicating the finish of the roasting operation.

After the roasting operation has finished, the controller 40 drives the discharge motor 35 for a predetermined time (this is represented by step i in Fig. 9). Thus, the eccentric cam element 36 is rotated through 1800 to cant the roasting device 12. As the result of canting of the roasting device 12, the roasted coffee beans are discharged into the cooling container 50 in the cooling space 13 via the discharge opening 21 1b and discharge duct 17. As shown in Fig. 3b, the cover plate 31 is pivoted to open the discharge hole 21 1b owing to canting of the supporting frame 21 1b and discharge duct 17. This- discharge operation of the roasted coffee is promoted by the rotating operation of the blades 223.

After the passage of a predetermined time, the discharge motor 35 returns the roasting device 12 to its horizontal position assisted by its dead weight. Also, at the same time, the blower motor 56 is driven at high speed to promote air circulation (this is represented by step j in Fig. 9). Therefore, roasted coffee beans in the cooling container 50 in the cooling space 13 are cooled by the circulated air, and also the interior of the container 20 is cooled down by the air introduced from the air passageway, to thereby bring down the temperature in the container 20 quickly.

During the cooling process, the controller 40 checks the temperature in the container 20 through the thermosensor 42 to determine when the interior temperature is below the predetermined temperature (this is represented in by step k in Fig. 9), and when the detected temperature is below the predetermined temperature, the roasting process can progress to the next step, such as step 1. In step 1, the controller 40 decides whether the main/preheating switch 41 has to be closed. Then, if the switch 41 is open, the roasting process is finished, and if the switch 41 is still closed, the operation of the controller 40 is returned to step d to maintain the temperature in the container 20 to await the next roasting operation.

As mentioned above, the roasting apparatus is provided with a roasting device which includes a cylindrical container and a drum containing a heater element. Therefore, radiation heat or convection heat are effectively used to roast the coffee beans. Furthermore, the roasting apparatus comprises separate roasting device and cooling space, and these two parts are substantially connected with one another through an air circulation way. Therefore, cooling the interior of the container and the roasted coffee are accomplished by a single blower, to thereby minimise manufacturing cost and provide compactness. Also, the cooling space is positioned below the discharge opening of the container, and the roasting device is pivotable in the housing.

Therefore, the roasted coffee beans are automatically discharged into the cooling space, to thereby provide a highly efficient roasting and discharge operation.

Claims (3)

1. A coffee roasting apparatus comprising an outer housing having an outer frame and a base portion; a roasting device mounted in the outer frame; a cooling space for roasted coffee beans defined between the outer frame and the base portion, and below a discharge opening from the roasting device; and a cooling air circulation way including the cooling space and the interior of the roasting device.

2. Apparatus according to claim 1, wherein the roasting device is a roasting drum which is pivotally mounted in the outer frame whereby the roasting drum may adopt a roasting position, in which the axis of the drum is substantially horizontal, and a discharge position, in which the axis of the drum is inclined with the discharge opening adjacent to the lowermost part of the drum.

3. Apparatus according to claim 1 or claim 2, wherein the circulation way contains a blower for forcing coling air through the circulation way.