Drum roaster for bean roasting

Abstract

The present invention relates to a drum-type roaster (2) for roasting beans, comprising a housing assembly (4) for rotatably supporting a roasting drum (12) containing beans. The roasting drum (12) is also provided with a drive means for rotating the roasting drum (12) and a heating assembly (20) for heating the beans with at least heated air. The heating assembly (20) has at least one electric heating element (14) for heating supply air, which is disposed in a heating pipe (13) upstream of the roasting drum (12) in the direction of heated air flow. A suction fan (18) for exhausting the heated air from the roasting drum (12) is disposed downstream of the roasting drum (12) in the direction of heated air flow. The heating assembly (20) also has a blower fan (16) disposed upstream of the electric heating element (14) in the direction of supply air flow.

Description

[Technical Field]

[0001] The present invention relates to a drum roaster for roasting beans, comprising a housing assembly for rotatably supporting a roasting drum containing beans, a drive means for rotating the roasting drum, and a heating assembly for heating the beans with at least heated air, the heating assembly having at least one electric heating element for heating supply air, the electric heating element being arranged in a heating tube upstream of the roasting drum in the direction of heated air flow, and a suction fan for exhausting the heated air from the roasting drum being arranged downstream of the roasting drum in the direction of heated air flow. [Background technology]

[0002] Such drum roasters are well known in the art and are used, particularly in small roasting plants, shops, and cafes, as so-called mini-roasters or commercial roasters. An example of this is the drum roaster described in German Utility Model No. 202017002951. An electric heating element, such as an electric heated air generator with a ceramic heating resistor, is provided, and heated air is drawn into the roasting drum by a suction fan. The generation of heated air by this electric heating element with a suction fan is highly dependent on ambient conditions. This can lead to significant fluctuations in the vacuum pressure inside the roasting drum, leading to undesirable roasting results. It is known, however, in the field of domestic roasters (see, for example, European Patent No. 2179665, for roasting volumes of 0.5 kg to 2 kg), to place a high-pressure blower upstream of the electric heating element to direct heated air into the roasting drum. However, this makes controlling the heated air even more difficult than the aforementioned suction fan embodiment. Summary of the Invention [Problem to be solved by the invention]

[0003] The object of the present invention is to avoid the above-mentioned drawbacks in a simple and cost-effective manner. [Means for solving the problem]

[0004] This object is achieved by a heating assembly comprising a blower fan according to the invention, which is arranged upstream of the electric heating element in the direction of the blown air flow. This ensures a uniform flow of supply air to the roasting drum in a particularly simple and cost-effective manner. The roasting process can be controlled by the user in a very simple way. In addition, reliable cooling of the electric heating element is ensured in all operating situations. The blower fan is preferably configured as a side fan.

[0005] The ceramic heating element is particularly easy and inexpensive to manufacture and is configured as an electric heating element that can be cooled in a simple manner, wherein the ceramic element is provided with channels in which the heating rods are arranged, and the supply air flows through the channels.

[0006] In a preferred embodiment, a controller for at least the heating assembly is provided, the controller controlling at least the heating process.

[0007] A preferred embodiment is characterized in that the electric heating element is provided with a collection container for the supply air conveyed by the blower fan, which essentially serves to smooth the flow of the supply air. A pressure monitor fluidly connected to the heating pipe can be provided to ensure a minimum flow rate through the electric heating element.

[0008] A frequency converter is preferably provided to control the blower fan, allowing for energy efficient operation at constant airflow and easy speed control of the blower fan.

[0009] A temperature sensor in the heating tube facilitates monitoring the temperature of the electric heating element: if the temperature of the electric heating element gets too high, the temperature sensor detects this and shuts off the electric heating element for safety reasons.

[0010] In a preferred embodiment, a protective temperature limiter is provided in the heating tube, which in the event of overheating is able to turn off the heating element and generate an error message.

[0011] In a preferred embodiment, the electric heating element includes a clock-controlled power supply as the first control circuit. This allows for simple control of the heating energy and thus of the roasting process. For this purpose, a semiconductor switch with a PWM signal at its input can be installed in the clock-controlled power supply. This signal can be determined by a PID controller, which compares the set and actual heated air temperatures at the input of the PID controller of the electric heating element.

[0012] A second control circuit can be provided to set the temperature according to a recipe during automatic roasting, which compares the set recipe temperature with the actual recipe temperature at the input of the PID controller. Preferably, the roasting temperature, the heated air temperature and / or the exhaust air temperature can be taken into account as recipe temperatures.

[0013] The invention will now be further explained with reference to the drawings. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a partial cross-sectional side view of a drum roaster according to the present invention. [Figure 2] FIG. 2 is a detailed view of an electric heating element and a blower fan fluidly connected to the electric heating element. [Figure 3] FIG. 3 is a schematic diagram of the first control circuit. [Figure 4] FIG. 4 is a schematic diagram of the second control circuit. DETAILED DESCRIPTION OF THE INVENTION

[0015] FIG. 1 shows a typical drum roaster 2 for commercial use. The drum roaster 2 has a housing assembly 4, which essentially comprises a drum housing portion 6 and a base housing portion 8. For clarity, the base housing portion 8 is shown open and without a cover panel. The drum housing portion 6 is disposed on the base housing portion 8, which contains a container 10 for roasted beans. Arranged in a known manner inside and on top of the drum housing portion 6 are a roasting drum 12 (shown here in partial cross section), a drive mechanism (not shown in detail) for rotating the roasting drum 12, and a heating element 14 (shown here in schematic cross section) for heating the heated air supplied to the roasting drum 12. The heating element 14 is configured as a ceramic heating element. A heating tube 13 containing the electric heating element 14, together with a blower fan 16 and a suction fan 18, constitutes a heating assembly 20. This heating assembly 20 supplies heated air to blow into the roasting drum 12 and ensures exhaust removal by a cyclone 22 of known type. The assembly is controlled by a control device 23. Heat transfer to the beans is by direct contact with the heated air by convection and by heat transfer through the roasting drum 12 by conduction. A display 24 located in the drum housing part 6 here serves as an input and display panel for the user.

[0016] Also shown in the figure is a bean inlet funnel 26, a sampling device 28, and a bean outlet device 30 including the collection container 10. Below the collection container 10 are a mixing drive 32 (not shown in detail) for the mixing device, rotatably supported within the collection container 10, and a cooling air fan 34 for supplying cooling air to the collection container 10.

[0017] As already mentioned, a blower fan 16 is provided for supplying blown air, and this blower fan 16 is arranged upstream of the electric heating element 14 in the direction of flow of the blown air. Furthermore, the heating tube 13 is provided with a collection container 36 between the blower fan 16 and the heating tube 13 carrying the electric heating element 14, for stabilizing the flow of blown air. A pressure monitor 38 is in fluid connection with the heating tube 13 and monitors the pressure within the heating tube 13, thereby ensuring a minimum flow rate and thereby ensuring reliable cooling of the electric heating element 14. A frequency converter (not shown in detail) controlling the blower fan 16 allows for energy-efficient operation and easy speed control.

[0018] A temperature sensor 40 is provided to monitor the heating air temperature inside the heating tube 13, and this temperature sensor 40 extends into the heating tube 13 to monitor the temperature. The heating tube 13 is further provided with a protection limiter 42 that immediately shuts down the electric heating element 14 if the temperature limit is exceeded. The pressure monitor 38, temperature sensor 40, and protection limiter 42 are connected to the controller 23 via the heating assembly 20 using control technology. A clock-controlled power supply is provided to easily control the heating energy provided by the electric heating element 14, which constitutes a first control circuit 44 (see Figure 3). A second control circuit 46 is provided for recipe-based temperature control during automatic roasting and is illustrated in Figure 4.

[0019] 2 shows in more detail the heated pipe 13 with the upstream collection vessel 36 and the blower fan 16. The pressure monitor 38, temperature sensor 40 and protective temperature limiter 42 are also clearly visible here.

[0020] 3 shows a schematic diagram of a first control circuit 44 for the clocked power supply of the electric heating element 14, implemented in the control device 23. The roasting process stored in the control device 23 specifies a percentage of maximum heating power. This is converted in block 48 to a set recipe temperature 50 in °C and compared with an actual recipe temperature 52. The difference value 53 serves as an input signal for a PID controller 54 of the electric heating element 14 and is supplied as a PWM signal to a semiconductor switch 56. It then generates a clocked power supply for the heating element 14, whose actual temperature (in this case the actual recipe temperature 52) is monitored by the temperature sensor 40.

[0021] 4 shows a schematic diagram of the second control circuit 46 that sets the recipe temperature during the automatic roasting process. The roasting process stored in the controller 23 selects a recipe set temperature 60 from a recipe in block 58 and compares it to an actual recipe temperature 62. The difference value 64 serves as an input signal for a PID controller 66 that controls the heating assembly 20. The actual recipe temperature 62 is also monitored here by the temperature sensor 40. The roast, heated air, and / or exhaust temperatures may function as the recipe set point or the actual temperature.

Claims

1. A drum roaster (2) for roasting beans, comprising a housing assembly (4) for rotatably supporting a roasting drum (12) containing beans; a driving means for rotating the roasting drum (12) and a heating assembly (20) for heating the beans with at least heated air; The heating assembly (20) comprises at least one electric heating element (14) for heating the supply air and a suction fan (18) for exhausting the heated air from the roasting drum (12), the electric heating element (14) being arranged in the heating pipe (13) upstream of the roasting drum (12) in the direction of flow of the heated air, and the suction fan (18) being arranged downstream of the roasting drum (12) in the direction of flow of the heated air; The heating assembly (20) has a blower fan (16) arranged upstream of the electric heating element (14) in the direction of flow of the supply air.

2. 2. The drum roaster (2) according to claim 1, further comprising a control device (23) for at least said heating assembly (20).

3. 2. The drum roaster (2) according to claim 1, wherein the electric heating element (14) is configured as a ceramic heating element.

4. 2. The drum roaster (2) according to claim 1, wherein the electric heating element (14) is provided with a collection container (36) for the blown air supplied by the blower fan (16).

5. 3. The drum roaster (2) according to claim 2, further comprising a pressure monitor (38) fluidly connected to the heating pipe (13).

6. 6. The drum roaster (2) according to any one of claims 1 to 5, further comprising a frequency converter for controlling the blower fan (16).

7. 6. The drum roaster (2) according to any one of claims 2 to 5, wherein a temperature sensor (40) is provided in the heating tube (13).

8. 6. The drum roaster (2) according to any one of claims 2 to 5, wherein a protective temperature limiter (42) is provided in the heating tube (13).

9. 6. The drum roaster (2) according to any one of claims 2 to 5, wherein the electric heating element (14) is provided with a clock-controlled power supply as the first control circuit (44).

10. 10. A drum roaster (2) according to claim 9, wherein the clock-controlled power supply is provided with a semiconductor switch having at its input a PWM signal determinable by a PID controller, the set temperature of the heated air being compared at the input of the PID controller with the actual temperature of the heated air in the electric heating element.

11. 8. A drum roaster (2) according to claim 7, wherein a second control circuit (46) is provided for setting the recipe temperature in the case of automatic roasting, the set recipe temperature being compared with the actual recipe temperature at the input of the PID controller.

12. 10. The drum roaster (2) according to claim 9, wherein the roasting temperature, the heated air temperature and / or the exhaust air temperature are taken into account as recipe temperatures.

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