| 摘要 |
A coffee maker comprises a pump for pressurizing water, a pump tube connected to an outlet side of the pump, and a brewing chamber which is adapted to accommodate a coffee pad. During operation of the coffee maker, the water is heated and pressed through a coffee pad in order to obtain coffee. In order for the performance of the coffee maker to be stable, it is important that a predetermined pressure is obtained in the brewing chamber. The stability of the performance is found to be dependent on a ratio between a length of the pump tube and a wavelength of a wave which is caused by the pump in the pump tube during operation. If said ratio is within a range of 0.3 to 0.7±0.5N, wherein N is an integer, the performance is stable. However, if the ratio is outside of this range, the performance is unstable.
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