FIELD OF THE INVENTION

The disclosure relates to a soymilk maker, and more particularly relates to a soymilk maker with a grinding mechanism. BACKGROUND OF THE INVENTION

Soy beverage (also called soymilk) is a beverage made from soybeans. As a traditional staple of Asian cuisine, it is a stable emulsion of oil, water and protein, and produced by soaking dry soybeans and grinding them with water.

Soymilk can be made at home with traditional kitchen tools or with a soymilk maker. Generally speaking, there are two different ways to produce soymilk by means of a soymilk maker: either grinding beans by means of a blade or blades, or milling beans by using a miller. The current market tendency shows that the soymilk maker with the milling function is becoming dominant, since users believe that the milling process can keep more nutrition in the soymilk and makes it taste better.

However, there are some technical problems with respect to the milling process. Compared with the rotational speed during the grinding process, i.e. about 8,000 -10,000 rpm, the milling process generally takes place at a low rotational speed, i.e. about 1,000 ~ 4,000 rpm. For a traditional milling process beans have to be soaked for about 6 hours before the beans are soft and consequently can be milled easily and also cannot get jammed in the miller. In present day soymilk machines unsoaked beans are used and, in spite of this, the milk always needs to be ready in 25 minutes, therefore milling is facing a challenging task.

In order to solve this technical problem, a blade is provided to work together with the rotary milling disc, so that the unsoaked beans can be cut before being milled, thus preventing the beans from jamming and helping to improve the milling efficiency. Fig. 10 illustrates a grinding mechanism 100 of a soymilk maker according to the prior art. Specifically, the grinding mechanism 100 comprises a motor (not shown), a blade 102 and a miller 104 including a stationary milling disc 1041 and a rotary milling disc 1043. The blade 102 is mounted on the output shaft 106 of the motor and driven by the motor. The stationary milling disc 1041 is immovable in the housing of the soymilk maker. The rotary milling disc 1043 is engaged with the stationary milling disc 1041, and is also mounted on the output shaft 106 of the motor and driven by the motor. Once the motor is activated, the blade 102 and the rotary milling disc 1043 are driven to rotate at the same rotational speed.

It is desirable to control the rotational speed of the rotary milling disc 1043 so as to be below a certain rotational speed, for example, 3500 rpm, while maintaining the speed of the blade 102 as high as possible. Consequently, as the speed of the blade 102 is restricted by the rotational speed of the rotary milling disc 1043, the beans could not be cut efficiently prior to being milled.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a soymilk maker is disclosed, which comprises a housing and a grinding mechanism accommodated within the housing. The grinding mechanism comprises a motor mounted in the housing, a blade being rotatable in a first plane at a first rotational speed for grinding soybeans under the action of the motor for cutting the soybeans, and a miller being rotatable in a second plane at a second rotational speed under the action of the motor for milling the soybeans. The second plane is spaced from and extends substantially parallel to the first plane, and the first rotational speed is higher than the second rotational speed.

In an embodiment, the speed ratio between the first rotational speed and the second rotational speed is within the range of 1.5-15.

In a preferred embodiment, the speed ratio between the first rotational speed and the second rotational speed is within the range of 1.67-6.

In an embodiment, the first rotational speed is within the range of 2,000-20,000 rpm, and the second rotational speed is within the range of 1,000-7,000 rpm.

In a preferred embodiment, the first rotational speed is within the range of 5,000-8,000 rpm, and the second rotational speed is within the range of 1,000-3,000 rpm. In an embodiment, the miller comprises a stationary milling disc and a rotary milling disc which can be driven by the motor to rotate with respect to the stationary milling disc.

In some embodiments, the grinding mechanism may further comprise a transmission assembly, the transmission assembly being configured such that the blade and the rotary milling disc are rotatable simultaneously during at least part of the soymilk making process.

In such embodiments, the transmission assembly may at least comprise a pair of engaging gears configured to operate as a decelerator or an accelerator, and a shaft configuration for respectively supporting the gears and driving the blade and the rotary milling disc provided on the shaft. In a preferred embodiment, the decelerator is constituted by a first gear and a second gear of the pair of engaging gears, and the shaft configuration includes the output shaft of the motor and another output shaft parallel to the output shaft of the motor; the first gear being fixedly mounted on the output shaft of the motor, the second gear being fixedly mounted on another output shaft and engaging the first gear and the number of teeth of the second gear being larger than that of the first gear; wherein the blade is mounted on the output shaft of the motor, and the rotary milling disc is fixedly mounted on the other output shaft. In an alternativeembodiment, the accelerator is constituted by a first gear and a second gear of the pair of engaging gears, and the shaft configuration includes the output shaft of the motor and another output shaft parallel to the output shaft of the motor; the first gear being fixedly mounted on the other output shaft parallel to the output shaft of the motor, the second gear being fixedly mounted on the output shaft of the motor and engaging the first gear and the number of teeth of the second gear being larger than that of the first gear; wherein the blade is mounted on the other output shaft, and the rotary milling disc is fixedly mounted on the output shaft of the motor.

In yet another embodiment, the transmission assembly may comprise a pair of belt-linked pulleys configured to operate as a decelerator or an accelerator, and a shaft configuration for respectively supporting the pulleys and driving the blade and the rotary milling disc provided on the shaft.

In a further embodiment, the transmission assembly may comprise a first gear, a second gear and a third gear set arranged between the first gear and the second gear; the first gear, the second gear and the third gear set being configured as a planetary gear drive mechanism; wherein the first gear is configured as a sun gear, and the second gear is configured as an outer ring gear, and each gear of the third gear set is configured as a planetary pinion rotatably fixed to an immovable carrier, wherein the blade is driven by the motor, and the rotary milling disc is driven by the second gear. In some other embodiments, the transmission assembly may comprise a first gear, a second gear and a third gear set arranged between the first gear and the second gear; the first gear, the second gear and the third gear set being configured as a planetary gear drive mechanism; wherein the first gear is configured as a sun gear, and the second gear is configured as an outer ring gear, and each gear of the third gear set is configured as a planetary pinion rotatably fixed to an immovable carrier, wherein the rotary milling disc is driven by the motor, and the blade is driven by the first gear.

In the above two planetary gear drive mechanisms, the second gear is an annular wall protruding from the surface of the rotary milling disc which is opposite to the surface mated with the stationary milling disc, wherein the annular wall is provided with a plurality of teeth mated with each gear of the third gear set. In a preferred embodiment, the carrier includes an upper plate, a lower plate and a cylindrical portion connecting the upper plate and the lower plate and having a longitudinal through-hole extending from the upper plate to the lower plate, wherein said third gear set are uniformly and rotatably fixed on the upper plate of the carrier, the stationary milling disc and the rotary milling disc are rotatably mounted on the cylindrical portion, and the through-hole allows the output shaft of the motor to rotatably pass through.

In some embodiments of the present invention, the grinding mechanism further comprises a first clutch capable of connecting the motor to the blade for transferring movement of the motor to the blade, a second clutch capable of connecting the motor to the rotary milling disc for transferring movement of the motor to the rotary milling disc, wherein the blade is driven by the first clutch in order to rotate while the rotary milling disc is immovable when the motor is rotated in a first rotational direction, and the rotary milling disc is driven by the second clutch in order to rotate while the blade is immovable when the motor is rotated in a second rotational direction opposite to the first rotational direction. Specifically, the first clutch is a unidirectional clutch, and the second clutch is a unidirectional clutch reversely arranged with respect to the first clutch . More specifically, the unidirectional clutch is an overrunning clutch such as a ratchet-like clutch or a roller-type clutch.

In such embodiments, the first clutch may be a ratchet-like clutch, and comprises a first plate on which the blade is mounted and a first rotor driven by the motor, wherein the first plate has a housing defining a cavity and at least one projection protruding from the housing toward the cavity, and correspondingly the first rotor is rotatably arranged within the cavity and has a first portion and a second portion, wherein the second portion is pivotally connected with the first portion such that the second portion is engaged with the projection so as to cause the first plate to rotate when the first rotor is rotated in the first direction and is disengaged from the projection so as to release the first plate when the first rotor is rotated in the second direction.

Alternatively, in such embodiments the second clutch may be a ratchet-like clutch, and comprises a second plate on which the rotary milling disc is mounted and a second rotor driven by the motor, wherein the second plate has a housing defining a cavity and at least one projection protruding from the housing toward the cavity, and correspondingly the second rotor is rotatably arranged within the cavity and has a first portion and a second portion, wherein the second portion is pivotally connected with the first portion such that the second portion is disengaged from the projection so as to release the second plate when the second rotor is rotated in the first direction and is engaged with the projection so as to cause the second plate to rotate when the second rotor is rotated in the second direction.

Specifically, the second plate is an annular wall protruding from the surface of the rotary milling disc which is opposite the surface mated to the stationary milling disc.

In some embodiments, the soymilk maker according to the invention may further comprise a controller and a rotational direction control circuit, wherein the controller is used for generating an electrical signal for changing the rotational direction of the motor, and the rotational speed control circuit is used for changing the first rotational direction of the motor to the second rotational direction as long as it receives the electrical signal from the controller. BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and features of the present invention will become more apparent from the following detailed description considered in connection with the accompanying drawings, in which:

Fig. 1 is a schematic view of a soymilk maker according to the present invention;

Fig. 2 is a perspective view of a grinding mechanism according to the first embodiment of the present invention;

Fig. 3 is an exploded view of the grinding mechanism of the first embodiment as shown in Fig. 2;

Fig. 4 is a perspective bottom side view of the rotary milling disc of the grinding mechanism as shown in Fig. 3;

Fig. 5 is a perspective view of a grinding mechanism according to the second embodiment of the present invention;

Fig. 6 is an exploded view of the grinding mechanism of the second embodiment as shown in Fig. 5;

Fig. 7 is a perspective bottom side view of the rotary milling disc of the grinding mechanism as shown in Fig. 6;

Fig. 8 is a perspective bottom side view of the stationary milling disc of the grinding mechanism as shown in Fig. 6;

Fig. 9 is a perspective bottom side view of the upper cover with the blade of the grinding mechanism as shown in Fig. 6; and

Fig. 10 is a schematic view of a grinding mechanism according to the prior art. Throughout the above drawings, like reference numerals will be understood to refer to like, similar or corresponding features or functions.

DETAILED DESCRIPTION

Reference will now be made to embodiments of the invention, one or more examples of which are illustrated in the figures. The embodiments are provided by way of explanation of the invention, and are not meant as a limitation of the invention. For example, features illustrated or described as part of one embodiment may be used with another embodiment to yield a still further embodiment. It is intended that the invention encompass these and other modifications and variations as come within the scope and spirit of the invention.

Figs. 1-4 illustrate a soymilk maker 10 in accordance with the first embodiment of the present invention. Specifically, the soymilk maker 10 comprises a housing 12 and a grinding mechanism 200 including a motor 202, a miller 204 and a blade 206. The housing 12 has an inner cavity defined by a generally cylindrical outer wall 12a, a bottom wall 12b and an upper wall 12c. An intermediate wall 12d arranged between the bottom wall 12b and the upper wall 12c divides the inner cavity into a lower cavity for receiving the body 2021 of the motor 202 and an upper cavity for receiving the miller 204 and the blade 206. More specifically, the body 2021 of the motor 202 can be fixedly deposited within the lower cavity such that the output shaft 2023 of the motor 202 upwardly passes through the through -hole defined in the intermediate wall 12d and is substantially upright in the upper cavity.

The miller 204 includes a stationary milling disc 208 and a rotary milling disc 210. The stationary milling disc 208 and the rotary milling disc 210 are generally disc-shaped and may be made of metal, such as stainless steel. Specifically, the upper surface of the stationary milling disc 208 is provided with a plurality of oblique ribs 208a around a central through-hole 208b. The space defined by every two ribs 208a becomes gradually narrower from the outermost ends of the ribs 208a to the innermost ends thereof. Moreover, the innermost ends of ribs 208a are at a distance from the center of the stationary milling disc

208, and thus a central collecting area is formed. Correspondingly, the lower surface of the rotary milling disc 210 is also provided with a plurality of oblique ribs 210a around a central through-hole 210b, which can be mated to the ribs 208a to mill beans when the rotary milling disc 210 is rotated with respect to the stationary milling disc 208. The above mentioned ribs 208a, 210a could also be referred to as milling teeth. An annular wall 210c upwardly protruding from the upper surface of the rotary milling disc 210 extends circumferentially around the central through hole 210b, which annular wall can be integral with the rotary milling disc 210 or can be made separately and then fixed to the upper surface of the rotary milling disc 210 by fasteners such as bolts or by welding. The inner surface of the annular wall 210c is uniformly provided with teeth so that the annular wall 210c could serve as an outer ring gear in the planetary gear drive mechanism described below. Those skilled in the art can readily understand that the milling teeth of the stationary milling disc 208 and the rotary milling disc 210 can be substituted by other conventional configurations.

As shown in Fig. 3, the grinding mechanism 204 further comprises a carrier 212, three external gears 214 and an external gear 216. Specifically, the carrier 212 comprises an upper plate 212a, a lower plate 212b and a cylindrical portion 212c connecting the upper plate 212a with the lower plate 212b and having a longitudinal through -hole 212d extending from the upper plate 212a to the lower plate 212b. Said three external gears 214 are uniformly and rotatably fixed on the upper surface of the upper plate 212a of the carrier 212, and the angle between every two of three external gears 214 is 120 degrees. Since both the stationary milling disc 208 and the rotary milling disc 210 are retained between the upper plate 212a and the lower plate 212b, and rotatably mounted on the cylindrical portion 212c of the carrier 212 after assembly, the upper plate 212a of the carrier 212 can be received within the cavity defined by the annular wall 210c so as to allow each of three external gears 214 to engage with the teeth of the annular wall 210c. Said external gear 216 can be fixedly mounted on the output shaft 2023 of the motor 202 and positioned at the center of the annular wall 210c to engage each of three external gears 214. Therefore, the external gear 216, the three external gears 214 and the annular wall 210c constitute a planetary gear drive mechanism, of which the external gear 216 serves as a sun gear, and each of the three external gears 214 serves as a planet pinion, and the annular wall 210c serves as an outer ring gear. An upper cover 218 is provided to cover the annular wall 210c to prevent the planetary gear drive mechanism from exposure.

The blade 206 can be integrally made of metal, such as stainless steel, which may comprise a circular portion 206a defining a hole 206b in the center thereof and three branches 206c extending from and being uniformly distributed around the circular portion

206a. In more detail, the extreme end portions of these branches 206c are slightly bent upward. The blade 206 on the upper cover 218 can be fixedly mounted on the output shaft 2023 of the motor 202. Preferably, an end cap (not shown) can be threaded on the end of the output shaft 2023 of the motor 202 so as to prevent the blade 206 from falling off.

During installation, the lower plate 212b is fixedly connected to the cylindrical portion 212c of the carrier 212 after the stationary milling disc 208 and the rotary milling disc 210 have been rotatably mounted on the cylindrical portion 212c. Then, the carrier 212 is rotatably mounted on the output shaft 2023 of the motor 202. Subsequently, the external gear 216 is fixedly mounted on the output shaft 2023 of the motor 202 and also engaged with each of three external gears 214. Thereafter, the upper cover 218 is rotatably mounted on the output shaft 2023 of the motor 202 to cover the annular wall 210c on the rotary milling disc 210.

Finally, the blade 206 is fixedly mounted on the output shaft 2023 of the motor 202.

After the motor 202, the miller 204 and the blade 206 have been assembled as shown in the assembly of Fig. 2, the blade 206 is positioned right above the rotary milling disc 210. Consequently, the first plane in which the blade 206 is rotatable is spaced from and extends parallel to the second plane in which the rotary milling disc 210 is rotatable.

When the motor 202 is activated, on the one hand, the blade 206 is driven by the output shaft 2023 of the motor 202 to rotate at the first rotational speed and, on the other hand, the external gear 216 is driven by the output shaft 2023 of the motor 202 to cause rotation of the annular gear 210c via three external gears 214, and thus the rotary milling disc 210 is driven to rotate along with the annular gear 210c at the second rotational speed.

Due to the characterization of the configuration of the planetary gear drive mechanism, the first rotational speed must be higher than the second rotational speed.

Specifically, the first rotational speed is equal to the rotational speed of the output shaft 2023 of the motor 202, and the second rotational speed can be determined by dividing the first rotational speed by the drive ratio of the planetary gear mechanism. More specifically, the first rotational speed is within the range of 2,000-20,000 rpm, and the second rotational speed is within the range of 1,000-7,000 rpm. Preferably, the first rotational speed is within the range of 5,000-8,000 rpm, and the second rotational speed is within the range of 1,000-3,000 rpm. Generally speaking, the speed ratio between the first rotational speed and the second rotational speed is within the range of 1.5-15. Preferably, the speed ratio between the first rotational speed and the second rotational speed is within the range of 1.67-6.

In this manner, beans provided in the upper cavity of the housing 12 can be cut into very small particles by the blade 206 at a relatively high speed. Subsequently, the small particles can enter into the space between the stationary milling disc 208 and the rotary milling disc 210 via the holes in the rotary milling disc 210 to be milled by the ribs 208a, 210a at a relatively low rotational speed, resulting in an efficient milling process without jamming and in an improved taste of the soymilk thus prepared.

Those skilled in the art can readily understand that the blade 206 of the first embodiment of the present invention also can be directly mounted on the sun gear and rotated thereby.

In a simple variation of the first embodiment, the aforementioned rotary milling disc 210 may be fixedly mounted on the output shaft 2023 of the motor 202; the sun gear 216 may be rotatably mounted on the output shaft 2023 and driven by three external gears 214; and the blade 206 is driven by the sun gear 216.

As a substitute for the above planetary gear drive mechanism, another gear drive mechanism may comprise a motor, a first gear fixedly mounted on the output shaft of the motor, a second gear fixedly mounted on another output shaft parallel to the output shaft of the motor and engaging the first gear, a blade fixedly mounted on the output shaft of the motor, and a rotary milling disc fixedly mounted on said another output shaft. In this variant, the number of teeth of the second gear is larger than that of the first gear. Preferably, the second gear has 1.5-15 times as many teeth as the first gear. More preferably, the second gear has 1.67-6 times as many teeth as the first gear. In this manner, a decelerator(?) is constituted by the first gear and the second gear. Conversely, the first gear and the second gear also can constitute an accelerator as long as the second gear is fixedly mounted on the output shaft of the motor while the first gear is fixedly mounted on said another output shaft and driven by the first gear. Meanwhile, the blade is driven by the first gear, and the rotary milling disc is driven by the motor. From this substitution, those skilled in the art can understand that the object of the first embodiment of the present invention also can be realized by the

transmission assembly comprising a pair of engaging gears and a shaft configuration respectively supporting the gears and driving the blade and the rotary milling disc thereon.

Another variant of the first embodiment may comprise a motor, a first gear fixedly mounted on the output shaft of the motor, a second gear spaced from the first gear and fixedly mounted on the output shaft of the motor, a third gear fixedly mounted on a second shaft parallel to the output shaft of the motor and engaging the first gear, a fourth gear fixedly mounted on a third shaft parallel to the output shaft of the motor and engaging the second gear, a blade fixedly mounted on the second shaft and driven thereby, and a rotary milling disc fixedly mounted on the third shaft and driven thereby. In this variant, the speed ratio between the first gear and the third gear is configured such that the rotational speed of the blade is within the range of 2,000-20,000 rpm and preferably within the range of 5,000-8,000 rpm; and the speed ratio between the second gear and the fourth gear is configured such that the rotational speed of the rotary milling disc is within the range of 1,000-7,000 rpm and preferably within the range of 1,000-3,000 rpm, and at the same time lower than the rotational speed of the blade. This variation means that more gears combined with corresponding shaft configurations also can achieve the object of the first embodiment of the present invention.

Those skilled in the art can also readily conceive that the belt drive mechanism including at least two pulleys can be used to achieve the purpose of the first embodiment of the present invention.

By virtue of the technical solutions of the first embodiment and other variations, the blade 206 and the rotary milling disc 210 can be driven by the motor 202 to rotate simultaneously.

Figs. 1 and 5-9 illustrate a grinding mechanism 300 in accordance with the second embodiment of the present invention. Elements other than the grinding mechanism 300 are identical or similar to those used in the first embodiment, which will not be further described.

The grinding mechanism 300 comprises a motor 302, a miller 304 including a rotary milling disc 306 and a stationary milling disc 308, a blade 310 fixedly connected with an upper cover 312, a rotor 314 rotatable together with the rotary milling disc 306, another rotor 316 rotatable together with the blade 310, a bottom cover 318 for covering the rotor 314, and a lower cover 319 for covering the rotor 316. During installation, the bottom cover 318, the rotor 314, the rotary milling disc 306, the stationary milling disc 308, the lower cover 319, the rotor 316 and the upper cover 312 with the blade 310 are assembled together on the output shaft 3023 of the motor 302 one after another. Each element will be described in detail as follows.

The body 3021 of the motor 302 can be fixedly provided within the lower cavity of the housing 12, as shown in Fig. 1, such that the output shaft 3021 of the motor 302 upwardly passes through the through-hole defined in the intermediate wall 12d and is substantially upright in the upper cavity of the housing 12. The stationary milling disc 308 and the rotary milling disc 306 are generally disc-shaped and may be made of metal, such as stainless steel. Specifically, the upper surface of the rotary milling disc 306 is provided with a plurality of oblique ribs 306a around a central through-hole 306b thereof. The space defined by every two ribs 306a becomes narrower and narrower from the outermost ends of the ribs 306a to the innermost ends thereof. Moreover, the innermost ends of ribs 306a are at a distance from the center of the rotary milling disc 306, and thus a central collecting area 306c is formed.

An annular wall 320 downwardly protruding from the lower surface of the rotary milling disc 306 extends circumferentially around the central through hole 306b, which annular wall can be an integral part of the rotary milling disc 306 or, alternatively, can be separately made and then fixed to the lower surface of the rotary milling disc 306 by fasteners such as bolts or by welding. The inner surface of the annular wall 320 is uniformly provided with a plurality of projections 320a. The stationary milling disc 308 is positioned on the upper side of the rotary milling disc 306 and is also provided with a plurality of oblique ribs 308a on the lower surface thereof which can mate with the ribs 306a on the rotary milling disc 306 to mill beans when the rotary milling disc 306 is rotated with respect to the stationary milling disc 308. The above mentioned ribs 306a, 308a could also be referred to as milling teeth.

The rotor 314 is fixedly mounted on the output shaft 3023 of the motor 302 and received within the cavity defined by the annular wall 320 on the rotary milling disc 306. Specifically, the rotor 314 has a center portion 3141 and a plurality of engagement portions

3143 outwardly extending from the center portion 3141. Moreover, each of the engagement portions 3143 generally has a finger-like shape, and includes a first portion 3143a and a second portion 3143b pivotally connected with the first portion 3143a. In this way, the second portion 3143b is disengaged from the projection 320a so as to release the annular wall 320 when the rotor 314 is rotated in the counterclockwise direction, and the second portion 3143b is engaged with the projection 320a so as to cause the annular wall 320 to rotate when the rotor 314 is rotated in the clockwise direction.

In more detail, the engagement portion 3143 has a streamlined shape and, more particularly, is smoothly curved in the clockwise direction. The working principle is very similar to that of the finger of the palm. In the case of the rotor 314 rotating in the

counterclockwise direction at a certain rotational speed, the engagement portion 3143 will try to maintain its extended condition, but the second portion 3143b will tend to pivot toward the first portion 3143a once the rear side of the second portion 3143b comes into contact with the projections 320a on the annular wall 320. In the case of the rotor 314 rotating in the clockwise direction at a certain rotational speed, the engagement portion 3143 will try to maintain its extended condition and then the front side of the second portion 3143b will come into engagement with the projection 320a on the annular wall 320, since the direction of the relative motion of the annular wall 320 is opposite to the pivotal direction of the second portion 3143b.

Furthermore, a bottom cover 318 is provided on the outer periphery of the annular wall 320 to cover the rotor 314.

The blade 310 can be integrally made of metal, such as stainless steel, which may comprise a circular portion 3101 defining a hole 3103 at the center thereof and three branches 3105 extending from and being uniformly distributed around the circular portion 3101. In more detail, the extreme end portions of these branches 3105 are slightly bent upward. The blade 310 is fixedly connected to the upper cover 312 on the output shaft 3023 of the motor 302. Preferably, an end cap can be threaded on the end of the output shaft 3023 of the motor 302 so as to prevent the blade 310 from falling off.

Said upper cover 312 is uniformly provided with a plurality of projections 312a on its inner surface.

The rotor 316 is fixedly mounted on the output shaft 3023 of the motor 302 and received within the cavity defined by the upper cover 312 fixedly connected with the blade 310. Specifically, the rotor 316 has a center portion 3161 and a plurality of engagement portions 3163 outwardly extending from the center portion 3161. Moreover, each of the engagement portions 3163 generally has a finger-like shape, and includes a first portion 3163a and a second portion 3163b pivotally connected with the first portion 3163 a. In this way, the second portion 3163b is engaged with the projection 312a so as to cause the upper cover 312 to rotate when the rotor 316 is rotated in the counterclockwise direction, and the second portion 3163b is disengaged from the projection 312a so as to release the upper cover 312 when the rotor 316 is rotated in the clockwise direction.

In more detail, the engagement portion 3163 has a streamlined shape, and more particularly is smoothly curved in the counter clockwise direction. The working principle is very similar to that of the finger of the palm. In the case of this rotor 316 rotating in the counterclockwise direction at a certain rotational speed, the engagement portion 3163 will try to maintain its extended condition and then the front side of the second portion 3163b will come into engagement with the projection 312a on the inner surface of the upper cover 312 since the direction of the relative motion of the upper cover 312 is opposite to the pivotal direction of the second portion 3163b. In the case of the rotor 316 rotating in the clockwise direction at a certain rotational speed, the engagement portion 3163 will try to maintain its extended condition but the second portion 3163b will tend to pivot toward the first portion 3163a once the rear side of the second portion 3163b comes into contact with the projections 312a on the upper cover 312.

Furthermore, the lower cover 319 is provided on the outer periphery of the upper cover 312 to cover the rotor 316.

Those skilled in the art can readily understand that the rotor 314 within the cavity defined by the annular wall 320 and another rotor 316 within the cavity defined by the upper cover 312 can be interchanged in the above embodiment.

It can be readily understood by those skilled in the art that the mechanism constituted by the annular wall 320 and the rotor 314 and the mechanism constituted by the upper cover 312 and the rotor 316 are ratchet-like mechanisms. Also, it can be understood that the second embodiment of the present invention is achieved by two reversely arranged ratchet-like mechanisms, one of which is adapted for driving the blade 310 in a first direction and the other one is adapted for driving the rotary milling disc 306 in a second direction opposite to the first direction. Moreover, unidirectional clutches other than the above mentioned ratchet-like mechanism, such as a roller-type clutch, also can achieve the technical effect of the second embodiment of the present invention. That is, a modification of the second embodiment may comprise a pair of reversely arranged unidirectional clutches, one of which is adapted for driving the blade in a first direction and the other one is adapted for driving the rotary milling disc in a second direction opposite to the first direction.

Specifically, said unidirectional clutch can be an overrunning clutch.

By virtue of the technical solutions of the second embodiment and other variations, the blade 310 and the rotary milling disc 306 can be driven by the motor 302 so as to rotate separately. Preferably, in order to operate this embodiment of the present invention, the soymilk maker 10 as shown in Fig. 1 may further comprise an operation interface, a controller and a rotational speed control circuit. Specifically, the operation interface may include a realistic button physically present on the operation panel on the housing 12 of the soymilk maker 10 or a visual button displayed in a LED screen on the housing 12, which can be depressed by the user. In response to the button being depressed, the controller can generate an electrical signal for changing the current rotational direction of the motor 302 and send it to the rotational speed control circuit. The rotational direction of the motor 302 can be changed by the rotational speed control circuit a very short time(?) after this electrical signal from the controller is received, which could be easily realized by two switchable circuits used to control respectively the clockwise and the counterclockwise rotations of the motor 302 and a delay circuit allowing the motor 302 to stop the rotation in the current direction without any damage, for example. Alternatively, the instruction for changing the current direction of rotation of the motor 302 can be prestored in the controller; for instance, the rotational direction of the motor 302 can be automatically changed on condition that the time period elapsed after starting of the motor 302 reaches a predetermined duration, such as 8 minutes. In this case, the operation interface could be omitted. Preferably, in order to cut beans efficiently, the rotational speed of the blade 310 should be higher than that of the rotary milling disc 306. Moreover, since the cutting of the beans by the blade 310 usually takes place before the milling of the beans by the miller 304, the prestored first rotational speed is usually higher than the prestored second rotational speed.

After the motor 302, the miller 304 and the blade 310 have been assembled to an assembly as shown in Fig. 5, the blade 310 is positioned right above the rotary milling disc 306. Hence, the first plane in which the blade 310 is rotatable is spaced from and extends parallel to the second plane in which the rotary milling disc 306 is rotatable.

When the motor 302 is activated and rotated in the counterclockwise direction at the first rotational speed, the blade 310 is driven to rotate while the rotary milling disc 306 is immovable. When the predetermined time duration is reached, the motor 302 is rotated in the clockwise direction at the second rotational speed, and thus the rotary milling disc 306 is driven to rotate while the blade 310 is immovable. Specifically, the first rotational speed is within the range of 2,000-20,000 rpm, and the second rotational speed is within the range of 1,000-7,000 rpm. Preferably, the first rotational speed is within the range of 5,000-8,000 rpm, and the second rotational speed is within the range of 1,000-3,000 rpm.

In this manner, beans provided in the upper cavity of the housing 12 can be cut into very small particles by the blade 310 at a relatively high speed. Subsequently, the small particles can enter into the space between the stationary milling disc 308 and the rotary milling disc 306 via the holes in the stationary milling disc 308 to be milled by these ribs 306a, 308a at a relatively low rotational speed, resulting in an efficient milling process without jamming and in an improved taste of the soymilk thus prepared.

It should be noted that the above described embodiments are given for describing rather than limiting the invention, and it is to be understood that modifications and variations may be resorted to without departing from the spirit and scope of the invention as those skilled in the art readily understand. Such modifications and variations are considered to be within the scope of the invention and the appended claims. The protection scope of the invention is defined by the accompanying claims. In addition, any of the reference numerals in the claims should not be interpreted as a limitation to the claims. Use of the verb

"comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The indefinite article "a" or "an" preceding an element or step does not exclude the presence of a plurality of such elements or steps.