Patent Description:
As science and technology is developed continuously and people's living standard is improved continuously, food processors with a double-shaft beating function, such as wall breaking machines and soybean milk machines, etc., are applied more and more widely. In such a food processor, an electric motor rotates and drives two shafts arranged concentrically, and two blades in a mixing cup are in a transmission connection with the two shafts respectively, so that the two blades perform beating operation simultaneously.

At present, the electric motor generally employs an external transmission mechanism to rotate and drive the two shafts arranged concentrically. Consequently, when the assembler assembles the food processor, the transmission mechanism may be injured or even damaged easily. Of course, after the food processor is assembled, interference to the transmission assembly may occur owing to loosening of other parts (e.g., electric wires) in the food processor. As a result, the normal operation of the transmission assembly is affected, and the service life of the entire machine is shortened.

<CIT> discloses a fermentation tank mixing arrangement with a coaxial double-oar submersible agitator. The submersible motor comprises an inner shaft, an outer shaft, a first bevel gear, a second bevel gear and two sets of blades with opposite mounting directions. The first bevel gear and the second bevel gear are disposed inside the submersible motor, the edge of the rotor inside the submersible motor is provided with two sets of conical teeth respectively with the first bevel gear and the second bevel gear in order to allow different rotation speeds of the inner shaft and the outer shaft. The first bevel gear and the second bevel gear are synchronously rotated by the inner rotor of the submersible motor. Further state of the art is known from <CIT>.

To overcome the above-mentioned drawbacks or defects in the prior art, the present disclosure provides an electric motor and a food processor. The electric motor can effectively protect the gear transmission mechanism, is helpful for improving the reliability and service life of the gear transmission mechanism, and thereby improve the reliability and service life of the food processor.

To attain the object described above, the present disclosure provides an electric motor for a food processor, which comprises a front end cover and a rotary output shaft extending out of the front end cover from an inner cavity of the electric motor, wherein the rotary output shaft comprises an inner rotary shaft and an outer rotary shaft that are arranged concentrically, a gear transmission mechanism is further provided inside the inner cavity of the electric motor, and the gear transmission mechanism is in a transmission connection with the inner rotary shaft and the outer rotary shaft respectively.

The gear transmission mechanism comprises a gear bracket and gear transmission components, wherein the gear transmission components are accommodated in an inner cavity of the gear bracket, and the gear bracket is disposed in the inner cavity of the electric motor and fixedly mounted on the front end cover, wherein the inner rotary shaft extends through a bottom wall and a top wall of the gear bracket sequentially and extends out of a top wall of the front end cover, the outer rotary shaft is concentrically fitted outside the inner rotary shaft and extends out of the top wall of the gear bracket and the top wall of the front end cover, the gear transmission components comprise an inner shaft gear and an outer shaft gear that are fixedly fitted around outer circumference walls of the inner rotary shaft and the outer rotary shaft respectively, and the inner shaft gear and the outer shaft gear are in a transmission connection with each other and wherein the gear transmission mechanism comprises an intermediate gear, which is pivotally mounted on a side wall of the gear bracket and engaged with the inner shaft gear and the outer shaft gear respectively, wherein the gear bracket comprises a first half-sectional bracket portion and a second half-section bracket portion that are sectioned along a half section defined by a central axis of the intermediate gear and a concentric axis of the inner rotary shaft and the outer rotary shaft that orthogonally cross each other.

Optionally, the gear bracket is an enclosed cubical bracket.

Optionally, the outer circumference walls of the inner rotary shaft and the outer rotary shaft are respectively provided with an inner bearing pack and an outer bearing pack respectively arranged on the bottom wall and the top wall of the gear bracket, the rotary shaft of the intermediate gear is provided with an intermediate bearing pack mounted on the side wall of the gear bracket.

Optionally, a bottom end of the inner shaft gear abuts against a top end of the inner bearing pack, a top end of the outer shaft gear abuts against a bottom end of the outer bearing pack, and the intermediate gear is engaged with the inner shaft gear and the outer shaft gear respectively.

Optionally, all of the intermediate gear, the inner shaft gear, and the outer shaft gear are cone gears, and the horizontal inclination angles of the cone generatrices of the inner shaft gear and the outer shaft gear are not smaller than <NUM>° and not greater than <NUM>°.

Optionally, the rotation speed ratio of the outer rotary shaft to the inner rotary shaft is not smaller than <NUM>/<NUM> and not greater than <NUM>.

The present disclosure further provides a food processor, which comprises an inner shaft stirring blade assembly, an outer shaft stirring blade assembly, and an electric motor, wherein the inner rotary shaft drives the inner shaft stirring blade assembly to rotate, and the outer shaft stirring blade assembly is in a transmission connection with the outer rotary shaft.

With the above technical scheme, in the electric motor provided in the present disclosure, the inner rotary shaft and the outer rotary shaft, which are arranged concentrically, extend out of the front end cover of the electric motor, the inner rotary shaft and the outer rotary shaft are in a transmission connection via the gear transmission mechanism, and the gear transmission mechanism is accommodated in the inner cavity of the electric motor. Thus, the gear transmission mechanism is integrated in the electric motor, and is effectively protected. As a result, not only a situation of injury or damage to the gear transmission mechanism occurring owing to the carelessness of the assembler can be prevent, but also the interference to the double-shaft transmission assembly can be prevented when other parts (e.g., electric wires) in the food processor get loose. In that way, the reliability and service life of the gear transmission mechanism can be greatly improved, and the reliability and service life of the food processor can be improved.

Other features and advantages of the present disclosure will be further detailed in the detailed description hereunder.

The accompanying drawings are provided here to facilitate further understanding on the present disclosure, and constitute a part of this document. They are used in conjunction with the following detailed description to explain the present disclosure, but shall not be comprehended as constituting any limitation to the present disclosure. In the figures:.

Hereunder some detailed description of the present disclosure will be detailed with reference to the accompanying drawings. It should be understood that the detailed description described here are only provided to describe and explain the present disclosure rather than constitute any limitation to the present disclosure.

It is noted that the examples and the features in the examples in the present disclosure can be combined freely, provided that there is no confliction between them.

In the present disclosure, unless otherwise specified, the words that denote directions or orientations, such as "above", "below", "top", and "bottom", etc., are usually used to describe the relative position relations among the components with respect to the direction as set forth in the accompanying drawings or the vertical, plumb, or gravity direction.

Hereunder the present disclosure will be detailed in examples with reference to the accompanying drawings.

In one aspect, the present disclosure provides an electric motor. As shown in <FIG>, the electric motor comprises a front end cover <NUM> and a rotary output shaft extending out of the front end cover <NUM> from an inner cavity of the electric motor, wherein the rotary output shaft comprises an inner rotary shaft <NUM> and an outer rotary shaft <NUM> that are arranged concentrically, a gear transmission mechanism is further provided inside the inner cavity of the electric motor, and the gear transmission mechanism is in a transmission connection with the inner rotary shaft <NUM> and the outer rotary shaft <NUM> respectively. Optionally, the rotation speed ratio of the outer rotary shaft <NUM> to the inner rotary shaft <NUM> is not smaller than <NUM>/<NUM> and not greater than <NUM>.

In another aspect, the present disclosure provides a food processor. The food processor comprises an inner shaft stirring blade assembly, an outer shaft stirring blade assembly, and an electric motor, wherein the inner rotary shaft <NUM> drives the inner shaft stirring blade assembly to rotate, and the outer shaft stirring blade assembly is in a transmission connection with the outer rotary shaft <NUM>. Wherein the food processor may be a wall breaking machine, natural juice extractor, juice extractor, soybean milk machine, agitator, or any other household appliance, as long as the food processor is provided with an electric motor and has a food beating function.

In the technical scheme of the present disclosure, the inner rotary shaft <NUM> and the outer rotary shaft <NUM> that are arranged concentrically respectively rotate and drive the inner shaft stirring blade assembly and the outer shaft stirring blade assembly, and the inner shaft stirring blade assembly and the outer shaft stirring blade assembly are disposed in the mixing cup of the food processor, the rotor of the electric motor rotates and drives the rotary output shaft to drive the double stirring blade assembly (i.e., the inner shaft stirring blade assembly and the outer shaft stirring blade assembly) to operate simultaneously so as to cut and beat the food accommodated in the mixing cup. Wherein, the double shaft transmission mechanism composed of the inner rotary shaft <NUM> and the outer rotary shaft <NUM> in transmission connection is disposed in the inner cavity of the electric motor, i.e., the double shaft transmission mechanism is integrated in the electric motor. Thus, when the assembler assembles the food processor, the double shaft transmission mechanism is protected effectively, and thereby a situation of injury or damage to the double shaft transmission mechanism owing to the carelessness of the assembler can be avoided; in addition, after the food processor is assembled, interference to the double shaft transmission assembly can be effectively prevented when other parts (e.g., electric wires) in the food processor get loose. In that way, not only the reliability and service life of the double shaft transmission mechanism can be improved so as to improve the reliability and service life of the entire machine, but also the yield of the food processor can be effectively improved. Moreover, by integrating the double shaft transmission mechanism in the electric motor, the assembling speed of the assembler can be effectively improved, i.e., the assembler only has to assemble the electric motor integrated with the double shaft transmission mechanism into the food processor, without assembling the double shaft transmission mechanism additionally. Thus, the production efficiency of the food processor can be greatly improved. Of course, by integrating the double shaft transmission mechanism inside the electric motor, an additional internal space for accommodating the double shaft transmission mechanism is omitted in the food processor. That is to say, the internal space occupied in the food processor can be effectively reduced, the entire machine is smaller and more compact; in addition, the transportation and storage cost of the food processor can be reduced since the footprint of the entire machine is reduced.

Specifically, the double shaft transmission mechanism is a gear transmission mechanism. In such an arrangement, the gear transmission mechanism has a more outstanding technical effect than other transmission structures, such as belt-wheel transmission mechanisms. Hereunder the technical effect of the double shaft transmission mechanism serving as a gear transmission mechanism will be described with a belt-wheel transmission mechanism as a comparative example. Specifically, a gear transmission mechanism realizes transmission by means of gear engagement, while a belt-wheel transmission mechanism requires a transmission belt between the wheels to realize transmission. Therefore, compared with a belt-wheel transmission mechanism, a gear transmission mechanism has a smaller and more compact structure since it doesn't require a transmission belt, and thereby the electric motor or even the entire machine is smaller and more compact. Furthermore, the transmission belt in a belt-wheel transmission mechanism gets slack gradually after years of operation, resulting in degradation or even loss of the transmission capability; in contrast, such a situation doesn't occur in a gear transmission mechanism. Therefore, compared with a belt-wheel transmission mechanism, the operation reliability of a gear transmission mechanism is higher, and the service life of a gear transmission mechanism is longer. Of course, since a gear transmission mechanism doesn't require a transmission belt for linkage, the transmission efficiency is higher.

Optionally, the electric motor comprises an inner rotor <NUM> and an outer stator <NUM>, and the rotary shaft of the inner rotor <NUM> is the inner rotary shaft <NUM>, as shown in <FIG>. Therefore, compared with an electric motor with an outer rotor, an electric motor with an inner rotor <NUM> is smaller and more compact, and occupies a smaller space. Furthermore, the electric motor comprises a back end cover <NUM> fixed to the back end of the outer stator <NUM>.

Specifically, the gear transmission mechanism comprises a gear bracket <NUM> and a gear transmission component accommodated in the inner cavity of the gear bracket <NUM>, the gear bracket <NUM> is disposed in the inner cavity of the electric motor and fixedly mounted on the front end cover <NUM>, as shown in <FIG>. Thus, by connecting the gear bracket <NUM> to the front end cover <NUM> fixedly, the gear bracket <NUM> and the front end cover <NUM> forms an integral piece, so that the gear transmission components in the inner cavity of the bracket can carry out transmission smoothly, and thereby the inner rotary shaft <NUM> can smoothly transfer the rotational kinetic energy to the outer rotary shaft <NUM> via the gear transmission component. That is to say, the transmission between the inner rotary shaft <NUM> and the outer rotary shaft <NUM> is more smooth and stable, and the user experience can be improved. Of course, the smooth and stable transmission of the gear transmission components can effectively reduce the operation noise produced during gear transmission and is helpful for improving user experience. Moreover, since the gear transmission mechanism is accommodated in the inner cavity of the front end cover <NUM>, it doesn't affect the transmission efficiency of the rotor and the stator in the electric motor.

Furthermore, as shown in <FIG>, the gear bracket <NUM> is an enclosed cubical bracket. Specifically, to improve the reliability and service life of the gear transmission components, usually a lubricant is applied on the gear transmission components. Therefore, by configuring the gear bracket <NUM> into an enclosed bracket, interference to other parts in the electric motor owing to dripping or splashing of the lubricant applied on the gear transmission component can be effectively avoided, and the reliability and service life of the electric motor can be improved. Moreover, the gear bracket <NUM> may be in a spheroidal shape or other shape, besides cubical shape.

The inner rotary shaft <NUM> extends through a bottom wall and a top wall of the gear bracket <NUM> sequentially and extends out of a top wall of the front end cover <NUM>, the outer rotary shaft <NUM> is concentrically fitted outside the inner rotary shaft <NUM> and extends out of the top wall of the gear bracket <NUM> and the top wall of the front end cover <NUM>, as shown in <FIG>, the gear transmission components comprise an inner shaft gear <NUM> and an outer shaft gear <NUM> that are fixedly fitted around outer circumference walls of the inner rotary shaft <NUM> and the outer rotary shaft <NUM> respectively, and the inner shaft gear <NUM> and the outer shaft gear <NUM> are in a transmission connection with each other.

Furthermore, the gear transmission mechanism further comprises an intermediate gear <NUM> as shown in <FIG>, which is pivotally mounted on a side wall of the gear bracket <NUM> and engaged with the inner shaft gear <NUM> and the outer shaft gear <NUM> respectively. In such an arrangement, the outer rotary shaft <NUM> can rotate in a reverse direction with respect to the inner rotary shaft <NUM>, and thereby the inner shaft stirring blade assembly and the outer shaft stirring blade assembly have rotation directions reversed to each other. Thus, the rotation speeds of the double stirring blade assembly in directions reversed to each other are stacked, and the cutting speed of the double stirring blade assembly with respect to the food particles is greatly increased. Therefore, the food can be cut to a finer state, and the rate of juice extraction from the food and the drinking taste can be improved. In other words, for an electric motor in which the inner rotary shaft <NUM> and the outer rotary shaft <NUM> rotate in directions reverse to each other, by greatly decreasing the rotation speed of the rotor <NUM> in the electric motor (e.g., to <NUM>/<NUM> of the original rotation speed), a food beating and crushing effect can also be attained even when the inner rotary shaft <NUM> and the outer rotary shaft <NUM> rotate in the same direction. By decreasing the rotor speed, the food processor can achieve the original food crushing effect while the noise produced during the operation of the main body of the electric motor is reduced. Furthermore, the decreased rotor speed can result in decreased rotation speed of the double stirring blade assembly, and the vibration and noise produced during the food cutting operation of the double stirring blade assembly can be reduced.

Specifically, all of the intermediate gear <NUM>, the inner shaft gear <NUM>, and the outer shaft gear <NUM> are cone gears. Wherein the intermediate gear <NUM>, the inner shaft gear <NUM>, and the outer shaft gear <NUM> may be straight-tooth cone gears or skewed-tooth cone gears, or other appropriate cone gears, such as arc-tooth cone gears.

In addition, as shown in <FIG>, the horizontal inclination angles of the cone generatrices of the inner shaft gear <NUM> and the outer shaft gear <NUM> shall not be smaller than <NUM>° and not greater than <NUM>° respectively. Wherein the concentric axis of the inner shaft gear <NUM> and the outer shaft gear <NUM> and the central axis of the intermediate gear <NUM> orthogonally cross each other, and the horizontal inclination angle of the cone generatrix of the inner shaft gear <NUM>, the outer shaft gear <NUM> or the intermediate gear <NUM> refers to an acute included angle between the cone generatrix of the gear and the horizontal plane when the gear is placed horizontally (i.e., the central axis of the gear is perpendicular to the horizontal plane). Thus, the sum of the horizontal inclination angle of the cone generatrix of the inner shaft gear <NUM> or the outer shaft gear <NUM> and the horizontal inclination angle of the cone generatrix of the intermediate gear <NUM> shall be <NUM>°. In that way, if the horizontal inclination angles of the cone generatrices of the inner shaft gear <NUM> and the outer shaft gear <NUM> are <NUM>° respectively, the horizontal inclination angle of the cone generatrix of the intermediate gear <NUM> is <NUM>°. Optionally, the horizontal inclination angles of the cone generatrices of the inner shaft gear <NUM> and the outer shaft gear <NUM> are <NUM>° respectively. Thus, the inner shaft gear <NUM>, the outer shaft gear <NUM>, and the intermediate gear <NUM> can be designed to be interchangeable, i.e., the assembler has to mount gears to the positions where gears are to be mounted, without speeding any additional time and effort to artificially judge the types of the gears and the corresponding mounting positions. Furthermore, the horizontal inclination angles of the cone generatrices of the inner shaft gear <NUM> and the outer shaft gear <NUM> are greater than <NUM>° and not greater than <NUM>° respectively, i.e., the horizontal inclination angle of the cone generatrix of the intermediate gear <NUM> is smaller than <NUM>°. Thus, the intermediate gear <NUM> may be designed to be smaller, and the height of the gear bracket <NUM> may be designed to be smaller, and thereby the structure of the electric motor can be smaller and more compact. Of course, the space occupied by the electric motor is smaller, the accommodating space of the food processor can be reduced, and thereby the transportation and storage cost of the entire machine can be reduced.

It should be noted that there are a variety of ways to arrange the gear transmission components. For example, the above-mentioned inner shaft gear <NUM> and outer shaft gear <NUM> are engaged and carry out transmission via the intermediate gear <NUM>; or an outer gear may be provided on the inner rotary shaft <NUM>, an inner gear may be formed on the bottom end of the outer rotary shaft <NUM>, a connecting gear may be pivotally arranged on the bottom wall of the gear bracket <NUM> and engaged with the inner gear and the outer gear respectively.

Optionally, the speed ratio of the outer rotary shaft <NUM> to the inner rotary shaft <NUM> shall not be smaller than <NUM>/<NUM> and not greater than <NUM>. Thus, the food accommodated in the mixing cup can be cut to a finer state by the double stirring blade assembly, and thereby a better drinking state can be obtained while more juice can be squeezed from the food, and the user experience can be improved greatly. Furthermore, the speed ratio of the outer rotary shaft <NUM> to the inner rotary shaft <NUM> shall not be smaller than <NUM>/<NUM> and not greater than <NUM>/<NUM>. It can be understood that the higher the speed ratio of the outer rotary shaft <NUM> to the inner rotary shaft <NUM> is, the better the food beating and crushing effect of the double stirring blade assembly is; but the speed of impact of the food on the mixing cup body under the driving action of the high-speed double stirring blade assembly will be increased, and thereby the noise produced during the operation of the entire machine will be increased. Therefore, by confining the speed ratio of the outer rotary shaft <NUM> to the inner rotary shaft <NUM> to the above-mentioned preferred range, not only a good food beating and crushing effect can be attained, but also the noise during the beating operation can be reduced.

To facilitate the assembler to mount the gear transmission components into the gear bracket <NUM>, as shown in <FIG>, the gear bracket <NUM> comprises a first half-sectional bracket portion and a second half-section bracket portion that are sectioned along a half section defined by the central axis of the intermediate gear <NUM> and the concentric axis of the inner rotary shaft <NUM> and the outer rotary shaft <NUM> that are orthogonally cross each other. Specifically, the outer rotary shaft <NUM> with the outer shaft gear <NUM> is fitted around the inner rotary shaft <NUM> with the inner shaft gear <NUM>, as shown in <FIG> and <FIG>, and then the inner rotary shaft <NUM> and the outer rotary shaft <NUM> are mounted to corresponding positions in the first half-sectional bracket portion, as shown in <FIG>; the intermediate gear <NUM> is engaged with the outer shaft gear <NUM> and the inner shaft gear <NUM> respectively by utilizing an external space, then the intermediate gear <NUM> is turned around the concentric axis of the outer rotary shaft <NUM> and the inner rotary shaft <NUM> that serves as a central axis, and thereby the intermediate gear <NUM> is mounted to a corresponding position in the first half-sectional bracket portion, as shown in <FIG>; finally, the second half-section bracket portion and the first half-sectional bracket portion are assembled to form the gear bracket <NUM>. With such a ground-breaking assembling method, the assembler can mount the gear transmission components into the gear bracket <NUM> easily, and the assembling efficiency is high.

Optionally, the outer circumference walls of the inner rotary shaft <NUM> and the outer rotary shaft <NUM> are respectively provided with an inner bearing pack <NUM> and an outer bearing pack <NUM> that are respectively arranged on the bottom wall and top wall of the gear bracket <NUM>, the rotary shaft of the intermediate gear <NUM> is provided with an intermediate bearing pack <NUM> mounted on the side wall of the gear bracket <NUM>, as shown in <FIG> and <FIG>. Thus, by arranging the inner bearing pack <NUM> between the outer circumference wall of the inner rotary shaft <NUM> and the gear bracket <NUM>, radial support is provided to the inner rotary shaft <NUM>, the accuracy of rotation of the inner rotary shaft <NUM> can be improved, and thereby a situation of instable transmission of the inner rotary shaft <NUM> can be avoided; moreover, in that way, the friction coefficient between the inner rotary shaft <NUM> and the gear bracket <NUM> in the process of rotation can be effectively decreased, the inner rotary shaft <NUM> can rotate smoothly in the gear bracket <NUM>, and the user experience can be improved. Likewise, by arranging the outer bearing pack <NUM> between the outer circumference wall of the rotating shaft <NUM> and the gear bracket <NUM> and arranging the intermediate bearing pack <NUM> between the outer circumference wall of the rotary shaft of the intermediate gear <NUM> and the gear bracket <NUM>, the accuracy of rotation of the outer rotary shaft <NUM> and the rotary shaft of the intermediate gear <NUM> can be improved, the outer rotary shaft <NUM> and the rotary shaft of the intermediate gear <NUM> can rotate smoothly in the gear bracket <NUM>, and thereby the user experience can be improved.

In addition, as shown in <FIG>, the bottom end of the inner shaft gear <NUM> abuts against the top end of the inner bearing pack <NUM>, the top end of the outer shaft gear <NUM> abuts against the bottom end of the outer bearing pack <NUM>, and the intermediate gear <NUM> is engaged with the inner shaft gear <NUM> and the outer shaft gear <NUM> respectively. Thus, a situation of axial displacement (i.e., upward and downward movement) of the outer shaft gear <NUM> and the inner shaft gear <NUM> can be effectively prevented during the operation of the electric motor, the transmission stability and reliability of the gear transmission mechanism can be improved, and thereby the reliability of the entire machine can be improved.

It should be noted particularly that the other components and their functions of the electric motor and food processor according to the examples of the present disclosure are well known to those having ordinary skilled in the art, and will not be detailed here to reduce redundancy.

While the present disclosure is described above in some preferred examples, the present disclosure is not limited to those preferred embodiments.

In addition, it should be noted that the specific technical features described in above specific detailed description may be combined within the scope of the invention. To avoid unnecessary repetition, various possible combinations are not described specifically in the present disclosure.

Claim 1:
An electric motor for a food processor, comprising
a front end cover (<NUM>);
an output rotary shaft, extending out of the front end cover (<NUM>) from an inner cavity of the electric motor, wherein the output rotary shaft comprises an inner rotary shaft (<NUM>) and an outer rotary shaft (<NUM>) that are arranged concentrically; and
a gear transmission mechanism, provided inside the inner cavity of the electric motor, and the gear transmission mechanism is in a transmission connection with the inner rotary shaft (<NUM>) and the outer rotary shaft (<NUM>), wherein the gear transmission mechanism comprises a gear bracket (<NUM>) and a gear transmission component, and the gear bracket (<NUM>) is disposed in the inner cavity of the electric motor and fixedly mounted on the front end cover (<NUM>) , the outer rotary shaft (<NUM>) is concentrically fitted outside the inner rotary shaft (<NUM>) and the top wall of the front end cover (<NUM>), the gear transmission component comprises an inner shaft gear (<NUM>) and an outer shaft gear (<NUM>), the inner shaft gear (<NUM>) is fixedly fitted around an outer circumference wall of the inner rotary shaft (<NUM>) , and the inner shaft gear (<NUM>) and the outer shaft gear (<NUM>) are in a transmission connection with each other and,
wherein the gear transmission mechanism comprises an intermediate gear (<NUM>), which is pivotally mounted on a side wall of the gear bracket (<NUM>) and engaged with the inner shaft gear (<NUM>) and the outer shaft gear (<NUM>) respectively,
wherein the gear transmission component is accommodated in an inner cavity of the gear bracket (<NUM>),
wherein the inner rotary shaft (<NUM>) extends through a bottom wall and a top wall of the gear bracket (<NUM>) sequentially and extends out of a top wall of the front end cover (<NUM>),
wherein the outer rotary shaft (<NUM>) extends out of the top wall of the gear bracket (<NUM>),
wherein the outer shaft gear (<NUM>) is fixedly fitted on an outer circumference wall of the outer rotary shaft (<NUM>),
wherein the gear bracket (<NUM>) comprises a first half-sectional bracket portion and a second half-section bracket portion that are sectioned along a half section, wherein the half section is defined by a central axis of the intermediate gear (<NUM>) and a concentric axis of the inner rotary shaft (<NUM>) and the outer rotary shaft (<NUM>), wherein the two axes orthogonally cross each other.