WO2021115119A1

WO2021115119A1 - A gear transmission device

Info

Publication number: WO2021115119A1
Application number: PCT/CN2020/131235
Authority: WO
Inventors: Gee Chung Jonathan CHEUNG; Hoi Yue Yung
Original assignee: Inovo Robotics (Hk) Limited
Priority date: 2019-12-13
Filing date: 2020-11-24
Publication date: 2021-06-17
Also published as: GB2604536A; GB202208113D0

Abstract

A gear transmission device (10) such as a gearbox. The gearbox comprises a mechanism (12) having a central axis (A-A) aligned with a central axis of the device (10). The mechanism (12) comprises a gear system (20) configured to transmit a rotational force from a motor to a plurality of crankshafts (40); the gear system (20) comprises an input gear (22) adapted to be driven by the motor, and one or more gear units (24) operably engage with the input gear (22) for transmitting rotation from the motor to the plurality of crankshafts (40); wherein the plurality of crankshafts (40) comprise a central crankshaft (42) and one or more peripheral crankshafts (44); the central crankshaft (42) being positioned in longitudinal alignment with the central axis (A-A) of the mechanism (12), and the one or more peripheral crankshafts (44) being positioned longitudinally parallel to the central axis (A-A) of the mechanism (12); with the central crankshaft (42) and the peripheral crankshafts (44) being arranged to rotate in a same direction of rotation.

Description

A GEAR TRANSMISSION DEVICE

Technical Field

The invention relates to a power transmission system and particularly, but not exclusively, to a gear transmission device.

Background Art

Transmission systems or devices such as gearboxes are commonly used in machineries for transmitting power from a rotary power source, such as a motor to a load. Power in the form of rotational motion can generally be transmitted via one or more gears or gear trains, and based on their specific configurations, provide variations in speed and torque to the output. One of the primary function of the traditional gearboxes is to increase the output torque of the transmission by reducing the speed of the high-speed input via a fixed gear ratio. Different gearboxes have been designed and developed for various applications such as, in the field of automobiles and robotics, for example. Specialized gearbox designs such as, rotate vector (RV) reducers, which are known for their applications in industrial robots generally comprise a two-staged planetary gear and a cycloidal gear cooperatively connected to provide high transmission efficiency. Yet, one drawback being known for common RV reducers is that they have a relatively limited lifespan. Particularly, wearing, fatigue and/or operation failure at movable parts of the reducers, such as the crankshafts and/or the crankshaft bearings, are known to significantly affect reliability and efficiency of the gear transmissions, which are undesirable.

Technical Problem

An object of the present invention is to provide a novel gear transmission device.

Another object of the present invention is to mitigate or obviate to some degree one or more problems associated with known gearboxes, or at least to provide a useful alternative.

The above objects are met by the combination of features of the main claim; the sub-claims disclose further advantageous embodiments of the invention.

One skilled in the art will derive from the following description other objects of the invention. Therefore, the foregoing statements of object are not exhaustive and serve merely to illustrate some of the many objects of the present invention.

Technical Solution

In one main aspect, the invention provides a gear transmission device. The gear transmission device comprises a mechanism having a central axis aligned with a central axis of the device, the mechanism comprises a gear system configured to transmit a rotational force from a rotary power source to a plurality of crankshafts; the gear system comprises an input gear adapted to be driven by the rotary power source, and one or more gear units operably engageable with the input gear for transmitting rotation from the rotary power source to the plurality of crankshafts; wherein the plurality of crankshafts comprise a central crankshaft and one or more peripheral crankshafts; the central crankshaft being positioned in longitudinal alignment with the central axis of the mechanism, and the one or more peripheral crankshafts being positioned longitudinally parallel to the central axis of the mechanism; with the central crankshaft and the peripheral crankshafts being arranged to rotate in a same direction of rotation.

The summary of the invention does not necessarily disclose all the features essential for defining the invention; the invention may reside in a sub-combination of the disclosed features.

Description of Drawings

The foregoing and further features of the present invention will be apparent from the following description of preferred embodiments which are provided by way of example only in connection with the accompanying figure, of which:

Figure 1 is an exploded schematic diagram showing various components of the gear transmission device in accordance with an embodiment of the present invention;

Figure 2 is a further schematic diagram showing the gear transmission device of Figure 1; and

Figure 3 shows another embodiment of the gear transmission device of the present invention.

Best Mode

The following description is of preferred embodiments by way of example only and without limitation to the combination of features necessary for carrying the invention into effect.

Reference in this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Moreover, various features are described which may be exhibited by some embodiments and not by others. Similarly, various requirements are described which may be requirements for some embodiments but not other embodiments.

It should be understood that the elements shown in the figures may be implemented in various forms or combinations thereof.

In the context of the present invention, the term “gear” is to be given a broad meaning to encompass various types of gear which may include, but are not limited to, spur gears, helical gears, bevel gears, worm gears, screw gears, internal gears or the like configured in any different sizes, number of teeth, helix angles, face widths, etc. A person skilled in the art will appreciate that the present invention shall not be limited to the specific embodiments described and illustrated. Instead, variations to one or more of the structural parts or components of the present invention, which might reasonably be considered applicable in achieving the same technical effect, shall also be encompass. For example, a skilled person may understand that one or more of the gears, gear units and/or gear system as required in one or more of the described embodiments may well be replaceable or work together with one or more mechanical transmission components such as, but are not limited to, a belt and pulley system, for example.

Referring to Figs. 1 and 2, shown is an embodiment of the gear transmission device 10 in accordance with the present invention. The gear transmission device 10, which is more often referred to as a gearbox, a reducer, or a RV reducer in specific terms, may comprise a mechanism 12 with a central axis A-A aligned with, i.e. coincident with, a central axis of the device 10. The mechanism 12 comprises a gear system 20 configured to transmit rotation from one or more rotary power sources, such as but not limited to, an electric motor (not shown) to a plurality of crankshafts 40. In the embodiment as shown in the figures, the plurality of crankshafts 40 may comprise at least a centrally located crankshaft 42 and one or more peripheral crankshafts 44, such as three peripheral crankshafts 44 which are positioned to surround the central crankshaft 42. The plurality of crankshafts 40 including the central crankshaft 42 and the peripheral crankshafts 44 are arranged to rotate in the same direction of rotation. A person skilled in the art will appreciate that the number of crankshafts and particularly, the number of peripheral crankshafts may vary in accordance with the design requirements of the device 10, and therefore, shall not be limited to any specific embodiments described and/or illustrated in the present description.

In one embodiment, the gear system 20 is configured to transmit rotation from the motor to a cycloidal gear system 30 via the plurality of crankshafts 40 whereby the cycloidal gear system 30 and the plurality of crankshafts 40 are operably connected with one another. Preferably, the gear system 20 comprises an input gear 22 operably connected with and arranged to be rotatably driven by the rotary power source such as the motor (not shown). The gear system 20 further comprises one or more gear units 24, e.g. gear trains, arranged to engage the input gear 22 for transmitting rotation from the motor via the input gear 22 and then to the plurality of crankshafts 40. Preferably, the gear units 24 comprise one or more secondary gears 26, and more preferably, one or more tertiary gears 28 interconnecting the input gear 22 and the plurality of crankshafts 40 for power transmission. In one specific embodiment, each of the tertiary gears 28 is arranged to be fixedly connected at a proximal end of a respective one of the plurality of crankshafts 40, such that, when all the tertiary gears 28 are arranged to rotate in the same speed and direction of rotation, the plurality of crankshafts 40 also rotate in a synchronized manner. Optionally, the plurality of crankshafts 40 can be positioned or supported via one or more supporting plates 31, as shown in Figs. 1 and 2. In one embodiment, the supporting plate 31 are provided for preventing precession of the transmission system, i.e. to reduce and/or avoid a change in alignment of the crankshafts with respect to the rotational axis of the device 10, for example.

In one embodiment, the cycloidal gear system 30 may comprise at least one cycloidal gear plate 32 movably connectable with the plurality of crankshafts 40 to allow cycloidal movement of the cycloidal gear plate 32 in response to rotation of the plurality of crankshafts 40. Preferably, the cycloidal gear system 30 may further comprise a second cycloidal gear plate 34 to facilitate motion of the cycloidal gear system 30.

To allow effective transmission of power from the rotary power source to a load, it is preferred that each of the plurality of crankshafts 40, including the central crankshaft 42 and the peripheral crankshafts 44, rotate in the same direction of rotation, and more preferably, at the same speed and/or phase of rotation. In one preferred embodiment, the central crankshaft 42 is positioned to longitudinally align with the central axis A-A of the mechanism 12 for connecting the cycloidal gear system 30 at a substantially central position of the cycloidal gear plate 32; and the peripheral crankshafts 44 are positioned substantially parallel to and surrounding the central crankshaft 42 outwardly offset from the central axis A-A of the body 12 for movably connecting the cycloidal gear system 30 at a peripheral region of the cycloidal gear plate 32.

Referring to the specific embodiment of Figs. 1 and 2, it can be seen that the gear units 24 comprise a plurality of secondary gears 26 with preferably three such secondary gears 26. In this embodiment, the secondary gears 26 are provided in the form of compound secondary gears 26, which are configured to rotatably engage or mesh with, and to surround the centrally located input gear 22. Preferably, each respective larger gears 26a of the secondary gears 26 is positioned to mesh with and be driven by the central input gear 22, such as in the form of a sun and planet gear arrangement, for example. The surrounding secondary gears 26 are all rotatably driven in an opposite direction to that of the driving input gear 22. More preferably, the gear units 24 may further comprise a plurality of tertiary gears 28, such as, but not limited to four tertiary gears 28 as shown in the figures. The tertiary gears 28 are arranged to operably engage with the secondary gears 26, and more preferably, with respective smaller gears 26b of the compound secondary gears 26, for example. In one preferred embodiment, the tertiary gears 28 may comprise a centrally located tertiary gear 28a positioned substantially in axial alignment with the central axis A-A of the mechanism 12, and one or more peripheral tertiary gears 28b positioned adjacent to and/or surrounding the central tertiary gear 28a in meshed engagement with the central tertiary gear 28a and the smaller gears 26b of the compound secondary gears 26, with the peripheral tertiary gears 28b being arranged outwardly offset from, i.e. spaced from, the central axis A-A of the body 12. Preferably, the smaller gear 26b of each of the secondary gears 26 is in a meshed engagement with at least two tertiary gears 28, such as the central tertiary gear 28a and at least one peripheral tertiary gear 28b. In this embodiment, the tertiary gears 28 are driven by the secondary gears 26 to rotate in the same direction of rotation as the input gear 22, i.e. opposite to the direction of rotation of the secondary gears 26. However, it is preferred that the tertiary gears 28 do not directly contact or engage with the input gear 22 to thereby avoid interference to rotation of the tertiary gears 28 by the input gear 22, especially in view of the possible phase difference of rotation which may happen between the tertiary gears 28 and the input gear 22, for example.

Referring to Fig. 3, shown is another embodiment of the present invention. In the description of this embodiment, like numerals are used to denote like or similar parts with respect to the embodiment of Figs. 1 and 2. In this embodiment, the tertiary gears 28 may comprise only the peripheral tertiary gear 28b, i.e. without the central tertiary gear 28a, with the peripheral tertiary gear 28b being positioned offset from the central axis A-A of the mechanism 12. Preferably, the input gear 22, the secondary gears 26 which may comprise but are not limited to three spur gears 26, and the three peripheral tertiary gears 28b are arranged to connect substantially on a same, transverse plane substantially perpendicular to the central axis A-A of the mechanism 12. In this embodiment, the input gear 22 and each of the peripheral tertiary gears 28b are fixedly connected with a proximal end of a respective one of the four crankshafts 40 for directly driving the four crankshafts 40, i.e. for the input gear 22 to fixedly connect the proximal end of the central crankshaft 42 for driving the central crankshaft 42, and each of the tertiary gears 28b to fixedly connect the proximal end of the peripheral crankshaft 44 for driving the peripheral crankshafts. Since the input gear 22 and the three peripheral tertiary gears 28b are rotate in the same direction, the four crankshafts 40 will also rotate in the same direction, i.e. the same direction of rotation as the input gear 22 as driven by the motor to transmit rotational force to the cycloid gear system 30.

For any of the embodiments as described above, the crankshafts 40, including the central crankshaft 42 and the peripheral crankshafts 44, may each comprise at least one eccentric component 42a, 44a radially and outwardly extending from the respective central axis of the crankshaft 40, with the center of the eccentric component 44 being arranged to offset from the central axis of the respective crankshaft 40, as shown in the example of Fig. 1. Particularly, the crankshafts 40 are arranged to connect the cycloidal gear plate 32 via the respective eccentric components 42a, 44a. In one embodiment, one or more of the eccentric components 42a, 44a may be configured with one or more bearings (not shown) at, on, or adjacent the exterior circumferential surface of the respective eccentric components 42a, 44a. The eccentric components 42a, 44a are arranged to be movably received by the corresponding through-holes provided in the cycloidal gear plate 32. For example, the eccentric components 42a of the central crankshaft 42 are adapted to engage the through-hole located at a central region of the cycloidal gear plate 32, while the eccentric components 44a of the one or more peripheral crankshafts 44 are adapted to engage the corresponding through-holes located at a peripheral region of the cycloidal gear plate 32. In yet another embodiment, each of the crankshafts 40 may comprise at least two eccentric components, such as the first eccentric components 42a, 44a and the second eccentric components 42b, 44b, as shown in Fig. 1. Preferably, the first and the second eccentric components are longitudinally spaced apart from one another along the length of their respective crankshafts 40, and more preferably, arranged axially offset from the central axes of their respective crankshafts to a different extent and/or at a different phase from one another, i.e. the first eccentric component 42a, 44a may be configured to extend a longer distance in one direction than the second eccentric component 42b, 44b in the same direction, for example. In one embodiment, the first eccentric components 42a, 44a are arranged to be received by the corresponding through-holes in the first cycloidal gear plate 32, while the second eccentric components 42b, 44b are arranged to be received by the corresponding through-holes in the second cycloidal gear plate 34.

The cycloidal gear system 30 may further comprise a housing 36 positioned to surround one or more of the cycloidal gear plates 32, 34. Preferably, the housing 36 comprises a gear ring with a set of internal circumferential gear teeth 38 for engaging corresponding sets of external circumferential gear teeth 33, 35 of the cycloidal gear plates 32, 34. In one specific embodiment, the gear ring 36 may form part of a housing 40 of the mechanism 12. In one further embodiment, the housing 40 and a casing 16 may define a cavity to substantially encase and accommodate the mechanism 12, including the gear system 20, the crankshafts 40 and the cycloidal gear system 30; with the casing 16 being configured to facilitate connection between the input gear 22 and the motor. Optionally, one or more bearings such as in the form of a ring bearing 17 or the like may also be provided in association with one or more movable parts of the device 10, such as between the one or more cycloidal gear plates 32, 34 in the housing 40 and/or the output 14 to thereby reduce friction and to improve power transmission efficiency.

The present invention is advantageous in that it provides a gearbox, such as in the form of a RV reducer, with an improved efficiency, higher maximum torque to size ratio, and/or an extended lifespan when compared to conventional gearboxes. It is generally known that the lifespan of a gearbox is limited by the relatively short lifespan of its moving parts, and more particularly, the bearings such as the crankshaft bearings provided at the eccentric components of the crankshafts. Durability of the bearings is highly dependent on the load applied during operation, i.e. where a high load is driven and the crankshaft bearings are constantly under load, they are more likely to wear out quickly and thus frequent replacements will be required. By increasing the number of crankshafts, such as by including an additional crankshaft at the central position of the gearbox, the load can further be spread out and be shared across a greater number of crankshafts and thus the crankshaft bearings will individually experience less load and thus less wear. The stress experienced by each of the individual bearings is therefore reduced. The increased number of crankshafts provided by the present invention is beneficial not only by improving the lifespan of the bearings and thus a higher overall efficiency of the gearbox over its lifespan, but also increasing the maximum torque that can be transmitted by the gearbox without the need for increasing the dimensions of the gearbox or its components, etc. The present invention provides a gearbox of a size which can transmit a higher torque and thus higher power than a conventional gearbox of the same size. A higher level of performance can also be maintained over the lifespan of the gearbox as the crankshafts and the crankshaft bearings are likely to wear out at a much slower rate.

For example, in one traditional gearbox design which may generally require a planetary gear system having a sun gear and a number of planet gears surrounding the sun gear, it will be understood that the sun gear and the planet gears rotate in opposite directions, i.e. if the sun gear is rotating in a clockwise direction, the planet gears will be rotating in an anti-clockwise direction. In this traditional arrangement, the sun gear cannot drive a crankshaft due to its different direction of rotation compared to the planet gears and thus the gearbox will fail to operate. Whereas in the present invention, the gear system is specifically designed and configured to include a further set of tertiary gears operably meshed with the secondary gears to transmit rotation from one central input gear to a plurality of crankshafts, including the central crankshaft. The tertiary gears rotate in a same direction as the input gear, and all of the tertiary gears rotate at the same speed and in the same direction. This further allows the plurality of crankshafts including the central crankshaft and the peripheral crankshafts to be rotated in sync with the tertiary gears, i.e. at the same speed, same direction and/or same phase. As previously discussed, the special arrangement of the present invention assists in maximizing torque that the gearbox can experience when compared to a conventional gearbox of the same size without significantly increasing the size of the gearbox, as well as improving the lifespan of the gearbox including the lifespan of the crankshafts and crankshaft bearings.

The secondary gears, such as the secondary gears 26 as shown in the embodiment of Figs. 1 and 2, can be provided in the form of compound gears each compound gear having a first larger gear 26a and a second smaller gear 26b fixed thereto. The secondary gears 26 are arranged such that the larger gear 26a meshes with the input gear 22 and that the smaller gear 26b meshes with the tertiary gears 28. Alternatively, the gear system 20 may be arranged in a single-gear plane arrangement, such that the input gear 22, the secondary gears 26 and the tertiary gears 28 are all arranged at the same, single gear plane, as shown in Fig. 3, with the central crankshaft 42 being directly driven by the input gear 22, and the peripheral crankshafts being directly driven by the tertiary gears 28, for example. Since all crankshafts 40 must be rotated at least in the same direction and at the speed for the gearbox to operate, it is preferred for the input gear 22 and each of the tertiary gears 28 to have the same number of teeth, and especially so, for the embodiment configured in the single-gear plane arrangement of the gear system 20 of Fig. 3.

As discussed earlier, the longer lifespan of the gearbox of the present invention is achieved by having an additional, centrally located crankshaft to share the load with the plurality of peripheral crankshafts. It is thus preferred for the load be evenly distributed and shared among all the crankshafts. To achieve this technical effect, it is preferred that all the gears which are directly connected with the multiple crankshafts, such as the four tertiary gears 28 including the central tertiary gear 28a and the three peripheral tertiary gears 28b, be rotated at the same direction, same speed and same phase, such as the case as shown in the embodiment of Figs. 1 and 2. For the load evenly shared among all the crankshafts, each crankshaft and its bearings carry less but the same amount of load, and therefore the maximum load that can be transmitted by the gearbox can be increased, the transmission efficiency can be improved, and the lifespan of the gearbox in general can be extended.

The present description illustrates the principles of the present invention. It will thus be appreciated that those skilled in the art will be able to devise various arrangements that, although not explicitly described or shown herein, embody the principles of the invention and are included within its spirit and scope.

Moreover, all statements herein reciting principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents as well as equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure.

While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only exemplary embodiments have been shown and described and do not limit the scope of the invention in any manner. It can be appreciated that any of the features described herein may be used with any embodiment. The illustrative embodiments are not exclusive of each other or of other embodiments not recited herein. Accordingly, the invention also provides embodiments that comprise combinations of one or more of the illustrative embodiments described above. Modifications and variations of the invention as herein set forth can be made without departing from the spirit and scope thereof, and, therefore, only such limitations should be imposed as are indicated by the appended claims.

In the claims hereof, any element expressed as a means for performing a specified function is intended to encompass any way of performing that function. The invention as defined by such claims resides in the fact that the functionalities provided by the various recited means are combined and brought together in the manner which the claims call for. It is thus regarded that any means that can provide those functionalities are equivalent to those shown herein.

In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art.

Claims

A gear transmission device, comprising:

a mechanism having a central axis aligned with a central axis of the device, the mechanism comprising a gear system configured to transmit a rotational force from a rotary power source to a plurality of crankshafts; the gear system comprising an input gear arranged to be driven by the rotary power source, and one or more gear units engaging the input gear for transmitting the rotational force from the rotary power source to the plurality of crankshafts;

wherein the plurality of crankshafts comprise a central crankshaft and one or more peripheral crankshafts; the central crankshaft being positioned in longitudinal alignment with the central axis of the mechanism, and the one or more peripheral crankshafts being positioned longitudinally parallel to the central axis of the mechanism; with the central crankshaft and the peripheral crankshafts being arranged to rotate in a same direction of rotation.
The gear transmission device according to claim 1, wherein the gear system is configured to transmit the rotational force from the rotary power source to a cycloidal gear system via the plurality of crankshafts, the cycloidal gear system comprises at least one cycloidal gear plate movably connectable with the plurality of crankshafts to allow a cycloidal movement of the at least one cycloidal gear plate in response to rotation of the plurality of crankshafts.
The gear transmission device according to claim 2, wherein the central crankshaft is positioned in longitudinal alignment with the central axis of the mechanism for connecting the cycloidal gear system at a substantially central position of the cycloidal gear plate; and the peripheral crankshafts being positioned substantially parallel to the central crankshaft and offsetting from the central axis of the mechanism for connecting the cycloidal gear system at a substantially peripheral position of the cycloidal gear plate.
The gear transmission device according to claim 1, wherein the central crankshaft and the one or more peripheral crankshafts are arranged to rotate in the same direction of rotation as the input gear.
The gear transmission device according to claim 1, wherein the central crankshaft and the one or more peripheral crankshafts are arranged to rotate in a same speed.
The gear transmission device according to claim 1, wherein the one or more gear units of the gear system comprise one or more secondary gears rotatably engaged around the input gear.
The gear transmission device according to claim 6, wherein the one or more gear units further comprise one or more tertiary gears, wherein the one or more tertiary gears are operably engageable with the one or more secondary gears.
The gear transmission device according to claim 7, wherein the one or more tertiary gears are of no direct contact or engagement with the input gear.
The gear transmission device according to claim 7, wherein the one or more tertiary gears comprise a central tertiary gear positioned substantially in axial alignment with the central axis of the mechanism, and at least one peripheral tertiary gear positioned to offset from the central axis of the mechanism.
The gear transmission device according to claim 7, wherein the one or more tertiary gears are each connected at a proximal end of a respective one of the plurality of crankshafts.
The gear transmission device according to claim 7, wherein the one or more tertiary gears are positioned to offset from the central axis of the mechanism, with the input gear and each of the tertiary gears being connected at a proximal end of a respective one of the plurality of crankshafts.
The gear transmission device according to claim 11, wherein the input gear, the secondary gears and the tertiary gears are arranged substantially on a same, transverse plane substantially perpendicular to the central axis of the mechanism.
The gear transmission device according to claim 9, wherein each of the secondary gears is operably engageable with at least two tertiary gears comprising one central tertiary gear and at least one peripheral tertiary gear.
The gear transmission device according to claim 1 or 2, wherein each of the plurality of crankshafts comprises at least one eccentric component configured to axially offset from a central axis of the respective one of the crankshafts.
The gear transmission device according to claim 14, wherein the plurality of crankshafts are arranged to connect the at least one cycloidal gear plate via the at least one eccentric component of each of the respective crankshafts.
The gear transmission device according to claim 15, wherein the at least one cycloidal gear plate comprises a plurality of through-holes each of which being arranged to receive the at least one eccentric component of each of the respective crankshafts.
The gear transmission device according to claim 2, wherein the cycloidal gear system comprises a housing positioned to surround the at least one cycloidal gear plate, the housing comprises a gear ring having a set of internal circumferential gear teeth for engaging corresponding sets of external circumferential gear teeth of the at least one cycloidal gear plate.
The gear transmission device according to claim 17, wherein the ring unit forms part of a housing of the mechanism.
The gear transmission device according to claim 14, wherein each of the plurality of crankshafts comprises at least two eccentric components longitudinally spaced apart from one another, the two eccentric components being configured to axially offset from the central axis of the respective one of the crankshafts at a different extent and/or at a different phase from one another.