Friction or traction roller-type transmission

Abstract

A friction or traction roller-type transmission comprising: a stationary ring; a sun wheel; at least four rolling components including at least one flexible planetary wheel and at least one lateral support roller, and a rotatable carrier. The flexible planetary wheel contacts the sun wheel and the stationary ring. The lateral support roller contacts at least an adjacent one of the flexible planetary wheel. The lateral support roller comprises a pin and a solid roller rotatably mounted to the pin. The roller-type transmission also includes at least three roller pins with at least one end being secured to one of the at least one supporting plate. At least one of the at least three roller pins is the lateral support roller pin. The at least four rolling components can include at least two guide rollers and the at least three roller pins can include two guide roller pins.

Description

FRICTION OR TRACTION ROLLER-TYPE TRANSMISSION CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority under 35USC§119(e) of US provisional patent applications nos. 63 / 777.420 filed on March 25, 2025 and 63 / 801.880 filed on May 8, 2025, the specifications of which are hereby incorporated by reference.TECHNICAL FIELD OF THE INVENTION

[0002] The technical field relates to friction or traction roller-type drives or transmissions.BACKGROUND

[0003] Rotary speed adapters are used to modify the torque and speed of an energy supply to the requirements of a load. For instance, speed reducers can be used to increase the torque.

[0004] A planetary friction or traction transmission includes a sun wheel, serving as the input and the driver, and three or more planetary wheels, evenly distributed, engaged with the sun wheel. The planetary wheels are driven and rotate around the sun wheel within a stationary ring. The planetary friction or traction transmission further includes a rotatable carrier, serving as a portion of an output assembly. In some implementations, the friction or traction roller-type transmission can further include lateral support rollers mounted to the rotatable carrier and engaged in rotation by the planetary wheels.

[0005] To enable a precise transmission of motion between the input and the output members of the transmission, allowing rigid and precise motion control, it is desirable to eliminate play or loose movement between contact surfaces, allowing a transmission without backlash. A preload between the planetary wheels and the lateral support rollers is thus desirable. This preload also helps in forcing a rolling motion therebetween, reducing the possibility of abrasive wear and improving service life.

[0006] In prior art, to reduce play and create a preload between the planetary wheels and the lateral support rollers, the assembly is designed with a light interference between the planetary wheels and the lateral support rollers. However, this designed light interference requires tight manufacturing tolerances to avoid excess interference which can create large loads on the planetary wheels, the lateral support rollers and the bearings, reducing service life, while insufficient interference can result in backlash and the possibility of abrasive wear. Typically, in prior art, an interference in the order of just a few microns is required to achieve an adequate preload.

[0007] There is thus a need to provide a new friction or traction roller-type transmission wherein a preload between the planetary wheels and the lateral support rollers is maintained without requiring tight manufacturing tolerances, which require precision manufacturing techniques that can be challenging and costly.

[0008] The planetary wheels are free rollers slightly compressed between the sun wheel and an inner rolling surface of the stationary ring. An orbital rolling motion of the planetary wheels is transmitted to the rotatable carrier, through the lateral support rollers.

[0009] In addition to the rotatable carrier, the output assembly includes an output shaft, which defines a rotation axis and supported by rolling element bearings. The rolling element bearings define the position and the orientation of a rotation axis of the output shaft and block the other degrees of freedom. To limit the degrees of freedom and allow solely a rotation of the shaft along its rotation axis, several bearing options are typically used such as two deep-groove ball bearings, one cross-roller bearing, one four-point contact bearing, one double row angular contact bearing, two angular contact bearings, etc. To constrain the degrees of freedom, these bearings are relatively costly and / or include several components. It is appreciated that it is desirable to minimize the number of components in a friction or traction roller-type transmission to reduce at least one of space, weight, and cost.

[0010] Furthermore, in some embodiments, greater stiffness for the definition of the position of the input and / or the output rotation axes can be desirable.

[0011] There is thus a need to provide a new friction or traction roller-type transmission including a new rolling element bearing arrangement which is at least one of cheaper, smaller in terms of volume, and lighter and / or includes less components. Furthermore, it can be desirable to provide an alternative reduction stage geometry which can provide a greater stiffness for the definition of the position of the input and / or the output rotation axes.

[0012] In view of the above, there is a need for friction or traction roller-type transmission which would be able to overcome or at least minimize some of the abovediscussed prior art concerns.SUMMARY

[0013] It is therefore an aim of the present invention to address the above-mentioned issues.

[0014] According to a general aspect, there is provided a friction or traction roller-type transmission comprising: a stationary ring having an inner rolling surface defining an annular space; a sun wheel extending in the annular space and being concentric with the stationary ring, the sun wheel having an outer contacting surface; at least three pairs including a flexible planetary wheel and a rolling element, each one of the pairs being located in the annular space between the sun wheel and the inner rolling surface of the stationary ring, each one of the flexible planetary wheel having an outer surface contacting the outer contacting surface of the sun wheel and the inner rolling surface of the stationary ring, each one of the rolling elements being located between adjacent ones of the flexible planetary wheels and having an outer contacting surface contacting the outer surface of the adjacent ones of the flexible planetary wheels, each one of the rolling elements comprising a pin with two opposed ends and a solid roller rotatably mounted to the pin; and a rotatable carrier comprising at least one supporting plate with the at least three pairs and the sun wheel being axially located on one side thereof, oneof the opposed ends of the pins of the rolling elements being secured to a respective one of the at least one supporting plate, the at least one supporting plate having a central portion, pin connecting portions located peripherally to the central portion and having one of the ends of the pins secured thereto, and at least one flexible arm, each one of the at least one flexible arm connecting a respective one of the pin connecting portions to the central portion of the respective one of the at least one supporting plate, wherein the at least one flexible arm and the respective one of the pin connecting portions are configured to move radially when subjected to a radial load.

[0015] In an embodiment, the rotatable carrier comprises two of the at least one supporting plate, with the at least three pairs and the sun wheel being axially located inbetween, and each one of the opposed ends of the pins of the rolling elements being secured to a respective one of the supporting plates.

[0016] In an embodiment, each one of the at least one supporting plate of the rotatable carrier comprises one of the at least one flexible arm for each one of the rolling elements.

[0017] In an embodiment, each one of the sun wheel, the stationary ring, the flexible planetary wheels, the rolling elements and the rotatable carrier has an axial axis, and all the axial axes extend parallel to one another. The axial axes of the sun wheel, the stationary ring and the rotatable carrier are coaxial.

[0018] In an embodiment, the flexible planetary wheels and the solid rollers of the rolling elements are engageable in rotation by friction / traction contact.

[0019] In an embodiment, the at least one flexible arm has a flexibility ranging from about 0.5 N / pm to about 100 N / pm.

[0020] In an embodiment, the outer contacting surfaces of the sun wheel, the flexible planetary wheels and the solid rollers of the rolling elements, and the inner rolling surface of the stationary ring is a smooth surface.

[0021] In an embodiment, the flexible planetary wheels and the rolling elements are substantially evenly distributed in the annular space defined by the stationary ring.

[0022] In an embodiment, each one of the flexible planetary wheels is a hollow circular cylinder.

[0023] In an embodiment, the outer contacting surfaces of the solid rollers of the rolling elements are spaced apart from the inner rolling surface of the stationary ring.

[0024] In an embodiment, each one of the supporting plates further comprises planetary wheel axial supporting portions, located peripherally of the central portion, and the at least one flexible arm is connected to the central portion via at least one of the planetary wheel axial supporting portions. Each one of the at least one flexible arm can comprise two flexible arm segments, each one of the two flexible arm segments having a first end engaged with a respective one of the pin connecting portions and a second engaged with a respective one of the adjacent ones of the planetary wheel axial supporting portions. Each one of the planetary wheel axial supporting portions can be aligned a respective one of the planetary wheels to provide axial support.

[0025] In an embodiment, each one of the flexible arms is thinner than a width of at least one of the planetary wheel axial supporting portions and the pin connecting portions.

[0026] In an embodiment, a flexible joint is provided for each one of the at least one flexible arm. The flexible joint can be located centrally of the respective one of the at least one flexible arm. The flexible joint can be located between the central portion and the respective one of the at least one flexible arm. The flexible joint can comprise an elongated empty space defined between an outer edge of the central portion and an inner edge of the respective one of the at least one flexible arm.

[0027] In an embodiment, corresponding ones of the at least one flexible arm of the two supporting plates are in register.

[0028] In an embodiment, the pins of the rolling elements are, prior to assembly, located inwardly of a respective nominal operating position when the friction or traction rollertype transmission is assembled.

[0029] According to still another general aspect, there is provided a friction or traction roller-type transmission comprising: a stationary ring having an inner rolling surface defining an annular space; a sun wheel extending in the annular space and being concentric with the stationary ring, the sun wheel having an outer contacting surface; at least four rolling components located in the annular space between the sun wheel and the inner rolling surface of the stationary ring, the at least four rolling components comprising at least one flexible planetary wheel and at least one lateral support roller, each one of the at least one flexible planetary wheel having an outer surface contacting the outer contacting surface of the sun wheel and the inner rolling surface of the stationary ring, wherein the at least one lateral support roller has an outer contacting surface contacting at least one of the at least one flexible planetary wheel, the at least one lateral support roller comprising a lateral support roller pin with two opposed ends and a solid roller rotatably mounted to the lateral support roller pin; a rotatable carrier comprising at least one supporting plate with the at least four rolling components and the sun wheel being located on one side of the at least one supporting plate, the at least one supporting plate having a central portion, pin connecting portions located peripherally to the central portion, and at least one flexible arm, each one of the at least one flexible arm connecting a respective one of the pin connecting portions to the central portion of a respective one of the at least one supporting plate, wherein the at least one flexible arm and the respective one of the pin connecting portions are configured to move radially when subjected to a radial load; and at least three roller pins having opposed ends with at least one of the opposed ends being secured to a respective one of the pin connecting portions of the at least one supporting plate, and wherein at least one of the at least three roller pins is the lateral support roller pin of the at least one lateral support roller.

[0030] In an embodiment, the rotatable carrier comprises two of the at least one supporting plate, with the at least four rolling components and the sun wheel being located inbetween, and each one of the opposed ends of the lateral support roller pin being secured to a respective one of the supporting plates.

[0031] In an embodiment, each one of the at least one supporting plate of the rotatable carrier comprises one of the at least one flexible arm for each one of the at least one lateral support roller.

[0032] In an embodiment, each one of the sun wheel, the stationary ring, the at least one flexible planetary wheel, the at least one lateral support roller and the rotatable carrier has an axial axis, and all the axial axes extend parallel to one another. The axial axes of the sun wheel, the stationary ring and the rotatable carrier can be coaxial.

[0033] In an embodiment, the at least one flexible planetary wheel and the solid roller of the at least one lateral support roller are engageable in rotation by friction / traction contact.

[0034] In an embodiment, the at least one flexible arm has a flexibility ranging from about 0.5 N / pm to about 100 N / pm.

[0035] In an embodiment, the outer contacting surfaces of the sun wheel, the at least one flexible planetary wheel and the solid roller of the at least one lateral support roller, and the inner rolling surface of the stationary ring are smooth surfaces.

[0036] In an embodiment, the at least one lateral support roller comprises at least two lateral support rollers, each one being located on a respective side of each one of the at least one flexible planetary wheel and having an outer contacting surface contacting the outer surface of a respective adjacent one of the at least one flexible planetary wheel.

[0037] In an embodiment, the at least one flexible planetary wheel and the at least one lateral support roller are provided in at least three pairs, each one of the at least three pairs including one of the at least one flexible planetary wheel and one of the at least one lateral support roller, the lateral support rollers and the flexible planetary wheelsbeing provided in an alternating configuration wherein the outer contacting surface of the lateral support rollers contact the outer surface of adjacent ones of the flexible planetary wheels. The flexible planetary wheel and the lateral support rollers can be substantially evenly distributed in the annular space defined by the stationary ring.

[0038] In an embodiment, each one of the at least one flexible planetary wheel is a hollow circular cylinder.

[0039] In an embodiment, the outer contacting surface of the solid roller of the at least one lateral support roller is spaced apart from the inner rolling surface of the stationary ring and from the outer contacting surface of the sun wheel.

[0040] In an embodiment, each one of the supporting plates further comprises at least one planetary wheel axial supporting portion, located peripherally of the central portion, and the at least one flexible arm is connected to the central portion via at least one of the at least one planetary wheel axial supporting portion. The at least one planetary wheel axial supporting portion can comprise at least two planetary wheel axial supporting portions and each one of the at least one flexible arm can comprise two flexible arm segments, each one of the two flexible arm segments having a first end engaged with a respective one of the pin connecting portions and a second engaged with a respective one of adjacent ones of the at least two planetary wheel axial supporting portions. Each one of the at least one planetary wheel axial supporting portion can be aligned with a respective one of the at least one planetary wheel to provide axial support. The at least one flexible arm can be thinner than a width of the at least one planetary wheel axial supporting portion and the pin connecting portions.

[0041] In an embodiment, a flexible joint can be provided for each one of the at least one flexible arm. The flexible joint can be located centrally of a respective one of the at least one flexible arm. The flexible joint can be located between the central portion and the respective one of the at least one flexible arm. The flexible joint can comprise an elongated empty space defined between an outer edge of the central portion and an inner edge of the respective one of the at least one flexible arm.

[0042] In an embodiment, corresponding ones of the at least one flexible arm of the two supporting plates are in register.

[0043] In an embodiment, the lateral support roller pin is, prior to assembly, located inwardly of a respective nominal operating position when the friction or traction rollertype transmission is assembled.

[0044] In an embodiment, the at least one flexible planetary wheel is slightly compressible and the solid roller of the at least one lateral support roller is incompressible in comparison to the at least one flexible planetary wheel.

[0045] According to a further general aspect, there is provided a friction or traction rollertype transmission comprising: a stationary ring having an inner rolling surface defining an annular space; a sun wheel extending in the annular space and being concentric with the stationary ring, the sun wheel having an outer contacting surface; at least four rolling components located in the annular space between the sun wheel and the inner rolling surface of the stationary ring, the at least four rolling components comprising at least one flexible planetary wheel, at least one lateral support roller, and at least two guide rollers, each one of the at least one flexible planetary wheel having an outer surface contacting the outer contacting surface of the sun wheel and the inner rolling surface of the stationary ring, wherein the at least one lateral support roller has an outer contacting surface contacting the at least one flexible planetary wheel, the at least one lateral support roller comprising a lateral support roller pin with two opposed ends and a solid roller rotatably mounted to the lateral support roller pin, each one of the at least two guide rollers having an outer contacting surface contacting the outer contacting surface of the sun wheel and the inner rolling surface of the stationary ring, the at least two guide rollers being located on a respective side of the at least one lateral support roller and being spaced-apart from the outer contacting surface of the at least one lateral support roller, each one of the at least two guide rollers comprising a guide roller pin with two opposed ends and a solid roller rotatably mounted to the guide roller pin; and a rotatable carrier comprising at least one supporting plate with the at least four rolling components and the sun wheel being located on one side of the at least onesupporting plate, wherein at least one of the opposed ends of each one of the guide roller pins and the lateral support roller pin is secured to a respective one of the at least one supporting plate.

[0046] In an embodiment, the rotatable carrier comprises two of the at least one supporting plate, with the at least four rolling components and the sun wheel being located inbetween, and each one of the opposed ends of the lateral support roller pin and the guide roller pins being secured to a respective one of the supporting plates.

[0047] In an embodiment, each one of the sun wheel, the stationary ring, the at least one flexible planetary wheel, the at least one lateral support roller, the at least two guide rollers, and the rotatable carrier has an axial axis, and all the axial axes extend parallel to one another. The axial axes of the sun wheel, the stationary ring and the rotatable carrier can be coaxial.

[0048] In an embodiment, the at least one flexible planetary wheel, the solid rollers of the at least two guide rollers, and the solid roller of the at least one lateral support roller are engageable in rotation by friction / traction contact.

[0049] In an embodiment, the outer contacting surfaces of the sun wheel, the at least one flexible planetary wheel, the solid roller of the at least one lateral support roller, the solid rollers of the at least two guide rollers, and the inner rolling surface of the stationary ring are smooth surfaces.

[0050] In an embodiment, each one of the at least one flexible planetary wheel is a hollow circular cylinder.

[0051] In an embodiment, the outer contacting surface of the solid roller of the at least one lateral support roller is spaced apart from the inner rolling surface of the stationary ring and from the outer contacting surface of the sun wheel.

[0052] In an embodiment, the at least one lateral support roller comprises at least two lateral support rollers, each one being located on a respective side of the at least one flexible planetary wheel and having an outer contacting surface contacting the outersurface of a respective adjacent one of the at least one flexible planetary wheel and wherein the at least two guide rollers are located on a side of outer ones of the at least two lateral support rollers, opposed to a side contacting the respective adjacent one of the at least one flexible planetary wheel.

[0053] In an embodiment, the at least two guide rollers are spaced-apart from the outer surface of the at least one flexible planetary wheel.

[0054] In an embodiment, the at least one flexible planetary wheel is slightly compressible and the solid rollers of the at least one lateral support roller and the at least two guide rollers are incompressible in comparison to the at least one flexible planetary wheel.

[0055] According to a further general aspect, there is provided a friction or traction rollertype transmission comprising: a stationary ring having an inner rolling surface defining an annular space; a sun wheel extending in the annular space and being concentric with the stationary ring, the sun wheel having an outer contacting surface; at least four rolling components located in the annular space between the sun wheel and the inner rolling surface of the stationary ring, the at least four rolling components comprising at least one flexible planetary wheel and at least one lateral support roller, each one of the at least one flexible planetary wheel having an outer surface contacting the outer contacting surface of the sun wheel and the inner rolling surface of the stationary ring, wherein the at least one lateral support roller has an outer contacting surface contacting the at least one flexible planetary wheel, the at least one lateral support roller comprising a lateral support roller pin with two opposed ends and a solid roller rotatably mounted to the lateral support roller pin; a rotatable carrier comprising at least one supporting plate with the at least four rolling components and the sun wheel being located on one side of the at least one supporting plate; at least three roller pins having opposed ends with at least one of the opposed ends being secured to a respective one of the at least one supporting plate, wherein at least one of the at least three roller pins is the lateral support roller pin of the at least one lateral support roller; and an output assembly comprising a ring-shaped housing mounted to the stationary ring andremaining stationary therewith, an output shaft connected to an output one of the at least one supporting plate and extending centrally through the ring-shaped housing and engaged in rotation therewith, at least one annular bearing extending between the ringshaped housing and the output shaft to guide the output shaft during rotation, wherein the at least one annular bearing consists of one of a single deep groove ball bearing and at least one thrust roller bearing contacting at least one of an outer surface of the output one of the at least one supporting plate and the ring-shaped housing.

[0056] In an embodiment, the at least one annular bearing consists of two axially spaced-apart thrust roller bearings wherein an inside one is sandwiched between an output surface of the output one of the at least one supporting plate and an inner surface of the ring-shaped housing and an outside one contacts the ring-shaped housing on an output surface thereof.

[0057] In an embodiment, the friction or traction roller-type transmission further comprises a retaining ring engaged with the output shaft and being aligned with the at least one annular bearing to substantially prevent axial translation thereof.

[0058] In an embodiment, the at least four rolling components further comprises at least two guide rollers having an outer contacting surface contacting the outer contacting surface of the sun wheel and the inner rolling surface of the stationary ring, each one the at least two guide rollers being located on a side of the at least one lateral support roller and being spaced-apart from the outer contacting surface of the at least one lateral support roller, each one of the at least two guide rollers comprising a guide roller pin with two opposed ends and a solid roller rotatably mounted to the guide roller pin, wherein at least two of the at least three roller pins being the guide roller pins of the at least two guide rollers.

[0059] In an embodiment, the rotatable carrier comprises two of the at least one supporting plate, with the at least four rolling components and the sun wheel being located between the two supporting plates, and each one of the opposed ends of the at least three roller pins being secured to a respective one of the two supporting plates.

[0060] In an embodiment, the at least one lateral support roller comprises at least two lateral support rollers located on a respective side of the at least one flexible planetary wheel and having an outer contacting surface contacting the outer surface of a respective adjacent one of the at least one flexible planetary wheel.

[0061] According to a general aspect, there is provided a friction or traction roller-type transmission comprising: a stationary ring having an inner rolling surface defining an annular space; a sun wheel extending in the annular space and being concentric with the stationary ring, the sun wheel having an outer contacting surface; at least five rolling components located in the annular space between the sun wheel and the inner rolling surface of the stationary ring, and a rotatable carrier comprising at least one supporting plate. The at least five rolling components comprise at least one flexible planetary wheel and at least two lateral support rollers. Each one of the at least one flexible planetary wheel has an outer surface contacting the outer contacting surface of the sun wheel and the inner rolling surface of the stationary ring. At least one of the at least two lateral support rollers is located on each side of each one of the at least one flexible planetary wheel and has an outer contacting surface contacting the outer surface of the respective adjacent one of the at least one flexible planetary wheel. Each one of the at least two lateral support rollers comprises a lateral support roller pin with two opposed ends and a solid roller rotatably mounted to the lateral support roller pin. The at least five rolling components and the sun wheel are located on one side of the at least one supporting plate of the rotatable carrier. One of the opposed ends of the lateral support roller pins are secured to a respective one of the at least one supporting plate. The at least one supporting plate has a central portion, pin connecting portions located peripherally to the central portion and having one of the ends of the lateral support roller pins secured thereto, and at least one flexible arm. Each one of the at least one flexible arm connects a respective one of the pin connecting portions to the central portion of the respective one of the at least one supporting plate. The at least one flexible arm and the respective one of the pin connecting portions are configured to move radially when subjected to a radial load.

[0062] According to another general aspect, there is provided a friction or traction rollertype transmission comprising: a stationary ring having an inner rolling surface defining an annular space; a sun wheel extending in the annular space and being concentric with the stationary ring, the sun wheel having an outer contacting surface; at least five rolling components located in the annular space between the sun wheel and the inner rolling surface of the stationary ring, and a rotatable carrier comprising at least one supporting plate. The at least five rolling components comprises at least one flexible planetary wheel, at least two lateral support rollers, and at least two guide rollers. Each one of the at least one flexible planetary wheel has an outer surface contacting the outer contacting surface of the sun wheel and the inner rolling surface of the stationary ring. At least one of the at least two lateral support rollers is located on each side of each one of the at least one flexible planetary wheel and has an outer contacting surface contacting the outer surface of the respective adjacent one of the at least one flexible planetary wheel. Each one of the at least two lateral support rollers comprises a lateral support roller pin with two opposed ends and a solid roller rotatably mounted to the lateral support roller pin. Each one of the at least two guide rollers has an outer contacting surface contacting the outer contacting surface of the sun wheel and the inner rolling surface of the stationary ring. The at least two guide rollers are located on a side of outer ones of the at least two lateral support rollers, opposed to a side contacting a respective one of the at least one planetary wheel, and are spaced-apart from the outer contacting surfaces of the outer ones of the at least two lateral support rollers. Each one of the at least two guide rollers comprises a guide roller pin with two opposed ends and a solid roller rotatably mounted to the guide roller pin. The at least five rolling components and the sun wheel are located on one side of the at least one supporting plate of the rotatable carrier. At least one of the opposed ends of each one of the guide roller pins and the lateral support roller pins are secured to a respective one of the at least one supporting plate.

[0063] According to a further general aspect, there is provided a friction or traction rollertype transmission comprising: a stationary ring having an inner rolling surface defining an annular space; a sun wheel extending in the annular space and being concentricwith the stationary ring, the sun wheel having an outer contacting surface; at least five rolling components located in the annular space between the sun wheel and the inner rolling surface of the stationary ring, and a rotatable carrier comprising at least one supporting plate. The at least five rolling components comprises at least one flexible planetary wheel and at least two lateral support rollers. Each one of the at least one flexible planetary wheel has an outer surface contacting the outer contacting surface of the sun wheel and the inner rolling surface of the stationary ring. At least one of the at least two lateral support rollers is located on each side of each one of the at least one flexible planetary wheel and has an outer contacting surface contacting the outer surface of the respective adjacent one of the at least one flexible planetary wheel. Each one of the at least two lateral support rollers comprises a lateral support roller pin with two opposed ends and a solid roller rotatably mounted to the lateral support roller pin. The at least five rolling components and the sun wheel being located on one side of the at least one supporting plate of the rotatable carrier. The friction or traction roller-type transmission further comprises at least three roller pins having opposed ends with at least one of the opposed ends being secured to a respective one of the at least one supporting plate, at least two of the at least three roller pins being the lateral support roller pins of the at least two lateral support rollers. The friction or traction roller-type transmission further also comprises an output assembly comprising a ring-shaped housing secured to the stationary ring, an output shaft connected to an output one of the at least one supporting plate and extending centrally through the ring-shaped housing, at least one annular bearing extending between the ring-shaped housing and the output shaft to guide the output shaft during rotation. The at least one annular bearing consists of one of a single deep groove ball bearing and at least one thrust roller bearing contacting at least one of an outer surface of the output one of the at least one supporting plate and the ring-shaped housing.

[0064] In this specification, the term “friction roller-type transmission” is intended to mean a type of transmission that utilises the static friction of two smooth surfaces (instead of meshing teeth) to transfer torque between two rotating parts. The term traction transmission is intended to include similar transmission assemblies where acompressed film of traction fluid (or lubricant) is used to separate the rolling surfaces while transmitting the tangential forces.BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Fig. 1 is a perspective view of a combination of an electromagnetic motor with a drive assembly in accordance with an embodiment of the prior art;

[0066] Fig. 2 is a sectional view of the combination of Fig. 1;

[0067] Fig. 3 is an exploded view of the combination of Fig. 1;

[0068] Fig. 4 is a front elevation view of a friction or traction roller-type transmission in accordance with an embodiment;

[0069] Fig. 5 is a front elevation view of the friction or traction roller-type transmission of Fig. 4, wherein one supporting plate of a rotatable carrier is removed;

[0070] Fig. 6 is a rear perspective view of the friction or traction roller-type transmission of Fig. 4, wherein a stationary ring is removed;

[0071] Fig. 7 is a front perspective view of the friction or traction roller-type transmission of Fig. 4, without the stationary gear and wherein one supporting plate of the rotatable carrier is sectioned;

[0072] Fig. 8 is a front elevation view of one supporting plate of the rotatable carrier of the friction or traction roller-type transmission of Fig. 4;

[0073] Fig. 9 is a rear perspective view of the friction or traction roller-type transmission in accordance with another embodiment, without the stationary ring and wherein the rotatable carrier is characterized by a different shape;

[0074] Fig. 10 is a rear perspective view of a friction or traction roller-type transmission in accordance with another embodiment, with a stationary ring being omitted;

[0075] Fig. 11 is a front perspective view of the friction or traction roller-type transmission of Fig. 10, wherein one supporting plate of the rotatable carrier is sectioned; and

[0076] Fig. 12 is a perspective view of one supporting plate of the rotatable carrier of the friction or traction roller-type transmission of Fig. 10;

[0077] Fig. 13 is a front elevation view of a friction or traction roller-type transmission in accordance with another embodiment, wherein one supporting plate of the rotatable carrier is removed and the friction or traction roller-type transmission includes two guide rollers;

[0078] Fig. 14 is a rear elevation view of the friction or traction roller-type transmission of Fig. 13;

[0079] Fig. 15 is a front elevation view of a friction or traction roller-type transmission in accordance with another embodiment, wherein one supporting plate of the rotatable carrier is removed and the friction or traction roller-type transmission includes two planetary wheels, three lateral support rollers, and two guide rollers;

[0080] Fig. 16 is a rear elevation view of the friction or traction roller-type transmission of Fig. 15;

[0081] Fig. 17 is a front elevation view of a friction or traction roller-type transmission in accordance with another embodiment, wherein one supporting plate of the rotatable carrier is removed and the friction or traction roller-type transmission includes one lateral support roller, one planetary wheel concentric with the lateral support roller, and two guide rollers;

[0082] Fig. 18 is a rear perspective view of a drive assembly in accordance with an embodiment, showing an output assembly partially sectioned and including a single deep groove ball bearing (a stationary ring of the friction or traction roller-type transmission is omitted);

[0083] Fig. 19 is a sectional view of the drive assembly of Fig. 18, including the stationary ring;

[0084] Fig. 20 is a rear perspective view of a drive assembly in accordance with another embodiment, showing an output assembly partially sectioned and including two spacedapart thrust bearings (the stationary ring of the friction or traction roller-type transmission is omitted); and

[0085] Fig. 21 is a sectional view of the drive assembly of Fig. 20, including the stationary ring.

[0086] It will be noted that throughout the appended drawings, like features are identified by like reference numerals.DETAILED DESCRIPTION

[0087] Moreover, although the embodiments of the friction or traction roller-type transmission and corresponding parts thereof consist of certain geometrical configurations as explained and illustrated herein, not all of these components and geometries are essential and thus should not be taken in their restrictive sense. It is to be understood, as also apparent to a person skilled in the art, that other suitable components and cooperation thereinbetween, as well as other suitable geometrical configurations, may be used for the friction or traction roller-type transmission, as will be briefly explained herein and as can be easily inferred herefrom by a person skilled in the art. Moreover, it will be appreciated that positional descriptions such as “above”, “below”, “forward”, “rearward” “left”, “right” and the like should, unless otherwise indicated, be taken in the context of the figures and correspond to the position and orientation of the friction or traction roller-type transmission and corresponding parts. Positional descriptions should not be considered limiting.

[0088] Hereinafter, the terms “front” and “input side” is intended to mean closer to a motor and its shaft and “rear” and output side” means closer to the output shaft.

[0089] In the following description, the same numerical references refer to similar elements. Furthermore, for the sake of simplicity and clarity, namely so as to not unduly burden the figures with several references numbers, not all figures contain references to all the components and features, and references to some components and features may be found in only one figure, and components and features of the present disclosure which are illustrated in other figures can be easily inferred therefrom. The embodiments, geometrical configurations, materials mentioned and / or dimensions shown in the figures are optional, and are given for exemplification purposes only.

[0090] To provide a more concise description, some of the quantitative expressions given herein may be qualified with the term "about". It is understood that whether the term "about" is used explicitly or not, every quantity given herein is meant to refer to an actual given value, and it is also meant to refer to the approximation to such given value that would reasonably be inferred based on the ordinary skill in the art, including approximations due to the experimental and / or measurement conditions for such given value. In the following description, the term “about” means within an acceptable error range for the particular value as determined by one of ordinary skill in the art, which will depend in part on how the value is measured or determined, i.e. the limitations of the measurement system.

[0091] Friction or traction roller-type transmissions (or drives) rely on the friction or traction forces generated between smooth elements in rolling contact. Generally, a friction transmission refers to a transmission with dry contacts while a traction transmission refers to a transmission with lubricated contacts. As opposed to toothed gears, contacts between the cylindrical rotatable elements are continuous (i.e., toothless), between substantially smooth surfaces, leading to significant opportunities to reduce noise, reduce vibrations, increase stiffness, run at higher speeds and reduce backlash at the contact points.

[0092] Referring to the drawings, FIG. 1 shows a combination of an electromagnetic motor 10 with a drive assembly 5, in accordance with a non-limitative embodiment of the prior art. When a shaft 8 (FIG. 2) of the electromagnetic motor rotates, anoutput assembly 9 of the drive assembly 5 rotates relative to a housing 11 of the drive assembly 5 and the electromagnetic motor 10 with a reduced velocity and an increased torque. In some embodiments, an optional position sensor 12 can be mounted to the housing 11 to monitor directly or indirectly the position of the output shaft 13.

[0093] FIGS. 2 and 3 are respectively sectional and exploded views of the drive assembly 5 and the electromagnetic motor 10 of FIG. 1, wherein the drive assembly 5 includes two speed reduction stages 15, 16. In addition, the drive assembly 5 includes an optional coupling 14 mounted between the motor shaft 8 and a first one of the speed reduction stages 15 to allow misalignments. In the non-limitative embodiment shown, the drive assembly 5 further includes a second speed reduction stage 16. The rotary motion of the motor shaft 8 is sequentially transmitted to the first and the second speed reduction stages 15, 16. The output assembly 9, of the drive assembly 5 includes a cross roller bearing 17, an output shaft 13, and a seal 19 to protect the drive from ingress and retain lubricants. The cross roller bearing 17 guides the output shaft 13. As mentioned above, the cross roller bearing 17 defines the position and the orientation of a rotation axis of the output shaft 13 and blocks the other degrees of freedom.

[0094] The optional position sensor 12 reads the position of a ring 18 of the drive assembly 5, circumscribing the output shaft 13. According to an embodiment, the ring 18 is encoded (e.g., on its surface) such as to have its angular position readable by the position sensor 12.

[0095] It is appreciated that, in an alternative embodiment, the drive assembly 5 can include a single speed reduction stage or more than two speed reduction stages. Each one of the speed reduction stages can be one of the embodiments of the friction or traction roller-type transmission which is described in the following paragraphs in reference to the figures and alternatives thereof.

[0096] Referring now to FIGS. 4 to 8, there is shown a first non-limitative embodiment of the friction or traction roller-type transmission 20 including a sun element (or wheel) 22 in a center thereof engageable in rotation by the shaft of a motor, such as the shaft 8 ofFIGS. 1 to 3, or the output of a previous drive stage. The sun wheel 22 has a smooth outer contacting surface 24 and is the driver of the friction or traction roller-type transmission 20.

[0097] The friction or traction roller-type transmission 20 also includes a stationary ring 26, only shown in FIGS. 4 and 5 for clarity, having an inner rolling surface 28, and a plurality of planetary wheels (or free or flex rollers) 30 located in annular space 25 defined between the sun wheel 22 and the inner rolling surface 28 of the stationary ring 26, evenly distributed in the annular space 25. The stationary ring 26 is mounted concentrically with the sun wheel 22. Each one of the planetary wheels 30 is a flexible roller with a smooth outer contacting surface 36, e.g. the planetary wheels 30 can be slightly deformed and / or compressed. In the embodiment shown, each one of the planetary wheels 30 is a hollow circular cylinder with an inner surface 34 defining an inner space 32 (or bore). Being flexible, each planetary wheel 30 is slightly deformable and a shape of the inner space 32 can slightly vary from a circular shape. It is appreciated that, in an alternative embodiment, a central portion of each one of the planetary wheels 30 can be filled with a compressible material, i.e. a material more compressible than the material defining a peripheral portion of the planetary wheel 30. In some embodiments, the central portion of each one of the planetary wheels 30 can be thinner than the peripheral portion, thereby providing compressibility and / or deformability to the planetary wheels 30.

[0098] In some embodiments (see below in reference to Figs. 13 to 16), the friction or traction roller-type transmission can also include pins extending through the inner space 32 of the planetary wheels 30, without contacting their inner surface 34 and without guiding or supporting their rotation movement.

[0099] In some embodiments (not shown), the planetary wheel can be a solid and slightly flexible wheel, i.e. slightly compressible.

[0100] The inner space 32 of the planetary wheels 30 is dimensioned so that targeted preloads are generated under a predetermined level of assembly interference.The targeted preload is a function of the targeted torque transmission capacity. For instance and without being limitative, forces can be in the range of 50 N to 20,000 N at targeted interferences in the range of 20 to 200 microns, for each planetary wheel 30.

[0101] The outer contacting surface 36 of each one of the planetary wheels 30 contacts tangentially the outer contacting surface 24 of the sun wheel 22 and the inner rolling surface 28 of the stationary ring 26. More particularly, the planetary wheels 30 are under a compressed load (i.e. slightly compressed or preloaded), generating fractional or frictional contact. Therefore, when the sun wheel 22 is engaged in rotation, the planetary wheels 30 are simultaneously engaged in rotation between the sun wheel 22 and the stationary ring 26. The flexible planetary wheels 30 are engaged in rotation by friction / traction contact with the outer contacting surface 24 of the sun wheel 22. More particularly, when the sun wheel 22 is engaged in rotation, the planetary wheels 30 define an orbital motion confined by the stationary ring 26.

[0102] The friction or traction roller-type transmission 20 further includes a plurality of lateral support rollers 40, evenly distributed in the annular space 25. Each one of the lateral support rollers 40 includes a solid roller 44, a lateral support roller pin 46 and, optionally, a rolling bearing 48. The solid rollers 44 rotate around their respective lateral support roller pin 46 with the rolling bearing 48 being located inbetween. In the non-limitative embodiment shown, the rolling bearing 48 is a needle bearing but it is appreciated that other types of bearings can be used.

[0103] In comparison to the planetary wheels 30, the lateral support rollers 40 are incompressible and undeformable. In some embodiments, they are substantially void free in that there is continuous contact between the solid roller 44 and the lateral support roller pin 46.

[0104] In some embodiments, for instance when the friction or traction roller-type transmission 20 is free of guide rollers, as will be explained in more details below, the lateral support rollers 40 are provided in pairs with the planetary wheels 30. In the non-limitative embodiment shown, the friction or traction roller-type transmission 20 includesthree pairs of planetary wheels 30 and lateral support rollers 40. However, it is appreciated that, in an alternative embodiment (not shown), the friction or traction rollertype transmission 20 can include more than three pairs of planetary wheels 30 and lateral support rollers 40. Each one of the lateral support rollers 40 contacts two planetary wheels 30, one on each side thereof.

[0105] In the embodiment shown, the solid rollers 44 have an outer contacting surface 45 which does not contact the inner rolling surface 28 of the stationary ring 26 and the outer contacting surface 24 of the sun wheel 22, i.e. the outer contacting surface 45 is spaced-apart from the inner rolling surface 28; there is a gap inbetween since they are rotating in the opposed direction of the planetary wheels 30. However, the outer contacting surfaces 45 of the solid rollers 44 contact tangentially the outer contacting surfaces 36 of the two adjacent ones of the planetary wheels 30. In other words, each lateral support rollers 40 is located between two flexible planetary wheels 30 with their respective outer contacting surfaces 36, 45 being in contact. The lateral support rollers 40 are engaged in rotation via the outer contacting surfaces 36, 45 being in contact tangentially. More particularly, the solid rollers 44 of the lateral support rollers 40 are engaged in rotation by friction / traction contact with the outer contacting surfaces 36 of the flexible planetary wheels 30.

[0106] Hereinafter, the planetary wheels 30 are qualified as being flexible in that their outer shape can be modified elastically when forces are applied thereon. The solid rollers 44 are qualified as being solid in that their elastic deformation is generally comparatively small due to lower contact forces. Therefore, upon actuation of the friction or traction roller-type transmission 20, a peripheral shape of the planetary wheels 30 undergoes more deformation than a peripheral shape of the solid rollers 44. In some embodiments, the solid rollers 44 are substantially undeformed by the contact with the flexible planetary wheels 30.

[0107] In the non-limitative embodiment shown, the outer contacting surfaces 24, 36, 45 of the sun wheel 22, planetary wheels 30, and solid rollers 44 are smoothsurfaces, i.e. a surface being free of embossing pattern, roughness, irregularities, lumps or holes.

[0108] Furthermore, the outer contacting surfaces 24, 45 of the sun wheel 22 and solid rollers 44 and the inner rolling surface 28 of the stationary ring 26 are generally cylindrical and peripherally circular in shape. In some embodiments (not shown), they can include peripheral grooves or undercuts (i.e. radial grooves or undercuts), and the like to reduce the contact surface area between the outer contacting surfaces 24, 45 and / or the inner rolling surface 28. Furthermore, the outer contacting surfaces 36 of the planetary wheels 30, without deformation, is also substantially cylindrical and circular in shape.

[0109] In addition, the friction or traction roller-type transmission 20 further includes a rotatable carrier 50 to which the output shaft 13, or a sun wheel of a subsequent drive stage, is connected and, in some embodiments, secured. Thus, engaging the rotatable carrier 50 in rotation engages the output shaft 13 in rotation.

[0110] Thus, each one of the sun wheel 22, the stationary ring 26, the flexible planetary wheels 30, the lateral support rollers 40, and the rotatable carrier 50 has axial axis, and all the axial axes extend substantially parallel to one another. The axial axes of the sun wheel 22, the stationary ring 26, and the rotatable carrier 50 are coaxial.

[0111] Each one of the sun wheel 22, the stationary ring 26, the flexible planetary wheels 30, and the lateral support rollers 40 has a rolling surface, either internal or external, that is substantially cylindrical and circular and a rotation axis. The rotation axes of the sun wheel 22, the stationary ring 26, the flexible planetary wheels 30, and the lateral support rollers 40 extend substantially parallel to one another so that all rolling contacts are line contacts extending parallel to the rotation axes.

[0112] The rotatable carrier 50 includes two axially spaced-apart supporting plates 51a, 51b, one closer on the input side of the stage and one closer to the output side, which are engaged in rotation simultaneously. In an embodiment, the two supporting plates 51a, 51b can be connected to one another. For instance, they can bemanufactured as a single unit, being integral to one another. The planetary wheels 30 and the lateral support rollers 40 are located axially between the supporting plates 51a, 51b. The lateral support roller pins 46 of the lateral support rollers 40 are supported at both ends by the rotatable carrier 50, with each end being secured to a respective one of the supporting plates 51a, 51b.

[0113] Each one of the supporting plates 51a, 51b is made of a stiff material and has a thickness sufficient to ensure high torsional rigidity. The supporting plates 51a, 51b hold in place the lateral support roller pins 46 and the solid rollers 44 mounted to the lateral support roller pins 46 and which, in turn, contact the planetary wheels 30.

[0114] Each one of the supporting plates 51a, 51b is designed to provide a radial flexibility to a location of the lateral support roller pins 46, i.e. to allow some radial motion to the lateral support roller pins 46 and the solid rollers 44 supported by the lateral support roller pins 46 when they are subjected to a radial load.

[0115] In the embodiment shown, the friction or traction roller-type transmission 20 includes two axially spaced-apart supporting plates 51a, 51b, respectively located on an input side and an output side of the friction or traction roller-type transmission (i.e. the input supporting plate 51a and the output supporting plate 51b). However, it is appreciated that, in an alternative embodiment, the friction or traction roller-type transmission can include a single supporting plate, located either on the input side or the output side of the friction or traction roller-type transmission.

[0116] More particularly, the supporting plates 51a, 51b include flexible arms 56, as shown in FIG. 7, which are oriented substantially perpendicular to an axis of the lateral support roller pins 46 to allow flexibility radially. In a particular embodiment, the flexible arms 56 are oriented substantially perpendicular to the plane containing the sun wheel axis and lateral support roller pin axes to allow flexibility radially. It is appreciated that the level of radial flexibility can be adjusted by varying at least one of a length, a width, and a thickness of the flexible arms 56.

[0117] As shown in FIG. 8, in the embodiment shown in FIGS. 4 to 8, each one of the supporting plates 51a, 51b includes three flexible arms 56, one for each lateral support roller pin 46. As the two supporting plates 51a, 51b are substantially similar, only one will be described in the following paragraphs.

[0118] In an embodiment, each one of the flexible arms has a flexibility ranging from about 0.5 N / pm to about 100 N / pm.

[0119] The supporting plate 51a, 51b includes a central portion 52, a planetary wheel axial supporting portion 54 for each one of the planetary wheels 30, located peripherally (externally) of the central portion 52, a pin connecting portion 58 for each one of the lateral support rollers 40, and one flexible arm 56 connecting a respective one of the pin connecting portion 58 to the central portion 52 via an adjacent one of the planetary wheel axial supporting portion 54. The pin connecting portion 58 are located peripherally (or externally) with respect to the central portion 52, i.e. further away from a center of the supporting plate 51 a, 51 b.

[0120] As shown in FIG. 6, on the output side, the central portion 52 of the output supporting plate 51b is engaged with an output 62 of the friction or traction roller-type transmission 20. The output 62 of the friction or traction roller-type transmission 20 is concentric with the sun wheel 22 and secured to the output supporting plate 51b and therefore, rotates simultaneously therewith.

[0121] Each one of the planetary wheel axial supporting portion 54 is aligned with a respective one of the planetary wheels 30. In the non-limitative embodiment shown, the planetary wheel axial supporting portion 54 covers a majority of a surface area of the respective planetary wheel 30.

[0122] Each one of the pin connecting portions 58 is also aligned with and superposed to a respective one of the lateral support rollers 40. In the embodiment shown, each pin connecting portions 58 includes a bore 59 extending therethrough to engage and secure a respective one of the ends of the lateral support roller pins 46. It is appreciated that the pin connecting portions 58 can be free of bore extendingtherethrough and a respective end of the lateral support roller pins 46 can still be secured thereto.

[0123] The flexible arms 56, or flexible beams, extend between and connect a planetary axial wheel supporting portions 54 and pin connecting portions 58. Referring to FIG. 8, in the embodiment shown, a width of the flexible arms 56 is thinner than a width of the planetary wheel axial supporting portions 54 and a width of the pin connecting portions 58.

[0124] A flexible joint 60 is located between the central portion 52 and the flexible arms 56 and allows the flexible arms 56 to bend and move radially, either internally or externally, with respect to the central portion 52 and the stationary ring 26 when radial forces are applied. As the supporting plates 51a, 51b are made of a rigid material, the flexible arms 56 are biased towards their original (unstressed) position.

[0125] In the non-limitative embodiment shown, the flexible joints 60 are formed by elongated empty spaces defined between an outer edge of the central portion 52 and an inner edge of the flexible arms 56. However, it is appreciated that, in an alternative embodiment (not shown), the flexible joints 60 can be a section of the supporting plates 51a, 51b less rigid than the flexible arms 56. For instance, they can be a thinner section of the supporting plates 51a, 51b or they can be made of a material having greater flexibility than the material of the flexible arms 56.

[0126] In an embodiment, a flexible joint 60 is provided for each one of the flexible arms 56. The flexible joints 60 are located centrally of the respective one of the flexible arms 56, between the central portion 52 and the respective one of the flexible arms 56.

[0127] In the embodiment shown, on the input side, the supporting plate 51a further includes a central aperture 61, concentric with the sun wheel 22. On the output side, the output supporting plate 51b can include a central aperture or can be free thereof.

[0128] As mentioned above, the two supporting plates 51a, 51b are substantially similar, therefore, corresponding ones of the flexible arms 56 and the flexible joints 60 on the two supporting plates 51a, 51b are substantially in register.

[0129] At manufacturing, the pins bore 59 defined in the supporting plates 51a, 51b are placed slightly inwards with respect with the nominal operating position of the lateral support rollers 40. When the friction or traction roller-type transmission 20 is assembled, the planetary wheels 30 are slightly compressed between the sun wheel 22 and the stationary ring 26, ovalize elastically, and contact the lateral support rollers 40, pushing the lateral support rollers 40 including their lateral support roller pins 46 outwards, towards their nominal operating position, thus generating the desired preload between the lateral support rollers 40 and the planetary wheels 30 and eliminating backlash.

[0130] The targeted bending of the flexible arms 56 can be in the order of some tens of microns (e.g. between about 10 microns and about 40 microns), significantly relaxing the requirement for tight tolerance for location of the lateral support roller pins 46 at manufacturing and diameter of the lateral support rollers 40 and the planetary wheels 30. By an improved control of the preload, being kept at a relatively low value, longer service life of the rolling bearings 48 can be expected.

[0131] Referring to FIG. 9, there is shown an alternative embodiment of the rotatable carrier 50 of the friction or traction roller-type transmission 20. In the embodiment of FIG. 9, the radial flexibility of the rotatable carrier 50 is limited to one lateral support roller pin 46 since each one of the supporting plates 51a, 51b includes a single flexible arm 56 and flexible joint 60. More particularly, the radial flexibility provided by the flexible arm(s) 56 and optionally flexible joint(s) 60 can be provided for each lateral support roller pin 46 or for a reduced number thereof. Therefore, for a friction or traction roller-type transmission 20 including three pairs of lateral support rollers 40 and planetary wheels 30, such as the ones shown in embodiments of FIGS. 4 to 8 and FIG. 9, a flexible arm 56 and an optionally flexible joint 60 can be provided for a single lateral support roller pin 46 (embodiment of FIG. 9), for the three lateral supportroller pins 46 (embodiment of FIGS. 4 to 8), or for only two lateral support roller pins (embodiment not shown).

[0132] In an embodiment, the flexible arm(s) 56 and optionally flexible joint(s) 60 can be provided for the rotatable carrier 50 in a number equal to at least the number of pairs of lateral support rollers 40 and planetary wheels 30, i.e. a roller pair, minus 2 (e.g. at least one flexible arm 56 for three roller pairs, two flexible arms 56 for four roller pairs, etc.). In some embodiments, wherein the lateral support rollers 40 and planetary wheels 30 are not provided in pairs, one or more of the lateral support rollers 40 can be associated to a flexible arm 56 and optionally flexible joint 60. When the components of the friction or traction roller-type transmission 20 are assembled, the radial forces generated and controlled by the flexible arm(s) 56 are distributed among the other lateral support rollers 40, achieving static equilibrium.

[0133] In the embodiments of FIGS. 4 to 8 and FIG. 9, the flexible arm 56 is connected / linked at a single end and, more particularly, to an adjacent one of the planetary wheel axial supporting portions 54.

[0134] Turning now to the embodiment of FIGS. 10 to 12, there is an embodiment of each one of the flexible arms 56 is connected to the adjacent ones of the planetary wheel axial supporting portions 54 at both ends thereof. In the embodiment of FIGS. 10 to 12, the features of the rotatable carrier 50 are numbered with reference numerals in the 100 series which correspond to the reference numerals of the previous embodiments.

[0135] In the embodiment of FIGS. 10 to 12, the flexible arm 156 associated to one of the lateral support roller pin 46 includes two segments 156a, 156b, one on each side of the lateral support roller pin 46 and connecting the pin connecting portion 158 to respective adjacent ones of the planetary wheel support portions 154.

[0136] In the embodiment of FIGS. 10 to 12, each one of the supporting plates 151a, 151b of the rotatable carrier 150 further includes a plurality of apertures 164 extending therethrough and opened on the two opposed faces of the supporting plates151a, 151b. The flexible joint 160 is open in both pin bores 159, e.g. one end of the flexible joint 160 merges with a respective one of the pin bores 159. It is appreciated that the supporting plates 151a, 151b can be free of apertures 164 and that the shape of the flexible arm segments 156a, 156b and the flexible joint 160 can vary from the non-limitative embodiment shown.

[0137] It is appreciated that the flexible arms create a radial flexibility thereby allowing displacement of the position of the lateral support roller pins 46 with respect to the sun wheel 22. Radial forces are also created and controlled by this displacement.

[0138] In the embodiment of FIGS. 10 to 12, the elongated slits defined in the supporting plates 151a, 151b and forming the flexible joint 160 defines the flexible arm segments 156a, 156b, which are oriented substantially perpendicularly to a longitudinal axis of the lateral support roller pins 46 (or the pin axis). In a particular embodiment, the flexible arm segments 156a, 156b are oriented substantially perpendicularly to a plane containing the sun wheel axis and the lateral support roller pin 46 axis.

[0139] The lateral support roller pins 46 are supported at both ends by a respective one of the supporting plates 151a, 151b of the rotatable carrier 150. The flexible joint 160 extending through the supporting plates 151a, 151b and defining the flexible arm segments 156a, 156b induce some radial flexibility on the location of one of the lateral support roller pins 46. As mentioned above, at manufacturing, the lateral support roller pins 46 are positioned slightly inward, in a manner such that the flexible arm segments 156a, 156b are elastically bent at assembly, generating the desired preload between all the lateral support rollers 40 and the planetary wheels 30.

[0140] In the embodiment of FIGS. 10 to 12, the supporting plates 151a, 151b include only one set of flexible arm segments 156a, 156b but it is appreciated that flexible arm segments can be provided for each one of the lateral support rollers 40 or for more than one lateral support rollers 40 and its corresponding lateral support roller pin 46.

[0141] As mentioned above for the above-described embodiment (FIGS. 4 to 9), the flexible arm segments 156a, 156b and optionally flexible joint(s) 160 can be provided for the rotatable carrier 150 in a number equal to at least the number of pairs of lateral support rollers 40 and planetary wheels 30, i.e. a roller pair, minus 2 (e.g. at least one pair of flexible arm segments 156a, 156b for three roller pairs, two pairs of flexible arm segments 156a, 156b for four roller pairs, etc.). When the components of the friction or traction roller-type transmission 20 are assembled, the radial forces generated and controlled by the flexible arm segments 156a, 156b are distributed among the other lateral support rollers 40, achieving static equilibrium.

[0142] In the embodiments described above in reference to Figs 4 to 12, the friction or traction roller-type transmission 20, 120 includes pairs of lateral support rollers 40, 140 and planetary wheels 30, 130. The pairs of flexible planetary wheel 30, 130 and the lateral support rollers 40, 140 are substantially evenly distributed in the annular space defined by the stationary ring in a manner such that each one of the flexible planetary wheels 30, 130 contacts adjacent ones of the lateral support rollers 40, 140 to form a closed circle. The flexible planetary wheel 30, 130 and the lateral support rollers 40, 140 are configured in an alternating configuration.

[0143] Turning now to Figs. 13 and 14, there is shown an alternative embodiment of a friction or traction roller-type transmission 20. The features are numbered with reference numerals in the 200 series which correspond to the reference numerals of the previous embodiments. In addition to the stationary ring 226, the sun wheel 222, the flexible planetary wheel 230, the lateral support rollers 240, the friction or traction rollertype transmission 220 includes two guide rollers 238. The guide rollers 238 enhance the stiffness of the definition of the position of the input and / or the output axes, i.e. the rotation axes of the sun wheel 222 and the output carrier and shaft (not shown).

[0144] When the friction or traction roller-type transmission 220 includes guide rollers 238, the lateral support rollers 240 and planetary wheels 230 are not provided in pairs as for the embodiments shown in Figs. 4 to 12. For instance, the friction or traction roller-type transmission includes at least four (4) rolling components which can be acombination of flexible planetary wheel(s) 230, lateral support roller(s) 240, and guide rollers 238. If present, two guide rollers are generally used.

[0145] In some embodiments, the friction or traction roller-type transmission includes at least five (5) rolling components which can be a combination of flexible planetary wheel(s) 230, lateral support rollers 240, and guide rollers 238.

[0146] In the embodiment shown in Figs. 13 and 14, the friction or traction rollertype transmission 220 includes one planetary wheel 230, two lateral support rollers 240, located on a respective side of the planetary wheel 230 and contacting same, and two guide rollers 238, each one being located on a respective side of a respective one of the lateral support rollers 240, but generally spaced-apart thereof, i.e. the outer contacting surface 245 of the lateral support rollers 240 do not generally contact the outer contacting surface of their respective guide rollers 238.

[0147] As mentioned above, the friction or traction roller-type transmission 220 includes one guide roller 238 and one lateral support roller 240 located on each side of the planetary wheel 230, i.e. on a respective side of an imaginary axis A extending through a center of the planetary wheel 230 and a center of the sun wheel 222. The two portions of the friction or traction roller-type transmission 220, located on a respective side of the axis A, are symmetrical. As will be described in more detail below in reference to the embodiment of Figs. 15 and 16, the imaginary axis A extends through a center of a middle one of the one of the planetary wheels 230 and the lateral support rollers 240 which is provided in an odd number, when the planetary wheels 230 and the lateral support rollers 240 are not provided in pairs, as in the embodiments of FIGS. 4 to 12. In the embodiment of Figs. 13 and 14, there is a single planetary wheel 230 and two lateral support rollers 240, therefore, the imaginary axis A extends through the center of the planetary wheel 230.

[0148] As for the planetary wheels 230, the outer contacting surface of the guide rollers 238 contacts the outer contacting surface 224 of the sun wheel 222. Therefore,the guide rollers 238 are engaged in rotation by and simultaneously with the sun wheel 222.

[0149] In turn, while the outer contacting surfaces 245 of the lateral support rollers 240 are spaced-apart from the stationary ring 226, i.e. do not contact the inner rolling surface 228 of the stationary ring 226 since they are rotating in a rotation direction opposed to a rotation direction of the planetary wheels 230, the outer contacting surface of the guide rollers 238 contacts the inner rolling surface 228 and roll thereon.

[0150] Furthermore, the two guide rollers 238 are spaced-apart from one another, i.e. their outer contacting surfaces are not in contact. Furthermore, the guide rollers 238 are spaced-apart from the planetary wheel, with one lateral support roller 240 inbetween. The guide rollers 238 are also spaced-apart from the lateral support rollers 240.

[0151] As the lateral support rollers 240, each one of the guide rollers 238 includes a solid roller 239, a guide roller pin 241 and, optionally, a rolling bearing 242. The solid rollers 239 rotate around their respective guide roller pin 241 with the rolling bearing 242 being located inbetween. In the non-limitative embodiment shown, the rolling bearings 242 are needle bearings but it is appreciated that other types of bearings can be used. As the lateral support roller pins 246, the guide roller pins 241 are supported at both ends by the rotatable carrier 250 and, more particularly, by a respective one of the supporting plates 251a, 251b (only one is shown in Fig. 14) of the rotatable carrier 250 in the non-limitative embodiment shown. Therefore, the rotatable carrier 250 is engaged in rotation by both the lateral support rollers 240 and the guide rollers 238. In an embodiment (not shown), wherein the rotatable carrier 250 includes a single supporting plate 251, only one end of the guide roller pins 241 can be secured to the supporting plate 251 , in one of the pin connecting portions located peripherally to the central portion.

[0152] Via the lateral support roller pins 246 and guide roller pins 241, the lateral support rollers 240 and the guide rollers 238 define the position of the rotatable carrier 250. Therefore, the radial position of the output shaft secured directly or indirectly to the rotatable carrier 250 can be further rigidly defined, in comparison with the embodiments of Figs. 4 to 12, which do not include guide rollers.

[0153] As the guide rollers 238 contact and are engaged in rotation by the sun wheel 222, the radial position of the sun wheel 222 can also be further rigidly defined.

[0154] For all embodiments, the solid roller of the lateral support roller(s) is spaced-apart from or contact free with the inner rolling surface of the stationary wheel and the outer contacting surface of the sun wheel, while the outer surface of the flexible planetary wheel(s) contacts both the inner rolling surface of the stationary wheel and the outer contacting surface of the sun wheel. Similarly, the solid roller of the guide roller(s), if any, contacts both the inner rolling surface of the stationary wheel and the outer contacting surface of the sun wheel. However, it is contact free with (or spaced-apart from) the outer surface of the flexible planetary wheel(s) and the solid roller of the lateral support roller(s).

[0155] The flexible planetary wheel(s) is slightly compressible while the solid rollers of the lateral support roller(s) and the guide roller(s) are incompressible in comparison to the at least one flexible planetary wheel.

[0156] In the embodiment of Figs. 13 and 14, pairs of alternating and contacting lateral support rollers and planetary wheels do not extend continuously around the sun wheel 222, as in the embodiments of Figs. 4 to 12. In fact, the embodiment of the friction or traction roller-type transmission 320 of Figs. 13 and 14 includes only one planetary wheel 230 contacting the sun wheel 222. However, the lateral support rollers 240, mounted to and rotatable about their lateral support roller pins 246, are positioned on each side of the planetary wheel 230 and therefore are used to maintain the planetary wheel in place and are used to substantially eliminate backlash through a light preload, as explained above.

[0157] Turning now to the embodiment of Figs. 15 and 16, there is shown an alternative embodiment of the friction or traction roller-type transmission 320 including guide rollers 338. The features are numbered with reference numerals in the 300 series which correspond to the reference numerals of the previous embodiments. While the embodiment of the friction or traction roller-type transmission 320, shown in Figs. 13 and 14, includes one planetary wheel 330, two lateral support rollers 340, located on a respective side of the planetary wheel 330 and contacting same, and two guide rollers 338, the embodiment the friction or traction roller-type transmission 320, shown in Figs.14 and 16, includes two planetary wheels 330, three lateral support rollers 340, located between and on a respective side of each one of the planetary wheels 330 and contacting same, and two guide rollers 338, each one being located on a respective side of a respective one of the two outside lateral support rollers 340, but spaced-apart thereof. As for the embodiment of Figs. 13 and 14, the outer contacting surface 345 of the two outside lateral support rollers 340 do not contact the outer contacting surface of their respective guide rollers 338 since they are rotating in opposite rotation directions. In fact, the guide rollers 338 are spaced-apart from both the lateral support rollers 340 and the planetary wheels 330. The other features being similar to the embodiment of Figs. 13 and 14, they will not be described in further details.

[0158] It is appreciated that, when the friction or traction roller-type transmission 220, 320 or any alternative thereof, includes guide rollers 238, 338, the number of guide rollers 238, 338 is at least two to rigidify the radial position of the rotation axes of at least one of the sun wheel 222, 322 and the output shaft.

[0159] As mentioned above, an imaginary axis A can extend through a center of a middle one of the one of the planetary wheels 330 and the lateral support rollers 340 which is provided in an odd number, i.e. when the planetary wheels 330 and the lateral support rollers 340 are not provided in pairs, as in the embodiments of FIGS. 4 to 12. In the embodiment of Figs. 15 and 16, there are two planetary wheels 330 and three lateral support rollers 340, therefore, the imaginary axis A extends through the center ofa middle one of the lateral support rollers 240. The two portions of the friction or traction roller-type transmission 320, located on a respective side of the axis A, are symmetrical.

[0160] Referring now to Fig. 17, there is shown an alternative embodiment of the friction or traction roller-type transmission 320, 420 including guide rollers 338, 438. The features are numbered with reference numerals in the 600 series which correspond to the reference numerals of the previous embodiments. While the embodiment of the friction or traction roller-type transmission 320, 420, shown in Figs. 13 to 16, includes at least two lateral support rollers 340, 440, the embodiment of Fig. 17 includes only one lateral support roller 640 and the single planetary wheel 630, which is located over the lateral support roller 640, i.e. the planetary wheel 630 extends peripherally to the lateral support roller 640. The planetary wheel 630 is slightly spaced-apart from the lateral support roller 640. More particularly, the inner surface 634 of the planetary wheel 630 is slightly spaced-apart from the outer contacting surface of the lateral support roller 640 from a few tens of micrometers to a few hundreds of micrometers. Therefore, the planetary wheel 630 can be slightly deformed during operation of the friction or traction roller-type transmission 620. During operation, the outer contacting surface of the lateral support roller 640 can come into rolling contact with the inner surface 634 of the planetary wheel 630, keeping the planetary wheel 630 approximatively at the desired angular location. The outer contacting surface 636 of the flexible planetary wheel 630 contacts both the inner rolling surface 628 of the stationary ring 626 and the outer contacting surface 624 of the sun wheel 622. The outer contacting surface of the lateral support roller 640 does not contact the inner rolling surface 628 of the stationary ring 626 and the outer contacting surface 624 of the sun wheel 622 and the solid roller 644 of the lateral support roller 640 is engaged in rotation by the inner surface 634 of the planetary wheel 630, i.e. by friction / traction contact.

[0161] The supporting plates of the rotatable carrier 650 can include a flexible arm (not shown) for mounting the lateral support roller 640 to control a contact force on the flexible planetary wheel 630. A controlled contact force ensures that the lateral support roller 640 and the flexible planetary wheel 630 rotate together to minimizeabrasive wear between the internal surface of the flexible planetary wheel 630 and the external surface of the lateral support roller 640.

[0162] In addition to the lateral support roller 640 and the planetary wheel 630, the friction or traction roller-type transmission 620 includes two guide rollers 638, one on each side of the nested lateral support roller 640 and the planetary wheel 630. As the above described guide rollers 238, 338, each one of the guide roller 638 has an outer contacting surface contacting the inner rolling surface 628 of the stationary ring 626 and the outer contacting surface 624 of the sun wheel 622. Each one of the guide roller 638 is spaced apart from the outer contacting surface 636 of the flexible planetary wheel 630.

[0163] The imaginary axis A extends through the center of the lateral support roller 640. The two portions of the friction or traction roller-type transmission 620, located on a respective side of the axis A, are symmetrical.

[0164] Each one of the planetary wheel 630, the lateral support roller 640, and the guide rollers 638 is similar to the ones described above in reference to Figs. 4 to 16 and will not be described in further detail. Each one of the lateral support roller 640 and the two guide rollers 638 includes a roller pin having opposed ends secured to a respective one of the supporting plates of the rotatable carrier 650. Thus, the friction or traction roller-type transmission 620 includes three roller pins (i.e. two guide roller pins 641 and one lateral support roller pin 646), which are equidistantly spaced apart in the embodiment shown, secured to the rotatable carrier 650. The roller pins are also equidistant from a center of the sun wheel 622. Therefore, the friction or traction rollertype transmission 620 is self-centering. It is appreciated that, as in the above-described embodiments, only one of the two opposed ends of the roller pins can be secured to the rotatable carrier 650.

[0165] The friction or traction roller-type transmission stages 20, 120, 220, 320, 620 are self-centering, i.e. the preload contact forces between the rolling elements are configured to align the rotation axes of the sun wheel 22, 122, 222, 322, 622 and therotatable carrier 50 150, 250, 350, 650 with the central axis of the stationary ring 26, 126, 226, 326, 626. The contacts between the rolling elements are not infinitely rigid, thereby allowing for some level of swiveling of the rotation axes of the sun wheel 22, 122, 222, 322, 622 and the rotatable carrier 50 150, 250, 350, 650 and consequently of the rotation axes of the output shaft, which is engaged in rotation by the rotatable carrier 50 150, 250, 350, 650. The contacts between the rolling elements generally force the rotation axes of the sun wheel 22, 122, 222, 322, 622 and the rotatable carrier 50 150, 250, 350, 650 to intersect with the stationary ring axis at an axial position close to a middle of the roller length, i.e. a thickness of the lateral support roller(s) 40, 140, 240, 340, 640 and the guide rollers 238, 338, 638, if any. The at least three roller pins secured to the rotatable carrier 50 150, 250, 350, 650 maintain the alignment between the input rotation axis and the output rotation axis at their junction and define the position of the rotatable carrier 50, 150, 250, 350, 650. Thus, to be self-centered, the friction or traction roller-type transmissions 20, 120, 220, 320, 620 include at least three roller pins having opposed ends with at least one of the opposed ends being secured to a respective one of the at least one supporting plate 51, 151, 251, 351, 651 or to the rotatable carrier 50 150, 250, 350, 650. In the embodiments shown, the two opposed ends of each one of the roller pins are secured to a respective one of the two supporting plates 51, 151, 251, 351, 651 of the rotatable carrier 50, 150, 250, 350, 650. Furthermore, at least one of the at least three roller pins is a lateral support roller pin 46, 146, 246, 346, 646. The other ones can be additional lateral support roller pin and / or guide roller pin(s) 41 , 141 , 241 , 341 , 641 , if any.

[0166] For instance, in the embodiments of Figs. 4 to 12, the at least three roller pins are three lateral support roller pins 46, 146.

[0167] In the embodiment of Figs. 13 and 14, the at least three roller pins are the two lateral support roller pins 246 and the two guide roller pins 241.

[0168] In the embodiment of Figs. 15 and 16, the at least three roller pins are the three lateral support roller pins 346 and the two guide roller pins 241.

[0169] In the embodiment of Fig. 17, the at least three roller pins are the single lateral support roller pin 646 and the two guide roller pins 641.

[0170] Thus, all embodiments of the friction or traction roller-type transmissions 20, 120, 220, 320, 620 include at least four rolling components and, four of them include at least five rolling components. The embodiments of Figs. 4 to 12 include six rolling components (three planetary wheels 30, 130 and three lateral support rollers 40, 140). The embodiment of Figs. 13 and 14 includes five rolling components (one planetary wheel 230, two lateral support rollers 240, and two guide rollers 238). The embodiment of Figs. 15 and 16 includes seven rolling components (two planetary wheels 330, three lateral support rollers 340, and two guide rollers 238). Finally, the embodiment of Fig. 17 includes four rolling components (one planetary wheel 630, one lateral support roller 640, and two guide rollers 638).

[0171] In the embodiments of Figures 4 to 16, the lateral support rollers 240, 340 contact at least one of the planetary wheels 230, 330, outwardly thereof, and each one of the planetary wheels 230, 330 is located between, contacted by, and guided by two lateral support rollers 240, 340, one on each side thereof.

[0172] In the non-limitative embodiment of Fig. 17, the lateral support roller 640 does not contact the outer contacting surface 636 of the flexible planetary wheel 630 but the inner surface 634 thereof.

[0173] In the non-limitative embodiments of Figs. 13 to 16, the friction or traction roller-type transmissions 220, 320 includes planetary wheel pins 280, 380 extending through the inner space 232, 332 of the planetary wheels 230, 330, without contacting their inner surface 234, 334 and without guiding or supporting their rotation movement. Each one of the planetary wheel pins 280, 380 has opposed ends with at least one of the opposed ends being secured to a respective one of the at least one supporting plate 251, 351 or to the rotatable carrier 250, 350. In the embodiments shown, the two opposed ends of each one of the planetary wheel pins 280, 380 are secured to a respective one of the two supporting plates 251, 351 of the rotatable carrier 250, 350. Itis appreciated that the friction or traction roller-type transmissions can be free of planetary wheel pins 280, 380, as for the embodiments of Figs. 4 to 12.

[0174] It is appreciated that the supporting plates 51a, 51, 151a, 151b including at least one flexible arm 56, 156, as described above in reference to Figs. 4 to 12, can be used in combination with the friction or traction roller-type transmission 220, 320, including guide rollers 238, 338, or any alternative thereof, to improve the control the contact forces with the flexible rollers (or the planetary wheels) 230, 330 while allowing for larger manufacturing tolerances.

[0175] Turning now to Figs. 18 and 19, a non-limitative embodiment of an output assembly 9 of a drive assembly 5 is shown. The features are numbered with reference numerals in the 400 series which correspond to the reference numerals of the previous embodiments. The output assembly 409 includes a ring-shaped housing 470 secured to the stationary ring 426 (shown in Fig. 19 only), on the output side thereof. In the non-limitative embodiment show, the ring-shaped housing 470 is secured to the stationary ring 426 via mechanical fasteners 472 (Fig. 19) extending therethrough, e.g bolts, but it is appreciated that the ring-shaped housing 470 can be secured via other means. For instance, the ring-shaped housing 470 can be welded to the stationary ring 426 or be single piece with stationary ring 426, i.e. cast or machined as a single piece. It is understood that an outer surface of the ring-shaped housing 470 can have another shape than a circular profile and include a circular inner surface, i.e. the inner surface of the ring-shaped housing 470 includes a cylindrical section.

[0176] The output assembly 409 also includes the output shaft 413, which extends centrally therein. The ring-shaped housing 470 extends peripherally from the output shaft 413 and is spaced-apart thereof. The ring-shaped housing 470 and the output shaft 413 overlap axially, i.e. along a rotation axis R of the output shaft 413, at least along a section thereof.

[0177] The output assembly 409 also includes a rolling element bearing 417, extending between the ring-shaped housing 470 and the output shaft 413 along at leasta section of their overlapping section. The rolling element bearing 417 contacts both the ring-shaped housing 470 and the output shaft 413 and guides the output shaft 413 during rotation.

[0178] In the non-limitative embodiment of Figs. 18 and 19, the rolling bearing 417 is a single deep groove ball bearing. In comparison with the cross-roller bearing of the prior art, the single deep groove ball bearing 417 does not limit all the degrees of freedom of the output shaft 413. In fact, the single deep groove ball bearing 417 does not constrain the output shaft 413 rigidly regarding the tilting angles, i.e. the pitch and yaw. Therefore, the single deep groove ball bearing 417 does not sufficiently rigidify the output shaft 413 and thereby small tilting angles are possible. The single deep groove ball bearing 417 is however cheaper.

[0179] Being self-centered, the friction or traction roller-type transmission 420, which can be similar to the ones of Figs. 4 to 17 or any alternative thereof, defines a transmission output point along the rotation axis R of the output shaft 413. The output stage can be conceptually treated as a ball joint. In addition, the single deep-groove ball bearing 417, axially spaced-apart from the output stage of the friction or traction rollertype transmission 420, defines a bearing point along the rotation axis R of the shaft 413, spaced-apart axially from the transmission output point. The single deep-groove ball bearing 417 can also be conceptually treated as a ball joint. The transmission output point and the bearing point being axially spaced-apart from one another, together they completely define the position and the orientation of the rotation axis of output shaft 413, i.e. they substantially prevent tilting thereof.

[0180] Finally, the output assembly 409 also includes two optional retaining rings 474a, 474b to prevent translation of the output shaft 413 and the single deep-groove ball bearing 417 along a direction corresponding to its rotation axis R. In the embodiment shown, the retaining rings 474a, 474b are engaged with either the ringshaped housing 470 or the output shaft 413.

[0181] Turning now to Figs. 20 and 21, an alternative and non-limitative embodiment of the output assembly 409 is shown. The features are numbered with reference numerals in the 500 series which correspond to the reference numerals of the previous embodiments. The output assembly 509 is similar to the one described above in reference to Figs. 18 and 19, except that the shape of the ring-shaped housing 570 differs and the single deep groove ball bearing 417 is replaced by two spaced-apart thrust roller bearings 517a, 517b, each one being located on a respective side of the ring-shaped housing 570.

[0182] An inside thrust roller bearings 517a is sandwiched between an output surface of the output supporting plate 551b and an inner surface of the ring-shaped housing 570 and an outside thrust roller bearing 517b contacts the ring-shaped housing 570 on an output surface thereof.

[0183] The ring shaped part 574 covers the outer thrust roller bearing 517b and is secured to the output shaft 513. In the non-limitative embodiment show, the ring shaped part 574 is secured to the output shaft 513 via mechanical fasteners 576 extending therethrough, e.g bolts, but it is appreciated that the ring shaped part 574 can be secured via other means. Therefore, the ring shaped part 574 rotates simultaneously with the output shaft 513. The thrust roller bearings 517a, 517b define a plane to which the rotation axis of the output shaft 513 extend perpendicularly, again intersecting the rotation axis point defined by the transmission stage, thus defining the orientation and position of the output rotation axis. As the single deep groove ball bearing 417, the thrust roller bearings 517a, 517b are cheaper than the cross-roller bearing of the prior art.

[0184] It is appreciated that, in an alternative embodiment, the output assembly could include a single thrust roller bearing 517. In such embodiment, the thrust roller bearing can contact at least one of an outer surface of the output supporting plate 551b and the ring-shaped housing 570.

[0185] Tilting movements of the output shaft 513 are thus substantially prevented by the combination of one or more thrust roller bearing 517 and the self-centering friction or traction roller-type transmission 520.

[0186] In the non-limitative embodiment of Figs. 20 and 21, the rotatable carrier 550 is single piece, i.e. the two supporting plates 551a, 551b are connected to one another. However, it is appreciated that, in an alternative embodiment, the supporting plates can be distinct components, as for the embodiments of Figs. 4 to 19. Similarly, a unitary rotatable carrier can be used with the embodiments of Figs. 4 to 19.

[0187] In some embodiments, the use of either the single deep groove ball bearing 317 or one or more thrust roller bearing 517 will provide an output assembly with sufficient stiffness to substantially prevent tilting of the output shaft, with at least one of: lower costs, less components, within less space, and lower weight.

[0188] In the non-limitative embodiments shown in Figs. 18 to 21, the stationary ring 426, 526 and the ring-shaped housing 470, 570 are two distinct components secured together. However, it is appreciated that, in an alternative embodiment (not shown), the stationary ring and the ring-shaped housing can be single piece or unitary, e.g. they can be cast or machined as a single component or welded together. Similarly, in the non-limitative embodiments shown in Figs. 18 to 21, the output shaft 413, 513 and the rotatable carrier 450, 550 are two distinct components secured together (e.g. the output shaft can be attached to the output supporting plate of the rotatable carrier via mechanical fasteners) in a manner such that they are engaged in rotation simultaneously. However, it is appreciated that, in an alternative embodiment (not shown), the output shaft and the rotatable carrier can be single piece or unitary, e.g. they can be cast or machined as a single component or welded together to be engaged in rotation simultaneously.

[0189] In the above description, an embodiment is an example or implementation of the inventions. The various appearances of “one embodiment,” “an embodiment” or “some embodiments” do not necessarily all refer to the same embodiments.

[0190] Although various features of the invention may be described in the context of a single embodiment, the features may also be provided separately or in any suitable combination. Conversely, although the invention may be described herein in the context of separate embodiments for clarity, the invention may also be implemented in a single embodiment.

[0191] Reference in the specification to “some embodiments”, “an embodiment”, “one embodiment” or “other embodiments” means that a particular feature, structure, or characteristic described in connection with the embodiments is included in at least some embodiments, but not necessarily all embodiments, of the inventions.

[0192] It is to be understood that the phraseology and terminology employed herein is not to be construed as limiting and are for descriptive purpose only.

[0193] The principles and uses of the teachings of the present invention may be better understood with reference to the accompanying description, figures and examples.

[0194] It is to be understood that the details set forth herein do not construe a limitation to an application of the invention.

[0195] Furthermore, it is to be understood that the invention can be carried out or practiced in various ways and that the invention can be implemented in embodiments other than the ones outlined in the description above.

[0196] It is to be understood that the terms “including”, “comprising”, “consisting” and grammatical variants thereof do not preclude the addition of one or more components, features, steps, or integers or groups thereof and that the terms are to be construed as specifying components, features, steps or integers.

[0197] If the specification or claims refer to “an additional” element, that does not preclude there being more than one of the additional element.

[0198] It is to be understood that where the claims or specification refer to “a” or “an” element, such reference is not to be construed that there is only one of that element.

[0199] It is to be understood that where the specification states that a component, feature, structure, or characteristic “may”, “might”, “can” or “could” be included, that particular component, feature, structure, or characteristic is not required to be included.

[0200] The descriptions, examples, methods and materials presented in the claims and the specification are not to be construed as limiting but rather as illustrative only.

[0201] Meanings of technical and scientific terms used herein are to be commonly understood as by one of ordinary skill in the art to which the invention belongs, unless otherwise defined.

[0202] Several alternative embodiments and examples have been described and illustrated herein. The embodiments of the invention described above are intended to be exemplary only. A person of ordinary skill in the art would appreciate the features of the individual embodiments, and the possible combinations and variations of the components. A person of ordinary skill in the art would further appreciate that any of the embodiments could be provided in any combination with the other embodiments disclosed herein. It is understood that the invention may be embodied in other specific forms without departing from the central characteristics thereof. The present examples and embodiments, therefore, are to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given herein. Accordingly, while the specific embodiments have been illustrated and described, numerous modifications come to mind. The scope of the invention is therefore intended to be limited solely by the scope of the appended claims.

Claims

CLAIMS:

1. A friction or traction roller-type transmission comprising:a stationary ring having an inner rolling surface defining an annular space; a sun wheel extending in the annular space and being concentric with the stationary ring, the sun wheel having an outer contacting surface; at least four rolling components located in the annular space between the sun wheel and the inner rolling surface of the stationary ring, the at least four rolling components comprising at least one flexible planetary wheel, at least one lateral support roller, and at least two guide rollers, each one of the at least one flexible planetary wheel having an outer surface contacting the outer contacting surface of the sun wheel and the inner rolling surface of the stationary ring, wherein the at least one lateral support roller has an outer contacting surface contacting the at least one flexible planetary wheel, the at least one lateral support roller comprising a lateral support roller pin with two opposed ends and a solid roller rotatably mounted to the lateral support roller pin, each one of the at least two guide rollers having an outer contacting surface contacting the outer contacting surface of the sun wheel and the inner rolling surface of the stationary ring, the at least two guide rollers being located on a respective side of the at least one lateral support roller and being spaced-apart from the outer contacting surface of the at least one lateral support roller, each one of the at least two guide rollers comprising a guide roller pin with two opposed ends and a solid roller rotatably mounted to the guide roller pin; anda rotatable carrier comprising at least one supporting plate with the at least four rolling components and the sun wheel being located on one side of the at least one supporting plate, wherein at least one of theopposed ends of each one of the guide roller pins and the lateral support roller pin is secured to a respective one of the at least one supporting plate.

2. The friction or traction roller-type transmission of claim 1, wherein the rotatable carrier comprises two of the at least one supporting plate, with the at least four rolling components and the sun wheel being located inbetween, and each one of the opposed ends of the lateral support roller pin and the guide roller pins being secured to a respective one of the supporting plates.

3. The friction or traction roller-type transmission of one of claims 1 and 2, wherein each one of the sun wheel, the stationary ring, the at least one flexible planetary wheel, the at least one lateral support roller, the at least two guide rollers, and the rotatable carrier has an axial axis, and all the axial axes extend parallel to one another.

4. The friction or traction roller-type transmission of claim 3, wherein the axial axes of the sun wheel, the stationary ring and the rotatable carrier are coaxial.

5. The friction or traction roller-type transmission of any one of claims 1 to 4, wherein the at least one flexible planetary wheel, the solid rollers of the at least two guide rollers, and the solid roller of the at least one lateral support roller are engageable in rotation by friction / traction contact.

6. The friction or traction roller-type transmission of any one of claims 1 to 5, wherein the outer contacting surfaces of the sun wheel, the at least one flexible planetary wheel, the solid roller of the at least one lateral support roller, the solid rollers of the at least two guide rollers, and the inner rolling surface of the stationary ring are smooth surfaces.

7. The friction or traction roller-type transmission of any one of claims 1 to 6, wherein each one of the at least one flexible planetary wheel is a hollow circular cylinder.

8. The friction or traction roller-type transmission of any one of claims 1 to 7, wherein the outer contacting surface of the solid roller of the at least one lateral support roller is spaced apart from the inner rolling surface of the stationary ring and from the outer contacting surface of the sun wheel.

9. The friction or traction roller-type transmission of any one of claims 1 to 8, wherein the lateral support roller pin is, prior to assembly, located inwardly of a respective nominal operating position when the friction or traction roller-type transmission is assembled.

10. The friction or traction roller-type transmission of any one of claims 1 to 9, wherein the at least one lateral support roller comprises at least two lateral support rollers, each one being located on a respective side of the at least one flexible planetary wheel and having an outer contacting surface contacting the outer surface of a respective adjacent one of the at least one flexible planetary wheel and wherein the at least two guide rollers are located on a side of outer ones of the at least two lateral support rollers, opposed to a side contacting the respective adjacent one of the at least one flexible planetary wheel.

11. The friction or traction roller-type transmission of any one of claims 1 to 10, wherein the at least two guide rollers are spaced-apart from the outer surface of the at least one flexible planetary wheel.

12. The friction or traction roller-type transmission of any one of claims 1 to 11, wherein the at least one flexible planetary wheel is slightly compressible and the solid rollers of the at least one lateral support roller and the at leasttwo guide rollers are incompressible in comparison to the at least one flexible planetary wheel.

13. A friction or traction roller-type transmission comprising:a stationary ring having an inner rolling surface defining an annular space; a sun wheel extending in the annular space and being concentric with the stationary ring, the sun wheel having an outer contacting surface; at least four rolling components located in the annular space between the sun wheel and the inner rolling surface of the stationary ring, the at least four rolling components comprising at least one flexible planetary wheel and at least one lateral support roller, each one of the at least one flexible planetary wheel having an outer surface contacting the outer contacting surface of the sun wheel and the inner rolling surface of the stationary ring, wherein the at least one lateral support roller has an outer contacting surface contacting the at least one flexible planetary wheel, the at least one lateral support roller comprising a lateral support roller pin with two opposed ends and a solid roller rotatably mounted to the lateral support roller pin;a rotatable carrier comprising at least one supporting plate with the at least four rolling components and the sun wheel being located on one side of the at least one supporting plate;at least three roller pins having opposed ends with at least one of the opposed ends being secured to a respective one of the at least one supporting plate, wherein at least one of the at least three roller pins is the lateral support roller pin of the at least one lateral support roller; andan output assembly comprising a ring-shaped housing mounted to the stationary ring and remaining stationary therewith, an output shaft connected to an output one of the at least one supporting plate andextending centrally through the ring-shaped housing and engaged in rotation therewith, at least one annular bearing extending between the ring-shaped housing and the output shaft to guide the output shaft during rotation, wherein the at least one annular bearing consists of one of a single deep groove ball bearing and at least one thrust roller bearing contacting at least one of an outer surface of the output one of the at least one supporting plate and the ring-shaped housing.

14. The friction or traction roller-type transmission of claim 13, wherein the at least one annular bearing consists of two axially spaced-apart thrust roller bearings wherein an inside one is sandwiched between an output surface of the output one of the at least one supporting plate and an inner surface of the ring-shaped housing and an outside one contacts the ring-shaped housing on an output surface thereof.

15. The friction or traction roller-type transmission of one of claims 13 and 14, wherein the at least four rolling components further comprises at least two guide rollers having an outer contacting surface contacting the outer contacting surface of the sun wheel and the inner rolling surface of the stationary ring, each one the at least two guide rollers being located on a side of the at least one lateral support roller and being spaced-apart from the outer contacting surface of the at least one lateral support roller, each one of the at least two guide rollers comprising a guide roller pin with two opposed ends and a solid roller rotatably mounted to the guide roller pin, wherein at least two of the at least three roller pins being the guide roller pins of the at least two guide rollers.

16. The friction or traction roller-type transmission of claim 15, wherein the at least two guide rollers are spaced-apart from the outer surface of the at least one flexible planetary wheel.

17. The friction or traction roller-type transmission of any one of claims 13 to 16, wherein the rotatable carrier comprises two of the at least one supporting plate, with the at least four rolling components and the sun wheel being located between the two supporting plates, and each one of the opposed ends of the at least three roller pins being secured to a respective one of the two supporting plates.

18. The friction or traction roller-type transmission of any one of claims 13 to 17, wherein the at least one lateral support roller comprises at least two lateral support rollers located on a respective side of the at least one flexible planetary wheel and having an outer contacting surface contacting the outer surface of a respective adjacent one of the at least one flexible planetary wheel.

19. The friction or traction roller-type transmission of any one of claims 13 to 18, wherein the at least one flexible planetary wheel is slightly compressible and the solid rollers of the at least one lateral support roller are incompressible in comparison to the at least one flexible planetary wheel.

20. The friction or traction roller-type transmission of any one of claims 13 to 19, wherein the outer contacting surface of the solid roller of the at least one lateral support roller is spaced apart from the inner rolling surface of the stationary ring and from the outer contacting surface of the sun wheel.

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