Hybrid torque transmission mechanism

A hybrid torque transmission mechanism (10) comprises a torque receiving component (30) and a torque output component (50) connected to each other, so that they are able to rotate synchronously. The torque receiving component (30) is configured to receive power from an electric motor or gearbox (70), which is then transferred to the torque output component (50), which may contain an output gear (58) to transfer power to an application. The torque receiving component (30) is fabricated using powder metallurgy to achieve sufficient tolerance. The torque output component (50) is fabricated using metal injection molding for high toughness.

CROSS REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit of Chinese Patent Application Serial No. 201310078291.1, filed on Mar. 12, 2013. The entire content of the aforementioned patent application is hereby incorporated by reference for all purposes.

BACKGROUND

Torque transmission mechanisms are used in many applications, such as, for example, in electric powered surgical cutters used in the medical field. Typical transmission mechanisms comprise an output gear connected an output end of a gearbox (e.g., a planetary gearbox) or electric motor, allowing for power from the gearbox or motor to be transferred to an application, such as a blade, fan, or wheel. The output gear may contain connection features in order to connect it to the output end of the gearbox, such as one or more connection holes interfacing with one or more corresponding connection columns connected to the output end of the gearbox.

Due to safety considerations, it is desirable for the output gears of torque transmission mechanisms, such as those used in surgical cutters, to have a high degree of toughness, so that they do not shatter or break when subjected to a large impact. In order to achieve the necessary toughness, the output gears may be manufactured using metal injection molding (MIM), as output gears created in this fashion generally exhibit the toughness necessary to withstand large impacts due to having low internal stress.

However, because MIM causes shrinkage during the manufacturing process, it is often difficult to create connection features (e.g., connection holes) having the precise tolerances needed to interface the output gear with the gearbox or motor. Thus these features typically require secondary processing, adding complexity to the manufacturing process and increasing the cost of the output gears.

Alternatively, powder metallurgy (PM) would enable the connection features to have the desirable tolerance precision without requiring secondary processing, thus lowering the cost and complexity of manufacturing. However, output gears manufactured using powder metallurgy are often too brittle, lacking the toughness required in many applications.

Accordingly, there exists a need for a lower-cost torque transmission mechanism with sufficient toughness and sufficient tolerance precision that is simple to manufacture.

SUMMARY

Some embodiments are directed towards a torque transmission mechanism for transferring torque from a motor or gearbox to an application, wherein the mechanism comprises a torque receiving component and a torque output component. The torque receiving component includes a first axial end configured to receive a torque input, and a second axial end having a structural feature. The torque output component includes a first axial end having a structural feature and a second axial end. The structural feature on the first axial end of the torque output component is configured to interface with the structural feature on the second axial end of the torque receiving component, such that the torque receiving component and torque output component are connected and are able to rotate synchronously. In some embodiments, the torque receiving component and torque output component are fabricated separately using different processes. For example, the torque receiving component may be created using powder metallurgy, while the torque output component may be created using metal injection molding.

DETAILED DESCRIPTION

Various features are described hereinafter with reference to the figures. It shall be noted that the figures are not drawn to scale, and that the elements of similar structures or functions are represented by like reference numerals throughout the figures. It shall also be noted that the figures are only intended to facilitate the description of the features for illustration and explanation purposes, unless otherwise specifically recited in one or more specific embodiments or claimed in one or more specific claims. The drawings figures and various embodiments described herein are not intended as an exhaustive illustration or description of various other embodiments or as a limitation on the scope of the claims or the scope of some other embodiments that are apparent to one of ordinary skills in the art in view of the embodiments described in the application. In addition, an illustrated embodiment need not have all the aspects or advantages shown.

An aspect or an advantage described in conjunction with a particular embodiment is not necessarily limited to that embodiment and may be practiced in any other embodiments, even if not so illustrated, or if not explicitly described. Also, reference throughout this specification to “some embodiments” or “other embodiments” means that a particular feature, structure, material, process, or characteristic described in connection with the embodiments is included in at least one embodiment. Thus, the appearances of the phrase “in some embodiments”, “in one or more embodiments”, or “in other embodiments” in various places throughout this specification are not necessarily referring to the same embodiment or embodiments.

FIGS. 1A and 1Billustrate a hybrid torque transmission mechanism10in accordance with some embodiments. Torque transmission mechanism10comprises a torque receiving component30and a torque output component50, which may be detachably connected to each other so that torque output component50is able to rotate synchronously with torque receiving component30. Preferably, torque output component50exhibits a high degree of toughness and torque receiving component30exhibits a high degree of tolerance precision. In some embodiments, torque receiving component30is formed using powder metallurgy (PM), and torque output component50is formed using metal injection molding (MIM).

In some embodiments, torque receiving component30and torque output component50are connected through a non-cylindrical interface formed between the two components. For example, one of torque receiving component30and torque output component50may comprise a protrusion having a non-circular cross-section, while the other component comprises a recess having a cross-section matching that of the protrusion, such that the projection may be accommodated within the recess. In the illustrated embodiments, torque output component50is illustrated as having a protrusion52, while torque receiving component30contains a corresponding recess32. However, it will be understood that in other embodiments, torque output component50may contain a recess, while torque receiving component30contains a corresponding protrusion.

In some embodiments, protrusion52is provided with at least one substantially arcuate surface and at least one substantially planar surface. Similarly, recess32is configured to have at least one arcuate surface and at least one planar surface corresponding to those on protrusion52, so that torque receiving component30and torque output component50are able to rotate synchronously together. In some embodiments, the at least one planar surface of protrusion52and the at least one planar surface of recess32are configured to interface with a loose fit for easy assembly. The at least one planar surface of protrusion52and the at least one planar surface of recess32may be configured to interface with a tight fit (e.g., abutting each other), to prevent detachment of torque receiving component30from torque output component50when protrusion52is fixed within recess32.

In accordance with a preferred embodiment, torque output component50contains protrusion52having two substantially parallel planar surfaces54connected by two arcuate surfaces56, as illustrated inFIG. 2A. It should be understood that the term “substantially,” such as in “substantially parallel” or “substantially planar,” is used herein to indicate certain features, can refer to either an exact feature (e.g., perfectly parallel, perfectly planar) or a feature that is slightly offset or otherwise not perfect (e.g., slightly offset from being perfectly parallel, slightly offset from being perfectly planar). Such offsets may be caused by the fabrication and manufacturing tolerances, slacks in various mating components or assemblies, wear and tear, or any combinations thereof may nonetheless cause some deviations from an exact feature. Therefore, one of ordinary skill in the art will clearly understand that the term “substantially” such as in “substantially parallel” or “substantially planar” is used here to incorporate at least such fabrication and manufacturing tolerances, the slacks in various mating components or assemblies, or any combinations thereof.

Torque receiving component30comprises a corresponding recess32. The shape of recess32matches that of protrusion52, so that protrusion52is able to be inserted within recess32, with arcuate surfaces56of protrusion52interfacing with corresponding arcuate surfaces of recess32with a loose fit, and planar surfaces54of protrusion52interfacing with corresponding planar surfaces of recess32with a tight fit.

It is understood different protrusion and recess shapes may be used in other embodiments. For example,FIG. 2Billustrates a torque output component50wherein protrusion52is substantially “D” shaped, having one planar surface and one arcuate surface. In other embodiments, it is understood that protrusion52may not be provided with at least one arcuate surface and at least one planar surface. For example,FIG. 2Cillustrates a torque output component50wherein protrusion52is substantially hexagonal, andFIG. 2Dillustrates a torque output component50with a substantially polygonal protrusion52. It will be understood that the illustrated shapes of protrusion52of torque output component50are not exhaustive, and are merely given for the purpose of example.

In some embodiments, at least a portion of the outer surface of torque output component50is provided with a plurality of output teeth forming an output gear58, allowing for the transfer of torque from the torque transmission mechanism10to a gear, rack, or other structure on an external application (e.g., a blade, fan, or other application). In other embodiments, other means of transmitting torque (e.g., a non-circular protrusion like protrusion52or a non-circular recess like recess32in torque receiving component30) may be used instead of output gear58.

Torque output component50may further comprise a bore or hole59extending in a axial direction thereof, as illustrated inFIG. 1B. Bore59functions to reduce the wall thickness of torque output component50, thereby decreasing the amount of shrinkage experienced during the MIM process to prevent unevenness in shrinkage, and lower material costs. In some embodiments, bore59is a blind bore; while in some other embodiments, bore59may be a through bore.

Torque receiving component30comprises, on an end remote from torque output component50, a plurality of structural features for interfacing with and receiving power from an output of a power source, such as a motor or a gearbox. In some embodiments as illustrated inFIG. 1B, the structural features comprise one or more connection holes34configured to interface with the ends of one or more connection columns36. The other end of connection columns36may be configured to interface with a power source such as, for example, the central axes of planet gears in a planetary gearbox. In a preferred embodiment, connection holes34are blind bores.

FIGS. 3A and 3Billustrate a torque receiving component30and a torque output component50, respectively, in accordance with another embodiment. In this embodiment, the interface surface between torque receiving component30and torque output component50comprises substantially cylindrical surfaces and non-cylindrical surfaces. In some embodiments, torque receiving component30and torque output component50are configured to interface at the cylindrical surfaces with a tight fit, and to interface at the non-cylindrical surfaces with a loose fit.

For example, as illustrated inFIG. 3A, recess32of torque receiving component30comprises a substantially cylindrical section322and a non-cylindrical section324. Likewise as illustrated inFIG. 3B, protrusion52of torque output component50comprises two sections, a substantially cylindrical section522and a non-cylindrical section524. In some embodiments, the radius of cylindrical section522is configured to be slightly larger than the largest radius of non-cylindrical section524, wherein the largest radius of second section524is defined as the largest distance between a point on the outer surface of non-cylindrical section524and the central axis of torque output component50.

When torque transmission mechanism10is assembled, cylindrical section522of protrusion52interfaces with cylindrical section322of recess32with a tight fit in order to fix torque receiving component30and torque output component50together, while non-cylindrical section524of protrusion52interfaces with non-cylindrical section324of recess32with a loose fit. Rotation of torque receiving component30drives the rotation of torque output component50; and the two components are able to rotate together.

FIGS. 4A and 4Billustrate torque transmission mechanism10comprising a torque receiving component30and a torque output component50connected to each other by welding in accordance with yet another embodiment. For example, as shown inFIG. 4B, torque receiving component30may comprise one more protrusions33on an end surface adjacent to where component30interfaces with torque output component50. During assembly, protrusions33may be laser welded onto an end surface of torque output component50.

FIG. 5illustrates torque transmission mechanism10in accordance with some embodiments interfacing with a planetary gearbox70, which may be used to reduce the rotation speed of a power source, e.g., an electric motor. In some embodiments, planetary gearbox70comprises a ring gear72housing a plurality of planetary gear stages. Each planetary gear stage comprises a sun gear74and a plurality of planet gears76, wherein planet gears76engage sun gear74and ring gear72. For purposes of explanation, the planetary gear stage of gearbox70located closest to the power source will be referred to as the first gear stage, and the planetary gear stage located closest to torque transmission mechanism10will be referred to as the last gear stage.

In some embodiments, sun gear74of the first gear stage may be attached, connected, or otherwise fixed to an output shaft80of the power source, e.g., an electric motor, in order to receive power from the power source. A plurality of planet gears76of the first gear stage are configured to spin around sun gear74, and are attached to a surface of a spinning frame78through a plurality of rods or columns79. In some embodiments, columns79interface with the central axes of the planet gears76(seeFIG. 5, wherein a portion of planetary gears76is cut away to show columns79). Sun gear74of the next gear stage is attached to the opposite end of spinning frame78. Thus the rotation of sun gear74of a gear stage is transferred to its associated planet gears76, and to sun gear74of a next gear stage through spinning frame78.

Planet gears76of the last gear stage, instead of being coupled to a spinning frame78, interface with torque receiving component30through connection columns36. For example, in some embodiments the ends of connection columns36extending outside connection holes34are configured to be inserted into the center holes of the planet gears76of the last gear stage of planetary gearbox70. Thus, power can be transferred from the power source through planetary gearbox70to torque receiving component30and torque output component50.

As illustrated inFIG. 5, torque receiving component30may be accommodated within an open end of inner gear ring72of planetary gearbox70remote from output shaft80of the power source. In some embodiments, as illustrated inFIG. 1B, torque receiving component30comprises a large radius portion37and a small radius portion38, with a step39formed there between. Ring gear72of planetary gearbox70may comprise a protrusion73(shown inFIG. 5) corresponding to step39, which divides ring gear72into an engaging portion722on the side of ring gear72closer to output shaft80, and an extended portion724on the side of ring gear72remote from output shaft80. Step39and protrusion73may be substantially annular or ring-shaped, wherein the width of step39corresponds to the length of protrusion73. At least a portion of engaging portion722comprises a plurality of gear teeth to interface with the planet gears76located inside ring gear72, while extended portion724may or may not have gear teeth.

During assembly, a sleeve60, illustrated inFIG. 6, may be inserted into extending portion724. Torque receiving component30is inserted into ring gear72from the end closer to output shaft80, such that step39and protrusion73are adjacent or abutting each other, with small radius portion38of torque receiving component30accommodated inside sleeve60. The remaining components of planetary gearbox70may then be assembled using conventional methods.

Sleeve60preferably comprises a wear-resistant material, such as a curled sheet of stainless steel. The sheet ends may be spaced slightly apart such that the circumference of sleeve60is not completely closed, forming a longitudinal slot62. When installing sleeve60into extended portion724of inner gear ring72, the surface of sleeve60may be elastically deformed, allowing for a tight fit between sleeve60and extended portion724of gear ring72. In some embodiments, an inner surface of sleeve60may be coated with a wear resistant material such as Teflon. It is understood that while the illustrated embodiment shows the use of a sleeve60, in other embodiments, a sleeve60may not be necessary.

In the present embodiments, torque receiving component30is fabricated using powder metallurgy, allowing for connection holes34or other connection features to be formed with the required tolerances without the need for secondary processing. This simplifies the manufacturing process while lowering material costs. On the other hand, torque output component50is fabricated using metal injection molding, which provides the toughness and the ability to withstand high impacts necessary for output gear58.

Present embodiments of a torque transmission mechanism may be used in applications requiring a high degree of safety. Embodiments are also suitable for limited or one-time use applications, such as in the drive mechanism for an organ removal knife used in the medical field.

In the foregoing specification, various aspects have been described with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of various embodiments described herein. For example, the above-described systems or modules are described with reference to particular arrangements of components. Nonetheless, the ordering of or spatial relations among many of the described components may be changed without affecting the scope or operation or effectiveness of various embodiments described herein. In addition, although particular features have been shown and described, it will be understood that they are not intended to limit the scope of the claims or the scope of other embodiments, and it will be clear to those skilled in the art that various changes and modifications may be made without departing from the scope of various embodiments described herein. The specification and drawings are, accordingly, to be regarded in an illustrative or explanatory rather than restrictive sense. The described embodiments are thus intended to cover alternatives, modifications, and equivalents.