Patent ID: 12215745

DETAILED DESCRIPTION

The invention can be implemented in numerous ways, including as a process; an apparatus; a system; a composition of matter; a computer program product embodied on a computer readable storage medium; and/or a processor, such as a processor configured to execute instructions stored on and/or provided by a memory coupled to the processor. In this specification, these implementations, or any other form that the invention may take, may be referred to as techniques. In general, the order of the steps of disclosed processes may be altered within the scope of the invention. Unless stated otherwise, a component such as a processor or a memory described as being configured to perform a task may be implemented as a general component that is temporarily configured to perform the task at a given time or a specific component that is manufactured to perform the task. As used herein, the term ‘processor’ refers to one or more devices, circuits, and/or processing cores configured to process data, such as computer program instructions.

A detailed description of one or more embodiments of the invention is provided below along with accompanying figures that illustrate the principles of the invention. The invention is described in connection with such embodiments, but the invention is not limited to any embodiment. The scope of the invention is limited only by the claims and the invention encompasses numerous alternatives, modifications and equivalents. Numerous specific details are set forth in the following description in order to provide a thorough understanding of the invention. These details are provided for the purpose of example and the invention may be practiced according to the claims without some or all of these specific details. For the purpose of clarity, technical material that is known in the technical fields related to the invention has not been described in detail so that the invention is not unnecessarily obscured.

A device for coupling equipment is disclosed (i.e., a ‘torque transferring coupler’). The torque transferring coupler comprises an inner cylinder, wherein the inner cylinder has a radial face comprising a first set of curved structures; and an outer cylinder, wherein the outer cylinder has an axial face comprising a second set of curved structures, wherein a coupling is formed in response to a section of the outer cylinder disposed to surround a portion of the inner cylinder and the first set of curved structures of the inner cylinder disposed to interlock with the second set of curved structures of the outer cylinder. In some embodiments, the first set of curved structures and the second set of curved structures have smoothly matching profiles (e.g., the profiles are wave-like, have no points of discontinuities, no sharp edges, etc.). In some embodiments, the smoothly matching profiles are not matching in horizontal regions of the curved structures (e.g., the horizontal regions are perpendicular to the axis of the coupler). In some embodiments, there is a spatial offset (e.g., no contact) for horizontal regions to reduce manufacturing tolerance requirements (e.g., in response a horizontal region or point contacting before a sloped surface due to inaccurate manufacturing, backlash would result for the coupler). In various embodiments, the sets of curved structures comprise wave-like splines (i.e., ‘wave splines’).

The disclosed torque transferring coupler (TTC) is useful in connecting equipment for the purpose of transmitting power and/or rotational motion. For example, the TTC is used to attach a shaft (e.g., a drive shaft) to an object (e.g., a driven shaft, a pulley, a gear, a flange, a wheel, etc.).

In some embodiments, the inner cylinder of the TTC continues to a longer shaft (e.g., a drive shaft). In some embodiments, the inner cylinder of the TTC is continuous with (i.e., is integral to) a longer shaft (e.g., a drive shaft). In some embodiments, the inner cylinder of the TTC is attached to a longer drive shaft (e.g., attached via a flange added to the inner cylinder below the wave splines). In various embodiments, the wave splines of the inner cylinder stand proud of, are flush with, are shy of the longer drive shaft's diameter, or any other appropriate relation between the wave splines and the inner cylinder. In various embodiments, the outer cylinder wave splines are shaped in the entire thickness of the outer cylinder, the inner surface of the outer cylinder, stand proud of the inner surface of the outer cylinder, are flush with the inner surface of the outer cylinder, are shy of the inner surface of the outer cylinder, or have any other appropriate relation with the surfaces of the outer cylinder.

The TTC is similar to a curvic coupling, in that there are torque-transmitting teeth, or splines, that provide a self-centering effect due to the angle of the splines all pointing towards the center. The difference is that curvic couplings typically have the splines on an axial face, whereas the disclosed device has the splines on a radial or cylindrical face. The curved structure, or wave-like, design of the TTC splines (i.e., wave splines) results in a low profile (e.g., it can fit in relatively thin-walled tube) that is easier and more cost effective to manufacture than traditional coupling designs (e.g., the TTC can be made in a standard live-tooling lathe, with the wave splines milled in with an orthogonal spindle head; or by using a 3-axis mill with 3-dimensional tool pathing). Manufacturing cost effectiveness is also gained by (i) allowing the use of lower cost/lower strength materials (as the large contact area of the wave splines results in reduced material stress), and (ii) reduced assembly tooling required.

Additionally, the wave-like design of the TTC splines results in minimal backlash, high radial torque transfer (e.g., by using steep-angled wave splines), ease of assembly, precise and repeatable positioning, and allows for multiple possible configurations (e.g., multiple axial offsets/positions and/or mistake-proof radial positioning).

In some embodiments, the TTC comprises an inner cylinder that is threaded. In some embodiments, the TTC further comprises a nut, wherein the nut is disposed to secure the coupling. The TTC embodiment comprising a threaded inner cylinder and matching nut is an improvement over coupling devices that require a large amount of torque (e.g., enough torque to cause friction for radial torque resistance) applied to the nut during assembly to obtain a large amount of radial torque resistance. For example, a traditional coupling mechanism that relies on friction under a bolt head to provide some torque resistance is very easy to assemble and manufacture, but torque resistance is typically low. As a specific example, consider a motor shaft that has a female threaded hole down the center of the shaft, then a pulley or gear with a through hole is slid on to the shaft, and a threaded bolt is used to clamp the pulley onto the motor shaft. Assembly of these types of coupling devices requires high performance tooling such as torque impact drivers, or manual torque wrenches and a fixture to hold the shaft to counteract the torque applied to the nut during assembly. In contrast, the disclosed TTC embodiment requires only a small amount of torque (e.g., enough torque to keep TTC from displacing axially and enabling the spline structure to apply torque, 10 Nm of torque or less, etc.) applied to the nut to gain the torque transfer advantages provided by the TTC's wave spline interface.

The TTC is also an improvement over other traditional coupling devices or methods (e.g., a flange coupling, a set screw, a keyway, a traditional spline, a shrink fit, a press fit, etc.). For example, a flange coupling, comprising two flanges fastened to each other (e.g., two flanges bolted together with a bolt pattern). In some instances, a flange coupling comprises through-holes in both flanges, wherein a bolt and nut or a bolt and threaded hole are used to fasten the two flanges together. However, the disadvantage of the two flanges bolted together is that the coupling requires a larger diameter in order to have enough room for the holes in the axial direction. In contrast, the TTC can be made with a significantly smaller overall maximum diameter because the torque transmitting features are a part of the shaft cylinder.

Set screws (e.g., as used in a coupling collar) applied radially to a drive shaft can dig in, galling the shaft, and are prone to slipping, especially under load reversal. In contrast, the TTC's interlocking wave splines distributes rotational torque over a large contact area, thereby reducing stress in the material and eliminating the galling issues associated with set screws. Additionally, the symmetry of the interlocking wave splines provides equivalent radial torque resistance when the load is driven in either rotational direction, thereby eliminating slippage even under load reversal.

A keyway experiences backlash during load reversal and is dependent on the precision of manufacturing (e.g., broaching, wire electrical discharge machining (EDM), etc.). Traditional splines—projections on a shaft (e.g., a rectangular key) that fit into slots or grooves on a corresponding shaft, hub, or wheel—are economically costly, and the female side of a traditional spline coupling requires special tooling during manufacture (e.g., broaching, plunge EDM, etc.). In contrast, the symmetry of the TTC's interlocking wave splines, the large contact area of the wave splines, and the precise positioning that comes from the design of the interlocking wave splines, together result in minimal backlash. As long as there is no contact at any of the horizontal points along the TTC's wave splines that would negate the interlocking of the inner and outer cylinder wave splines, and not allow the angled wave splines to be fully in contact, backlash is essentially eliminated. That is, any resultant backlash is minimal to the point of requiring high-precision measurement systems (e.g., a laser-based measurement system) to detect even the slightest amount of backlash—what the industry refers to as ‘zero-backlash’. Thus, the precision and cost of manufacturing of the wave spline design is considerably lessened in comparison to that required for the use of a keyway or traditional spline.

A shrink fit (e.g., a sweat fit) or a press fit require very tight dimensional tolerances to obtain the right amount of friction or grip in a coupling. Additionally, both methods require special tooling during assembly (e.g., an inductive heater, a blow torch, an oven, a hydraulic press, an arbor press, etc.). In contrast, the TTC depends on the contact between the interlocking wave splines and not friction as provided by a shrink or press fit. Additionally, the TTC is easy to assemble, requiring no special tooling during assembly.

In various embodiments, the inner cylinder, the outer cylinder, and/or the nut comprise one or more of the following materials: a metal, a plastic, a ceramic, and/or any other appropriate material. Other materials used to manufacture the TTC include surface-hardened (i.e., case-hardened) steel alloys. The hard outer layer of case-hardened steel alloys improves surface wear resistance of repeated installation/removal processes, but because the inner material remains relatively soft, it remains resistant to fracturing during high torque applications, cycling loads, or load reversals.

High strength steels are also common in high torque applications such as motor shafts and pair well with a minimally constrained application, where three points of Hertzian contact are used to transmit the rotational torque. Increasing the surface area of contact will increase torque resistance, but minimally constraining the outer cylinder around the inner cylinder with only three points of contact increases the clocking accuracy of the install. In the minimally constrained configuration, Hertzian contact stress is an appropriate method of measuring the stress induced during torque application.

Common plastics such as acrylonitrile butadiene styrene (ABS) are good low strength candidates. Due to the lower stiffness compared to metals, plastic construction pairs well with a high surface area configuration (i.e., a large contact area between opposing wave splines). A large contact surface area results in reduced material stress which means that for some applications, low strength, low-cost materials can be used in place of higher cost, higher strength materials. Aluminum is easy to machine and is a good middle ground candidate for the material selection of these parts; any configuration can be used, depending on the torque of the application.

FIG.1Ais a block diagram illustrating an embodiment of a torque transferring coupler. In the example shown, torque transferring coupler (TTC)100comprises inner cylinder102, outer cylinder108, and nut114. In some embodiments, nut114couples to inner cylinder102. Inner cylinder102comprises wave splines104and threaded region106. Outer cylinder108comprises flange110and wave splines112. In various embodiments, flange110is used to couple TTC100to a driven shaft, a pulley, a gear, a flange, a wheel, etc.

The wave splines112of outer cylinder108are disposed to interlock with wave splines104of inner cylinder102. Once wave splines104and wave splines112are interlocked (e.g., by positioning outer cylinder108around inner cylinder102), nut114is used to secure the coupling by being threaded onto threaded region106. In various embodiments, nut114comprises one of the following: a hexagonal nut, a square nut, a ring nut, a cap nut, a capstan nut, a dome nut, a wingnut, a thumb nut, etc. In some embodiments, only a small amount of install torque is needed to secure nut114to gain the advantages of the wave spline interface.

In some embodiments, torque applied to a nut or bolt, and its relation to preload is well understood, but friction creates large uncertainty. Unfortunately, friction causes significant variability in the amount of preload in a fastener even when extremely accurate torque is applied. Uncertainty can be somewhat reduced by using a low friction thread lubricant, but uncertainty will never be fully reduced due to friction under the head of the bolt. If we do not consider friction, the mechanical advantage of a threaded fastener is the circumference of the pitch circle divided by the thread pitch (e.g., 2*pi*radius of nut/thread pitch). If friction is considered, the useful mechanical advantage is typically reduced by about 90% due to thread running torque, as well as under-head torque. Even when accounting for things like thread lubricant, thread class, material, coefficient of friction, the scatter in achieved preload can be expected to vary by +/−30%.

In some embodiments, the torque required on the nut in order to get the wave splines to function must be high enough to ensure that the horizontal component of the normal force reacted by the force of the nut is greater than the horizontal component of the force experienced during the torque application. Adequately pre-loaded joints (e.g., where the preload exceeds the applied load) have better fatigue life than joints in which applied load exceeds preload. Exceeding the preload also causes gapping (which would induce backlash in this torque transferring coupler). Therefore it is critical to torque the top nut adequately, depending on how much torque the system will experience.

In some embodiments, there are two mechanisms at play that use mechanical advantage to magnify the amount of torque the coupling can resist: 1) the mechanical advantage of the threaded nut, which forces the interlocking wave splines together; this is equal to the circumference of the pitch circle divided by the thread pitch, where a larger cylinder diameter and finer pitch threads increase the mechanical advantage; and 2) the mechanical advantage of the angle of the wave splines; this is equal to the tangent of the angle of the splines, where steeper angled splines increase the mechanical advantage.

In some embodiments, an example of calculation results is as follows: 1) desired torque resistance (torque of the load)—271 Nm, 2) cylinder diameter—50.0 mm, 3) thread pitch—1.5 mm, 4) angle of splines—70.0 degrees, 5) friction knockdown 90%, 6) mechanical advantage of threaded connection (no friction)—104.7 (e.g., 2*pi*cylinder diameter/2)/thread pitch), 7) mechanical advantage of splines—2.7 (e.g., tan(angle of splines in radians)), 8) total mechanical advantage (no friction)—287.7 (e.g., the mechanical advantage of threaded connection (no friction)*mechanical advantage of splines), 9) total mechanical advantage (with friction)—28.8 (e.g., (1−friction knockdown)*mechanical advantage of threaded connection (no friction)*mechanical advantage of splines), and 10) required input torque on the nut (with friction)—9.4 Nm (e.g., desired torque resistance (torque of the load)/total mechanical advantage (with friction)).

In some embodiments, a locking feature on nut114provides additional security against nut114from coming loose. In various embodiments, nut114comprises one of the following: a tangential clamp nut, a nylon-insert lock nut, a castellated nut, a pair of jam nuts, a Stover lock nut, a two-way lock nut, a serrated flange lock nut, a K-lock nut, etc. In various embodiments, a separate locking feature is used in combination with nut114(e.g., a thread locker compound, a lockwasher, a cotter pin, etc.).

In various embodiments, inner cylinder102is a solid cylinder or a hollow cylinder. In various embodiments, a solid or hollow form of inner cylinder102is manufactured starting from bar stock (e.g., using a lathe to form the cylindrical shape). In various embodiments, a hollow form of inner cylinder102is manufactured by boring an inner region of solid bar stock or by starting with hollow tube stock (e.g., metal tube stock). In some embodiments, threaded region106of inner cylinder102is added using a lathe, a mill, a die, or by any other appropriate means. In various embodiments, inner cylinder102, wave splines104, and/or threaded region106are manufactured using a standard live-tooling lathe (e.g., with wave splines104milled in with an orthogonal spindle head), or by using a 3-axis mill with 3-dimensional tool pathing. In various embodiments, wave splines104are manufactured on a separate hollow cylinder that is attached or fused around a separate inner cylinder (e.g., by welding, heat fusing, shrink fitting, press fitting, or by any other appropriate means) so as to create inner cylinder102with the raised structure of wave splines104on the surface of inner cylinder102.

In some embodiments, wave splines104have a first wave profile and wave splines112have a second wave profile. In some embodiments, wave splines104and wave splines112interlock with a first point of wave splines104contacting a second point of wave splines112. In some embodiments, wave splines104and wave splines112interlock with a first section of wave splines104contacting a second section of wave splines112. In some embodiments, wave splines104and wave splines112interlock with a first line segment of wave splines104contacting a second line segment of wave splines112. In some embodiments, wave splines104and wave splines112interlock together providing a low backlash coupling.

FIG.1Bis a block diagram illustrating a side view of an embodiment of a torque transferring coupler. In some embodiments, TTC120comprises TTC100ofFIG.1A. In the example shown, TTC120comprises inner cylinder122with wave splines124, outer cylinder126with flange128and wave splines130, and nut132. In the example shown, wave splines124and wave splines130are interlocked by having positioned outer cylinder126around inner cylinder122. Nut132has been threaded onto a threaded region (not shown) of inner cylinder122to secure the coupling.

In the example shown, wave splines124are integral to inner cylinder122and stand shy of wave splines130. By making wave splines124shy of wave splines130, inner cylinder122maintains a low surface profile (e.g., relative to an integral longer drive shaft), one of the key characteristics of this assembly. In the example shown, wave splines130of outer cylinder126need to be thicker because there is no cylindrical support material (e.g., to provide radial torque resistance).

In various embodiments, wave splines124of inner cylinder122stand proud of wave splines130(in an interlocked configuration the outer surface of the wave splines124has a larger radius than the outer surface of the wave splines130), the wave splines124of the inner cylinder122are flush with wave splines130(in an interlocked configuration the outer surface of the wave splines124is radially aligned with the outer surface of the wave splines130), or the wave splines124of the inner cylinder122stand shy of the wave splines130(in an interlocked configuration the outer surface of the wave splines124has a smaller radius than the outer surface of the wave splines130), or any other appropriate relation between wave splines124and wave splines130.

In some embodiments, wave splines124and/or and wave splines130have a periodicity. In some embodiments, wave splines124and/or and wave splines130have a single frequency. In some embodiments, wave splines124and/or and wave splines130each comprise multiple frequencies. In some embodiments, wave splines124and/or and wave splines130each has a single amplitude. In some embodiments, wave splines124and/or and wave splines130each comprise multiple amplitudes.

FIG.1Cis a block diagram illustrating a perspective view of an embodiment of a torque transferring coupler. In some embodiments, TTC140comprises TTC100ofFIG.1A. In the example shown, TTC140is a perspective view of TTC120ofFIG.1B.

FIG.1Dis a block diagram illustrating an embodiment of a torque transferring coupler. In the example shown, torque transferring coupler (TTC)150comprises inner cylinder152, outer cylinder158, and nut164. In some embodiments, nut164couples to inner cylinder152. Inner cylinder152comprises wave splines154and threaded region156. Outer cylinder158comprises flange160and wave splines162. In various embodiments, flange160is used to couple TTC150to a driven shaft, a pulley, a gear, a flange, a wheel, etc.

The wave splines162of outer cylinder158are disposed to interlock with wave splines154of inner cylinder152. Once wave splines154and wave splines162are interlocked (e.g., by positioning outer cylinder158around inner cylinder152), nut164is used to secure the coupling by being threaded onto threaded region156. In various embodiments, nut164comprises one of the following: a hexagonal nut, a square nut, a ring nut, a cap nut, a capstan nut, a dome nut, a wingnut, a thumb nut, etc. In some embodiments, only a relatively small amount of install torque is needed to secure nut164to gain the advantages of the wave spline interface.

In some embodiments, torque applied to a nut or bolt, and its relation to preload is well understood, but friction creates large uncertainty. Unfortunately, friction causes significant variability in the amount of preload in a fastener even when extremely accurate torque is applied. Uncertainty can be reduced by using a low friction thread lubricant, but it will never be fully certain due to friction under the head of the bolt. For this reason, friction is ignored, as this assembly does not do anything to solve that problem. If we do not consider friction, the mechanical advantage of a threaded fastener is the circumference of the pitch circle divided by the thread pitch (e.g., 2*pi*radius of nut/thread pitch). If friction is not considered, the useful mechanical advantage is typically reduced by about 90% due to thread torque, as well as under-head torque. Even when accounting for things like thread lubricant, thread class, material, coefficient of friction, the scatter in achieved preload can be expected to vary by +/−30%.

In some embodiments, the torque required on the nut to get the wave splines to work to ensure that the horizontal component of the normal force reacted by the force of the nut is greater than the horizontal component of the force experienced during the torque application. Adequately pre-loaded joints (e.g., where the preload exceeds the applied load) have better fatigue life than joints in which applied load exceeds preload. Exceeding the preload also causes gapping (which would induce backlash in this torque transferring coupler). Therefore it is critical to torque the top nut adequately, depending on how much torque the system will experience.

In some embodiments, there are two mechanisms at play that use mechanical advantage to magnify the amount of torque the coupling can resist: 1) the mechanical advantage of the threaded nut, which forces the interlocking wave splines together; this is equal to the circumference of the pitch circle divided by the thread pitch, where a larger cylinder diameter and finer pitch threads increase the mechanical advantage; and 2) the mechanical advantage of the angle of the wave splines; this is equal to the tangent of the angle of the splines, where steeper angled splines increase the mechanical advantage.

In some embodiments, an example of calculation results is as follows: 1) desired torque resistance (torque of the load)—271 Nm, 2) cylinder diameter—50.0 mm, 3) thread pitch—1.5 mm, 4) angle of splines—70.0 degrees, 5) friction knockdown 90%, 6) mechanical advantage of threaded connection (no friction)—104.7, 7) mechanical advantage of splines—2.7, 8) total mechanical advantage (no friction)—287.7, 9) total mechanical advantage (with friction)—28.8, and 10) required input torque on the nut (with friction)—9.4 Nm.

In some embodiments, a locking feature on nut164provides additional security against nut164from coming loose. In various embodiments, nut164comprises one of the following: a tangential clamp nut, a nylon-insert lock nut, a castellated nut, a pair of jam nuts, a Stover lock nut, a two-way lock nut, a serrated flange lock nut, a K-lock nut, etc. In various embodiments, a separate locking feature is used in combination with nut164(e.g., a thread locker compound, a lockwasher, a cotter pin, etc.).

In various embodiments, inner cylinder152is a solid cylinder or a hollow cylinder. In various embodiments, a solid or hollow form of inner cylinder152is manufactured starting from bar stock (e.g., using a lathe to form the cylindrical shape). In various embodiments, a hollow form of inner cylinder152is manufactured by boring an inner region of solid bar stock or by starting with hollow tube stock (e.g., metal tube stock). In some embodiments, threaded region156of inner cylinder152is added using a lathe, a mill, a die, or by any other appropriate means. In various embodiments, inner cylinder152, wave splines154, and/or threaded region156are manufactured using a standard live-tooling lathe (e.g., with wave splines154milled in with an orthogonal spindle head), or by using a 3-axis mill with 3-dimensional tool pathing. In various embodiments, wave splines154are manufactured on a separate hollow cylinder that is attached or fused around a separate inner cylinder (e.g., by welding, heat fusing, shrink fitting, press fitting, or by any other appropriate means) so as to create inner cylinder152with the raised structure of wave splines154on the surface of inner cylinder152.

As shown inFIG.1D, the inner cylinder152comprises an upper portion comprising the threaded region156, a central portion153, and a lower portion comprising the wave splines154. An upper axial face155of the wave splines154is defined by an upper outer edge155aand an upper inner edge155balong which the central portion153and the wave splines154connect. The upper axial face155of the wave splines154has a uniform radial thickness defined by the radial distance between the upper inner edge155band the upper outer edge155a. The axial length of the lower portion of the inner cylinder152varies in an oscillating manner as the inner cylinder rotates about its axis to form a first wave profile corresponding to the curved structures or wave-like shapes of the wave splines154.

As further shown inFIG.1D, the outer cylinder158comprises an upper portion comprising a flange160, a central portion161, and a lower portion comprising the wave splines162. A lower axial face163of the wave splines162is defined by a lower outer edge163aand a lower inner edge163b. The lower axial face163of the wave splines162has a uniform radial thickness defined by the radial distance between the lower inner edge163band the lower outer edge163a. The axial length of the lower portion of the outer cylinder158varies in an oscillating manner as the outer cylinder rotates about its axis to form a second wave profile corresponding to the curved structures or wave-like shapes of the wave splines162.

In various embodiments, the first wave profile and the second wave profile have different shapes. The embodiment shown inFIGS.1A-1Cshow wave profiles comprising waves having a single frequency and a single amplitude. The embodiments ofFIGS.1D,1E,2A,2B, and6A-6Dshow wave profiles comprising horizontal portions and waves having a single amplitude. The embodiments ofFIGS.2C and2Dshow wave profiles comprising steep-angled splines having longer periodicities, lower frequencies, and higher amplitudes than the wave splines shown inFIGS.2A and2B. The embodiment ofFIGS.5A-5Bshows wave profiles having multiple frequencies and multiple amplitudes.

In some embodiments, wave splines154have a first wave profile and wave splines162have a second wave profile. In some embodiments, wave splines154and wave splines162interlock with a first point of wave splines154contacting a second point of wave splines162. In some embodiments, wave splines154and wave splines162interlock with a first section of wave splines154contacting a second section of wave splines162. In some embodiments, wave splines154and wave splines162interlock with a first line segment of wave splines154contacting a second line segment of wave splines162. In some embodiments, wave splines154and wave splines162interlock together providing a low backlash coupling.

FIG.1Eis a block diagram illustrating a side view of an embodiment of a torque transferring coupler. In some embodiments, TTC170comprises TTC150ofFIG.1D. In the example shown, TTC170comprises inner cylinder172with wave splines174, outer cylinder176with flange178and wave splines180, and nut182. In the example shown, wave splines174and wave splines180are interlocked by having positioned outer cylinder176around inner cylinder172. Nut182has been threaded onto a threaded region (not shown) of inner cylinder172to secure the coupling.

In the example shown, wave splines174are integral to inner cylinder172and stand shy of wave splines180. By making wave splines174shy of wave splines180, inner cylinder172maintains a low surface profile (e.g., relative to an integral longer drive shaft), one of the key characteristics of this assembly. In the example shown, wave splines180of outer cylinder176need to be thicker because there is no cylindrical support material (e.g., to provide radial torque resistance).

In some embodiments, horizontal region186and horizontal region184of the wave splines180and wave splines174are not in contact for TTC170. This enables zero backlash coupling between inner cylinder172and outer cylinder176.

In various embodiments, wave splines174of inner cylinder172stand proud of wave splines180(in an interlocked configuration the outer surface of the wave splines174has a larger radius than the outer surface of the wave splines180), the wave splines174of the inner cylinder172are flush with wave splines180(in an interlocked configuration the outer surface of the wave splines174is radially aligned with the outer surface of the wave splines180), or the wave splines174of the inner cylinder172stand shy of the wave splines180(in an interlocked configuration the outer surface of the wave splines174has a smaller radius than the outer surface of the wave splines180), or any other appropriate relation between wave splines174and wave splines180.

In some embodiments, wave splines174and/or and wave splines180have a periodicity. In some embodiments, wave splines174and/or and wave splines180have a single frequency. In some embodiments, wave splines174and/or and wave splines180each comprise multiple frequencies. In some embodiments, wave splines174and/or and wave splines180each has a single amplitude. In some embodiments, wave splines124and/or and wave splines130each comprise multiple amplitudes.

FIG.1Fis a block diagram illustrating a perspective view of an embodiment of a torque transferring coupler. In some embodiments, TTC190comprises TTC150ofFIG.1D. In the example shown, TTC190is a perspective view of TTC170ofFIG.1E.

FIG.2Ais a block diagram illustrating a side view of an embodiment of an inner cylinder with shallow-angled splines. In some embodiments, inner cylinder with shallow-angled splines200comprises inner cylinder102, wave splines104, and threaded region106ofFIG.1A. In the example shown, inner cylinder with shallow-angled splines200comprises inner cylinder202, shallow-angled splines204, and threaded region206. In the example shown, shallow-angled splines204have a longer periodicity, a lower frequency, and a lower amplitude than wave splines124shown inFIG.1B. In some embodiments, shallow-angled splines204have a smoothly varying profile (e.g., the profile is wave-like, has no points of discontinuities, no sharp edges, etc.) to allow smooth rotational motion between inner cylinder202and an outer cylinder as the two are put together to form a coupling. In various embodiments, shallow-angled splines204comprise wave-like splines (i.e., ‘wave splines’).

In the example shown, shallow-angled splines204stand proud of inner cylinder202(i.e., shallow-angled splines204present a raised surface profile that sticks out from inner cylinder202, in an interlocked configuration the radius of the outer surface of the shallow-angled splines204is larger than the radius of the outer surface of the inner cylinder202). In some embodiments, typical spline thicknesses are 1-3 mm. In various embodiments, the amount that shallow-angled splines204stand proud from inner cylinder202(i.e., the thickness of shallow-angled splines204) is the same or different as the thickness of the splines of an outer cylinder comprising part of a complete TTC device (not shown).

In various embodiments, inner cylinder202is a solid cylinder or a hollow cylinder. In various embodiments, a solid or hollow form of inner cylinder202is manufactured starting from bar stock (e.g., using a lathe to form the cylindrical shape). In various embodiments, a hollow form of inner cylinder202is manufactured by boring an inner region of solid bar stock or by starting with hollow tube stock (e.g., metal tube stock). In some embodiments, the threaded region206of inner cylinder202is added using a lathe, a mill, a die, or by any other appropriate means. In various embodiments, inner cylinder202, shallow-angled splines204, and/or threaded region206are manufactured using a standard live-tooling lathe (e.g., with shallow-angled splines204milled in with an orthogonal spindle head), or by using a 3-axis mill with 3-dimensional tool pathing. In various embodiments, shallow-angled splines204are manufactured on a separate hollow cylinder that is attached or fused around a separate inner cylinder (e.g., by welding, heat fusing, shrink fitting, press fitting, or by any other appropriate means) so as to create inner cylinder202with the raised structure of shallow-angled splines204on the surface of inner cylinder202.

In various embodiments, shallow-angled splines204are manufactured on a separate hollow cylinder that comprises the same or different material as inner cylinder202. For example, shallow-angled splines204are manufactured from ABS tube stock that is fused around inner cylinder202, wherein inner cylinder202comprises round aluminum bar stock that has been machined on a lathe to add threaded region206. In some embodiments, shallow-angled splines204are designed to interlock with the splines of an outer cylinder comprising part of a complete TTC device (not shown).

FIG.2Bis a block diagram illustrating a perspective view of an embodiment of an inner cylinder with shallow-angled splines. In some embodiments, inner cylinder with shallow-angled splines220comprises inner cylinder102, wave splines104, and threaded region106ofFIG.1A. In the example shown, inner cylinder with shallow-angled splines220is a perspective view of inner cylinder with shallow-angled splines200ofFIG.2A.

FIG.2Cis a block diagram illustrating a side view of an embodiment of an inner cylinder with steep-angled splines. In some embodiments, inner cylinder with steep-angled splines240comprises inner cylinder102, wave splines104, and threaded region106ofFIG.1A. In the example shown, inner cylinder with steep-angled splines240comprises inner cylinder242, steep-angled splines244, and threaded region246. In the example shown, steep-angled splines244have a longer periodicity, a lower frequency, and a higher amplitude than wave splines204shown inFIG.2A.

In some embodiments, steep-angled splines244have a smoothly varying profile (e.g., the profile is wave-like, has no points of discontinuities, no sharp edges, etc.) to allow smooth rotational motion between inner cylinder242and an outer cylinder as the two are put together to form a coupler. In various embodiments, steep-angled splines244comprise wave-like splines (i.e., ‘wave splines’).

In the example shown, steep-angled splines244stand proud of inner cylinder242(i.e., steep-angled splines244present a raised surface profile that sticks out from inner cylinder242, in an interlocked configuration the radius of the outer surface of the shallow-angled splines244is larger than the radius of the outer surface of the inner cylinder242). In various embodiments, the amount that steep-angled splines244stand proud from inner cylinder242(i.e., the thickness of steep-angled splines244) is the same as or is different from the thickness of the splines of an outer cylinder comprising part of a complete TTC device (not shown).

In various embodiments, inner cylinder242is a solid cylinder or a hollow cylinder. In various embodiments, a solid or hollow form of inner cylinder242is manufactured starting from bar stock (e.g., using a lathe to form the cylindrical shape). In various embodiments, a hollow form of inner cylinder242is manufactured by boring an inner region of solid bar stock or by starting with hollow tube stock (e.g., metal tube stock). In some embodiments, the threaded region246of inner cylinder242is added using a lathe, a mill, a die, or by any other appropriate means. In various embodiments, inner cylinder242, steep-angled splines244, and/or threaded region246are manufactured using a standard live-tooling lathe (e.g., with steep-angled splines244milled in with an orthogonal spindle head), or by using a 3-axis mill with 3-dimensional tool pathing. In various embodiments, steep-angled splines244are manufactured on a separate hollow cylinder that is attached or fused around a separate inner cylinder (e.g., by welding, heat fusing, shrink fitting, press fitting, or by any other appropriate means) so as to create inner cylinder242with the raised structure of steep-angled splines244on the surface of inner cylinder242.

In various embodiments, steep-angled splines244are manufactured on a separate hollow cylinder that comprises the same or different material as inner cylinder242. For example, steep-angled splines244are manufactured from ABS tube stock that is fused around inner cylinder242, wherein inner cylinder242comprises round aluminum bar stock that has been machined on a lathe to add threaded region246. In some embodiments, steep-angled splines244are designed to interlock with the splines of an outer cylinder comprising part of a complete TTC device (not shown).

FIG.2Dis a block diagram illustrating a perspective view of an embodiment of an inner cylinder with steep-angled splines. In some embodiments, inner cylinder with steep-angled splines260comprises inner cylinder102, wave splines104, and threaded region106ofFIG.1A. In the example shown, inner cylinder with steep-angled splines260is a perspective view of inner cylinder with steep-angled splines240ofFIG.2C.

FIG.3Ais a block diagram illustrating a side view of an embodiment of a torque transferring coupler. In some embodiments, TTC300comprises TTC100ofFIG.1A. In the example shown, TTC300comprises inner cylinder302with wave splines304, outer cylinder306with wave splines308and flange310, and nut312. In the example shown, wave splines304and wave splines308are interlocked by having positioned outer cylinder306around inner cylinder302. Wave splines304and wave splines308do not have any sharp points or discontinuities so that when inner cylinder302is rotated against outer cylinder306it can be smoothly set to a position enabling torque transfer when coupled. Nut312has been threaded onto a threaded region (not shown) of inner cylinder302to secure the coupling. In the example shown, wave splines304and wave splines308illustrate another embodiment of wave spline profiles as compared to the wave spline profiles shown inFIGS.1A,2A, and2C. Line314(labeled with A's on either end) indicates the plane of a cross-sectional view of TTC300that is revealed inFIG.3B.

FIG.3Bis a block diagram illustrating a cross-sectional view of an embodiment of a torque transferring coupler. In some embodiments, TTC320comprises TTC100ofFIG.1A. In the example shown, TTC320is a cross-sectional view of TTC300corresponding to line314(labeled with A's on either end) ofFIG.3A. In the example shown, TTC320comprises inner cylinder322, outer cylinder324with flange326, and nut330. Lip328provides torque resistance to the axial force applied to flange326when securing the coupling via nut330.

FIG.4Ais a block diagram illustrating applied and reactive forces in an embodiment of a torque transferring coupler with shallow-angled splines. In some embodiments, TTC400comprises TTC100ofFIG.1A. In the example shown, TTC400comprises outer cylinder402with wave splines403and flange404, inner cylinder405with shallow-angled splines406, and nut407. In the example shown, arrow408indicates the axial force applied by nut407onto flange404. Arrow410indicates the axial force transferred by flange404onto point of contact409between wave splines403and shallow-angled splines406. Arrow412indicates the reactive force to the axial force applied to point of contact409(i.e., the axial force applied as indicated by arrow410). Line414is shown at the angle of contact between wave splines403and wave splines406. Arrow416indicates the normal force perpendicular to line414. Arrow418indicates the torque resistant force provided by TTC400when nut407has secured the coupling. Resistance to rotation between inner cylinder405and outer cylinder402is not solely dependent on friction or locking of nut407against flange404. Instead, the structures of wave splines403and wave splines406, in conjunction with the axial force, enable resistance to relative rotation between inner cylinder405and outer cylinder402. In the example shown, the limited points of contact between wave splines403and wave splines406results in precise axial positioning of flange404of outer cylinder402with respect to inner cylinder405.

Note that the wave spline structures (e.g., wave splines403and wave splines406) enable resistance to relative rotation in both rotational directions and can thereby enable a zero-backlash coupling between an inner cylinder and an outer cylinder (e.g., inner cylinder405and outer cylinder402). In other words, since there is no contact on the horizontal spline surfaces shown here, there is guaranteed contact on the sloped portions of spline surfaces, which is what provides the zero-backlash, torque resistance.

FIG.4Bis a block diagram illustrating applied and reactive forces in an embodiment of an inner cylinder with steep-angled splines of a TTC. In some embodiments, portion of TTC420comprises an inner cylinder, wave splines426, and threaded region. In the example shown, arrow422indicates the axial force applied to wave spline426(e.g., the axial force applied by a nut and transferred via a flange of an outer cylinder). Arrow424indicates the reactive force to the applied axial force (i.e., the axial force applied as indicated by arrow422). Line428is shown at the angle of wave spline426. Arrow430indicates the normal force perpendicular to line428. Arrow432indicates the torque resistant force provided by portion of TTC420(e.g., when an outer cylinder with matching wave splines has been installed and secured around inner cylinder with steep-angled splines of portion of TTC420). Note for the same axial force applied, as indicated by arrow422, the torque resistant force432provided by wave splines426is much larger in comparison to the torque resistant force418provided by the shallow-angled splines412ofFIG.4A.

In the example shown, the steep angle of the splines, as shown by line428, provides a mechanical advantage, similar to the properties of a wedge. For example, for a steep-angled log-splitting wedge, only a small input force from a hammer is needed to split the wood, because the angle of the wedge magnifies the outward force on the wood. Steeper angles result in a higher outward force multiplier. Relating that principle to the steep-angled splines shown inFIG.4B, applying too much torque to a nut used to secure an outer cylinder with matching wave splines around inner cylinder with steep-angled splines, would increase the force experienced at the contact interface, as indicated by arrow422, so much that it could yield the material just during install. So, for a portion of TTC420, less install torque is required on the nut. That is, a nut installed at low torque (so the material is not close to yielding) can provide a large amount of radial torque resistance due to the large contact surface area provided by a portion of TTC420. For a given radial torque, higher contact surface area means less stress in the material. In various embodiments, the angles of the wave splines can be tuned depending on the torque requirements of a given application.

FIG.4Cis a block diagram illustrating forces applied to an embodiment of an inner cylinder with steep-angled splines of a TTC. In some embodiments, portion of TTC440comprises an inner cylinder, wave splines442, and a threaded region. In the example shown, line444is shown at the angle of wave splines442. Arrow446indicates the normal force perpendicular to line444. Arrow448indicates the radial force applied to wave spline442from a torque transfer—for example, when portion of TTC440is used as part of a complete TTC that is installed and used in a torque transferring operation (e.g., when driving a driven shaft, wheel, pulley, gear, etc.). Arrow450indicates the axial force at the contact interface resultant from the radial force applied to wave splines442from a torque transfer. That is, the steeper the splines, the closer to “perpendicular to the direction of torque transfer” they are, which reduces the amount of force experienced at the wave spline contact interface. Also with steeper wave splines, the magnitude of the forces indicated by arrow446and arrow448become closer to each other, which is favorable for high torque applications, in that most of the reacted normal force is contributing to the useful torque transfer to the load.

In some embodiments, the steepness of the splines compared to the shallowness of the splines may add more uncertainty to the relative axial position of the inner cylinder to the outer cylinder as the seated position of the inner cylinder wave splines to the outer cylinder wave splines may have more uncertainty with a steeper slope.

In some embodiments, the inner cylinder wave splines have different amplitudes compared to the outer cylinder wave splines so that the splines do not bottom out when securely seated with respect to each other.

FIG.5Ais a block diagram illustrating an embodiment of a dual-height torque transferring coupler. In some embodiments, TTC500comprises TTC100ofFIG.1A. In the example shown, torque transferring coupler (TTC)500comprises inner cylinder502, outer cylinder510, and nut520. In some embodiments, nut520couples to inner cylinder502(e.g., by being threaded onto threaded region508). Inner cylinder502comprises splines504of a first height, splines506of a second height, and threaded region508. Outer cylinder510comprises flange512and multiple splines that mesh with the splines of inner cylinder502(e.g., spline514, spline516, and spline518). In various embodiments, flange512is used to couple TTC500to a driven shaft, a pulley, a gear, a flange, a wheel, etc.

Spline514and spline516of outer cylinder510are disposed to interlock with either splines504or splines506of inner cylinder502. In the example of spline514and spline516interlocking with splines504, flange512of outer cylinder510is disposed axially at a first height. In the example of spline514and spline516interlocking with splines506, flange512of outer cylinder510is disposed axially at a second height. Once splines504and splines506are interlocked (e.g., by positioning outer cylinder510around inner cylinder502), nut520is used to secure the coupling by being threaded onto threaded region508.

In various embodiments, the splines are designed to create one or more axial offsets—for example, two axial coupling positions, three axial coupling positions, four axial coupling positions, or any other appropriate number of axial coupling positions.

In some embodiments, splines504, splines506, and splines514, splines516are smooth and do not have any sharp discontinuities so that outer cylinder510and inner cylinder502can rotate smoothly with respect to one another to enable simple relative positioning between inner cylinder502and outer cylinder510.

FIG.5Bis a block diagram illustrating an embodiment of a dual-height torque transferring coupler positioned at a first height. In some embodiments, TTC530comprises TTC100ofFIG.1A. In the example shown, TTC530comprises inner cylinder532, outer cylinder538, and nut548. In some embodiments, nut548couples to inner cylinder532(e.g., by being threaded onto a threaded region of inner cylinder532). Inner cylinder532comprises splines534of a first height, splines536of a second height. Outer cylinder538comprises flange540and multiple splines that mesh with the splines of inner cylinder532(e.g., spline542, spline544, and spline546). In various embodiments, flange540is used to couple TTC530to a driven shaft, a pulley, a gear, a flange, a wheel, etc.

In the example shown, spline542and spline544are interlocked with splines534, while spline544and spline546are interlocked with splines536, thereby positioning flange540axially at a first height. Nut548has secured the coupling by being threaded onto a threaded region of inner cylinder532(not shown).

FIG.5Cis a block diagram illustrating an embodiment of a dual-height torque transferring coupler positioned at a second height. In some embodiments, TTC550comprises TTC100ofFIG.1A. In the example shown, TTC550comprises TTC530ofFIG.5B, wherein spline542and spline544are interlocked with splines536, thereby positioning flange axially at a second height.

FIG.5Dis a block diagram illustrating points of contact in an embodiment of a dual-height torque transferring coupler positioned at a first and second height. In some embodiments, TTC560comprises TTC100ofFIG.1A. In the example shown, outer cylinder562is shown positioned relative to inner cylinder564at a first height (i.e., a first axial position) via spline points-of-contact566, and outer cylinder562is shown positioned relative to inner cylinder564at a second height (i.e., a second axial position) via spline points-of-contact568. The two different spline points-of-contact566and568enable a height differential570for flange572(i.e., flange572can be positioned in either of two different axial positions separated by height differential570).

FIG.5Eis a block diagram illustrating the clearance within an embodiment of a dual-height torque transferring coupler positioned at a first height. In some embodiments, TTC580comprises TTC100ofFIG.1A. In the example shown, TTC580comprises TTC560ofFIG.5D. Clearance582is what guarantees contact at the sloped portions of the spline surfaces (i.e., at spline points-of-contact562), and thus provides zero-backlash, torque resistance for the first axial position of TTC560ofFIG.5D.

FIG.6Ais a block diagram illustrating an embodiment of a mistake-proof torque transferring coupler. In some embodiments, TTC600comprises TTC100ofFIG.1A. In the example shown, TTC600comprises outer cylinder with splines606and inner cylinder with splines602. In the example shown, positioning arrow604and positioning arrow608illustrate proper radial alignment of outer cylinder with splines606and inner cylinder with splines602prior to securing the coupling (i.e., proper radial alignment is achieved when the arrow ends of positioning arrow604and positioning arrow608are aligned).

In some embodiments, positioning arrow604and positioning arrow608are physically marked (e.g., embossed, debossed, painted, etc.) on outer cylinder with splines606and inner cylinder with splines602(e.g., to provide visual positioning information to a coupling assembler). In some embodiments, there are no positioning arrows marked on outer cylinder with splines606and inner cylinder with splines602.

In the example shown, positioning arrow604and positioning arrow608are shown for illustration purposes and are not required to achieve proper radial alignment of outer cylinder with splines606and inner cylinder with splines602. This is due to the mistake-proof spline design of TTC600, wherein there is only one way to physically position outer cylinder with splines606and inner cylinder with splines602when assembling and securing the coupling. In the example shown, this is achieved by creating one long horizontal spline (as indicated by positioning arrow608) whereas the other splines of outer cylinder with splines606are part of an otherwise continuous wave profile. In various embodiments, a mistake-proof TTC can be implemented by using any other appropriate spline design that provides a break in an otherwise symmetric spline profile.

FIG.6Bis a block diagram illustrating a perspective view of an embodiment of a mistake-proof torque transferring coupler. In some embodiments, TTC620comprises TTC100ofFIG.1A. In the example shown, TTC620comprises TTC600ofFIG.6A, but because of the perspective view of TTC620, nut622(not shown inFIG.6A) is revealed. In some embodiments, nut620is used to secure TTC600(i.e., nut620is used to secure outer cylinder with splines606ofFIG.6Ato inner cylinder with splines602ofFIG.6A).

FIG.6Cis a block diagram illustrating a side view of an embodiment of a mistake-proof torque transferring coupler in the coupled position. In some embodiments, TTC620comprises TTC100ofFIG.1A. In the example shown, TTC640comprises TTC600ofFIG.6A. In the example shown, TTC640comprises outer cylinder with splines646and inner cylinder with splines642. The alignment of positioning arrow644and positioning arrow648illustrates that proper radial alignment of outer cylinder with splines646and inner cylinder with splines642has been achieved. Nut650is shown having secured TTC640(i.e., outer cylinder with splines646has been coupled to inner cylinder with splines642).

FIG.6Dis a block diagram illustrating a perspective view of an embodiment of a mistake-proof torque transferring coupler in the coupled position. In some embodiments, TTC660comprises TTC100ofFIG.1A. In the example shown, TTC660comprises TTC640ofFIG.6Cshown in a perspective view.

FIG.7Ais a block diagram illustrating an embodiment of a torque transferring coupler as part of a stepper motor assembly. In the example shown, the stepper motor with gear assembly700comprises stepper motor702, drive shaft704, wave splines706, threaded region708, gear710, outer cylinder with wave splines712, and nut714. In some embodiments, drive shaft704with wave splines706and threaded region708, along with outer cylinder with wave splines712and nut714, comprise TTC100ofFIG.1A, wherein flange110ofFIG.1Ahas been replaced by gear710. In some embodiments, gear710is integral with outer cylinder with wave splines712(e.g., gear710and outer cylinder with wave splines712is manufactured from a single piece of metal stock). In some embodiments, gear710is manufactured separately from outer cylinder with wave splines712. In some embodiments, gear710is attached to outer cylinder with wave splines712(e.g., attached with a key, by welding, heat fusing, shrink fitting, press fitting, or by any other appropriate means). In the example shown, gear710is coupled to drive shaft704by a TTC comprising wave splines706, threaded region708, outer cylinder with wave splines712, and nut714. In various embodiments, stepper motor702with gear710is used to drive a driven shaft, a driven gear (e.g., a gear that fits the teeth pattern of gear710), a belt or chain (e.g., a belt or chain used to couple to a driven shaft or driven gear), or to drive and/or precisely position a pan tilt unit, an antenna, a telescope, a camera (e.g., a security camera, a surveillance camera, an infrared camera, etc.), a zoom lens mechanism, a valve control, a hard disk drive, a robot, a vending machine feed or delivery system, a production line, or any other appropriate use.

FIG.7Bis a block diagram illustrating a perspective view of an embodiment of a stepper motor assembly utilizing a torque transferring coupler. In the example shown, stepper motor assembly with gear720comprises stepper motor722, drive shaft724, gear726, and nut728. In the example shown, stepper motor with gear assembly720is a perspective view of stepper motor with gear assembly700ofFIG.7A, wherein nut728has secured gear726to drive shaft724(i.e., using the TTC as shown inFIG.7A).

FIG.7Cis a block diagram illustrating a perspective view of an embodiment of a torque transferring coupler utilized as part of a stepper motor assembly. In the example shown, stepper motor assembly with gear740is a perspective view of stepper motor assembly with gear720ofFIG.7B, wherein TTC742is visible. In some embodiments, TTC742comprises drive shaft704with wave splines706and threaded region708, along with outer cylinder with wave splines712and nut714ofFIG.7A.

FIG.8is a flow diagram illustrating an embodiment of a method for providing a torque transferring coupler. In800, an inner cylinder is provided, wherein the inner cylinder has a radial face comprising a first set of curved structures. In802, an outer cylinder is provided, wherein the outer cylinder has an axial face comprising a second set of curved structures, wherein a coupling is formed in response to a section of the outer cylinder disposed to surround a portion of the inner cylinder and the first set of curved structures of the inner cylinder disposed to interlock with the second set of curved structures of the outer cylinder, and the process ends.

Although the foregoing embodiments have been described in some detail for purposes of clarity of understanding, the invention is not limited to the details provided. There are many alternative ways of implementing the invention. The disclosed embodiments are illustrative and not restrictive.