A gear device based motion converter for converting rotary motion to linear motion

Abstract

A planetary or harmonic gear device are used to implement a motion converter for converting rotary motion to linear motion, by providing a linearly displacing function comprises one or more stages of planetary or harmonic gear assemblies that are rotatably driven by an input member, a linearly displaceable linkage that converts rotary motion into linear motion, an actuator for the linkage that is kinematically connected to a last stage of the one or more stages, and a housing for the actuator and for mechanical components of the one or more stages having an opening at proximal and distal ends thereof, wherein all mechanical components of at least one of the one or more stages are annular to define a continuous central cavity from the distal opening to the at least one stage, wherein the linkage is retractable within and extendable from the central cavity to facilitate displacement of a stationary surface upon extension of the linkage and contact with the stationary surface.

Description

[0001] - 1 -

[0002] A GEAR DEVICE BASED MOTION CONVERTER FOR CONVERTING ROTARY MOTION TO LINEAR MOTION

[0003] Field of the Invention

[0004] The present invention relates to the field of motion transmission devices. More particularly, the invention is directed to a planetary gear device based motion converter for converting rotary motion to linear motion, including high-magnitude linear motion.

[0005] Background of the Invention

[0006] A planetary gear device comprising a plurality of spaced planet gears meshing with both a central sun gear and an outer ring gear provides equal load distribution by virtue of the multiple planet gears and also achieves a high torque transmitting capacity within a small space. Since power is transmitted radially without any lateral pressure on the gear teeth, a planetary gearbox is stable and reliable.

[0007] A harmonic gear device (also known as a strain wave gear) is a compact mechanical transmission that uses an elliptical wave generator to flex a cup-shaped "flexspline" into a circular spline, which is a rigid ring with internal teeth. This design allows for high gear ratios, zero backlash, high torque, and compact, lightweight construction, making it ideal for applications like robotics, aerospace, and medical devices where precision is critical.

[0008] Several mechanical applications, such as lifting and breaching devices require high-power linear motion. One of the existing solutions is based on hydraulic pistons, which can provide a required high-power linear motion. However, hydraulic systems are cumbersome, expensive and suffer from failures. In addition, hydraulic fluid is prone to polluting the surroundings during the event of a leak from one or more fluid pipes.

[0009] It is an object of the present invention to provide a planetary or harmonic gear device for converting rotary motion to linear motion to produce a desired linear force, such as a controlled linear force, a high-magnitude linear force converted from a high-torque rotary motion, or even a low-magnitude linear force. - 2 -

[0010] It is another object of the present invention to provide a planetary or harmonic gear device that converts rotary motion to a long-displacement linear force.

[0011] It is still another object of the present invention to provide a mechanical linear actuator for replacing hydraulic and pneumatic piston linear actuators.

[0012] It is yet another object of the present invention to provide a planetary or harmonic gear device that converts rotary motion to a long-displacement linear motion, which can be operated manually or by an electric motor.

[0013] It is an additional object of the present invention to provide an economical and easy to handle planetary or harmonic gear device that functions as a substitute for several devices, such as a jack, a hydraulic piston and a breaching device.

[0014] Other objects and advantages of the invention will become apparent as the description proceeds.

[0015] Summary of the Invention

[0016] A planetary or harmonic gear device are used to implement a motion converter for converting rotary motion to linear motion, by providing a linearly displacing function comprises one or more stages of planetary or harmonic gear assemblies that are rotatably driven by an input member, a linearly displaceable linkage that converts rotary motion into linear motion, an actuator for the linkage that is kinematically connected to a last stage of the one or more stages, and a housing for the actuator and for mechanical components of the one or more stages having an opening at proximal and distal ends thereof, wherein all mechanical components of at least one of the one or more stages are annular to define a continuous central cavity from the distal opening to the at least one stage, wherein the linkage is retractable within and extendable from the central cavity to facilitate displacement of a stationary surface upon extension of the linkage and contact with the stationary surface. - 3 -

[0017] The gear device may be a planetary gear device having one or more stages of gear planetary assemblies.

[0018] In one aspect, the input member is a tubular drive coupling connected to an annular input gear of a first stage planetary gear assembly, wherein the central cavity extends from the distal opening to a proximal end of the tubular drive coupling.

[0019] In one aspect, one of the annular mechanical components is a coupling section. The coupling section may be configured with a proximal uninterrupted circumferential wall and with a distal interrupted wall portion that is integral with the proximal wall from which two or more predefined shaped female regions are removed. The coupling section is adapted to mate with another coupling section that may be configured with a distal uninterrupted circumferential wall and with a proximal interrupted wall portion that is integral with the distal wall of the another coupling section and that is formed with two or more axially protruding predefined shaped male parts such that each male part of the coupling section is complementary to a female region of the coupling section.

[0020] In one aspect, the linkage is a leadscrew and the actuator is a nut actuator that is coaxial with the leadscrew and that has inner threading with which outer threading of the leadscrew cooperates to cause linear displacement of the leadscrew upon rotation of the nut actuator.

[0021] In one aspect, the inner threading of the nut actuator surrounds a central bore that is coincident with the central cavity and extends throughout the nut actuator from a proximal terminal peripheral element to a distal terminal peripheral element.

[0022] In one aspect, the nut actuator is configured with the another coupling section that is drivingly connected to the last planetary gear assembly stage.

[0023] In one aspect, the device further comprises an element for restraining rotational motion of the leadscrew. - 4 -

[0024] In one aspect, the leadscrew is configured with an axially extending groove and the rotational motion restraining element is introduced into the groove. The rotational motion restraining element may be connected to a non-rotating mounting element that is mounted onto the housing of the device.

[0025] In one aspect, the tubular drive coupling is directly connected to an input shaft.

[0026] In one aspect, the tubular drive coupling is gearingly connected to an input shaft.

[0027] In one aspect, the tubular drive coupling is drivingly connected to an annular sun gear of the first stage planetary gear assembly.

[0028] In one aspect, the tubular drive coupling is drivingly connected to a ring gear of the first stage planetary gear assembly.

[0029] In one aspect, the device further comprises a force applier connected to an output end of the linearly displaceable linkage and contactable with the stationary surface.

[0030] A planetary gear device providing a linearly displacing function, comprising a combination of one or more hollow planetary gear stages and a screw-like actuator kinematically connected to a last stage of the one or more stages, for allowing the screw-like actuator to linearly displace mechanical elements via a cavity portion formed in the hollow planetary gear stages.

[0031] The ring gear may be common to all stages.

[0032] The inner threading of the nut actuator may be a ball screw, a unified thread, a rectangular thread, a square thread, a trapezoidal thread, an Acme thread or a buttress thread.

[0033] The gear device may also be a harmonic gear device having one or more stages of gear harmonic assemblies. - 5 -

[0034] The input member is a tubular drive coupling connected to an annular input gear of a first stage harmonic gear assembly, wherein the central cavity extends from the distal opening to a proximal end of the tubular drive coupling.

[0035] The nut actuator may be configured with the another coupling section that is drivingly connected to the last harmonic gear assembly stage.

[0036] The tubular drive coupling is drivingly connected to an annular gear of the first stage of the harmonic gear assembly.

[0037] The tubular drive coupling is drivingly connected to a ring gear of the first stage harmonic gear assembly.

[0038] A harmonic gear device providing a linearly displacing function, comprising a combination of one or more hollow harmonic gear stages and a screw-like actuator kinematically connected to a last stage of the one or more stages, for allowing the screw-like actuator to linearly displace mechanical elements via a cavity portion formed in the hollow harmonic gear stages.

[0039] Brief Description of the Drawings

[0040] In the drawings:

[0041] - Fig. 1 is a plan view of a prior art planetary gear device;

[0042] - Fig. 2 is a perspective view of a planetary gear device according to an embodiment, shown when a linearly displaceable linkage is in a retracted position;

[0043] - Fig. 3 is a perspective view of the planetary gear device of Fig. 2, showing the linearly displaceable linkage in an extended position;

[0044] - Fig. 4 is a perspective sectional view of the longitudinally elongated housing of the planetary gear device of Fig. 2, shown without the mechanical components;

[0045] - Fig. 5 is a perspective exploded view of two planetary gear assemblies used in the planetary gear device of Fig. 2, showing an annular coupling section;

[0046] - Fig. 6 is a perspective sectional view of one of the planetary gear assemblies of Fig. 5; - 6 -

[0047] - Fig. 7 is an exploded view of the planetary gear assembly of Fig. 6;

[0048] - Fig. 8 is a perspective view of the planetary gear assembly of Fig. 6 when assembled and one the carrier members is removed;

[0049] - Fig. 9 is a perspective sectional view of the planetary gear device of Fig. 2, shown with the mechanical components;

[0050] - Fig. 10 is a perspective sectional view of the planetary gear device of Fig. 2, shown with the mechanical components with the exception of the tubular drive coupling;

[0051] - Fig. 11 is a perspective end view of a nut actuator used in the planetary gear device of Fig. 2;

[0052] - Fig. 12 is a perspective view of a linearly displaceable linkage used in the planetary gear device of Fig. 2;

[0053] - Fig. 13 is an exploded view of the planetary gear device of Fig. 2;

[0054] - Fig. 14 shows the basic construction of a harmonic gear device;

[0055] - Fig. 15 illustrates a harmonic gear device with an annular coupling section, according to an embodiment of the invention;

[0056] - Fig. 16 illustrates a cross-sectional view of the harmonic gear device with an annular coupling section, according to an embodiment of the invention;

[0057] - Fig. 17 illustrates a cross-sectional view of the harmonic gear device with an annular coupling section of Fig. 15, according to an embodiment of the invention;

[0058] - Figs. 18A-18B provide an exploded view of the harmonic gear device with an annular coupling section of Fig. 15, according to an embodiment of the invention; and

[0059] Figs. 19A-19B illustrate the integration of the harmonic gear device into the nut actuator of Fig. 11, according to an embodiment of the invention.

[0060] Detailed Description of the Invention

[0061] The motion converter of the present disclosure is based on planetary or harmonic gear devices that comprise a linkage that converts rotary motion into linear motion.

[0062] Example 1 - Planetary Gear Device - 7 -

[0063] The planetary gear device is a combination of a unique planetary gear and a screw gear, for convert rotary motion to linear motion, including long linear motion with high power and controlled power.

[0064] The high-magnitude linear force that is able to be derived from high-torque rotary motion, or alternatively the low-magnitude linear force that is able to be derived from low-torque rotary motion, may be utilized for door breaching and raising vehicles or other heavy objects without need of a complicated and expensive hydraulic system that is liable to malfunction and cause air or water contamination.

[0065] Fig. 1 illustrates a prior art planetary gear device 10. Planetary gear device 10 comprises central sun gear 2, outer ring gear 4, and a plurality of symmetrically spaced planet gears 6 intermeshing with both sun gear 2 and ring gear 4, all of which generally being parallel-axis spur gears but may be of other configurations as well. The planet gears 6 revolve around sun gear 2, transmitting the rotary motion of the sun gear to the ring gear. A carrier 8 on which the planet gears 6 are rotatably mounted is also caused to rotate. A planetary gear device is easily adaptable for use in various implementations by changing the gear ratio between different gears or the number of planet gears, while taking into account a desired output force or speed. One contributing factor to the compactness and stability of planetary gear device 10 is that the drive shaft that may be connected to sun gear 2 is coaxial with the output shaft connected to carrier 8.

[0066] A linearly displaceable linkage is not able to be readily incorporated into a prior art planetary gear device due to the presence of the disc of sun gear 2 for each of one or more stages that radially extends from its hub 1, to which the drive shaft may be connected, to the gear teeth and that would block the linear displacement of the linkage. A carrier structure axially coincident with hub 1 or with any other central structure of sun gear 2 would also restrict linear displacement of the linkage.

[0067] To accommodate the linearly displaceable linkage that is positioned in a central cavity, all mechanical components of the planetary gear device of an embodiment of the present - 8 - disclosure including the sun gear, carrier, coupling section and linkage actuator have an annular configuration. Even though the sun gear and carrier have increased flexibility as a result of their annular configuration, various means such as sliding bearings, thrust bearings, gears and cages may be used for increased strength and reduced housing vibration and gear dynamic loads.

[0068] An assembled planetary gear device 30 providing a linearly displacing function is illustrated in Fig. 2 according to one embodiment. Device 30 is configured with main housing 34 in which one or more planetary gear assemblies are positioned, tubular drive coupling 41 linearly protruding from an annular end plate 39 at the longitudinal end of main housing 34 which is adapted for connection with the first planetary gear assembly, secondary housing 53 in which the actuator of the linearly displaceable linkage is retained, and force applier 64 connected to the output end of the linearly displaceable linkage, for example used in conjunction with a mechanical door breaching tool as illustrated that is configured with a triangularly shaped claw 66 adapted for insertion into the gap between a door and door frame. The linearly displaceable linkage, which is retracted in this drawing, is received in the common central cavity provided in main housing 34, tubular drive coupling 41 and secondary housing 53, and has a length at least equal to the length the central cavity.

[0069] Tubular drive coupling 41 may be rotatably driven by means of an input drive shaft received within socket 52, for example one that is connected to an electric motor. Alternatively, the periphery of tubular drive coupling 41 is gearingly connected to an input shaft. If so desired, tubular drive coupling 41 may be configured with circumferentially spaced ridges so that the first planetary gear assembly will be able to be driven by manually rotating the tubular drive coupling.

[0070] One or two claws 66 may be integrally formed with, and distally spaced from, annular mounting element 68 for secured mounting at the distal end of secondary housing 53. The distal end of secondary housing 53 may be formed with inner threading 57 (Fig. 4), and mounting element 68 may be formed with a radially smaller threaded coupler 84 (Fig. 13) for - 9 - threaded engagement with secondary housing 53. Other mounting elements are also in the scope of the invention, also those configured without a claw.

[0071] Force applier 64 may be configured with a substantially straight distal surface 86 provided with a plurality of grip elements 87 and with a through hole 89 through which a fastener is introduced in order to be fastened in a threaded hole 91 formed in the distal end of the linearly displaceable linkage 69, as shown in Fig. 10. The distal output end 67 of linearly displaceable linkage 69 has a larger radial dimension than linearly displaceable linkage 69, and is surrounded by a protective cup 94 proximally extending from force applier 64.

[0072] Other configurations of a force applier and a breaching tool are also in the scope of the invention.

[0073] Fig. 3 illustrates device 30 when linearly displaceable linkage 69, for example the illustrated leadscrew, is set to an extended position whereby force applier 64 is positioned distally relative to claw 66.

[0074] The size of the central longitudinally extending cavity 61, as illustrated in Fig. 4, is defined by the radial dimension of the annular end plate 39 and of the annular wall 56 dividing main housing 34 from secondary housing 53, being sufficient to receive the linearly displaceable linkage therein. The radial dimension of cavity 61 is of course reduced by the presence of the components of the planetary gear device.

[0075] An annular coupling section 42 is illustrated in Fig. 5. The use of annular coupling section 42 ensures that the linearly displaceable linkage insertable within the central cavity will not be interfered with during operation of the device. Coupling section 42 may connect a first planetary gear assembly 35A to a second planetary gear assembly 35B, connect tubular drive coupling 41 to first planetary gear assembly 35A, or connect second planetary gear assembly 35B, or any other final stage number, to the actuator of the linearly displaceable linkage. - 10 -

[0076] Annular coupling section 42 is configured with a proximal uninterrupted circumferential wall 43 that defines a complete annular surface and with a distal interrupted wall portion 46 that is integral with proximal wall 43, from which two or more predefined shaped female regions

[0077] 47 are removed. Coupling section 42 is adapted to mate with an adjacent coupling section 44 that is configured with a distal uninterrupted circumferential wall 48 that defines a complete annular surface and with a proximal interrupted wall portion that is integral with distal wall

[0078] 48 and that is formed with two or more axially protruding predefined shaped male parts 45. Each male part 45 of coupling section 44 is complementary to a female region 47 of coupling section 42, being suitably dimensioned to facilitate a strong coupling and force transmitting action.

[0079] Planetary gear assembly 35A, which is illustrated in Fig. 6, comprises interconnected distal carrier member 28 and proximal carrier member 29, each being annular, on which the planet gears (not shown) are rotatably mounted. Distal carrier member 28 is integrally formed with coupling section 42. Ring gear 24 having inner gear teeth is positioned around carrier members 28 and 29, being slightly radially spaced from their periphery, for example by a clearance of 0.1 mm. Ring gear 24 may be fixed in place by small circumferentially spaced protrusions 23 that protrude radially outwardly from the ring gear periphery and that are received in corresponding recesses formed in the main housing. Sun gear 22 having outer gear teeth is formed with coupling section 44, and is positioned within a cavity internal to carrier members 28 and 29 while being intermeshed with the planet gears which in turn are intermeshed with ring gear 24. The inner periphery of sun gear 22 is aligned with, and of the same curvature as, the inner periphery of coupling section 42, although sun gear 22 and coupling section 42 are slightly axially spaced from one another.

[0080] An exploded view of planetary gear assembly 35A is shown in Fig. 7. Both carrier members 28 and 29 are configured with a plurality of axially extending, circumferentially extending and circumferentially spaced abutments 33, each of which is formed with a through hole 36 that also passes through an external carrier member surface 21. Each of carrier members 28 and 29 is configured with an axially extending tubular post 31 positioned between two adjacent abutments 33, for the purpose of rotatably supporting a planet gear 26. The posts - 11 -

[0081] 31 and abutments 33 provided with distal carrier member 28 have a male protruding element M, and the posts and abutments provided with proximal carrier member 29 have a female recessed element F. When a threaded screw 37, or any other suitable fastener, is inserted into a corresponding through hole 36 formed in carrier members 28 and 29 and is secured by a nut 38, the male protruding element of the posts and abutments becomes interlocked with the female recessed element as shown in Fig. 6 and carrier members 28 and 29 become securely coupled to each other. Also, slippage of a planet gear 26 from a post 31 is prevented.

[0082] Prior to securing carrier members 28 and 29 to each other, a planet gear 26 is mounted on each post 31 while being intermeshed with the fixed outer ring gear 24. Afterwards, sun gear 22 is positioned within a cavity that is radially inwards to the abutments 33 and axially spaced between the radially inward edge 18 of the exterior surface 21 of each of carrier members 28 and 29 in such a way that ensures that the sun gear will be intermeshed with each of the planet gears 26.

[0083] Although the teeth of each gear used in the planetary gear assembly are shown to be those of a spur gear, other gear tooth profiles such as a helical gear profile, a bevel gear profile and a herringbone gear profile are also suitable.

[0084] An assembled planetary gear assembly 35A is shown in Fig. 8 while the proximal carrier member is removed. Sun gear 22 is driven in the same rotational direction as the tubular drive coupling with which it is connected. The four planet gears 26, or any other desired number of planet gears, intermeshed with both the rotating sun gear 22 and the fixed ring gear 24, are caused to rotate in the opposite rotational direction about the corresponding interlocked post while simultaneously revolving around the sun gear and along the ring gear. The revolving planet gears 26 in turn rotationally drive the annular carrier provided with the abutments 33 in the same rotational direction as the sun gear, albeit at a slower speed in accordance with a predetermined gear ratio. - 12 -

[0085] It will be appreciated that a larger-diameter tubular drive coupling may be connected to ring gear 24 when the latter is free to rotate. Sun gear 22 may be fixed or also free to rotate, or alternatively the carrier is fixed or also free to rotate. This arrangement defines a different gear ratio, the gear ratio being determined by the number of teeth of the input gear, the driven gear, and each planet gear 26.

[0086] Figs. 9 and 10 illustrate a perspective sectional view of two-stage planetary gear device 30, including leadscrew 69 and the coaxial nut actuator 74 that actuates linear displacement of leadscrew 69. Leadscrew 69, which is configured with the illustrated trapezoidal thread form, but which is also capable of being configured with other types of thread forms such as square, triangular, sawtooth and knuckle thread forms, is capable of occupying the entire central cavity of device 30, as shown. Nut actuator 74, which is configured with an intermediate relatively small-diameter periphery 73, a proximal relatively large-diameter terminal peripheral element 76 that is integral with intermediate periphery 73, and a distal terminal peripheral element 78 that is integral with intermediate periphery 73 and of a smaller diameter than proximal terminal peripheral element 76 and greater than intermediate periphery 73, is connected to second planetary gear assembly 35B by an elongated coupling section 42', which is similarly configured as coupling section 42. Bearings 81, 82 and 83 mounted within the housing help reduce friction during rotation of drive coupling 41 and nut actuator 74, and also support a high axial load while maintaining the nut actuator in a fixed axial position.

[0087] Fig. 9 shows the coupling section 42 that connects drive coupling 41 to first planetary gear assembly 35A, and Fig. 10 shows the coupling section 42 that connects first planetary gear assembly 35A to second planetary gear assembly 35B.

[0088] As shown in Fig. 11, nut actuator 74 has inner threading 77 with which the outer threading of the leadscrew cooperates. Rotation of the nut actuator causes corresponding linear displacement of the leadscrew, whether proximally or distally. The inner threading 77 surrounds the central bore 72, and extends throughout nut actuator 74 from proximal terminal peripheral element 76 to distal terminal peripheral element 78. Proximal terminal - 13 - peripheral element 76 is configured with a plurality of circumferentially spaced recessed regions 79 that adjoin the threaded bore 72, to facilitate connection with male parts of a coupling section.

[0089] The long-length central cavity extending from distal face 109 of mounting element 83 (Fig. 13) to tubular drive coupling 41 (Fig. 2) within which leadscrew 69 is able to be retracted and from which it is able to be extended facilitates a corresponding long-length displacement that is able to be achieved. The long-length displacement is produced in response to high- torque rotary motion generated by the planetary gear assemblies and the nut actuator. The generated torque may be increased when a plurality of annular planetary gear stages that increasingly reduce the rotational speed of the driven gear are employed. The provision of additional stages, for example 3-5 stages, necessarily increases the length of the central cavity to enable use of a corresponding increased-length leadscrew that produces a long- length displacement.

[0090] One implementation of a planetary gear device providing a linearly displacing function is a car lift for raising a vehicle above a parking space of a high-rise building. A plurality of planetary gear devices may apply a vertical force to a platform supporting the vehicle and cause the vehicle to be raised to a suitable overlying position.

[0091] With reference to Fig. 12, leadscrew 69 is configured with an axially extending groove 102 that is slightly recessed from threading 104 to the exposed unthreaded periphery, in order to restrain rotational motion of the leadscrew. Groove 102 extends from the proximal end 108 of the leadscrew to enlarged distal end 67 in abutment with force applier 64.

[0092] As shown in the exploded view of planetary gear device 30 shown in Fig. 13, a tooth 108 connected to non-rotating mounting element 68 is adapted to be introduced into groove 102 to prevent rotation of leadscrew 69. Tooth 108 has a maximum width substantially equal to, and slightly less than the width of groove 102. While a rotational driving force is transmitted to nut actuator 74, leadscrew 69 that is rotationally engaged with the nut actuator is urged - 14 - to be linearly displaced with essentially no rotational motion by the cooperation between tooth 108 and groove 102.

[0093] A rectangular plate 113 integrally formed with tooth 108 is received in a similarly shaped recess 117 formed in the distal face 109 of mounting element 83. Plate 114 is provided with a mounting hole 116 through which fastener 111 is introduced in order to be engaged with threaded hole 119 formed within recess 117, causing the plate to become stationary similarly to the mounting plate and housing. One side of recess 117 is arcuate, coinciding with the circular edge 118 of the bore formed in mounting element 83 that is in communication with the central cavity of the housing. Tooth 108 protrudes beyond circular edge 118, and is therefore able to be introduced into groove 102.

[0094] In another embodiment, the leadscrew is configured without a groove, and the planetary gear device is provided without a protruding tooth. Nevertheless, the leadscrew is urged to be linearly displaced exclusively when force applier 64 (Fig. 10) is brought in contact with a stationary surface intended to be displaced, such as a door to be breached. Contact with the stationary surface prevents rotation of the leadscrew. Thus upon driven rotation of the nut actuator, the cooperating leadscrew is urged to be linearly displaced with sufficient force to cause corresponding displacement of the stationary surface.

[0095] In another embodiment, the input shaft is directly connected to the first planetary gear assembly which is not annular while the disc of its sun gear radially extends from its gear teeth. The planetary gear device has a common central cavity provided in the other mechanical components in the main housing and secondary housing, and the linearly displaceable linkage has a length at least equal to the length of this central cavity to produce a long-length displacement.

[0096] The ring gear may be common to all stages. Also, the inner threading of the nut actuator may be a ball screw, a unified thread, a rectangular thread, a square thread, a trapezoidal thread, an Acme thread or a buttress thread. - 15 -

[0097] Example 2 - Harmonic Gear Device

[0098] This example illustrates another embodiment where a harmonic gear device is used rather than a planetary gear device.

[0099] Fig. 14 shows the basic construction of a harmonic gear device 140. The harmonic gear device 140 comprises an elliptical wave generator 141 which is used an input that drives a flex spline 142, which is a flexible, cup-shaped component that is responsible for transmitting the motion generated by the wave generator to a circular spline 143, which is a rigid ring with internal teeth.

[0100] The flex spline 142 features external teeth that engage with the internal teeth of the circular spline 143 at specific points of contact. The elastic nature of the flex spline 142 allows it to deform in accordance with the wave generator 141, while the flex spline 142 rotates within the circular spline 143. Typically, there are extra two teeth in the circular spline 143 that remains stationary, such that each half rotation of the elliptical wave generator 141 rotates the flex spline 142 one tooth forward or backward, depending on the direction of rotation and is used as the output of the harmonic gear. The circular spline 143 is a rigid ring with internal teeth that mesh with the external teeth of the flex spline 142. As the flex spline 142 deforms, only a portion of its teeth engage with the teeth of the circular spline 143, ensuring precision and smooth operation. This design creates the high reduction ratios and torque capabilities characteristic of harmonic gear device 140 and enables smooth harmonic motion that eliminates backlash and reduces mechanical errors.

[0101] Fig. 15 illustrates a harmonic gear device with an annular coupling section 42, according to an embodiment of the invention. The annular coupling section 42 ensures that the linearly displaceable linkage 69 (of Fig. 3), insertable within the central cavity will not be interfered with during operation of the device. Annular coupling section 42 connects the tubular drive coupling 41 (shown in Fig. 10) to the harmonic gear device 140 and to the actuator of the linearly displaceable linkage 69 (shown in Fig. 10). - 16 -

[0102] Annular coupling section 42 is configured with a proximal uninterrupted circumferential wall 43 that defines a complete annular surface and with a distal interrupted wall portion 46 that is integral with proximal wall 43, from which two or more predefined shaped female regions 47 are removed. Coupling section 42 is adapted to mate with the nut actuator 74 via a plurality of circumferentially spaced recessed regions 79 that adjoin the threaded bore 72, to facilitate connection with male parts of coupling section 42 connected to the flex spline 142, which is the output of the harmonic gear device. Tubular drive coupling 41 (shown in Fig. 2) is terminated with mating male parts similar to male parts 45, which are engaged with the female regions 47 formed in the elliptical wave generator 141.

[0103] Fig. 16 illustrates a cross-sectional view of the harmonic gear device 140 with an annular coupling section 42, according to an embodiment of the invention. The elliptical wave generator 141 is used as an input that drives the flex spline 142 via bearing 160. The external teeth of flex spline 142 engage with the internal teeth of the circular spline 143 and the flex spline 142 rotates within the circular spline 143, to generate a relative movement between flex spline 142 and the stationary circular spline 143, which provides the reduction ratio. The male parts of tubular drive coupling 41 (shown in Fig. 2) are engaged with the female regions 47 formed in the elliptical wave generator 141.

[0104] Fig. 17 illustrates a cross-sectional view of the harmonic gear device with an annular coupling section 42 of Fig. 15, according to an embodiment of the invention. It can be seen that the bearing 160 consists of a plurality of adjacent tubular rods 161 deployed between the elliptical wave generator 141 and the flex spline 142.

[0105] Figs. 18A-18B provide an exploded view of the harmonic gear device with an annular coupling section 42 of Fig. 15, according to an embodiment of the invention. The exploded view shows the elliptical wave generator 141, the flex spline 142, bearing 160 and the annular coupling section 42, which is rigidly connected to the external teeth of the flex spline 142, which together, from the output. - 17 -

[0106] Figs. 19A-19B illustrate the integration of the harmonic gear device into the nut actuator of Fig. 11, according to an embodiment of the invention. The distal end of tubular drive coupling 41 is engaged to the female regions 47 formed in the elliptical wave generator 141 via its male parts. The annular coupling section 42 which is the output of harmonic gear device 140 is engaged to the female regions 47 of the nut actuator 74, which rotates and causes the distal output end 67 of linearly displaceable linkage 69 (shown in Fig. 3) to move outwardly (or inwardly, depending on the rotation direction) with linear movement with high force that is determined by the gear ratio. At standby position, the linearly displaceable linkage 69 is fully contained within the cavity formed in the gear and the tubular drive coupling 41, as shown in Fig. 19B.

[0107] According to another embodiment, several harmonic gear assemblies may be connected to each other (using several corresponding annular coupling sections), to obtain a final stage number (that provides a desired gear ratio), to the actuator of the linearly displaceable linkage.

[0108] While some embodiments of the invention have been described by way of illustration, it will be apparent that the invention can be carried out with many modifications, variations and adaptations, and with the use of numerous equivalents or alternative solutions that are within the scope of persons skilled in the art, without exceeding the scope of the claims.

Claims

- 18 -CLAIMS1. A gear device providing a linearly displacing function, comprising: a) one or more stages of gear assemblies that are rotatably driven by an input member; b) a linearly displaceable linkage that converts rotary motion into linear motion; c) an actuator for said linkage that is kinematically connected to a last stage of said one or more stages; and d) a housing for said actuator and for mechanical components of said one or more stages having an opening at proximal and distal ends thereof, wherein all mechanical components of at least one of said one or more stages are annular to define a continuous central cavity from the distal opening to said at least one stage, wherein said linkage is retractable within and extendable from said central cavity to facilitate displacement of a stationary surface upon extension of said linkage and contact with the stationary surface.

2. The device according to claim 1, wherein the gear device is a planetary gear device having one or more stages of gear planetary assemblies.

3. The device according to claim 2, wherein the input member is a tubular drive coupling connected to an annular input gear of a first stage planetary gear assembly, wherein the central cavity extends from the distal opening to a proximal end of the tubular drive coupling.

4. The device according to claim 2, wherein one of the annular mechanical components is a coupling section.

5. The device according to claim 4, wherein the coupling section is configured with a proximal uninterrupted circumferential wall and with a distal interrupted wall portion that is integral with the proximal wall from which two or more predefined shaped female regions are removed.- 19 -6. The device according to claim 5, wherein the coupling section is adapted to mate with another coupling section that is configured with a distal uninterrupted circumferential wall and with a proximal interrupted wall portion that is integral with the distal wall of the another coupling section and that is formed with two or more axially protruding predefined shaped male parts such that each male part of the coupling section is complementary to a female region of the coupling section.

7. The device according to claim 6, wherein the linkage is a leadscrew and the actuator is a nut actuator that is coaxial with the leadscrew and that has inner threading with which outer threading of the leadscrew cooperates to cause linear displacement of the leadscrew upon rotation of the nut actuator.

8. The device according to claim 7, wherein the inner threading of the nut actuator surrounds a central bore that is coincident with the central cavity and extends throughout the nut actuator from a proximal terminal peripheral element to a distal terminal peripheral element ball screw.

9. The device according to claim 7, wherein the nut actuator is configured with the another coupling section that is drivingly connected to the last planetary gear assembly stage.

10. The device according to claim 7, further comprising an element for restraining rotational motion of the leadscrew.

11. The device according to claim 10, wherein the leadscrew is configured with an axially extending groove and the rotational motion restraining element is introduced into the groove.- 20 -12. The device according to claim 11, wherein the rotational motion restraining element is connected to a non-rotating mounting element that is mounted onto the housing of the device.

13. The device according to claim 3, wherein the tubular drive coupling is directly connected to an input shaft.

14. The device according to claim 3, wherein the tubular drive coupling is gearingly connected to an input shaft.

15. The device according to claim 3, wherein the tubular drive coupling is drivingly connected to an annular sun gear of the first stage of the planetary gear assembly.

16. The device according to claim 3, wherein the tubular drive coupling is drivingly connected to a ring gear of the first stage planetary gear assembly.

17. The device according to claim 2, further comprising a force applier connected to an output end of the linearly displaceable linkage and contactable with the stationary surface.

18. A planetary gear device providing a linearly displacing function, comprising a combination of one or more hollow planetary gear stages and a screw-like actuator kinematically connected to a last stage of said one or more stages, for allowing said screwlike actuator to linearly displace mechanical elements via a cavity portion formed in said hollow planetary gear stages.

19. The device according to claim 16, wherein the ring gear is common to all stages.

20. The device according to claim 8, wherein the inner threading of the nut actuator is selected from the group of: ball screw- 21 - unified thread rectangular thread square thread trapezoidal threadAcme thread buttress thread.

21. The device according to claim 1, wherein the gear device is a harmonic gear device having one or more stages of gear harmonic assemblies.

22. The device according to claim 21, wherein the input member is a tubular drive coupling connected to an annular input gear of a first stage harmonic gear assembly, wherein the central cavity extends from the distal opening to a proximal end of the tubular drive coupling.

23. The device according to claim 21, wherein one of the annular mechanical components is a coupling section.

24. The device according to claim 23, wherein the coupling section is configured with a proximal uninterrupted circumferential wall and with a distal interrupted wall portion that is integral with the proximal wall from which two or more predefined shaped female regions are removed.

25. The device according to claim 24, wherein the coupling section is adapted to mate with another coupling section that is configured with a distal uninterrupted circumferential wall and with a proximal interrupted wall portion that is integral with the distal wall of the another coupling section and that is formed with two or more axially protruding predefined shaped male parts such that each male part of the coupling section is complementary to a female region of the coupling section.- 22 -26. The device according to claim 25, wherein the linkage is a leadscrew and the actuator is a nut actuator that is coaxial with the leadscrew and that has inner threading with which outer threading of the leadscrew cooperates to cause linear displacement of the leadscrew upon rotation of the nut actuator.

27. The device according to claim 26, wherein the inner threading of the nut actuator surrounds a central bore that is coincident with the central cavity and extends throughout the nut actuator from a proximal terminal peripheral element to a distal terminal peripheral element ball screw.

28. The device according to claim 26, wherein the nut actuator is configured with the another coupling section that is drivingly connected to the last harmonic gear assembly stage.

29. The device according to claim 26, further comprising an element for restraining rotational motion of the leadscrew.

30. The device according to claim 29, wherein the leadscrew is configured with an axially extending groove and the rotational motion restraining element is introduced into the groove.

31. The device according to claim 30, wherein the rotational motion restraining element is connected to a non-rotating mounting element that is mounted onto the housing of the device.

32. The device according to claim 22, wherein the tubular drive coupling is directly connected to an input shaft.

33. The device according to claim 22, wherein the tubular drive coupling is gearingly connected to an input shaft.- 23 -34. The device according to claim 22, wherein the tubular drive coupling is drivingly connected to an annular gear of the first stage of the harmonic gear assembly.

35. The device according to claim 22, wherein the tubular drive coupling is drivingly connected to a ring gear of the first stage harmonic gear assembly.

36. The device according to claim 21, further comprising a force applier connected to an output end of the linearly displaceable linkage and contactable with the stationary surface.

37. A harmonic gear device providing a linearly displacing function, comprising a combination of one or more hollow harmonic gear stages and a screw-like actuator kinematically connected to a last stage of said one or more stages, for allowing said screwlike actuator to linearly displace mechanical elements via a cavity portion formed in said hollow harmonic gear stages.

38. The device according to claim 37, wherein the inner threading of the nut actuator is selected from the group of: ball screw unified thread rectangular thread square thread trapezoidal threadAcme thread buttress thread.

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