INTEGRATED MOTOR LINEAR ACTUATOR.
Patent Information
- Authority / Receiving Office
- MX · MX
- Patent Type
- Patents
- Current Assignee / Owner
- TOLOMATIC INC
- Filing Date
- 2022-11-18
- Publication Date
- 2026-05-19
Smart Images
Figure MX433753B0
Abstract
Description
This application claims priority to U.S. Patent Application No. 16 / 878,897, filed on May 20, 2020, entitled INTEGRATED MOTOR LINEAR ACTUATOR, which is incorporated herein by reference, in its entirety and for all purposes. FIELD OF INVENTION This application pertains to linear drive technology, including but not limited to linear drive systems for robotic welding, automated machine tool systems, and other programmable tool applications. More generally, the description refers to integrated motor linear drive systems with advanced designs tailored to improve power-to-weight ratio, envelope size, stroke length, and thermal performance. BACKGROUND OF THE INVENTION This description refers to linear actuators for use in automated machine tool systems, including robotic welding and other programmable tool applications. More generally, the description refers to the thrust bearing elements of a linear actuator system, including the thrust tube and thrust rod components. Industrial robots utilize a wide variety of actuator technologies to automate manufacturing processes, including robotic welding, injection molding, fixture clamping, packaging, assembly, surface coating, and product inspection and testing. They are also used in other high-volume, high-precision production manufacturing applications, particularly where speed, accuracy, durability, tool life, and operating costs are critical engineering factors. In robotic welding and automated or programmable machine tool applications, actuators can be arranged to position a welding gun or similar apparatus relative to a workpiece, using a linear actuator to position the electrode or end effector. Suitable applications include, but are not limited to, short-stroke clamping operations for arc, spot, or resistance welding, projection welding, and MA / t / ZUZÓ / UΊ ÓZOO friction and stir welding. Linear drives are also used in a range of other programmable tool applications, including robotic, pedestal, and accessory-type manufacturing operations. Speed, accuracy, and actuator life remain important design factors across these diverse applications, along with system size and weight considerations. As a result, there is a continuing need for improved linear actuator designs that can provide greater positioning accuracy with reduced tool deflection and travel, within a desired tool size and weight envelope, and at a reasonable cost. BRIEF DESCRIPTION OF THE INVENTION A linear actuator system is described. The system includes an actuator housing that encloses a motor and a screw shaft, each extending along a common longitudinal axis. A nut assembly engages with the screw shaft and is coupled to the push tube. The push tube extends from a proximal end, which engages with the nut assembly and is disposed at least partially within the actuator housing, to a distal end, which is disposed at least partially outside the housing. The push tube can be directly coupled to the nut assembly at the proximal end. In several examples and configurations, the linear actuator system includes an actuator housing that extends along the longitudinal axis. A motor assembly, including a stator, is coupled to the actuator housing, with a rotor extending along the shaft within the housing. A screw shaft extends within the rotor, along the common longitudinal axis. A nut assembly is coupled to the screw shaft and to a thrust tube that extends from a proximal end, which can be directly coupled to the nut assembly, to a distal end disposed at least partially outside the housing. The nut assembly is configured to convert the rotational motion of the rotor around the longitudinal axis into linear motion of the thrust tube along the longitudinal axis. The method's modalities include operating a motor that has a stator and rotor arranged around the screw shaft. The rotor rotates around a longitudinal axis, along with the screw shaft, driving a thrust tube along the longitudinal axis. The thrust tube can be directly coupled to a nut assembly in a threaded connection with the screw shaft. The thrust tube extends from a proximal end in direct physical coupling with the nut assembly to a load-bearing distal end. Depending on the modality, the method may also include providing rotational stability while loading the thrust tube; for example, the ML / E / ZuZo / uZoo thrust tube can be supported with a bushing or bearing placed near the distal end. The apparatus configurations include a stator coupled to an actuator housing. A rotor is disposed within the actuator housing, adjacent to the stator, and the screw shaft is disposed within the rotor, extending along a shaft of the actuator housing. A nut assembly is engaged around a threaded portion of the screw shaft and coupled with a thrust tube that extends continuously along the shaft from a proximal end to a distal end. A mechanical fit defines a direct physical coupling between the proximal end of the thrust tube and the nut assembly; for example, in the absence of any additional load-bearing components intervening between the nut assembly and the proximal end of the thrust tube. In addition to the representative examples and modalities described herein, other modalities are also covered, as described with reference to the drawings, and by the study of the following description. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a front symmetrical view of a linear actuator system. Figure 2 is a cross-sectional view of the linear actuator system. Figure 3 is a cross-sectional view of a nut and push tube assembly for a linear actuator system. Figure 4 is an exploded view of the thrust tube and a front end bearing assembly for a linear actuator system. Figure 5 is an exploded view of a linear actuator system, including a motor assembly and a screw shaft. Figure 6 is a cross-sectional view of the screw shaft, showing the roller screw and portions of the adapter. Figure 7 is an exploded view of a rear-end bearing block assembly for a linear actuator system. Figure 8 is a top view of the linear actuator system, showing a cooling assembly for the actuator housing. Figure 9 is a front view of the linear actuator system, showing an anti-rotation feature for the push tube. Figure 10 is a rear view of the linear actuator system, showing the connectors for control and power communications. Figure 11 is a flowchart that illustrates a method for operating a system ΜΛ / Ε / ΖυΖο / υΊ ÓZOO of the linear actuator. DETAILED DESCRIPTION OF THE INVENTION Linear drive systems are available in a variety of sizes and configurations, depending on application, service, and operational requirements. Integrated motor drive systems offer an efficient and compact design, with the central housing section also serving as the stator housing. For example, a stator coil assembly can be mounted inside the central housing section, with a rotor and screw shaft extending inside the stator along the central axis. A nut assembly couples the rotor and screw shaft to a push tube or output rod, which moves longitudinally along the axis in response to the rotor's rotation. Integrated motor drives can be produced at a relatively low cost with improved electromechanical efficiency and manufacturing advantages. Additional design benefits include high speed and positioning accuracy, a reduced envelope size, and an improved power-to-weight ratio. Weight can be an important design consideration in applications where the actuator device is typically carried by a robot, along with the associated welding gun equipment or other mechanical tool components. A lighter system also reduces the load on the robot arm, increasing speed and enabling smaller robot systems with more precise positioning capabilities and higher throughput. The body portion of the actuator housing can be held together between the end caps, for example, using reinforcing bars or similar mechanical fasteners. This design can also reduce weight compared to thicker-walled configurations and improve the system's ability to cool the motor drive, which is also a consideration in applications requiring the device to operate at high repetition rates (e.g., more welds per minute) or with greater travel distances. Higher rates and greater travel distances both mean additional mechanical work output; that is, the motor drive needs to work harder, and the system thus generates more heat. To address these concerns, the actuator configurations described herein are adapted to accommodate a cooling assembly, such as an active water-cooled system or a passive cooling structure. Adding a cooling assembly can improve motor capacity, for example, by two times or more, while maintaining acceptable system temperatures. In some embodiments, the cooling assembly can be formed within the actuator housing or otherwise permanently installed at the point of manufacture. In other embodiments, a modular cooling assembly can be adapted to be selectively coupled (and decoupled) along one or more different sides or longitudinal sections of the actuator housing. Typical electric motor drives include an internal rotor, mounted with swivel bearings at each end. The bearings are sized to support the length of the rotor component as it rotates around the longitudinal axis of the drive, with precise clearance between the rotor and stator along the rotor's length. In some configurations, the rotor may be supported by a single swivel bearing assembly at one end; for example, at the proximal end, or between the proximal and distal ends. The rotor may also be provided in a short, standard, or elongated configuration, with additional design features to reduce the mass and moment of inertia of both the rotor and other motor drive components. Reference will now be made to the accompanying drawings, which help illustrate the various features of this description. The following description is presented for illustrative and descriptive purposes. Furthermore, the description does not intend to limit the inventive aspects to the forms described herein. Consequently, variations and modifications in accordance with the relevant knowledge, skills, and technical expertise are within the scope of the inventive aspects herein. Figure 1 represents a linear actuator system 100, exemplary of the linear actuator systems discussed above and as described in detail below. The linear actuator system 100 is used to drive an output rod or push tube 104 in reciprocating motion along a longitudinal axis A. In the configuration of Figure 1, the push tube 104 is positioned at least partially within the main body or central portion of the actuator housing 108. The push tube 104 extends along the longitudinal axis A from a first (proximal) end oriented toward the proximal end region 105a of the linear actuator system 100, within the housing 108, to a second (distal) end 104b toward the distal end region 105b of the linear actuator system 100, outside the housing 108. In this particular example, the distal or outlet end 104b of the push tube 104 is positioned at the axial end of the distal region 105b. The distal end 104b of the push tube 104 can be attached to a machine tool, workpiece, end effector, or other component. A motor assembly is positioned within the drive housing 108 and configured to drive the push tube 104 in a reciprocating motion along the longitudinal axis A. The push tube 104 typically moves between a first (retracted) position and a second (extended) position, in which the distal end 104b of the push tube 104 advances at least partially out of the drive housing 108 and past the head assembly 112. This reciprocating motion between the first retracted position and the second extended position can be used to drive a machine tool in a corresponding manner along the longitudinal axis A. As used herein, the terms proximal and distal are defined with respect to the internal components of the linear actuator system 100, and any workpiece or tool attachment located at the output end 104b of the thrust tube 104, outside the actuator housing 108. In particular, the term distal refers to the direction of the output end 104b of the thrust tube 104 that is at least partially outside the housing 108 (and any workpiece or tool attachment connected thereto), and the term proximal refers to the direction away from the output end 104b of the thrust tube 104 (and any workpiece or tool attachment connected thereto). Alternatively, the terms may be interchanged without loss of generality, depending on the design or drawing convention. The actuator housing 108 shown in Figure 1 generally encloses a portion of the push tube 104. The actuator housing 108 further encloses a motor assembly and any other appropriate components used to drive the reciprocating motion of the push tube 104. Exemplary internal components are described in greater detail with reference to Figure 2, including a motor assembly (e.g., magnets, windings, and rotors), bushings, bearings, and a nut assembly coupled to a lead screw or screw shaft to convert the rotational motion of the rotor into reciprocating motion of the push tube 104 along the central axis A. The main or central portion of the actuator housing 108 can be formed by extrusion or machining into a generally hollow shape configured to enclose the motor assembly and other internal components, or as a multi-part assembly. More generally, the actuator housing can encompass the central or main housing section 108 together with a head assembly 112, bearing block 114, and rear cover 116, joined together along the central axis A. As shown in Figure 1, for example, the head assembly 112 is coupled to the distal end of the main housing 108 along the longitudinal axis A, in the distal region 105b of the actuator system, and the main bearing block 114 and rear cover 116 are coupled to the central portion of the housing 108 in the proximal region 105a. As described herein, the linear actuator system 100 converts rotary motion (e.g., of an internal screw) into reciprocating motion of the push tube 104. The main bearing block 114 may enclose various components adapted for precision control of the reciprocating motion, such as a rotary encoder that detects a rotational position of the internal screw and other control or logic components that utilize the position ML / E / ZuZo / uO ÓZOO detected to determine a reciprocal position of the push tube 104. The bearing block connectors 117 can be used to detachably attach the main bearing block 114 to the actuator housing 108. In this configuration, the main bearing block 114 can be interchanged, allowing the linear actuator to be used with a variety of different encoders, sensors, feedback mechanisms, etc., as appropriate for a given application. As described herein, an adapter is provided for connecting the screw shaft and other internal actuator components to be associated with different bearing blocks, including those having different sizes or configurations than the main bearing block 114 shown with respect to Figure 1. External connectors 115a and 115b are mounted on or above the main bearing block 114. These connectors are used to connect the linear drive system 100 to various external systems and processes. For example, connectors 115a and 115b can be used to electrically connect the linear drive system 100 to a power supply. Alternatively, connectors 115a and 115b can be used to provide a data connection between the linear drive system 100 and an external computing device, which can be adapted to control one or more operations of the linear drive system 100. Connectors 115a and 115b are for illustrative purposes only. These connectors can be used to provide connections or links between the Linear Drive 100 system and external power supplies, computing devices, and other peripheral systems. For example, a remote computing device can be wirelessly coupled to one or more internal components of the Linear Drive 100 system. Control signals and data outputs can then be exchanged between the remote computing device and the Linear Drive 100 system wirelessly, according to various protocols. The main bearing block 114 is shown connected to a back cover 116. The back cover 116 may be a plate or other closure that operates to close and seal the interior of the main bearing block 114 from the external environment. The back cover 116 may also provide access for servicing or replacing various components housed within the main bearing block 114. For example, the main bearing block 114 may contain various sensors and other electronic components that can be protected by the back cover 116. As shown in Figure 1, back cover connectors 119, such as bolts, screws, or other mechanical fasteners, may be used to secure the back cover 116 to the main bearing block 114.The rear cover connectors 119 can be manipulated in order to remove the rear cover 116 from the main bearing block 114 and allow maintenance of the components contained therein. A front head assembly 112 is detachably attached to the actuator housing 108 in the distal end region 105b, for example, using screws, bolts, or similar front head connectors 113. As described herein, the front head assembly 112 houses an adjustable guide bushing that can provide stability to the thrust tube 104 as the thrust tube 104 moves in a reciprocating motion along the longitudinal axis A. The front head assembly 112, in cooperation with the adjustable guide bushing 130, can also provide rotational stability to the thrust tube 104. As an example, the thrust tube 104 can define a plane 106 or other surface contour.The front head assembly 112 may include one or more features, including the adjustable guide bushing, with a correspondingly contoured feature that is key to plane 106, thereby helping the thrust tube 104 to maintain rotational stability as the thrust tube 104 moves along longitudinal axis A. The linear actuator system 100 described herein also includes various cooling features, systems, and assemblies that help reduce the temperature of the motor assembly contained within the actuator housing 108. In the example in Figure 1, the linear actuator system 100 is shown including a cooling loop 120. The cooling loop 120 may be at least partially embedded, encapsulated, or seated with a thermally conductive material 123 within a channel or recessed feature 110 defined in the actuator housing 108. The cooling loop 120 may be formed with the thermally conductive material 123 arranged at least partially around the cooling loop 120 to conduct heat away from the actuator housing 108. The cooling loop 120 may include a hollow internal duct or tube through which the cooling fluid is routed.A first fluid coupling 122a and a second fluid coupling 122b can be used to couple the cooling loop 120 to a fluid source for circulating the cooling fluid. In some cases, the fluid couplings 122a and 122b may include inlet and outlet couplings, valves, or quick-disconnect features adapted for removable connection of the cooling loop 120 to a conduit, hose, or other fluid flow component configured to circulate the fluid through the cooling loop 120. The recessed feature 110 is shown formed on a first side 109a of the actuator housing 108. The cooling loop 120 is therefore at least partially embedded, encapsulated, or seated on the first side 109a of the actuator housing 108. The cooling loop 120 in the example of Figure 1 conducts heat substantially from the first side 109a. A second side 109b, or another side of the actuator housing 108, remains substantially decoupled from the cooling loop 120. However, it will be appreciated that, in other cases, multiple cooling loops may be provided, with corresponding recessed features formed on each respective side, or all sides, of the actuator housing 108 as required.Furthermore, in other cases, the second side 109b or another side of the actuator housing 108 can be adapted to receive another cooling component, such as a modular cooling jacket or another cooling jacket that attaches to a side of the actuator housing 108 that is not otherwise associated with the cooling loop 120 shown in Figure 1. In this configuration, the linear actuator system 100 can be adjusted to provide the level of cooling as required for a particular application. Figure 2 is a cross-sectional view of the actuator system 100. In this particular configuration, the linear actuator system 100 includes a motor assembly 140 arranged within the central portion of the actuator housing 108. A head assembly 112 is coupled to the central housing 108 in the distal end region 105b, for example, using one or more front head connectors 113, or similar mechanical fittings. A bearing block 114 and rear cover 116 are connected to the central housing 108 at the proximal end 105a, opposite the head assembly 12, for example, using one or more bearing block connectors 117 and rear cover connectors 119. The motor assembly 140 is located within the central housing 108. The motor assembly 140 typically includes a stator with a number of motor windings 142, magnets 144 (for example, permanent magnets or electromagnets), and a rotor 146. For example, the motor assembly 140 can be configured as a hollow-shaft motor having one or more stationary motor windings (stator) 142, with a centrally located hollow rotor 146 positioned radially inward of the stator windings 142, within the drive housing 108. Conversely, the windings 142 are positioned radially outward of the rotor 146, for example, fixed to (or fixed relative to) the drive housing 108. When the motor assembly 140 is provided in hollow shaft or hollow rotor form, as shown in Figure 2, the rotor 146 may have generally cylindrical outer and inner surfaces, with the stator windings 142 and rotor 146 surrounding a centrally located linear thrust mechanism that includes a threaded lead screw or screw shaft 150, with nut (or nut assembly) 160 coupled directly to the thrust tube, output rod, or other load transfer structure. The thrust mechanism is configured to convert the rotational motion of the rotor 146 into linear motion of the thrust tube 104. As shown in Figure 2, for example, the thrust mechanism includes the elongated, externally threaded lead screw or screw shaft 150 in combination with an internally threaded nut assembly 160, positioned radially inward from and substantially surrounded by the rotor 146. In this configuration, the screw shaft 150 may include an externally threaded section, provided with threads along a ML / E / ZuZo / uO ÓZOO substantial portion of the shaft length. As used herein, the terms thread and threading may thus be used to define the main threaded section of the screw shaft 150, including, but not limited to, conventional threads, Acme- or ACME-type threads, roller screw threads, ball nut threads, and other threaded features suitable for converting the rotary motion of the rotor 146 into linear motion of the push tube 104. Depending on the design, the lead screw or screw shaft 150 may also include a proximal extension 152. The proximal extension 152 may be formed as a reduced-diameter, unthreaded section at the proximal end of the screw shaft 150. The proximal extension 152 extends through the hub 148 and may be rotatably coupled to it, for example, by providing the inner surface of the hub 148 with a complementary tapered shape, or with a lock-and-key arrangement. The thrust bearing 170 can be positioned radially outward from the hub 148 and configured to support the hub 148 and the proximal extension 152 of the screw shaft 150 within the actuator housing 108. In some examples, the thrust bearing 170 may include a pair of bearings that are matched to provide a higher force capacity. Accordingly, although Figure 2 shows the thrust bearing 170 as a single bearing, two or more bearings may be provided at or adjacent to the proximal end to support the screw shaft 150 within the housing 108. Depending on the design, the rotor 146 and hub 148 may be provided as a single, integrated component or as separate parts.The proximal end of the rotor 146 can also be rigidly connected to the axial extension (rotor mounting portion) of the hub 148, so that rotation of the rotor 146 causes a corresponding rotation of the hub 148 and lead screw (or screw shaft) 150. A feedback device or block 176, for example, including an optional braking assembly, can also be positioned adjacent to the proximal extension 152 of the screw shaft 150, with a mounting plate 179 facilitating attachment within the main bearing block 114. A rotary encoder 178 or other position sensor / controller can be mounted to the proximal extension 152 of the screw shaft 150, using an adapter 172. For example, a hollow shaft encoder (incremental or absolute) 178 can be coupled to the adapter 172 using a threaded connection or other mechanical means, with the rotation sensor element mounted directly on the adapter 172. In turn, the adapter 172 can also be coupled to the screw shaft 150 in a manner that causes the adapter 172 to rotate with the rotation of the screw shaft 150.Therefore, while adapter 172 is shown in Figure 2 for use with a hollow-hole feedback device, other configurations are possible and are addressed herein. For example, feedback devices that do not require a hollow-hole connection can be implemented, including those where a direct coupling of the device or adapter 172 and / or screw shaft 150 is used (e.g., an Oldham coupler, a threaded coupling, or other mechanical coupling). In the example in Figure 2, the screw shaft 150 includes a mating feature or fit 154 at its proximal end. Although many configurations are possible, the mating feature 154 defines a proximal fit 155 or socket that is adapted to receive the adapter 172. The adapter 172 may define an adapter fit 173, which is a reduced-diameter portion of the adapter 172. The adapter fit 173 can be inserted into the proximal fit 155 of the screw shaft 150. In some cases, the adapter fit 173 and the proximal fit 155 may define a press fit, interference fit, or threaded coupling. A lock nut 175 may also be provided to restrict rotational and axial movement of the adapter 172 and the screw shaft 150 relative to each other. A load distribution washer 171 is shown in Figure 2 with the proximal extension 152 and the coupling feature 154 extending through it. The load distribution washer 171 can further improve the stability of the screw shaft 150 during operation. The load distribution washer 171 can be pressed between the lock nut 175 and the thrust bearing 170 / hub 148 along the longitudinal axis A, thereby providing a more evenly distributed load along the longitudinal axis AA for components configured for rotational movement about it. The distal end of the push tube 104 can be adapted for association with an adjustable guide bushing 130 that supports and stabilizes the distal end of the push tube 104 relative to the actuator housing 108. For example, the adjustable guide bushing 130 can generally be positioned at the distal end 105b of the system 100. At the distal end 105b, the adjustable guide bushing 130 can be configured to provide axial or rotational stability to the push tube 104 as the push tube 104 oscillates along the longitudinal axis A between a retracted and an extended state, as explained in detail with reference to Figure 4. This may involve adapting one or more contours of the adjustable guide bushing 130 to a corresponding contour of the push tube 104 (for example, plane 106 in Figure 1). In some embodiments, the distal end of the rotor 146 may be provided with a projection, recessed portion, or other feature to accommodate a secondary bearing 158 configured to support and stabilize the distal end of the rotor 146 relative to the drive housing 108. As a possibility, a secondary bearing 158 may be provided, which may be adapted to float or travel in an axial direction (parallel to the axis of rotation A of the rotor 146 and the lead screw 150), in order to accommodate the thermal expansion of the rotor 146 and other components. ML / E / ZuZo / u Ozoo The central portion of the rotor 146 can be provided with a number of mandrels 144, mounted either along the outer surface of the rotor 146 or embedded within the outer surface of the rotor 146, adjacent to the stator windings or coils 142. For example, the rotor 146 can be machined to form channels or slots extending axially along the central portion of the rotor 146, and the mandrels 144 can be embedded within the slots, between the corresponding (and radially thicker) axial rib sections. This can also provide a rotor 146 with thicker-walled sections at the proximal and distal ends, extending axially on either side of the mandrels 144. A channel and axial rib structure reduces the mass and inertial motion of the rotor 146, so less torque is required for angular acceleration and deceleration. The outer (proximal and distal) ends of the rotor 146 can also be provided with a plurality of slots, holes, or openings extending through the wall sections to further reduce inertia and torque requirements. The rotor 146 also allows for simple assembly of the motor 140, without additional tooling for alignment, while providing sufficient material to reduce or limit core saturation due to the high flux density of the magnets 144, and reduces stray flux and flux leakage. When the motor assembly 140 is operated, the rotor 146 rotates in a first (e.g., clockwise) or second (e.g., counterclockwise) direction about the longitudinal axis A. The proximal end of the rotor 146 is connected to a screw shaft 150 (e.g., by means of a hub 148), so that the rotation of the rotor 146 results in a corresponding rotation of the screw shaft 150, in either the first or second direction. The nut assembly 160 may include internal threads, for example, a recirculating ball screw or roller nut 162 that engages with external threads on the outer surface of the screw shaft 150 to convert the rotary motion of the rotor 146 into a linear (axial) motion of the nut assembly 160. The nut assembly 160 and the push tube 104 are directly coupled to each other and therefore move in unison along the longitudinal axis A when the screw shaft 150 rotates through the rotor 146 of the motor assembly 140. The nut assembly 160 and the push tube 104 can be directly coupled to each other, without the need for additional intermediate bearing or housing structures, giving the linear actuator system 100 a more compact design. Furthermore, without the additional bearing or housing structures, the screw shaft 150 can be oversized, or generally larger, than conventional designs relative to the dimensions of the actuator housing 108. In this way, the actuator system 100 can provide improved torque relative to its system size, while utilizing the cooling systems described herein to remove heat and maintain a suitable system temperature. ML / E / ZuZo / u Ozoo 100. In the example in Figure 2, the nut assembly 160 includes a first end 161a adjacent to the hub 148 and a second end 161b adjacent to the thrust tube 104. The second end 161b rests directly on the thrust tube 104, for example, in a mechanical coupling or fit 167. A complementary fit 168 is defined on the second end 161b of the nut assembly 160, for example, a threaded coupling, press fit, or interference fit adapted for mating with the fit 167 on the proximal end 104a of the thrust tube 104. In this configuration, the thrust tube 104 can be mated directly to the roller nut 162 or the nut assembly 160, in the absence of additional housing or load-bearing structures between the mechanical coupling 168 on the second end 161b of the nut assembly 160 and the complementary fit. 167 in the proximal and 104 push tube. As shown in Figure 2, the roller nut 162 is held within the nut assembly 160 by a carrier 166 that extends between the first and second ends 161a, 161b. In the example in Figure 2, the carrier 166 defines the mechanical coupling 168 at the second end 161b of the nut assembly 160. End caps 164a, 164b may be provided at the respective first and second ends 161a, 161b for structural support and to mitigate debris entry into the roller nut 162. In some cases, the end caps 164a, 164b may define the mechanical coupling 168, either alone or in conjunction with the carrier 166. For example, the nut assembly 160 and push tube 104 can move in a distal direction in response to a first rotation (clockwise) of the rotor 146 and the lead screw or screw shaft 150, with the outlet end of the push tube 104 moving away from the actuator housing 108 along axis A of the linear actuator system 100. Conversely, when the motor assembly 140 drives the rotor 146 and screw shaft 150 in the opposite direction (counterclockwise), the nut assembly 160 and push tube 104 move in a proximal direction along longitudinal axis A, retracting the push tube 104 into the actuator housing 108. For example, the push tube 104 can be retracted into an internal volume 127 of the actuator housing. 108.A stop 128 can be provided between the push tube 104 and the screw shaft 150 or another system component 100. The stop 128 defines a deformable interface region between the inner surface of the push tube 104 at the working or output (distal) end and the adjacent end of the screw shaft 150, cushioning the impact and reducing the contact forces at the innermost position of the push tube 104. Alternatively, the threading configuration can be different, and the proximal and distal movements of the push tube 104 can be reversed with respect to the rotation of the screw shaft 150. In this way, the motor assembly 140 is controllable to provide any desired linear or axial movement of the push tube 104, and any workpiece or tool connected to it, based on the rotational movement of the rotor 146 and the screw shaft 150. Figure 3 is a cross-sectional view of the nut 160 and push tube 104 assembly directly coupled together. The nut 160 assembly is shown directly coupled to a proximal end of the push tube 104. For example, the nut 160 assembly can be continuously extended from the first end 161a to the second end 161b, with the second end 161b abutting the push tube 104. The nut 160 and push tube 104 assembly can thus be directly coupled together, in the absence of an additional bearing structure or housing intervening between the nut assembly and the proximal end of the push tube. As shown in Figure 3, the mechanical coupling 168 may include a threaded coupling, press fit, or interference fit at the second end 161b of the nut assembly 160. The mechanical coupling 168 may be adapted to engage a complementary fit or coupling 167 at the proximal end 104a of the push tube 104, opposite the distal end 104b, within a common outside diameter of the push tube 104 and the nut assembly 160. For example, the nut assembly 160 may define an outside surface of the nut assembly 169, and the push tube 104 may define an outside surface of the push tube 126. The outside surface of the nut assembly 169 and the outside surface of the push tube 126 may be substantially continuous with each other, each having a common or similar outside diameter. In this configuration, the directly coupled nut assembly 160 and push tube 104 can be placed inside the rotor 146, with the rotor 146 adapted to accommodate and match the common outside diameter, within a desired tolerance, rather than being larger for additional intermediate housing or support structures. In turn, the nut assembly 160 and directly coupled push tube 104 can be configured to accommodate an oversized or larger lead screw or screw shaft 150, facilitating the compact designs described herein with improved torque due to fitting the larger screw shaft 150 in a more compact space. In Figure 3, the distal end 104b of the push tube 104 is shown with a mechanical coupling or similar fastening device at the end of the rod 124. The end of the rod or fastening device 124 can be configured as a threaded coupling or similar device for a machine tool component, located at the distal end 104b of the push tube 104, outside the actuator housing 108. For example, an effector for a welding gun or other machine tool component can be coupled to the end of the rod 124 and can be driven axially by the push rod 104. The end of the rod (or device) 124 is typically positioned by the push tube 104 at or adjacent to the distal end 105b of the linear actuator system 100. The end of the rod 124 defines a common interface that allows the push tube 104 (and more generally, the linear actuator system 100) to be coupled to a variety of different effectors and other machine tool components. The end of the rod 124 may also include a variety of mating features, including pins, clamps, screws, slots, locking mechanisms, etc., which are used to secure the effector or machine tool component to the push tube 104. For example, a welding electrode or similar machine tool component can be coupled or secured directly to the end of the rod 124 and move with the reciprocating motion of the push tube 104.Alternatively, an end effector or other load-bearing component can be attached to the end of rod 124 in order to manipulate the machine tool, for example, a welding gun arm. Adjacent to the tool joint, a grease fitting or similar fitting 129 is provided at the distal end of the push tube 104, positioned at the distal end 105b of the actuator system 100. The grease fitting 129 can be used to receive a supply of lubricant for the internal volume 127. A seal 125, such as an O-ring, can be mounted at the distal (outlet end) of the push tube 104, mitigating lubricant leakage. Figure 4 is an exploded view of the push tube 104 and the front head assembly 112. The front head assembly 112 generally closes the distal end 105b of the actuator housing 108 and helps to provide stability to the push tube 104. For example, the front head assembly 112 includes several components that cooperate to receive the push tube 104 and guide the reciprocating motion of the push tube 104, including the adjustable guide bushing 130, the push tube wiper 136, and the push tube scraper 138, as shown in Figure 4. In one example, the thrust tube 104 may include one or more surface contours that are adapted to the corresponding features of the front head assembly 112 for reciprocating motion along its length. In Figure 4, the thrust tube 104 is shown with a first surface 106a and a second surface 106b. The first and second surfaces 106a and 106b may be positioned on opposite sides of the thrust tube 104 and define a substantially smooth or flat contour along the longitudinal dimension of the thrust tube 104. In other examples, the thrust tube 104 may include more or fewer surfaces, including surfaces in different positions and configurations. Planes 106a and 106b can be keyed or matched to corresponding contours of the front head assembly 112. In this configuration, the front head assembly 112 can receive the thrust tube 104, and planes 106a and 106b can mitigate movement. MA / t / ZUZÓ / UΊ ÓZOO of thrust tube 104 rotation as the thrust tube moves alternately along the longitudinal axis. For example, the adjustable guide bushing 130 can provide a first bushing portion 132a and a second bushing portion 132b that receives the thrust tube 104 within the front head assembly 112. The first bushing portion 132a can define a first keyed contour 134a and the second bushing portion 132b can define a second keyed contour 134b. The adjustable guide bushing 130 can be adapted to receive the thrust tube 104 with the face 106a mating with the first keyed contour 134a and the face 106b mating with the second keyed contour 134b.As the thrust tube 104 moves alternately through the adjustable guide bushing 130, the keyed contours 134a, 134b thereby affect the rotational movement of the thrust tube 104, due to the engagement with the respective contours of planes 106a, 106b. Pins 135 are provided for installing the adjustable guide bushing 130 in system 100. As shown in Figure 4, planes 106a and 106b can be further keyed to the contours of the front head assembly 112, such as the first front head contour 131a and the second front head contour 131b. Similarly, the push tube wiper 136 can include a first wiper mating contour 137a and a second wiper mating contour 137b for mating with the first and second planes 106a and 106b. The push tube scraper 138 also shows the first scraper mating contour 139a and the second scraper mating contour 139b for mating with the first and second planes 106a and 106b. Figure 5 is an exploded view of the linear actuator system 100, which includes a motor assembly 140, lead screw or screw shaft 150, and nut assembly 160 directly coupled to the push tube 104. As shown in Figure 5, the directly coupled nut assembly 160 and push tube 104 are adapted to receive the screw shaft 150, with the nut assembly 160 mating with the external threads of the screw shaft 150. The rotor 146 extends along and over the directly coupled nut assembly 160 and push tube 104 such that the nut assembly 160 and push tube 104 fit in an annular space between the screw shaft 150 and the rotor 146. The rotor 146 is positioned within the actuator housing 108 adjacent to the cooling loop 120. The cooling loop 120 is therefore positioned to remove heat from the motor assembly 140 through the actuator housing 108. The adapter 172 is shown in Figure 5 as connected to the screw shaft 150. The adapter 172 generally serves to couple the screw shaft 150 to the encoder 178 of the main bearing block 114. The adapter 172 can be of an appropriate length to extend from the screw shaft 150 to the encoder 178. In this way, the screw shaft 150 and the actuator system 100 can be manufactured separately. ML / E / ZuZo / u ÓZOO of the encoder 178 and the main bearing block 114, with adapter 172 tuned to effectively extend a screw length 150 to meet the specific characteristics of encoder 178. As an illustration, different types or configurations of encoders may have different sizes. The drive system 100 may include a common-size screw shaft 150, and adapter 172 may be any of a variety of different sizes to connect the common-size screw shaft 150 to the specific encoder for a given application. Figure 6 is a cross-sectional view of the lead screw or screw shaft 150 and the adapter 172. The screw shaft 150 may have a shaft length ls, and the adapter 172 may have an adapter length la. Generally, the shaft length l5 may have a length value that is standardized across a particular series or model of the actuator system 100. The adapter 172 may have an adapter length la that suits the requirements of the encoder 178. Figure 7 is an exploded view of the main bearing block assembly 114 for a linear actuator system 100. As shown in Figure 7 and as described above, the main bearing block 114 may be associated with or otherwise include connectors 115a, 115b, the back cover 116, the thrust bearing 170, the timing washer 171, the lock nut 175, the feedback device or feedback block 176, the rotary encoder 178, and the mounting plate 179. In some cases, an alternative feedback block 176' may be substituted for the feedback block 176. Suitable feedback blocks 176' may include an integrated pilot function with a braking assembly. In this configuration, the braking assembly is configured to brake the rotation of the screw shaft in response to feedback from the separator or encoder.Other variations of the 176 or 176' feedback block may be provided, and are covered in the description herein. Figure 8 is a top view of the linear actuator system 100. In the top view, the cooling loop 120 is shown coupled with the actuator housing 108. For example, the actuator housing 108 can define the recessed feature 110 with the first side of the actuator housing 108. The recessed feature 110 can be measured and formed in such a way that the cooling loop 120 can be at least partially embedded, encapsulated, or seated within the actuator housing 108, along the selected side. In the example in Figure 8, the cooling loop 120 extends along the recessed feature 110 from the first fluid coupling 122a near the proximal end 105a of the actuator housing 108 to the distal end 105b of the actuator housing 108 and back to the second fluid coupling 122b near the proximal end 105a.In this way, the 120 cooling loop can resemble a U-shaped duct. In other examples, the. ML / E / ZuZo / uO OZOO cooling loop 120 can be defined by other geometries, including geometries where the cooling loop 120 extends the actuator housing 108 multiple times, such as extending in a serpentine pattern between the proximal and distal ends 105a, 105b, similar to a radiator or other cooling structure. Figure 9 is a front view of the actuator system 100, showing an anti-rotation feature for the push tube 104. As illustrated in the front view, the push tube 104 may include planes 106a and 106b on opposite sides. The front head assembly 112 may include one or more components that are keyed to planes 106a and 106b. For example, as described above, the front head assembly 112 may house a guide bushing and other features that have contours matching those of planes 106a and 106b. In this way, as the push tube 104 moves alternately, rotational movement of the push tube 104 can be prevented. Figure 10 is a rear view of the linear actuator system 100. Connectors 115a and 115b are shown in the rear view. Connectors 115a and 115b can be adapted for power and control communications. For example, one or both of connector 115a and connector 115b can be used to connect the linear actuator system 100 to a power supply, a remote computing unit, or another external system or process. Each of connectors 115a and 115b can be configured to connect the linear actuator system 100 to different systems. For example, connector 115a can be configured to connect the linear actuator system 100 to a power supply, and connector 115b can be configured to connect the linear actuator system 100 to a remote computing unit. In other cases, more or fewer connectors can be provided, as appropriate for a given application. Figure 11 is a flowchart illustrating a process or method 1100 for operating the linear actuator system. For example, process 1100 can be used with a linear actuator system 100, in any of the examples and configurations described herein. While the specific operations of method 1100 are presented in a particular arrangement, method 1100 may include more, fewer, or different steps than those illustrated, consistent with the teachings of this description. The operations of method 1100 can also be performed in any order or combination, with or without any of the additional processes and techniques described herein. In operation 1104, the linear actuator motor is operated. The motor has a stator and a rotor arranged around a linear actuator screw shaft. The rotor rotates around a longitudinal axis. For example, and with reference to Figure 2, the motor assembly 140 of the linear actuator system 100 is operated. The stator windings 142 and the rotor windings 146 are ML / E / ZuZo / u ÓZOO are arranged around the lead screw or screw axis 150. The rotor 146 rotates around the longitudinal axis AA. In operation 1108, a push tube is driven along the longitudinal axis. The push tube is directly coupled to a nut assembly in a threaded coupling with the screw shaft. For example, and with reference to Figure 2, the push tube 104 is driven in reciprocating motion along the longitudinal axis AA. The push tube 104 is directly coupled to the nut assembly 160. In one example, the direct coupling of the push tube 104 and the nut assembly 160 may include a direct physical coupling between the nut assembly 160 and the proximal end of the push tube 104, in the absence of any additional housings or bearing structures. The nut assembly 160 is threaded with the screw shaft 150. In operation 1112, the push tube is loaded. The push tube extends from a proximal end in direct physical coupling with the nut assembly to a distal end subjected to the load. For example, and with reference to Figures 2 and 3, the push tube 104 can be loaded onto the end of the rod or clamping device 124. In one example, the end of the rod 124 can be coupled with a welding electrode or welding gun effector for use in resistance welding operations. There may be substantial mechanical loading on the welding electrodes to provide the mechanical coupling required to ensure high-quality welds. The greater the axial mechanical load and radial (inductive) load due to the welding current, the greater the potential for displacement of the rod end and related welding electrode. Inductive reaction forces can cause the welding gun and actuator assembly to deviate from the axis, causing the electrodes to slip or move out of position and potentially affecting weld quality. In operation 1116, rotational stability is provided to the push tube. The push tube is supported by a bushing or bearing near its distal end. For example, with reference to Figures 2 and 4, the adjustable guide bushing 130 supports the push tube 104. The adjustable guide bushing 130 includes keyed contours 134a, 134b that are adapted for engagement with the corresponding faces 106a, 106b of the push tube 104. As the push tube 104 moves alternately along the longitudinal axis AA, the adjustable guide bushing 130 can therefore mitigate the rotational movement of the push tube 104, with the first and second portions of the bushing 132a, 132b preventing the rotational movement of the push tube 104. In operation 1120, heat is dissipated by a cooling loop. For example, and with reference to Figures 2 and 8, the cooling loop 120 can be embedded, encapsulated, or partially seated within the actuator housing 108. In some cases, the housing MA / t / ZUZÓ / UΊ ÓZOO of the actuator 108 may define a recessed feature 110 with the cooling loop 120 placed at least partially therein. The cooling loop 120 extends along the length of the actuator housing 108 and along the stator and rotor arranged around the screw axis. A thermally conductive material 123 may be placed at least partially around the cooling loop 120, conducting heat from the housing to the cooling loop 120. EXAMPLES The systems, devices, and techniques related to linear actuators are described herein. A linear actuator typically includes a thrust tube configured for reciprocating motion along a longitudinal axis. A distal end of the thrust tube is configured to engage a machine tool, such as a welding, pressing, clamping, or other tool, enabling the linear actuator to drive the machine tool in reciprocating motion with the thrust tube. The linear actuator can be used in automated assembly or manufacturing environments and other environments where the distal end of the thrust tube is subjected to load, including axial (e.g., mechanical) and transverse or radial (e.g., mechanical or current-based inductive) loads, which generate forces that tend to displace the thrust tube at the distal end. As described above, a nut assembly directly couples a rotor and screw shaft to the thrust tube to provide an efficient and compact design. Furthermore, the actuator configurations described herein are capable of accepting a modular water-cooling assembly or other active or passive modular cooling unit. The addition of the cooling assembly increases the motor's capacity, allowing the actuator to operate at a higher capacity while maintaining acceptable system temperatures. Although it will be appreciated that a variety of examples and implementations are within the scope and spirit of the description and appended claims, a number of examples and improvements are described below for illustrative purposes.Thus, the examples are not intended to be exhaustive or to limit the description to the precise forms described, and it will be evident to an expert in the technique that many modifications and variations are possible in view of the teachings above. Example 1. A linear actuator system is described as a first example. The linear actuator system includes an actuator housing that extends along a longitudinal axis. The linear actuator system further includes a motor assembly comprising a stator coupled to the actuator housing and a rotor that extends within the actuator housing. The linear actuator system also includes a screw shaft that extends The linear actuator system also includes a nut assembly coupled to the screw shaft. The linear actuator system further includes a push tube extending from a proximal end coupled directly to the nut assembly to a distal end disposed at least partially outside the housing. The nut assembly is configured to convert the rotational motion of the rotor about the longitudinal axis into linear motion of the push tube along the longitudinal axis. A number of feature enhancements and additional features are applicable to the first example and are considered in light of this description. These feature refinements and additional features can be used individually or in any combination. As such, each of the following features to be discussed can be used, but is not required to be used, with any other combination of features from the first example. To illustrate, in one embodiment, the nut assembly is coupled directly to the proximal end of the push tube. The nut assembly is adapted to actuate the distal end of the push tube between a first retracted position close to the actuator housing and a second extended position away from the actuator housing, in the absence of an additional housing or bearing structure intervening between the nut assembly and the proximal end of the push tube. In another embodiment, the nut assembly extends continuously from a first end opposite the push tube to a second end that abuts the push tube. The nut assembly further includes a defined mechanical coupling at the second end, in direct physical engagement with the proximal end of the push tube. The mechanical coupling may also include a threaded coupling, press fit, or interference fit at the second end of the nut assembly and adapted to engage the proximal end of the push tube within a common outside diameter of the push tube and the nut and bolt assembly. In another embodiment, the nut assembly includes a screw nut fitted around a threaded portion of the screw shaft and extending continuously from a first end opposite the push tube to a second end that abuts the push tube. In this configuration, the nut assembly may include a mechanical coupling at the second end of the roller nut, in direct physical coupling with the proximal end of the push tube. In another embodiment, a cooling loop is embedded, encapsulated, or at least partially seated within the actuator housing, with a thermally conductive material disposed at least partially around the cooling loop to conduct heat away from the actuator housing. The cooling loop may include a fluid flow conduit and further comprises a defined recessed feature along a selected side of the actuator housing to accept the conduit and the thermally conductive material. In another embodiment, a cooling channel is formed or machined into a main portion of the actuator housing body. A cooling loop extends along the channel from a first end in a proximal portion of the actuator housing to a distal portion of the actuator housing and back to a second end in the proximal portion, adjacent to the first end. In another embodiment, the stator is coupled to an inner surface of the actuator housing, and the rotor is arranged around the axis of the screw and nut assembly. The thrust tube is positioned radially inward within an annular region defined between an outer diameter of the screw and nut assembly and the inner surface of the rotor. In another embodiment, the linear actuator system also includes an adapter rotatably coupled to a threaded portion of the screw shaft and extending along the longitudinal axis to a coupling operable with a controller at one end of the actuator housing, opposite the push tube. The controller includes a separator or encoder configured to determine a rotational position of the screw shaft via the operative coupling with the adapter. In another configuration, the linear actuator system also includes a braking assembly arranged around the adapter between the threaded portion of the screw shaft and the controller. The braking assembly is configured to brake the rotation of the screw shaft in response to feedback from the separator or encoder. In another embodiment, a bushing or bearing is placed around the thrust tube near the distal end. The bushing or bearing is keyed into a flat or perimeter contour feature adapted to prevent rotation of the thrust tube during linear motion along its longitudinal axis. Example 2. As a second example, a method is described. The method includes operating a motor that has a stator and a rotor arranged around a screw shaft. The rotor rotates around a longitudinal axis of the screw shaft. The method further includes driving a thrust tube along the longitudinal axis. The thrust tube is directly coupled to a nut assembly in a threaded connection with the screw shaft. The method further includes loading the thrust tube. The thrust tube extends from a proximal end in direct physical connection with the nut assembly to a distal end subjected to the load. The method further includes providing rotational stability to the thrust tube. The thrust tube is supported by a bushing or bearing near the distal end. ML / E / ZuZo / u Ozoo A number of feature enhancements and additional features are applicable to the second example and are considered in light of this description. These feature refinements and additional features can be used individually or in any combination. As such, each of the following features to be discussed can be used, but is not required to be used, with any other combination of features from the second example. To illustrate, in one embodiment, actuating the push tube involves direct physical coupling between the nut assembly and the proximal end of the push tube, without any additional housing or bearing structures intervening between them. In this configuration, the nut assembly can be continuously extended around the screw axis from a first end opposite the push tube to a second end that abuts the push tube. Consequently, the direct physical coupling may include a threaded coupling, press fit, or interference fit defined at the second end. In some cases, the push tube load may include the threaded coupling or fit that receives the proximal end of the push tube within an outside diameter of the nut assembly. In another embodiment, providing rotational stability may include a keyed bushing or bearing to prevent rotation of the thrust tube when driven along its longitudinal axis. For example, the thrust tube may include at least one flat or perimeter contour feature adapted to prevent rotation when mated with a complementary flat or perimeter contour feature on the bushing or bearing. In another embodiment, the method further includes dissipating heat with a cooling loop at least partially embedded, encapsulated, or seated within a housing that extends around the stator and rotor arranged around the screw shaft, with a thermally conductive material arranged at least partially around the cooling loop that conducts heat from the housing to the cooling loop. In another embodiment, the method further includes determining a rotational position of the screw shaft using a controller comprising a spacer or encoder. The spacer or encoder is operably coupled with an adapter that extends along the longitudinal axis from an operational coupling with the spacer or encoder to a rotational coupling with a threaded portion of the screw shaft. Additionally, the method also includes braking the rotation of the screw shaft with a braking assembly arranged around the adapter in response to feedback from the controller. Example 3. As a third example, an apparatus is described. The apparatus includes a stator coupled to an actuator housing. The apparatus further includes a rotor positioned within the actuator housing adjacent to the stator. The apparatus further includes a screw shaft disposed within the rotor, extending along a shaft of the actuator housing. The apparatus further includes a nut assembly coupled around a threaded portion of the screw shaft. The apparatus further includes a thrust tube coupled with the nut assembly. The thrust tube extends continuously along the shaft from a proximal end to a distal end. A mechanical fit defines a direct physical coupling between the proximal end of the thrust tube and the nut assembly, in the absence of any additional load-bearing components intervening therein. A number of feature enhancements and additional features are applicable to the third example and are considered in light of this description. These feature refinements and additional features can be used individually or in any combination. As such, each of the following features to be discussed can be used, but is not required to be used, with any other combination of features from the third example. To illustrate, in one embodiment, the mechanical fit comprises a threaded coupling, press fit, or interference fit configured to accept the proximal end of the thrust tube within an outside diameter of the nut assembly, in the absence of an additional housing or bearing structure intervening in a defined annular region between the outside diameter of the nut assembly and an inner surface of the rotor. In another embodiment, the apparatus includes a cooling loop embedded, encapsulated, or at least partially seated within a defined recessed feature in a major portion of the actuator housing body. A thermally conductive material is placed at least partially around the cooling loop to conduct heat away from the actuator housing. In another embodiment, the device also includes an adapter rotatably coupled to the threaded portion of the screw shaft and extending along the shaft to an operational coupling with an encoder. The encoder is configured to determine a rotational position of the screw shaft through the operational coupling with the adapter. In some cases, a brake assembly is provided along the adapter with a feedback device mounted on the brake assembly via a pilot feature. The brake assembly is configured to brake the rotation of the screw shaft in response to the operation of the feedback device. Although this description is made with reference to particular examples and embodiments, changes may be made and equivalents substituted without departing from the scope of the invention as claimed. Modifications may also be made to adapt these teachings to different industries, materials, and technologies, not limited to the particular examples described, and encompassing all embodiments within the language of the appended claims.
Claims
1. A linear actuator system, characterized in that it comprises: an actuator housing extending along a longitudinal axis; a motor assembly including a stator coupled to an inner surface of the actuator housing and a rotor extending within the actuator housing; a screw shaft extending within the rotor, along the longitudinal axis; a nut assembly coupled with the screw shaft; and a push tube extending from a proximal end coupled directly with the nut assembly to a distal end disposed at least partially outside the housing; wherein the nut assembly is configured to convert the rotational motion of the rotor about the longitudinal axis into linear motion of the push tube along the longitudinal axis;and wherein the rotor is arranged around the axis of the screw and the nut assembly, with the thrust tube arranged radially inwards from an annular region defined between an outer diameter of the nut assembly and an inner surface of the rotor.
2. The linear actuator system according to claim 1, further characterized in that the nut assembly is directly coupled to the proximal end of the push tube and is adapted to actuate the distal end of the push tube between a first retracted position close to the actuator housing and a second extended position away from the actuator housing, in the absence of an additional housing or bearing structure intervening between the nut assembly and the proximal end of the push tube.
3. The linear actuator system according to claim 1, further characterized in that the nut assembly extends continuously from a first end opposite the push tube to a second end that abuts the push tube, and further comprising a defined mechanical coupling at the second end, in direct physical coupling with the proximal end of the push tube.
4. The linear actuator system according to claim 3, further characterized in that the mechanical coupling comprises a threaded coupling, press fit or interference fit at the second end of the nut assembly and adapted to couple the proximal end of the push tube within a common outer diameter of the push tube and nut assembly.
5. The linear actuator system according to claim 1, further characterized in that the nut assembly comprises a roller nut coupled around a threaded portion of the screw shaft and extending continuously from a first end opposite the push tube to a second end abutting the push tube, and further comprising a mechanical coupling at the second end of the roller nut, in direct physical coupling with the proximal end of the push tube.
6. The linear actuator system according to claim 1, further characterized in that it additionally comprises a cooling loop embedded at least partially, encapsulated or seated within the actuator housing, with a thermally conductive material disposed at least partially around the cooling loop to conduct heat away from the actuator housing.
7. The linear actuator system according to claim 6, further characterized in that the cooling loop comprises a fluid flow conduit and further comprises a recessed feature defined along a selected side of the actuator housing to accept the conduit and the thermally conductive material.
8. The linear actuator system according to claim 1, further characterized in that it additionally comprises a cooling channel formed or machined in a main portion of the actuator housing body, wherein a cooling loop extends along the channel from a first end in a proximal portion of the actuator housing to a distal portion of the actuator housing and back to a second end in the proximal portion adjacent to the first end.
9. The linear actuator system according to claim 1, further characterized in that it additionally comprises an adapter rotatably coupled to a threaded portion of the screw shaft and extending along the longitudinal axis to a coupling operable with a controller at a proximal end of the actuator housing, opposite the push tube, wherein the controller comprises a separator or encoder configured to determine a rotational position of the screw shaft through the operable coupling with the adapter.
10. The linear actuator system according to claim 9, further characterized in that it additionally comprises a braking assembly disposed around the adapter between the threaded portion of the screw shaft and the controller, wherein the braking assembly is configured to brake the rotation of the screw shaft in response to feedback from the separator or encoder.
11. The linear actuator system according to claim 1, further characterized in that it additionally comprises a bushing or bearing disposed around the thrust tube near the distal end, wherein the bushing or bearing has a flat or peripheral contour feature adapted to prevent rotation of the thrust tube during linear motion along the longitudinal axis.
12. A method characterized in that it comprises: operating a motor having a stator coupled to an inner surface of an actuator housing and a rotor disposed about a screw shaft, wherein the rotor rotates about a longitudinal axis; actuating a push tube along the longitudinal axis, wherein the push tube is directly coupled to a nut assembly in threaded coupling with the screw shaft; and loading the push tube, wherein the push tube extends from a proximal end in direct physical coupling with the nut assembly to a distal end subjected to the load;and providing rotational stability to the thrust tube, wherein the thrust tube is supported by a bushing or bearing near the distal end, and wherein the rotor is disposed around the axis of the screw and nut assembly, with the thrust tube arranged radially inward from an annular region defined between an outer diameter of the nut assembly and an inner surface of the rotor.
13. The method according to claim 12, further characterized in that the drive of the push tube comprises direct physical coupling between the nut assembly and the proximal end of the push tube, without any additional housing or bearing structures intervening between them.
14. The method according to claim 13, further characterized in that the nut assembly extends continuously around the axis of the screw from a first end opposite the push tube to a second end that abuts the push tube and wherein the direct physical coupling comprises a threaded coupling, press fit or interference fit defined at the second end.
15. The method according to claim 14, further characterized in that the thrust tube load comprises the threaded coupling, press fit or interference fit that receives the proximal end of the thrust tube within an outside diameter of the nut assembly.
16. The method according to claim 12, further characterized in that providing rotational stability comprises the bushing or bearing being keyed to prevent rotation of the thrust tube when driven along the longitudinal axis, wherein the thrust tube comprises at least one flat or peripheral contour feature adapted to prevent rotation when coupled with a complementary flat or peripheral contour feature on the bushing or bearing. 17.- The method according to claim 12, further characterized in that it additionally comprises dissipating heat with a cooling loop at least partially embedded, encapsulated or seated within a housing extending around the stator and rotor arranged around the screw shaft, with a thermally conductive material disposed at least partially around the cooling loop that conducts heat from the housing to the cooling loop.
18. The method according to claim 12, further characterized in that it additionally comprises determining a rotational position of the screw shaft with a controller comprising a spacer or encoder, wherein the spacer or encoder is operably coupled with an adapter extending along the longitudinal axis from an operative coupling with the spacer or encoder to a rotational coupling with a threaded portion of the screw shaft.
19. The method according to claim 18, further characterized in that it additionally comprises braking the rotation of the screw shaft with a braking assembly arranged around the adapter in response to feedback from the controller.
20. An apparatus comprising the linear actuator system according to claim 1, characterized in that: the rotor is placed within the actuator housing, close to the stator; the screw shaft is placed within the rotor, which extends along the axis of the actuator housing; the nut assembly is engaged around a threaded portion of the screw shaft; and the push tube extends continuously along the axis from the proximal end to the distal end, wherein a mechanical fit defines a direct physical coupling between the proximal end of the push tube and the nut assembly, in the absence of additional load-bearing components intervening between them.
21. The apparatus according to claim 20, further characterized in that the mechanical fit comprises a threaded coupling, press fit or interference fit configured to accept the proximal end of the push tube within an outer diameter of the nut assembly, in the absence of an additional housing or bearing structure intervening in an annular region defined between the outer diameter of the nut assembly and an inner surface of the rotor.
22. The apparatus according to claim 20, further characterized in that it additionally comprises a cooling loop embedded, encapsulated or at least partially seated within a defined recessed feature in a main portion of the actuator housing body, with a thermally conductive material disposed at least partially around the cooling loop to conduct heat away from the actuator housing.
23. The apparatus according to claim 20, further characterized in that it additionally comprises an adapter rotatably coupled to the threaded portion of the screw shaft and extending along the shaft to an operational coupling with an encoder, wherein the encoder is configured to determine a rotational position of the screw shaft through the operational coupling with the adapter.
24. The apparatus according to claim 23, further characterized in that it additionally comprises a braking assembly disposed along the adapter with a feedback device mounted on the braking assembly using a pilot feature, wherein the braking assembly is configured to brake the rotation of the screw shaft in response to the operation of the feedback device.