Patent Publication Number: US-11649881-B2

Title: Mechanical spring actuator

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/821,390, filed Mar. 17, 2020, which is a divisional of U.S. patent application Ser. No. 15/228,051, filed Aug. 4, 2016 and issued as U.S. Pat. No. 10,626,967 on Apr. 21, 2020, which application claims the benefit of U.S. Provisional Patent Application Ser. No. 62/200,774, filed Aug. 4, 2015 and entitled “Mechanical Spring Actuator,” the entire disclosures of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present disclosure is directed generally to a mechanical linear actuator, and more specifically to a mechanical linear actuator that can adjust the actuation load as a function of an object&#39;s weight. 
     BACKGROUND 
     A linear actuator is an actuator that creates motion in a straight line, unlike a conventional electric motor that creates a circular motion. Linear actuators are commonly used in a wide variety of applications, including but not limited to positioning a seat such as an aircraft or automotive passenger seat, mitigating blast seat shock, position locking, or in any system that requires mechanical actuation, among many other applications. 
     Existing linear actuators, however, function largely the same regardless of the weight of the object that they are moving or positioning. Thus, existing linear actuators do not consider or adequately respond to the weight of the object. Accordingly, there is a need in the art for a mechanical linear actuator that can adjust the actuation load as a function of an object&#39;s weight. 
     SUMMARY OF THE INVENTION 
     The present disclosure is directed to inventive mechanical linear actuators. The inventive mechanical linear actuators provide a mechanism for positioning a seat of, for example, an aircraft or automobile, through linear motion. The mechanical linear actuators can also be used with any other machine or mechanism requiring load adjustment, shock mitigation, or controlled rate positioning. For example, the linear actuator can be configured to adjust the actuation load as a function of the seat occupant&#39;s, or other object&#39;s, weight. Additionally, the mechanical linear actuator may include a hydraulic component to control forces acting on the device or potentially energy stored by the device and, consequently, control the speed of actuation. Devices without a hydraulic component can rely on coulombic damping, mechanical damping in which energy is absorbed via sliding friction, at, for example, the screw/nut interface to control the speed of actuation. The linear actuator disclosed or otherwise envisioned herein may also include a mechanical lock to retain the linear actuator at any portion of stroke to hold an associated seat mechanism or other mechanism in a desired position. The linear actuator may also include an adjustable locking collar to adjust the stroke and bottoming positions of the device. 
     Generally, in one aspect, a linear actuator is provided. The linear actuator includes: a housing with a first end and a second end, and defining a central cavity extending axially therethrough; a tube having a first portion and a second portion, the first portion arranged to slide within the central cavity of the housing, and the second portion extending outwardly from the second end of the housing; a first elongated rotatable screw positioned axially within the central cavity of the housing and connected to the tube, wherein the first elongated rotatable screw is coaxial with the tube; a first nut positioned within the central cavity of the housing and mounted about the first elongated rotatable screw, wherein the first nut is configured to move axially within the central cavity of the housing as the first elongated rotatable screw rotates; a second elongated rotatable screw positioned axially within the central cavity of the housing; a second nut positioned within the central cavity of the housing and mounted about the second elongated rotatable screw, wherein the second nut is configured to move axially within the central cavity of the housing as the second elongated rotatable screw rotates; and a spring positioned within the central cavity of the housing and around the second elongated rotatable screw between the second nut and the second end of the housing. 
     According to an embodiment, the linear actuator further comprises gears coupled to the first and second elongated rotatable screws, wherein the gears are configured to enable concurrent rotation of the first and second elongated rotatable screws. 
     According to an embodiment, the linear actuator further comprises a spline positioned about either the first elongated rotatable screw or the second elongated rotatable screw, the spline configured to selectively allow rotation of the first and second elongated rotatable screws. 
     According to an embodiment, the linear actuator further comprises a lock/release lever in communication with the spline. 
     According to an embodiment, the linear actuator further comprises an adjustable locking collar. 
     According to an embodiment, the first elongated rotatable screw comprises a first plurality of screw threads on its outer surface and the first nut comprises a first plurality of nut threads on its inner surface, the first plurality of screw threads and the first plurality of nut threads configured to mate to enable the first nut to move axially within the central cavity of the housing as the first elongated rotatable screw rotates. 
     According to an embodiment, the second elongated rotatable screw comprises a second plurality of screw threads on its outer surface and the second nut comprises a second plurality of nut threads on its inner surface, the second plurality of screw threads and the second plurality of nut threads configured to mate to enable the second nut to move axially within the central cavity of the housing as the second elongated rotatable screw rotates. 
     According to an embodiment, the first nut is coaxial with the first elongated rotatable screw and the tube. 
     According to an embodiment, the spring directly contacts the second nut in the housing. 
     According to an embodiment, the spring is configured to bias the second nut away from the second end of the housing. 
     According to an embodiment, the gears that are coupled to the first and second elongated rotatable screws are arranged within the housing. 
     According to an embodiment, the first elongated rotatable screw has a first length and the second elongated rotatable screw has a second length that is different than the first length of the first elongated rotatable screw. 
     According to an embodiment, the second elongated rotatable screw is arranged closer to the first end of the housing than the first elongated rotatable screw. 
     According to an embodiment, the first elongated rotatable screw has a first diameter and the second elongated rotatable screw has a second diameter that is different than the first diameter of the first elongated rotatable screw. 
     According to an embodiment, the first nut is arranged closer to the first end of the housing than the second nut. 
     According to an embodiment, the first nut has a first diameter and the second cylindrical nut has a second diameter that is different than the first diameter of the first nut. 
     According to an embodiment, the spring is longer than the first elongated rotatable screw. 
     According to an embodiment, the first elongated rotatable screw is connected to the tube within an end of the tube. 
     According to an embodiment, the tube surrounds the first elongated rotatable screw. 
     According to an embodiment, the spring extends alongside of the first nut. 
     These and other aspects and embodiments of the invention will be described in greater detail below, and can be further derived from reference to the specification and figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be more fully understood and appreciated by reading the following Detailed Description of Embodiments in conjunction with the accompanying drawings. 
         FIG.  1    is a schematic representation of a cutaway view of a linear actuator, in accordance with an embodiment. 
         FIG.  2    is a schematic representation of a linear actuator, in accordance with an embodiment. 
         FIG.  3    is a schematic representation of a cutaway view of a linear actuator, in accordance with an embodiment. 
         FIG.  4    is a schematic representation of a cutaway view of a linear actuator, in accordance with an embodiment. 
         FIG.  5    is a schematic representation of a linear actuator, in accordance with an embodiment. 
         FIG.  6    is a schematic representation of a cutaway view of a linear actuator, in accordance with an embodiment. 
         FIG.  7    is a schematic representation of a linear actuator, in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     The present disclosure describes various embodiments of a mechanical linear actuator providing a mechanism for positioning a seat of, for example, an aircraft or automobile, through linear motion, including a mechanism that accounts for the weight of the person or object being positioned. According to an embodiment, therefore, is a linear actuator that may include a mechanical lock to retain the linear actuator at any portion of stroke to hold an associated seat mechanism or other mechanism in a desired position. The linear actuator may also include an adjustable locking collar to adjust the stroke and bottoming positions of the device. The mechanical linear actuator can also be used with any other machine or mechanism requiring load adjustment, shock mitigation, or controlled rate positioning, among other uses. 
     According to an embodiment, the various embodiments of the mechanical linear actuator may include a hydraulic component to control forces acting on the device or potentially energy stored by the device and, consequently, control the speed of actuation. Devices without a hydraulic component can rely on coulombic damping, mechanical damping in which energy is absorbed via sliding friction, at, for example, the screw/nut interface to control the speed of actuation. Many other configurations are possible. 
     Referring now to the drawings, wherein like reference numerals refer to like parts throughout, there is seen in  FIG.  1    a cutaway view of a linear actuator  100 . The linear actuator comprises a housing  12  and a piston tube  14 . The housing comprises a proximal end  16  and a distal end  18 , and defines a central cavity that extends axially through the housing. When assembled, piston tube  14  is partially positioned within the central cavity of the housing  12 , and partially extends from the opening in the housing at the distal end  18  of the housing. Piston  28  of the linear actuator is slidable within the central cavity of the housing. 
     Linear actuator  100  also comprises a screw  20  positioned within the housing  12 . The screw is threaded on its outer surface. The linear actuator also comprises a nut  22  positioned within the housing, which according to an embodiment can be cylindrical among other shapes. The nut  22  is mounted about the screw  20  and includes a thread (e.g., single or multiple start, or any type of thread profile) on the inner surface of the nut, which is complementary to the threading on the screw  20  in order to enable the nut to move axially within the housing as the screw rotates. 
     Linear actuator  100  also comprises a spring  24  positioned within the housing about the screw  20  and between the nut  22  and a portion of the piston tube  14 . The spring acts to bias the piston tube away from the nut. Rotation of the screw  20  in a first direction can move the nut  22  in the direction of the piston tube, therefore increasing the pre-load force of the spring on the piston tube. Rotation of the screw  20  in an opposite, second direction can move the nut away from the piston tube, therefore decreasing the pre-load force of the spring on the piston tube. 
     According to an embodiment, the linear actuator  100  also comprises an adjustment knob  26  which is mounted on and extends into the housing  12 . The adjustment knob interfaces the screw though the use of gears or a direct drive, enabling rotation of the screw  20  using the knob. The adjustment knob may be controlled either mechanically or electronically by an external component reacting to the weight of an occupant of the seat, for example. According to an embodiment, if gears  30  are used as the interface between the knob and the screw, such gears can be, for example, bevel, worm, or helical gears, and can be of an appropriate gear ratio to achieve a desired nut travel and preload. Many other types of gears are possible. 
     According to an embodiment, the linear actuator  100  also comprises a hydraulic dampening component  32  having a piston rotatably coupled to the screw. A free-rotating coupling  32  between the screw and the piston allows for rotation of the screw and linear translation of the piston within the hydraulic dampening component  32 , where the rotation of the screw does not affect the hydraulic component. According to an embodiment, the hydraulic system of the linear actuator  100  can also comprise an accumulator  50 . The accumulator can be a thermal and/or rod accumulator. 
     According to an embodiment, the linear actuator  100  can also comprise a mechanical lock  36  to retain the linear actuator at any portion of stroke to hold an associated seat mechanism or other mechanism in a desired position. 
     Referring to  FIG.  2   , according to an embodiment, is an outside view of the linear actuator  100  of  FIG.  1   . The linear actuator comprises a housing  12  and a piston tube  14  extending from the distal end of the housing. Also shown are an adjustment knob  26 , and a lock  36 . 
     Referring to  FIG.  3   , in one embodiment, is a cutaway view of a linear actuator  200 . The linear actuator comprises a housing  12  and a piston tube  14 . The housing comprises a proximal end  16  and a distal end  18 , and defines a central cavity that extends axially through the housing. When assembled, piston tube  14  is partially positioned within the central cavity of the housing  12 , and partially extends from the opening in the housing at the distal end  18  of the housing. Piston  28  of the linear actuator is slidable within the central cavity of the housing. 
     This embodiment of the linear actuator comprises a first spring  24   a,  but also includes a second spring  24   b.  The linear actuator  200  also comprises a first spring retainer  38  and a second spring retainer  40 , which allow for bifurcated action. It should be noted that trifurcation or any combination of changing spring rate vs. stroke can be achieved according to the same principles. The first retainer  38  is positioned within the housing  12  between the first spring  24   a  and the piston tube  14 . The first retainer receives the spring  24   a  in an opening in the first retainer and retains the first spring at the first retainer&#39;s distal end. As shown, the spring still is able to exert a force on the piston tube via the first retainer. 
     The second retainer  40  comprises proximal and distal ends and is positioned in the housing  12  about the screw  20 . The second spring  24   b  is positioned in the housing  12  about the screw, between the proximal end  16  of the housing and the second retainer  40 . The second spring biases the second retainer away from the proximal end of the housing. The second retainer can interface with the outer wall of the proximal end of the first retainer, thus enabling the piston tube to exert a force on the second spring via the first retainer. 
     According to an embodiment, a force exerted on the piston tube  14  causes the first spring to compress and, thus, causes the piston tube and first retainer  38  to move axially within the opening of the housing toward the proximal end of the housing. As the outer wall of the proximal end of the first retainer  38  reaches the second retainer  40 , continued force causes the second spring to compress (in addition to the first spring) and, thus, causes the piston tube, first retainer, and second spring to move axially within the opening of the housing toward the proximal end of the housing. Because both springs are being compressed, the force needed to stroke the piston tube near the end of its stroke is greater than the force needed at the beginning of its stroke when only the first spring is being compressed. 
     Referring to  FIG.  4   , in one embodiment, is a cutaway view of a linear actuator  300 . The linear actuator comprises a housing  12  and a piston tube  14 . The housing defines a central cavity that extends axially through the housing. When assembled, piston tube  14  is partially positioned within the central cavity of the housing  12 , is slidable, and partially extends from the opening in the housing at the distal end of the housing. The screw  20 , which is threaded on its outer surface, is elongated and rotatable and is positioned axially in the housing. The nut  22  of the linear actuator  300  is cylindrical and is positioned in the housing adjacent to the piston tube  14 . The nut  22  is mounted about the screw and includes a thread on the inner surface. The thread of the nut mates with the thread of the screw to enable the nut to move axially within the housing as the screw rotates. The screw threads can be any type and can include any number of starts. The spring  24  of the linear actuator  300  is positioned within the housing, about the screw, and between the nut and the proximal end of the housing. The spring acts to bias the nut, and therefore the piston tube, away from the proximal end of the housing. 
     According to an embodiment, the linear actuator  300  comprises a spline  42  positioned around the screw  20  and configured to selectively allow rotation of the screw using a lock/release lever  44 , or similar component for controlling the spline. When the spline is engaged with the screw, the spine prevents rotation of the screw and, thus, the nut is not able to move axially within the housing. When the spline is not engaged with the screw, the screw is able to rotate, thus allowing the nut to move axially within the housing. During such movement, the spring provides a resistive force in the direction of spring compression, and an assisting force in the direction of spring extension. The device can also provide coulombic friction damping (or any other form of damping) at the screw/nut interface to help control the speed of actuation. The linear actuator may also include an adjustable locking collar  46  to adjust the stroke and bottoming positions of the device. 
     Referring to  FIG.  5   , according to an embodiment, is an outside view of the linear actuator  300  of  FIG.  4   . The linear actuator  300  comprises a housing  12  and a piston tube  14  extending from the distal end of the housing. Also shown are a lock/release lever  44  and an adjustable locking collar  46 . 
     Referring to  FIG.  6   , in one embodiment, is a cutaway view of a linear actuator  400 . The linear actuator comprises a housing  12  and a piston tube  14 . The housing defines a central cavity that extends axially through the housing. When assembled, piston tube  14  is partially positioned within the central cavity of the housing  12 , is slidable, and partially extends from the opening in the housing at the distal end of the housing. 
     According to an embodiment, linear actuator  400  comprises a first screw  20   a  and a second screw  20   b.  The first screw  20   a  is elongated and rotatable and is positioned axially in the first opening of the housing. The first screw  20   a  includes a thread on the outer surface of the first screw. A first nut  22   a  is cylindrical and is positioned in the first opening of the housing adjacent to the piston tube. It is mounted about a screw  20  of the linear actuator and includes a thread on its inner surface. The thread of the first nut  22   a  mates with the thread of the first screw  20   a  to enable the first nut to move axially within the first opening of the housing as the first screw rotates. The screw threads can be of any pitch and can include any number of starts. 
     The second screw  20   b  is elongated and rotatable and is positioned axially in the second opening of the housing. The second screw includes a thread on the outer surface of the second screw. A second nut  22   b  of the linear actuator is cylindrical and is positioned in the second opening of the housing. It is mounted about the second screw  20   b  and includes a thread on its inner surface. The thread of the second nut  22   b  mates with the thread of the second screw  20   b  to enable the second nut to move axially within the second opening of the housing as the second screw rotates. The screw threads can be of any pitch and can include any number of starts. 
     According to an embodiment, the spring  24  of the linear actuator  400  is positioned in the second opening of the housing, about the second screw  20   b,  and between the second nut  22   b  and the distal end of the housing. The spring  24  acts to bias the second nut away from the distal end of the housing. The gears  30  are coupled to the first and second screws, therefore enabling concurrent rotation of the screws. 
     According to an embodiment, the linear actuator  400  can also include a spline positioned about either the first or the second screw and configured to selectively allow rotation of the screws using a lock/release lever, or similar component for controlling the spline. When the spline is engaged, the spine prevents rotation of the screws and, thus, the nuts are not able to move axially within the housing. When the spline is not engaged, the screws are able to rotate, thus allowing the nuts to move axially within the housing. During such movement, the spring provides a resistive force in the direction of spring compression, and an assisting force in the direction of spring extension. 
     According to an embodiment, the linear actuator  400  can also provide coulombic friction damping (or any other type of damping) at both screw/nut interfaces to help control the speed of actuation. The gears can be of any type, including, for example, worm, spur, or helical gears. The ratios between the gears coupled to the first and second screws can be designed to allow a relatively lesser spring force to create a relatively larger output force on the piston tube (e.g., a 5-to-1 gear size ratio from first-spring to second-spring). It should be understood that the ratio between the gears can be of any ratio designed to obtain a desired output or mechanical advantage. 
     Although the present invention has been described in connection with a preferred embodiment, it should be understood that modifications, alterations, and additions can be made to the invention without departing from the scope of the invention as defined by the claims.