Abstract:
The linear-to-rotary actuator includes an elongated drive member constrained to linear movement, and a rotary member constrained to rotary movement. The elongated drive member has a coupling end and an engaging member that projects from the coupling end. The rotary member has a track defining an Archimedean spiral. The track is adapted to receive the engaging member. The engaging member is constrained to slide in the track such that linear movement of the elongated member effects rotation of the rotary member. The track may be a slot, a groove, or other guide. Alternatively, instead of a track defined directly in the rotary member, the actuator may include a linking member (such as a disk or rectangular bracket) attached to the rotary member, the linking member having a track defining an Archimedean spiral defined therein, the engaging member being slidable in the track to convert linear motion into rotary motion.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a continuation of my prior application Ser. No. 14/099,186, filed Dec. 6, 2013 now pending. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to mechanical drive mechanisms that convert one type of motion to another, and more particularly, to a linear-to-rotary actuator that uses an Archimedean spiral to convert linear motion of a first member into rotary motion of a second member. 
     2. Description of the Related Art 
     Actuators used to facilitate the transfer of linear motion to rotary motion and/or rotary to linear motion between engaging members can vary in complexity, as well as the prescribed use. Door hinges, scissor trimming, raising lift linkages, and the steering of a wheel are all examples that illustrate interconversion between linear and rotary motion. While many types of linear-to-rotary actuators exist, very few actuators have a universal application that can convert linear motion of a first member into rotary motion of a second member, or vice-versa, in an easy and efficient manner. 
     Another basic example of a type of actuator that translates between linear and rotary motion is a screw fastener. Rotation of the screw head translates to linear movement of the screw. While screw fasteners are widely used in many different mechanical applications, they are not very easy to thread or unthread without the use of specialized tools, such as a screwdriver. 
     Thus, a linear-to-rotary actuator solving the aforementioned problems is desired. 
     SUMMARY OF THE INVENTION 
     The linear-to-rotary actuator includes an elongated drive member constrained to linear movement, and a rotary member constrained to rotary movement. The elongated drive member has a coupling end and an engaging member that projects from the coupling end. The rotary member has a track defining an Archimedean spiral. The track is adapted to receive the engaging member. The engaging member is constrained to slide in the track such that linear movement of the elongated member effects rotation of the rotary member. The track may be a slot, a groove, or other guide. Alternatively, instead of a track defined directly in the rotary member, the actuator may include a linking member (such as a disk or rectangular bracket) attached to the rotary member, the linking member having a track defining an Archimedean spiral defined therein, the engaging member being slidable in the track to convert linear motion into rotary motion. 
     The elongated drive member may be a linear actuator selected from the group consisting of a hydraulic piston and cylinder assembly, a pneumatic piston and cylinder assembly, and an electric linear actuator. Alternatively, the elongated drive member may be a shaft and a gear assembly for driving the shaft. The gear assembly can be selected from the group consisting of a rack and pinion gear assembly and a worm drive gear assembly. Alternatively, the elongated drive member may be an elongated shaft having a threaded end and a support member having an internally threaded bore. The elongated shaft moves linearly when the threaded end is threaded into and out of the bore in the support member. In another alternative, the linear-to-rotary actuator may have a shaft, an electric motor, and a coupler assembly connecting the motor to the shaft. The coupler assembly selectively reciprocates the shaft. The elongated drive member may comprise a part of any mechanism for imparting linear motion to the elongated drive member. 
     The rotary member may comprise a door and hinges adapted for connecting the door to a rigid support member. As such, the door is rotatable on the hinges, and linear movement of the elongated member selectively opens and closes the door. Alternatively, the rotary member may be a pivotally mounted arm, post, disk, wheel, shaft, or any other member that can engage in rotary motion. 
     These and other features of the present invention will become readily apparent upon further review of the following specification and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a chart illustrating an example of an Archimedean spiral. 
         FIG. 1B  is a diagram illustrating construction of a guide curve based upon the principles of an Archimedean spiral. 
         FIG. 2  is an environmental, perspective view of a crane incorporating a linear-to-rotary actuator according to the present invention. 
         FIG. 3  is a partial environmental perspective view of door incorporating a linear-to-rotary actuator according to the present invention. 
         FIG. 4A  is a perspective view of a linear-to-rotary actuator according to the present invention having a pair of rotary members on opposite sides of a linearly movable shaft to provide constant torque. 
         FIG. 4B  is a side view of a disk-type rotary member of the linear-to-rotary actuator of  FIG. 4A . 
         FIG. 4C  is a side view of the disk-type rotary member of  FIG. 4B , shown rotated to the stops of the tracks. 
         FIG. 5  is an exploded view of an embodiment of a linear-to-rotary actuator according to the present invention having dual rotating members with dual slots defining Archimedean spirals to provide constant torque. 
     
    
    
     Similar reference characters denote corresponding features consistently throughout the attached drawings. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The embodiments of a linear-to-rotary actuator described herein provide various mechanical devices utilizing an Archimedean spiral configuration provided on the linear-to-rotary actuator to facilitate selective extension, retraction and rotation of connected members with ease of operation. 
     Referring to the graph shown  FIG. 1A , an Archimedean spiral is characterized by the mathematical formula ρ=αθ, where ρ equals the radius or radial vector from the point of origin O, α equals a constant, and θ is the angle expressed in radians, αθ being in polar coordinates. For any given constant α there is a constant proportional relationship between the change in radial length and the change in angle. In other words, any arbitrary point following the above formula will change in radial length at the same proportional constant rate as that of the angular rotation. As used herein, an Archimedean spiral refers to any curve, or portion of a curve, that complies with the formula ρ=αθ, except as specified below. 
       FIG. 1B  shows an example of an Archimedean curve constructed in accordance with the principles of the above formula. The curve  2  defines the linear movement of a member, which will be further described in relation to the various embodiments described herein. In this example, it is desired to move the member a certain linear distance starting from an arbitrary initial point  3   a  to an end point  3   e  within a desired arc range. The difference between the length of the initial radius ρ 1  and the length of the end radius pρ 5  equals the length of desired linear movement. The intermediate points  3   b ,  3   c ,  3   d  and the intermediate radial lengths ρ 2 , ρ 3 , ρ 4  can be determined by dividing the arc range into equal increments. Joining these points  3   a ,  3   b ,  3   c ,  3   d ,  3   e  provides a good approximation of the shape of the desired curve  2 . Increasing the increments will result in a more accurate curve  2 . 
     Further, the curve  2  can also be approximated by a simple circular curve. As shown in  FIG. 1B , the curve  2  can have the properties of a simple circular curve where the axis or point of origin O C  is offset from the original point of origin O. The radii r 1 , r 2 , r 3 , r 4 , r 5  to each respective point  3   a ,  3   b ,  3   c ,  3   d ,  3   e  on the curve from the offset point of origin O C  are approximately equal to each other. Thus, it can be seen that an Archimedean spiral can also be expressed by a circular curve. The above concepts provide that a relatively smooth and effortless translational curve can be constructed, especially for linear-to-rotary actuators to transfer linear motion to rotary motion for connected mechanical components. 
     The aforementioned principles of Archimedean spirals, represented by example in the guide curve  2  of  FIG. 1B , can be utilized to efficiently and effectively transfer linear motion to rotary motion in several mechanical applications. 
     Referring to  FIG. 2 , there is shown a linear-to-rotary actuator  10  adapted to transfer linear motion into rotary motion in conjunction with a crane. As shown, the actuator  10  includes a first member  12 , or elongated drive member, such as a double-acting hydraulic cylinder and piston assembly  12 , to provide linear motion. The actuator  10  further includes a second member, or arm  16 , adapted for rotary motion, and a linking member or rotary member  14  adapted to transfer linear motion of the first member  12  into rotary motion of the second member  16 . 
     The elongated drive member assembly  12  includes a piston  18 . The elongated drive member  12  is configured to extend and retract the piston  18  linearly in response to pressure applied by the control lines  22  and  23 . As illustrated, the elongated drive member  12  is constrained in a cylinder  25 , which limits the piston  18  to generally linear movement. The elongated drive member  12  further includes a coupling end  20 , which includes a first engaging member  24  and a second engaging member  26 , projecting from the coupling end  20  and adapted for operative engagement with the rotary member  14 . 
     The rotary member  14  rotates in response to linear movement of the elongated drive member  12  and piston  18 . The rotary member  14  operatively engages the elongated drive member  12  and the second member  16 , enabling the transfer of linear motion of the elongated drive member  12  into rotary motion of the second member  16 . As shown, the rotary member  14  is connected to the first member  12  at a central axis  30 . As such, the rotary member  14  rotates about the axis  30 , when the elongated drive member  12  and piston  18  move linearly. 
     As shown, the rotary member  14  has a generally circular configuration conducive for circular rotation about the axis  30 . The rotary member  14  includes a first slot or track  40  defining an Archimedean curve, and adapted to receive the corresponding first engaging member  24  of the elongated drive member  12 . The rotary member  14  further includes a second slot or track  42 , also defining an Archimedean curve, and adapted to receive the corresponding engaging member  26 . 
     Each respective guide slot  40  and  42  is formed in accordance with, or has the curvature defining, an Archimedean spiral, as previously described in  FIG. 1B . Accordingly, upon linear movement of the piston  18  of the elongated drive member  12 , each respective guide  40  and  42  translate linear movement of the respective engaging member  24 ,  26  into rotary movement of the rotary member  14  and the connected second member  16 . 
     In operation, the elongated drive member  12  is activated by the control lines  22  and  23 . As such, hydraulic pressure forces the piston  18  to extend linearly outward from the hydraulic cylinder  12 . As the elongated member  18  moves linearly, the engaging members  24  and  26 , positioned in the corresponding respective guides  40  and  42 , provide a force on the rotary member  14 . As such, the respective engaging members  24 , and  26  slide along the guides  40  and  42 . 
     As the engaging members  24  and  26  cooperatively travel along the Archimedean shaped guides  40 ,  42 , linear forces are applied to the rotary member  14 , thereby rotating the rotary member  14  about the axis  30 , and further cooperatively rotating the connected second member  16 . Linear retraction of the elongated drive member  18  towards the hydraulic cylinder  25  has a reverse effect on the rotary member  14 . As such, linear retraction of the elongated drive member  14  forces the rotary member  14  and connected second member  16  to rotate in an opposite direction. 
     Referring now to  FIG. 3 , there is shown an embodiment of the linear-to-rotary actuator  210  using a slot  240  defining an Archimedean curve to transfer linear motion into rotary motion of a door or window. As shown, the actuator  210  includes a first member  212  or elongated drive member, a linking member  214  having a track or slot  240  formed therein, and a second member  216 , in operative engagement with the joining member  214  and elongated drive member  212 . 
     The elongated drive member  212  can include a gear assembly or coupler assembly  220 . The assembly  220  provides the actuator with a linear driving force. The gear assembly  220  can be a worm drive gear assembly  220 , including an electric linear actuator, having a motor  222  and a shaft  218 . The assembly  220  connects the motor  222  to the shaft  218 , and selectively reciprocates the shaft  218  linearly. 
     As shown, the shaft  218  has a threaded end. The assembly  220  or member  220  has an internally threaded bore for receiving the shaft  218 . The shaft  218  is adapted for linear movement into and out of the internally threaded bore formed in the assembly  220 . Linear movement is applied to the shaft  218 , when the threaded end of the shaft  218  is threaded into and out of the bore formed in the support member  220 . 
     As shown the linking member  214  can be a plate or bracket having a non-circular configuration. The linking member  214  is connected to the second member  216 , which can be a door or window  216 . The linking member  214  further includes a track or slot  240  formed therein defining an Archimedean spiral. As shown the slot  240  is adapted to receive the engaging member  224  of the shaft  218 . As the engaging member  224  is constrained to slide in the slot  240 , linear movement of the shaft  218  can rotate the linking member  214  and connected second member  216 . 
     As illustrated, the second member  216 , which can be a door or window, is further connected to a hinge  226  and frame  228 , enabling the second member  216  to rotate in response to movement of the joining member  214 . 
     In operation, a remote control or user interface can activate the electric motor  222  to force the threaded shaft  218  to move in linearly. As the shaft  218  moves linearly, the engaging member  224  slides along the Archimedean slot  240 . Linear movement of the engaging member  224  within the Archimedean slot  240  forces the linking member  214  to rotate. Accordingly, the member  216 , connected to the plate  214 , is forced to also rotate relative to the frame  228 . 
     With respect to singular rotary members, the driving torque applied on a singular rotary member having an Archimedean spiral varies from the radius change of the rotating angle. The varied torque applied to the member can negatively affect the dynamic application to the linear to actuator. Accordingly it is desirable, when transferring linear motion to rotary motion, that the linear-to-rotary actuator has constant torque. 
     Referring now to  FIGS. 4A-4C , there is shown an embodiment of a linear-to-rotary actuator  310  adapted to provide constant torque during linear-to-rotary motion transfer. The actuator  310  includes a first member  312 , or elongated drive member  312 , a rotary member  314 ,  315 , and a rotary member  316  adapted to transfer rotary motion to an associated member. 
     The elongated drive member  312  can include a cylinder and piston assembly  320 , or pneumatic and piston assembly  320 . As illustrated the piston assembly  320  includes a cylinder and piston  318 . The piston  318  has a coupling end  322 , which includes plural engaging members  324  and  326  configured for operative engagement with the rotary members  314  and  315 . The rotary members  314  and  315  transfer linear motion from the first member  312  into rotary motion of the second member  316 . 
       FIG. 4A  shows the rotary actuator  310 . As shown, the first member  312  can be a cylinder and piston assembly  320 . The piston  318  is adapted for linear reciprocation. The elongated drive member  312  includes plural engaging members  324 , and  326  formed on a coupling end  322  and adapted to cooperatively engage rotary members  314 ,  315  to enable the transfer of linear motion of the piston  318  into rotary motion of the rotary members  314 ,  315 . 
     As illustrated, the rotary member  314  includes dual slots, or tracks  340 ,  342  and the rotary member  315  includes dual slots or tracks  344  and  346  formed therein. The tracks  340 ,  342 ,  344  and  346  define an Archimedean curve, similar to the curve illustrated in  FIG. 1B . The engaging members  324  and  326  each have two opposing ends that project from the piston  318 . As such, the engaging members  324  and  326  provide four insertable members configured for entry into the corresponding Archimedean slots  340 ,  342 ,  344  and  346 . 
     As illustrated in  FIGS. 4B and 4C , the respective Archimedean curves  340  and  342  are symmetrically arrayed about the center of the rotary member  314 . The plural grooves  340 ,  342  balance the torque change to the constant. As such the driving arm or piston  318  when moving in the constant length of linear motion can drive the symmetric Archimedean grooves  340 ,  342  simultaneously and keep the driving torque constant. 
     As shown in  FIG. 4A , the rotary or rotary members  314 , and  315  with an Archimedean groove formed therein can have reverse rotations installed on opposing sides of the engaging members  324  and  326 . It is contemplated that the rotary members  314  and  315  do not be need to be identical. The Archimedean spirals on each side can have different constant in ρ=αθ. They will be matched in motion if and only they follow the same linear motion step with the angular motion different. Notably, it is possible to form the Archimedean slots  340 ,  342  on a single disc 180° or less, and by using dual rotary members  314 ,  315 , the relative angle of change can be doubled to about 360° or less. 
     In operation, the elongated drive member  312  selectively receives hydraulic or pneumatic pressure in the cylinder, and pressure is applied to the piston  318 . The piston  318  is constrained to reciprocate linearly. The engaging members  324  and  326 , in response to movement of the connected piston  318 , move linearly. As such, the engaging members  324  and  326  are constrained to slide along the respective Archimedean slots  340 ,  342 ,  344 , and  346 , so that the rotary members  314 ,  315  rotate. 
     Continuing to  FIG. 5 , an embodiment of a fluid-driven linear-to-rotary actuator  410  is shown for transferring linear motion of a first member  412  or elongated drive member  412  into rotary motion of one or more second members, or rotary members  414 ,  415 . The linear-to-rotary actuator  410  can use hydraulic pressure or pneumatic pressure to provide a driving forced from the linear-to-rotary actuator  410 . As such, it is contemplated that the elongated drive member  412 , of the linear-to-rotary actuator  410  can be a hydraulic piston and cylinder assembly, or a pneumatic piston and cylinder assembly. 
     The elongated drive member  412  includes a cylinder  436 , a piston  418 , operatively connected to the cylinder  436 , and a sleeve  434 . The elongated drive member  412  further includes an extension bar  420  defining a coupling end  420 . The extension bar  420  is connected to the piston  418  and configured for reciprocation within the sleeve  434 . The elongated drive member  212  further includes a plurality of cross pins or engaging members  424  and  426  extending generally outward from the extension bar  420 , and adapted to cooperatively engage the rotary members  414 ,  415 . 
     The sleeve  430  includes a plurality of slots or apertures  432   a ,  432   b  formed therein. The plural slots  432   a ,  432   b  are adapted to receive corresponding plural engaging members  424  and  426  through the sleeve  434 . The slots  432   a  and  432   b  enable linear movement of the engaging members  424  and  426  during operation, and also enable the engaging members  424  and  426  to be operatively engaged with the corresponding rotary members  414  and  415 . 
     The engaging members  424 ,  426  include corresponding rollers  448 , adapted for connection to the ends of the respective engaging members  424 ,  426  to facilitate sliding movement of the engaging members  424 ,  426  during linear engagement with the rotary members  414 ,  415 . 
     As shown, the dual rotary members  415 ,  414  pivotally engage the axis  430  on both respective sides of the elongated driving member  412 . The rotary members  414 ,  415  have a generally circular configuration, and each includes dual tracks, tracks  440 ,  442  for rotary member  414 , and dual tracks  444 ,  446  for rotary member  415  to receive respective engaging members  424  and  426 . The tracks  440 ,  442  and  444 ,  446  each have an Archimedean curve formation to cooperatively provide a balanced and constant driving torque when in rotary motion. As shown, Archimedean tracks  440 ,  442  are formed in opposing directions from tracks  444 , 446  such that torque applied by the rotary members  414  and  415  to the connected members is balanced. 
     In operation, the elongated drive member  412  selectively receives hydraulic or pneumatic pressure in the cylinder  436 . The pressure is applied the piston  418  forcing the piston  418  to reciprocate linearly within the sleeve  434 . The connected extension bar  420 , in response to movement of the piston  418 , moves linearly within sleeve  434 . As such, the engaging member  424  and  426  engage the rotary members  414  and  415 , and are constrained to slide along the respective Archimedean slots  440 ,  442 ,  444 . Accordingly, the rotary members  414 , and  415  rotate about the axis  430  to transfer linear motion into rotary motion. 
     Other embodiments are contemplated with respect to using the Archimedean spiral for linear-to-rotary actuators. For example, with respect to safety applications, a linear-to-rotary actuator may have a block including an Archimedean groove. In such application, a sliding bar has an engaging member provided on an end thereof. As force is provided downward, the engaging member provides a force rotating the block in a downward position. As the sliding bar with spring forces extends upward, a linear force rotates the block upward. 
     In another embodiment, relative rotation angle enlargement for the Archimedean rotator can be used to drive a four-bar linkage system. As such, a pair of identical non-circular shaped rotary members, or Archimedean brackets, are jointly provided on the same sides of the first member or sliding member. As the sliding member with threads are driven by manual crank or motors, the vertical bar with crossed rollers in the identical Archimedean slots will lift up and down the linkages. The relative rotating angles between the upper and lower linkages are doubled as the single Archimedean angle rotated. Moreover, the relative linkage position is automatically self-locked in thread movement. 
     It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.