Abstract:
A lead screw attachment mechanism for a linear actuator system is provided. The attachment mechanism comprises an attachment housing comprising a fixed cover configured to house the attachment mechanism. The attachment mechanism comprises a first coupling mechanism configured to couple the attachment mechanism to an output shaft of a motor and a second coupling mechanism configured to couple the attachment mechanism to a lead nut, wherein the lead nut is configured to move linearly along an axis defined by a length of the attachment mechanism. The attachment mechanism is configured to rotate about the axis, within the fixed cover.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is a continuation of and claims priority to U.S. patent application Ser. No. 14/301,557, filed Jun. 11, 2014, which is a continuation of Ser. No. 13/655,883, filed Oct. 19, 2012, the contents of which are hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     A servo motor (a.k.a. simply a “servo”) is a device having a rotatable output shaft. The output shaft can typically be positioned to specific angular positions in accordance with a coded signal received by the servo. It is common that a particular angular position will be maintained as long as a corresponding coded signal exists on an input line. If the coded signal changes, the angular position of the shaft will change accordingly. Control circuits and a potentiometer are typically included within the servo motor casing and are functionally connected to the output shaft. Through the potentiometer (e.g. a variable resistor), the control circuitry is able to monitor the angle of the output shaft. If the shaft is at the correct angle, the motor actuates no further changes. If the shaft is not at the correct angle, the motor is actuated in an appropriate direction until the angle is correct. 
     There are different types of servos that include output shafts having varying rotational and torque capabilities. For example, the rotational and/or torque capability of an industrial servo is typically less restricted than that of a hobby servo. That being said, hobby servos are generally available commercially at a cost that is much less than that associated with industrial servos. 
     Because hobby servos are relatively small and inexpensive, they are popular within the hobby-mechanical industry for applications such as, but by no means limited to, hobby robotic applications and radio-controlled models (cars, planes, boats, etc.). One example of a hobby servo is the Futaba S-148 available from Futaba Corporation of America located in Schaumburg, Ill. 
     SUMMARY 
     A lead screw attachment mechanism for a linear actuator system is provided. The attachment mechanism comprises an attachment housing comprising a fixed cover configured to house the attachment mechanism. The attachment mechanism comprises a first coupling mechanism configured to couple the attachment mechanism to an output shaft of a motor and a second coupling mechanism configured to couple the attachment mechanism to a lead nut, wherein the lead nut is configured to move linearly along an axis defined by a length of the attachment mechanism. The attachment mechanism is configured to rotate about the axis, within the fixed cover. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic drawing of a linear actuator system with a lead nut. 
         FIG. 2  is a schematic drawing of a linear actuator system with a sliding tube and a fixed cover. 
         FIG. 3  is a perspective view of a multiple motor drive mechanism with an outer casing removed to show the multiple motors. 
         FIG. 4  is a perspective view of a multiple motor drive mechanism with an outer casing. 
         FIGS. 5-1, 5-2, and 5-3  are perspective views of a hobby servo motor. 
         FIG. 6  is a side view of a lead screw attachment mechanism that includes an outer surface having multiple different types of threading. 
         FIG. 7  is a side view that shows internal components of the lead screw attachment mechanism shown in  FIG. 6 . 
         FIG. 8  is a perspective view of a lead screw attachment mechanism attached to a hobby servo motor. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a schematic drawing of one example of a linear actuator system  100 . System  100  optionally includes a motor  102 , a lead screw attachment mechanism  106 , a lead nut  108 , and a feedback mechanism  110 . Motor  102  illustratively has a rotatable output shaft  104 , and motor  102  may be part of either an open-loop system or a closed-loop system. In an open-loop system, the position, direction of rotation, and/or speed of rotation of output shaft  104  are based on an operator input  114  without any feedback. In a closed-loop system, the position, direction of rotation, and/or speed of rotation of output shaft  104  are based on both an operator input  114  and feedback  112  from feedback mechanism  110 . 
     The output shaft  104  illustratively has a number of splined features, and the attachment mechanism  106  has an inner surface  116  that is configured to functionally engage the splined features such that rotation of output shaft  104  is transferred to attachment mechanism  106 . Accordingly, output shaft  104  and attachment mechanism  106  are in-line with each other and rotate about a same axis of rotation  118 . 
     In an embodiment, the outer surface of attachment mechanism  106  has multiple different textured surfaces. For example, the outer surface of attachment mechanism  106  may have two or more threaded surface. In the particular example shown in  FIG. 1 , attachment mechanism  106  has a lower threaded section  120  and an upper threaded section  122 . The lower section  120  may have gear-teeth type threading, and upper section  122  may have screw type threading. In other embodiments, only one of sections  120  or  122  may have threading, and the other section has a smooth outer surface. Embodiments are not however limited to any configuration. 
     Lead nut  108  illustratively has an inner surface  124  that has threading that corresponds to the threading of upper section  122 . For instance, inner surface  124  may have screw type threading that enables lead nut  108  to be able to move up and down along lead screw attachment mechanism  106  in a screw and nut type fashion. In one embodiment, lead nut  108  is prevented from rotating while lead screw attachment  106  is rotated. This results in lead nut  108  moving up and down along the attachment mechanism  106  in the directions shown by arrow  128 . Accordingly, system  100  is able to turn rotational movement  126  of lead screw attachment mechanism  106  into linear motion  128  of the lead nut  108 . 
     In some, but not all embodiments, feedback mechanism  110  is rotatably connected to surface  120  of attachment mechanism  106  such that rotation of mechanism  106  is directly translated to rotation  130  of mechanism  110  about axis of rotation  132 . Axis  132  is optionally parallel to axis of rotation  118  of mechanism  106 . The rotation may be translated through gear teeth on the outer surface of feedback mechanism  110  that correspond to gear teeth on the surface  120 . In one example of such an embodiment, feedback mechanism  110  comprises a potentiometer. In other embodiments, feedback mechanism  110  comprises an encoder such as, but not limited to, a magnetic encoder, an optical encoder, a rotary encoder, or a linear encoder. 
       FIG. 2  is a schematic drawing of another example of a linear actuator system  200 . System  200  optionally includes a motor  202  (e.g. a hobby servo motor), a lead screw attachment mechanism  206 , a lead nut  208 , a fixed cover  252 , and a sliding tube  254 . The lead screw attachment mechanism  206  optionally includes a threaded lower section  220  and a threaded upper section  222 . 
     In an embodiment, lead screw attachment mechanism  206  is rotated about an axis of rotation  218  by an output shaft of motor  202 . The lead nut  208  is prevented from rotating by the fixed cover  252  and the sliding tube  254 . Fixed cover  252  is illustratively stationary (i.e. does not move relative to motor  202 ). Sliding tube  254  is able to move in the linear directions  228 , but is not able to rotate about axis  218 . Accordingly, as mechanism  206  is rotated, lead nut  208  and the attached sliding tube  254  are able to move up and down in the linear directions shown by arrows  228 . 
     System  200  may be either a closed-loop system or an open-loop system. In the case of a closed-loop system, system  200  may include a feedback mechanism in a number of different places. In one embodiment, feedback mechanism  210  is configured such that it does not move linearly with lead nut  208 . For instance, feedback mechanism  210  may include a potentiometer or encoder that is rotated by the lower threaded section  220 . In another embodiment, feedback mechanism  211  is configured such that it does move linearly with lead nut  208 . For instance, feedback mechanism  211  may include an optical or magnetic sensor that determines its position relative to fixed cover  252 . Furthermore, in yet another embodiment, a feedback mechanism  212  may be included within motor  202  (e.g. within a casing of motor  202 ) such that it is not exposed to other components, and perhaps provides a cleaner appearance. Embodiments are not limited to any particular configuration and can include any number of feedback mechanisms including none in the case of an open-loop system. 
       FIG. 3  shows a perspective view of a multi-motor drive mechanism  300 . In certain embodiments of the present disclosure, a multi-motor drive mechanism  300  is used to rotate a lead screw attachment mechanism (e.g. mechanism  106  in  FIG. 1  or mechanism  206  in  FIG. 2 ). In other words, the motor  102  in  FIG. 1  and motor  202  in  FIG. 2  do not necessarily need to be single motor systems. Instead, the motors in those figures can be replaced with a multi-motor drive mechanism. Additionally, multi-motor drive mechanisms can be used by themselves without being incorporated in a linear actuator system. 
     Multi-motor drive mechanism  300  in  FIG. 3  illustratively includes two motors (e.g. two hobby servo motors)  301  and  302 . Embodiments are not however limited to any specific number of motors and can include more than the illustrated two (e.g. 3, 4, 5, 6, etc.). The two motors are secured within a mounting bracket  304 . Bracket  304  optionally includes two apertures  306  and  308  that are configured to receive motors  301 / 302  and secure them to the bracket  304 . 
     Bracket  304  is also configured to support a rotatably mounted gear  310 . Gear  310  is functionally engaged with two gears  312  and  314 . Gears  312  and  314  are illustratively configured to fit around a splined output shaft of motors  301  and  302 . However, in another embodiment, system  300  does not include gears  312  and  314 , and instead the output shafts of motors  301  and  302  are used directly to rotate gear  310 . 
     In one embodiment, gears  312  and  314  have smaller outer circumferences (i.e. smaller diameters) than gear  310 . In such a configuration, gear  310  is able to provide a greater amount of torque than could motors  301  and  302  by themselves. Embodiments are again not limited to any particular configuration, and gears  310 ,  312 , and  314  could have different relative sizes. 
     Gear  310  is illustratively attached to an attachment hub  316  that directly translates rotation from gear  310 . Hub  316  includes a center aperture  317  that is surrounded by a number of satellite apertures  318 . Center aperture  317  may be the same size, larger, or smaller than satellite apertures  318 . This may be beneficial in that it provides many different options for attaching other components to hub  316 . For instance, a same or similar center and satellite aperture pattern can be repeated on other components such that all of the components can be connected together. Furthermore, bracket  304  may include one or more attachment posts  320  that can be used to secure the components shown in  FIG. 3  within an outer casing. 
       FIG. 4  shows a perspective view of a multi-motor drive mechanism within a casing  300 . The casing includes a bottom portion  352  and a top portion  354 . Portions  352  and  354  illustratively support and protect the components shown in  FIG. 3  (e.g. the motors  301 / 302 , gears  310 / 312 / 314 , etc.). In an embodiment, top casing portion  354  includes a number of apertures and securing mechanisms (e.g. screws) that are used to secure the mounting bracket  304  and/or posts  320  shown in  FIG. 3  to the outer casing. The top casing portion  354  may also include a number of apertures  358  that can be used to secure the multi-motor drive mechanism  300  within an operating environment.  FIG. 4  further shows that system  300  may include one group of wires  360  that are used to provide control signals, power, etc. to the components within system  300  (e.g. motors  301  and  302 ). 
       FIG. 5-1  is a perspective view of a hobby servo motor  500 , and  FIG. 5-2  is a side view of hobby servo motor  500 . In an embodiment, servo motor  500  includes a feedback mechanism (e.g. feedback  110  in  FIG. 1 ) and is a motor such as motor  102  in  FIG. 1 . Servo  500  includes attachment flanges  504 . Flanges  504  optionally include apertures  505  formed therein for receiving an attachment mechanism (e.g., a screw, bolt, etc). The attachment mechanism is illustratively utilized to secure servo  500  within an operative environment. Servo  500  also includes an electrical connection  506  that enables the servo to receive electrical power and/or control signals. 
     Servo  500  includes a rotatable output shaft  502  also known as a servo spline or a servo splined output shaft. Shaft  502  optionally has an outer perimeter or periphery that has splines or teeth. It is common for shaft  502  to have a 23, 24 or 25 tooth configuration. 
     Output shaft  502  is positioned to specific angular positions in accordance with a coded input signal received by the servo. It is common that a particular angular position will be maintained as long as a corresponding coded signal exists on an input line. If the coded signal changes, the angular position of the servo output shaft  502  will change accordingly. 
     In an embodiment, output shaft  502  includes a threaded orifice  522 . Threaded orifice  522  extends into splined output shaft  502  from its distal end. Orifice  522  is illustratively used to secure an item such as a gear, horn, or other attachment mechanism to shaft  502 . Servo  500  further includes a planar or relatively planar surface  521  that surrounds shaft  502 . In accordance with one aspect of the present disclosure, gears, horn, and attachment mechanisms that are attached to, rotatably coupled to, or functionally engaged to shaft  502  also include a planar or relatively planar surface. In such an embodiment, a surface of the item being attached and surface  521  are engaged to one another in a relatively flush relationship. 
       FIG. 5-3  is a perspective view of hobby servo motor  500  showing an internal potentiometer  552  and control circuit  550  removed from the hobby servo housing or casing. Control circuit or circuits such as circuit  550  and an internal potentiometer such as potentiometer  552  are commonly included within the housing or casing of a hobby servo motor. The control circuitry and potentiometer are functionally connected to the hobby servo motor rotatable output shaft. Through the potentiometer (e.g., a variable resistor), the control circuitry is able to monitor the angle of the output shaft. If the shaft is at the correct angle, the motor actuates no further changes. If the shaft is not at the correct angle, the motor is actuated in an appropriate direction until the angle is correct. In an embodiment, internal potentiometer  552  is replaced with a feedback mechanism (e.g. mechanism  110  in  FIG. 1 ). In at least certain circumstances, the new feedback mechanism includes an internal encoder that enables output shaft  522  to perform multiple rotations (e.g. 720 degrees, 1080 degrees, etc.). Additionally, it should be mentioned that in certain embodiments, motor  500  comes preconfigured with an internal encoder and does not need to be modified. 
     Rotation of a servo output shaft such as shaft  502  is typically limited to around 180 degrees. In most cases, rotation is limited at least because of an internal mechanical stop. It is also common that servo output shaft  502  is capable of producing a relatively limited amount of torque power. The torque and rotational limitations of a hobby servo are adequate for many applications; however, some applications require a servo having torque power and/or a rotational capacity that is beyond the capability of a typical hobby servo. Increased torque power and/or rotational capacity enable greater mechanical flexibility. 
     In accordance with one embodiment of the present disclosure, hobby servo motors such as servo  500  are internally modified to enable a range of output shaft rotation that is greater than its “off-the-shelf” capability. For example, in accordance with one embodiment, an internal mechanical stopping mechanism, which prevents rotation past a predetermined angle, is removed from hobby servo motor to enable for continuous rotation in either direction. As a result of the modification, the rotatable output shaft of a hacked or modified servo is able to rotate beyond the range of rotation prior to the modification. 
     Following modification of servo  500 , limitations inherent to the internal potentiometer make it a poor choice for subsequent control functionality. As previously mentioned, in a normal servo operating configuration, the servo motor rotates the servo output shaft corresponding to the coded signal received by the servo. The output shaft is rotated until the signal from the internal potentiometer of the servo, which corresponds to the angular position of the servo output shaft, matches the coded signal received by the servo. Most hobby servos contain internal potentiometers such as potentiometer  552  shown in  FIG. 5-3  that are physically limited to monitoring a limited range of angles (e.g., often less than 200 degrees). Therefore, when a servo  500  is modified for extended rotation, the internal potentiometer is not the best control component for applications that require the servo shaft to rotate beyond the typical rotation limits in order to provide improved rotational capacity. The internal potentiometer is not likely to support control of a range of rotation that is even equivalent to the original rotational range of the servo output shaft. 
     In accordance with one aspect of the present disclosure, the internal potentiometer is disconnected and an external/auxiliary potentiometer is inserted into the control scheme to facilitate proportional control of the servo splined output shaft. Alternatively or in addition, the internal potentiometer is optionally replaced with a feedback mechanism (e.g. mechanism  110  in  FIG. 1 ). In an embodiment, servo  500  utilizes the coded input signal and the signal from an external potentiometer to rotate and position the output shaft. A particular external potentiometer having any of a variety of control characteristics can be selected and implemented based on the requirements of a given application. Therefore, a potentiometer with a rotational range of substantially less than or greater than 180 degrees can be selected and implemented as desired. 
       FIG. 6  is a side view of a lead screw attachment mechanism  606 . Attachment mechanism  606  illustratively includes a top surface  602 , a bottom surface  604 , and an output shaft attachment housing 1308. Additionally, mechanism  606  optionally includes two or more different surfaces along the rotatable shaft. In the embodiment shown in  FIG. 6 , mechanism  606  includes a first threaded surface  620  and a second threaded surface  622 . First threaded surface  620  may for instance include screw, worm screw, gear, or any other type of threading. Second surface  622  may also illustratively include screw, gear, or any other type of threading. In one embodiment, first and second threaded surfaces  620  and  622  include different types of threading (e.g. one includes screw threading and the other gear threading), or alternatively, both surfaces  620  and  622  may include the same type of threading. In another embodiment, one or more of surfaces  620  or  622  may instead include a non-textured surface (e.g. a smooth outer surface such as that shown in  FIG. 8 ). Additionally, embodiments of mechanism  606  are not limited to only including two surfaces along the rotatable shaft. Embodiments of mechanism  606  optionally include any number of surfaces along the rotatable shaft. For instance, mechanism  606  may include three different surfaces instead of the two shown in  FIG. 6  with one surface having screw threading, one gear threading, and the other surface being smooth. 
       FIG. 7  is a side view of lead screw attachment mechanism  606  that highlights internal features with dotted lines. Mechanism  606  includes top surface  602 , attachment mechanism orifice  610 , attachment surface  607 , output shaft attachment housing  608 , top receiving surface  614 , spline receiving surface  612 , and bottom surface  604 . Embodiments of mechanism  606  include any desired dimensions. Embodiments of mechanism  606  are made from every material. Examples of materials include rigid materials such as 6061 T6 aluminum. 
       FIG. 8  is a perspective view of an embodiment of a lead screw attachment mechanism  806  attached to an exemplary hobby servo  802 . The particular embodiment of mechanism  806  includes a smooth outer surface  800 . In other embodiments, outer surface  800  includes one or more textured portions as is shown in the previous drawings. Mechanism  806  is securely and functionally engaged to a motor rotatable output shaft, and mechanism  806  bottom surfaces  604  and/or  652  (shown and labeled in  FIG. 7 ) are flushly engaged with a circular planar surface of the motor. In an embodiment, mechanism  806  is securely attached to hobby servo  802  using screw  804 . In other embodiments, attachment mechanisms other than screws are used. The attachment of mechanism  806  to hobby servo  802  provides many useful features. Mechanism  806  provides enhanced performance such as increased strength and durability. Mechanism  806  supports greater side-loads on the servo than the servo could support alone. Mechanism  806  also allows for items that cannot be directly attached to a hobby servo to be indirectly attached. 
     Finally, it is to be understood that even though numerous characteristics and advantages of various embodiments have been set forth in the foregoing description, together with details of the structure and function of various embodiments, this detailed description is illustrative only, and changes may be made in detail, especially in matters of structure and arrangements of parts within the principles of the present disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. In addition, although the embodiments described herein are directed to hobby servo motors, it will be appreciated by those skilled in the art that the teachings of the disclosure can be applied to other types of components, without departing from the scope and spirit of the disclosure. Also, it should be noted that embodiments of the present disclosure illustratively include any one or more features described in this specification or shown in the figures.