Abstract:
A stepper motor linear actuator arrangement is formed by casting thermoplastic internal threads within a hollow metal cylinder and arranging the within a hollow metal motor stator.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    Stepper motors are currently available for providing linear motion by means of a so-called “linear actuator” whereby an elongated threaded rod is inserted within the motor during the manufacturing process. 
         [0002]    One example of a manufactured threaded rotor for a linear actuator is found in U.S. Pat. No. 6,774,517 entitled “Injection Molded Threaded Rotor and Manufactured Method”. 
         [0003]    Whereas the rotor, per se, is fabricated and installed during the motor manufacturing process, it would be more economically feasible to manufacture the motor having a hollow rotor whereby the linear actuator could be installed after the motor has been assembled. 
         [0004]    One purpose of the instant invention is to provide an integrated linear actuator arrangement that could be inserted within the motor after the motor has been completely assembled, per se. 
       SUMMARY OF THE INVENTION 
       [0005]    A stepper motor linear actuator arrangement is formed by casting thermoplastic internal threads within a hollow metal cylinder and arranging the cylinder for insertion within a hollow metal motor stator. An extended threaded rod is later inserted within the internal threads to provide linear actuator function. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1A  is a front perspective view of a perforated metal cylinder, which forms the outer surface of the linear actuator according to the invention; 
           [0007]      FIG. 1B  is a front perspective view of the cylinder of  FIG. 1A  after adhering thermoplastic threads to the inner surface thereof; and 
           [0008]      FIG. 2  is a side perspective view of the cylinder of  FIGS. 1A ,  1 B, after insertion within a motor-controller combination. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0009]    As shown in  FIG. 1A , a linear actuator outer cylinder  10  is depicted in the form of a hollow metal cylinder  11  including a plurality of perforations  12 . The cylinder has an outer diameter D 1  of predetermined dimensions for purposes to be described below. 
         [0010]    In accordance with the invention, the outer sleeve  10 , as shown in  FIG. 1B , is arranged within a mold such that an integral inner cylinder  14  is formed therein of a thermoplastic material  15  and defines a plurality of threads, as indicated at  15 A. 
         [0011]    The thermoplastic material also fills the perforations  12  such that the outer sleeve  10  becomes a single entity with the inner cylinder to complete the linear actuator nut assembly  13 . 
         [0012]    As best seen by now referring to  FIG. 2 , a motor controller  16 , such as an IMS M-1713-1.5, including a driver  17  affixed to a stepper motor  18 , is depicted wherein the hollow rotor  19  receives the nut assembly  13  therein. 
         [0013]    The hollow rotor  19  defines a predetermined diameter D 2  which receives the outer sleeve diameter D 1 , shown in  FIG. 1A  in tight-fit relation whereby the elongated threaded shaft  20 , threadingly inserted within the threads  15 A ( FIG. 1 ) contained within the nut assembly  13 B to allow the threaded shaft  20  to rotate in unison with the hollow rotor  19 , when the stepper motor  18  is actuated to perform the linear actuator function. 
         [0014]    When a different size motor  18  is utilized, a different size nut assembly  13  is selected to provide the tight-fit relation without having to form the hollow rotor  19  and nut assembly  13  as a single entity as described within the prior art. 
         [0015]    Accordingly, an integral linear actuator nut assembly has been described herein for tight-fit insertion within a hollow stepper motor rotor, without having to form the rotor and nut assembly as a single unit per se.