Patent Publication Number: US-2011072927-A1

Title: Method and apparatus for attachment of a lead screw to a motor shaft

Description:
BACKGROUND OF THE INVENTION 
     Methods are currently available for converting a motor rotation to a bi-directional linear motion wherein a complex interface is interconnected with the motor shaft to provide the linear movement. 
     Two early arrangements are described within U.S. Pat. No. 3,641,828 entitled “Rotary-Linear Motion Converter” and within U.S. Pat. No. 4,324,148 entitled “Rotary/Linear Motion Converter Assembly”. 
     A more recent arrangement for converting motor rotation is the use of a linear actuator whereby a lead screw is connected with the motor shaft during the motor manufacture, per se. 
     One example of a lead screw for a linear actuator is described within U.S. Pat. No. 7,086,303 entitled “Lead Screw for Linear Actuator and Method of Manufacturing Same”. 
     U.S. Pat. No. 6,422,101 entitled “Reinforced Lead Screw with Springless Ani-Backlash Nut” and U.S. Pat. No. 7,552,657 entitled “Long-Span Lead Screw Assembly with Anti-Backlash Nut” describe the arrangement of the lead screw relative to a motor rotor. 
     Whereas the lead screws currently employed require supplemental means for coupling to the motor shaft, or specific assembly during the motor manufacture, it would be more convenient and economically feasible to attach the lead screw directly to a motor shaft after motor manufacture, per se. 
     One purpose of the instant invention, accordingly, is to provide an integrated linear actuator arrangement that could be attached to the motor shaft after the motor has been completely assembled. 
     SUMMARY OF THE INVENTION 
     A linear actuator arrangement consists of an extended lead screw terminating at one end via a conical section and a threaded rod. A conical aperture within one end of a customized rotor shaft abuts a threaded aperture formed therein.
     After completion of the motor assembly including the customized rotor shaft, the threaded rod at the end of the lead screw is later fastened within the threaded aperture to provide linear actuator function.   

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view the customized lead screw according to the invention; 
         FIG. 2  is sectional side view of a motor shaft customized for threadingly receiving the lead screw of  FIG. 1 ; and 
         FIG. 3  is a side view, in partial section, of the customized lead screw of  FIG. 1  inserted within a motor shaft of  FIG. 2  to complete the linear actuator assembly. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As shown in  FIG. 1 , a lead screw  10  is depicted in the form of a first threaded metal rod  11  similar to that described within the aforementioned U.S. Pat. No. 7,086,303 and differs therefrom by inclusion of a conical section  12  terminating in a second diameter threaded metal rod  13  of smaller diameter than the first threaded metal rod  11 . 
     In further accordance with the invention, as shown in  FIG. 2 , a customized motor shaft  14  defining a rotor support rod  15 , which includes a pair of bearing journals  16 A,  16 B, on the exterior surface thereof and a cone-shaped aperture  17  at one end leading to a threaded circular aperture  18  and a non-threaded circular aperture  19 . A shaft  20  extends from the opposite end of the motor support rod  15  for function within a stepper motor assembly as described within U.S. Pat. No. 6,967,425 entitled “Multi-functional Electric Stepper Motor Assembly Having Increased Motor Torque”. 
     The combined rotor shaft-lead screw assembly  21  is now depicted in 
       FIG. 3  with the threaded metal rod  13  engaged within the threaded circular aperture  18  such that the conical section  12  sits within the cone-shaped aperture  17  and the threaded metal rod  11  on the lead screw  10  extends therefrom the rotor shaft  14 . 
     Although the attachment of the lead screw  10  to the rotor shaft  14  is shown prior to completion of the stepper motor, this is for purposes of clarity. In actuality, the rotor shaft  14  is part of the complete stepper motor assembly (not shown) and the lead screw  10  is assembled therein after such assembly.
     This allows lead screws of various lengths and configurations to be assembled to a stepper motor without having to design each stepper motor for each lead screw, per se, which is an important feature of the invention.   

     A linear actuator arrangement has herein been described whereby a simple adjustment to the rotor shaft of a stepper motor and the like is adjusted to receive a plurality of sized lead screws without having to design and adjust each and every stepper motor to accommodate each and every sized lead screw, as described earlier.