Abstract:
An overload protection device using a rotatable arm rotatably connected to a driving wheel and a resilient member connecting the rotatable arm with the driving wheel for transmitting the torque outputted by a motor to the driving wheel, the resilient member is obviously deformed when the motor is operated in a overload condition to detach the rotatable arm from the motor for protecting the motor from the overload condition.

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates to overload protection devices and, particularly, to an overload protection device for a motor. 
     2. Description of Related Art 
     Generally, a circuit for driving an electric motor usually employs a fuse. The fuse breaks when the electric motor overloads to protect the electric motor from damages. However, after each time the fuse breaks, to restore the circuit, the fuse needs to be replaced. This is an inconvenient and very time-consuming. 
     Therefore, it is desirable to provide an overload protection device which can overcome the above-mentioned problems. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURE 
         FIG. 1  is an exploded, isometric view of an exemplary embodiment of an overload protection device. 
         FIG. 2  is an assembled, isometric view of the overload protection device of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , an overload protection device  2 , according to an exemplary embodiment, is illustrated. The overload protection device  2  includes a transmitting shaft  22  driven by a motor  20 , a driving wheel  24 , and a transmitting mechanism  26 . 
     The motor  20  includes a rotor  200  and a first gear  202  formed on the distal end of the rotor  200 . The motor  20  works normally when supplied with power lower than a rated power. Once the power exceeds the rated power, the motor  20  becomes overloaded. 
     The transmitting shaft  22  is a cylindrical rod and includes a first connecting end  220 , a meshing end  222 , a cylindrical surface  224 , a driving arm  226  radially extending outwards from the cylindrical surface  224 , and a second gear  222   a  formed on the meshing end  222 . The driving arm  226  includes a connecting portion  226   a  and a forcing portion  226   b . The connecting portion  226   a  is an elongated rectangular plate and substantially extends outwards radially from the cylindrical surface  224  near the first connecting end  220 . The forcing portion  226   b  substantially extends from the distal end of the connecting portion  226   a  towards the first connecting end  220  of the rotor  22 . 
     The driving wheel  24  is substantially a circular plate and includes an inner sidewall  240  and a fixing member  246 . The driving wheel  21  also defines a center hole  242  in the center of the inner sidewall  240  and a connecting hole  244  (e.g., a threaded hole) in the inner sidewall  240  adjacent to the periphery of the inner sidewall  240 . The fixing member  246  is a cylindrical protrusion perpendicularly extending outwards from the inner sidewall  240  at a predetermined distance away from the center hole  242  and the connecting hole  244 . 
     The transmitting mechanism  26  includes a rotatable arm  260 , a resilient member  262 , a connecting ring  264 , and a screw  266 . The rotatable arm  260  includes a free end  260   a  and a second connecting end  260   b  and defines a through hole  260   c  in the middle. The connecting ring  264  defines an assembly hole  264   a  in the center. The screw  266  includes a threaded body  266   a  and a positioning head  266   b.    
     The resilient member  262  deforms (e.g., stretches) when a tensile force applied on the resilient member  262  is larger than a critical tensile force, but remains substantially unchanged when the tensile force is smaller than the critical tensile force. In this embodiment, the resilient member  262  can be a helical spring. 
     Referring to  FIG. 2 , in assembly, the transmitting shaft  22  is rotatably connected to the driving wheel  24  via rotatably inserting the first connecting end  220  into the center hole  242 . The transmitting shaft  22  is engaged with the motor  20  by meshing the second teethed section  222   a  with the first gear  202 . The rotation arm  26  is rotatably connected to the driving wheel  24  by inserting the threaded end  266   a  of the screw  266  through the through hole  260   c  of the rotatable arm  26  and screwing the screw  266  into the connecting hole  244 . The connecting ring  264  is fixed on the fixing member  246  of the driving wheel  24 . The resilient member  262  is connected between the second connecting end  260   b  of the rotatable arm  26  and the connecting ring  264 . 
     In use, the motor  10  drives the transmitting shaft  22  to rotate via the first gear  202  and the second teethed section  222   a . The driving arm  226  rotates following the transmitting shaft  22  and presses against the free end  260   a  of the rotatable arm  260  via the forcing portion  226   b . The rotatable arm  260  rotates about the screw  266  and applies a tensile force on one distal end of the resilient member  262  if the tensile force is smaller than critical tensile force. The resilient member  262  drives the driving wheel  24  to rotate via the other distal end. Therefore, the torque generated by the motor  20  is transmitted to the driving wheel  24 . In this case, the absolute value of the torque outputted by the motor  10  is substantially equal to the absolute value of the torque applied on the driving wheel  24  by the resilient member  262 . 
     If the motor  10  becomes overloaded, the tensile force applied on the resilient member  262  is larger than the critical tensile force. Thus, the resilient member  262  would stretch to a greater degree, the rotatable arm  26  rotates about the screw  266  and, the forcing portion  226   b  separates from the free end  260   a  of the rotatable arm  26 . As a result, the transmitting shaft  22  would rotate freely, decreasing the load of the motor and protecting the motor  10  from damage caused/due to overloading. 
     While various exemplary and preferred embodiments have been described, it is to be understood that the invention is not limited thereto. To the contrary, various modifications and similar arrangements (as would be apparent to those skilled in the art) are intended to also be covered. Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.