Abstract:
The front brake of an electric motor has mechanical structure and is fitted on the output spindle at the front end of the electric motor, able to diminish the dimensions of an electric motor and save cost, and having no problem pertaining to circuit control and power compatibility in case of maintenance.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to the front brake of an electric motor, particularly to one having a simple mechanical structure to effectively control an electric motor and able to save cost. 
     2. Description of the Prior Art 
     A conventional electric motor  1  having function of braking and speed reducing, as shown in FIG. 1, is installed with an electromagnetic brake  2  at the rear side to control its shaft to carry out braking. That the electromagnetic brake  2  is installed at the rear side of the conventional electric motor  1  is mainly because the electric motor  1  has its front side provided with a speed-reducing device  3  to lower the speed and heighten the torsion of the output power of the electric motor  1  to let the spindle  4  at the front side of the electric motor  1  able to output a comparatively great power to drive the mechanical equipment connected with it. Under such a condition, after the speed-reducing device  3  carries out speed reduction, the spindle  4  will produce a torsion which is too huge to be braked by the electromagnetic brake  2 ; therefore the conventional electric motor  1  must have its electromagnetic brake  2  installed at the rear side so as to brake the shaft directly, thus increasing dimensions of the electric motor  1  and taking much space. 
     SUMMARY OF THE INVENTION 
     The objective of the invention is to offer a front brake of an electric motor, having mechanical structure and connected with an output spindle at the front end of an electric motor, diminishing the dimensions of an electric motor and saving cost and also having no problem involving circuit and electric source in maintenance. 
     Besides, the electromagnetic brake  2  of the conventional electric motor  1  is supplied with direct current for carrying out operation, but for the present almost all the factories and families are supplied with alternating current for use; therefore the electromagnetic brake  2  has to be additionally provided inside with a rectifier to convert alternating current into direct current and a control circuit, thus complicating its structure and increasing cost. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     This invention will be better understood by referring to the accompanying drawings, wherein: 
     FIG. 1 is a perspective view of a conventional electric motor: 
     FIG. 2 is an exploded perspective view of a first preferred embodiment of the front brake of an electric motor in the present invention: 
     FIG. 3 is a cross-sectional view of the first preferred embodiment of the front brake of an electric motor in the present invention: 
     FIG. 4 is a side cross-sectional view of the first preferred embodiment of the front brake of an electric motor in the present invention: 
     FIG. 5 is a side cross-sectional view of the first preferred embodiment of the front brake of an electric motor in the present invention, showing the spring constricted inward: 
     FIG. 6 is a side cross-sectional view of the first preferred embodiment of the front brake of an electric motor in the present invention, showing the spring expanded outward: 
     FIG. 7 is a perspective view of the first preferred embodiment of the front brake of an electric motor applied for pulling up a curtain in the present invention: 
     FIG. 8 is a front view of a second preferred embodiment of the front brake of an electric motor in the present invention: 
     FIG. 9 is a front view of a third preferred embodiment of the front brake of an electric motor in the present invention: 
     FIG. 10 is an exploded perspective view of a fourth preferred embodiment of the front brake of an electric motor in the present invention: and 
     FIG. 11 is an exploded perspective view of a fifth preferred embodiment of the front brake of an electric motor in the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A first preferred embodiment of the front brake of an electric motor in the present invention, as shown in FIGS. 2 and 3, includes an electric motor  10 , a shaft coupling rotary disc  20  and a brake  30  as main components combined together. 
     The electric motor  10  has a speed-reducing device  101  assembled at the front side, and the speed-reducing device  101  is provided with a power output spindle  11  extending outward at the front end for output of power and having its outer circumference fitted with a sleeve  12 . 
     The shaft coupling rotary disc  20  has its outer circumferential edge provided with a plurality of engage members  21  extending forward and spaced apart equidistantly. The shaft coupling rotary disc  20  further has a recessed groove  22  and a through shaft hole  23  axially bored in the center. The shaft hole  23  and the spindle  11  have the same shape and are united with each other to rotate together. 
     The brake  30 , as shown in FIG. 4, includes a base  31 , a drive rod  32  and a controlling rotary member  33  combined together. 
     The base  31  shaped a hollow pillar has a round base hole  311  axially bored in the center for receiving a torsion spring  312  therein. The torsion spring  312  has two ends respectively bent inward to form an actuating member  313 . Further, the base hole  311  of the base  31  has its opposite sides respectively covered by a sealing cover  314  having an axial insert hole  315  in the center. 
     The drive rod  32  shaped as an elongate column is positioned inside the torsion spring  312  after having its front inserted through the pivotal insert hole  315  of the front sealing cover  314 . The drive rod  32  is provided with a protruding drive member  321  on a central portion to push against the outer side of the actuating member  313  of the torsion spring  312 . 
     The controlling rotary member  33  is axially bored with a pivotal shaft hole  331  in the center and has its rear circumference formed with a serrated portion  332  to be engaged with the engage members  21  of the shaft coupling rotary disc  20 . The front portion of the controlling rotary member  33  to be inserted in the base hole  311  of the base  31  has its opposite side edges respectively and symmetrically formed with an interacting surface  333  to push against the inner side of the actuating member  313  of the torsion spring  312 . The drive rod  32  is pivotally inserted through the pivotal shaft hole  331  of the controlling rotary member  33  and has its drive member  321  protruding out of the pivotal shaft hole  331 . 
     In assembling, as shown in FIG. 3, the shaft coupling rotary disc  20  is fitted with the front side of the electric motor  10 , letting the spindle  11  inserted through the shaft hole  23  of the shaft coupling rotary disc  20 . Then, the engage members  21  of the shaft coupling rotary disc  20  are engaged with the serrated portion  332  of the controlling rotary member  33  to assemble the shaft coupling rotary disc  20  together with the brake  30 . 
     In using, as shown in FIG. 7, if the electric motor  10  of this invention is to be installed with a moving-up and-down curtain unit  40 , the base  3   1  in front of the electric motor  10  is fitted in the rail frame  41  of the curtain unit  40  and connected to the rolling shaft  44  of the curtain unit  40  by means of a connecting sleeve  42  and a connecting rod  43 , letting the drive rod  32  connected with the rolling shaft  44  of the elevating curtain  40  so as to actuate the curtain unit  40  to move up and down. 
     In operating, as shown in FIG. 5, when the electric motor  10  is started and the spindle  11  begins to rotate, the spindle  11  will actuate the interacting surfaces  333  of the controlling rotary member  33  to rotate clockwise or counterclockwise. When the interacting surfaces  333  of the controlling rotary member  33  is rotated to push against the inner side of one actuating member  313  of the torsion spring  312 , the torsion spring  312  will be forced to constrict inward and separate from the inner circumferential edge of the base hole  311  of the base  31 , letting the torsion spring  312  lose its expanding resilience. At this time, the controlling rotary member  33  will actuate the drive rod  32  to rotate together with the connecting rod  43  and the rolling shaft  44  of the curtain unit  40  to enable the curtain body  45  to move up and down. On the contrary, as shown in FIG. 6, when the electric motor  10  stops rotating, the curtain body  45  will hang down due to its own gravity and actuate the rolling shaft  44 , the connecting rod  43 , the connecting sleeve  42  and the drive rod  32  to rotate. At this time, the drive member  321  of the drive rod  32  will push the outer side of one actuating member  313  of the torsion spring  312  and force the torsion spring  312  to expand outward and closely push against the inner wall of the base bole  311  of the base  31  to form a braking function, letting the controlling rotary member  33  and the drive rod  32  as well as the connecting rod  43  stop rotating and the curtain body  45  impossible to move downward. 
     Thus, the power driven by the electric motor  10  can be controlled to actuate the curtain body  45  to move up and down by constricting the torsion spring  312  inward, or controlled to stop the curtain body  45  from moving downward due to its own gravity (or an external force) by expanding the torsion spring  312  outward. 
     A second preferred embodiment of the front brake of an electric motor  10  in the present invention, as shown in FIG. 8, is to have a gear  50  fitted on the spindle  11  of the electric motor  10 . The gear  50  is directly engaged with the serrated portion  332  (equivalent to a gear) of the controlling rotary member  33 . The power driven by the electric motor.  10  in the second preferred embodiment has the same actuating and braking function and effect as those described in the first preferred embodiment. 
     A third preferred embodiment of the front brake of an electric motor in the present invention, as shown in FIG. 9, is to have a belt pulley  50  (gear-like) fitted on the spindle  11  of the electric motor  10 . The belt pulley  50  is separated from the controlling rotary member  33  for a certain distance and they are connected to each other by a transmission belt  51 . The teeth  52  of the transmission belt  51  (time-scale belt) and the gear  50  and the serrated portion  332  of the controlling rotary member  33  are engaged with one another. Thus, the electric motor  10  can be assembled with different mechanical devices in various ways, convenient in assembling and using. The power driven by the electric motor  10  in this preferred embodiment has the same actuating and braking function and effect as those described in the first preferred embodiment. 
     A fourth preferred embodiment of the front brake of an electric motor in the present invention, as shown in FIG. 10, is to have the front surface of the controlling rotary member  34  bored with plural insert holes  341 , and one side of the shaft coupling rotary disc  24  provided with plural projecting studs  241  to be inserted in the insert holes  341  to combine the shaft coupling rotary disc  24  together with the controlling rotary member  34 , equally enabling the electric motor  10  to actuate the brake to function. 
     A fifth preferred embodiment of the front brake of an electric motor in the present invention, as shown in FIG. 11, includes an electric motor  10 , a shaft coupling rotary disc  20  and a brake  30  combined together. The structure of the brake  30  in) the fifth preferred embodiment is almost the same as that in the first preferred embodiment, except that one sealing cover  314  (a) is formed integral on the front side of the base  31  and the other sealing cover  314  (a) is movably covered on the rear side of the base  31 . The two sealing covers  314  (a) are respectively and axially bored with a pivotal insert hole  315  (a) in the center. 
     While the preferred embodiments of the invention have been described above, it will be recognized and understood that various modifications may be made therein and the appended claims are intended to cover all such modifications that may fall within the spirit and scope of the invention.