Brake release device attached to a door machine

1. A brake release device ( 40 ) attached to a door machine, said door machine ( 1 ) comprises an axle ( 2 ), a brake device ( 10 ) for braking said axle ( 2 ), a brake release bar ( 20 ) provided at the outside of said door machine ( 1 ) for actuating said brake device ( 10 ) to release said axle ( 2 ), and a pull chain disc ( 31 ) for rotating said axle ( 2 ), wherein said brake release device ( 40 ) comprises:

a ring plate ( 41 ) fixed on a lateral end face of said pull chain disc ( 31 ), a plurality of equally spaced openings ( 411 ) being formed along the entire circumference of said ring plate;

a base plate ( 43 ) provided at the outside of said door machine ( 1 ), and having a horizontal guiding portion ( 431 ) at one end thereof;

a passive plate ( 44 ) having a plurality of plug pins ( 441 ) corresponding to said openings ( 411 ) of said ring plate ( 41 ) being provided on one end face thereof, said passive plate being guided by said guiding portion ( 431 ) to move between a first position in which said plug pins ( 441 ) are separated from said openings ( 411 ), and a second position in which said plug pins ( 441 ) are inserted into corresponding openings ( 411 );

a guiding member ( 45 ) parallel to said axle ( 2 ) being disposed on said base plate ( 43 ), said guiding member ( 45 ) having an axial guiding hole ( 451 );

a sliding pin ( 46 ) mounted within said guiding hole ( 451 ) for sliding therein, one end of said sliding pin ( 46 ) corresponding to said brake release bar ( 20 ) and the other end of said sliding pin ( 46 ) being connected to said passive plate ( 44 );

a spring element ( 47 ) accommodated in said guiding hole ( 451 ), one end of said spring element ( 47 ) abutting against said guiding member ( 45 ) and the other end of said spring element ( 47 ) abutting against said sliding pin ( 46 ) to an effect that said sliding pin ( 46 ) is compressed by said spring element and tends to move toward said brake release bar ( 20 ); and

a fusible link device ( 48 ) having one end provided at a predetermined position, and the other end connected with said sliding pin ( 46 ) through a connecting member ( 481 ) so as to resist the restoring force of said spring element ( 47 ), so that the sliding pin is maintained at a distance from said brake release bar ( 20 ), and said passive plate ( 44 ) is maintained at said first position; when the surrounding temperature exceeds the melting point of said fusible link device ( 48 ), said fusible link device ( 48 ) melts and said connecting member ( 481 ) connecting said sliding pin is released, and said sliding pin ( 46 ) slides toward said brake release bar ( 20 ) under the action of the restoring force of said spring element to impact against said brake release bar ( 20 ) so as to release said brake device ( 10 ), whereby said passive plate ( 44 ) is actuated to move to said second position.

2. The brake release device as claimed in claim 1 , wherein said pull chain disc ( 31 ) is accommodated in a housing ( 1 a ) of said door machine ( 1 ), said ring plate ( 41 ) being provided on the right end face of said pull chain disc ( 31 ), a plurality of through holes ( 1 b ) corresponding to said openings ( 411 ) of said ring plate ( 41 ) being provided on said housing ( 1 a ); said base plate ( 43 ) being fixed at an outside end face of said housing ( 1 a ), said base plate ( 43 ) having a space for receiving said passive plate ( 44 ) therein, said passive plate ( 44 ) having at least one pair of plug pins ( 441 ) provided within said through holes ( 1 b ) of said housing ( 1 a ).

3. The brake release device as claimed in claim 2 , wherein each of said plurality of plug pins ( 441 ) includes a small diameter segment ( 441 a ) at one end thereof with an end portion of said small diameter segment slidably disposed on the passive plate ( 44 ); a spring component ( 442 ) being arranged to encircle the periphery of said small diameter segment ( 441 a ) with one end thereof abutting against said plug pin ( 441 ) and the other end thereof abutting against said passive plate ( 44 ) so that said plug pin ( 441 ) has a tendency to restore to its original position during sliding.

4. The brake release device as claimed in claim 3 , wherein each of said plurality of plug pins ( 441 ) has a small diameter end ( 441 b ) formed at one end facing said ring plate ( 41 ); when said brake release device ( 40 ) releases the brake, said small diameter ends ( 441 b ) of said plug pins ( 441 ) are inserted into said openings ( 411 ) so as to lock said pull chain disc ( 31 ) into an irrotational state.

5. The brake release device as claimed in claim 1 , wherein said brake device ( 10 ) comprises:

a support stand ( 11 ) arranged to encircle the outer periphery of said axle ( 2 ) of said door machine ( 1 ) and received in said housing of said door machine ( 1 ), said support stand ( 11 ) having a plurality of guiding rods ( 111 ) fixed at one end and disposed to be parallel with said axle ( 2 );

a moving disc ( 12 a ) movable in an axial direction of the axle ( 2 ) by being guided by said guiding rods ( 111 );

a stationary disc ( 12 b ) provided at the other end of said guiding rods ( 111 ) and is arranged to face said moving disc;

a braking component ( 13 ) including a sliding portion ( 131 ) and a brake disc ( 132 ), said sliding portion being arranged on said axle of the door machine such that the sliding portion is movable in said axial direction of the axle by a predetermined range, said brake disc ( 132 ) being arranged to be interposed between said moving disc ( 12 a ) and said stationary disc ( 12 b ), brake linings ( 133 ) being provided on both sides of said brake disc ( 132 ) so as to be in frictional engagement with said moving disc ( 12 a ) and said stationary disc ( 12 b );

at least one compression spring ( 15 ) having one end biasing against said moving disc ( 12 a ) so as to urge said brake disc ( 132 ) against said stationary disc ( 12 b ), to thereby clamping said brake disc ( 132 );

an electromagnet ( 15 ) arranged to oppose said moving disc ( 12 a ) and configured to retract said moving disc ( 12 a ) when energized, so as to disengage said moving disc ( 12 a ) from said brake disc ( 132 ), to thereby releasing said braking component ( 13 ); and

a restoring spring sheet ( 16 ) having one end disposed on an end face of said sliding portion ( 131 ) and the other end abutting against said axle ( 2 ), and is compressed when said brake disc ( 132 ) is clamped, and when said moving disc ( 12 a ) is retracted to disengage from said brake disc, the restoring force of said spring sheet acts on said sliding portion ( 131 ), so as to disengage said brake disc ( 132 ) from said stationary disc ( 12 b ).

6. The brake release device as claimed in claim 5 , wherein said brake release bar ( 20 ) comprises a U-shaped portion ( 21 ) at the other end thereof, both end portions of said U-shaped portion ( 21 ) being pivotally disposed on said stationary disc ( 12 b ), projections ( 211 ) being provided on said end portions of said U-shaped portion ( 21 ) to abut against said moving disc ( 12 a ), when said brake release bar ( 20 ) is actuated by an external force, so as to disengage said moving disc ( 12 a ) from said brake disc ( 132 ).

7. The brake release device as claimed in claim 6 , wherein said brake device ( 10 ) comprises a sensor switch ( 17 ) electrically connected to the circuit of said door machine ( 1 ); said U-shaped portion ( 21 ) of said brake release bar ( 20 ) having a contact arm ( 212 ) that triggers said sensor switch ( 17 ) to switch off the circuit of said door machine ( 1 ) when said brake release bar ( 20 ) is actuated by the external force to release the brake.