A laminator is a device that performs a coating operation using heat and pressure applied by a roller in a state that a to-be-coated plate-shaped member is inserted between laminating films.
Additionally, there are two types of the laminator. One is a large-sized laminator suitable for laminating large quantities and the other is a small-sized laminator suitable for laminating small quantities.
Specifically, the small-sized laminator for home use or portable has a simple construction in which a pair of rollers apply heat and pressure. Generally, the small-sized laminator employs one-way rotating motor so as to reduce its manufacturing cost and scale down its volume.
Accordingly, there is demanded a roller driving apparatus for a laminator, in which a roller can rotate in a backward direction so as to remove jammed films, as well as in one direction at a forward rotation.
FIG. 1 is a perspective view showing a roller driving apparatus of a conventional laminator.
Referring to FIG. 1, the roller driving apparatus of the conventional laminator includes one pair of supporting frames 31a and 31b facing each other, upper and lower rollers 33a and 33b installed between the supporting frames 31, upper and lower roller gears 34a and 34b coupled with each one end of the rollers 33 to transfer rotational forces of the rollers 33, one pair of connection gears 35a and 35b selectively coupled to the upper roller gear 34a and the lower roller gear 34b to transfer the rotational force, a motor gear 16 selectively transferring a rotational force of a motor M to the connection gears 35, a motor fixing member 32 to which the motor M is coupled, and a manipulating member 37 for manipulating a transfer direction of the connection gears 35 by using an external force.
FIG. 2 is an exploded perspective view showing the roller driving apparatus of the conventional laminator.
Referring to FIG. 2, the roller driving apparatus includes: one pair of upper and lower connection gears 35a and 35b; upper and lower gear shafts 39a and 39b inserted into central axes of the upper and lower connection gears 35a and 35b; a manipulating member 37 into which the upper and lower gear shafts 39a and 39b are inserted so as to be movable in correlation to the upper and lower gear shafts 39a and 39b and with which a user directly applies an external force upward and downward; and a fixing spring 38 for stably fixing positions of a central shaft 40 and the manipulating member 37 around the rotational center of the manipulating member 37.
In more detail, the manipulating member 37 includes upper and lower shaft fixing holes 371 and 373 and a spring guide 374. The upper and lower connection gears 35a and 35b are internally inserted into the upper and lower fixing holes 371 and 373, and the central shafts of the upper and lower connection gears 35, i.e., the upper and lower gear shafts 39a and 39b, are inserted thereinto, so that the upper and lower connection gears 35 are supported. The spring guide 374 has two guide faces that are in contact with central-shaft fixing holes 372 into which the central shaft 40 is inserted and a fixing spring 38 to thereby fix the position of the manipulating member 37.
Also, the upper and lower gear shafts 39a and 39b are inserted into the supporting frame 31b, the connection gears 35, the motor fixing member 32 and specially the manipulating member 37, so that the mesh state of the connection gears 35 is changed according to an external force applied by the user.
Further, the supporting frame 31b and the motor fixing member 22 include upper shaft guides 311 and 321 and lower shaft guides 313 and 323 into which the upper and lower gear shafts 39a and 39b are respectively inserted, and circular central holes 312 and 322 into which the central shaft 40 is inserted. Particularly, the upper shaft guides 311 and 321 and the lower shaft guides 313 and 323 are formed in an arc shape so that the upper and lower gear shafts 39a and 39b can be properly moved in left and right directions according to a change of positions of the connection gears 35. Furthermore, in order that the position of the fixing spring 38 is correctly fixed at both front and rear ends, spring inserting holes 314 and 324 having the same outward shape as the fixing spring 38 are further formed on each one side of the supporting frame 31b and the motor fixing member 32. At this time, the position of the fixing spring 38 can be fixed by pushing into the spring inserting holes 314 and 324.
Additionally, the roller driving apparatus further includes protrusions 318, 319, 329 and 330 for fixing positions of the upper and lower gear shafts 39a and 39b through the upper shaft guides 311 and 321 and the lower shaft guides 313 and 323. It is desirable that the protrusions 318, 319, 329 and 330 should be formed on an outside of the central shaft 40.
If the user moves the manipulating member 37 in upward and downward directions to thereby move the upper and lower connection gear 35a and 35b internally inserted into the manipulating member 37, the upper and lower connection gears 35a and 35b are meshed with the upper and lower roller gears 34a and 34b or separated therefrom, so that the rotational force whose transfer direction is changed into forward or backward direction is transferred.
The upper shaft guides 311 and 321 and the lower shaft guides 313 and 323 are formed on the supporting frame 31b and the motor fixing member 32 in the arc shape so as to guide the movement of the upper and lower gear shafts 39a and 39b. 
Meanwhile, the change of the position of the connection gears 35 results in that of the mesh between the motor gear 36 and the roller gears 34 to thereby change the transfer direction of the rotational force, so that the forward and backward rotations of the rollers 33 are manipulated to the user's intentions.
In order to stably support the changed position of the manipulating member 37, the fixing spring 38 is inserted into the spring guide 374 so that a predetermined force is applied to the manipulating member 37.
Additionally, after the manipulating member 37 is moved upward or downward, the manipulating member 37 is hung between the supporting bar 327 and the supporting bar hanging projections 375, so that the position of the manipulating member 37 is fixed.
Further, after the upper gear shaft 39a and the lower gear shaft 39b moves to one side, the protrusions 318, 319, 329 and 330 firmly fix the positions of the upper and lower gear shaft 39a and 39b so that the upper and lower gear shafts 39a and 39b cannot be released unless a force is applied beyond a predetermined strength. Meanwhile, to make it possible to move the positions of the upper and lower gear shafts 39a and 39b by a predetermined force, it is desirable that at least one of the manipulating member 37 and/or the upper gear shaft 39a and the lower gear shaft 39b and/or the motor fixing member 32 and the right supporting frame 31b is formed of a plastic material with elasticity.
FIGS. 3 to 5 are views showing a forward rotation state, a backward rotation state and a stopped state of the roller in the conventional laminator, respectively.
Referring to FIG. 3, in case that the user pushes upwards the manipulating member 37 to change the position of the manipulating member 37 in a counterclockwise direction, the upper connection gear 35a is meshed with the motor gear 36 and the upper roller gear 34a. In the end, the rotational force of the motor is transferred to the upper roller 33a through the motor gear 36, the upper connection gear 35a and the upper roller gear 34a. Then, the upper roller gear 34a is meshed with the lower roller gear 34b to generate the rotational force of the lower roller gear 34b, so that the lower roller 33b also rotates with the same revolutions as the upper roller 34a. 
At this time, the manipulating member 37 is in a state rotated in the counterclockwise direction around the central shaft 40. The upper gear shaft 39a is in contact with a left side of the arc-shaped upper shaft guide 321 and the lower gear shaft 39b is in contact with a right side of the arc-shaped lower shaft guide 323, thereby setting its position. The fixing spring 38 is in contact with a second guide face 374b of the spring guide 374 to apply a predetermined force to the manipulating member 37, so that the mesh of the upper connection gear 35a is not released even by a torque applied to the manipulating member 37 when the upper connection gear 35a rotates.
Referring to FIG. 4, in case that the user pushes downward the manipulating member 37 to rotate the position of the manipulating member 37 in a clockwise direction, the lower connection gear 35b is meshed with both the motor gear 36 and the lower roller gear 34b. As a result, the rotational force of the motor is transferred to the lower roller 33b through the motor gear 36, the lower connection gear 35b and the lower roller gear 34b. Also, the lower roller gear 34b is meshed with the upper roller gear 34a and generates the rotational force of the upper roller gear 34a, so that the upper roller 33a also rotates at the same revolutions as the lower roller 34b. 
At this time, the manipulating member 37 is in a state rotated in the clockwise direction around the central shaft 40. The upper gear shaft 39a is in contact with a right side of the arc-shaped upper shaft guide 321 and the lower gear shaft 39b is in contact with a left side of the arc-shaped lower shaft guide 323, thereby setting its position. The fixing spring 38 is in contact with a first guide face 374a of the spring guide 374 to apply a predetermined force to the manipulating member 37, so that the mesh of the upper connection gear 35a is not released even by a torque applied to the manipulating member 37 when the upper connection gear 35a rotates.
Referring to FIG. 5, the user applies an external force to the manipulating member 37 to contact the fixing spring 38 with an edge of a central portion of the spring guide 374 without any contact with the guide faces 374a and 374b of the spring guide 374. In this state, any connection gears 35 are not meshed with the roller gears 34. Thus, the rotational force of the motor M is not transferred to the rollers 33. Also, it is possible to obtain a more stable operation by forming the spring guide with three faces
At this time, the user can remove the rolled film from the laminator by directly pulling it out. However, the user should keep on holding the manipulating member 37 while the rolled film is removed.
It can be seen that the position of the supporting bar 327 is fixed more firmly because the supporting bar 327 is hung on the supporting hanging projections 357. Also, because the positions of the upper and lower gear shafts 39a and 39b are fixed to the protrusions 318, 319, 329 and 330, the position of the manipulating member 37 can be fixed more firmly.
However, according to the roller driving apparatus of the conventional laminator, the driving speed of the roller in the forward rotation is equal to that in the backward rotation, so that operation efficiency of the small-sized laminator is lowered.
For example, in order to apply heat and pressure for a predetermined time, it is desired that the laminator should carry out the forward rotation for a predetermined long time while the laminator rapidly carries out the backward rotation when the laminator rotates backward so as to remove a film. Accordingly, it is inefficient that the roller always rotates at the same speed in both the forward rotation and the backward rotation.