Carriage driving apparatus

A carriage for use in disc driving or the like can be driven correctly by a carriage driving apparatus comprising guide shafts extended linearly, a carriage slidably supported on the guide shafts, a pulley holder rotatably supported around one of the guide shafts at one end thereof, a driven pulley rotatably journaled at one side of the pulley holder, a drive pulley disposed at a predetermined distance from the driven pulley and connected to a rotational shaft of a driving motor, a pulling belt laid around between the drive pulley and the driven pulley and connected at an intermediate portion thereof to the carriage and a base for supporting the guide shafts, wherein a pulley holder rotation inhibitive portion is disposed on the opposite side of a mounting portion for the driven pulley with respect to the guide shaft support portion of the pulley holder closely opposing to the base.

BACKGROUND OF THE INVENTION 
This invention concerns a driving apparatus for a carriage for use in a 
disc driving apparatus or the like. 
SUMMARY OF THE INVENTION 
The object of this invention is to provide a carriage driving apparatus 
capable of correctly transferring a carriage. 
The above object can be attained according to this invention by a carriage 
driving apparatus comprising guide shafts extended linearly, a carriage 
slidably supported on the guide shafts, a pulley holder rotatably 
supported around one of the guide shafts at one end thereof, a driven 
pulley rotatably journaled at one side of the pulley holder, a drive 
pulley disposed at a predetermined distance from the driven pulley and 
connected to a rotational shaft of a driving motor, a pulling belt laid 
around between the drive pulley and the driven pulley and connected at an 
intermediate portion thereof to the carriage and a base for supporting the 
guide shafts, wherein a pulley holder rotation inhibitive portion is 
disposed on the opposite side of a mounting portion for the driving pulley 
with respect to the guide shaft support portion of the pulley holder while 
opposing to the base.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
In FIGS. 1 and 2, a chassis 1 has a pair of guide shafts 2, 2 secured 
thereto in parallel by means of retainer plates 3, 3, and a carriage 4 is 
slidably supported on the guide shafts 2, 2. A magnetic head 5 for writing 
and reading to and from a flexible magnetic disc (not shown) is secured to 
the carriage 4. 
At the rearface of the chassis 1, is secured a driving motor (not shown), 
the rotational shaft 6 of which was securely fitted with a drive pulley 7. 
A belt 8 made of a thin metal sheet is wound around the drive pulley 7 and 
set to the pulley 7 by means of a threaded screw (not shown). The belt 8 
is also laid around a driven pulley 9 which is rotatably supported on one 
side of a pulley holder 10. The pulley holder 10 is rotatably journaled at 
its one end to the guide shaft 2, and a pulley holder rotation inhibitive 
portion 11 is disposed on the opposite side to the mounting portion for 
the driven pulley with respect to the guide shaft support portion. The 
pulley holder rotation inhibitive portion 11 is located as close as 
possible to the surface of the chassis 1 as shown in FIG. 2. 
A spring 12 extends between the pulley holder 10 and the mounting portion 
1b of the chassis 1, so that the endless belt 8 laid between the drive 
pulley 7 and the drive pulley 9 may always be applied with a tension and 
not slackened. A slight gap 13 is formed between the pulley holder 
rotation inhibitive portion 11 and the chassis 1 as shown in FIG. 2 so 
that the function of the spring may not be hindered. The belt 8 is formed 
with an aperture through which the projection 4a disposed from the 
carriage 4 is inserted to connect the carriage 4 with the belt 8, whereby 
the carriage 4 moves following the running of the belt 8. A cam protrusion 
7a formed on the upper surface of the drive pulley 7 can be abutted 
against a stopper member 14 for preventing the carriage 4 from 
uncontrolled running. A microswitch 15 actuated by the movement of the 
carriage 4 is disposed along the passage of the carriage. 
Referring then to the driving operation of the carriage 4 constituted as 
described above, the carriage 4 secured with a head 5 is slidable being 
guided along the guide shafts 2, 2 and driven by the belt 8 laid around 
the drive pulley 7 and the drive pulley 9. The drive pulley 7 is securely 
fitted with the rotational shaft 6 of the driving motor. As the driving 
motor rotates, the belt 8 secured to the drive pulley 7 moves and the 
carriage 4 is transferred together with the belt 8 in the direction of 
tracking a magnetic disc. Since the driving pulley 9 is freely journaled 
on the pulley holder 10 and the belt 8 is always supplied with the tension 
from the spring 13, the carriage 4 can accurately be transferred. 
Furthermore, since the pulley holder 10 is supported on the guide shaft 2, 
it may possibly be rotated about the guide shaft 2 as the axial center due 
to the vibrations caused upon transfer of the carriage 4 or the like. 
However, since the pulley holder 10 is inhibited by the pulley holder 
rotation inhibitive portion 11 from excess rotation, no positional 
displacement is caused to the belt 8 wound around the driven pulley 9. 
Consequently, the carriage 4 driven by the belt 8 can always be 
transferred smoothly along the guide shafts 2, 2 in the direction of 
tracking the magnetic disc. When the carriage 4 arrives at a zero track 
position, the microswitch 15 is actuated to stop the transfer of the 
carriage 4. 
In this invention, the pulley holder rotation inhibitive portion is 
disposed on the opposite side to the mounting portion for the driven 
pulley with respect to the guide shaft bearing portion of the pulley 
holder while opposing to the base. Accordingly, if a force tending to 
rotate the pulley holder around the guide shaft is exerted during transfer 
of the carriage or the like, the rotation of the pulley holder can be 
inhibited by the pulley holder rotation inhibitive portion to always 
stretch the belt at an exact position between the drive pulley and the 
driven pulley, whereby the carriage can be transferred by a predetermined 
amount to conduct the correct tracking for the magnetic disc.