Note: Descriptions are shown in the official language in which they were submitted.
CA 02594064 2007-07-19
PNEUMATIC BASE FOR FACILITATING THE INSTALLATION AND
TENSIONING OF A DRIVE BELT
FIELD OF THE INVENTION
The present invention generally relates to drive belt transmissions and,
more particularly, to belt tensioning devices.
BACKGROUND ART
In belt drive systems, the tension in the drive belt must be maintained
above a predetermined level to avoid slippage between the belt and the
pulleys.
During use, various factors, such as wear, heat and vibrations may have an
impact on
the level of tension in the belt. Accordingly, various belt tensioners have
been
developed over the years to maintain a desired tension in the belt. Such belt
tensioners are typically provided in the form of a belt engaging roller
mounted at the
distal end portion of an actuator and disposed to engage the belt between two
pulleys.
The actuator is set to urge the roller in contact with the belt in a belt
tensioning
direction with a force selected to appropriately tension the belt.
Such system suffers from several drawbacks. For instance, they do not
provide for easy installation and removal of a drive belt. Also, they tend to
neutralize
the vibrations transmitted to the belt by the drive unit instead of
suppressing the
vibrations at the source. Finally, conventional belt tensioners are provided
as
additional parts to be installed for the single purpose of tensioning the belt
and as
such they contribute to increase the installation costs and times.
SUMMARY
It is therefore an aim of the present invention to address the above
mentioned concerns.
Therefore, in accordance with a general aspect, there is provided a
power transmission belt arrangement comprising a power unit mounted on a
pneumatic base, the pneumatic base comprising at least one pneumatic actuator
and a
power unit mounting plate mounted for pivotal movement about a pivot axis, the
pneumatic actuator being displaceable between a collapsed position and an
extended
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position to cause pivotal movement of the power unit mounting plate with the
power
unit fixedly mounted thereon, a drive pulley mounted to a rotating output
shaft of
said power unit, a belt trained on the drive pulley and extending around a
driven
pulley for transmitting a torque from said output shaft to said driven pulley,
whereby
pivotal movement of said power unit mounting plate via actuation of said
pneumatic
actuator provides for the adjustment of the distance between the drive pulley
and the
driven pulley and therefore for the adjustment of the tension in the belt.
In accordance with another general aspect, there is provided a belt
tensioner comprising a belt trained on a drive pulley driven by a drive unit
mounted
on a base supported on at least one air-spring bellows linearly extendable
under fluid
pressure from a collapsed position to an extended position to cause joint
movement
of the base, the drive unit and the drive pulley and thereby change the
tension in the
belt; and a pressure regulator operatively connected to said at least one air-
spring
bellows for regulating the fluid pressure in said air-spring bellows at a
fixed value
such as to maintain the tension substantially constant in said belt during
use.
In accordance with a further general aspect, there is provided a method
of maintaining a desired tension in a drive belt extending around a drive
pulley and at
least one driven pulley, the drive pulley being mounted on a rotating shaft of
a drive
unit; the method comprising: mounting the drive unit on a pneumatic base
including
at least one pneumatic actuator displaceable between a retracted position and
an
extended position, the movement of the pneumatic actuator varying the distance
between the drive pulley and the driven pulley, and setting the pressure of
the
pneumatic actuator at a fixed value corresponding to the desired tension in
the belt,
whereby belt tension fluctuations are automatically compensated by a
corresponding
extension variation of the pneumatic actuator.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a perspective view of a drive belt arrangement in accordance
with one embodiment of the present invention; and
Fig. 2 is an end view of the drive belt arrangement shown in Fig. 1.
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DESCRIPTION OF THE PREFERRED EMBODIMENTS
Fig. 1 shows a power transmission or drive belt arrangement
comprising an endless belt 12 extending over a drive pulley 14 and a driven
pulley
15. The drive pulley 14 is keyed or otherwise secured to the output shaft 16
of a
motor 18. The motor 18 is fixedly mounted on a pneumatic base comprising a
horizontally disposed mounting plate 20 which is, in turn, pivotally mounted
along a
first side 22 to a vertically oriented stationary plate 24. As shown in Fig.
2, the pivot
can be provided in the form of a hinge mounted between the undersurface of the
mounting plate 20 and the vertically oriented stationary plate 24. The hinge
provides
a fixed horizontal pivotal axis for the mounting plate 20. Other suitable
orientation
and pivot arrangement could be used as well.
The pneumatic base of the motor 18 further comprises at least one
fluidly driven actuator, such as the air-spring bellows 28 shown in Fig.l. The
air-
spring bellows 28 is installed underneath the mounting plate 20. The air-
spring
bellows 28 can be inflated and deflated between extended and collapsed
positions to
cause upward or downward pivotal movement of the mounting plate 20. By so
pivoting the mounting plate 20, the drive pulley 14 can be displaced towards
or away
from the driven pulley 15, thereby providing for the adjustment of the tension
in the
drive belt 12. The air-spring bellows 28 is mounted between a stationary
bottom
surface 30 and the mounting plate 20 at a second side of the mounting plate
opposite
the first side 22 thereof (i.e. opposite the pivot). The air-spring bellows 28
could, for
instance, consists of Air Spring model Y1-1S3 manufactured by ENDINE Inc...
AirstokeTM actuators or AirmountIM isolators manufactured by Firestone
Industrial
Product Company could be used as well. It is noted that the expression "air-
spring
bellows" is herein intended to broadly refer to elastomeric or rubber-like
bellows
adapted to contain a column of a compressed fluid. A wide variety of actuation
media
such as air, water, nitrogen and other suitable pressurized liquid or gas
could be used.
Therefore, the expressions "air-spring bellows" or "pneumatic" should not be
construed as only referring to air as the actuation media.
A pressure regulator 30 is operatively connected to the air-spring
bellows 28 to adjust the pressure therein according to the desired level of
tension in
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the drive belt 12. The pressure regulator 30 is mounted in a fluid line of a
fluid
pressure source (typically a source of compressed gas, such as compressed
air). The
pressure regulator 30 is of standard construction and typically comprises a
valve set
to maintain the pressure constant in the air-spring bellows irrespective of
the volume
variations of the bellows.
In use, the air-spring bellows 28 is first deflated or at least partly
deflated to permit easy installation of the belt over the pulleys 14 and 15.
Then, the
air-spring bellows 28 is inflated to cause the mounting plate 20 to pivot
upwardly so
as to increase the distance between the pulleys 14 and 15 until reaching the
desired
tension in the belt 12. The tension in the belt 12 is electronically measured
using any
appropriate sensing tool. Once the desired tension in the belt has been
obtained, the
regulator 30 is adjusted to constantly maintain the air-spring bellows 28 at
an internal
pressure corresponding to the desired tension in the belt 12. Belt wear, heat
variations, vibrations as well as other factors may produce variations in the
length of
the belt 12, which length variations are automatically compensated by a
corresponding variation of the volume and, thus, of the height of the air-
spring
bellows 28. For instance, in the event of an increase of the length of the
belt 12, the
pressure exerted on the air-spring bellows 28 will decrease and since the
internal
pressure of the air-spring bellows 28 is maintained at a predetermined set
value by
the pressure regulator 30, the volume of the air-spring bellows 28 will
automatically
expand, thereby increasing the distance between the pulleys 14 and 15 and
compensating for the belt length increase. In this way, the tension in the
belt 12 can
be maintained constant at all time irrespective of belt length variations and
that
without the intervention of an operator. This prevents slippage between the
belt 12
and the pulleys 14 and 15. A worn belt can be readily replaced by simply
releasing
pressure from the air-spring bellows to displace same towards its collapsed
position.
The worn belt can then be removed from the pulleys 14 and 15 and a new one
installed therearound without requiring any other adjustments.
The positioning of the air-spring bellows underneath the motor is
advantageous in that it provide a damping base for the motor which allows
reducing
the vibrations on all the parts of the system. This contributes to increase
the service
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life of all the parts. It also contributes to reduce the occupational noise in
the plant
where the belt drive arrangement is installed. The above described pneumatic
base
thus solves several problems all at once.
The above description is meant to be exemplary only, and one skilled
in the art will recognize that changes may be made to the embodiments
described
without department from the scope of the invention disclosed. For instance, it
is
understood that motor 18 could be replaced with any other suitable types of
power or
driving units. Also, it is understood that the motor 18 and the air-spring
bellows 28
could be vertically oriented as opposed to the illustrated horizontally
disposed
installation. Other installation angles are contemplated as well. Finally, it
is understood that more than one air-spring bellows could be provided
underneath the
mounting plate 20. Other modifications which fall within the scope of the
present
invention will be apparent to those skilled in the art, in light of a review
of this
disclosure, and such modifications are intended to fall within the appended
claims.
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