The present invention relates to a tool for mounting and de-mounting
a transmission belt onto and from a pulley.
As is known, in belt transmission units the transmission belt passes
around associated pulleys comprising respective annular outer seatings engaged,
in use, by the belt itself.
Normally, for fitting a belt onto a pulley and for removal of a belt
from an associated pulley, general purpose tools are used, for example screw drivers,
which are not, in general, able to perform these operations in a correct manner,
and in particular which cause incisions and lacerations to the belts themselves
which, consequently, can have a relatively short service life and need frequent
The object of the present invention is that of providing a tool for
mounting a transmission belt onto a pulley and for de-mounting a belt from an associated
pulley, which is free from the above-explained disadvantage, and, in particular,
is a dedicated tool for performing these operations.
According to the present invention there is provided a tool for mounting
a transmission belt onto a pulley and for de-mounting a belt from a pulley, characterised
in that it comprises a cylindrical bearing wall tapered and curved along a longitudinal
direction and able in use to be positioned on an outer cylindrical surface of the
said pulley and to be forced radially between the said belt and the said pulley
to turn together with the pulley itself, and a deflection wall extending transversely
of the said bearing wall along a longitudinal edge of the bearing wall itself,
to define, in use, an abutment for a lateral surface of the said belt to deflect
the belt upon rotation of the said pulley about its axis.
The invention will now be described with reference to the attached
drawings which illustrate a non-limitative embodiment thereof, in which:
- Figures 1, 2 and 3 are, respectively, a side view, a plan view and a front
view of a preferred embodiment of the tool for mounting a transmission belt onto
a pulley and for de-mounting a belt from an associated pulley according to the
present invention; and
- Figures 4 and 5 illustrate in perspective and on a reduced scale the tool of
the preceding Figures used for mounting and, respectively, de-mounting a transmission
In Figures 4 and 5 the reference numeral 1 generally indicates a belt
transmission unit and, in particular, a transmission unit of a motor vehicle interposed
between a drive shaft and a shaft of an auxiliary unit (not illustrated). The unit
1 comprises a resilient toothed transmission belt 2 of known type and, in particular,
of the type commonly indicated with the term "poly-V", a pulley (not illustrated)
fitted on the shaft of the auxiliary unit, and a pulley 3 fitted on the drive shaft
to rotate about its axis 4.
The pulley 3 is delimited by an outer cylindrical surface 5 which
comprises an intermediate axial section 6 delimiting an annular seat 8 for the
belt 2, and two axial end sections 9 radially delimiting respective terminal rings
10 and 11. The rings 10 and 11 are delimited axially by respective outer surfaces
12 and respective inner surfaces 13 which define respective axial shoulders of
the seat 8.
To perform the operations for fitting the belt 2 onto the pulley 3
and for removal of the belt 2 from the pulley 3 there is provided a dedicated mounting/de-mounting
tool indicated 15 in the attached drawings.
As illustrated, in particular, in Figures from 1 to 3, the tool 15
is made in one piece, preferably of metal, and comprises a wall 16 extending in
a curved longitudinal direction and delimited by two surfaces 17 and 18 parallel
to one another. The wall 16 has an S-shape lateral profile (Figure 1) and comprises
a front end portion 19 and a cylindrical rear end portion 20 which have respective
axes 21 and 22 extending parallel to one another on opposite sides of the wall
16. In particular the portion of 20 is concave towards the surface 17 whilst the
portion 19 is concave towards the surface 18 and has a radius of curvature R1 slightly
greater than the outer radius of the pulley 3 and less than the radius of curvature
R2 of the portion 20.
With reference, in particular, to Figure 2, the wall 16 is tapered
longitudinally from the portion 19 towards the portion 20 in such a way as to present,
in plan, a substantially triangular shape having two longitudinal converging edges
23 and 24 of which the edge 24 is substantially orthogonal to the axis 21 and is
joined to two opposite lateral walls 27 and 28 which extend along the edge 23 and
the edge 24 respectively and form with the wall 16 respective obtuse angles equal
to one another and preferably about 100°.
As illustrated in Figures 1 and 2, the wall 27 is a flat wall comprising
two related end sections 30 and 31 adjacent the portion 19 and the portion 20 respectively,
and is tapered from the section 31 towards the section 30. The section 30 ends
with a projection 33 which extends about an axis 34 parallel to the axis 21 and
projects from the opposite side of the wall 16 from the wall 27; it is concave
in the same sense as the concavity of the portion 19 and has a radius of curvature
R3 greater than R1.
The wall 28, on the other hand, is substantially flat and comprises
an end 38 adjacent the portion 20 converging towards the wall 27 to merge with
the wall 27 itself.
At the opposite end of the tool 15 the wall 16 has a dimension measured
parallel to the axis 21 substantially equal to the width of the belt 2 and is delimited
by a front surface 40 inclined with respect to the axis 21 and forming an acute
angle with the wall 27.
With reference to Figure 4, in order to mount the belt 2, in use,
onto the pulley 3, the wall 28 is engaged with the inner surface of the ring 10
retaining the wall 16 manually against the section 9 of the surface 5 in a region
close to one run or branch of the belt 2 in such a way that the edge 24 is disposed
in correspondence with the section 9 with the wall 16 extending so as to project
out from the pulley 3.
The belt 2 is passed around the pulley of the auxiliary unit and coupled
to the tool 15 by positioning it in contact with the surface 17 and against the
wall 27. During rotation of the drive shaft in a clockwise sense, as viewed in
Figure 4, about the axis 4, the tool 15 is manipulated to interpose the wall 27
between the belt 2 and the pulley 3 in such a way as to force the wall 16 between
the belt 2 and pulley 3 upon elastic deformation of the belt 2 so as to cause the
tool 15 to rotate together with the pulley 3.
The wall 27 defines an abutment for a lateral surface 41 of the belt
2 so that, during the rotation of the pulley 3 about the axis 4, the wall 27 axially
deflects the belt 2 which progressively passes over the surface 17 towards the
pulley 3, passing over the ring 10 and engaging in the seat 8.
With reference to Figure 5, in order to de-mount the belt 2 from the
pulley 3 the wall 28 is engaged with the outer surface 12 of the ring 10 in a region
close to an outgoing branch of the belt 2 by positioning the wall 16 in contact
with the surface 5 in the seat 8 with the projection 33 bearing against the ring
Upon rotation of the drive shaft about the axis 4 in an anticlockwise
sense as seen in Figure 5, that is to say in the opposite sense of rotation to
that in which the motor operates, the wall 16 wedges between the belt 2 and the
pulley 3, remaining forced between the belt 2 and the pulley 3 itself upon the
elastic deformation of the belt 2, so that the tool 15 starts to turn together
with the pulley 3.
After this rotation the section 31 of the wall 27 lies alongside the
lateral surface 41 of the belt 2 and diverts the belt 2 which slides axially and
progressively over the surface 19 towards the outside of the pulley 3 passing over
the ring 10 until it is completely uncoupled from the seat 8.
From the above it is evident that the tool 15 described is a dedicated
tool both for mounting the belt 2 onto the pulley 3 and for de-mounting the belt
2 from the pulley 3 in a relatively simple and rapid manner without risk of damage
to the belt 2, therefore simplifying the operations for replacement of the belt
In fact, the tool 15 interposed and forced in use between the belt
2 and pulley 3 prevents the belt 2 from rubbing against the ring 2 or against other
parts of the pulley 3, whilst the wall 27 acts as a deflector and axially guides
the belt 2 simply upon rotation of the pulley 3.
Moreover, the wall 28 defines a precise reference for positioning
the edge 24 with respect to the ring 10 whilst the particular shape of the walls
16, 27, 28 facilitates and renders gradual the entry of the belt 2 into the seat
8 and its exit from the seat 8, preventing the belt 2 from coming into contact
with sharp corners.
From the above it is evident that the tool 15 described and illustrated
can have modifications and variations introduced thereto which do not depart from
the field of protection of the present invention.
In particular, the tool 15 could have different geometric proportions
from those illustrated to adapt it, for example, to a pulley 3 different from that
illustrated, and the walls 16, 27, 28 could have different shapes from those illustrated
and described by way of example.