The present invention concerns a pulley assembly for belt drives
according to the preamble of claim 1.
In particular, the object of the present invention is intended to
be used on belt drives of the type mounted on motorvehicle engines and the like.
As known, in the motorvehicle engines and the like, the actuating
of the common members, as for instance, the a.c. generator and the cooling pump,
the pump of the power steering, the compressor of the air conditioner and other
ones, is given to a driving belt extending according to a closed line around a
driving pulley, moved by the engine itself, as well as around different driven
pulleys arranged for setting in action the above said members. Moreover, in a lot
of cases there are provided one or more idle pulleys, used as simple slide guide
pulleys and/or associated to known belt tensioners apt to give a constant tensioning
to the belt itself, to assure a uniform transmission of motion in absence of slipping
The above said idle pulleys usually are mounted on respective supporting
pivots upon previous interposition of rolling ball bearings or rollers. More particularly,
each bearing has its own fixed inner ring, rigidly fitted around a supporting
core borne by the stationary structure of the engine or by a movable arm making
part of the belt tensioner as well as a rotating outer ring, anchored in an engagement
housing obtained within a fastening collar making part of the pulley. A disc-shaped
flange radially projects from the fastening collar of substantially cylindrical
shape, said disc-shaped flange supporting, in a radially outer position, a cylindrical
rolling portion which circumscribes coaxially the fastening collar and has an outer
working area arranged to act in contact relation with the driving belt.
In consideration of the aforesaid, it is pointed out that the bearings
mounted on the above said pulleys are subjected to working situations that expose
them to risks of premature wearing and/or seizing owing to the great quantity
of dust, deposits, water and other outer agents to which they are exposed.
It is clear that such a situation represents a great problem, since
in consequence of the bearing seizing, the driving belt breaks owing to the strong
sliding of the same on the locking pulley.
The attempts made up to now to overcome said type of problem are
potentially directed to use protecting elements secured to the supporting central
core of the bearing in order to protect this latter from the contact with the
above mentioned outer agents.
By way of example, see what shown in the figures of the U.S. Patents
No. 4,551,120 and No. 4,698,049 and of U.K. patent No. 2,258,287.
However, these solutions cannot guarantee an absolute protection
of the bearing since, in order to avoid mechanical interferences between the fixed
protection and the pulley or the movable part of the bearing, it is necessary
to provide mechanical clearances that, as far as reduced, constitute in any case
a way through which the outer agents can reach the bearing.
FR-A-2274461 discloses a pulley assembly as claimed in the preamble
of claim 1, including a pulley mounted on a shaft through the interposition of
a bearing assembly and a protecting device to protect the bearing assembly. The
protecting device presents a relatively complex and expensive structure, since
it is formed by two different elements, a sealing ring forced inside the pulley
and against the outer ring of a rolling bearing of the bearing assembly, and a
cover coupled to the sealing ring.
In agreement with the present invention, it has been found that the
bearing is perfectly protected utilizing a cover engageable in a tight manner on
any one of the two terminal edges of the fastening collar and anchorable in a
removable manner to the pulley by hooking means operating across through openings
obtained in the disc-shaped-flange; it is solved the technical problems deriving
from the anchoring of the cover itself on the pulley rotatable part in presence
of the considerable centrifugal stresses, the whole maintaining the possibility
of easily removing the cover itself and considerably containing the costs for its
More particularly, the invention concerns a pulley assembly for belt
drives according to the preamble of claim 1, including a device for protecting
said bearing characterized by the features according to the characterizing portion
of claim 1.
Moreover it is provided that the said elastic means are also elastically
deformable in consequence of the centrifugal force, so that the interference between
the hooking means and the radially outer edges of said openings tends to increase
by increasing the rotation speed of the pulley.
Advantageously, said hooking means comprise a plurality of hooking
teeth circumferentially arranged around the axis of the cover and each showing
a substantially wedge-shaped profile defined by an inclined guide surface directed
to the opposite part with respect to the cover and arranged to interfere with the
radially outer edge of the corresponding engaging opening to which a stop surface
follows; said stop surface being turned towards the cover and oriented in a substantially
radial direction with respect to the axis of this latter to act in abutment relationship
against the disc-shaped flange, on the opposite part with respect to the cover,
said guide and stop surfaces meeting at an apex spaced from the axis of the cover
according to a measure greater than the radial distance of the outer edge of said
engaging opening with respect to the axis of the pulley.
Preferably, the elastic means comprise on their turn a plurality
of elastic tongues extending in a projecting manner from said cover and each supporting
at their ends one of said hooking teeth.
Preferably there are also provided centering means associated to
said cover to guide it coaxially to the fastening collar during the engagement
of the cover itself with the pulley.
Advantageously, said centering means comprise circumferentially distributed
pins, extending in a projecting manner from the cover and arranged to slidly act
in opposition relation, on the outer cylindrical surface of the fastening collar.
According to the requirements, it is possible to provide at least
two hooking teeth and at least two elastic tongues placed in diametrically opposite
positions with respect to the axis of the cover and able to operatively fit into
corresponding through engaging openings, or at least three hooking teeth and at
least three corresponding closing tongues, distributed angularly at 120 degrees
with respect to the axis of said cover.
More in detail, in a preferred embodiment the device forming the
object of the present invention comprises four hooking teeth and four corresponding
closing tongues, distributed according to an angular pitch of 90 degrees with
respect to the axis of the cover and arranged to fit into corresponding through
Further features and advantages will better appear from the detailed
description of some preferred, but not exclusive, embodiments, of a device for
protecting bearings of pulleys in belt drives according to the present invention.
Said description will be made hereinafter with reference to the attached sheets
of drawing, supplied by way of non-limiting example, wherein:
- Figure 1 shows schematically a discontinued perspective view of a belt drive
associated to a motorvehicle engine and provided with a tensioner to assure a
correct tensioning action of the belt;
- figure 2 is an exploded perspective view of a pulley provided with the device
for protecting the bearing according to the present invention;
- figure 3 is a lateral view of a pulley provided with the protecting device
forming the object of the present invention;
- figure 4 is a sectional view of the pulley of figure 3.
With reference to the cited figures, and in particular to figures
2 and 4, reference numeral 1 indicates a device for protecting bearings of pulleys
in belt drives, taken as a whole, according to the present invention.
In the example referred to in figure 1, the device 1 is associated
to an idle pulley 2, operatively connected to a movable arm 3 making part of a
conventional belt tensioner 4, associated on their turn to a belt drive of a motorvehicle
engine indicated as a whole with reference numeral 5 in figure 1, in order to assure
a correct tensioning action to a driving belt 6.
As information, in the example of figure 1 the driving belt 6, moved
by a driving pulley 7, put into rotation by the engine, provides to set in action
a first, second, third, fourth and fifth driven pulley 8, 9, 10, 11 and 12, respectively
associated to a cooling pump (not shown), a pneumatic feed pump 9a for a ventilating
circuit of the vehicle, an alternator 10a, a compressor 11a for the cooling circuit
of an air conditioner, as well as to a hydraulic pump of a power steering (not
The pulley 2 is of the type made of plastic material molded by injection
and has conventionally a fastening collar 13 of a substantially cylindrical configuration,
a connecting disc-shaped flange 14 extending coaxially around the fastening collar
13 substantially according to a plane perpendicular to the axis of this latter,
as well as a cylindrical rolling portion 15 circumscribing coaxially the fastening
collar 13 and the connecting flange 14. An outer working area 15a is obtained on
said cylindrical rolling portion 15, said outer working area 15a being arranged
to act in contact relationship on the driving belt 6, in a length comprised between
the third and the fourth driven pulleys 10 and 11.
Radial ribs 14a equally angularly spaced are moreover arranged between
the fastening collar 13 and the cylindrical rolling portion 15. Inside the fastening
collar 13 there is an engagement housing 16 in which an outer ring 17 is fixed,
said outer ring 17 making part of a common ball bearing 18 whose inner ring 19
is coaxially fitted around a supporting core 20 projecting from the above said
More particularly, the fixing of the outer ring 17 in the engagement
housing 16 can be obtained, for example, by forcing the bearing 18 into the fastening
collar 13, or by forming the pulley 2 directly around the outer ring itself after
having placed the bearing 18 inside the injection mould utilized for realizing
the pulley 2.
The inner ring 19, on its turn, is fixed on the supporting core 20
through a forcing action and/or with the aid of an axial blocking threaded device
The device according to the present invention aims to protect the
bearing 18 from the contact with dust, sand, particles, water and any other substance
that can cause a premature wearing and/or impair its functionality.
To this end, the device 1 comprises at least a cover 22 placed coaxially
against one side of the pulley 2, as clearly visible in figures 2 and 3.
The cover 22 has a circumferential connecting portion 23 countershaped
to and operatively engageable with one of the terminal edges 13a of the fastening
As it can be easily noticed from figure 3, the engagement between
the circumferential connecting portion 23 of the cover 22 and the corresponding
terminal edge 13a of the fastening collar 13 takes place substantially in a hermetic
seal relationship, so that, on the side of the pulley 2 supporting the cover itself,
the bearing 18 is completely protected from the contact with the outer agents.
In the represented example, on the side of the pulley 2 opposite
to the cover 22, the protection of the bearing 18 from the contact with particles
and impurities is given, in a way known per se, to a flat screening surface 3a
defined on the movable arm 3, or on another fixed structure bearing the supporting
core 20, extending close by the terminal edge 13a opposite to that mounting the
Alternatively, it is possible to arrange two covers 22, one per side
of the pulley 2.
Of course, the outer shape of the cover 22 can be any one depending
on the requirements. By way of example, in the embodiment shown in figures 3 and
4, where the threaded device 21 has a flattened head 21a, the shape of the cover
is substantially flat. Instead, in the example of figures 1 and 2, the cover 22
has a cupola-like shape and is fitted to house threaded elements having larger
axial overall dimensions.
Always in agreement with the present invention, the engagement of
the cover 22 with the pulley 2 is obtained through hooking means 24 operatively
connected to the cover itself and able to be inserted into corresponding through
engaging openings 25 obtained in the disc-shaped flange 14, as it will better appear
Interconnecting elastic means 26 operate between the hooking means
24 and the cover 22. Preferably, said elastic means 26 are constituted by elastic
tongues extending in a projecting manner from the cover itself and enabling the
hooking means to be inserted with snapping action into the through openings 25
on the radially outer edges 25a.
More particularly, the above said hooking means comprise a plurality
of hooking teeth 24 circumferentially distributed around the axis of the cover
22, each borne by one of the elastic tongue 26, at the end. As clearly visible
in figure 2, each hooking tooth 24 has a substantially wedge-shaped profile, defined
by an inclined guide surface 24a, directed to the opposite part with respect to
the cover 22, to which a stop surface 24b follows; said stop surface 24b being
turned towards the cover itself and oriented in a substantially radial direction
with respect to the axis of this latter. The guide surface 24a and the stop surface
24b meet at an apex 24c spaced from the axis of the cover 22 according to a slightly
larger size than the radial distance of the outer edge 25a of the corresponding
engaging opening 25 with respect to the axis of the pulley 2.
In this way, the application of the cover 22 requires only that this
latter be coaxially pushed against the pulley 2 on the side of this latter where
the cover itself will be engaged. In fact, in said a situation the hooking teeth
24 at the beginning will go to interfere with the radially outer edges 25a of the
engaging openings 25 through the respective inclined guide surfaces 24a. In consequence
of said interference, the hooking teeth 24 will be pushed radially toward the axis
of the cover 22, upon the elastic deformation of the tongues 26, as long as the
apices 24c will have passed over completely the radially outer edges 25a of the
corresponding engaging openings 25. At this point, the elastic action of the tongues
26 will make the hooking teeth 24 click radially towards the outside, so that the
stop surfaces 24b offer to act in abutment relationship against the disc-shaped
flange 14, on the part opposite to the cover 22, to hold this latter axially against
the corresponding side of the pulley 2.
In this situation, the cover 22 will be with its circumferential
connecting portion 23 in engagement relationship with the corresponding terminal
edge 13a of the fastening collar 13, assuring the optimal protection of the bearing
18 from the contact with the impurities coming from outside.
Advantageously, when the pulley 2 rotates at high speed in consequence
of the pulling by the belt 6, the effect of the centrifugal force on the hooking
teeth 24 is such that, thanks to the elastic deformability of the tongues 26,
the interference between the teeth and the outer edges 25a of the openings 25 tends
to be increased of a measure as greater as the rotation speed is higher.
In other words, the effect of the centrifugal force is a bar to the
movement of the teeth 24 towards the axis of the pulley 2 and the cover 22, of
a measure as greater as the rotation speed is higher.
This situation represents an optimal security, since it eliminates
any risk of an accidental release of the cover 22 in consequence of the rotation.
When the pulley is not working, it will be sufficient to act on one
or more of the elastic tongues 22 with the point of a screwdriver or other suitable
tool to obtain the release of the hooking teeth 24 from the disc-shaped flange
14 and the consequent removal of the cover 22 in case of necessity, for instance
to allow the access to the bearing 18 for maintenance operations and/or to remove
the pulley 2.
In a preferred embodiment, the cover 22 is moreover associated to
centering means, constituted for instance by circumferentially distributed centering
pins 27, extending in a projecting manner from the protection cover itself and
arranged to act in opposition relation on the outer cylindrical surface of the
fastening collar 13 so that, during the assemblage, the cover itself is suitably
guided coaxially to the fastening collar. Therefore, it is achieved a further simplification
of the operations of application of the cover 22 on the pulley 2, as well as the
elimination of any possibility to insert the teeth 24 in a not correct position,
with the consequent risk of damaging the teeth themselves and/or the elastic tongues
In the shown example, it is provided that two of said centering pins
27 be placed alongside each elastic tongue 26, symmetrically on opposite parts.
Of course, also the number of hooking teeth 24 and elastic tongues
26, as well as the corresponding openings 25, can be any one depending on the
requirements. In the shown example, there are arranged four hooking teeth 24 and
as many elastic tongues 26 distributed according to an angular pitch of 90 degrees,
arranged to go into the four corresponding engaging openings 25. Alternatively,
it could be possible to use only two hooking teeth 24 and corresponding elastic
tongues 26, arranged in positions diametrally opposite with respect to the axis
of the cover 22 or, preferably, at least three hooking teeth 24 and corresponding
elastic tongues 26, arranged angularly at 120 degrees with respect to the axis
of the cover.
Thus the invention achieves important advantages.
As clearly results from what previously described, the protetion
device forming the object of the present invention is an optimal protection for
the bearing without leaving, on the side of the pulley 2 supporting the cover
22, any space that can constitute an access way for the impurities towards the
Also it is noted that the perfect closing made by the cover 22 on
the terminal edge 13a of the fastening collar 13 enables the cover itself to be
an efficacious means to contain the noise transmitted by the bearing 18 towards
outside, in consequence of the rolling action at high speed.
Thanks to the arrangement of the through openings 25 across the disc-shaped
flange 14, the device forming the object of the present invention permits moreover
to apply the cover on both sides of the pulley, without requiring to this end
any additional elements and/or structural modifications of the same.
Moreover the protection cover can be easily removed from the pulley
in case of need, without that said removal easiness produces risks of accidental
disengagement by the cover itself during the rotation at high speed. In fact,
as it has been seen, the effects of the centrifugal force assure a greater stability
of the connection.
Moreover, it is pointed out that the device forming the object of
the present invention achieves all the above mentioned advantages also maintaining
a very simple and essential structure, realizable at greatly contained costs.
Of course, the invention as herein drawn-up can include numerous
amendments and alternative embodiments, all deriving from the inventive principle
that characterizes the same, which is defined by the claims.