U.S. patent application number 12/929422 was filed with the patent office on 2012-07-26 for ventilating insert for abrasive tools.
Invention is credited to Giovanni Ficai.
Application Number | 20120190279 12/929422 |
Document ID | / |
Family ID | 46544503 |
Filed Date | 2012-07-26 |
United States Patent
Application |
20120190279 |
Kind Code |
A1 |
Ficai; Giovanni |
July 26, 2012 |
Ventilating insert for abrasive tools
Abstract
A ventilating insert for the substantially coaxial fixing of
abrasive tools, such as deburring wheels, cutting wheels, fiber
discs, Scotch-Brite.RTM. having an abrasive disk-like element, to
the free end of a rotating shaft of a grinder, comprising at least
one threaded ring for coupling to the free end of the rotating
shaft, an annular portion of which is jointly associated with the
disk-shaped element, the threaded ring comprising a central
threaded hole and being designed to be arranged substantially
coaxially with the disk-shaped element and able to be associated
with corresponding threaded elements provided on the free end of
the rotating shaft. The ventilating insert comprises deflectors for
at least one fluid for cooling the disk-like element which are
associated with the threaded ring for propelling radially the
cooling fluid from the central to the peripheral region of the
disk-like element during the rotation thereof.
Inventors: |
Ficai; Giovanni;
(Collecchio, Fraz. OZZANO TARO, IT) |
Family ID: |
46544503 |
Appl. No.: |
12/929422 |
Filed: |
January 24, 2011 |
Current U.S.
Class: |
451/442 |
Current CPC
Class: |
B24D 7/16 20130101; B24D
7/10 20130101; B24D 5/10 20130101; B24D 5/16 20130101 |
Class at
Publication: |
451/442 |
International
Class: |
B24B 55/00 20060101
B24B055/00 |
Claims
1. A ventilating insert for substantially coaxial fixing of
abrasive tools, such as deburring wheels, cutting wheels, fiber
discs, Scotch-Brite.RTM. discs or tools, having an abrasive
disk-shaped element, to a free end of a rotating shaft of a
grinder, comprising: at least one threaded ring that comprises a
central threaded hole for coupling with corresponding threaded
means provided on a free end of a rotating shaft, said threaded
ring having an annular portion which is jointly associatable with
the disk-shaped element, arranged substantially coaxially thereto;
and deflecting means for deflecting at least one fluid for cooling
the disk-shaped element which are associated with said threaded
ring for propelling radially the cooling fluid from a central
region to a peripheral region of the disk-shaped element during
rotation thereof.
2. The insert of claim 1, wherein said deflecting means comprise a
plurality of vanes that protrude substantially radially and diverge
with respect to each other, at least one first end of said vanes
being jointly associated with said threaded ring.
3. The insert of claim 2, wherein each one of said vanes comprises
a substantially rectilinear longitudinal extension which protrudes
radially with respect to said threaded ring.
4. The insert of claim 2, wherein each one of said vanes comprises
a substantially C-shaped curved longitudinal extension which forms
a deflector of the flow of said cooling fluid.
5. The insert of claim 2, wherein said threaded ring comprises a
substantially cup-shaped portion, which surrounds said central
threaded hole and is arranged opposite said annular portion, said
vanes being formed at said substantially cup-shaped portion.
6. The insert of claim 2, wherein a second end of each one of said
vanes is provided so that it substantially cantilevers out with
respect to said threaded ring.
7. The insert of claim 6, wherein at least one annular flange which
is substantially continuous and coaxial with said threaded ring,
for connecting said vanes, whose outside radius is substantially
equal to a distance between the second ends of said vanes and a
rotation axis of said threaded ring, and whose inside diameter is
substantially larger than said central threaded hole, said annular
flange being jointly associated with said second ends of said
vanes.
8. The insert of claim 7, wherein a connecting surface between each
pair of contiguous ones of said vanes, provided in said threaded
ring, has a substantially frustum-shaped generatrix in a proximal
region, with a longitudinal axis that is substantially inclined
with respect to the rotation axis of said threaded ring.
9. The insert of claim 1, in combination with an abrasive tool
having an abrasive disk-shaped element, wherein the disk-shaped
element comprises through openings provided at a substantially
central portion thereof for outflow of the cooling fluid at a back
part of the disk-like element.
Description
[0001] The present invention relates to a ventilating insert for
abrasive tools designed to be installed on sanding machines.
BACKGROUND OF THE INVENTION
[0002] There are various types of abrasive tools designed to be
installed on portable machines. The most widespread among them are:
abrasive deburring wheels and abrasive cutting discs with resinoid
binder, for example of the high-speed type to be used on portable
sanding machines with diameters that vary from 100 mm to 230 mm,
lamellar discs, Scotch-Brite.RTM. discs, fiber discs, etcetera.
[0003] All these tools have in common that they are installed on a
sanding machine or polishing machine and turned to apply their
abrasive action or cutting action.
[0004] An abrasive deburring wheel, for example, consists of a disk
provided by a mixture of abrasive grains, binding resins and
fillers, which is mounted on an adapted grinder, commonly known as
a sanding machine, is rotated about its own axis and then placed in
contact with the part to be ground, or vice versa.
[0005] In order to be able to mount the grinding wheel, sanding
machines usually have a rotating shaft that is provided with a
centering system, an abutment shoulder, a thread at the free end
and two fastening flanges.
[0006] One of these two flanges is fitted on the sanding machine
shaft and engages the shoulder and the centering system thereof.
The other flange is instead provided with a central threaded hole
and is screwed onto the shaft. The grinding wheel, in working
conditions, is interposed between these two flanges and is firmly
fixed thereto by screwing the threaded flange on the sanding
machine shaft with a certain strength. Finally, the grinding wheel
is kept concentric with the shaft by means of two centering
protrusions formed on the faces of the flanges that are in direct
contact with the grinding wheel. These protrusions enter a few
millimeters into the central hole of the grinding wheel and ensure
its perfect centering.
[0007] Deburring wheels can have various cross-sectional shapes
which are specified by the EN12413 standard; the most common ones
are the flat one and the one with depressed center, but there are
also tapered ones or saucer-shaped ones. All of them, anyway, are
mounted on sanding machines in a manner substantially similar to
the one described above.
[0008] Abrasive grinding wheels of the flat or depressed-center
disc-like type are known and described in detail in Italian patent
no. 1,361,563 and comprise a disk-like abrasive and/or cutting
element that can be associated coaxially with the free end of the
rotating shaft of a grinder and is provided with a substantially
central through hole, with a first face which can be positioned, in
the mounting configuration, so that it substantially faces the
grinder and is in contact with a supporting flange of the machine
itself, and with a second face which lies opposite to the first one
where a threaded ring for coupling to the free end of the rotating
is jointly connected to the substantially central portion of the
second face.
[0009] These abrasive deburring wheels are substantially
constituted by an abrasive mix reinforced by reinforcements
constituted by one or more nets made of fabric, by one or two
optional annular elements made of metal or plastic material,
commonly known as washers or rings, which delimit the hole for the
coupling of the grinding wheel to the pivot of the grinder, and by
an optional paper label, which adheres to one of the two faces of
the grinding wheel (usually the convex one).
[0010] The abrasive mix is generally made of grains of abrasive
material (silicon carbide, corundum, zirconium-modified corundum,
and others) of predefined particle size (usually measured in
meshes), which are mixed with resins and some additives. The resins
are generally phenolic-based, in liquid and/or in powder form.
Optionally, they can be modified with rubbers, epoxy resins and/or
others, or with organic and/or vegetable or synthetic
compounds.
[0011] The purpose of the reinforcement nets is to reinforce the
structure of the grinding wheel and to allow its use at high
rotation rates in complete safety. The high rotation rate is
desired because the abrasive action is faster and work is performed
more rapidly. However, high speeds involve high centrifugal forces
and high tensions inside the body of the grinding wheel. In order
to be able to withstand these high tensions, one therefore uses
these reinforcement nets made of materials with high breaking
strength. Generally, these nets are woven with glass fiber yarns,
but it is also possible to use other types of high-strength fibers
such as carbon fiber, Kevlar.RTM. or others; these nets, before
being used in grinding wheels, are usually impregnated with resin,
normally of the same type as the one used in the abrasive mix. The
purpose of this operation is to achieve better adhesion between the
net yarn and the abrasive mix itself, thus increasing the strength
of the manufactured article. Finally, the nets are die-cut so as to
obtain a shape (usually a round one) that is convenient for
placement inside the grinding wheel.
[0012] The labels are usually made of paper but also of tin foil or
other synthetic material, have an annular shape and bear the
identification and informational data of the grinding wheel.
[0013] These grinding wheels of the known type, however, are not
free from drawbacks, including the fact that during the deburring
operation the friction between such grinding wheel and the
workpiece generates a considerable amount of heat, which leads to
an overheating of both the workpiece and the grinding wheel.
[0014] This overheating can reach such high temperatures that the
resin of which the grinding wheel itself is composed breaks down.
The resin thus loses its strength and causes the release of the
abrasive grains and thus the wear of such grinding wheel. Moreover,
this overheating can be harmful also for the workpiece, because it
causes damaging effects of various types, such as:
[0015] burns and pitting with consequent bluish coloring of the
surface of the metal piece, a phenomenon that is particularly
unwanted for pieces made of stainless steel where visual appearance
also is particularly important;
[0016] burns in wood or plastic materials;
[0017] drip melting in low-melting metals or in plastics;
[0018] modification of the crystalline structure of the metal in
the case of self-hardening steels;
[0019] modification of physical and chemical characteristics in
general for all materials that poorly tolerate high
temperatures.
[0020] All of the above statements apply also in the case of
lamellar discs, fiber discs, Scotch-Brite.RTM. discs or other
abrasive tools.
[0021] Lamellar discs, for example, are composed of a circular
supporting plate onto which flaps of abrasive cloth are glued.
Abrasive cloth is a fabric (usually made of cotton or polyester) on
which a thin layer of grains of abrasive material is fixed. The
grains are fixed by spraying the fabric with resin, spreading the
abrasive grains over it and finally polymerizing the resin. The
flaps are obtained from the abrasive cloth by cutting strips of
suitable width and finally cutting the individual flaps from the
strips. Each flap rests on the supporting plate (already covered
with glue or resin) so as to form an annular pack of flaps.
[0022] During use of the lamellar disc, as occurs for abrasive
grinding wheels, a large amount of heat is produced and the
temperature of the flaps and of the workpiece increases rapidly. At
high temperatures the cotton (or synthetic fiber) of the abrasive
cloth burns or melts, and the resin that holds the abrasive grains
breaks down. All this entails wear of the abrasive material of the
lamellar disc.
[0023] Moreover, the workpiece is affected by the same drawbacks
caused by the heat which are described above for abrasive grinding
wheels.
[0024] Fiber discs are simply pieces of abrasive cloth (sometimes
paper) made in a manner similar to cloth for lamellar discs but
die-cut to a circular shape.
[0025] The fiber disc is fixed to a supporting plate (which in turn
is fixed to the rotating shaft of the sanding machine) mainly in
two ways: [0026] a. The abrasive cloth on the face opposite to the
abrasive part has a fabric made of Velcro.RTM. and the supporting
plate has the corresponding component for the Velcro.RTM.. The
cloth is thus simply held to the plate by the effect of the
Velcro.RTM.. [0027] b. The center of the fiber disc has a hole that
allows the passage of the sanding machine shaft. A threaded flange
screwed to said shaft fixes the fiber disc to the back support.
[0028] In both cases, when the fiber disc is put to work it
generates heat that breaks down the resin of the abrasive cloth,
releasing the abrasive grains and causing wear of said fiber
disc.
[0029] Scotch-Brite.RTM. discs are composed of a disc of abrasive
material and a supporting plate. The supporting plate is generally
made of fiberboard or plastic. The disc of abrasive material is
instead composed of Scotch-Brite.RTM., i.e., a material composed of
nylon filaments in the matrix of which small abrasive grains are
embedded.
[0030] Scotch-Brite.RTM. is produced by dropping onto a surface
melted nylon filaments mixed with abrasive grains according to a
random arrangement.
[0031] When the filament touches the surface it is already nearly
solid and keeps the shape of a filament. Deposition continues until
the desired thickness of the fabric is obtained and the finished
product is therefore a lamina of filaments arranged in a random and
disorderly manner.
[0032] This layer thus obtained is then die-cut and used for
various applications. In the case of interest of the present
description, the flap of Scotch-Brite.RTM. is die-cut so as to have
a circular shape and is glued to the supporting plate.
[0033] The plate with Scotch-Brite.RTM. is perforated at the center
and is mounted on sanding machines like an abrasive grinding wheel
by fixing it between the two flanges, i.e., the abutment flange and
the threaded fastening flange.
[0034] In this case also, when the tool made of Scotch-Brite.RTM.
is working, the heat that is developed can reach the point of
melting the nylon of which is composed, causing the release of
abrasive grains without said grains having worked.
[0035] Scotch-Brite.RTM. tools must even be used at lower
peripheral speeds than abrasive grinding wheels; otherwise the
generated heat would be too high and the nylon would melt
immediately.
[0036] As is apparent, in all the cases described above the heat
generated by the abrasive action causes a more or less quick wear
of the tool and harmful overheating of the material that is being
worked.
SUMMARY OF THE INVENTION
[0037] The aim of the present invention is to eliminate the
drawbacks noted above of the background art, by devising a
ventilating insert that makes it possible to reduce the consumption
of abrasive material, thus increasing its performance and average
life.
[0038] Within this aim, an object of the invention is to allow the
working of pieces without damaging their finish and their aesthetic
appearance or altering their physical and chemical
characteristics.
[0039] Another object of the present invention is to provide a
structure that is simple, relatively easy to provide in practice,
safe to use, effective in operation, as well as relatively
inexpensive.
[0040] This aim and these and other objects which will become
better apparent hereinafter are achieved by the present ventilating
insert for the substantially coaxial fixing of abrasive tools, such
as deburring wheels, cutting wheels, fiber discs, Scotch-Brite.RTM.
discs or tools that otherwise can be related to an abrasive
disk-like element, to the free end of a rotating shaft of a
grinder, comprising: [0041] at least one threaded ring for coupling
to said free end of said rotating shaft, an annular portion of
which is jointly associated with said disk-like element, said
threaded ring comprising a central threaded hole and being designed
to be arranged substantially coaxially with said disk-like element
and able to associated with corresponding threaded means provided
on said free end of said rotating shaft, [0042] characterized in
that it comprises means for deflecting at least one fluid for
cooling said disk-like element which are associated with said
threaded ring for propelling radially said cooling fluid from the
central region to the peripheral region of said disk-like element
during the rotation thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0043] Further characteristics and advantages of the present
invention will become better apparent from the following detailed
description of a preferred but not exclusive embodiment of a
ventilating insert, illustrated by way of non-limiting example in
the accompanying drawings, wherein:
[0044] FIG. 1 is a sectional side view of a detail of an abrasive
grinding wheel, according to the invention;
[0045] FIG. 2a is a plan view of the threaded ventilating insert of
the grinding wheel of FIG. 1 in the variation with curved
vanes;
[0046] FIG. 2b is a plan view of the threaded ventilating insert of
the grinding wheel of FIG. 1 in the variation with straight
vanes;
[0047] FIG. 3 is a sectional side view of a detail of an
alternative embodiment of a grinding wheel with ventilating insert,
according to the invention;
[0048] FIG. 4 is a plan view of the threaded ventilating insert of
the grinding wheel of FIG. 3;
[0049] FIGS. 5, 6 and 7 are sectional side views of further
alternative embodiments of a ventilating insert according to the
invention, which can be assembled at will on many conventional
abrasive grinding wheels;
[0050] FIG. 8 is a sectional side view of a further alternative
embodiment of a ventilating insert according to the invention;
[0051] FIG. 9 is a sectional view showing only the ventilating
insert of FIG. 8;
[0052] FIG. 10 is a sectional side view of a further alternative
embodiment of a ventilating insert according to the invention;
[0053] FIG. 11 is a sectional side view showing only the
ventilating insert of FIG. 10;
[0054] FIGS. 12a and 12b are respectively a sectional side view and
a plan view of a further alternative embodiment of a ventilating
insert, according to the invention;
[0055] FIGS. 13a and 13b are respectively a sectional side view and
a plan view of a preferred embodiment of a ventilating insert,
according to the invention;
[0056] FIGS. 14a and 14b are views of two respective alternative
embodiments of flat grinding wheels with a ventilating insert,
according to the invention, in the configuration for fastening onto
the rotating shaft of a sanding machine;
[0057] FIG. 15 is a sectional side view of a further alternative
embodiment of a grinding wheel with ventilating insert, according
to the invention;
[0058] FIGS. 16a and 16b are respectively a lateral elevation view
and an axonometric view of a further embodiment of a ventilating
insert with inclined vanes, according to the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0059] With reference to the figures, a ventilating insert for the
substantially coaxial fixing of abrasive tools, such as deburring
wheels--generally designated by the reference numeral 1 in the
drawings--, cutting wheels, fiber discs, Scotch-Brite.RTM. discs or
tools that can otherwise be related to a disk-like element 2 of the
abrasive type, can be connected to the free end of a rotating shaft
of a grinder.
[0060] In particular, in the examples shown in the figures,
reference is made to a depressed-center or flat abrasive grinding
wheel 1, provided with a ventilating insert, but said ventilating
insert might also be associated for the axial fixing of fiber
discs, Scotch-Brite.RTM. discs or the like.
[0061] The grinding wheel 1 comprises an abrasive disk-like element
2 for deburring or cutting, which can be associated, in a
substantially coaxial manner, with the free end 3 of a rotating
shaft 4 of a sanding machine.
[0062] The disk-like element 2 is provided with at least one
substantially central through hole 5, a first face 6, which can be
placed (in the assembly configuration) so that it substantially
faces the machine and is in contact with a supporting flange 7 of
the machine itself.
[0063] Moreover, the disk-like element 2 is provided with a second
face 8, which lies opposite the first face 6 and defines the active
face of such grinding wheel (if it is a deburring wheel).
[0064] The ventilating insert comprises at least one threaded ring
9 for attachment to the free end 3 of the rotating shaft 4, an
annular portion 10 of which is jointly associated with the
disk-like element 2, and particularly in the case of the grinding
wheel 1 with the substantially central portion 11 of the second
face 8.
[0065] The threaded ring 9 comprises a central threaded hole 12,
which is substantially coaxial to the disk-like element 2 and can
be coupled to corresponding threaded means 13 provided on the free
end 3 of the rotating shaft itself.
[0066] In particular, for the purposes of the present invention,
the ventilating insert comprises means for deflecting at least one
fluid for cooling the disk-like element 2, which are associated
with the threaded ring 9 and propel radially the cooling fluid from
the central region to the peripheral region of the disk-like
element 2 during the rotation of the abrasive grinding wheel 1.
[0067] The cooling fluid is generally air, which is aspirated by
the deflecting means during the rotation of the grinding wheel 1 in
a direction that is substantially parallel to the axis of rotation
of said grinding wheel, and is propelled in a radial direction by
the same deflecting means.
[0068] Advantageously, the deflecting means comprise a plurality of
vanes 14 that extend substantially radially with respect to the
threaded ring 9 and diverge with respect to each other.
[0069] At least one first end 14a of the vanes 14 is jointly
associated with the threaded ring 9.
[0070] In the embodiments shown in FIGS. 1, 2a and 2b, the vanes 14
extend radially from the central threaded hole 12 to the outer
perimetric rim 15 of the threaded ring 9 and are jointly connected,
at the part directed toward the grinding wheel, to said threaded
ring along the entire longitudinal extension.
[0071] However, the second end 14b of each one of the vanes 14
might be substantially cantilevered, as shown in FIGS. 3 to 16,
with respect to the threaded ring 9.
[0072] Such vanes, in this embodiment, protrude outward from such
threaded ring so as to be substantially cantilevered on the
disk-like element 2, for example extending beyond the outer
perimetric rim 15 of such threaded ring.
[0073] This configuration is particularly visible in a preferred
embodiment of the ventilating insert shown in FIGS. 13a and 13b, in
which the vanes 14 protrude radially and externally with respect to
the threaded ring 9, which has a substantially cylindrical
shape.
[0074] Each one of the vanes 14 can comprise a substantially curved
C-shaped or spiral-shaped longitudinal extension that defines a
deflector for the flow of the cooling fluid, for example, of the
type of a centrifugal fan or the like.
[0075] The threaded ring 9 is, for example, applied to the
disk-like element 2 by interposition of a layer of adhesive
material and/or by mechanical interference between a cylindrical
portion 16 of the threaded ring 9 and the through hole 5. The
threaded ring 9 can in any case be uncoupled from the disk-like
element 2 and coupled thereto only at the time of installation of
the element 2 on the shaft of the sanding machine simply by
screwing it thereon.
[0076] This, in any case, prevents the threaded ring 9 from
separating from the disk-like element 2 during handling, whereas
during use the mechanical transmission of the motion and torque
from the rotating shaft 4 to the grinding wheel 1 is ensured by the
fastening of the grinding wheel against the supporting flange 7 of
the rotating shaft 4.
[0077] This threaded connection allows the self-locking coupling
between said grinding wheel and said rotating shaft, without
thereby requiring lock nuts or similar devices.
[0078] In particular, as is known, the thread of the threaded ring
9 is such that, during the rotation of the rotating shaft 4, the
torques acting on the grinding wheel 1 tend to turn the grinding
wheel in the direction for screwing the threaded ring 9 on the
rotating shaft 4.
[0079] The threaded ring 9, in one embodiment, comprises a
substantially cup-shaped portion, whose concavity is directed
toward the second face 8 of the disk-like element 2.
[0080] The cup-shaped portion surrounds the central threaded hole
12 and is arranged opposite the annular portion 10.
[0081] The vanes 14, advantageously, are defined at said
substantially cup-shaped portion and are such as to protrude from
the bottom thereof.
[0082] Advantageously, the vanes 14 have a height that is
substantially equal to the depth of the cup-shaped portion of said
threaded ring and/or the height of the cylindrical portion 16.
[0083] The vanes 14, moreover, in the region that is proximal to
the central threaded hole, have mutual coupling surfaces for the
optimization, in terms of fluid-dynamics, of the centrifugal thrust
of the cooling fluid.
[0084] In a preferred embodiment, illustrated in FIGS. 13a and 13b,
the vanes have a substantially straight shape and extend radially
so as of protrude from the threaded ring 9; between each contiguous
pair of vanes 14, provided in a cantilevered manner with respect to
the threaded ring 9, the connecting surface between them (provided
on the threaded ring itself) has a substantially frustum-shaped
generatrix with a longitudinal axis that is substantially inclined
with respect to the rotation axis of said threaded ring, the shell
of which extends obliquely, forming a diverging channel along the
entire thickness of said threaded ring.
[0085] This refinement allows an increase in the surface (also in
the central region of the threaded ring 9) that is active in
propelling the cooling fluid of each vane 14 and thus makes it
possible to improve the ventilating effect imparted by the rotation
of such threaded ring.
[0086] With this solution it is possible to obtain very high
ventilation performance levels.
[0087] The vanes 14, moreover, can be provided integrally with the
threaded ring 9 or be jointly associated therewith by means of
fixing elements, heat-sealed, glued or coupled by means of
mechanical joints.
[0088] The disk-like element 2 can have different shapes and
dimensions; in the embodiment of the invention shown in the
figures, for example, the grinding wheel 1 is of the
depressed-center type, i.e., it has a concavity at the central
portion of the second face 8, and the threaded ring 9 is arranged
so as to be substantially recessed within said concave central
portion. In this embodiment the thickness of the disk-like element
2 is such as to allow accommodation inside the through hole 5 of
the cylindrical portion 16 of the threaded ring 9.
[0089] However, the disk-like element 2 might also be substantially
flat and the threaded ring 9 might be arranged so as to protrude
with respect to the second face 8.
[0090] In some cases (cutting discs) the thickness of the grinding
wheel 1 might be particularly limited and might not make it
possible to accommodate inside the central threaded hole 12 all of
the cylindrical portion 16.
[0091] In FIGS. 14a and 14b the threaded ring 9 comprises at least
one cavity 17 at the surface thereof affected by the annular
portion 10 and arranged around the central threaded hole 12, so as
to accommodate the centering rim of the supporting flange 7 of the
rotating shaft 4 for the self-centering of the grinding wheel 1
with respect to the rotation axis of said rotating shaft.
[0092] The threaded ring 9, shown for example in FIGS. 3 to 13 and
15, moreover comprises at least one annular flange 18, which is
substantially continuous and coaxial with the threaded ring 9 for
connecting said vanes, the external radius of which is
substantially equal to the distance between the second end 14b of
each vane 14 and the central rotation axis of the threaded ring 9
and the inside diameter is substantially larger than the diameter
of the central threaded hole 12.
[0093] In the preferred embodiment, shown in FIGS. 13a and 13b, the
annular ring 18 has at least a reduced radial thickness, i.e., the
difference between the external radius and the internal radius
thereof is substantially equal to 1 mm.
[0094] In this embodiment, moreover, the annular ring 18 is
associated with the second ends 14b of the vanes 14 on the same
side where the first ends 14a are associated with the threaded ring
9.
[0095] The annular ring 18 shaped like a thin ring or polygon of
very limited cross-section and having an aerodynamic shape so as
not to interfere with the air flow makes it possible to eliminate
the possibility that these ventilating inserts might become
mutually interlocked in the lines of the vibrating feeders used to
transport them, which would prevent a normal and easy flow
thereof.
[0096] In a further embodiment, illustrated in FIGS. 3 to 12 and in
FIG. 15, the annular flange 18 is jointly associated with the
second ends 14b of the vanes 14 on the side opposite the threaded
ring 9.
[0097] The threaded ring 9 furthermore comprises outflow openings
19 for the cooling fluid, which are interposed between the threaded
ring 9 and the annular flange 18 at the outer perimetric rim 15 of
the threaded ring 9, i.e., in the peripheral region of such
threaded ring, in the region of interposition between the vanes
14.
[0098] The annular flange 18, in this case, makes it possible to
channel in an optimized manner the cooling fluid inside the region
occupied by the vanes 14 and therefore improve the inflow in an
axial direction of the air and consequently the outflow in a radial
direction thereof.
[0099] FIGS. 7 and 6 illustrate some variations of the flange 18
where said flange is bent respectively toward the grinding wheel 1
or outward depending on where one intends to direct the cooling
flow.
[0100] In one embodiment, not shown in the figures, of the grinding
wheel 1 the annular flange 18, for example, may have a
substantially planar portion adapted to be arranged in contact with
a corresponding planar surface provided on the disk-like element 2
and therefore be substantially covered by it.
[0101] In a further possible embodiment of the grinding wheel 1,
such grinding wheel may comprise a plurality of through openings
provided in the disk-like element 2 at the substantially central
portion thereof for the outflow of the cooling fluid, propelled by
the deflecting means during the rotary actuation of said grinding
wheel, at the first face 6 of such disk-like element.
[0102] In a further possible embodiment of the grinding wheel 1
shown in FIGS. 8 and 9, the ventilating insert no longer has a
perforated and threaded cylindrical central part but a thin central
part that can be sandwiched and fastened between the grinding wheel
1 and a fastening flange 20 of the traditional type.
[0103] The vanes jointly connected to this thin part protrude in a
substantially radial direction and can be surmounted or not by the
annular flange 18. In this case there are no constraints for the
type of thread, because it is possible to use the fastening flange
20 that the sanding machine usually has.
[0104] The threaded ring 9 shown in FIGS. 8 and 9 can be free or
fixed, for example by adhesive bonding to the disk-like element
2.
[0105] In a further possible embodiment of the grinding wheel 1
shown in FIGS. 2b, 12b, 13b, the ventilating vanes do not have a
spiral arrangement but are straight. This solution is easier to
provide in practice.
[0106] In a further possible embodiment of the grinding wheel 1
shown in FIGS. 16a and 16b, the vanes 14 are no longer cylindrical
(i.e., they do not extend vertically in a direction that is
parallel to the rotation axis of the grinding wheel 1) but oblique.
This solution, although complex to provide in practice, approaches
more closely the geometry of centrifugal compressors and can
increase the ventilating effect. The inclined position of the vane
14 in fact improves the angle of attack of the cooling fluid that
enters in an axial direction the ventilating insert and is
propelled by it in a radial direction. In this case also, the
insert can be provided with an annular ring 18 or not for
channeling the fluid into the more peripheral region of such
insert.
[0107] The ventilating insert may occupy all the concavity of such
depressed-center grinding wheels because the higher the vanes 14
are, and therefore the more the depression is utilized, the higher
the efficiency of the ventilation. For this purpose the vanes 14
might also protrude from the side of the grinding wheel 1 by a few
millimeters and anyway always with the limitation of not causing
problems of contact with the workpieces when one works with the
grinding wheel slightly inclined or almost flat.
[0108] The vanes may have the most convenient desired height.
[0109] In depressed-center grinding wheels 1 that have deeper
concavities, the problem of making the vanes protrude from the side
of the grinding wheel does not exist, since the cavity is more than
deep enough to provide vanes 14 of sufficient height.
[0110] The vanes 14, furthermore, might be available in a desired
number, from a minimum of 2 until the desired efficiency is
reached. Their thickness is also as desired and they may be
oriented radially as well as deflected in any shape of the
curvilinear type in a left-handed or right-handed direction. They
may be straight or inclined, with a constant or variable
inclination, by any angle.
[0111] Their outside diameter may be of any size, limited only by
the necessity of not interfering with the article to be worked.
These inserts may be also be applied on flat grinding wheels, where
obviously the ventilating insert must protrude from the side of the
grinding wheel. The ventilating insert on the flat grinding wheel
might moreover be mounted on both sides of the grinding wheel if
necessary.
[0112] These ventilating inserts may be made of plastic materials
or of metallic materials. They may be applied to the grinding wheel
both by adhesive bonding and by die-casting or injection molding on
the grinding wheel itself. They may be pre-threaded at the center
or threaded after being mounted or even not threaded at all.
[0113] In practice it has been found that the described invention
achieves the intended aim and objects and in particular the fact is
stressed that the ventilating insert, according to the invention,
allows reducing the wear of the abrasive tool and thus increasing
the performance and the average service life of said grinding
wheels (or lamellar discs or fiber discs or Scotch-Brite.RTM.
discs).
[0114] Moreover, the grinding wheel according to the invention,
provided thus with a ventilating insert, allows working pieces
without damaging their aesthetic finish or altering their physical
and chemical characteristics.
[0115] The invention thus conceived is susceptible of numerous
modifications and variations, all of which are within the scope of
the appended claims.
[0116] All the details may furthermore be replaced with other
technically equivalent elements.
[0117] In practice, the materials used, as well as the contingent
shapes and dimensions, may be any according to requirements without
thereby abandoning the protective scope of the appended claims.
[0118] The disclosures in Italian Patent Application No.
MO2010A000053 from which this application claims priority are
incorporated herein by reference.
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