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The present invention relates to a trueing machine for cork
stoppers according to the preamble of claim 1.
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The invention has been conceived in its application to the
trueing of agglomerated cork stoppers and of glued
stoppers, but is also applicable to the trueing of natural
cork stoppers.
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Agglomerated cork stoppers are cylindrical bodies of a
material constituted by milled cork grains bonded by a
suitable adhesive.
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Glued stoppers are composite stoppers constituted by a main
cylindrical component or body of agglomerated cork, which
has at least one disc of valuable natural cork glued to at
least one of its ends.
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Both agglomerated cork stoppers, such as those produced in
suitable moulds or by extrusion, and glued stoppers, such
as those produced by disc glueing machines, as well as
natural cork stoppers, such as those obtained by the
dinking of cork barks, do not have the prescribed nominal
diameter and have a rough surface texture; actually they
are semifinished products which require a finishing or
calibrating step called trueing or turning.
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A machine known from a long time, account of which is given
in the preamble of claim 1, is similar to a lathe in which
every single stopper, while it is rotated around its axis,
is turned between centres by means of a circular blade
whose peripheral cutting edge tangentially engages the
periphery of the stopper.
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This known machine, which is of the handicraft kind and
demands skilled, and therefore expensive, labour, has a low
productivity which is due to the idle times which
correspond to the substitution of every single stopper
between the centres. This machine is therefore quite
inadequate to the present production rates, if only one
thinks that some modern machines for the production of raw
glued stoppers can reach a production rate of some thousand
of stoppers per hour.
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For that reason, such machine has been abandoned in favour
of machines in which the tool is an abrasive disc or an
abrasive tape which operates like the centreless grinding
machines for metal workpieces.
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However, the latter machines, which allow to obtain
stoppers with smooth surfaces of good quality, have the
drawback to produce cork dust polluted by abrasive grains.
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A continuous machine is also known, which avoids both the
aforesaid idle times and the aforesaid pollution due to
abrasive, but which can be used only for the trueing of
cylindrical agglomerated cork bars, before these bars are
severed into sections each having the length of a finished
stopper.
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The known continuous machine, in which the tool is still a
circular blade and in which the bar is fed in the axial
direction, solves the problem to drive the piece into
rotation, the rotation being obtained by means of rollers.
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The main object of the invention is to provide a trueing
machine for cork stoppers which has the advantageous
characteristics of the aforesaid continuous machine, but
which can be used for the continuous trueing of single
stoppers.
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According to the invention this object is attained by means
of a machine as claimed.
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Thanks to the claimed solution, a machine according to the
invention allows to obtain, through the trueing station, a
continuous flow of stoppers which are driven into rotation
one after the other around their axis.
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Each stopper which reaches the trueing station from the
feeding conduit is first seized and centered by the set of
three rotary members of the first assembly, which is
immediately upstream of the circular blade, and is driven
into rotation around its axis and fed onwards by the
corresponding driving wheel.
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Once the rotating stopper has been seized and centered, it
is engaged by the circular blade which removes a layer of a
predetermined thickness all over its length. The trued
portion is then introduced between the rotary members of
the set of three members of the second assembly, which is
immediately downstream of the blade.
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Thanks to the adjustment of the rotary members of the
second assembly, which takes account of the reduction of
diameter of the stopper due to the trueing, the stopper
remains centered on the same axis as before and continues
to be driven into rotation and to be fed onwards, this time
by the driving wheel of the second assembly.
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The invention will be better understood from the reading of
the detailed description which follows, made with reference
to the attached drawings, given by way of not limiting
example, and in which:
- figure 1 is a plan view from above of a machine according
to a preferred embodiment of the invention,
- figure 2 is a lateral elevational view thereof according to
the arrow II of figure 1,
- figure 3 is a partial front view thereof in the plane
indicated with III-III in figure 2,
- figure 4 is a partial cross-section in the plane indicated
with IV-IV in figure 1,
- figure 5 is a partial side view according to the arrow V of
figure 3, and
- figure 6 is a vertical cross-section according to the line
VI - VI of figure 2.
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Referring to figures 1 and 2, the machine shown comprises a
bench B which supports a fixed horizontal table 10 and a
structure which defines a trueing station, generally
indicated 12.
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A tubular feeding conduit 14, which can be better seen in
figures 3 and 5, extends above the table 10 and comes from
a feeder of raw stoppers to be trued, indicated S1, for
example from a vibrating hopper (not shown).
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Preferably, as shown, the feeding conduit 14 and the axis
of the stoppers S1, indicated Z in figure 5, are vertical
and the feeding of the stoppers in the conduit 14 takes
place by gravity.
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The conduit 14 has a lower end which opens onto an upper
region of the trueing station 12.
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The arrangement of the trueing station 12 is more clearly
shown in figures 3, 5 and 6.
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A circular blade 16, located in the trueing station 12, is
carried and rotated by the shaft of an electric motor 18.
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As will be better clarified below, the cutting edge of the
blade 16 engages the peripheral surface of the successive
raw stoppers S1 which come down from the conduit 14 in
order to remove a layer of a predetermined thickness from
the stoppers, as shown for the stopper S2, transforming
them into finished stoppers, indicated S3.
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After the trueing step, the stoppers S3 fall into an
underlying conduit, not shown, which leads to a receptacle
or a conveyor belt.
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The axis of the circular blade 16, indicated A in figures 1
and 2, is askew with respect to the axis of the successive
stoppers S1, S2, S3, in order to obtain that, while the
stoppers are fed downwards, a layer of cork is removed from
their surface in the form of a helical chip, which may be
discontinuous in the most frequent case of the trueing of
agglomerated stoppers.
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Preferably, the circular blade 16 is provided with a
peripheral cutting portion of a sintered agglomerate of
tungsten, molybdenum or tantalum carbides, with cobalt as a
binder, such as Widia®.
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The use of a material such as Widia® or an equivalent
material does not seem to be known in the application to
the trueing of cork stoppers, for which use was made of
circular blades with a cutting edge of special steel which
required frequent regrindings, to the point that the
trueing machines themselves were equipped with a regrinding
device to restore the cutting edge after the trueing of
some hundreds of stoppers.
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It has been found that with the use of a circular blade 16
with a cutting edge of Widia® or an equivalent material,
sharpening of the cutting edge is necessary after the
trueing of a number of stoppers of the order of 800,000.
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The abrasive discs and tapes according to the prior art
produced stoppers of agglomerated cork with ground surfaces
which showed craters with "torn out" edges which were
anything but suitable to guarantee a perfectly tight seal
of the stoppers in the necks of the bottles.
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It has also been found that the use of a circular blade
with a cutting edge of a material such as Widia® allows
instead to obtain trued surfaces of agglomerated cork that,
as different from the prior art, show craters with very
neat edges thanks to which these craters behave as many
suction cups vis-à-vis the glass of the neck of the bottle,
to all advantage of the tightness of the seal.
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The trueing with a circular blade avoids the disadvantage
of the production of cork dust polluted by abrasive grains.
Indeed, the scraps are in the form of chips which can be
reused for the production of articles of agglomerated cork.
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Referrig again to figures 1 and 2, preferably the electric
motor 18 of the circular blade 16 is carried by a slide 22
which can be micrometrically moved towards the stoppers S1,
S2, S3 and in the opposite direction by means of a
handwheel 24 for adjusting the cutting depth of the blade
16.
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A platform 26 is interposed between the slide 22 and the
motor 18 and can be adjusted by means of a handwheel 28 in
order to bring back the circular blade 16 to the tangent
cutting position after each sharpening.
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Referring now more particularly to figures 2, 3, 5 and 6,
the trueing station 12 comprises a pair of assemblies for
driving and centering the stoppers.
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A first assembly or upper assembly, generally indicated
30a, is located immediately before the circular blade 16; a
second assembly or lower assembly, generally indicated 30b,
is located immediately after the circular blade 16.
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Since, preferably, the parts of the two assemblies, the
upper one 30a and the lower one 30b, are identical or
substantially such, in the description which follows and in
the drawings they are indicated by the same reference
numerals followed by the letter a for the upper assembly
30a and by the letter b for the lower assembly 30b.
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The upper assembly 30a is located above and the lower
assembly 30b is located under the table 10.
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Each assembly 30a, 30b includes a respective set of three
rotary members which engage the stoppers S1, S2, S3,
respectively, according to generatrices arranged like the
vertexes of a triangle.
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One of these rotary members, 32a and 32b, respectively, is
a motorized driving wheel, having an axis which is inclined
with respect to the axis Z of the stoppers S1, S2, S3.
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Each driving wheel 32a, 32b drives into rotation the raw
stoppers S1 and the finished stoppers S3, respectively, as
well as a stopper S2 which is being trued, and is rotated
by a respective asynchronous electric motor 34a, 34b
(figure 2) in such a direction as to feed the stoppers
along their common axis Z.
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The distance between the two driving wheels 32a, 32b in the
direction Z is chosen smaller than the length of the
stoppers, so as to make sure that a stopper S1 to be trued,
a stopper S2 which is being trued, and a stopper S3 which
has just been trued are always engaged by the periphery of
one of these wheels.
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Each driving wheel 32a, 32b is preferably provided with a
rim of a slightly abrasive material in order to ensure the
revolving friction for driving the stoppers S1, S2, S3 both
into rotation and translation.
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The other two rotary members of each set of three are a
pair of idle, cylindrical and smooth, pressure rollers 36a,
36b, respectively, of small diameter, also visible in
figure 1.
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The axes of all the pressure rollers 36a, 36b are parallel
to the axis Z of the stoppers S1, S2, S3. The axial length,
in the direction Z, of the rollers 36a, 36b is
substantially equal to the axial height of the respective
driving wheel 30a, 30b, so as to make sure that a stopper
S1 to be trued, a stopper S2 which is being trued, and a
stopper S3 which has just been trued are always engaged
also by the pressure rollers 36a and/or 36b.
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The three rotary members 32a, 36a and 32b, 36b of each
assembly 30a, 30b are interconnected by a respective self-centering
linkage, generally indicated 38a for the upper
linkage and 38b for the lower linkage in figure 3.
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Each self-centering linkage 38a, 38b is provided with
adjusting means which are so arranged that in the trueing
station 12 the axis Z of each stopper S1, S2, S3 remains
the same before, during and after the trueing.
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To this purpose, preferably, the motorized driving wheel
32a, 32b of each assembly 30a, 30b is carried by a
respective slide 40a, 40b (figure 2) whose position is
adjustable, independently from the other slide, in a
horizontal direction X, perpendicular to the axis Z of the
stoppers S1, S2, S3.
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A device for adjusting the position of the slides 40a, 40b
will be described more below.
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Each self-centering linkage 38a, 38b preferably includes
(figures 1, 2 and 3) a respective pair of rocking levers
42a, 42b each of which is fulcrumed at 46 on the table 10
around a respective fixed axis which is parallel to the
axis Z of the stoppers S1, S2, S3.
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One arm 44a, 44b of each rocking lever 42a, 42b is linked
to the respective slide 40a, 40b by a respective connecting
rod 48a, 48b of adjustable length, while the other arm 46a,
46b of the lever 42a, 42b carries the respective pressure
roller 36a, 36b.
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The levers 42a, 42b of each linkage 38a, 38b are specularly
arranged with respect to a median plane containing the axis
Z of the stoppers S1, S2, S3 and passing through the centre
of the corresponding driving wheel 32a, 32b.
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Referring especially to figure 2, a respective thrust
regulator for the respective driving wheel 32a, 32b is
associated to the slide 40a, 40b of each assembly 30a, 30b.
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The two thrust regulators, generally indicated 50a and 50b,
respectively, are independent from each other.
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Each thrust regulator 50a, 50b includes a respective
pneumatic actuator 52a, 52b with a respective piston rod
54a, 54b which is connected to the corresponding slide 40a,
40b in the manner which will be described below, and which
biases the slide towards the stoppers S1, S3.
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The two actuators 52a, 52b are fed with compressed air
through a common pressure regulator, diagrammatically shown
in dotted lines at 55.
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The rod 54a, 54b of each actuator 52a, 52b has associated
thereto a respective micrometric adjustment device for
adjusting the end position of the corresponding slide 40a,
40b according to the diameter of the raw stoppers S1 and
the finished stoppers S3, respectively.
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Figure 2 shows respective handwheels, indicated 56a, 56b,
for the micrometric adjustment of the end position of the
upper slide 40a and the lower slide 40b, respectively.
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Each handwheel 56a, 56b is fast with a respective toothed
crown 57a, 57b having an inner toothing in mesh with the
outer toothing of a respective tubular pinion 58a, 58b.
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Each pinion 58a, 58b has an inner thread having the
function of a nut, which is in engagement with a
corresponding threaded rear section of the rod 54a, 54b of
a respective actuator 52a, 52b.
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Therefore, the rotations of the handwheels 56a, 56b in one
direction and the other are converted into micrometric
linear to-and-fro movements of the piston rods 54a, 54b.
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As will be understood, since the two driving wheels 32a,
32b have the same diameter, if they were rotated at the
same angular speed the upper wheel 32a would rotate the raw
stoppers S1 at an angular speed lower than that at which
the lower wheel 32b rotates the stoppers S3, whose diameter
has been reduced by the trueing.
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This difference in rotation speed is undesirable:
referring especially to figure 2, each driving wheel 32a,
32b is driven by the respective asynchronous electric motor
34a, 34b through a respective 90° reduction gear 60a, 60b
and from an electrical circuit (not shown) which allows the
speeds of the two asynchronous motors 34a, 34b to be
automatically adjusted in such a manner as to impart to all
the stoppers S1, S2, S3 the same speed of rotation before,
during and after the trueing.
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Preferably, the inclination of the driving wheels 32a, 32b
is adjustable in order to allow to regulate the feed rate
of the stoppers S1, S2, S3 according to the requirements.
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The inclined attitude taken by the driving wheels 32a, 32b
is better shown in Figure 6.
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A system for adjusting the inclination of the driving
wheels 32a, 32b will be now described with specific
reference to figure 4, as well as to figure 2 as far as
regards the upper components indicated by reference
numerals followed by the suffix a.
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Each slide 40a, 40b has a pair of brackets affixed thereto,
62a, 62b, respectively, each of which pairs is supported by
a respective horizontal, revolving and sliding shaft 64a,
64b which constitutes an extension of a respective piston
rod 54a, 54b.
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Each of the slides 40a, 40b is provided with a respective
orthogonal pivot pin 66a, 66b.
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The table 10 carries a lateral turret 68 in which a
vertical nut 70 is fixed, which is in engagement with a
vertical threaded shaft 72.
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The micrometric rotation of the nut 70 can be obtained,
through a bevel gear pair 74, from a handwheel 76.
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Each pivot pin 66a, 66b is connected to the threaded shaft
72 through a respective telescopic connecting rod 78a, 78b.
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One end of each telescopic connecting rod 78a, 78b is
articulated to the respective pivot pin 66a, 66b by means
of a bushing 80a, 80b, preferably of the ball-type, and its
other end is coupled to the threaded shaft 72 by means of a
respective ear 82a, 82b.
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Each ear 82a, 82b is imprisoned between two nuts, 84a and
84b, respectively, which prevent them from sliding along
the shaft 72.
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The adjusting system of figure 4 allows to adjust in unison
the inclination of the two driving wheels 32a, 32b from the
handwheel 76; by rotating the handwheel 76 by hand in one
direction or the other, the two bushings 80a, 80b and the
two pivot pins 66a, 66b are raised and lowered jointly,
whereby the respective slides 40a, 40b and the two driving
wheels 32a, 32b are rotated in unison, through the
respective pivot pins 66a, 66b, according to the double
arrows G of figures 4 an 6.
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The possibility of varying of the length of the telescopic
connecting rods 78b, 78b and the possibility of rotating
the bushings 80a, 80b around the pivot pins 66a, 66b allow
to take up the geometric variations of the system due to
the adjustment movements imparted to the slides 40a, 40b in
the direction X of figure 2.
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Moreover, by modifying the positions of the ears 82a, 82b
along the threaded shaft 72 by the manipulation of the nuts
84a, 84b, it is possible to adjust the geometry of the
system in such a manner that the two driving wheels 32a,
32b have the same inclination, or different inclinations,
if this is deemed convenient.
