Title of Invention

EXTRUDER FOR WELDING PLASTIC COMPONENTS

Abstract An extruder (10) for welding plastic components, comprising a front part (11) for plasticizing and ejecting additional plastic welding material, and a rear part (12), for feeding and breaking up a continuous filament (13) made of the additional plastic material. The rear part (12) comprises a feed channel (20) that cooperates with a worm screw (21) for the advancement of the filament (13). The feed channel (20) is delimited by the thread (24) of the worm screw (21) on one side and by a sliding surface (25) for the filament (13) on the opposite side. The distance between the sliding surface (25) and the crest of the thread (24) decreases in the direction in which the filament (13) is fed, in order to provide scoring of increasing depth on the filament (13). The thread (24) comprises at least one discontinuity (28) of the worm that has a sharp discontinuity end (29) for cropping the filament (13) at the scoring.
Full Text EXTRUDER FOR WELDING PLASTIC COMPONENTS
The present invention relates to an extruder for welding plastic
components.
Various methods are known for welding plastic components, such as
for example containment tanks and other types of special article.
One of the most widely used methods is welding with added material
and is performed by means of an extruder composed of a front part, for
plasticizing and ejecting plastic material to be added to the weld, and by a
rear part for feeding and breaking up a continuous filament made of the
additional material.
The front part, for plasticizing and ejection, generally comprises a
plasticizing chamber, inside which the small pieces of plastic filament that
originate from the rear part are melted and moved by means of a screw
feeder toward an ejection nozzle.
Electric resistors for heating and melting the small pieces of filament
are arranged around the plasticizing chamber.
The rear part generally comprises a cylindrical feed chamber, in
which a worm screw is arranged coaxially.
A feed channel is provided between the thread of said worm screw
and the wall of the cylindrical chamber.
The distance between the crest of the thread and the wall of the
cylindrical chamber is shorter than the diameter of the plastic filament and
accordingly the thread engages said filament.
The rotary motion of the worm screw (actuated by an electric motor)
allows the filament to advance inside the feed channel until it reaches the
plasticizing chamber.
At the end of the rear part, substantially at the end of the worm screw,
there are generally elements for cutting the filament into many small pieces
that will feed the plasticizing chamber.
The known extruders described here, although being known and used
extensively on the market, are not free from drawbacks and aspects that can
be improved.
A first drawback is that said cutting elements arranged at the end of
the rear part do not provide uniform filament pieces, and this causes a less
than optimum flow of additional welding material, since said material is not
melted correctly.
A second drawback is linked to the fact that the rotating components,
i.e., the screw feeder and the worm screw, must have a very precise axial
tolerance, since any friction would damage the individual components,
including the element that transmits rotary motion (which, if subjected to
stresses caused by unexpected friction, is easily damaged or becomes noisy
and tends to reduce its operating cycle); it should be noted, in this regard,
that these extruders are subjected to very long and accordingly very
demanding work cycles.
Another drawback is that the first part of the plasticizing chamber
may overheat.
Overheating in this region can lead to an expansion of the rotating
elements beyond the allowed tolerances and to consequent friction and
malfunctions.
The aim of the present invention is to provide an extruder for welding
plastic components that solves the drawbacks noted in known types.
Within this aim, an object of the present invention is to provide an
extruder for welding plastic components that allows to provide small pieces
of filament of additional welding material that have mutually uniform
dimensions.
Another object of the present invention is to provide an extruder for
welding plastic components that allows to ensure a correct axial tolerance of
the rotating elements.
Another object of the present invention is to provide an extruder for
welding plastic components that allows to avoid overheating of the rotating
elements.
Another object of the present invention is to provide an extruder for
welding plastic components that can be manufactured with known systems
and technologies.
This aim and these and other objects that will become better apparent
hereinafter are achieved by an extruder for welding plastic components,
which comprises a front part for plasticizing and ejecting additional plastic
welding material, and a rear part, for feeding and breaking up a continuous
filament made of said plastic material, said rear part comprising at least one
feed channel that cooperates with a worm screw, said at least one feed
channel being delimited by the thread of said worm screw on one side and
by a sliding surface for said filament on the opposite side, said extruder
being characterized in that the distance between said sliding surface and the
crest of said thread decreases in the direction in which said filament is fed,
in order to provide scoring of increasing depth on said filament, said thread
comprising at least one discontinuity of the worm that has a sharp
discontinuity end for cropping said filament at said scoring.
Further characteristics and advantages of the present invention will
become better apparent from the following detailed description of a
preferred but not exclusive embodiment thereof, illustrated by way of non-
limiting example in the accompanying drawings, wherein:
Figure 1 is a partially sectional side view of an extruder according to
the invention;
Figure 2 is an enlarged-scale partially sectional plan view of a portion
of the extruder of Figure 1;
Figure 3 is a transverse sectional view of the extruder, taken along the
line III-III of Figure 2.
With reference to the figures, an extruder for welding plastic
components according to the invention is generally designated by the
reference numeral 10.
The extruder 10 comprises a front part 11, for plasticizing and
ejecting plastic material to be added to the weld, and a rear part 12, for
feeding and breaking up a continuous filament, here designated by the
reference numeral 13, made of the plastic material of the additional welding
material.
The front part 11 comprises a chamber 14 for transferring small
pieces of plastic filament, generally designated by the reference numeral 15,
from the rear part 12 to a melting chamber 16 that is located proximate to an
ejection duct 17.
The transfer chamber 14 is substantially cylindrical and comprises
internally a screw feeder 18, which moves the small filament pieces 15
toward the melting chamber 16 and the ejection duct 17.
The melting chamber 16 comprises electric resistor means 19, which
will be described hereinafter.
The rear part 12, for feeding and breaking up the continuous filament
13, comprises a feed channel 20, which cooperates with a worm screw 21.
The worm screw 21 is rigidly fixed coaxially at the rear end of the
screw feeder 18, and is fixed coaxially to a rotation shaft 22 that protrudes
from a motor drive, for example an electric one (not designated by reference
numerals in the figures for the sake of simplicity), which is embedded in a
casing 23 of the extruder 10; the casing 23 and the motor drive are, for
example, the typical ones of an ordinary portable drill.
It is evident that the motor drive can be of any kind, electrical,
pneumatic, hydraulic, et cetera, depending on the requirements and
applications.
The feed channel 20 is delimited by a thread or thread part 24 of the
worm screw 21 on one side and by a sliding surface 25 for the filament 13
on the opposite side.
The distance between the sliding surface 25 and the crest of the thread
24 decreases in the feeding direction of the filament 13.
5 In particular, in this embodiment, the thread 24 is substantially
cylindrical, while the sliding surface 25 is inclined so as to converge toward
the thread 24 in the feeding direction of the filament 13.
The fact that the distance between the crest of the thread 24 and the
sliding surface 25 decreases in the feeding direction of the filament 13
) causes the filament 13 to be scored by the worms.
The rotary motion of the worm screw 21 causes the advancement of
the filament 13 and the scoring increases in depth as the filament advances.
In order to optimize the advancement of the filament 13, a shoulder
26 for guiding the filament 13 is formed on the sliding surface 25 and
contrasts the lateral thrust produced by the rotation of the worm screw 21.
The thread 24 is composed of, or has, in this embodiment, two
separate worm starts 24a and 24b, which are mutually parallel.
The depth of the roots of the thread 24 is greater than the diameter of
the filament that can be used in the extruder.
Advantageously, the thread 24 comprises discontinuities or
interruption zones 28 of the thread with the starts 24a and 24b.
These discontinuities 28 are formed on the extension of the thread 24
along a common continuous line that is transverse to said thread and with a
preset pitch.
Each discontinuity 28 has a sharp discontinuity end for cropping the
thread 13 at the scoring produced during advancement.
When, during the rotation of the worm screw 21, the filament 13
encounters the first discontinuity 28 of the thread 24, said filament tends to
move toward the rotation axis of the worm screw 21, since the pressure
applied in that point by the thread is not present.
Accordingly, since the depth of the roots of the thread 24 is greater
than the diameter of the filament 13, said filament, by moving toward the
axis, enters fully the root of the thread 24; in this manner, a sharp
discontinuity end 29 of the first discontinuity 28, by rotating, crops the part
of the filament 13 that is not scored.
If for any reason (flash of the filament, unexpected slippages,
unexpected stretching, less than optimum previous scoring, dirt, et cetera),
the sharp discontinuity end 29 does not crop the filament 13 with the first of
the discontinuities 28, cropping can be attempted on the next discontinuity.
The last of the discontinuities 28, not shown in the figures, is formed
on a portion 24c of the thread 24 that does not lie above, i.e. lies away from,
the sliding surface 25 and intersects (or is at least tangent to) an ideal or
imaginary continuation surface of the sliding surface 25.
The roots of the thread 24, in this embodiment, have a square cross-
section, while the crests have a sawtooth cross-section.
A thread of this type can be provided, for example, by superimposing
two successive machining operations: a first milling with a square-head
tool, superimposed on a more superficial milling with a sawtooth plate.
As regards the overall structure of the rear part 12, it comprises a
cylindrical sleeve 33, which is associated with the casing 23 coaxially to the
rotation axis of the rotation shaft 22 of the motor drive.
On the bottom of the cylindrical sleeve 33 there is an axial conical
roller bearing 44, on which the rotation shaft 22 that protrudes from the
motor drive is keyed.
A tubular bush 45 is arranged adjacent to the inner walls of the
cylindrical sleeve 33 and forms a rotation chamber 27 for the worm screw
21.
The tubular bush 45 forms a longitudinal space 46 for the insertion of
a block 47 on which the sliding surface 25 and the shoulder 26 are formed.
A duct 48 for access of the filament 13 to the feed channel 20 is
formed in the block 47.
Since the worm screw 21 is rigidly and coaxially fixed at the rear end
of the screw feeder 18, and since said screw feeder is fixed coaxially to the
rotation shaft 22, the rotation axis of the screw feeder 18 coincides with the
axis of the rotation shaft 22 and therefore with the conical roller-type axial
bearing 44.
As regards the front part 11, it is constituted by a tubular body 49, in
which the transfer chamber 14 and part of the melting chamber 16 are
formed.
The transfer chamber 14 is substantially cylindrical and comprises
internally the screw feeder 18 that moves the small pieces of filament 15
toward the melting chamber 16 and the ejection duct 17.
Advantageously, the transfer chamber 14 comprises heat dissipation
means 50, which are constituted by heat dissipation fins 51 formed on the
outer surface of the transfer chamber 14.
The melting chamber 16 is constituted by the end part of the tubular
body 49, to which an end cap 52 is coupled; the ejection duct 17 is further
formed on the end cap 52.
The melting chamber 16, as mentioned, comprises electric resistor
means 19, which are advantageously constituted by a helical resistor 53, of
the type known commercially by the name "Rotfil", which is coaxial to the
melting chamber 16.
A heating fan 54 is arranged on the upper part of the casing 23, and
its output duct 55 is connected, by means of a tube 56, to an output
connector 57, which is arranged proximate to an injection nozzle 58 of the
extruder 10.
The heating fan 54 allows to heat the parts of the components to be
welded that are in mutual contact.
In practice, it has been found that the invention thus described solves
the problems noted in known types of extruder for welding plastic
components; in particular, the present invention provides an extruder for
welding plastic components that allows to extrude extremely uniform
additional welding material.
The scoring formed on the fed filament by means of the worm screw
and the subsequent cropping at said scoring due to the discontinuities of the
thread of said worm screw in fact allow to obtain small pieces of filament
which are regular and which, in the melting chamber, are able to melt in an
optimum manner, obtaining in output from the extruder an extremely
uniform additional welding material, with consequent improved quality of
the weld.
Moreover, the present invention provides an extruder for welding
plastic components that allows to ensure a correct axial tolerance of the
rotating elements.
The use of an axial bearing of the conical roller type in fact allows to
maintain perfectly the axial arrangement of the rotation shaft and therefore
of the rotation elements that are derived from it and coaxial to it. Said
bearing utilizes the contrasting thrust imparted to said bearing that is
generated during the compression of the plastic material while it is
plasticizing. The initial part of the rotation shaft is therefore pushed directly
toward the cone of the bearing.
Moreover, the present invention provides an extruder for welding
plastic components that allows to avoid overheating of the rotating
elements.
The heat dissipation fins provided on the outer surface of the transfer
chamber in fact allow, in a simple and cheap way, optimum heat dissipation
in the main work area of the screw feeder, preventing it from overheating
and also preventing the overheating of the tubular body that forms the
transfer chamber in which the screw feeder acts. In this manner, dangerous
expansions are avoided.
The invention thus conceived is susceptible of numerous
modifications and variations, all of which are within the scope of the
appended claims; all the details may further be replaced with other
technically equivalent elements.
In practice, the materials employed, so long as they are compatible
with the specific use, as well as the dimensions, may be any according to
requirements and to the state of the art.
WE CLAIMS:- CLAIMS
1. An extruder for welding plastic components, comprising a front
part (11) for plasticizing and ejecting additional plastic welding material,
and a rear part (12), for feeding and breaking up a continuous filament (13)
made of said plastic material, said rear part (12) comprising at least one feed
channel (20) that cooperates with a worm screw (21), said at least one feed
channel (20) being delimited by the thread (24) of said worm screw (21) on
one side and by a sliding surface (25) for said filament (13) on the opposite
side, said extruder (10) being characterized in that the distance between said
sliding surface (25) and the crest of said thread (24) decreases in the
direction in which said filament (13) is fed, in order to provide scoring of
increasing depth on said filament (13), said thread (24) comprising at least
one discontinuity (28) of the worm that has a sharp discontinuity end (29)
for cropping said filament (13) at said scoring.
2. The extruder according to claim 1, characterized in that said thread
(24) comprises two separate thread starts (24a, 24b), which are mutually
parallel, said separate thread starts (24a, 24b) having at least two of said at
least one worm discontinuity (29) formed on the extension of said thread
(24c) along a common continuous line that is transverse with respect to said
thread (24).
3. The extruder according to claim 2, characterized in that the last one
of said discontinuities (28) is formed on a portion (24) of said thread (24)
that does not lie above said sliding surface (25) and intersects, or is at least
tangent to, the ideal continuation of said sliding surface (25).
4. The extruder according to one or more of the preceding claims,
characterized in that said thread (24) is substantially cylindrical, while said
sliding surface (25) is inclined so as to converge toward said thread (24) in
the feeding direction of said filament (13).
5. The extruder according to one or more of the preceding claims,
characterized in that a shoulder (26) for guiding said filament (13) is
provided on said sliding surface (25) and contrasts the lateral thrust due to
the rotation of said worm screw (21).
6. The extruder according to one or more of the preceding claims,
characterized in that the roots of said thread (24) have a square cross-
section, while the crests have a sawtooth cross-section, the depth of said
roots of said thread (24) being greater than the diameter of said filament
(13).
7. The extruder according to one or more of the preceding claims,
characterized in that said rear part (12) comprises a sleeve (33), which is
associated with a casing (23) that supports a motor drive for the rotation of
said worm screw (21), a rotation shaft (22) being accommodated in said
sleeve (33), protruding from said motor drive and being rigidly fixed to said
worm screw (21), an axial bearing of the conical roller type (44) being
arranged on the bottom of said cylindrical sleeve (33), said rotation shaft
(22) that protrudes from said motor drive being keyed on said bearing, a
tubular bush (45) being arranged adjacent to the internal walls of said
cylindrical sleeve (33) and forming a rotation chamber (27) for said worm
screw (21), a longitudinal space (46) being formed on said tubular bush (45)
for the insertion of a block (47) on which said sliding surface (25) and said
shoulder (26) are formed, the duct (48) for the access of said filament (13)
to said feed channel (20) being formed in said block (47).
8. The extruder according to one or more of the preceding claims,
characterized in that said front part (11) is constituted by a tubular body
(49), in which there is a transfer chamber (14) for accommodating a screw
feeder (18) for small pieces (15) of said filament (13), and a melting
chamber (16), said transfer chamber (14) comprising heat dissipation means
(50), which are constituted by heat dissipation fins (51) formed on the outer
surface of said transfer chamber (14).
9. The extruder according to one or more of the preceding claims,
characterized in that said front part (11) is constituted by a tubular body
(49), in which there is a melting chamber (16) that comprises electric
resistor means (19) constituted by a helical resistor (53).
10. The extruder according to one or more of the preceding claims,
characterized in that it comprises a heating fan (54), the output duct (55) of
which is connected, by means of a tube (56), to an output connector (57),
which is arranged proximate to the injection nozzle (58) of said extruder
(10).
11. An extruder for welding plastic components, comprising a front
part (11), for plasticizing and ejecting plastic material to be added to the
weld, and a rear part (12), for feeding and breaking up a continuous filament
(13) made of said plastic material, said front part (11) comprising a screw
feeder (18) for the small pieces (15) of plastic filament (13) that arrive from
said rear part (12) toward the ejection duct (17), said extruder (10) being
characterized in that the rotation axis of said screw feeder (18) coincides
with the axis of a rotation shaft (22), which is keyed on an axial bearing of
the conical roller type (44).
12. The extruder for welding plastic components, comprising a front
part (11), for plasticizing and ejecting plastic material to be added to the
weld, and a rear part (12), for feeding and breaking up a continuous filament
(13) made of said plastic material, said front part (11) comprising a transfer
chamber (14) for transferring, by means of a screw feeder (18), small pieces
(15) of plastic filament (13) from said rear part (12) to a melting chamber
(16) that is proximate to the ejection duct (17), said extruder (10) being
characterized in that said transfer chamber (14) comprises heat dissipation
means (19), which are constituted by heat dissipation fins (51) formed on
the outer surface of said transfer chamber (14).
13. The extruder for welding plastic components, comprising a front
part (11), for plasticizing and ejecting plastic material to be added to the
weld, and a rear part (12), for feeding and breaking up a continuous filament
(13) made of said plastic material, said front part (11) comprising a melting
chamber (16) for small pieces (15) of plastic filament (13) that arrive from
said rear part (12), electric resistor means being provided in said melting
chamber (16) for melting said small pieces (15) of filament (13), said
extruder (10) being characterized in that said electric resistor means (19)
comprise a helical resistor (53) of the type known commercially by the name
"Rotfil", which is coaxial to said melting chamber (16).

An extruder (10) for welding plastic components, comprising a front part (11) for plasticizing and ejecting additional plastic welding material,
and a rear part (12), for feeding and breaking up a continuous filament (13) made of the additional plastic material. The rear part (12) comprises a feed channel (20) that cooperates with a worm screw (21) for the advancement of
the filament (13). The feed channel (20) is delimited by the thread (24) of the worm screw (21) on one side and by a sliding surface (25) for the filament (13) on the opposite side. The distance between the sliding surface (25) and the crest of the thread (24) decreases in the direction in which the filament (13) is fed, in order to provide scoring of increasing depth on the filament (13). The thread (24) comprises at least one discontinuity (28) of the worm that has a sharp discontinuity end (29) for cropping the filament (13) at the scoring.

Documents:

732-KOL-2004-ABSTRACT-1.1.pdf

732-kol-2004-abstract.pdf

732-KOL-2004-AMANDED CLAIMS.pdf

732-kol-2004-claims.pdf

732-kol-2004-CORRESPONDENCE 1.1.pdf

732-KOL-2004-CORRESPONDENCE-1.2.pdf

732-kol-2004-correspondence.pdf

732-KOL-2004-DESCRIPTION (COMPLETE)-1.1.pdf

732-kol-2004-description (complete).pdf

732-KOL-2004-DRAWINGS-1.1.pdf

732-kol-2004-drawings.pdf

732-KOL-2004-ENGLISH TRANSLATION.pdf

732-KOL-2004-EXAMINATION REPORT REPLY RECIEVED.pdf

732-KOL-2004-FORM 1-1.1.pdf

732-KOL-2004-FORM 1-1.2.pdf

732-kol-2004-form 1.pdf

732-kol-2004-form 18.pdf

732-KOL-2004-FORM 2-1.1.pdf

732-KOL-2004-FORM 2-1.2.pdf

732-kol-2004-form 2.pdf

732-kol-2004-form 26.pdf

732-KOL-2004-FORM 3-1.1.pdf

732-KOL-2004-FORM 3-1.2.pdf

732-kol-2004-form 3.pdf

732-KOL-2004-FORM 5-1.1.pdf

732-kol-2004-form 5.pdf

732-KOL-2004-OTHERS-1.1.pdf

732-KOL-2004-PETITION UNDER RULE 137-1.1.pdf

732-KOL-2004-PETITION UNDER RULE 137.pdf

732-kol-2004-priority document.pdf

732-kol-2004-specification.pdf

732-kol-2004-translated copy of priority document.pdf


Patent Number 248041
Indian Patent Application Number 732/KOL/2004
PG Journal Number 24/2011
Publication Date 17-Jun-2011
Grant Date 13-Jun-2011
Date of Filing 19-Nov-2004
Name of Patentee RITMO S.P.A.
Applicant Address VIA A. VOLTA, 7, 35037 TEOLO (PROV. OF PADOVA)
Inventors:
# Inventor's Name Inventor's Address
1 RENZO BORTOLI VIA LIVIANA, 88, 35038 TORREGLIA (PROV. OF PADOVA)
PCT International Classification Number B29C 65/20
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 PD2003A000301 2003-12-16 Italy