Title: Blocking device of the unwinding of threads from the feeding bobbins of a double-torque twister
Abstract: Blocking device of the unwinding of the threads from the feeding bobbins of a twisting spindle with superimposed bobbins inserted on their hollow pin, in which the threads are blocked with mechanical interceptors brought into their unwinding range at the entrance of the respective hollow pins and activated by means of sensors of the twisted thread situated downstream of the thread-guide curl.
Patent Number: 6,996,966 Issued on 02/14/2006 to Badiali, et al.
| Inventors:
|
Badiali; Roberto (Pordenone, IT);
Nicodemo; Ruggero (Casarsa, IT);
Ghinami; Giovanni (Fiume Veneto, IT)
|
| Assignee:
|
Savio Macchine Tessili S.p.A. (Pordenone, IT)
|
| Appl. No.:
|
050935 |
| Filed:
|
February 4, 2005 |
Foreign Application Priority Data
| Feb 09, 2004[IT] | MI2004A0201 |
| Current U.S. Class: |
57/58.55; 57/58.83 |
| Current Intern'l Class: |
D01H 1/10 (20060101) |
| Field of Search: |
57/78,88,585.4,585.5,587,588.3
|
References Cited [Referenced By]
U.S. Patent Documents
| 4930301 | Jun., 1990 | Kawarabashi.
| |
| 5220777 | Jun., 1993 | Badiali et al.
| |
| 5291729 | Mar., 1994 | Badiali et al.
| |
| 2002/0000084 | Jan., 2002 | Scheufeld.
| |
Primary Examiner: Welch; Gary L.
Assistant Examiner: Hurley; Shaun R.
Attorney, Agent or Firm: Hedman & Costigan, P.C.
Claims
The invention claimed is:
1. A blocking device of the unwinding of threads (
3,
4) from the
feeding bobbins (
1,
2) of a twisting spindle (F) with coaxially superimposed
bobbins inserted on their own hollow pin (
10,
11), each thread (
3,
4) unwinding upwards from its bobbin and in the same direction as the other
thread, directly entering the hollow pin (
10,
11) without penetrating,
during its run, the space surrounding the other bobbin, characterized in that the
blocking device of the unwinding of the thread (
4) of the lower bobbin (
2)
comprises a mechanical interceptor (
48) integral with the upper hollow pin
(
10), activated with means for activating (
55,
71) for its
descent to enter into the unwinding range of the thread (
4) preventing it
from passing into the lower hollow pin (
11).
2. The blocking device of the unwinding of threads according to claim 1, characterized
in that the blocking device of the unwinding of the thread (
4) of the lower
bobbin (
2) is associated in coordination with the blocking device of the
unwinding of the thread (
3) of the upper bobbin (
1) consisting of
a mechanical interceptor (
59,
77) which enters the unwinding range
and interrupts it, preventing the thread from passing into the upper hollow pin (
10).
3. The blocking device of the unwinding of threads according to claim 2, characterized
in that the activation of the blocking means of the unwinding of the feeding threads
(
3,
4) is controlled by the falling from a mechanical thread-feeler
(
50) of the twisted thread (
5) situated downstream of the thread-guide
curl (
6).
4. The blocking device of the unwinding of threads according to claim 2, characterized
in that the activation of the blocking means of the unwinding of the feeding threads
(
3,
4) is controlled by a sensor (
70) of anomalies of the
twisted thread (
5).
5. The blocking device of the unwinding of threads according to claim 4, characterized
in that the sensor (
70) of anomalies of the twisted thread (
5) is
capable of detecting whether said thread is present and running and also if it
falls within a range of pre-established titer and regularity characteristics.
6. The blocking device of the unwinding of threads according to claim 1, characterized
in that the blocking device of the unwinding of the thread (
4) of the lower
bobbin (
2) consists of one or more elements (
48) protruding downwards,
situated at the bottom of the hooded element (
45), which forms the lower
terminal part of the upper hollow pin (
10), which guide the thread when
the hollow pin
10 is lowered against the top of the lower hollow pin (
11).
7. The blocking device of the unwinding of threads according to claim 6, characterized
in that the upper hollow pin (
10) is produced in several coaxial threaded parts.
8. The blocking device of the unwinding of threads according to claim 1, characterized
in that the system for keeping the upper hollow pin (
10) in a raised position
with respect to its hub (
17) is of the magnetic type, one part being constructed
with ferrous material or inserts and inserting a magnet (
47) in the other part.
9. The blocking device of the unwinding of threads according to claim 3, characterized
in that the activation of the blocking means of the unwinding of the threads (
3,
4) is effected with mechanical coupling in rotation of a thread-feeler (
50)
and an arm (
55) which, on falling, has a weight which is sufficient to press
the upper hollow pin (
10), overcoming the forces that keep it raised and
making it drop until it reaches the top of the lower hollow pin (
11).
10. The blocking device of the unwinding of threads according to claim 9, characterized
in that the rotational coupling of the thread-feeler (
50) and the arm (
55),
causes a pre-established delay between the breakage and/or absence of thread (
5)
and the falling of the arm (
55) to interrupt the unwinding of the threads
(
3,
4) from their feeding bobbins (
1,
2).
11. The blocking device of the unwinding of threads according to claim 4, characterized
in that the activation of the blocking means of the unwinding of the threads (
3,
4) is effected with the association of the sensor (
70) and an arm
(
71), which the sensor causes to fall or keeps it in a raised position in
relation to the thread detected, and the arm (
71), on falling, has a weight
which is sufficient to press the upper hollow pin (
10), overcoming the forces
that keep it raised and making it drop until it reaches the top of the lower hollow
pin (
11).
12. The blocking device of the unwinding of threads according to claim 11, characterized
in that the arm (
71) is maintained in an upper position by a supporting
element (
74) having two alternative controlled positions: an advance position
by protruding to support the resting arm (
71) and a reverse position which
unhooks the arm (
71) allowing it to fall until it reaches the upper hollow
pin (
10).
13. The blocking device of the unwinding of threads according to claim 11, characterized
in that the arm (
71) is equipped in its terminal part with an interception
and interruption element (
77) of the thread.
14. The blocking device of the unwinding of threads according to claim 13, characterized
in that the arm (
71) has a fall run in which it intersects, with the element
(
77), the surface according to which the balloon of twisted thread (
5)
rotates and also intersects the path of the thread (
3) unwound from the
upper bobbin (
1).
Description
The present invention relates to double-torque twisting and more specifically
to controlling the threads fed to the twister.
Twisting operations consist in joining two or more threads by their mutual
twisting around their longitudinal axis, producing a new higher quality thread,
more resistant to traction and abrasion, more regular and with an improved appearance
and feel.
Twisting can be effected by feeding the two or more threads already coupled
and wound parallelly by an assembler, or—according to an industrially more
advanced technology—by taking the single threads from two separate bobbins,
generally conical and superimposed. The present invention can be advantageously
applied in this latter type of twisting, carried out starting from two bobbins
of thread without the intermediate stage of assembling or coupling in an assembler.
For a better understanding of the technical problems relating to twisting, and
of the characteristics and advantages of the technical solution according to the
present invention, it is described herein with reference to a twister fed with
separate threads from two superimposed bobbins of the type already object of the
previous patents EP-B1-417,850 and EP-B1-528,464 of the same applicant, which respectively
relate to the double hollow pin and the alignment process of the two threads at
the start of the twisting operation in one of the twister units. These patents
provide greater details on the twister as a whole.
In order to illustrate the problems and technical solutions associated with double-torque
twisting, the conventional scheme of a twisting station is schematically described,
with reference to FIG. 1, bearing in mind that, in general, double-torque twisters
consist of a series of twisting stations situated abreast of each other forming
the front of the machine.
FIG. 1 refers to the scheme of a twisting spindle F already known according
to the patent EP 417,850 filed by the same applicant: this shows two conical superimposed
bobbins
1 and
2 which feed the twisting with single threads.
The feeding is provided by the upper feeding bobbin
1 and the lower feeding
bobbin
2 with the threads
3 and
4 respectively, which form
a double twisted thread
5 which forms the twisting product. The twisted
thread
5 passes through a thread-guide ring
6 and moves towards the
collecting bobbin of the twisted thread produced which, for the sake of simplicity,
is not illustrated. The rotation rate of said bobbin is kept constant and creates
the linear unwinding rate of the underlying feeding bobbins
1 and
2.
The production rate is in the order of magnitude of tens of linear metres of twisted
thread per minute.
The truncated-conical bobbins
1 and
2 have the conical section
facing upwards, they are centered by hollow, superimposed pins,
10 and
11
respectively, forming the core of the twisting spindle and are contained in two
baskets
13,
14 respectively. The pins
10 and
11 have
circumferential enlargements
15,
16 which, together with the lower
hubs
17 and
18, act as supporting and centering elements of the unwinding
bobbins
1 and
2, or more specifically, their spools
1′
and
2′ respectively. The twisting station is contained in an outer
casing
19 currently called balloon container.
The upper hub
17 is sustained with radial supporting elements
20
which are connected with the basket
13. A suitable bulging
21 of
the upper edge of the underlying basket
14 serves to sustain and center
the upper basket
13.
At the top
22,
23 of each of the two superimposed and coaxial pins
10 and
11 which form the core of the twisting spindle, the two threads
3 and
4 then enter the cavity of the respective pins
10 and
11 and pass through this together as far as the foot of the twisting station
where they meet a tensioning device
31 inside the spindle, already known
in the art, described, for example, in the previous patent EP 528,464 filed by
the same applicant.
At the foot of the twisting station there is a rotating disk
32 equipped
with a radial duct
33 from which the double thread
5 exits and an
edge
34 which guides the thread after its exit.
The rotating disk
32 is the only part activated in movement of the twisting
spindle F and is made to rotate with the pulley
35, which is activated by
tangential transmission with a longitudinal activating belt common to all the stations
F situated on the front of the twister, not shown in the figure, for the sake of simplicity.
In the twisting spindle F so far illustrated, each thread
3,
4
is
unwound from its bobbin
1,
2 and the most frequent anomalies derive
from breakage of the threads. If the twisted thread
5 breaks, its collection
is naturally interrupted, whereas if only one of the threads
1,
2
being fed, break, it is possible for the collecting to continue with the remaining
thread alone.
In both cases, if the spindle F continues to rotate, there is the possibility
that only one or both of the threads being fed can continue to unwind. The quantity
of thread unwound from the bobbins
1,
2 and not twisted with the
thread wound onto the upper collecting bobbin, is wound inside the spindle itself,
breaks and becomes disaggregated, causing a waste of useful material and creating
isolated segments and dust which is harmful for the machine. The thread, which
is no longer controlled, can interfere with and wind itself onto the activation organs.
The removal of this material on the part of the operator requires most of the
intervention time necessary for re-establishing the operating conditions of the
twisting unit.
When the spindle is functioning, whereas it is easy to reach the thread
3
and the upper bobbin
1 and consequently interrupt their unwinding, a direct
intervention due to blockage of the unwinding of the thread
4 is not easy
as a result of the difficulty of reaching the space between the two bobbins
1,
2.
In the known art, further unwinding of the threads is generally indirectly prevented
by stopping the twisting station F. This stoppage is effected by stopping the rotation
of the spindle, thus preventing the threads from being pulled back from the bobbins
due the centrifugal force of the spindle itself, and at the same time by lowering
a feeler of the twisted thread which is situated above the upper bobbin, in the
ascending area of the balloon, so as to interfere with the rising threads, preventing
them from being collected.
The descent of the twisted thread feeler—a technique which is already known—can
take place naturally either by the absence or breakage of the twisted thread itself,
or when the feeding has been reduced to a single thread which is untwisted, and
therefore weakened, in the first part of its run and is not capable of resisting
the stress of the feeler. The descent of the twisted thread feeler can also be
caused by a specific actuator—either mechanical or pneumatic—following
the detection of an anomaly of the characteristics of the twisted thread which
is entrusted to a sensor situated on the collection path, for example with respect
to tension, torque distribution, presence of undesired defects.
The braking of the spindle F—a technique which is already known—requires
a costly complication of the device as it generally requires the following operations,
in sequence:
- detaching the tangential entrainment belt from the pulley 35,
- braking the spindle F with an individual shoe brake on each spindle,
- keeping the spindle F and the belt detached until after the intervention
of the operator.
The whole operation is difficult, and especially for tangential transmission
machines, as there is considerable stress in detaching the belt, which causes an
increase in the tension of the belt with a consequent overloading of the mechanical
organs. This overload is particularly dangerous when intervening on several twisting
spindles F, for example in the lifting operation when all the spindles have been stopped.
The objective of the present invention is to provide a blocking device of both
of the feeding threads to the twisting spindle F, which overcomes the drawbacks
of the available blocking systems of the known art.
This objective is achieved according to the present invention with a direct
blocking device of the feeding of the threads without the necessity of stopping
the twisting spindle.
The most important characteristics of the blocking device of the feeding threads
to the twister are defined in the dependent claim, whereas preferential embodiments
are defined in the dependent claims.
The invention is described hereunder with reference to some embodiments shown
in FIGS. 2 to 6, for purely illustrative but non-limiting purposes, and to clarify
the characteristics and advantages of the present invention referring to the enclosed
schematic drawings.
FIG. 1 shows a perspective view of the twisting spindle F of a twisting station
with the superimposed two feeding bobbins to illustrate the technical problem faced
in the present invention.
FIG. 2 illustrates the configuration of the twisting station in the normal operating
phases with free unwinding of the two feeding bobbins. FIG. 2
bis shows,
as an enlarged detail, the conformation of the upper hollow pin 10. FIG.
2
ter shows, as an enlarged detail, the conformation and functioning of the
thread feeler 50 and organs connected therewith.
FIG. 3 illustrates the behaviour of the thread feeler 50 in the presence
of broken thread, absent or faulty, and 3
bis the conformation of
the arm 55.
FIG. 4, on the other hand, illustrates the configuration of the twisting station
with the breakage of one or more of the threads with the blocking of their unwinding
from the two feeding bobbins.
FIGS. 5 and 6 show an alternative embodiment of the invention; these respectively
illustrate the configuration of the twisting station during normal functioning
and its configuration when an irregularity of the thread 5 occurs, by blockage
of the unwinding of the threads from the two feeding bobbins.
FIG. 2 illustrates the normal functioning of the twisting station. The feeding
consists of two threads
3 and
4, coming from the feeding bobbins
1,
2 situated in the cylindrical baskets
13,
14, which
are each inserted in their unwinding head, consisting of the upper ends
22,
23 of the superimposed pins
10,
11, they pass through their
cavities in series and are twisted in the low part of the spindle F; the double
twisted thread
5 then rises outwardly and upwards where it is collected.
The two threads
3,
4 unwind at the pulling rate of the twisted
thread, spinning around their bobbin and penetrating the tops of their hollow pins
10,
11. In order to limit wear phenomena due to the running of the
thread, these pin tops are protected with smooth rounded metal washers.
The double twisted thread
5 leaves the hole
33 of the rotating
disk
30 spinning rapidly; its balloon is controlled first by the internal
wall of the containment cylinder
19 and then by the thread-guide curl
6;
it is drawn by the pulling exerted by the upper winding bobbin. Said collection
bobbin of the twisted thread
5 is not shown in the figure for the sake of
simplicity. It follows, for example, the known conventional scheme of a bobbin-holder
arm which carries the bobbin, where the twisted thread is wound onto its tube;
it is made to rotate by contact with an activation cylinder which rotates at a
constant rate and which creates the constant pulling rate of the twisted thread
5, starting from the two feeding bobbins
1,
2.
As illustrated in FIG. 2, where it is shown in a longitudinal section, the supporting
structure of the upper bobbin
1 and the upper hollow pin
10 essentially
consists of the upper basket
13, the radial supporting elements
20
on the container basket
14, the centering pin
17 and its upper truncated-conical
part
40, which are integral with each other.
The upper hollow pin
10 is kept in a raised upward position and axially
separated with respect to the lower hollow pin
11. In the known art, this
raising and axial distancing action of the upper hollow pin
10 with respect
to the lower hollow pin is normally entrusted to a coaxial spring system inserted
between said upper hollow pin and the inside of the fixed centering pin
17.
In the illustrative embodiment of FIGS. 2,
2bis and
3, the
truncated-conical part
40 corresponds to a cylindrical cavity
41
coaxial with the hollow pin
10, thus forming a cylindrical guide of the
hollow pin
10 in its axial ranges. Analogously, the hollow pin
10
corresponds to an upper cylindrical part
43, with a coherent dimension for
its guided running from inside the hollow
41, and with a lower larger hood-shaped
cylindrical part
45, as illustrated further on. This cylindrical part
45
has radial dimensions which allow it to run inside the lower cavity of the truncated-conical
part
40, enabling the upper part of its hood
45 to rest on the bottom
of the lower cavity of the truncated-conical part
40.
The conventional coaxial spring lifting system can therefore be inserted into
the cavity
41 around the cylindrical part
43.
According to a preferred embodiment of the invention, these parts are produced
in a form coherent with one another so that, at the run end, they can adhere to
each other. Of the parts which are thus in contact, one is produced with ferromagnetic
characteristics, for example by producing it with ferrous material or inserts,
for example an iron washer
46 integral with the truncated-conical part
40,
and a permanent magnet
47 is inserted in the other part. Once contact has
been established and the hollow pin
10 has reached its upper run end, the
washer
46 and magnet
47 are at a minimum distance and the magnetic
attraction has its maximum value. The possible variations in the tension of unwound
thread are consequently opposed by the magnetic force which withholds the pin at
its run end without harmful vibrations.
This maintenance system in a raised position of the upper hollow pin
10
can also be effected without coaxial springs. In this case, once the lowering of
the upper hollow pin has been completed, its re-lifting must be effected by the
operator who intervenes on the twisting station, until the hood
45 and magnet
47 have been brought back to their upper run end.
As shown in FIG. 2
bis, the hollow pin
10 is produced in several
coaxial threaded parts to allow it to be introduced into its cylindrical guide
consisting of the cavity
41 of the truncated-conical part
40. Various
elements
48, protruding downwards, are situated at the bottom of the hooded
element
45, which guide the thread when the hollow pin
10 is lowered
against the top of the lower hollow pin
11.
As illustrated in FIG. 2, the twisted thread
5 rises upwards in the cylindrical
space between the outer casing
19—no longer shown in the drawing,
for the sake of simplicity—and the two baskets
13,
14, which
contain the two feeding bobbins, and passes through the threadguide ring
6.
Above the thread-guide
6, the thread encounters the thread-feeler
50,
consisting of a lever hinged onto the structure of the twisting station and whose
terminal part
51 rests on the thread running upwards.
FIG. 2
ter shows an enlarged view of the thread-feeler
50 and organs
connected therewith. In the embodiment illustrated, the thread-guide lever
50
has an interrupted run and ends with a contact element
51 with the twisted
thread, consisting of a rod orthogonal to the direction of the thread. The thread-feeler
50 is integral with a pin
52 which rotates inside a short tube
53
equipped with radial openings
54 which allow a certain free rotation with
respect to the thread-feeler lever
50. The short tube
53 is, in turn,
part of a mobile arm rod
55 hinged onto the fixed structure
57, and
capable of coaxially rotating with the thread-feeler lever
50. During normal
functioning, the arm
55 is in an almost vertical position and leaning backwards,
so that its barycentre is pulled slightly back towards the left with respect to
the rotation axis of the short tube
53, which is, in turn, hinged onto the
element
57 of the fixed structure of the machine.
FIG. 3 shows the behaviour of the thread-feeler
50 when the thread
5,
broken, absent or faulty, no longer sustains said thread-feeler, which is consequently
lowered, rotating around its hinge in the short tube
53. In its initial
rotation, the lever of the thread-feeler
50 rotates inside the openings
54 until it comes to a rest with its shoulders which delimit the openings
54 and, with its weight, engages and also forces the short tube
53
to rotate, thus causing the arm
55 to drop, making its barycentre rotate
in a clockwise direction around the short tube
53 according to the arrow
of FIG. 3.
The detail of FIG. 3
bis shows the conformation of the arm
55, in
a perspective view. The body of the arm
55 is produced with a draw piece
and is hinged in a terminal part to the fixed structure
57 with the short
tube
53, which, in turn, also contains and guides the thread-guide
50.
The body of the arm
55 is produced with a weight which is sufficient to
press the upper hollow pin
10, overcoming the elastic and/or magnetic forces
which keep it lifted, making it drop until it rests on the top of the lower hollow
pin
11. A transversal supporting element
58 is inserted, in the body
of the arm
55, on the top
22 of the upper hollow pin
10. A
nib
59 is also inserted on the short tube
53, which established the
run end of the rotation of the arm
55 against shoulder elements, not shown
in the figure for the sake of simplicity.
The configuration of the thread-feeler
50 and arm
55, coupled with
the rotation pin
52 which rotates inside the short tube
53 with openings
54, causes a certain preestablished delay between the breakage and/or lack
of thread
5 and the falling of the arm
55 to interrupt the unwinding
of the threads
3,
4 from their feeding bobbins.
FIG. 4 illustrates the configuration of the twisting station following the falling
of the thread-feeler
50 and arm
55, following breakage or lack of
twisted thread
5, for activating the blockage of the unwinding of the two
feeding bobbins.
The falling of the feeler
50 of the thread
5 takes place in a clockwise
direction at one of its run ends, not shown in the figure for the sake of simplicity.
On its rear part, the feeler
50 is equipped with an interception and interruption
element
59 of the thread
3 unwound from the upper bobbin
1
which prevents it from being pulled back again inside the upper hollow pin
10.
The further unwinding of the feeding thread
3 from the upper bobbin is
blocked by a mechanical intercepting device
59 which enters its unwinding
range, interrupts it and prevents it from continuing to pass into the upper hollow
pin
10.
With a small delay with respect to the feeler (
50), the arm
55
also begins to fall until its weight rests with the transversal element
58
on the top
22 of the upper hollow pin
10. The impact of the arm
55
causes, in turn, the disinsertion of the upper hollow pin
10 from the elements
which are keeping it lifted, for example the magnet
47, and lowers it until
its hooded element
45 reaches the top
23 of the lower hollow pin
11.
The connection elements
48 situated at the end of the hooded element
45
intercept the thread
4 when the hollow pin
10 reaches the top of
the lower hollow pin
11 and prevent it from further unwound from its bobbin
2 and pulled back again inside the upper hollow pin
10.
The unwinding of the feeding thread
4 from the lower bobbin
2 is
thus blocked by the downward activation of a mechanical intercepting device
48
which enters the unwinding field of the thread
4 and prevents it from passing
into the lower hollow pin
11.
In the alternative embodiment of the invention illustrated in FIG. 5, the rising
thread
5, after passing the thread-guide
6, runs past a thread-anomaly
sensor
70, capable of detecting whether the thread is present and running,
and also if it falls within a range of preestablished titer and regularity characteristics.
When the sensor
70 detects the lack of running thread or an anomaly in the
characteristics of the thread, it causes the falling of an arm
71 whose
function is analogous to that of the arm
55 of the embodiment illustrated
in the previous figures. It is hinged with a pin
72 which rotates inside
a cylindrical housing situated in the fixed structure
57 and is capable
of falling between an upper position, shown in FIG. 5, to a lower position, shown
in FIG. 6. The arm
71 is sustained in the upper position by a supporting
element
74 having two alternative controlled positions: a protruding advance
position to support the resting arm
71 and a backward position unhooking
the falling arm
71 until it reaches the upper hollow pin
10. These
two positions are controlled according to the detections of the sensor
70:
anomalies or the absence of thread cause the withdrawal of the element
74
and the falling of the arm
71, whereas the detection of the presence of
thread, running normally, keeps the element
74 in an advanced supporting
position of the arm
71.
For this purpose, a transversal pin
75 is inserted in the body of the
arm
71 as a rest on the top
21 of the upper hollow pin
10,
when it drops for the withdrawal of the element
74. The arm
71 is
also produced with a weight which is sufficient for pressing the upper hollow pin
10, overcoming the elastic and/or magnetic forces, which keep it raised.
The arm
71 is equipped in its end part with a thread interception and interruption
element
77.
FIG. 6 illustrates the configuration of the twisting station illustrated in
FIG. 5 following the detection of an anomaly of the thread on the part of the sensor
70. The falling of the arm
71 following the detection of the sensor
70 of anomalies or lack of twisted thread
5, causes blockage of the
unwinding of the two feeding bobbins.
As it falls, the arm
71 intersects, with the thread cutting element
77,
the pointed surface according to which the balloon rotates during normal twisting
functioning. If the sensor
70 has detected an anomaly of the twisted thread
5, the falling of the arm
71 also causes interruption of the thread.
When the arm
71 arrives at the top
22 of the upper hollow in
10,
the element
77 also intersects the run of the thread
3 unwound from
the upper bobbin
1 and interrupts it, preventing it from being pulled back
into the upper hollow pin
10. The arm
71 contemporaneously rests
its weight with the transversal element
75 on the top
22 of the upper
hollow pin
10, lowers it and also interrupts the feeding from the lower
bobbin, analogously to what is described with reference to FIG. 4.
The thread blocking device according to the present invention allows considerable
advantages with respect to the known art. The fact that the blocking of the unwinding
of the threads
3,
4 from the feeding bobbins
1,
2 takes
place without requiring the braking and stoppage of the spindle, is immediately evident.
It can also be noted that, in the known art, the blocking of the unwinding from
the lower bobbin with the spindle functioning was prevented due to the difficulty
in reaching the space between the two bobbins.
Individual braking automatisms for each twisting spindle are not necessary,
with considerable simplification and economy.
*
