[0001] The present invention relates to a drawing frame for webs of textile fibres provided
with a rotary comb head, including a base and a pair of counter-rotating shafts with
horizontal axes supported by the base in a superimposed arrangement, each of the said
two shafts rotatably driving a pair of axially-spaced comb-carrier discs provided
with substantially radial slots in which are slidably engaged a circumferential series
of needle-carrier bars or axial combs the ends of which engage in corresponding shaped
guide tracks rigidly connected to the base, the combs associated with the two shafts
defining two sets of needles intersecting in the treatment region for the web of textile
fibres, the head further being provided with a cleaner device for cleaning the combs
of the two sets of needles.
[0002] Drawing frames of the type indicated above have recently come into widespread use
due to the fact that, compared with conventional machines provided with comb heads
with intersecting needles controlled by worm screws or "augers" they have the advantage
of a greater working speed, of reduced mechanical wear and of facilitating and limiting
maintenance, while achieving the same quality of work typical of the conventional
machines. In order to obtain these results it is absolutely necessary to ensure that
the zone of operation of the rotary head of the machine and the mechanical members
of the head itself, particularly the combs, are completely clean. Indeed, while in
conventional machines with auger heads, cleaning of the combs is achieved directly
due to the movement of the combs themselves, in machines with rotary comb heads, it
is necessary to provide a cleaning device which is able to remove waste material which
is deposited between - the needles of the combs during working.
[0003] In machines having rotary comb heads at present in use, mechanical cleaning devices
have been provided which consist, for example, of 'rotary brushes entrained with the
combs, of rotary brushes controlled mechanically, or of rotary brushes controlled
mechanically and cleaned by mechanical cleaners and suction nozzles. These devices
have a series of disadvantages among which may be cited:
- difficulty of adjustment and of maintaining the adjustment over a period of time,
- wear and tear on the brushes and their respective control members,
- difficulty of access to the working zone of the rotary comb head to allow normal
intervention by the operator during working,
- geometric impossibility of cleaning the combs completely due to the prevalence of
a tangential effect in the relative movement between the cleaning brushes and the
needles of the combs, which results in the impossibility of achieving complete removal
of the waste material from the combs and compaction of material at the roots attaching
the needles to the combs,
- constant removal, during working, of textile fibres which are held by the combs
in the return phase and which should, instead, be returned to the web or mat of material
during the working phase of the combs.
[0004] The object of the present invention is to obviate these disadvantages.
[0005] In order to achieve this object, the present invention provides a drawing frame for
webs of textile fibres, characterised in that the cleaner device for the rotary comb
head comprises a source of compressed air, means for supplying the compressed air
to the interior of each set of needles, and means for directing the compressed air
between the combs of each set of needles in the form of an elongate jet directed outwardly
in a substantially radial, predetermined direction so that, during the rotation of
the shaft, the said jet of compressed air flows tangentially and successively over
the surfaces of the combs of the set of needles.
[0006] Thanks to the characteristic the following important advantages are obtained:
- greater simplicity of manufacture, assembly and maintenance of the machine,
- long working life of the cleaning device due to the absence of moving mechanical
parts,
- smaller bulk of the machine head and easier access to the working zone due to the
fact that the active part of the cleaning device is disposed within the set of needles,
- greater functional efficiency due to the fact that the comb-cleaning phase is carried
out in short time intervals, thus avoiding the removal of textile fibres taken up by the combs themselves during the working phase.
[0007] According to the invention each jet of compressed air is directed substantially parallel
to the direction of displacement of the web of textile fibres to be treated and faces
towards the output zone of the web. As a result of this characteristic, the web of
textile fibres at the inlet to the rotary comb head is not disturbed by the jet of
compressed air of the cleaning device.
[0008] Preferably the jets of compressed air extend parallel to the axes of the respective
shafts of the head over a length substantially equal to the length of the parts of
combs lying between the said comb-carrier discs. Thus the jets of compressed air act
uniformly along the entire active part of each comb.
[0009] According to a further characteristic of the invention, the means for supplying compressed
air to the interior of each set of needles include valve means and programmable timer
means for controlling the said valve means.
[0010] This characteristic makes it possible to regulate the operation of the cleaning device
in dependence on the type of material treated by the machine.
[0011] According to a preferred embodiment of the invention, each of the rotary shafts of
the head is hollow and has an axial passage at one end adapted to put its hollow interior
into communication with the said means for supplying compressed air; the portion of
each shaft between the respective comb-carrier discs supports a freely-rotatable,
cylindrical, tubular casing interposed between the shaft and the combs and provided
with a pair of annular, end heads provided with plain bearings in hermetically-sealed
contact with the surface of the shaft; the said casing has an axial slit formed along
its lateral wall and communicating with the hollow interior of the shaft through apertures
formed in the wall of the said shaft; positioning means are provided for maintaining
the said tubular casing, during the rotation of the shaft,ina fixed angular position
in which the said axial slit is disposed in a substantially horizontal plane passing
through the axis of the shaft. The said positioning means are, to advantage, constituted
by a ballast weight carried by the tubular casing.
[0012] Further advantages and characteristics of the invention will become clear during
the course of the detailed description which follows, with reference to the appended
drawings, provided purely by way of non-limiting example, in which:
Figure 1 is a partially-sectioned, front elevational view of one part of the drawing
frame according to the invention, in which the pneumatic circuit for feeding the cleaning
device is also illustrated schematically,
Figure 2 is a cross-sectional view, on an enlarged scale, taken on line II-II of Figure
1, and
Figure 3 illustrates a detail of Figure 1 on an enlarged scale.
[0013] With reference to the drawings, by 10 is indicated in its entirety a rotary comb
head of a drawing frame for the treatment of webs of textile fibres. The head 10 comprises
essentially a pair of vertical support pillars 12 which serve to support a pair of
superimposed shafts 14 for rotation about horizontal axes. The shafts 14 are rotated
in opposite senses by means of a motor and a conventional transmission not shown in
the drawings.
[0014] Each of the shafts 14 supports, adjacent the pillars 12, a pair of comb-carrier discs
16 provided with corresponding, circumferential sets of substantially radial slots
18. In the slots 18 of the discs 16 associated with each shaft 14 are slidably engaged
a plurality of needle-carrier bars, or combs, 20 disposed parallel to the axis of
the shaft 14. As shown in detail in Figure 2, each comb 20 is constituted by a support
bar 22 carrying, at is outer edge, a plurality of needles 24 which are slightly inclined
to the plane of the bar 22. The ends of the bar 22 of each comb 20 project outwardly
of the comb-carrier discs 16 and engage slidably in corresponding shaped guide tracks
26 formed in the support pillars 12. In this manner, during rotation of the shafts
14, the combs 20 are entrained for rotation with the discs 16 and, as a result of
the shaped tracks 26, are guided along partially eccentric paths with respect to the
axes of the respective shafts 14. These paths, which are clearly visible in Figure
2, effect mutual approaching of the combs 20 entrained by the two shafts 14 in the
zone of treatment of the web, indicated by F, and a sharp displacement of these combs
away from each other on leaving the treatment zone of the web. The combs 20 carried
by the two shafts 14 thus define two sets of needles which intersect in the zone of
working of the head 10.
[0015] Each shaft is hollow and has an axial passage 28 at one end, shaded as a convergent-divergent
venturi opening externally of the head 10. On that portion of each shaft 14 lying
between the respective comb-carrier discs 16 is mounted, for free rotation, a tubular,
cylindrical casing 30 interposed between the shaft 14 and the support bar 22 of the
combs 20. Each casing 30 has a pair of annular heads 32 at its ends, each head bearing
an annulus of thermoplastics material 34 in contact with the surface of the shaft
14. The annuli 34 constitute plain bearings for supporting the casing 30 and are,
moreover,
' adapted to achieve hermetic sealing of the hollow interior of the casing 30 with
respect to the surface of the shaft 14.
[0016] As is clearly seen in Figure 2, each casing 30 has a semi-cylindrical upper portion
36 provided alongĀ· its axial edges with edge flanges 38,39 bent outwardly and substantially
aligned in a horizontal plane. The flange 38 which faces inwardly of the machine is
coupled to one of the axial edges of a semi-cylindrical, lower portion.40 which completes
the tubular casing 30. The lower portion 40 is considerably thicker and, hence, considerably
heavier than the upper portion 36. The other axial edge of the lower portion 40 ends
a short distance from the flange 39 of the upper portion 36 so as to define an axial
slit 42 which extends for the entire length of the casing 30. As a result of the conformation
of the casing 30 described above, the axial slit 42 is maintained constantly in a
fixed angular position, in which it is disposed in a substantially horizontal plane
passing through the axis of the shaft 14, by gravity, even during rotation of the
shaft 14. The axial slit 42, on the basis of what has been said above, faces outwardly
of the textile machine.
[0017] The hollow interior of each casing 30 communicates with the interior of the respective
shaft 14 through a series of holes 44 formed in the lateral wall of the shaft 14.
[0018] As illustrated in figure 1, the venturi-shaped outer portion 28 of the axial passage
of each shaft 14 is associated with a nozzle 46 disposed so as to form an injector
48 with the passage 28. The nozzles 46 are connected to a compressed-air supply circuit
indicated in its entirety by 50. The circuit 50 includes a source 52 of compressed
air connected, through a monitoring valve 53, to a filter and regulator device 54
associated with a manometer 56. The filter- regulator device 54 is connected, through
a non- return valve 58, to an air accumulator 60. The accumulator 60 is connected
to the two nozzles 46 with the interposition of a solenoid valve 62 controllable by
means of a programmable timer 64.
[0019] Adjacent the working zone of the head 10, on the input side for the textile fibre
web F, is an entrainment assembly 68. The entrainment assembly 68 includes a pair
of rotary cylinders 70 associated with a pressure roller 72, and has the function
of improving the control of the web of fibres F in the feed.
[0020] During operation of the head 10, the web of fibres F is fed in a substantially horizontal
direction in the direction of arrow A, through the zone between the shafts 14 and
the respective combs 20. The shafts 14 are rotated in the senses indicated by the
arrows B and drive the combs 20 which thus move along the paths defined by the shapes
of the guide tracks 26. The rotary combs 20 thus define two sets of needles which
intersect in the zone of passage of the web of textile fibres F and penetrate the
web F successively, effecting, in combination with a drawing assembly 100 at the outlet,
a drawing action.
[0021] Simultaneously, the pneumatic circuit 50 supplies compressed air to the two nozzles
46 through the solenoid valve 62.. According to the type of material to be treated,
the solenoid valve 62 may be maintained constantly in an open position or may be controlled
to open and close. in a predetermined cycle by means of the programmable timer 64.
The compressed air leaving each nozzle 46 passes through the axial passage 28 into
the hollow interior of the respective shaft 14. Thanks to the conformation of the
axial passages 28 and the disposition of the nozzles 46, the compressed air leaving
each nozzle draws a current of air from the external environment into the interior
of the respective shaft 14. The air then passes through the holes 44 in the wall of
the shaft 14 and into the tubular casing 30. The air then leaves the casing 30 through
the axial slit 42, thus creating an elongate, laminar jet directed radially outwardly.
During the rotation of the shaft 14, the casing 30, and hence the axial slit 42, are
maintained in a fixed angular position due to the presence of the ballast constituted
by the lower cylindrical portion 40 of the casing. Thus the jet of air flows tangentially
over the combs 20 which are located successively in correspondence with the slit 42
and detaches and separates waste material which accumulates at the base of the needles
24. An integral suction system, known per se and not illustrated in the drawings,
collects this material and discharges it outside the machine.
[0022] The conformation of the axial slits 42 and their positioning with respect to the
rotary
'combs 20 allows an efficient cleaning action to be achieved with the minimum consumption
of compressed air. The consumption of air is further reduced by the presence of the
injectors 48 constituted by the axial passages 28 and the respective nozzles 46. Moreover,
the jets of air which, as indicated previously,-- are directed parallel to the direction
of displacement A of the web of textile fibres F and face towards the output zone
of the web, do not disturb the web of fibres F at the inlet to and at the exit from
the head 10 to any extent.
[0023] Naturally, the principle of the invention remaining the same, the details of construction
and the embodiments may be varied widely with respect to what has been described and
illustrated, without thereby departing from the scope of the present invention.
1. A drawing frame for webs of textile fibres provided with a rotary comb head (10)
including a base (12) and a pair of counter-rotating shafts (14) with horizontal axes
supported by the base in a superimposed arrangement, each of the said two shafts rotatably
driving a pair of axially spaced comb carrier discs.(16) provided with substantially
radial slots (18) into which are engaged, in a slidable manner, a circumferential
series of needle carrier bars or axial combs (20) the ends of which engage in corresponding
shaped guide tracks (26) rigidly connected to the base, the combs associated with
the two shafts defining two sets of needles intersecting in the treatment region for
the web of textile fibres; the head (10) being moreover provided with a cleaner device
for cleaning the combs =(20) of the two sets of needles, characterised by the fact
that the cleaner device comprises a source of compressed air (52), means (46, 50)
supplying the compressed air to the interior of each set of needles (24), and means
(14, 30.) for directing between the combs (20) or each set of needles (24) the compressed
air in the form of an elongate jet directed outwardly in a substantially radial predetermined
direction (A) so that during the rotation of the shaft (14) the said jet of compressed
air brushes tangentially and successively the surfaces of the combs (20) of the set
of needles (24).
2. A drawing frame according to Claim 1, characterised by the fact that the jets of
compressed air are directed substantially parallel to the direction of displacement
(A) of the web (F) of textile fibres to be treated, and faces towards the output zone
of the web (F).
3. A drawing frame according to Claim 1, characterised by the fact that the jets of
compressed air extend parallel to the axes of the shafts (14) of the head (10) for
a length substantially equal to the length of the parts of the combs (20) lying between
the said comb-carrier discs (16).
4. A drawing frame according to Claim 1, characterised by the fact that the means
(46, 50) for supplying compressed air to the interior of each set of needles (24)
comprises valve means (62) and programmable timer means (64) for the control of the
said valve means (62).
5. A drawing frame according to Claims 1 to 3, characterised by the fact that each
of the rotating shafts (14) of the head (10) is hollow and has at one end an axial
passage (28) able to put into communication the hollow interior of the shaft with
the said means (46, 50) for supplying compressed air; a portion of each shaft (14)
lying between the respective comb-carrier discs (16) supporting a freely rotatable
cylindrical tubular casing (30) interposed between the shaft (14) and the combs (20)
and provided with a pair of annular end heads (32) provided with plain bearings (34)
hermetically sealed in contact with the surface of the shaft (14); the said casing
(30) having an axial slit (42) formed along its lateral wall and communicating with
the hollow interior of the shaft (14) through aperture (44) formed in the wall of
the said shaft (14); positioning means (40) being provided for maintaining, during
the rotation of the shaft (14), the said tubular casing (30) in a fixed angular position
in which the said axial slit (42) is disposed in a substantially horizontal plane
passing through the axis of the shaft (14).
6. A draw frame according to Claim 5, characterised by the fact that the said positioning
means are constituted by a ballast weight (40) carried by the tubular casing (30).
7. A drawing frame according to Claim 6, characterised by the fact that the lateral
wall of the tubular casing (30) has a substantially semi-cylindrical lower portion
(40) which extends'substantially from the said axial slit (42) up to a position in
correspondence with the region of the casing (30) diametrically opposite the slit
(42), and has a weight significantly greater than that of the remaining portion (36)
of the casing (30).
8. A drawing frame according to Claim 4, characterised by the fact that the said axial
end passage (28) of each shaft (14) is shaped in the form of a convergent-divergent
venturi, and by the fact that the said means (46, 50) for supplying compressed air
includes a pair of nozzles (46) connected to the said source of supply (52) with the
interposition of a solenoid valve (62) controllable by means of a programmable timer
(64) and each associated with the axial end passage (28) of one of the shafts (14)
in such a way as to form an air injector (48).
9. A drawing frame. according to Claim 4, characterised by the fact that the hermetically
sealed plain bearings (34) carried by the end heads (32) of the tubular casing (30)
are constituted by rings of thermoplastics material.
10. A drawing frame substantially as described with reference to the attached drawings.