[0001] This invention relates to false twist apparatus, and in particular to apparatus for
use in determining the point, in the path of a textile yarn through a false-twist
crimping machine, at which the twisting of the yarn commences. Such a device is known
as a twist-stop, and has the effect of preventing the passage of twist, generated
in the yarn by a false-twist device, from travelling upstream of the twist-stop.
[0002] Many differing types of twist-stop device are known, and many other devices which
have another primary function, for example feed rollers, may also serve very satisfactorily
as twist-stop devices. However the latter generally do not give the precise control
of the yarn which is required in this sensitive area, and it may not be practicable
to position them for good twist-stop functioning. Therefore it is customary for false-twist
crimping machines to be fitted with devices which have the sole function of twist-stopping.
A large proportion of such twist-stopping devices are in the form of a rotatable member
around the periphery of which the yarn is caused to pass, such periphery providing
a tortuous or zig-zag yarn path. Such twist-stop devices are also of many differing
forms. For example, in GB Patent No 908112, there is described a rotatable disc having
at its periphery a series of radial slits whereby oppositely bent blades form a zig-zag
V-shaped groove in which the yarn runs. A similar device is shown in GB Registered
Design No 895467, comprising a pair of coaxially secured discs with pressed-out ribs
between cut-outs on each disc, the ribs on one disc interdigitating with those on
the other disc. However twist-stops of such a construction tend to abrade the yarn
and can cause filament breakages in multi-filament yarns, or even yarn breaks. Alternatively
they may become distorted and cease to be effective as a twist stop. To reduce these
problems the ribs may be stamped out of the discs without slits or cut-outs, as described
in GB Patent No 1297097. Such ribs, or lugs, may have a rounded cross-section so as
to provide for more gentle control of the yarn than was the case with the previously
described type of twist-stop device. However due to difficulties in producing identical
ribs as regards dimensions and surface finish, not only from one twist-stop to another,
but also around the periphery of a single twist stop, the control of the yarn in this
sensitive area is not as satisfactory as is desired. Furthermore the sheet metal from
which the above described twist stop devices are made tends to wear rapidly under
the abrading action of the yarn.
[0003] To improve upon the latter device there has been produced a twist stop in which the
aforementioned ribs on each of the two coaxially secured discs are formed of a ceramic
material, the discs being of a plastics material. The discs of this device are moulded
with the ceramic discs in situ, and this entails a difficult and costly manufacturing
process. Also the surface finishing of the ceramic ribs prior to assembly of the twist-stop
is difficult and costly.
[0004] As an alternative to the above described twist stop devices there is also known a
twist stop comprising a plurality of cylindrical pins secured around the periphery
of a roller, which pins are alternately oppositely inclined out of the central plane
of the roller to form a V-shaped, zig-zag yarn path around the periphery of the twist
stop. The pins are of a ceramic material and of circular cross-section, so that substantially
identical size and surface finish can readily be produced on all pins. Such a twist-stop
has been used extensively and successfully for more than 17 years. It is easier and
less costly to produce than the ceramic-ribbed twist-stop described above, and this
is an important factor in yarn texturing since damaged twist-stops, which affect the
quality of the textured yarn, are often tolerated due to the high cost of repeated
replacement.
[0005] Despite the commercial success of the latter twist-stop, the pins are prone to damage,
and it can be difficult to thread-up for a machine operator who is not highly experienced.
To overcome this problem, shrouds have been fixed to texturing machines to assist
in guiding the yarn and protecting the pins. However such shrouds make it more difficult
to remove yarn wraps from the twist stop and yarn or debris can get between the twist-stop
and the shroud.
[0006] It is an object of the present invention to provide a twist stop which overcomes,
at least to a significant extent, all of the abovementioned disadvantages of the prior
known twist stop devices.
[0007] The invention provides a twist stop device comprising a roller having an array of
cylindrical pins of a wear resistant material extending outwardly thereof, with alternate
pins being relatively disposed and oppositely inclined relative to a median plane
of the roller whereby the array defines a V-shaped, zig-zag yarn path for a yarn running
around said device, and the roller comprising a pair of walls disposed adjacent the
array of pins on opposed sides thereof and extending radially outwardly of the roller
at least to the outer ends of the pins.
[0008] The pins may be of a ceramic, sapphire, hardened steel or tungsten carbide material,
and may be retained in receiving formations provided in the roller. The pins may be
clipped or adhesively bonded in the receiving formations, which may be bores or recesses.
[0009] The walls may be of a plastics material, and may be integral with a hub part of the
roller. The roller may be formed in two parts, each comprising a wall and a hub portion.
The parts of the roller may be substantially identical, each hub portion comprising
half of the hub part. Each hub portion may have a plurality of pin receiving recesses
therein, equi-spaced therearound, and interdigitating formations may be provided on
said two hub portions. A plurality of interdigitating formations may each be provided
with one pin receiving recess therein. Each wall may comprise a peripheral lip which
extends over at least part of the outer ends of those pins inclined towards that wall.
Each wall may also comprise an inwardly directed surface which is inclined relative
to the median plane of the device and contacts those pins inclined towards that wall
over the length of those pins.
[0010] The pins may be inclined at an angle of between 15
o and 30
o, for example 20
o, relative to the median plane, and each pin may have a diameter of substantially
1mm. The pins may be disposed at equi-angularly arranged locations, and there may
be at least one more location than pins in the device. There may be two diametrically
opposed locations at which no pin is provided, for example 40 pins may be provided
at 42 equi-angularly arranged locations. At the or each location having no pin disposed
thereat, a slot may be provided in the walls, which slot may extend radially inwardly
substantially to the hub part.
The device may be of comparatively small overall diameter, for example up to 50mm,
and may be substantially 36 mm in diameter. The device may comprise a bearing axially
located in the hub part. The interdigitating formations may be formed so as to resist
separation of the two parts, or the two parts may be secured to each other as by an
adhesive, welding or by screws or rivets.
[0011] Alternatively at least one spigot may be formed on one of the hub portions, and for
the or each spigot a bore be provided in the other of the hub portions, the or each
bore being adapted to receive a spigot therein. The or each bore may have a counterbore
part into which an enlarged head of a spigot, formed after assembly of the roller,
is received. The invention will now be further described with reference to the accompanying
drawings in which :-
Fig 1 is a front elevation of one half of one embodiment
Fig 2 is a sectional view on line 2-2 of the embodiment of Fig 1, with the bearing
removed for clarity,
Fig 3 is a side view of an assembly of two halves corresponding with that shown in
Figs 1 and 2.
Figs 4 to 7 are front elevations and sectional views onlines 5-5 and 7-7 respectively
of the two roller parts of a second embodiment prior to assembly, and
Fig 8 is a sectional view of the assembled second embodiment of roller.
[0012] Referring now to Figs 1 and 2, there is shown one half 11 of one embodiment of twist
stop device 10 in accordance with the present invention. The half device 11, which
may be moulded of a plastics material, comprises a wall 12 and a half hub part 13,
the latter having a through bore 14 and a counterbore 15 into which a ball bearing
16 (not shown in Fig 2) is fitted. The half hub part 13 is formed to have a plurality
of alternating , radially extending ribs and recesses, 17 and 18 respectively which
can interdigitate with corresponding formations on another half 19 (Fig 3) of the
twist stop device 10. In this case, 21 ribs 17 and 21 recesses 18, all of equi-angular
extent, are formed around the half hub part 13, although other numbers of ribs and
recesses may be provided if desired. The ribs 17 and recesses 18 of the two twist-stop
halves 11, 19 may be formed so as to resist separation of the two halves 11, 19 when
assembled as shown in Fig 3. However welding, eg ultrasonic welding, or adhesive bonding
of the two halves 11, 19 is preferred. Alternatively the two halves 11, 19 may be
secured to each other by screws or rivets.
[0013] In twenty of the ribs 17 and twenty of the recess 18 are formed semi-circular grooves
20, 21 respectively, the remaining rib 17¹ and recess 18¹ which are not provided with
grooves being diametrically opposed. Into each of the grooves 20 is fitted a pin 22
of circular cross-section. The grooves 20 and the inwardly directed surface 23 are
inclined relative to the median plane 24 of the assembled twist stop 10 (Fig 3) at
an angle of substantially 20
o, the surface 23 being aligned with the bottom of the recesses 18 so as to support
the pins 22 over their entire length. A peripheral rib 25 extends over approximately
half of the outer ends of the pins 22 so as to prevent the pins 22 from flying out
of the twist stop 10 as it rotates. The pins 22 are of a hard wearing material such
as ceramic, sapphire, hardened steel or tungsten carbide, and because of their simple
shape, can readily be manufactured, ground and polished to the required dimensions
and surface finish. The pins 22 may be clipped or adhesively bonded into the grooves
20.
[0014] Two twist stop halves 11, 19 as described above are assembled together as shown in
Fig 3 to form the complete twist stop 10. The ball bearing 16 is housed in the two
counterbores 15,and the ribs 17 of twist stop half 11 enter the recesses 18 of the
twist stop half 19. At the same time, the semi-circular portion of the pin 22 protruding
from the grooves 20 in the ribs 17 of each twist stop half 11, 19 enter the grooves
21 in the recesses 18 of the other twist stop half 19, 11 respectively. It is ensured
on assembly that the non-grooved rib 17¹ of each twist stop half 11, 19 enters the
non-grooved recess 18¹ of the other twist stop half 19, 11. Radially outwardly of
the ribs 17¹ and recesses 18¹ are slots 26 which extend radially in the walls 12 substantially
to the hub part 13 to facilitate the cutting and removal of yarn wraps from around
the twist stop 10, without damaging any of the pins 22.
[0015] Referring now to Figs 4 to 8, there is shown the two parts of a second embodiment
of twist stop device 28 in accordance with the invention. The device 28 comprises
a male part 29 (Figs 4 and 5) and a female part 30 (Figs 6 and 7), which have many
features corresponding with features of device 10 previously described. Such corresponding
features are referenced with corresponding reference numerals. However in their embodiment,
three spigots 31 are provided on the male part 29, to be received in three correspondingly
positioned bores 32 in the female part 30, instead of the previously described interdigitating
formations. The bores 32 each have a counterbore 33 to accommodate an enlarged head
34, of a spigot 31, formed after assembly of the two parts 29, 30. The bearing 16
is fitted to the counterbores 15 during such assembly. Instead of the semi-circular
grooves 20, 21 of the previous embodiment 10, blind bores 35 in the hub part 13 of
the male part 29 receive the inner ends of alternate pins 22, whilst the remainder
of the pins 22 have their inner ends received in a part circular groove formed between
two ribs 36 also provided on the hub part 13 of the male part 29. Corresponding pairs
of ribs 36 are also provided on the hub part 13 of the female part 30. The outer ends
of the pins 22 are received in similar groove/two rib formations 37 provided at alternate
pin locations on the male and female parts 29, 30 respectively adjacent the peripheral
rib 25.
[0016] As can be seen from Figs 3 and 8, the two twist stop halves 11, 19 or parts 29, 30,
when assembled, ensure that the array of pins 22 provide a V-shaped, zig-zag path
for a yarn 27 passing around the twist stop 10 or 28. The accurately produced pins
22 minimise damage to the yarn 27. Since the pins 22 are retained and protected by
the peripheral ribs 25, there is less likelyhood of the twist stop being damaged,
and hence replacement is less frequent than was the case with known pinned twist stops.
Furthermore, since threading is easier and yarn displacement is less likely due to
the presence of the walls 12, the pins 22 may be shorter than was the case heretofore,
thereby making the present twist-stop less costly to manufacture than the known twist
stops. Cheaper twist stops are more likely to be replaced when damaged, and therefore
less poor quality yarn is likely to be produced.
[0017] Also the smaller pins provide that the present twist stop is lighter than known twist-stops,
thereby ensuring longer bearing life and hence less frequent twist stop replacement.
Furthermore a lighter twist stop is able to be accelerated to its operating speed
by finer yarns without yarn breakage, than is the case with known heavier twist stops.
[0018] Other embodiments of twist stop in accordance with the invention will be readily
apparent to persons skilled in the art. For example the pins may be inserted in holes
in the periphery of a single hub part, and the two wall parts then secured to the
hub part by an adhesive, by welding or by screws.
1. A twist stop device comprising a roller having an array of cylindrical pins of a wear
resistant material extending outwardly thereof, with alternate pins being relatively
disposed and oppositely inclined relative to a median plane of the roller whereby
the array defines a V-shaped, zig-zag yarn path for a yarn running around the device,
characterised in that the roller (10;28) comprises a pair of walls (12) disposed adjacent
the array of pins (22) on opposed sides thereof and extending radially outwardly of
the roller (10;28) at least to the outer ends of the pins (22).
2. A device according to claim 1 characterised in that the pins (22) are retained in
receiving formations (20,21;35,36,37) provided in the roller (10;28).
3. A device according to claim 1 or claim 2 characterised in that the walls (12) are
formed integrally with a hub part (13) of the roller (10;28) and a bearing (16) is
axially located in the hub part (13).
4. A device according to any one of claims 1 to 3 characterised in that the roller (10;28)
is formed in two parts (11,19;29,30) each comprising a wall (12) and a hub portion
(13).
5. A device according to claim 4 characterised in that interdigitating formations(17,18)
are provided on the two hub portions (13).
6. A device according to any one of claims 1 to 5 characterised in that each wall (12)
comprises a peripheral lip (25) which extends over at least part of the outer ends
of those pins (22) inclined towards that wall (12) and in that each wall (12) has
an inwardly directed surface (23) which is inclined relative to the median plane (24)
of the device (10;28) and contacts those pins (22) inclined towards that wall (12)
over the length of those pins (22).
7. A device according to any one of claims 1 to 6 characterised in that the pins (22)
are inclined at an angle of between 15o and 30o relative to the median plane (24) and are disposed at equi-angularly arranged locations.
8. A device according to claim 7 characterised in that there are two diametrically opposed
locations at which no pin (22) is provided, and in that a slot (26) is provided in
the walls (12) each location having no pin (22) disposed thereat.
9. A device according to claim 4 characterised in that at least one spigot (31) is formed
on one of the hub portions (13) and for the or each spigot (31) a bore (32) is provided
in the other of the hub portions (13) adapted to receive a spigot (31) therein.
10. A device according to claim 4 characterised in that the two roller parts (11,19;29,30)
are secured to each other by an adhesive.