Yarn delivery device and drive wheel suitable for this purpose

A yarn delivery device has a casing, a delivery drum rotatably mounted on the casing, a drive belt, at least one drive wheel propelling the delivery drum, the drive wheel having a peripheral section for application of the drive belt and being provided with at least one cleaning channel extending in a peripheral direction, and at least one scrapper attached to the casing and projecting at a point of a peripheral section remaining free of the drive belt into the cleaning channel.

BACKGROUND OF THE INVENTION 
The invention relates to a yarn delivery device having a casing, a delivery 
drum rotatably mounted thereon, and at least one drive wheel intended to 
propel the delivery drum, said drive wheel having a peripheral section 
intended for application of a drive belt. 
In known yarn delivery devices or feed mechanisms of this type (EP 0 217 
373 A2), which are used in particular in numerous textile machines, the 
yarn delivery drum is usually propelled by means of a drive wheel which is 
designed in the form of a toothed belt disc or of a spur pinion, and is 
looped around on a portion of its circumference by a drive belt in the 
form of a toothed belt, which is driven from a central drive system. The 
toothing serves the purpose of avoiding slippage between the drive belt 
and the drive wheel, and in particular in the case of positive yarn supply 
to the textile machine, to ensure that at every point in time quantities 
of yarn are provided which are in a precisely defined ratio to the 
operating speed of the textile machine, e.g. to the rotary speed of the 
needle cylinder of a circular knitting machine. 
When processing yarns in the form of fibre yarns, large amounts of floating 
fluff particles result in the atmosphere surrounding the textile machine. 
These among other things are caught up by the drive belt and carried 
along. Therefore it is conventional to provide at any point in the drive a 
cleaning device, in order to clean the drive belt and free it from the 
entrained fluff particles. Such cleaning devices for example contain two 
brush wheels rolling along the drive belt. 
Cleaning devices of this sort have proved inadequate. Therefore, despite 
their use, fluff residues adhering to the drive belt are conveyed into the 
tooth gaps of the tooth belt discs, and in particular into the interspaces 
between the tooth points of the toothed belt, and are pressed into the 
base of the teeth of the toothed belt disc. The tooth spaces in this way 
are gradually and progressively filled, until their overfilling leads to a 
situation in which the toothed belt is pushed out of the tooth gaps, and 
proper propulsion is no longer possible, or the compressed fluff particles 
are released in an uncontrolled manner from the belt disc and drop off in 
the form of thick fluff clots. These are in addition frequently mixed with 
abrasions from the drive belt and/or the drive wheel, and mixed with oil, 
thereby becoming contaminated and also in addition extremely discoloured, 
and in particular can adopt a pitch-black colour. 
As the yarn delivery devices in textile machines are frequently disposed 
directly above those working points at which the yarns supplied thereby 
are processed, there is a risk that the fluff clots will be processed 
together with the yarns by the textile machine. In the case of circular 
knitting machines, for example, the fluff clots could in this way pass 
into the area of influence of the knitting needles, and either destroy 
these or be worked into the knitted fabric to be produced by the circular 
knitting machine, which in this way is likewise contaminated and 
discoloured and thus require expensive subsequent treatment. 
Corresponding problems can arise if instead of tooth belts and tooth belt 
discs, other propulsion means, particularly untoothed drive belts and 
drive rollers are used. 
SUMMARY OF THE INVENTION 
It is, therefore, an object of this invention to design the yarn delivery 
device described above in such a way that an accumulation of fluff 
particles on the drive belt and/or on the circumferential section of the 
drive wheel co-operating therewith is to a large extent avoided. 
A further object of this invention is to design a drive wheel for the yarn 
delivery device mentioned above in such a way that an accumulation of 
fluff particles on the drive belt and/or the drive wheel can be avoided in 
a simple manner. 
These and other objects of the present invention are solved in that the 
peripheral section of the drive wheel is provided with at least one 
cleaning channel surrounding in the peripheral direction, and there is 
attached to the casing at least one scraper, which projects at a point of 
the peripheral section remaining free of the drive belt with a free end 
section into the cleaning channel. 
The invention further provides a drive wheel for a yarn delivery drum with 
at least one peripheral section intended for application of a drive belt, 
said drive wheel having a peripheral section which is provided with at 
least one cleaning channel rotating in the peripheral direction.

DESCRIPTION OF PREFERRED EMBODIMENTS 
The yarn delivery device shown in FIG. 1 has a casing 1, which is 
detachably secured on a sub-base 2 of a machine processing or consuming 
yarns, e.g. a circular knitting machine. Disposed on the underside of the 
casing 1 is a conventional storage or delivery drum 3, which is mounted to 
rotate about an axis of rotation 4 and for this purpose is rigidly 
connected to a shaft 5 rotatably mounted in the casing 1. Rotatably 
mounted on a portion of the shaft 5 projecting above the upper side of the 
casing 1 is a drive wheel 6, which is driven by a drive system not shown 
by means of a drive belt 7. 
In order that the delivery drum 3 can be optionally propelled at different 
rotary speeds, frequently at least one further drive wheel 8 is secured 
coaxially on the shaft 5, and which is in an effective connection with a 
second drive belt 9. An e.g. manually switchable clutch disc 10 is 
non-rotarily connected to the shaft 5 between the two drive belts 6 and 8, 
and which can be displaced axially on the shaft 5 and thus can be 
non-rotarily coupled optionally, e.g. by frictional connection, with one 
or the other drive wheel 6 or 8. Thus either the drive wheels 6,8 have 
different diameters, or the drive belts 7,9 are driven at differing 
speeds. 
Secured at the free end of the casing 1 are a yarn brake 11 and a yarn eye 
12 located thereabove. On the underside of the casing 1 there is provided 
a yarn inlet guide member 14, e.g. an eye disposed between the yarn brake 
11 and the delivery drum 3, while on the side of the delivery drum 3 lying 
diametrically opposite the guide member 14 are provided two yarn outlet 
members 15 and 16 secured to the underside of the casing 1, and which, 
like the guide member 14, can consist of open or closed eyes. A yarn 17 is 
passed from a supply spool not shown through the yarn eye 12, the yarn 
brake 11 and the guide member 14 obliquely from above and substantially 
tangentially onto the yarn support surface of the delivery drum 3, is 
wound up thereon in at least one, preferably a plurality of windings and 
finally is fed substantially tangentially through the two guide members 15 
and 16 and a processing point not shown of a knitting machine or the like. 
Sensors 18 and 19, likewise attached to the casing 1, can in a 
conventional way serve to monitor the yarn 17. 
FIGS. 2 and 3 show on an enlarged scale the drive wheel 6 and the drive 
belt 7 of the yarn delivery device according to FIG. 1. The drive wheel 8 
and the drive belt 9 can be substantially identical in design. 
The drive wheel 6 has, for example in the fashion of a conventional drive 
belt, two spaced-apart and coaxially disposed substantially plane parallel 
circular flanged wheels 21 and 22, between which there sits a hollow 
cylindrical member 23 slightly smaller in diameter and secured to the 
shaft 5, and which forms a peripheral section 24 intended for application 
of the drive belt 7. This peripheral section 24 is provided with a 
toothing, which consists of teeth 25 extending parallel to the axis 4 and, 
disposed therebetween, tooth gaps 26, and serves to co-operate with or be 
brought into engagement with a corresponding toothing 27 of the drive belt 
7 designed as a toothed belt, in order to ensure slip-free propulsion of 
the drive roller 6 by the drive belt 7. Thus the peripheral section 24 and 
the drive belt 7 can have a width substantially corresponding to the 
spacing between the flanged wheels 21,22, as shown in FIG. 2 by the 
measurement a. 
Yarn delivery devices, drive wheels and drive belts of the type described 
are generally known to the person skilled in the art (e.g. DE 37 11 558 
C1, EP 0 217 373 A2, EP 0 499 218 A1) and therefore need no further 
explanation. 
According to the invention the drive roller 6 has a cleaning channel 29, 
which is machined in the peripheral section 24, extends over its entire 
circumference and is preferably disposed in the centre between the two 
flanged wheels 21,22. 
According to the invention, there is associated with the cleaning channel 
29 a scraper 30, which is secured by means of a screw 31 or the like (FIG. 
1) to the casing 1, and e.g. consists of a rod-shaped component having a 
circular cross-section, which projects with one free end section 32 into 
the cleaning channel 29, appropriately without touching it, and preferably 
terminating close above its base. Thus it is evident that the drive belt 
7, as FIG. 3 shows, always abuts on a portion of the peripheral section 24 
of the drive wheel 6, and the scraper 30 projects at a point not occupied 
by the drive belt 7, e.g. at a point of the peripheral section 24 lying 
diametrically opposite the drive belt 7, into the cleaning channel 29. 
The cleaning channel 29 is machined for example by a simple milling 
procedure into the peripheral section 24, where the complete drive wheel 6 
is not manufactured as a plastics injection moulded part. The depth of the 
cleaning channel 29, measured in the radial direction of the peripheral 
section 24, starting from the outer surface of the peripheral section 24, 
is preferably slightly deeper than corresponds to the bases of the tooth 
gaps 26 of its toothing, and the scraper 30 preferably projects to such a 
depth into the cleaning channel 29 at the free end section 32 according to 
FIG. 3 likewise terminates beneath the bases of the tooth gaps 26. 
The scraper 30 serves the purpose of removing all fluff particles, yarn 
residues and such contamination pressed into the tooth gaps 26 of the 
peripheral section 24, immediately from the tooth gaps 26 again, before 
they can be compressed into dense, possibly discoloured fluff clots. As 
the fluff and yarn portions are to a large extent disposed in the 
peripheral section 24 so that they are disposed at least partly parallel 
to the axis 4, they are reliably picked up by the scraper 30 and due to 
the movement of the drive wheel 6 taking place during operation of the 
yarn delivery device, and of the entailed air movement, are removed out of 
the area of the peripheral section 24, before any portion of the 
peripheral section 24 momentarily located in the area of the scraper 30 
again passes into the area of influence of the drive belt 7. It is 
naturally also alternatively possible to provide respectively a plurality 
of cleaning channels 29 between the flanged wheels 21,22, and to associate 
with each cleaning channel a corresponding scraper 30, in order also 
reliably to pick up yarn residues or the like not extending over the width 
a. 
The shape of the end section 32 of the scraper 30 is to a large extent 
optional. For example, the end section 32 of the scraper 30, deviating 
from FIG. 3, could also stand obliquely instead of radially and vertically 
to the axis 4 of the drive wheel 6, and could be provided with a 
wedge-shaped bevelled point disposed in the cleaning channel 29. 
The precise position, arrangement and shape of the scraper 30 can be easily 
determined in individual cases by tests. The same applies to the width and 
depth of the cleaning channel 29. For this latter, a width of about 3 mm 
with a measurement a of e.g. about 13 mm and such a depth have proved 
easily useable, that the cleaning channel 29 projects over the bases of 
the tooth gaps 26 radially inwards by for example about 1 mm. 
If according to FIG. 1 a plurality of drive wheels 6,8 are provided per 
delivery drum 3, these appropriately each have a cleaning channel 29,33, 
and with these there can be associated individual further scrapers 
attached to the casing 1. Alternatively it is however also possible, as 
FIG. 1 shows, to provide a component 34 common to all drive wheels 6,8, 
upon which a plurality of scrapers 30,35 with end sections 32,36 are 
integrally attached, each of which projects into an associated cleaning 
channel 29 or 33. 
The scrapers 30,35 can be made from various materials, particularly metals 
(e.g. spring wire) or plastic, and can be designed extensively rigidly, 
but also flexibly, in dependence on the requirements of the individual 
case. In both cases the scraper 30,35 can consist of a tube, and can be 
designed at its free end as a blower nozzle, in order to connect it to a 
compressed air source or the like and thus to increase the cleaning 
action. 
The invention is not restricted to the embodiment described, which can be 
varied in many ways. For example it is possible to attach the scraper 30 
or the component 34, instead of to the casing 1, to another portion of the 
yarn delivery device or textile machine which is stationary with respect 
to the drive wheel 6,8. The term "casing" is therefore intended to 
comprise all these types of attachment. Furthermore, the drive belt 7,9 
can be designed differently from the way shown and described, and in 
particular can have no peripheral toothing. In this case, the peripheral 
section 24 of the drive wheel 6,8 can also be smooth and without toothing, 
while the cleaning channels 29,33 project to a pre-selected depth into the 
peripheral section 24. Moreover, drive belts can be provided which are 
additionally or exclusively provided with toothings in at least one of 
their lateral edges, these toothings being in engagement with 
corresponding lateral toothings in the drive wheel (e.g. EP 0 185 131 B1). 
In these cases also the formation of fluff clots in the peripheral section 
24 is reliably avoided. It would furthermore be possible to allow the free 
end sections 32,36 or other sections of the scrapers 30,35 to slide on the 
base of the cleaning channels 29,33, in order in this way also reliably to 
eliminate the formation of contamination in the cleaning channel 29,33, 
particularly when the scrapers 30,35 are made of a sufficiently flexible 
material. With respect to the indicated measurements for the width and 
depth of the cleaning channel 29, other values held to be appropriate can 
be used. It can be quite generally ascertained that the width of the 
cleaning channel 23 should for example be between one quarter and two 
thirds the value a and its depth should be at least about 0.5 to 1 mm 
deeper than the tooth base. Thus the scraper 30,35 can for example extend 
at least about 0.5 mm into the cleaning groove 29, and e.g. have a 
cross-sectional dimension which is about 1 mm smaller than the width of 
the cleaning channel, should it not be intended to touch the channel 
walls. Further, the invention is not restricted to drive wheels 6,8 which 
sit directly on the shaft 5 of the delivery drum 3. Alternatively, there 
could be drive wheels 6 or 8 physically separated from the delivery drum 
3, which are coupled via further drive means in a drive relationship with 
the delivery drum 3. Finally it is evident that the features according to 
the invention can also be used in combinations different from those 
illustrated and described. 
It will be understood that each of the elements described above, or two or 
more together, may also find a useful application in other types of 
constructions differing from the types described above. 
While the invention has been illustrated and described as embodied in a 
yarn delivery device and a drive wheel therefor, it is not intended to be 
limited to the details shown, since various modifications and structural 
changes may be made without departing in any way from the spirit of the 
present invention. 
Without further analyses, the foregoing will so fully reveal the gist of 
the present invention that others can, by applying current knowledge, 
readily adapt it for various applications without omitting features that, 
from the standpoint of prior art, fairly constitute essential 
characteristics of the generic or specific aspects of this invention.