This invention relates to methods and apparatus for the production
of colored knitted nets. More particularly, the invention relates to apparatus
and methods for coloring individual ribbons of knitted nets.
Knitted nets are currently used for products including sacks for
agricultural produce, bird protection nets, shading nets, insect protection nets
and nets for wrapping round bales of hay. Such knitted nets are generally produced
in a process which includes production of a primary film, slitting of the film
into individual ribbons, orientating the ribbons, knitting the individual ribbons
into a knitted net, and winding the knitted net onto a spool. The primary film
may be produced in various colors according to the intended application of the
Frequently, there is a desire for knitted net which includes a strip
of a particular color that differs from the overall color of the net. This may
be for providing a strip of a particular shade at the end or middle of the net
to indicate the netting product as originating from a specific supplier. Different
color markings for similar products may also be used either for marking the end
of a roll or in conjunction with a photoelectric cell to count the number of cuts.
A common method of coloring knitted netting is to use bobbins of
different colored ribbons. These bobbins of colored ribbons are conveniently placed
at the knitting machine and the colored ribbons are threaded into the machine
as replacements for the original ribbons. Usually these colored ribbons have some
amount of orientation and the bobbins are, therefore, located after the orientation
stage in the net production process. The original ribbons of the overall color
which have been replaced are automatically wound onto rolls and then recycled.
In the Raschel method of knitting, two types of ribbons are employed;
transverse ribbons and longitudinal ribbons. When there is a desire to change color
in the netting in the longitudinal direction, ribbons may be replaced as described
above. When there is a desire to change color in the transverse direction, however,
the above described method may not be used as the knitting of the longitudinal
ribbons takes less than a second. Shutting down the knitting machine, changing
the ribbons, and restarting the machine to run for such a short period of time
is extremely inefficient.
Accordingly, the existing coloring method is only useful when there
is a need to color longitudinal ribbons. Additionally, multiple colored ribbons
must be stocked, each having characteristics compatible with the final product.
The existing coloring method also introduces technical complications in the net
knitting procedure causing wastage of raw materials and increase in the cost of
the final product.
Accordingly, there is a need in the art to provide an efficient method
and apparatus for coloring knitted nets during production of the netting.
In view of the foregoing it is an object of the invention to provide
an apparatus and method for producing colored knitted net which colors the individual
ribbons of the knitted net.
It is a further object of the invention to provide an apparatus and
method for producing colored knitted net which may be incorporated into the on-line
production of the knitted net.
It is a further object of the invention to provide an apparatus and
method for producing colored knitted net which is independent of the characteristics
of the individual ribbons of the knitted net.
It is known from US-A-4060999 to provide an apparatus for producing
knitted net from thermoplastic material comprising a source for supplying a plurality
of individual oriented thermoplastic ribbons at a constant speed and a knitting
apparatus for knitting said plurality of individual oriented thermoplastic ribbons
into a net.
An apparatus for producing knitted net according to the present invention
is characterised by a coloring apparatus disposed between the source and the knitting
apparatus including means for coloring selected oriented thermoplastic ribbons
of the plurality of individual oriented thermoplastic ribbons supplied from the
It is also known to provide a method of producing knitted net from
thermoplastic material comprising the steps of supplying a plurality of individual
oriented thermoplastic ribbons at constant speed and knitting them into a net.
A method of producing knitted net according to the present invention
is characterised by the step of colouring selected oriented thermoplastic ribbons
of the plurality of individual oriented thermoplastic ribbons supplied from the
source before knitting them into the net.
In a preferred apparatus of the invention, the individual ribbon
coloring apparatus is provided in the net production process after the orientation
stage and prior to the knitting stage. All or some of the individual ribbons may
pass through the coloring apparatus. Each ribbon passing through the coloring apparatus
may be either included in or excluded from the coloring process in accordance
with a control system which operates consistently with the knitting machine cycle,
thereby selecting which of the individual ribbons are to be colored. It is thereby
possible to program the system to color any particular area of the knitted net,
including lengthwise, widthwise, strips or in any other desired pattern.
In one preferred embodiment, the coloring apparatus includes a roller
which rotates in a bath of colored ink. The ribbons are colored by contacting the
roller and will remain uncolored when not contacting the roller. A control system
may be provided for raising the ribbons from the roller and may include an electromagnetic
or pneumatic piston which is operated in accordance with signals coming from a
real time control system. Alternatively, the complete coloring apparatus may be
moved down and out of contact with the ribbons.
Preferred embodiments of the invention will now be described, by
way of example only, with reference to the accompanying drawings, in which:
- Figure 1 shows an apparatus for the production of knitted netting including
the coloring apparatus in accordance with the invention;
- Figure 2 is a side sectional view of the coloring apparatus;
- Figure 3 is a front partially sectional view of the coloring apparatus;
- Figure 4 is a side sectional view of an alternative embodiment of the coloring
- Figure 5 is a perspective view of a further alternative embodiment of the coloring
- Figure 6 is a perspective view of a further alternative embodiment of the coloring
In the following detailed description of the drawings wherein several
alternative embodiments of the invention are discussed, like components are given
like numeral designations for convenience.
In Figure 1 is shown an apparatus for producing knitted netting.
A primary film, e.g. linear low density polyethylene (LLDPE) is supplied on rolls
2. The primary film enters drawing unit 4 which slits and orients the primary
film into individual ribbons 6. A drawing unit appropriate for this purpose is
the ISO In-Line Drawing Unit for tape yarns from Karl Mayer (Germany). The individual
ribbons 6 exit the drawing unit and enter knitting machine 8 via alignment rollers
10. Knitting machine 8 knits the individual ribbons 6 into a continuous Raschel
knitted net 14. Appropriate knitting machines for this purpose is the Raschel
machine from Karl Mayer (Germany) or similar machines. The continuous knitted netting
14 is wound onto roll 16 by winding machine 12.
In accordance with the invention, coloring apparatus 18, interposed
between drawing unit 4, where the primary film is slit and oriented into individual
ribbons, and knitting machine 8, where the knitted netting is actually knit. Coloring
apparatus 18 includes alignment roller 20, coloring roller 22 and contact roller
24. Coloring roller 22 is located in vessel 30 and is connected by drive belt 32
to motor 26. Alternatively, the coloring roller may be driven by direct motor
connection. Movement of contact roller 24 is controlled by control 28 to engage
or disengage the individual ribbons 6 from contact with coloring roller 22.
It will be appreciated from Figure 1 that the preferred point in
the net production process to color the individual ribbons is after the ribbons
are oriented and before the ribbons are knitted into the net. If coloring is performed
before orientation, the colored ink which colors the ribbon will be spread over
an area 5-7 times longer than the original area because of the drawing process
during ribbon orientation. The color will, therefore, become very dull. There may
also be unexpected reactions of the colored ink on the ribbon because of the heat
which is needed for orientation.
In Figure 2 is shown a side sectional view of the coloring apparatus
in accordance with the invention. The coloring apparatus includes a vessel 30 filled
with a desired colored ink 34 to a predetermined level. The preferred colored
ink includes a basic coloring agent NEWFLEX OD C/41 made by SUNCHEMICAL and may
be mixed with a solvent that evaporates quickly. Various paints may also be used.
Inside the vessel there is a rough coloring roller 22 which has about
half of its diameter immersed in the colored ink 34 and which rotates on an axle
36. The coloring roller 22 is a simple rough metal axle with a knurled roller
surface. The axle 36 is supported by two sealed bearings 38. A length 40 of the
axle protrudes through the walls of the vessel 30 and beyond the bearings 38.
A small motor 26 rotates the coloring roller 22 via drive belt 32 connected to
the protruding length of the axle.
The individual ribbons 6 pass transverse to the axial direction of
the coloring roller 22 and contact the upper circumference of the coloring roller.
When in contact with the coloring roller 22, the colored ink will color one side
of the individual ribbons 6 as the coloring roller 22 rotates in colored ink 34.
In accordance with signals from a real time control system, rotation
of the coloring roller may be controlled. Such control systems for the dyeing and
printing of materials are known in the art and are described, e.g. in US Patent
No.3,969,779. When the coloring roller does not rotate, colored ink does not reach
the upper portion of the coloring roller circumference and the coloring of the
individual ribbons ceases.
Alternatively, as shown in Figure 3, contact roller 24 may be positioned
downstream of rough roller 22 and controlled by electromagnetic or pneumatic piston
44 to alter the path of travel of individual ribbons 6. When piston 44 is retracted,
contact roller 24 allows contact between individual ribbons 6 and coloring roller
22. When extended, contact roller 24 alters the path of travel of individual ribbons
6 thereby preventing contact between the individual ribbons and coloring roller
22. In the extended position, no coloring of the individual ribbons occurs despite
continued rotation of the coloring roller.
Two-sided coloring of the ribbons can be accomplished by repositioning
the ribbons so that the ribbons contact the lower circumference of the coloring
roller 22. In Figure 4, an entrance roller 46 and an exit roller 48 are provided
at vessel 30 to direct the path of travel of individual ribbons 6 to the underside
of coloring roller 22.
In accordance with this embodiment, the path of travel of the individual
ribbons 6 is directly through the colored ink 34 and in contact with coloring roller
22 thereby coloring both sides of the individual ribbons. Electromagnetic or pneumatic
piston 46 is provided to raise and lower coloring roller 22 and motor 26 to bring
coloring roller 22 in and out of contact with individual ribbons 6.
In this case, when coloring is to be stopped, the coloring roller
is raised in order to allow free passage of the individual ribbons. In its raised
position individual ribbons 6 travel directly from entrance roller 46 to exit
roller 48 without contacting either coloring roller 22 or colored ink 34.
Accordingly, no coloring of individual ribbons 6 occurs in this condition.
As another alternative embodiment of the invention, the coloring
apparatus may be implemented utilizing capillary action. As shown in Figure 5,
a cylindrical vessel 52 is filled with colored ink 34 to about half its diameter.
A thread 56 is held by a thread support 58 located perpendicular to the passage
of the individual ribbons 6 and is immersed into the colored ink 34.
As the ribbon 6 passes through the thread support 58, the ribbon
contacts the upper portion of the thread 56 which is wet with colored ink because
of capillary action. It may be appreciated that a particular advantage of this
embodiment is that no moving parts are required for the coloring apparatus itself.
If an interruption in coloring is desired, the ribbon 6 is simply moved upward
and out of contact with the thread by a pneumatic or electromagnetic cylinder 60
with ribbon guide 62.
Control of the movement of the above-described rollers and pistons
may be obtained via electromagnetic or pneumatic devices as are commonly known
in the art and may be maintained under computer programmed control. A movement
of about 1-3mm is sufficient to break the contact between the coloring device and
the individual ribbons. When the ribbons are raised, contact between the coloring
device and the individual ribbons is broken and coloring ceases. It will be appreciated
that this method and apparatus for producing colored knitted net is extremely
versatile and with appropriate control any colored pattern may be created.
As a further embodiment, the coloring apparatus may also be implemented
using an ink jet printer as shown in Figure 6. Ink jet 64 is positioned directly
above individual ribbons 6 and is connected via feed line 66 to a colored ink
supply and via connection 68 to an appropriate control system. An appropriate ink
jet printer is ALPHA JET by Metronic Geratebau GmbH & Co. (Germany).
Ink jet printers create an electrostatic field which moves the ink
jet in order to create letters and other complex patterns. For printing on ribbons,
however, all that is required is on/off control of the ink jet. Ink jet equipment
works very fast creating a printed line 3mm thick at a speed of 600 m/min. At this
rate, an ink jet can print by line scanning (similar to a printer wherein the
print head moves horizontally and the paper moves vertically) at a rate of about
1.8 sq. m/min. This printing rate is sufficient for coloring oriented ribbons.
It will be appreciated that an advantage of this embodiment is that the ribbons
which are to be colored may be scanned and colored by the ink jet printer under
computer program control, instead of mechanically picking-up the ribbons when the
ribbons are not to be colored.
Advantageously, the ability of having full program control of the
position of "jet on" or "jet off" signals allows continuous control as to which
(and when) individual ribbons will be colored. This particular embodiment may
also be implemented with less physical equipment than previously described embodiments.