The present invention relates to an oscillating control
device for thread-guide bars of linear knitting machines, also known as Raschel-type
warp looms, tricot, crochet or the like.
As is known, Raschel-type linear knitting machines are
provided with a plurality of bars designed to carry a plurality of thread-holding
elements, commonly known as thread-guides. Said bars should be moved so as to enable
the threads associated to the thread-guides to be correctly fed onto the needles
of the knitting machine for the formation of new fabric with the well-known technique
in which the new thread enters the old loop and the old loop is discharged and becomes
part of the fabric being formed. In order to achieve its knitting task, the thread-guide
bar makes two basic movements simultaneously, i.e. a first linear movement in front
of the hook of each needle, commonly known as "shog", and an oscillating movement
on the side of each needle for bringing the threads alternatively before and behind
the needle hook, commonly known as "swing".
The present invention relates to a device for enabling
the oscillating movement ("swing") for the thread-guides.
Currently, in linear knitting machines the oscillation
of the thread-guide bars, which is usually of 4° to 10°, is obtained by
means of several methods, all of which exploit leverage systems, such as quadrilaterals,
suitably connected to one another and derived from systems for handling the rising
and descent of needles for the formation of the knitted stitch, as is shown for
instance in documents
. Accordingly, the whole mechanism of the machine is rigorously synchronized
in its basic movements, whatever the speed at which the machine is running.
As is known, thread-guide bars, eight of them being generally
present on double needle-bed machines, are associated to at least one support, which
is in its turn connected to said leverage systems for transmitting the oscillating
movement thereof. Said bars are connected to two supports, each of them being placed
on one of the end portions thereof. If necessary, it can further be provided for
intermediate resting supports, which can both actively transmit the oscillating
movement and be passively subjected to it.
As was already said, the leverages convert the linear movement
resulting from the needles into an oscillating movement for the thread-guide bars.
As a matter of fact, the oscillating movement is generated by the movement of a
rod connected to the support of the thread-guide bars so as to make it rotate around
the axis of the shaft supporting it. As a rule, as can be seen in figure 1, the
support of the thread-guide bar is made up of a main body to which the bars as connected,
and of a supporting arm, upon which the rod acts and which has a main axis basically
perpendicular to the main axis of the main body. Moreover, the support is associated
to the shaft supporting it on the point of connection between the arm and the main
body, which is also the center of rotation for said support. This particular structure
allows to obtain an oscillating movement for the main body starting from the linear
movement of the arm obtained by means of the rod.
Known devices as disclosed above show various drawbacks.
Firstly, the systems for transmitting motion from the motor of the machine to the
thread-guide bars are quite complex, since they have to be extremely accurate because
of the narrow spaces in which needles and thread-guides work with respect to the
overall size of the machines, and require a very large number of components. This
increases costs hugely. Moreover, the mechanical complexity of the devices strongly
limits their speeds of use, and thus said machines often represent a bottleneck
in the manufacturing system into which they are integrated.
Secondly, said devices have a very low flexibility, since
it is very difficult to make after-changes to them because of their complexity.
Even maintenance operation for repairing or replacing elements can be complex. Anyhow,
these operations require the intervention of specialized personnel working for the
company that has made the machines, with subsequent problems of production stops
and further cost increase.
Eventually, another problem with known systems consists
in the need to continuously invert the direction of movement of the support, and
thus of the thread-guide bars, so as to make oscillations. As a matter of fact,
the masses involved, which are quite high, have to be pushed in one direction, so
as to create a counterclockwise oscillation for instance, then at stroke end they
have to be braked and pushed in the opposite direction, so as to make the following
clockwise oscillation for instance. Such a device, therefore, gives rise to several
mechanical problems leading inevitably to solutions involving large overall sizes
of stressed components and strong reductions of operating speeds. Moreover, said
devices generate very strong vibrations that have to be absorbed by the machine
through suitable measures, such as for instance big anti-vibration supporting structures.
The state of the art shows devices mitigating the problem
disclosed above, though further increasing costs.
They are basically made up of eccentric systems based on
the principle of connecting rod-crank imparting a sinusoidal movement to the support,
as shown in Figure 2. The sinusoidal movement of the connecting rod slows down the
stroke of the support on the point of inversion of the movement, thus greatly reducing
vibrations and discharging the forces of inertia generated on the various mechanical
connections as far as the motor.
Moreover, known knitting machines can include even more
than two of the conventional devices associated to the ends of the thread-guide
bars. For instance, in a machine with a needle-bed having a length of about 3.5
m, there can be 8 devices spaced from one another of about 0.5 m. As a matter of
fact, the use of several devices enables to reduce size and, therefore, to obtain
higher speeds of use. However, in this case the size of the motor and of the shaft
connected thereto significantly increases, since eight of these devices are fitted
onto the shaft, together with other devices involved in the movement of needles
and other elements, which devices increase the forces of inertia involved due to
the masses in movement that have to be moved in a suitable manner both at constant
speed and during acceleration or braking.
It should be pointed out that, generally, these devices
are located in the portion containing the rear needle-bed, thus leaving the front
portion of the machine free for different reasons, also of economical nature. Therefore,
the system is not balanced and gives rise to vibrations occurring also at low speeds
(350 oscillations per minute for instance).
The aim of the present invention is to solve the problems
at the state of the art by proposing an oscillating control device for thread-guide
bars of linear knitting machines without the drawbacks described above. Therefore,
an aim of the present invention is to propose an oscillating control device for
thread-guide bars of linear knitting machines that enables to reduce the manufacturing
and management costs of the knitting machines. As a consequence, an aim of the invention
is to provide an oscillating control device for thread-guide bars of linear knitting
machines that has a small number of components and enables to simplify the structure
of the machine and the construction and management thereof, especially as far as
maintenance is concerned.
A further aim of the invention is to show an oscillating
control device for thread-guide bars of linear knitting machines that is very accurate
and ensures a high quality of the finished item.
Still another aim of the present invention is to increase
the operating speed of the knitting machine so that the knitting station represents
no more a bottleneck in the whole manufacturing process of knitted items.
Moreover, an aim of the invention is to show an oscillating
control device for thread-guide bars of linear knitting machines that generates
on the supports, and therefore on the thread-guide bars, a controlled and balanced
oscillating movement especially in the critical steps of acceleration, braking and
movement inversion, so that a strong over-sizing of the structural components of
the machine is not required and the generation of vibrations and shakes is reduced.
A final aim of the invention is to show an oscillating
control device for thread-guide bars of linear knitting machines that enables to
balance the forces acting upon the machine, so that the knitting machine has a compact,
rational and dynamically balanced structure.
These and other aims that will emerge from the following
description are achieved, according to the present invention, by an oscillating
control device for thread-guide bars of linear knitting machines in accordance with
the appended claims.
The invention will now be disclosed in further detail thanks
to the drawings, which represent a merely exemplary and non-limiting embodiment
- Figures 1 and 2 show examples of known oscillating control devices for thread-guide
bars of linear knitting machines;
- Figure 3 shows a side view of an oscillating control device for thread-guide
bars of linear knitting machines in accordance with the invention;
- Figure 4 shows a first schematic front view of a knitting machine according
to the invention in a first embodiment thereof;
- Figure 5 shows a schematic front view of a detail of the machine according to
- Figure 6 shows a top view of the machine according to the invention in the first
- Figure 7 shows a perspective view of the device of Figure 3 associated to a
first end portion of the thread-guide bars;
- Figure 8 shows a perspective view of the device of Figure 3 associated to a
second end portion of the thread-guide bars;
- Figure 9 shows a second schematic front view of the machine of Figure 4;
- Figure 10 shows a schematic side view of the machine according to the invention
in a second embodiment thereof.
With reference to the figures mentioned above, an oscillating
control device 1 for thread-guide bars 2 of linear knitting machines 60 according
to the present invention comprises a support 5 that can rotate around a middle axis
6 to which at least one thread-guide bar 2 can be associated, movement means 10
for the support 5, and transmission means 20 operatively connected to the movement
means 10 for imparting an oscillating movement to the support 5.
The device 1 is characterized in that the transmission
means 20 are operatively associated to the support 5 on at least two separate actuating
points 7a, 7b for moving it with an oscillating movement in a balanced manner with
respect to the middle axis 6 thereof.
As can be seen in figure 3, said points 7a, 7b for actuating
the support 5 are opposed with respect to a vertical plane containing the middle
axis 6. Moreover, a pushing action and a pulling action are applied simultaneously
on the two actuating points 7a, 7b, respectively, by the movement means 10 through
the transmission means 20. In further detail, every time the support 5 moves with
an oscillating movement, a pushing action is applied on one of two actuating points
7a, 7b and a pulling action is applied on the other one. As a consequence, these
devices 1 can also be defined "push-pull" devices.
It is thus possible to balance the forces acting upon the
device 1 and to control their dynamics effectively. Moreover, the oscillating movement
of the support 5 takes place in a plane basically perpendicular to the longitudinal
development of the thread-guide bars 2, so that the middle axis 6 of said support
5 is basically parallel to the main axes of the thread-guide bars 2.
The transmission means 20 comprise main transmission means
21 operatively connected to the movement means 10, and secondary transmission means
25 operatively connected to the main transmission means 21 and moved by the latter.
The main transmission means 21 act upon the support 5 on a first actuating point
7a, whereas the secondary transmission means 25 act upon it on a second actuating
point 7b (Figures 3 and 6).
Advantageously, therefore, the main and secondary transmission
means 21, 25 exert onto the support 5, by means of the corresponding actuating points
7a, 7b, the pushing action and the pulling action, respectively, for oscillations
in one direction and vice versa for oscillations in the other direction.
The transmission means 20 further comprise connection means
30 between the main transmission means 21 and the secondary transmission means 25,
so as to transmit synchronously to the secondary transmission means 25 the movement
supplied by the movement means 10 through the main transmission means 21 (Figures
3 and 6).
According to the invention, the main transmission means
21 comprise a main shaft 22 operatively connected to the movement means 10, and
a main connecting rod 23 operatively associated to the main shaft 22 and to the
support 5 on the first actuating point 7a. A further component of said means 21
is a main eccentric pin 24 associated to a portion of the main shaft 22, preferably
to an end portion thereof, so that the main connecting rod 23 is fitted onto the
main shaft 22 by means of said main eccentric pin 24 (Figure 4).
In their turn, the secondary transmission means 25 comprise
a secondary shaft 26 operatively associated to the connection means 30, and a secondary
connecting rod 27 operatively associated to said secondary shaft 26 and to the support
5 on the second actuating point 7b.
Preferably, the secondary transmission means 25 also comprise
a secondary eccentric pin 28 associated to a portion, as a rule an end portion,
of the secondary shaft 26. Here again, the connecting rod 27 is fitted onto the
secondary shaft 26 by means of said secondary eccentric pin 28.
The secondary connecting rod 27 is designed to cooperate
with the main connecting rod 23 for moving the support 5 with an oscillating movement.
The two shafts, the main one 22 and the secondary one 26,
rotate synchronously, whereas their connecting rods 23, 27 operate with phase opposition
due to the different location of the eccentric pin 24, 28 of the respective shafts
22, 26. Therefore, while one of them, the main connecting rod 23 for instance, pushes
the support 5 and makes it rotate with respect to its middle axis 6 counterclockwise,
the other one, the secondary one 27 for instance, pulls simultaneously the support
5 cooperating with the main connecting rod 23 so that said support rotates counterclockwise
in a balanced manner.
Advantageously, the oscillating movement imparted by the
main connecting rod 23 and by the secondary connecting rod 27 to the support is
sinusoidal and dampened at its ends, i.e. during movement inversion. This allows
to maximize the effectiveness of the movement since, both during acceleration and
during braking, the two connecting rods 23, 27 cooperate to the movement by sharing
in a fair manner the efforts and the absorptions of the forces of inertia generated
at high oscillating speeds. Thus, this results in a harmonious movement without
all negative components generated in known devices 1 moved with means operating
only on one side, i.e. with only one connecting rod.
The connection means 30 comprise a main pulley 31 integrally
associated to the main shaft 22, a secondary pulley 32 integrally associated to
the secondary shaft 26, and a connection belt 33 associated to the two pulleys 31
and 32 for transmitting the movement of the main pulley 31 to the secondary shaft
26 exactly by means of the secondary pulley 32. Generally, in double needle-bed
linear knitting machines 60, every support 5 is associated to approximately eight
thread-guide bars 2. Preferably, the bars 2 are not associated to the support 5
directly but by means of secondary supports 8, to which only one bar 2 can be associated
and which are integral with the support 5, as shown in Figures 3, 4, 5, 7 and 8.
It should be pointed out that every secondary support 8 is integral with the support
5 as far as rotation is concerned, while it can move with translational motion with
respect to the support 5 so as to enable the translation of the bars 2 as required
for the movement of said bars 2 commonly known as "shog".
In a first execution variant shown in detail in Figures
4, 6 and 9, which is also the preferred embodiment of the invention, the movement
means 10 comprise at least one dedicated motor 11. This dedicated motor 11 is designed
only to move the support 5 and is different from the central motor 13 moving the
other elements of the machine 60 such as the needles.
In this case, therefore, the main shaft 22 is integrally
connected to the dedicated motor 11, and the main connecting rod 23 is designed
to convert the rotational motion of the main shaft 22 generated by the dedicated
motor 11 into an oscillating motion for the support 5.
Preferably, the dedicated motor 11 is a brushless motor,
but other types suitable to this purpose can be used, such as stepper motors or
direct current motors. As an alternative, two dedicated motors 11 synchronized with
one another can be used, so as to move the main 21 and the secondary 25 transmission
means, thus without the need for connection means 30 whose function is to move the
secondary transmission means 25 starting from the movement of the main ones 21.
Said solution, however, would be highly complex to be carried out and managed, especially
due to the need for a perfect synchronization between the two dedicated motors 11,
and would significantly increase costs.
In a second execution variant of the invention shown in
Figure 10, the movement means 10 can be operatively associated to the central motor
13 of the machine 60. It should be pointed out that central motor 13 denotes the
motor designed to move all the elements of the machine 60 and in particular the
needles. In this case, therefore, the movement means 10 comprise a first movement
pulley 14 operatively associated to the main shaft 22, a second movement pulley
15 that can be operatively associated to the central motor 13, and a movement belt
16 operatively connected to the first 14 and to the second 15 movement pulley for
transmitting to the first movement pulley 14 the movement of the second movement
Advantageously, the movement means 10 can further comprise
first means 17 for varying the rotational speed of the main shaft 22 with respect
to the rotational speed of the central motor 13, associated to the movement belt
16. In further detail, said means 17 consist of reduction gears and are required
when the main shaft 22 has to be moved at another angular speed than the one of
the central motor 13 to which it is connected and from which it receives the movement,
as typically occurs in double needle-bed linear knitting machines 60.
The inventive idea underlying the present invention extends
also to a linear knitting machine 60 characterized in that it comprises at least
one oscillating control device 1 for thread-guide bars 2 in accordance with the
In particular, a linear knitting machine 60 in accordance
with the invention generally comprises at least two oscillating control devices
1 for thread-guide bars 2. Preferably, one of these devices 1 is located on a first
end portion 3 of the thread-guide bars 2, and another one is located on a second
end portion 4, opposite the first one 3, so as to prevent torsions of said thread-guide
bar 2 during oscillations.
The machine 60 can further comprise at least one intermediate
support 9 associated to the thread-guide bars 2 on an intermediate portion 2a thereof,
located between the two end portions 3, 4, so as to support the latter (Figure 5).
Every intermediate support 9 can move with an oscillating movement around the central
axis. Preferably, the intermediate supports 9 do not transmit to the thread-guide
bars 2 the oscillating motion but only accompany the oscillations thereof by passively
absorbing them. In some cases, however, the intermediate supports 9 can also actively
transmit the oscillating movement to the bars 2 (which alternative is not shown).
Advantageously, every support 5 and every intermediate
support 9 are turnably associated to an oscillating shaft 18 whose main axis coincides
with the central axis 6 around which said supports 5 rotate. Advantageously, the
thread-guide bars 2 can be associated to every intermediate support, which houses
all thread-guide bars 2, by means of a secondary intermediate support, as can be
seen in Figure 5.
The knitting machine 60 further comprises control means
40 designed to ensure the synchronism between the oscillating movement of the supports
5 of the two devices 1 associated to the end portions 3, 4 of the thread-guide bars
2, and to ensure the continuity of movement for the thread-guide bars 2 in case
of failures. Said control means 40 comprise an auxiliary shaft 41 operatively associated
to the secondary shafts 26 of the two devices 1, so as to stiffly connect said secondary
shafts 26 (Figures 5 and 6).
The auxiliary shaft 41 has several functions beyond the
one of ensuring the perfect synchronism between the two secondary shafts 26 as mentioned
above. As a matter of fact, the auxiliary shaft 41 enables to ensure the continuity
of movement in case some components break, such as a connection belt 33 between
the main transmission means 21 and the secondary ones 25 of one of the two devices
1, since the auxiliary shaft 41 can move the secondary shaft 26 of the damaged device
1 by exploiting the movement of the secondary shaft 26 of the undamaged device 1.
The same applies to a breakage or malfunctioning of the movement means 10, especially
of the dedicated motor 11 in the first execution variant of the devices 1. However,
the machine 60 is equipped with suitable sensors that are able to signal the emergency
condition and to stop said machine 60 with suitable procedures.
Moreover, the auxiliary shaft 41 is adequately supported
and perfectly able to rotate on its axis 42 at high speeds without causing unwanted
vibrations in the transmission means.
A linear knitting machine 60 with oscillating control devices
1 for thread-guide bars 2 according to the first execution variant also comprises
coordination means 50 between the central motor 13 and the dedicated motors 11 for
adapting the movement of the dedicated motors 11 to the movement of the central
motor 13 so as to synchronize the movement of the thread-guide bars 2 to the one
of the needles. This function is highly important since the movements of the thread-guide
bars 2 and of the needles have to be extremely stiff and coordinated so that all
the needles are always correctly fed, thus preventing damages to the finished product
or breakage of threads or needles.
Said coordination means 50 can be either electronic or
In the first case, the coordination means 50 comprise at
least one first detection element 51 associated to the central motor 13, designed
to detect the angular position thereof, at least one second detection element 52
for each of the dedicated motors 11, designed to detect the angular position thereof,
and an electronic adjustment element (not shown) designed to process the signals
transmitted by the first 51 and by the second 52 detection elements so as to synchronize
the dedicated motors 11 with the central motor 13 (Figures 4 and 9). For instance,
the electronic adjustment element can be an electronic card connected to the electronic
means running and managing the whole machine 60. Moreover, the first 51 and the
second 52 detection elements can comprise position transducers of "encoder" or "resolver"
type or of other type, which are able to indicate the exact angular position of
the shaft moving with respect to a reference zero. In particular, the signal referring
to the central motor 13 is commonly managed as main signal ("master signal") with
which all the other movements of the machine 60 have to comply.
This allows to eliminate cams, back gears, leverages, rods,
etc. which are required to connect stiffly and synchronously elements spaced apart
even of some meters and which were difficult and expensive to be carried out. Despite
being of electronic type, the coordination means 50 of this type are able to connect
stiffly the central motor 13 to the dedicated ones 11, as if there were actually
a stiff mechanical connection between them.
The rapidity of data transmission and execution makes the
movement between the central motor 13 and the dedicated motors 11 harmoniously connected
and rigorously controlled, since the coordination means 50 can follow in real time
speed variations of the central motor 13 and adapt the mechanisms thereof under
their control, in this case the dedicated motors 11.
As was already mentioned, the coordination between the
central motor 13 and the dedicated motors 11 can also take place with mechanical
coordination means 50 making use of conventional transmission. In this case, the
coordination means 50 comprise at least one first coordination pulley 53, each of
them being associated to each of the dedicated motors 11, a second coordination
pulley 54 associated to the central motor 13, and a coordination belt 55 operatively
connected to the first 53 and to the second 54 coordination pulley so as to move
the first coordination pulley 53 according to the movement of the second one 54.
The coordination means 50 can further comprise second means 56 for varying the rotational
speed of the first coordination pulley 53 with respect to the second one 54, generally
made up of reduction gears.
Moreover, in this case every dedicated motor 11 comprises
two shafts, a first shaft made up of the main shaft 22, and a second shaft made
up of a coordination shaft 57 operatively connected to the first coordination pulley
This type of coordination means 50, which is perfectly
functional, can introduce some delays due to the imperfect stiffness of the coordination
belts 55, which delays are mitigated by reducing the operating speed of the machine
The two types of coordination means 50 can also be used
simultaneously so as to minimize the possible lack of synchronization between the
central motor 13 and the dedicated motors 11 in case of breakages or failures of
the various components.
In the solution of embodiment in which a linear knitting
machine 60 comprises oscillating control devices 1 for thread-guide bars 2 according
to the second execution variant, the central motor 13 has two shafts. As a matter
of fact, said motor 13 has two shafts made up of the movement shafts 12 operatively
connected to the second movement pulleys 15 of the two devices 1 associated to the
first 3 and to the second 4 end portion of the thread-guide bars 2, respectively.
It should be pointed out that, preferably, all the belts
and pulleys are toothed. However, the terms belt and pulley are to be construed
as general terms representing any transmission element designed to perform the functions
required by a knitting machine 60 in accordance with the inventive idea as described.
The invention thus conceived can undergo several changes
and variants, all of which fall within the framework of the inventive idea.
In practice, any material or size can be used, depending
on the various needs.
Moreover, all details can be replaced by technically equivalent
The invention achieves important advantages.
Firstly, the presence of transmission means performing
simultaneously a pushing and a pulling action onto the support makes the inversion
of the direction of movement and the steps of acceleration and braking gradual and
smooth. This enables to limit the size of the mechanical structure of the machine
and the stresses (vibrations, shakes, ...) it undergoes during operation.
The structure of the machine is further simplified and
made lighter in both execution variants as described also thanks to the particular
shape of the movement means. As a matter of fact, in the first execution variant
the use of dedicated motors allows to reduce the number of elements controlled by
the central motor of the machine, which can therefore be reduced in size. In this
embodiment, the structure of the machine is further reduced by using electronic
coordination means positively affecting also the flexibility of the machine itself.
In the second execution variant, the complicated leverages of known machines are
replaced by a simple transmission system using preferably pulleys and belts. This
makes the knitting machine simpler to be carried out and managed, especially as
far as maintenance is concerned, and significantly reduces the costs thereof. Furthermore,
the use of a push-pull system enables to balance the structure of the knitting machine
and to reduce significantly its vibrations. For instance, the knitting machine according
to the present invention allows to reduce vibrations also at a speed of 3,000 and
more oscillations per minute.
Thanks to the lighter structure and the fewer vibrations,
the devices according to the present invention can operate at high speeds reducing
the criticalities of the knitting step with respect to the other steps of the manufacturing
process of knitted items.
Finally, a further advantage consists in that the described
devices, by controlling the oscillating movement and ensuring a high accuracy, ensure
a high quality of the knitted items thus manufactured.