The present invention relates to a driving mechanism for the control
of the needle-bar and tube-bars in fast knitting machines, of the type comprising;
a support bed provided with at least two side posts; at least one drive shaft
rotatably engaged through each of said posts; a pair of swinging arms each rotatably
connected to one of said posts and fixedly engageing a needle-bar; a pair of first
driving connecting rods each of them exhibiting one end pivoted to one of said
swinging arms and the opposite end operatively engaged on one eccentric carried
by said first drive shaft; a second drive shaft rotatably engaged to each of said
posts; a pair of oscillating supports each of them being slidably engaged in a
vertical direction with one of said posts and engaging at least a tube-bar at
one end thereof; a pair to second driving connecting rods each exhibiting one end
connected to one of said oscillating supports and the opposite end operatively
engaged with a second eccentric carried by the second drive shaft; said first and
second drive shafts being driven simultaneously in rotation in order to respectively
cause the operation of the needle-bar according to a horizontal oscillatory movement
and the operation of the tube-bar according to a vertical oscillatory movement.
It is known that in fast knitting machines the needle-bar is fastened
by its opposite ends to two swinging arms which are pivoted, according to a horizontal
axis, to two posts forming part of the machine bed. Acting upon each of said swinging
arms is one driving connecting rod operatively engaging with a respective eccentric
mounted to a main shaft the opposite ends of which are rotatably engaged through
said posts. The main shaft is driven in rotation by a motor in order to impart
an oscillatory movement in a substantially horizontal direction to the needle-bar,
through the eccentrics, first driving connecting bars and swinging arms.
The rotation of the main shaft is transmitted, by a pair of toothed
belts or the like acting on the opposite ends of the main shaft, to a pair of second
shafts each of which is rotatably engaged to one of the posts. Associated with
each of said second shafts is a second eccentric operatively engaging a second
driving connecting rod. The second driving connecting rods give rise to the movement
of two oscillating supports each of which is slidably engaged with two guide rods
upstanding from the corresponding post.
Engaged with the oscillating supports by its opposite ends is at
least a tube-bar carrying a number of threading tubes arranged such as to cooperate
with the needles carried by the needle-bar and with other instrumentalities of
the knitting machine in order to carry out the knitting of the workpiece.
Due to the rotation transmitted to the second drive shafts, the second
connecting rods actuate the supports, and hence the tube-bar or bars transmitting
a substantially vertical oscillatory movement to the same.
Also operating on the tube-bars is a second driving mechanism which,
actuated by a so-called "glider chain" transmits an oscillatory movement in a horizontal
direction to the bars themselves, which movement is vectorially combined with
the vertical oscillations transmitted by the above described driving mechanism.
It is to be noted that one of the most important problems connected
with fast knitting machines resides in the strong vibrations to which said machines
are submitted when they are actuated at high speed. Obviously due to the presence
of these vibrations it is impossible to increase the work speed beyond given values,
which brings about a limitation in the productivity of these machines.
In addition, due to said vibrations the different parts of the machine
are submitted to high mechanical stresses and it is therefore necessary to provide
the machine with heavy beds and frameworks in order to ensure a sufficient steadiness
to the same.
Most of the above vibrations have been found to be caused by the
reciprocating horizontal movement of the needle-bar and the reciprocating vertical
movement of the tube-bars. In fact, each of said bars as well as the different
elements connected thereto, form an important mass which is submitted to high decelerations
and accelerations each time a reversal of movement occurs. As a result of said
accelerations and decelerations there are high forces of inertia which are directly
transmitted to the machine framework.
In the light of the above discussed drawbacks, the main object of
the present invention is substantially to solve the problems of the known art by
providing a driving mechanism set up in such a manner that it eliminates all vibrations
caused by the horizontal oscillatory movement of the needle-bar and vertical oscillatory
movement of the tube-bars.
Document GB 948, 868 discloses a flat warp knitting machine comprising
sets of needles, needle tongues, guide eyes and sinkers, each of which sets being
mounted on a separate bar driving member.
Each of such bar driving members is reciprocated by a pivotal link
connected with a respective pivoted member. The pivoted member is oscillated trought
90° by a respective connecting rod. The connecting rods are driven from a single
krank-shaft. Balance weights are connected each to the respective pivoted member,
by another pivotal link.
This construction allows to reduce the vibrations due to the reciprocating
of the above cited bar diving members, but it is suitable to be used only on flat
warp knitting machines, where warp yarns are knitted into a fabric which passes
across to a predetermined knitting point. By contrast, such a construction is not
suitable to be used on fast knitting machines designed to form a fabric by knitting
weft yarns with warp yarns.
The above-mentioned object, which will become more apparent from
the following description, is attained by driving mechanism for the control of
the needle-bar and tube-bars in fast knitting machines, characterized in that
it comprises: at least a pair of auxiliary swinging arms each pivoted to one of
said posts; at least a pair of first counterweights each integral to one of said
auxiliary swinging arms; at least a pair of first auxiliary connecting rods each
of them exhibiting one end pivoted to one of said auxiliary swinging arms and
the opposite end operatively engaged with one auxiliary eccentric mounted on the
first drive shaft; at least a pair of second counterweights each associated with
one of the posts and slidably guided in a vertical direction; at least a pair of
second auxiliary connecting rods, each of them exhibiting one end pivoted to one
of the second counterweights and the opposite end operatively engaged with a second
auxiliary eccentric carried by the corresponding second drive shaft; said first
and second auxiliary eccentrics being mounted in phase opposition relative to said
first and second eccentrics in order to cause said first and second counterweights
to oscillate in phase opposition relative to the oscillations performed by the
needle-bar and tube-bars.
Further features and advantages of the invention will best be understood
from the detailed description of a preferred embodiment of the driving mechanism
for the control of the needle-bar and the tube-bars in fast knitting machines
given hereinafter by way of non-limiting example with reference to the accompanying
drawing in which the only figure is a perspective fragmentary view of one half
of the driving mechanism in question mounted on a fast knitting machine, the other
half being substantially identical to and arranged in a mirror image of the first
Referring to said drawing, a mechanism for the control of the needle-bar
and tube-bars in fast knitting machines according to the invention has been generally
identified by reference numeral 1.
The driving mechanism 1 is mounted to a pair of posts 2, only one
of which is shown in the figure, forming part of a support bed conventionally provided
in the knitting machine with which said driving mechanism is associated. In greater
detail, the driving mechanism is formed of two half parts each mount on one of
said posts 2. For the sake of clarity, during the following description reference
will be made, except in case of need, to the half part of the driving mechanism
associated with post 2 herein shown, the other half part being substantially identical
to and arranged in a mirror image of the first one.
In known manner, the driving mechanism 1, as shown by arrow 3a, is
designed to impart a substantially horizontal oscillatory movement to a needle-bar
3 extending between the posts 2 of the bed and supporting a number of needles
4 suitably distributed over the same. The driving mechanism 1 is also designed
to transmit a vertical oscillatory movement, as shown by arrow 5a, to one or several
tube-bars 5 the opposite ends of which are slidably engaged through oscillating
supports 6 (only one of which is shown), each of them being slidably engaged to
a pair of guide rods 7 upstanding from the corresponding post 2.
Still in known manner, the tube-bars 5 are also actuated, by means
of a second driving mechanism not shown as not important to the ends of the invention,
with an oscillatory horizontal movement in a longitudinal direction, as shown
by arrow 5b.
Also shown in the accompanying figure, by way of example only, is
a guide bar 8 supporting a number of eye-pointed needles 9 and provided with an
oscillatory movement consisting of angular oscillations as shown by arrow 8a and
horizontal oscillations as shown by arrow 8b. The driving mechanism for the control
of said guide bar 8 is not shown and will not be described as it is unimportant
to the ends of the present invention.
The driving mechanism 1 comprises at least one drive shaft 10 rotatably
engaged through each post 2. In greater detail, provision is preferably made for
a pair of first drive shafts 10 each associated with one of the posts 2 and driven
in rotation by a single main shaft 11 extending between said posts and rotatable
supported by the posts themselves close to the base thereof.
In greater detail, the main shaft 11, driven in rotation by a "V"
belt 12 connecting it to a motor not shown, transmits a rotatory movement to each
of the first drive shafts 10 by means of a toothed belt 13 operatively engaging
with respective toothed pulleys 10a, 11a, carried by the first drive shaft and
the main shaft itself.
In addition, at least one of the first drive shafts 10 is associated
with a flywheel 14.
The driving mechanism 1 also comprises a pair of first driving connecting
rods 15 each of them exhibiting one end 15a pivoted to a swinging arm 16 in turn
rotatably connected to one of the posts 2 and fixedly engaging the needle-bar
3 at one end thereof. The second end 15b of the driving connecting rod 15 operatively
engages with one eccentric 17 fixedly carried by the corresponding first drive
Advantageously, associated with eachone of the first drive shafts
10 is one auxiliary eccentric 18 mounted in phase opposition, that is rotated through
180°, relative to the first eccentric 17 and preferably having the same eccentricity
as the latter.
Operatively engaged with the first auxiliary eccentric 18 is one
end 19a of one auxiliary connecting rod 19 the opposite end 19b of which is pivoted
to an auxiliary swinging arm 20 rotatably engaged to the corresponding post 2.
Mounted on the auxiliary arm 20 is at least one counterweight 21 preferably exhibiting
a mass equal to half the mass of the needle-bar 3 and at all events sufficient
to cause the assemble consisting of the counterweight 21, auxiliary arm 20, auxiliary
connecting rod 19, auxiliary eccentric 18 to have a mass substantially identical
to the sum of the masses of half needle-bar 3, swinging arm 16, first driving connecting
rod 15 and first eccentric 17.
The driving mechanism 1 further comprises a pair of second drive
shafts 22 each of which is rotatably supported relative to the corresponding post
2. In greater detail, preferably each second drive shaft 22 is rotatably engaged
through a support bracket 23 fastened to the post 2.
The second drive shaft 22 is provided with a toothed pulley 22a operatively
engaging with said toothed belt 19 so as to cause the rotation of the shaft itself.
The second drive shaft 22 integrally carries a second eccentric 24
as well, which is operatively engaged in one end 25a of a second driving connecting
rod 25 the opposite end 25b of which is connected to one of the oscillating supports
Moreover a second auxiliary eccentric 26 is integrally engaged to
each of the second drive shafts 22, which auxiliary eccentric is mounted in phase
opposition relative to the second eccentric 24 and preferably has the same eccentricity
as the latter. Engaged with the second auxiliary eccentric 26 is one end 27a of
a second auxiliary connecting rod 27 the opposite end 27b of which is connected
to a second counterweight 28 slidable guided in a substantially vertical direction.
In greater detail, the second counterweight 28 is slidably engaged on an auxiliary
slide 29 fixedly carried by the support bracket 23. Preferably, the second counterweight
28 has a mass which is substantially equal to half the mass of the tube-bars 4
or at all events sufficient to cause the assembly consisting of the counterweight
28, auxiliary connecting rod 27, auxiliary eccentric 26 to have an overall mass
substantially identical to the sum of the masses of half the tube-bars 4, one of
the oscillating supports 6, one of the second driving connecting rods 25 and one
of the second eccentrics 24.
Operation of the driving mechanism according to the invention described
above mainly as regards structure, is as follows.
As previously said, the rotatory movement imparted to the main shaft
11 is transmitted, through each of the toothed belts 13, to the first and second
drive shafts 10, 22, The rotation of the first drive shaft 10 causes, through
the first eccentric 17, the movement of the connecting rod 15 which, as a result,
makes the arm 16 oscillate about its own pivot axis. Upon oscillation of arm 16,
a substantially horizontal reciprocating movement of the needle-bar 3 according
to arrow 3a occurs.
Simultaneously, the rotation of the first shaft 10 brings about,
through the first auxiliary eccentric 18, the operation of the first auxiliary
connecting rod 19 the oscillatory movement of which also causes the auxiliary
arm 20 to oscillate about its own pivot axis. As a result, the first counterweight
is submitted to an oscillatory movement, as shown by arrow 21a, about the pivot
axis of the auxiliary arm 20. Since the first auxiliary eccentric 18 is 180° offset
with respect to the first eccentric 17, the first counterweight 21 is subjected
to oscillate in phase opposition relative to the needle bar 3. Consequently, the
counterweight 21 and needle-bar 3 will transmit forces of inertia to the post
2, and therefore to the knitting machine as a whole, which substantially have the
same intensity by opposite senses, so that they mutually become null.
The rotation of the second drive shaft 22, in turn, causes the operation
of the second driving connecting rod 25 so that it transmits a substantially vertical
reciprocating movement, as shown by arrow 5a, to the corresponding oscillating
support 6 and therefore to the tube bars 5. At the same time the second auxiliary
eccentric 27a actuates the second auxiliary connecting rod 27 the oscillatory
movement of which causes the second counterweight 28 to move in a substantially
vertical direction as shown by arrow 28a.
Since the second auxiliary eccentric 26 is 180° offset with respect
to the second eccentric 24, the oscillations of the second counterweight 28 will
be in phase opposition relative to those of the tube bars 5. As a result, the
forces of inertia transmitted to the machine structure by the second counterweight
28 and tube-bars 5 will be subjected to become mutually null.
The present invention attains the intended purposes.
In fact, in the driving mechanism described the forces of inertia
produced by the needle-bar and tube-bars are made null by the counterweights actuated
by the same shafts which are designed to move the bars themselves. In this way
all vibrations which in the known art are transmitted to the machine structure
by effect of the above specified forces of inertia are eliminated.
Obviously by eliminating these vibrations important advantages are
achieved, first of all a higher speed in the operation of the knitting machine
and therefore a greater productivity.
In addition, by eliminating said vibrations the stresses currently
produced on the different mechanical parts of the machine are greatly reduced,
which results in a greater liability. A further advantage resides in the possibility
of greatly reducing the mass of the machine bed.
It will be also recognized that the original solution of adopting
two first drive shafts rotated by a main shaft allows the sizes, and consequently
the mass, of the eccentrics actuating the needle-bar to be remarkably reduced.
In fact in known solutions these eccentrics were directly mounted on the main shaft
which necessarily has a big diameter and therefore said eccentrics needed to be