Device for driving needle beds in a circular knitting machine

A circular knitting machine has needle beds; a cylinder and a dial, and means to drive the cylinder and dial including three assemblies symmetrically arranged about three planes which intersect on a line substantially coincident with the machine axis, the assemblies thereby acting to center the cylinder and dial. It is preferred for the assemblies to include shafts and intermediate gears connecting the shafts to crown gears on the cylinder and dial, and for the cylinder to be axially adjustable by means in each assembly relative to the dial.

This invention relates to a device for driving and positioning the needle 
beds of a circular knitting machine of the type having a rotating cylinder 
and a rotating dial. 
In a circular knitting machine with two needle beds, namely a horizontal 
needle bed or dial and a vertical needle bed or cylinder, the synchronous 
rotation of the two needle beds is achieved by means of the dial and a 
large toothed crown or drive wheel being mounted on a central shaft, while 
the cylinder is firmly fixed to a second drive wheel which rotates whilst 
resting on an annular support fixed to the framework of the machine. The 
needle beds are caused to rotate by a motor, via a control shaft connected 
both to the two drive wheels and to the motor by a suitable transmission. 
A perpetual problem in such machine is the centering and accurate 
adjustment of the needle beds. Another problem is as follows. When the 
machine is braked quickly, for example by operation a safety device 
monitoring yarn break, needle disengagement or the like, the central shaft 
supporting the dial undergoes a sudden shock. Each such shock has the 
effect of slightly twisting the central shaft and hence causing 
irregularities in the setting of the needles of the dial relative to the 
needles of the cylinder. These irregularities can eventually become 
sufficiently great to cause deterioration of the needles. It is usually 
attempted to avoid this by supporting the dial on a central shaft of 
larger diameter. However, when the shaft is large enough to resist 
deformation, it is found that the control shaft which drives the needle 
beds receives the shocks and this in turn becomes deformed. Repeated 
shocks on the control shaft can cause a permanent misalignment between the 
drive wheels of the cylinder and dial. As a result, the machine no longer 
turns in a true circle and it produces knitted fabric of faulty 
appearance. 
It has been proposed to overcome this difficulty by reinforcing the control 
shaft with one or two supplementary shafts which are parallel to it, but 
with only one of the shafts being driven directly by motor, the other or 
others being driven by the drive wheels. While this arrangement improves 
synchronisation between the cylinder and dial it does not prevent 
deformation of the motor shaft under the repeated action of the braking 
shocks, because only this shaft, which is connected directly to the motor, 
receives the shocks. 
Another problem arises from the adjustment of the spacing between the lips 
of the two needle beds (in order to adjust the mesh spacing) which is 
usually effected by adjusting the height of the central shaft supporting 
the dial. During this movement, it frequently happens that the dial bends 
or buckles, producing a non-uniform mesh spacing over the periphery of the 
machine and also leading to faulty appearance of the knitted fabric. 
The aim of the present invention is to reduce at least some of these 
difficulties. 
According to the present invention there is provided a circular knitting 
machine having needle beds: a cylinder and a dial and means to drive the 
cylinder and dial, such means including three assemblies symmetrically 
arranged about three planes which intersect on a line substantially 
coincident with the machine axis, the assemblies thereby acting to centre 
the cylinder and dial. 
Preferably the machine includes, in each assembly, a shaft, each shaft 
being drivingly connected to a motor and arranged to drive the cylinder 
and dial, and each shaft having an associated braking system. 
Preferably also, the machine includes, in each assembly, two intermediate 
gear wheels engaging toothed portions on the shaft and respectively 
engaging gear wheels fixed with the cylinder and dial. Advantageously, the 
cylinder has a toothed crown wheel machined directly into the material of 
the cylinder. Means may be provided in each assembly to adjust the axial 
position of the cylinder relative to the dial, and there may be 
comparators to assist in carrying out the adjustment and controlling axial 
spacing at the three points.

FIG. 1 represents the drive arrangement of the needle beds in a 
conventional circular knitting machine which has a dial 1 firmly fixed to 
a central shaft 2 which also carries a drive wheel 3, which engages with a 
gear-wheel 4 fixed at the upper end of a vertical control shaft 5. A 
gear-wheel 6, identical with the gear-wheel 4 and fixed near the bottom of 
the shaft 5 engages with a drive wheel 7 firmly fixed to a cylinder 8 and 
which, in rotation, rests on an annular support 9 fixed to the framework 
of the machine (which is not otherwise shown). The control shaft 5 is 
connected, at its lower end, to a motor shaft 11 by a known drive system 
12 which can comprise gear-wheels, pullies and belts, wheel and chain 
combination or the like. The motor 13 is located in one of the legs (not 
shown) of the framework of the machine. 
FIG. 2 is a schematic plan view of a device of the invention for driving 
and positioning the needle beds of a circular knitting machine. In this 
Figure is shown the symmetrical arrangement of three control devices 
relative to three planes (.pi..sub.1, .pi..sub.2, .pi..sub.3) which 
intersect along one and the same vertical line D, which is substantially 
on the machine axis. The motor 15 occupies a central position in the upper 
part of the knitting machine. It is fixed to a plate 16 which rests on 
three supports 17 which allow radial play for centering the motor and 
possess locking means 14 in order to secure the motor 15 in its operating 
position FIGS. 3 and 4. This motor drives three pullies 18 via belts 19 
which all three cooperate with the shaft of the motor 15. Tensioning 
devices 20 are provided. The pullies are symmetrically arranged about the 
three planes .pi..sub.1, .pi..sub.2, .pi..sub.3. 
FIG. 3 shows that each pulley 18 is connected to a respective vertical 
shaft 21 which at its ends carries pinion gears having sets of teeth 22, 
22', preferably machined into the material of the shaft. These sets of 
teeth, which are preferably machined simultaneously, are identical to 
about one-hundreth of a millimeter. The sets of teeth, 22, 22', 
respectively engage with intermediate gear-wheels 23, 23'. The six 
intermediate gear-wheels with which a machine is fitted are also 
preferably machined simultaneously so as to be as identical as possible. 
The three gear-wheels 23 engage with a drive wheel 24 of the dial whilst 
the three gear-wheels 23' engage with a set of teeth 25 machined at the 
bottom of the cylinder 26. This set of teeth 25 and the drive wheel 24 of 
the dial have the same basic diameter and the same number of teeth. The 
dial 27 is supported by members 40 extending sideways from three columns 
28 which form bearings for the three shafts 21. The cylinder 26 rests on 
three adjustable levers 29. 
Centering of the two needle beds is achieved by the six intermediate 
gear-wheels 23 and 23'. The fact that the six gear-wheels are identical 
and that the drive wheel 24 of the dial is identical with the set of teeth 
25 of the bottom of the cylinder permit strict centering. 
The three shaft 21 each carry an identical braking system 30. They all 
three participate in the control of the machine and all three equally 
experience shocks due to braking. However, these shocks, being distributed 
among the three shafts, are less intense in their action on each of the 
shafts than they would be on a single shaft and do not cause them to 
undergo deformation which can produce irregularities in the setting of the 
needles of the dial relative to the needles of the cylinder. 
Relative movement of the needle beds in the vertical direction in order to 
regulate the needle mesh spacing is effected at the three support points 
of the cylinder by adjustment of the levers 29. Control devices 31 (FIG. 
5) acting on the levers 29 make it possible to raise or lower the cylinder 
relative to the dial. A comparator such as micrometer 32 is connected to 
each lever 29 and engages a fixed part of the machine indicate the amount 
of travel at each of the three points. It is thus possible to produce 
strictly identical travels at each of the three points, which makes it 
possible to provide a needle bed spacing which is constant over the entire 
periphery of the machine. 
Any device for transmitting movement between the motor and the shafts 21 
could replace the belt and the pulley arrangements described above. Also, 
the sets of teeth machined into the material of the control shafts could 
be replaced by fitted gear-wheels, although this might not show such 
accurate centering of the needle beds. Further, alternative systems of 
support for the cylinder which allow vertical travel could be used, for 
example a clamp located towards the inside of the machine and adjustable 
by means of, for example, a screw. However, the device which has been 
described above has the advantage of freeing the bottom of the cylinder, 
making it possible to withdraw the latter easily and to replace the needle 
beds easily, for example in order to change the gauge of the machine. 
While three shafts and sets of gears have been described, a greater number 
could be used.