[0001] The present invention relates to knitting machines and, more particularly, to a method
of and an apparatus for controlling a knitting machine in accordance with a preset
pattern.
[0002] In knitting machines, various operating elements, such as knitting needles, sinkers
stitch cams and yarn feeders, are actuated by electrically driven needle selecting
devices. By way of example, a circular knitting machine conventionally includes a
rotating cylinder having vertical grooves in its outer periphery in which knitting
needles are slidably mounted for movement between knitting and non-knitting positions.
A plurality of needle selecting devices are disposed around the knitting cylinder,
typically one for each yarn feed, for selecting the knitting needles for movement
to knitting and non-knitting positions to accomplish a patterned knitting in accordance
with a preset pattern. These needle selecting devices are electrically connected with
a controller in which the preset pattern is stored for performing a patterning control.
[0003] Heretofore, such needle selecting devices are quite complex, as is the electrical
connection between such needle selecting devices and the controller, and maintenance
thereof is difficult and costly. A typical arrangement of needle selecting devices
and their controller is disclosed in JP-A-8-218255 and is illustrated in Figure 6
of this application. A plurality of needle selecting devices are connected in series
to each other and to their controller by means of a plurality of signal lines. Each
of the needle selecting devices has built therein, or is externally fitted with, a
respective drive circuit and includes a plurality of stages (for example, upper and
lower eight stages) of needle selecting fingers each having a piezoelectric element
operable to cause the needles to be selected in response to a pulse voltage applied
to such piezoelectric element.
[0004] The signal lines between the controller and the first needle selecting device and
between the needle selecting devices include a plurality of address data lines which
serve as paths of transmission of control data signals (knitting data signal) and
address signals, that are parallel signals outputted from the controller for controlling
the knitting operation, and a single strobe line which serves as a path of transmission
of a strobe signal outputted from the controller. The number of address data lines
is of a value sufficient to satisfy the number of bits of the knitting data and the
number of bits of addresses of each needle selecting device.
[0005] More specifically, an address signal for selecting one of the needle selecting devices
is transmitted from the controller to each needle selecting device through the address
data lines contained in the signal lines, and one of the needle selecting devices
assigned by such address signal is then specified at a timing in synchronism with
the strobe signal transmitted from the controller through the strobe line. In such
case, each needle selecting device is provided with a dip switch that is set to a
combination of On and Off positions in correspondence with the address assigned thereto
and, only when the address of the needle selecting device set by the dip switch matches
with the address signal thus transmitted, the above described address selection is
carried out. Thereafter, the knitting data signal associated with the above described
needle selecting device is transmitted from the controller to each needle selecting
device through the address data lines and is then stored in the address-selected needle
selecting device at a timing synchronized with the strobe signal transmitted from
the controller through the strobe line.
[0006] By sequentially carrying out the foregoing address selection and data writing operation
subject to each of the needle selecting devices, the needle selecting devices can
select the knitting needles necessary to accomplish the desired pattern knitting.
[0007] In such prior knitting machine control systems, the numerous address data lines for
transmission of the knitting data signals and the address signals and the single strobe
line utilized to electrically connect between the controller and the needle selecting
devices causes the control circuit and drive circuits to be bulky in size and complicated
in circuit design.
[0008] Also, because such conventional knitting machine control systems require that the
address of the needle selecting devices is necessarily repeated each time a data signal
is issued by the controller, excessive time is required to issue data signals to all
of the needle selecting devices, particularly where the number of such needle selecting
devices is large. For example, assuming that the number of the needle selecting devices
is expressed by N and the time required to drive a drive circuit of a needle selecting
device is expressed by t, then, the length of time expressed by N x t would be required
to cause all of the needle selecting devices to perform the needle selecting operation.
In other words, to activate a piezoelectric element, associated with the needle selecting
fingers in one of the needle selecting devices, by supplying a pulse voltage from
the associated drive circuit to such piezoelectric element would require a length
of voltage applying time of typically 16 ƒÊs and, therefore, in order for all of the
needle selecting devices to perform the needle selecting operation while the knitting
cylinder rotates an angle corresponding to a circumferential width of the single knitting
needle, at least the length of time expressed by N x 16 ƒÊs would be required. Accordingly,
if the number of the needle selecting devices is relatively large, it may occur that
the needle selecting operation would not be finished during the length of time in
which the knitting cylinder rotates the angle corresponding to the width of the single
knitting needle. In order to alleviate this problem, the length of time during which
the piezoelectric element is activated must be reduced from 16 ƒÊs down to 8 ƒÊs or
4 ƒÊs (µmm), but a different electrical countermeasure is necessitated to sustain
the reliability of operation.
[0009] In addition, such prior needle selecting devices tend to be complicated by the presence
of the dip switches required for address specification of such needle selecting device.
Moreover, in the event that replacement of the needle selecting device becomes necessary,
the dip switch of a replacement needle selecting device must be set to the combination
of On and Off positions which had been assigned to the dip switch of the replaced
needle selecting device, requiring a complicated maintenance.
[0010] With the foregoing in mind, it is an object of the present invention to alleviate
the above discussed problems and to provide a method of and an apparatus for controlling
a knitting machine which is simplified in structure and easy to maintain.
[0011] This object of the present invention is accomplished by providing a method of and
an apparatus for controlling a knitting machine in which control data is supplied
to a plurality of needle selecting devices, each of which includes a drive circuit
and a shift register. The shift registers in the needle selecting devices are connected
in series with each other and, therefore, the control data supplied from the controller
to the shift register of one of the needle selecting devices is sequentially transferred
to the remaining needle selecting devices. The control data is latched and retained
in each shift register when the transfer of the control data is completed, and the
drive circuit of the indicated needles selecting device is actuated based on the retained
control data.
[0012] Since according to this method and apparatus, the control data is outputted serially
from the controller and is sequentially transferred through the respective shift registers
in the remaining needle selecting devices and, when the transfer of the control data
corresponding to the respective shift register in each needle selecting device completes,
the control data is retained in the shift register, and the control data corresponding
to each needle selecting device can be transmitted with no need to specify the address
of any needle selecting device. Accordingly, the number of the signal lines necessary
for the data transmission can be reduced considerably, and hence the drive circuit
in each needle selecting device and the controller can be compacted, accompanied by
simplification of the associated circuit designs.
[0013] Also, since the number of the signal lines necessary for the data transmission is
thus reduced, making it possible to achieve a data transmission through a differential
line comprised of two lines through which the data signal and an inverted signal of
the data can be respectively transmitted simultaneously and, consequently, noises
containing a relatively large amount of high frequency components can advantageously
be suppressed considerably, it is possible to accomplish a high-speed data transmission
with the frequency of the data signal increased. For this reason, even though the
number of the needle selecting devices is increased, the length of time required for
all of the needle selecting devices to perform the needle selecting operation will
not increase significantly. Furthermore, this leads to the length of the voltage applying
time being reduced and a high reliability of operation can be maintained. In addition,
since all of the needle selecting devices can be actuated at the time the control
data are retained in those needle selecting devices, the present invention can be
applied not only to a piezoelectric control devices in which piezoelectric elements
are employed to drive the pattern fingers, but also to an electromagnetic control
device in which electromagnetic elements requiring a relatively long voltage applying
time are employed.
[0014] In addition, since the needle selecting devices need not be specified by respective
addresses, no dip switches are needed and in the event of replacement of one of the
needle selecting devices, no complicated and time-consuming job of setting a combination
of the On and Off positions to render the dip switch to match with the address is
necessary, rendering the maintenance to be easy to accomplish.
[0015] In order that the present invention may be more readily understood, reference will
now be made to the accompanying drawings, in which:-
Fig. 1 is a block diagram illustrating a preferred embodiment of the invention for
controlling a circular knitting machine;
Fig. 2 is a diagram illustrating a needle selecting device suitable for use with the
embodiment of Fig. 1;
Fig. 3 is a longitudinal sectional view showing one of the actuators employed in the
needle selecting device;
Fig. 4 is a chart showing waveforms of signals supplied from a controller of the needle
selecting device referred to above;
Fig. 5 is a schematic diagram showing the structure of the circular knitting machine;
and
Fig. 6 is a block diagram illustrating a conventional control system.
[0016] Referring now more particularly to the drawings and specifically to Figure 5, there
is illustrated schematically a circular knitting machine, generally indicated at 10,
including a rotating cylinder 11. Cylinder 11 has a multiplicity of vertical grooves
in its outer periphery (not shown) in which knitting needles 12 and other cooperating
operating elements are mounted. A more complete description of these conventional
knitting machine components is provided in US-A-5,647,230 owned by this proprietor.
Such operating elements include selector jacks 13 (Figure 3) positioned in the cylinder
grooves beneath the needles 12 for moving the needles 12 between knitting and non-knitting
positions in accordance with a preset pattern.
[0017] Knitting of fabric items, such as socks, is performed by the needles 12 which, in
cooperation with other stitch forming instrumentalities (not shown), knit yarns 14
(only one of which is shown) fed to the needles 12. Typically, a plurality of yarn
feeds, usually four to eight, are provided around the periphery of the cylinder 11.
[0018] Needle selection in accordance with the desired pattern is accomplished by a plurality
of needle selecting devices 20 arranged around the cylinder 11, with the number of
needle selecting devices
20 equaling the number of yarn feeds. The needle selecting devices
20 are positioned in advance of the yarn feeds for selecting the appropriate needles
12 to be moved to the knit position and thereby to receive yarn
14 from a yarn feed. Each needle selecting device
20 is the same and therefore only one will be described.
[0019] Needle selecting device
20 is preferably an electrically controlled and actuated device. More preferably, needle
selecting device
20 includes a plurality of actuating elements or piezoelectric elements
21 that are fixedly mounted at a medial location on a shaft
22 which in turn is rotatably mounted on a stay
23a of a housing
23. One end of each piezoelectric element
21 is received in a cavity in a block or stay
23b of housing
23 at one end thereof and the other end thereof moves up or down upon the application
of a pulse of electrical energy of either positive or negative polarity (Figures 2
and 3). Piezoelectric elements
21 are operatively connected at their other ends to pattern fingers
24 by a bifurcated end portion
24a. Fingers
24 are mounted for limited pivotal movement on a stay
23c of housing
23 and have their other end portions
24b projecting through openings in the housing
23. The piezoelectric elements
21 and pattern fingers
24 are preferably arranged in a multi-tier stack and may include eight tiers of stages
and each tier or stage may include two rows.
[0020] To actuate the piezoelectric elements
21, each needle selecting device
20 includes a drive circuit
25. Needle selecting device
20 also includes a shift register
26 for receiving, transferring and retaining knitting data which serves as control data
for the drive circuit
25.
[0021] A controller
30 is connected to one of the needle selecting devices
20 and the remaining needle selecting devices
20 are connected in series to the one needle selecting device
20. Controller
30 has a built-in data output means
31, a clock signal generating means
32 and a latch signal generating means
33. The knitting data for controlling and actuating the needle selecting devices
20 is outputted as serial signals from the data output means
31.
[0022] The data output means
31 is connected to the shift register
26 of the first in line needle selecting device
20 by a data transmission line
34a and the shift registers
26 of the remaining needle selecting devices
20 are connected together in series by data transmission lines
34b, 34c, etc. The clock signal generating means
32 is connected to the shift registers
26 of the needle selecting devices
20 by a data transmission line
35. Similarly, the latch signal generating means
33 is connected to the shift registers
26 of the needle selecting devices 20 by a data transmission line 36 and a power source
terminal 37 of controller 30 is connected to each needle selecting device 20 by a
power line 38 to complete the control circuits to the needle selecting devices 20.
[0023] The drive circuit 25 of each needle selecting device 20 is connected to the piezoelectric
elements 21. The piezoelectric elements 21 are generally of a rectangular plate-like
configuration and may be formed of a bimorph ceramic material or any other piezoelectric
material known to persons skilled in this art. When a positive or negative pulse voltage
is applied to the piezoelectric elements 21 by the drive circuit 25, they will flex
up or down and cause the pattern fingers 24 to pivot up or down as is illustrated
in Figure 3.
[0024] Each pattern finger 24 has a slant or sloping cam surface and a linear surface (not
shown) on its outer end of end portion 24b which engages a pattern butt 13a on the
selector jack 13 when the pattern finger 24 is pivoted upward by the application of
a positive pulse voltage to the piezoelectric element 21. The pattern finger 24 pushes
the selector jack 13 inwardly of cylinder 11 and out of the path of a raising cam
15. Therefore, the needle 12 will not be raised to the knit position, but will remain
in the non-knit or welt position. Conversely, when a negative pulse of voltage is
applied by the drive circuit 25 to the piezoelectric element 21, the pattern finger
24 will be pivoted downwardly and the outer end thereof will be moved out of the path
of the pattern butt 13 a of the selector jack 13 and the selector jack 13 will be
engaged and moved upwardly by the raising cam 15 to move the needle 12 to the knit
position to receive yarn 14 and thereafter form a stitch.
[0025] To place the present invention in perspective, Figure 6 illustrates a typical control
system, generally indicated at 50, for a previously used knitting machine (See JP-A-8-21855).
In this conventional control system 50, a controller 51 is connected in series to
a plurality of actuators or needle selecting devices 52, having drive circuits 53
therein, by a plurality of signal lines 54. The signal lines 54 include a plurality
of address lines which serve as paths of transmission of control data signals (knitting
data signals) and address signals, that are parallel signals outputted from the controller
51 for controlling the knitting operation, and a single strobe line which serves as
a path for transmission of a strobe signal outputted from the controller 51. The number
of address lines is of a value sufficient to satisfy the number of bits of the knitting
data and the number of bits of addresses of each actuator or needle selecting device
52.
[0026] In the above described needle selecting device, an address signal for selecting one
of the needle selecting devices
52 is transmitted from the controller
51 to each needle selecting device
52 through the address data lines contained in the signal lines
54, and one of the needle selecting devices
52 assigned by such address signal is then specified at a timing in synchronism with
the strobe signal transmitted from the controller
51 through the strobe line. In such case, each needle selecting device
52 is provided with a dip switch that is set to a combination of On and Off positions
in correspondence with the address assigned thereto and, only when the address of
the actuator set by the dip switch matches with the address signal thus transmitted,
the above described address selection is carried out. Thereafter, the knitting data
signal associated with the above described needle selecting device
52 at a timing synchronized with the strobe signal transmitted from the controller
51 through the strobe line.
[0027] By sequentially carrying out the foregoing address selection and data writing operation
subject to each of the needle selecting devices
52, the needle selecting devices
52 can select the knitting needles necessary to accomplish the desired pattern knitting.
[0028] In the needle selecting device of the structure described above, the numerous address
data lines for transmission of the knitting data signals and the address signals which
are the parallel signal and the single strobe line are utilized to electrically connect
between the controller
51 and one of the needle selecting devices
52 and between the neighboring needle selecting devices
52. For this reason, although the time required to transmit the knitting data signal
and the address signal to each of the actuators
52 may be reduced, a relatively large number of signal lines for the transmission of
the parallel signals, the signal lines
54 corresponding in number to the number of bits of the signals are required, hence
rendering the drive circuit
53 for each actuator
52 and the controller
51 to be bulky in size accompanied by complication of circuit designs.
[0029] Also, in the above described needle selecting device, the operation of specifying
the address of one of the needle selecting devices
52 and subsequently driving the drive circuit
53 after the data signal is retained in the needle selecting device
52 specified by such address is necessarily repeated each time the address of the needle
selecting device
52 is expressed by
N and the time required to drive one drive circuit
53 is expressed by
t, then, the length of time expressed by
N x
t would be required to cause all of the needle selecting devices
52 to perform the needle selecting operation. In other words, to activate the piezoelectric
element associated with the needle selecting fingers in one of the needle selecting
devices
52, by supplying a pulse voltage from the associated drive circuit
53 to such piezoelectric element,would require a length of voltage applying time of
typically
16 µs and, therefore, in order for all of the needle selecting devices
52 to perform the needle selecting operation while the knitting cylinder rotates an
angle corresponding to a circumferential width of the single knitting needle, at least
the length of time expressed by N x 16 µs would be required. Accordingly, if the number
of the actuators
52 is relatively large, it may occur that the needle selecting operation would not be
finished during the length of time in which the knitting cylinder rotates the angle
corresponding to the width of the single knitting needle. In order to alleviate this
problem, the length of time during which the piezoelectric element is activated must
be reduced from 16 µm down to 8µs or 4µs, but a different electrical countermeasure
is necessitated to sustain the reliability of operation.
[0030] In addition, in the above described needle selecting device, each of the needle selecting
devices
52 tends to be complicated in structure in the presence of the dip switch required for
address specification of such actuator
52. Moreover, in the event that replacement of the actuator
52 occurs as a result of failure of such actuator
52 to operate properly, the dip switch of a replacement actuator
52 must be set to the combination of On and Off positions which has been assumed by
the dip switch of the replaced needle selecting device
52, requiring a complicated maintenance.
[0031] The operation of the circular knitting machine
10 will now be described. At the outset, the knitting data
a corresponding to each of the needle selecting devices
20 is outputted from the data output means
31 of the controller
30 (Fig. 1) as a serial signal (as shown in Fig. 4). A single unit of the knitting data
a corresponding to one needle selecting device
20 comprises a signal having bits, the number of which is equal to the number of the
selector jacks
13, which is also the number of the piezoelectric elements
21. In the illustrated embodiment, there are
16 bits. The sequential arrangement of the knitting data
a is set to match with the sequential arrangement of the needle selecting devices
20. The serial signal representative of the knitting data
a so outputted is supplied to the shift register
26 in the first stage needle selecting device
20 (Fig. 1) and is then sequentially transferred to the shift register
26 in the last-stage needle selecting device
20 through the shift registers
26 in the intermediate stage needle selecting devices
20. The transfer of the knitting data
a is carried out bit by bit in synchronism with the clock signal
b (shown in Fig. 4) which is supplied parallel from the clock signal generating means
32 of the controller
30 to all of the shift registers
26.
[0032] When the transfer of the knitting data
a completes, the knitting data
a is latched in the shift registers
26 in response to the latch signal
c (shown in Fig. 4) which is outputted from the latch signal generating means
33 of the controller
30. In other words, in the case where the single unit of the knitting data
a for each of the needle selecting devices
20 is comprised of 16 bits, and assuming that the total number of the needle selecting
devices
20 is expressed by N, the latch signal
c is outputted each time the clock signals
b, (the number of which is equal to 16 x N) are outputted, so that the knitting data
a can be latched in each of the shift registers
26. Since as hereinabove described, the knitting data
a is supplied to the respective shift registers
26 of the needle selecting devices
20 and at the time of completion of the transfer of the knitting data
a, the corresponding knitting data
a is stored in the shift registers
26 in response to the above described latch signal
c.
[0033] The drive circuits
25 of the respective needle selecting devices
20 are activated in response to the latch signal
c which serves as a timing signal for initiating the pulse voltages that activate the
piezoelectric elements
21. In other words, the drive circuit
25 of the respective needle selecting device
20 is activated by the utilization of the knitting data
a, retained in the shift register
26 in such needle selecting device
20, as a control signal to thereby apply a positive or negative pulse voltage to the
piezoelectric element
21 to move the pattern finger
24 in the stage corresponding to the knitting data
a, allowing the corresponding pattern finger
24 to move upwards or downwards. By this action, as hereinbefore described, the knitting
needle
12 is shifted upwards or held standstill to thereby accomplish the desired pattern knitting.
[0034] A line through which the knitting data
a is transferred by means of the shift registers
26 is a differential line having a pair of two lines capable of transferring the data
signal and an inverted signal simultaneously and, therefore, any adverse influence
which would be brought about by noises can be suppressed to improve the S/N ratio
of the knitting data. In the case of the above described needle selecting device,
since without the needle selecting devices having to be specified by the respective
addresses as in the conventional case, the knitting data
a corresponding to the respective needle selecting device
20 can be supplied serially, the number of signal lines for the data transmission can
be reduced considerably. As a result thereof, an electric circuit for each needle
selecting device
20 and the controller
30 can be made compact with the circuit simplified in structure. In particular, the
use of the differential line comprised of a pair of two lines has hitherto been considered
impossible since the number of the signal lines may double, but has been made possible
in the present invention in which the number of the signal lines is reduced considerably.
[0035] Also, since the data transfer is possible with such a differential line, the noises
containing a relatively large amount of high frequency components can be suppressed
considerably and, therefore, it is possible to accomplish a high-speed data transfer
by increasing the frequency of the data signal a while any possible adverse influence
which would be brought about by the noises is avoided. For this reason, even though
the number of the needle selecting devices
20 is increased, the length of time required for all of the needle selecting devices
20 to perform the needle selecting operation will not increase significantly. In addition,
in view of this, no effort is necessary to reduce particularly the voltage applying
time for actuating the pattern fingers
24 in each of the needle selecting devices
20, securing a high reliability of operation.
[0036] Again, since at the time the knitting data
a is retained in all of the needle selecting devices
20, all can be actuated at a time, no effort is necessary to specifically reduce the
voltage applying time towards the pattern fingers
24 for accomplishment of a high speed operation and, therefore, the present invention
can be equally applied to an electromagnetic needle selecting device in which actuating
elements that require a relatively long voltage applying time are employed for actuating
the pattern fingers by the effect of an electromagnetic force developed by an electromagnetic
coil.
[0037] It is to be noted that in the control system of this invention, the length of time
required to transmit the knitting data
a to all of the needle selecting devices
20 would be 16 x N x T, wherein "N" represents the number of the needle selecting devices
20 used, "
16" represents the number of bits of the single unit of the knitting data
a and the "T" represents the cycle of the clock signal
b. However, if the clock signal
b has a cycle "T" which is 125 nanoseconds (a frequency of 8 MHz), the transmission
of the knitting data
a to all of the needle selecting devices
20 can be achieved stably and at a high speed and, during the period in which the knitting
cylinder
11 rotates the angle corresponding to the width of a single knitting needle
12, the needle selecting operation can be performed. By way of example, even where N
= 64, 16 x 64 x 125 nanoseconds = 128 microseconds and, hence, the length of time
required for the knitting cylinder
11 to rotate the angle corresponding to the width of one of the 3,000 knitting needles
12 is sufficiently smaller than 1 millisecond.
[0038] In addition, since the above described needle selecting devices
20 need not be specified by the corresponding address, no dip switch is required, as
in the conventional case, for each needle selecting device and the needle selecting
device
20 can be correspondingly simplified in structure. Also, even if as a result of one
of the needle selecting devices
20 failing to operate properly, replacement of the damaged needle selecting device
20 is required, no complicated and time-consuming job of setting a combination of the
On and Off positions to cause the new dip switch to match with the address is necessary,
rendering the maintenance easy to accomplish.
[0039] The present invention is not limited to the needle selecting device for selecting
the knitting needles of the type shown in the above described embodiment, but may
be applied to a control method and a control apparatus wherein electrically driven
needle selecting devices are used to drive various driven members in the knitting
machine such as a stitch cam for adjusting the knitting stitch of each knitting needle
and a yarn guide for changing the path of travel of a thread.