Warp knitting machine with electrically controlled thread feed

A warp knitting machine comprises a brake operative upon current interruption. The guide bars are displaced by an electrical setting motor as well as a control arrangement, which establishes the position of the guide bars in dependence upon the angular position of the main shaft. The control arrangement bases its control upon a predetermined displacement function relating the positions of the main shaft and guide bar. The setting motor and control arrangement are connected to a main power source via an intermediate circuit, which has at least one storage condenser. This machine allows for a rather rapid change of the lapping pattern and a continuance of controlled guide bar displacement right up to the standstill of the main shaft.

BACKGROUND OF THE INVENTION 
1. Field Of the Invention 
The present invention relates warp knitting machines having (a) a main 
shaft driven by an electrical main motor, (b) an electrically operated 
brake activated upon current interruption, and (c) at least one 
supplemental electrical system connected to the main power circuit, for 
influencing the thread feed. 
2. Description Of Related Art 
When a warp knitting machine of the foregoing type (DE PS 30 25 792) is 
switched, the supplemental control system is separated from the power 
mains by a time delay relay, so that the supplemental system operates 
until the actual standstill of the main shaft. However, if power mains 
fail both the main shaft motor as well as the supplemental system lose 
power. While inertia causes the main shaft to runs on, immediate 
inoperability befalls the supplemental system, that is, the controlling 
motor for the warp beam drive speed and a jacquard arrangement. The main 
shaft is not considered a substantial problem since the brake on the main 
shaft operates quite rapidly, that is, within one or two revolutions. The 
thus resulting pattern errors are not observable to the naked eye. 
Generally speaking, guide bars are mechanically connected to the main 
shaft, suitably by means of a cam plate system or pattern chains. Thus, 
after the run down of the main shaft, the correct correspondence between 
the guides and the remaining operating elements remains. It is however, 
burdensome to alter such displacement patterns since this requires an 
exchange of cam plates or pattern chains. It is thus either impossible or 
rather difficult to provide a displacement pattern with a longer repeat. 
A control arrangement for the displacement of guide bars in warp knitting 
machines is known (DE OS 22 57 224), in which the displacement steps to be 
taken are read off from a schedule carrier, for example a punched or 
magnetic tape. A synchronizing transmitter generates a signal in 
particular angular positions of the main shaft, based on which, the most 
recently read displacement step is carried out by means of a position 
control circuit. By using another schedule carrier, it is possible to 
change the pattern by changing the displacement motion. The progress of 
the displacement motion cannot be controlled since it depends upon the 
design of the control circuit. 
Accordingly, there is a need for a warp knitting machine of the 
above-mentioned type in which the displacement pattern for the guide bars 
may be altered in a simple and procedurally safe manner. 
SUMMARY OF THE INVENTION 
In accordance with the illustrative embodiments demonstrating features and 
advantages of the present invention, there is provided a warp knitting 
machine adapted to be connected to a main power source. The machine has at 
least one guide bar, a main shaft, and an electrical main motor coupled to 
the main shaft for driving it. A brake coupled to the main shaft can brake 
it upon interruption of current to the electrical main motor. Included is 
at least one supplemental system for influencing delivery of threads. This 
supplemental system is commonly powered with the main motor by the main 
power source. The supplemental system has a control arrangement, an 
intermediate circuit, and at least one electrical setting motor for 
displacing the guide bar. The control arrangement is coupled to the main 
shaft and the setting motor. This control arrangement is responsive to the 
angular position of the main shaft for positioning the guide bar, as 
determined by a predetermined displacement function correlating positions 
of the guide and the main shaft. The intermediate circuit has an energy 
storage device for replacing interrupted power from the main power source 
to keep the setting motor and the control arrangement powered at least 
temporarily. 
The preferred supplemental system has an electrical setting motor for 
displacing the guide bar. The preferred control arrangement sets the 
position of the guide bars in dependence upon the angular position of the 
main shaft, using a predetermined displacement function. This preferred 
control arrangement is connected to the power mains via at least one 
storage condenser. 
In such a construction, the guide bar displacement depends up on the 
displacement function generated by the control arrangement. This can be 
readily altered and permits larger repeats without any difficulty. The 
displacement function is a continual function which, for every angular 
position of the main shaft, specifies a particular position of the guide 
bar. In normal operation therefore, the relative correspondence between 
the guides and the remaining elements of the machine are exactly defined. 
Difficulties arise however, when a power interruption occurs in the power 
mains, since the control arrangement and the setting motor are no longer 
operative. Thus collisions between the operating elements cannot be 
avoided. However, by utilizing a power restoring condenser, the time up to 
the standstill of the main shaft can be bridged. Since the main shaft is 
braked and therefore the electrical power need only be available for a 
short time, the cost and space requirement for a storage condenser is not 
too great. The provision of the storage condenser in an intermediate 
circuit has the advantage that it is constantly charged fully and 
therefore unloading can commence at a predetermined voltage. 
Preferably, when there is a plurality of guide bars with appropriate 
setting motors, the intermediate, power-restoring circuit is common to all 
the motors. This permits the total capacity of the storage condenser, that 
is to say, the storage condensers switched in parallel, to be smaller, 
since the peak demand of the storage motors generally speaking does not 
occur at the same time and therefore an energy exchange is possible. 
Preferably, the main shaft motor and the setting motor are driven with 
alternating or cyclic current and the storage condenser in the 
intermediate circuit is located between a rectifier and an inverter. In 
such an arrangement the control condenser is safely charged even though in 
the rest of the circuit, the current is an alternating or cyclic current. 
Furthermore, this makes it simple to drive the setting motor with another 
frequency, suitably lower than that at the main shaft motor. Such 
adaptable frequency is of interest, with respect to the design and control 
of the setting motor. 
Preferably, the setting motor is an electrical linear motor. This enables 
the guide bars to be controlled with greater accuracy. 
In a preferred embodiment the control arrangement comprises: an absolute 
bar position transmitter, an absolute rotational angle transmitter for the 
main shaft, a schedule transmitter, and a position control circuit. The 
absolute bar position transmitter provides a different position signal for 
each position of the guide bar, that is, the setting motor. The absolute 
rotational angle transmitter provides a different rotational angle signal 
value for every position of angular rotation of the main shaft. The 
schedule transmitter receives different displacement functions to generate 
the appropriate position reference value, in dependence upon the 
rotational angle signal of the chosen displacement function. The position 
control circuit compares the bar position signal with a position target 
value and controls the setting motor in dependence upon the deviation from 
the desired value. 
The use of an absolute rotational angle generator ensures a clear 
relationship between the bar's position target value and the rotational 
angle setting of the main shaft at every point in time. The absolute bar 
position transmitter ensures that a position signal is clearly assigned to 
each position target value. In summary, there is thus obtained an 
unequivocal relationship between a rotational angle setting and position. 
This relationship may be readily altered by the provision of a different 
displacement function.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to FIG. 1, guide bar 1, which is to be displaced, is connected 
via a connecting rod 3 to the setting motor 2, here in the form of an 
electrical linear motor. An absolute position transmitter 4 generates 
position signal X.sub.i which runs via line 5 to position controller 6. 
Transmitter 4 may be an encoder for producing a digitally encoded signal 
indicating displacement of bar 1. 
The main shaft 7 of the warp knitting machine is driven by electrical motor 
8. An rotational absolute angle generator 9 sends to the output 
arrangement 11 over line 10, a rotational angle signal, which corresponds 
to the appropriate position of the main shaft 7. Generator 9 may be a 
shaft encoder for sending a digitally encoded signal corresponding to 
shaft rotation. Arrangement 11, in dependence upon the rotational angle 
signal on line 10, transmits position target value X. to the position 
controller 6. In dependence upon the deviation from the desired path, the 
setting motor 2 is provided with the appropriate control signal S. 
Furthermore, the main shaft 7 is provided with a brake 12 which is caused 
to operate when the current fails, by means of a power storage means, for 
example a loaded spring (not shown). When current is applied a solenoid 
(not shown) can overcome the spring and allow shaft rotation. 
A schedule transmitter 13 comprises a storage means 14 and a computer 15. 
Storage means 14 can be an EPROM or other type of digital memory. A 
plurality of prototype transition curves F for the overlap and the 
underlap displacements are stored in storage means 14. The desired 
transition curves for the desired lapping patterns can be identified and 
summoned by means of characteristic value K1. 
Characteristic value K2 presents a calculation formula to computer 15 which 
operates in conjunction with the specified transition curves F. The 
formula instructions comprise, inter alia, the sign specification 
(positive/negative) and an integer multiplier. From these instructions, 
computer 15 assembles transition curves F in sequence, and optionally 
rescales and/or inverts them to produce the displacement function V. This 
in turn allows output arrangement 11 to generate the appropriate position 
target value X.sub.s as a function of the rotational angle signal on line 
10. 
In this way, there is a clear correspondence between the angular position 
of main shaft 7 and the appropriate position of guide bar 1. The guide bar 
is so positioned by the position controller 6 that it can run through its 
entire working cycle without the occurrence of collisions. For example, 
the control value S can be produced as a linear or other function of the 
difference between signals X.sub.i and X.sub.s. 
In practice, blocks 6, 11 and 15 as well as the storage means 14 need not 
be separate segments. In fact, they can suitably be put together in a 
central processing unit Z in the manner of a process computer. This 
processor can be programmed with interrupt handlers that respond to 
increments in signals on lines 5 and 10. When signal X.sub.i changes, 
signal X.sub.s is adjusted based on the feedback function in arrangement 6 
(e.g., a linear or integral function of (X.sub.i -x.sub.s)). When the 
signal on line 10 changes signal X. is adjusted (e.g. by a look-up table 
formed in accordance with function F). 
The CPU Z, together with the absolute position transmitter 4 and the 
absolute rotational angle position transmitter 9, form the control 
arrangement 16 for the displacement of guide bar 1. 
FIG. 2 illustrates that the main shaft 8 is connected to an alternating 
current source 20 via dual pole switch 17 having contacts 18 and 19. A 
brake 12 is connected across the switched side of switch 17 in parallel 
with previously illustrated, main shaft motor 8, so that upon power 
failure, (for example main power interruption from source 20), brake 12 is 
activated and the main shaft is brought to a standstill, suitably in a few 
seconds. 
A rectifier 21 is powered through the same switch 17 by alternating current 
power source 20. An intermediate circuit 22 having an energy storage 
device (condenser 23) is connected to the output of rectifier 21. 
Rectifier 21 may be a full or half wave bridge using in one embodiment a 
transformer feeding a rectifier bridge to charge condenser 23 (transformer 
and bridge not shown). 
Connected to circuit 22 is an inverter 24, which is powered by condenser 23 
to, in turn, power setting motor 2. Inverter 24 produces an alternating 
current to motor 2. Control arrangement 16 is also connected across 
condenser 23. Arrangement 16 and motor 2 respond to previously mentioned 
control signal S. In case it is necessary to power a second setting motor 
2a for another guide bar, a further inverter 24a is connected to 
intermediate circuit 22. Additionally, intermediate circuit 22 is provided 
with additional condenser 23a; or a larger condenser 23 is provided. Where 
control arrangement 16 is driven by DC current, it may be directly 
connected to the intermediate circuit. 
The capacity of intermediate circuit 22 is so chosen that control 
arrangement 16 and setting motor 22 can unequivocally be operated up to 
the time of complete standstill of the main shaft. One must take into 
account the fact that only a partial discharge of the storage condenser 23 
is permissible since otherwise the condenser size is inadequate for 
driving the control arrangement 16 and the setting motor 2. Generally 
speaking, a 50% discharge is permissible. 
FIG. 3 illustrates individual transition curves F1 for the overlap and F2 
for the underlap as they are stored in storage means 14. The computer 15 
can assemble them in sequence to provide the displacement function V, 
which is illustrated in FIG. 4. In this simple case, the computation 
operation defined by characteristic K2 involves inverting the control 
curve F2 in the computation. The transition curves are clearly shown 
providing a displacement of one needle space. For displacements over a 
plurality of needle spaces, one may utilize the same transition curves, 
however in such a case computer 15 must multiply the displacement values 
by an integer defined by characteristic K2. 
The transition curves herein are illustrated as straight lines. In practice 
however, the curves are rather specialized curves, which are similar to a 
sinusoidal, parabolic or hyperbolic format or are comprised of a plurality 
of collected segments. The purpose is to keep the accelerations and 
decelerations of the guide bar 1 to an absolute minimum. The displacement 
functions can also take into account other displacement errors such as 
those caused by the utilization of a linked push rod in the guide bar 
drive or by a needle/guide deflection due to the tension of the threads. 
In the illustrated example, brake 12 is operated not only when a power 
failure occurs in the main source 20, but also when switch 17 is opened. 
If it is undesirable for the brake to operate in such a case, the brake 
can be connected before switch 17 so that the switched off main motor 8 
still continues to run. In this case, the capacity of the storage means in 
the intermediate circuit 22 is insufficient unless power be removed from 
the main circuit by a timed delay as is the case in other systems, such as 
are described in DE PS 30 25 782. 
Instead of alternating current, it is also possible to utilize a 
multi-phase or other pulsing or cyclic current source.