GB2058153A - Warp knitting machine - Google Patents

Abstract

A warp knitting machine, more particularly a stitch-bonding machine, has provision for keeping equal spacings between the knitting implements (sliding latch needles, closing wires, thread guides etc.) carried by respective bars 2, 3, 4, 5, 6 and 7, by compensating for the thermal expansion of the bars caused by different thermal influences. To this end electrical heating elements 14 to 19 and temperature measuring sensors 21, 23, 24, 26, 27 and 28 are provided in the respective bars which sensors form measuring bridges with respective desired value controllers. These control bridges are connected to the respective heating conductors via operational amplifiers, output stages and relays. <IMAGE>

Description

SPECIFICATION Method and means for keeping constant the spacings between the knitting implements in a warp knitting machine This invention relates to a method and means for keeping constant the spacings between the knitting implements in a warp knitting machine, in particular on a stitch-bonding machine. Different thermal influences, which vary in their intensity in the course of the stages of operation, namely prolonged stoppage, starting and continuous operation, cause different degrees of thermal expansion in the bars which carry the knitting implements (sliding batch needles, closing wires, thread guides etc.).These thermal influences can be caused, for example, by room temperature, by the mutual friction between the knitting implements and by the friction between the knitting implements and the textile material to be processed and, to a considerable degree, by the heat emitted by the gearbox of the machine or by the heat dissipated by adjacent components. The design is important in this case.

The varying degrees of thermal expansion in the individual bars carrying the stitch-forming knitting implements lead to variations in the spacing between the said implements. The precise cooperation of the implements is no longer ensured; faults, caused by breakages and bending of the knitting implements, occur in the working process, as well as reduction in quality. These problems are intensified as the fineness of material and the working width are increased.

Attempts have been made to obviate the errors in mutual spacing between the knitting implements by adjusting the knitting elements which are combined to form holders. This is effected in such a way that the implement holders of the bars subjected to lower thermal expansion are adapted to the implement holders of the bars subjected to higher thermal expansion to the required degree in each case.

As the operating time increases, the spacing errors change so that corrections are repeatedly necessitated. The adjustment of the holders becomes more costly as the working width is increased. It has become known practice (German Utility Model 1,896,204) to approximate the spacing by electrically heating the oil in the machine gearbox to operating temperature. As a result of the heat emitted by the compact gearbox, the bars located in its zone of influence, are heated in order to create in the bars the expansion corresponding to that during continuous operation, even during starting of the warp knitting machine.

This solution has the advantage that not all the bars in warp knitting machines are influenced to the same extent by heat emitted by the gearbox and therefore spacing errors cannot be excluded.

A further known solution (German Democratic Republic Patent Specification 115,515) relatesas do other inventions -- to the electrical heating of the bars. In this case it is assumed that there are "hot" and "cold" bars. In contrast to the "cold" bars, the bars which are located in the zone where they are directly influenced by the heat of the gearbox are referred to as "hot" bars. The mode of operation of this solution is that thermal energy is conveyed to the "cold" bars empirically to such an extent that the spacings are identical.

After a certain degree of saturation is reached, the temperatures of the "cold" and "hot" bars are automatically compared and the heating of the "cold" bar is adjusted.

This system of adjustment has proved unsuccessful in practice.

A considerable drawback is the classification of the bars as "cold" and "hot" bars, that is, the procedure of determining which bar is subsequently heated. It should be noted that the thread guide bar, which is classed with the "cold" bars, for example in stitch-bonding machines, can be hotter before starting than the needle bar which is designated as being "hot". This heating of the thread guide bar, for example, is caused by space heating, the bars which are designated as being "hot" being subject to the considerable thermal influence of the still cold gearbox during the prolonged stoppage and starting stages.

Depending on the type of machine and technology, the heating of the relevant bars by the gearbox can be further delayed by the insulating effect of the textile material to be processed. The mentioned known method does not take this fact into account since the greatest faults during starting after prolonged stoppages occur until a prolonged operating time is achieved.

It is the underlying object of the invention to provide a method and means which ensure an identical spacing between the respective knitting implements during all operating stages, that is, even at the beginning of the starting operation of the warp knitting machine, and which avoids faults caused by spacing errors and other disadvantages.

Accordingly, the present invention consists in a method of keeping constant the spacings between the knitting implements in a warp knitting machine which are carried by the respective bars, in particular in a stitch-bonding machine, to compensate for the thermal expansion and associated spacing errors in the respective operating states, normally caused by different thermal influences, characterised in that if necessary all the bars are heated, the guiding during control being initiated in each operating stage by the bars which during continuous operation are exposed to the thermal effect of the machine gearbox.

The present invention also consists in a warp knitting machine, in particular a stitch-bonding machine, having means for keeping constant the spacings between the knitting implements which are carried by respective bars, characterised in that all the bars are preferably provided with electric heating elements, the power input of which is determined to the required degree.

It is now possible for each of the bars, which are subject to the thermal influence of the gearbox, to be electrically heated by a suitable circuit so that their temperature is definitely several degrees higher than the temperature if the bar which is hottest when in the cold state and which is unaffected by the heat of the gearbox.

The other bars are subsequently guided to the same extent by the heating of the heated bars. At first this heating proceeds until the implements of all the bars have equal spacing which is achieved by a single adjustment of the heating system and until the temperature thereof is higher than the temperature of the hottest bar when in the cold state. The bars which are subject to the thermal influence of the gearbox are heated as the operating time increases so that the command variable of the control system is the spacing or the electrical resistance of the bars which are uniformly heated by the gearbox.

Advantageous embodiments of the invention are described in the subsidiary claims.

In developing the present method, it is ensured that the machine cannot under any circumstances be put into operation until the errors in spacing between the knitting implements have been reduced to a degree which is acceptable and does not disrupt the working process.

In order that the invention may be more readily understood, reference is made to the accompanying drawings which illustrate diagrammatically and by way of example embodiments thereof, and in which: Figure 1 shows a cross-section through the stitch-forming station of a stitch-bonding machine for the consolidation of fleece by means of stitching thread, Figure 2 shows a plan view of a sliding latch needle bar, Figure 3 shows a plan view of a stitching thread guide bar, Figure 4 shows a circuit diagram of the control unit for heating the needle bar, closing wire bar and knocking over bit bar, Figure 5 shows a table corresponding to Figure 4, Figure 6 shows a circuit diagram of the control unit having a follow-up control for heating the thread guide bars and the counter holding bar, and Figure 7 shows a table corresponding to Figure 6.

The stitch-forming knitting implements according to Figure 1 for the consolidation of fleece by bonding with a stitching thread are needles or plates which are combined to form holders. The latter are sliding latch holders 8, closing wire holders 9, knocking over bit holders 10, thread guide holders 11 on the left (Fig. 3), thread guide holders 12 on the right, and the counter holding plate holders 13, which are screwed on the respective bars extending over the working width of the machine. The corresponding bars are called the sliding latch needle bar 2, closing wire bar 3, knocking over bit bar 4, thread guide bar 5, on the left, for receiving the thread guide holders, 11, on the left, and thread guide bar 6, on the right, for receiving the thread guide holders, 12, on the right, and the counter holding plate bar 7.The thread guide bar 5, 6 has been divided because of uneven thermal expansion, so that the thread guide bar 5, 6 could be designed in two separate control sections.

The gearbox 1 of the machine has a virtually equal thermal effect on the needle bar 2, the closing wire bar 3 and the knocking over bit bar 4.

The room temperature has virtually no influence on these bars because of the more or less insulating effect of the cover plate 32, of the fleece 33 with preset stitch-forming points or of the stitch-bonded fabric 34 produced. The thread guide bars 5, 6 and the counter holding plate bar 7 are heated only indirectly by the gearbox 1. As a result of friction between the sliding latch needles 8 and the fleece 33 or between the thread guides 11, 12 and the thread, between the needles 8 and closing wires 9, due to contact between the fleece 33 and the counter holding plates 13 and the knocking over bits 10, and between the stitchbonded fabric 34 and the knocking-over bit holder 10 and the fabric support bar 31, heating of or dissipation of heat on the dividing sinkers occurs.

The ambient temperature is important to the heat content of the thread guide bars 5, 6, the counter holding bar 7, the fabric support bar 31, the fleece 33 and the sewn/knit fabric 34.

This complexity of influences, which vary in their intensity and direction of effect as the operation time increases, and the thermal expansion caused thereby in the respective holders and bars means that heating of the bars is required to the necessary degree. An automatic heating control system is provided for adapting to the actual prevailing conditions or for keeping the said conditions constant.

The needle bar 2, the closing wire bar 3, the thread guide bar, on the left at 5, the sewing thread guide bar, on the right at 6, and the counter holding bar 7 are respectively heated by the heating conductors 14, 1 5, 1 7, 1 8, 1 9 which lie in grooves formed in the various bars. The knocking over bit bar 4 is heated by the heating conductor 1 6 which is externally adjacent thereto. This eliminates the accumulated cold, prevailing before work commences in the space which is bounded to a greater or lesser extent by the gearbox 1, the cover plate 32, the fleece 33 and the fabric 34.

The measuring sensors, which are necessary for controlling the movable bars are constructed as contactless measuring sensors 20, 21,22, and 23. If this requirement cannot be met, as in this embodiment in which the measuring sensors 26, 27 are attached to the thread guide bars 5, 6 by holders 30, it should be ensured that substantially immovable feed lines are installed. In cases where for design reasons the measuring sensors cannot be fully accommodated by the bars, the metal enclosure of the measuring sensor is enlarged, for example by means of an extension 29 on the needle bar 2.

The control unit is set once before being put into operation in order to achieve the intended effect. The desired value controller 59 is set so that the heating conductor 14 heats the needle bar 2 to a temperature several degrees higher than that of the hottest bar or rail in the cold state.

Then, the heating conductor 1 5 of the closing wire bar 3 is set by the desired value controller 60. The heating conductor 1 6 of the knocking over bit bar is set by the desired value controller 61. The desired value controllers 59, 60, 61 are set with the object of creating equal spacing between the knitting implements in the needle holder 8, closing wire holder 9 and knocking over bit holder 10.

The control measuring sensors 21, 23, 24 and the desired value controllers 59, 60, 61 each form part of the measuring bridges 35, 39, 43 and are connected to the difference input of the operational amplifiers 36, 40, 44.

If the temperature in the bars is still below the desired value, the measuring bridges 35, 39, 43 are unbalanced. The relays 38, 42, and 46, which switch on the heating conductors 14, 1 5, 1 6, are controlled via the operational amplifiers 36, 40, 44 and the output stages 37, 41, 45. When the desired temperature is reached, a balance is established in the measuring bridges 35, 39, 43.

The heating conductors 14, 1 5, 1 6 are switched off via the operational amplifiers 36, 40, 44, the output stages 37, 41, 45 and the relays 38, 42, 46.

The heating conductor 1 7 of the thread guide bar, on the left at 5, is set by the desired value controller 62 so that the spacing between the thread guide holders, on the left at 11, corresponds to the spacing between the needle holders 8 on the left hand side of the needle bar 2.

The control measuring sensor 26 is mounted in the thread guide bar, on the left at 5. A follow-up measuring sensor 20 is installed in the left hand side of the needle bar 2. The control measuring sensor 26 and the follow-up measuring sensor 20 form part of the measuring bridge 47 which is automatically maintained in a balanced state. If the temperature in the needle bar 2 increases as a result of the heating by the heating conductor 14 or by the heat emitted by the gearbox 1, the measuring bridge 47 is unbalanced. The operational amplifier 48 controls the relay 50 via the output stage 49. The heating conductor 1 7 of the thread guide bar, on the left at 5, is switched on.

When a temperature at which the spacing between the thread holders, on the left at 11, corresponds to the spacing between the needle holders on the left hand side, is reached with the aid of the control measuring sensor 26 in the sewing thread guide bar, on the left at 5, a balance is established in the measuring bridge 47. The operational amplifier 48 switches off the heating conductor 1 7 via the output stage 49 and the relay 50.

The thread guide bar, on the right at 6, is controlled in a similar manner. Correspondingly, the required temperature of the counter holding bar 7 is adjusted to the temperature of the knocking over bit bar 4.

The coordination of the respective elements of the control unit with the associated bars is shown in Figures 5 and 7. The output stages 37, 41, 45, 49, 53, 57 and the relays 38, 42, 46, 50, 54, 58 can be replaced by Triac zero-voltage controllers.

The relays 38, 42, 46, 50, 54, 58 control the release/protective circuit for the starting of the stitch-bonding machine. The said protective circuit consists of relays having self-holding contacts and working contacts. The working contacts are connected in series and are located in the control current circuit of the stitch-bonding machine.

Claims (9)

1. Method of keeping constant the spacings between the knitting implements in a warp knitting machine which are carried by respective bars, in particular in a stitch-bonding machine, to compensate for the thermal expansion and associated spacing errors in the respective operating states, normally caused by difference thermal influences, characterised in that if necessary all the bars are heated, the guiding during control being initiated in each operating stage by the bars which during continuous operation are exposed to the thermal effect of the machine gearbox.

2. Method according to Claim 1, wherein, until the heat of the gearbox takes effect, the bars located in the zone of the gearbox are heated to a predetermined level, followed at the same time by the bars located outside the zone of the gearbox.

3. Method according to Claim 2, wherein the temperature of the bars, heated to a predetermined level and those following, is several degrees higher than the temperature of the bar which is the hottest when in a cold state and is not directly affected by the heat of the gearbox.

4. Method according to Claim 2 or 3, wherein the warp knitting machine can only be put into operation after the predetermined level of temperature has been reached.

5. A warp knitting machine, in particular a stitch-bonding machine, having means for keeping constant the spacings between the knitting implements which are carried by respective bars, characterised in that all the bars are preferably provided with electric heating elements, the power input of which is determined to the required degree.

6. A warp knitting machine according to Claim 5, wherein there are provided a measuring bridge, an operational amplifier, an output stage and a relay which switch on or off the heating system of the needle bar, the closing wire bar and the knocking over bit bar.

7. A warp knitting machine according to Claim 5 or 6, wherein there are provided a further measuring bridge, an operational amplifier, an output stage and a relay which cause the thread guide bars and the counter holding bar to follow on relative to the needle bar and the knocking over bit bar.

8. A warp knitting machine according to any of Claims 5 to 7, wherein the heating of one or a plurality of said bars can be divided into separate control sections, when the thermal conditions created inside said bars by constant influences are not generally constant.

9. A warp knitting machine, in particular a stitch-bonding machine, substantially as herein described with reference to and as shown in the accompanying drawings.