EP0860529B1 - Control module for controlling the needles of a knitting machine - Google Patents

Abstract

A controller has a piezoelectric bending transducer (2). The transducer has a flat support (3), which has a piezoelectrically active sheet (4) on one side and is fixed to a housing (1) at one end (5). The ratio of its free length (30) to its thickness (31) is 40-70.

Description

The invention relates to a control module for controlling the needles a knitting or knitting machine with a housing and at least one piezoelectric bending transducer arranged therein, wherein the bending transducer comprises a flat support body, which is at least on one side with a piezoelectric active layer and at a rear end is firmly connected to the housing.

Such a control module is suitable for controlling the needles or stitch-forming elements of a textile machine, such as a knitting or knitting machine. This is particularly suitable Control module for use on a jacquard machine. to Pattern formation in the goods produced by a textile machine becomes the information whether a needle is forming a stitch is used or not, via a mechanical Obtained scan of the deflection of the bending transducer. Dependent a mesh is formed from the deflection of the bending transducer or not.

For this purpose, a control module is known from US 3,961,501 A, at which the movable end or front end of the piezoelectric Bending converter with a guide part through which is assigned a for the elevation of each needle Part of a knitting machine depending on the passing from the deflection of the bending transducer to an operative position is pressed or not. In the operative position is the stroke of a corresponding cam with the help of the uplifted part, for which also the technical term Circuit board is used on the appropriate needle transfer. In this way, every single needle of the Knitting machine can be controlled separately. Unfortunately, however, the positioning speed of known bending transducers is sufficient not out of a theoretically possible knitting speed to reach. From US 3,961,501 it is further known a number of bending transducers in parallel in the control module to each other and at predetermined intervals from each other to arrange. The corresponding number of needles or sinkers will correspond to the position of the respective bending transducer Place a cam or finger, which when swiping past with the guide part of the corresponding Bending transducer comes into contact. In this way can the pattern information for a predetermined number of needles to the control module in a single switching operation transfer. It is common here to have 8 or 16 bending transducers for controlling 8 or 16 needles in the control module summarize. The working speed of the knitting machine can be increased.

The control module described in US 3,961,501 A is in similarly also known from EP 0 210 790 A2. Also here a number of bending transducers are combined in the control module, to control the working speed of the Increase textile machine.

Such a control module is also from DE 39 33 149 C2 known. Here, the bending transducer is at a rear end movably connected to the housing and additionally on one Center area rotatably supported. Through this between the ends of the bending transducer lying area is a reduction the response time of the bending transducer. On however, such a bending transducer must have a certain minimum length exhibit. Such a bending transducer must also be possible be wide and less than Have 200 microns. This is the only way to get one Achieve high electrical capacity of the bending transducer, so that with a normal operating voltage of approx. 50 V one can achieve sufficiently high deflection of the bending transducer. As is known, it is the one introduced into a bending transducer electrical energy proportional to its electrical Capacity and proportional to the square of the applied Voltage or potential difference. The capacity of the bending transducer itself is proportional to the area of the applied piezoelectrically active layer and inversely proportional to the thickness of the bending transducer.

Due to the size of such a bending transducer the housing of the control module must have a corresponding Have length, resulting in a control module with large dimensions leads. Furthermore, can be stored with such Bending converter only positioning or response times of no less than 2.5 milliseconds (msec.). The Working speed one with such a control module Equipped textile machine is still by the response time of the bending transducer limited.

The object of the invention is to provide a control module based Specify piezoelectric bending transducer, which is a superior Has property in terms of response time.

According to the invention, this object is achieved by a control module to control the needles of a knitting or knitting machine, with a housing and at least one arranged therein piezoelectric bending transducer, the bending transducer one includes flat support body, which at least on one side provided with a piezoelectrically active layer and on its rear end is fixed to the housing, wherein the ratio of the free length of the bending transducer to its Thickness ranges from 40 to 70. Under The free length of the bending transducer becomes the distance between the front, freely movable end and the location of the fixed connection to the housing at the rear end of the bending transducer Roger that.

The invention does not take the path according to the opinion a relevant expert a bending transducer with high electrical capacity and resulting proportionately great length and width for a control module with high Response time to use. Rather, the invention proceeds from considering that the response time of a bending transducer largely determined by its mechanical vibration behavior becomes. Here again is the natural or resonant frequency of the bending transducer a significant factor. The higher the resonant frequency is, the easier a low one can be Response time can be achieved. Do extensive research show that with a bending transducer, in which the Ratio of its free length to its thickness in an area is between 40 and 70, resonance frequencies of more than 150 Hz. Bending transducers common until now however, have a ratio of length to thickness in one Range from 100 to 140, which results in resonance frequencies of not more than 100 Hz.

With a bending transducer with the specified ratio of length and thickness, response times of less than 2.5 msec can be based on the resonance frequency. achieve. Such response times are required, for example, to control the needles of a circular knitting machine in accordance with the maximum possible rotation speed of the knitting cylinder. With a control module on the basis of such bending transducers, a productivity increase of a knitting machine, ie knitted goods in m ² per unit time, can be achieved by approximately 50% compared to control modules which are equipped with conventional bending transducers. Conventional bending transducers only achieve response times of not less than 2.5 msec.

It is advantageous if the bending transducer is used to control the needles by applying a voltage or a potential difference of more than 100 V to the electrodes of the piezoelectric active layer, for example electrodes in the form of a Metallization, is actuated. This way even with a relatively short and thick bending transducer with a accordingly low electrical capacity which for a mechanical deflection required electrical energy contribute. The electrical inserted in a bending transducer As already mentioned, energy is proportional to the square of the applied potential difference or voltage. Such a short bending transducer leads to one small housing dimensions of the control module.

To be as homogeneous as possible when applying the potential difference electric field in the piezoelectrically active layer Achieving along the bending transducer can be piezoelectric active layer with flat, electrically conductive Electrodes are provided. In particular, the support body be electrically conductive and as such an electrode Act. A flat electrode can have one, for example the piezoelectrically active layer applied metallization or a coating made of a conductive plastic his. The application of the potential difference or voltage can via connecting cables contacted with the corresponding electrodes happen.

In principle for the piezoelectrically active layer all materials are suitable, which the piezoelectric or show the electrostrictive effect, it's special advantageous if the piezoelectrically active layer Piezoceramic is. Such a piezoceramic allows namely through their composition an adaptation to different Requirements, for example with regard to the coefficient of thermal expansion, the size of the piezoelectric effect or in terms of flexibility become. In particular, certain oxide ceramics, e.g. on the base of lead zirconate titanium known, which excellent Have properties.

So that such a ceramic or piezoceramic the piezoelectric Effect shows is a polarization of the same in one homogeneous electric field of a few KV / mm required. In this way, a polar axis in the piezoceramic generated for the occurrence of the piezoelectric effect necessary is. Through the polar axis, which in the direction of the shows the electric field used for polarization defines the so-called polarization direction of the piezoceramic.

Becomes a piezoceramic against its polarization direction operated, i.e. an electric field becomes antiparallel to the If the direction of polarization is applied, this leads to depolarization and ultimately a disappearance of the piezoelectric Effect. It is therefore common to use conventional bending transducers, which are provided with a piezoceramic, with Operating voltages of no more than 50 V in order to depolarization when operating against the direction of polarization to keep as low as possible. Conveniently, is therefore when operating with a potential difference of more than 100 V this applied to the piezoceramic such that the emerging electric field in the direction of polarization Piezoceramic shows.

An increase in the deflection path of the bending transducer can be achieve if the bending transducer with a piezoelectrically active layer is provided. From the rest position of the bending transducer can be alternately Apply a potential difference to both piezoelectrically active ones Layers achieve a deflection on both sides and thus the deflection path compared to a one-sided coating Double the bending transducer.

For one coated on both sides with a piezoceramic Bending converter can be used to control the needles of the bending converter by applying a potential difference of more than 100 V. one of the piezoceramic layers is actuated, the electric field in the direction of polarization of the respective piezoceramic layer shows and each potential difference present at the other piezoceramic layer is zero. You can do this between the two outer ones Electrodes of the bending transducer a fixed predetermined potential difference be created and the supporting body or possibly itself between the support body and the respective piezoceramic Alternating internal electrodes switched to the respective potential of the outer electrodes become.

The thickness of the bending transducer is advantageously in one Range from 500 to 900 µm. With such a thickness with a sufficiently high electrical capacity high mechanical resonance frequency and thus a low response time of the bending transducer. The free length of a such bending transducer can be reduced to 25 mm.

For the width of the bending transducer, it is advantageous if this is in a range of 2 to 10 mm.

A high flexibility and a high response time of the bending transducer can be achieved if the support body from a Fiber composite material exists. Such a fiber composite is, for example, a carbon or glass fiber reinforced Epoxy resin, depending on whether it is an electrically conductive or an electrically non-conductive support body is desired is. In principle, all other are fiber-reinforced Plastics imaginable as long as they are the required Have flexibility.

Since the housing dimensions of the control module due to the possible short design of the bending transducer are relatively small, it is appropriate to already in a corresponding housing To arrange control electronics for actuating the bending transducer. In this way, the link between the Control electronics and the bending transducer to be controlled very briefly being held. This can cause high electrical impulses Frequency are fed to the bending transducer.

Another advantageous embodiment of the control module provides for the control electronics on an electronic board to arrange and the rear end of the bending transducer on the Fasten the electronics board. This way a compact housing with small dimensions for the control module achieve.

FIG 1

eine Aufsicht auf eine vorteilhafte Ausgestaltung des Steuermoduls für eine Rundstrickmaschine;

FIG 2

eine Aufsicht auf eine weitere vorteilhafte Ausgestaltung des Steuermoduls für eine Rundstrickmaschine, wobei die Steuerelektronik in das Gehäuse integriert ist;

FIG 3

eine perspektivische Ansicht eines in dem Steuermodul gelagerten Biegewandlers, welcher beidseitig mit einer Piezokeramik versehen ist, und

FIG 4

die elektrische Beschaltung des in Figur 3 gezeigten Biegewandlers.

Embodiments of the invention are explained in more detail with reference to a drawing. In it show:

FIG. 1

a supervision of an advantageous embodiment of the control module for a circular knitting machine;

FIG 2

a top view of a further advantageous embodiment of the control module for a circular knitting machine, the control electronics being integrated in the housing;

FIG 3

a perspective view of a bending transducer mounted in the control module, which is provided on both sides with a piezoceramic, and

FIG 4

the electrical wiring of the bending transducer shown in Figure 3.

In Figure 1 is an advantageous embodiment in supervision of the control module according to the invention for use in a Jacquard circular knitting machine shown. In a housing 1 are 16 piezoelectric bending transducers 2 each with the same distance from each other and arranged parallel to each other. An upper housing part is not for reasons of clarity located. Each of the 16 piezoelectric bending transducers 2 is using a groove in a terminal block 6 on the respective rear end 5 firmly connected to the housing 1. Every bending transducer 2 is constructed from an electrically conductive Support body 3 in the form of a flat plate made of a carbon fiber reinforced Epoxy resin, which support body 3 on both sides each provided with a piezoelectrically active layer 4 is. The piezoelectrically active layer 4 is as one Lead-zirconate-titanium oxide ceramics designed so that the supporting body 3 and the respective piezoelectrically active layer 4 one almost identical in wide temperature ranges Have coefficients of thermal expansion. The surface of the piezoelectrically active layer 4 is for electrical contacting each with an electrode in the form of a thin one Provide metallization layer. Each bending transducer 2 is approximate along the entire length with an electrically insulating Surface coating provided for a light Achieve manageability. Only at the rear end 5 are the support body 3 and the two piezoelectric active layers 4 led to the outside, so that there easily control electronics can be connected. The electrical Contacting and wiring of the bending transducers 2 is shown in detail in Figures 3 and 4.

On the front, freely movable end 8 of each bending transducer 2 a cylindrical thickening 14 is clamped. The thickening 14 reaches into the rear part of one with the help of a Axis 12 on the housing 1 rotatably mounted rocker 10, the front End is formed as an elongated finger.

The control module is used to control the needles Bore 20 in a vertical position, i.e. with one another piezoelectric bending transducers 2 attached. During the Rotation of the knitting cylinder of the circular knitting machine becomes corresponding the position of the rocker 10 with the aid of a cam the corresponding board, which has a hub on the assigned Knitting needle transfers, brought into an operative position or not. The corresponding circuit board is used for this the knitting cylinder in the appropriate place with a Provide cams so that when the Control module one cam or one board exactly one is assigned to piezoelectric bending transducer 2. is For example, one of the rockers 10 in the position shown 18 so the cam of the associated board occurs with the Finger of the rocker 10 in contact when swiping past and will consequently placed in the operative position. Corresponding the operational position is a hub on the assigned Transfer knitting needle, which then results in a stitch formation is used. In the position shown 16 however, one of the rockers 10 kicks the cam of the associated one Do not use your finger to slide the board over Rocker 10 in contact, so that the board is not in the operational position. Accordingly, no stroke is opened transfer the associated knitting needle and consequently also not used to form a stitch.

To connect the control module shown in Figure 1, a Corresponding control electronics via connecting cables, connecting terminals or other electrical contacts with the piezoelectric bending transducers 2 connected. The control electronics can be attached to the housing 1 of the control module or with a corresponding length of the connecting cable attached to another part of the knitting machine become.

In Figure 2 is a particularly advantageous embodiment in supervision of the control module according to the invention shown. The structure corresponds essentially to the control module, which in Figure 1 is shown. With the same outer dimensions of the housing 1, the piezoelectric bending transducers 2 were compared by approximately 1/3 the bending transducers in Figure 1 shortened. At the same In this way, control electronics 20 can function integrate the housing 1. Control electronics 20 and control module are compact in this way in a single housing 1 accommodated.

Such a construction has the advantage that the electrical Connection cable between the control electronics 20 and the Bending transducers 2 can be kept very short, so that too Voltage pulses with high frequency applied to the bending transducer 2 can be. The control electronics 20 itself is on an electronics board 21 housed. Are symbolic corresponding to this in Figure 2 without further details electronic components 22 shown. For fixing of the respective rear end 5 of the bending transducer 2 is Terminal block 6 attached directly to the electronics board 21. The electronics board 21 itself is with the housing 1, here not shown, screwed.

The detailed structure and the electrical contact a bending transducer 2 according to Figures 1 and 2 is based a perspective view shown in Figure 3. Out For reasons of clarity, this is the electrically insulating one Coating of the bending transducer 2 not shown. The bending transducer 2 is fixed at its rear end 5 in one Nut of the terminal block 6 clamped. As already in the figures 1 and 2, the freely movable front end of the Bending transducer 2 movable over a cylindrical thickening 14 connected to a rocker 10, which via an axis 12 is rotatably attached to the housing 1. The one for the control module to control the needles of a circular knitting machine provided bending transducer 2 has a thickness 31 of 750 microns and a width 32 of 7 mm. The free length 30 measured from free end of the bending transducer up to its rear fastening point of the bending transducer is 38 mm, so the ratio the free length 30 of the bending transducer 2 to his Thickness 31 is 50. The support body 3 is, as already described on both sides with a piezoelectrically active Provide a layer made of a lead zirconate titanium oxide ceramic. There is a thin metallization on both sides for electrical contacting 7 on the respective piezoelectrically active Layer 4 applied. Both the support body 3 and the extend piezoelectrically active layer 4 applied on both sides facing away from the free end of the bending transducer Side to behind the terminal block 6. For electrical Contacting extends the support body 3 from a carbon fiber reinforced Epoxy over the length of the piezoelectric active layer 4. For electrical contacting are the support body 3 and the outer electrode acting metallization 7 of the respective piezoelectrically active Layer 4 via a solder contact 34 each with connecting cables 32 provided. The bending transducer 2 is with a so-called Provide three-pole connection.

According to the orientation in Figure 4, between the two outer electrodes or between the respective metallization 7 of the two piezoelectrically active layers 4 a potential difference of 200 V is applied. The direction of polarization 36 of the lead zirconate titanium oxide ceramics piezoelectrically active layer 4 shows on both Sides of the support body 3 in the direction shown, i.e. in the direction of that created by the applied potential difference electric field. For controlling the bending transducer 2 is now alternately a potential on the support body 3 of 0 V and +200 V. With a created Voltage of 0 V is that according to FIG. 4 at the top piezoelectrically active layer 4 falling potential difference equal to 0 V. There is no electrical field; the piezoelectric active layer is not activated. At the according FIG. 4 the piezoelectrically active layer 4 below on the other hand, a potential difference of 200 V drops. The emerging electric field points in the direction of polarization 36. The piezoelectrically active one below Layer 4 is therefore activated and contracts in the direction perpendicular to the applied electric field, i.e. perpendicular to the direction of polarization 36. As a result of this curves the bending transducer 2 shown in Figure 3 on its free End down so that your finger is over the axis 12 rotatably mounted rocker 10 moves upwards. Will the Support body 3, however, placed on a potential of +200 V, see above contracts accordingly the one according to FIGS. 3 and 4 above piezoelectrically active layer 4, so that the finger of the Rocker 10 moves down.

Claims (10)

1. Control module for controlling the needles of a knitting machine, with a casing (1) and at least one piezoelectric bending transducer (2) disposed therein, the bending transducer (2) comprising a flat support body (3) which is provided, on at least one side, with a piezoelectrically active layer (4) and is rigidly connected, at its rear end (5), to the casing (1), characterized in that the ratio of the free length (30) of the bending transducer (2) to its thickness (31) lies in a range between 40 and 70.
2. Control module according to Claim 1, characterized in that, for the purpose of controlling the needles, the bending transducer (2) can be actuated through application of a voltage of more than 100 V to the electrodes of the piezoelectrically active layer (4).
3. Control module according to Claim 2, characterized in that the piezoelectrically active layer (4) is a piezoceramic, and in that the electric field resulting from application of the voltage points in the polarization direction (36) of the piezoceramic.
4. Control module according to any one of Claims 1 to 3, characterized in that the bending transducer (2) is provided with a piezoelectrically active layer (4) on both sides.
5. Control module according to any one of Claims 1 to 4, characterized in that the thickness (31) of the bending transducer (2) lies in a range from 500 to 900 µm.
6. Control module according to any one of Claims 1 to 5, characterized in that the width (32) of the bending transducer (2) lies in a range from 2 to 10 mm.
7. Control module according to any one of Claims 1 to 6, characterized in that the support body (3) consists of a fibre composite material.
8. Control module according to any one of Claims 1 to 7, characterized in that control electronics (20) are disposed in the casing (1) for the purpose of actuating the bending transducer (2).
9. Control module according to Claim 8, characterized in that the control electronics (20) are disposed on an electronics board (21), and in that the rear end (5) of the bending transducer (2) is attached to the electronics board (21).
10. Control module according to any one of Claims 1 to 9, characterized in that several bending transducers (2) are provided, disposed in parallel to one another.

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