EP0095709B1 - Yarn furnisher for a knitting machine with striper - Google Patents

Description

The present invention relates to a yarn feed apparatus according to the preamble of claim 1.

From EP-A-0 028 412 a generic yarn feed device is already known which also has a circuit connected to the position sensor for switching off the knitting machine. During a large part of the work cycle, with the exception of a certain yarn change period, which occurs periodically, the circuit formed from a holding relay switches off the knitting machine as soon as all position sensors simultaneously indicate that the yarns are not being fed.

In the yarn feeder known from EP-A-0 028 412, the yarn guide elements are moved by magnets in the non-feed areas, while their movement in the feed areas are brought about by increased yarn tensions resulting from the work of the fingers in the ringing mechanism. However, yarn feeders are also known in which the movement of the yarn guide elements is brought about exclusively by the changes in tension in the yarn due to the working of the fingers of the ringing mechanism. Each yarn transport element is a constantly driven belt that runs over a freely rotatable roller. As soon as the yarn guide element moves the yarn under the belt, it takes the yarn with it and conveys it to the associated finger. Conversely, when the yarn guide element moves into the non-feed area, the yarn is moved out from under the belt and remains there. In the latter, known yarn feeder, it is necessary that the path of movement of the guide element is sufficiently long in each case so that the yarn guide element compensates for an inevitable wobble movement of the yarn, which results from the inertia of the yarn mass and the yarn elasticity when the previously effective acceleration by the yarn transport element is suddenly dismantled. The position sensor connected to the yarn guide element indicates a yarn break with a signal in an end position of the yarn guide element in the non-feed area, which end position the yarn guide element can only reach if the yarn guide element was able to move in addition to the normal trailing movement due to the yarn break. The knitting machine is switched off with this signal. In all other positions in the non-feed area and in the feed area, the position sensor emits no signal. The disadvantage here is that no signal can be generated with the position sensor if a yarn error occurs in which the knitting machine does not consume the amount of yarn supplied properly, for example as a result of a malfunction in the course of the yarn to the ringing mechanism and to the knitting needles or due to soiled eyelets or one wrong knitting machine setting. In the case of such errors, the tension in the yarn running out of the yarn feed apparatus is reduced, as a result of which the guide element moves the yarn out of the feed area without, however, reaching its end position. Shortly thereafter, the yarn tension increases again because the positive feed has ended, whereby the yarn guide element moves the yarn back into the feed area. The position sensor does not react to this yarn error, conversely the guide element can reach its end position in which a switch-off signal is initiated via the position sensor if the tension in the incoming yarn slowly decreases if this yarn has not been processed for a long time and due to vibrations or begins to sag due to air currents. Such a fault is particularly difficult to find out if the contact function of the position sensor is not sufficiently sensitive and can cause the knitting machine to stand still for a considerable time. Another yarn error is present when two yarns are processed simultaneously in the ringing mechanism after a color change. This yarn error is also not indicated by the position sensor since it does not reach its end position.

Compared to this prior art, the object of the present invention is to develop a generic yarn feed device in such a way that further yarn feed errors can be detected.

This object is achieved in a yarn feed device of the generic type by the features in the characterizing part of claim 1.

Preferred embodiments are the subject of the dependent claims.

Embodiments of the invention are explained below with reference to the drawings.

• Fig. 1 eine schematische Seitenansicht eines Garnzuführapparates,
• Fig. 2 eine erste Ausführungsform der elektrischen Schaltung des Garnzuführapparates von Fig. 1,
• Fig. 3 eine zweite Ausführungsform der elektrischen Schaltung, und
• Fig. 4 eine weitere Ausführungsform der elektrischen Schaltung.

Show it:

• 1 is a schematic side view of a yarn feeder,
• 2 shows a first embodiment of the electrical circuit of the yarn feed apparatus of FIG. 1,
• Fig. 3 shows a second embodiment of the electrical circuit, and
• Fig. 4 shows another embodiment of the electrical circuit.

1, a yarn feeder has a housing 1, which is attached to a fastening section 2, with which the yarn feeder can be fixed to a circular support ring 2 'in a horizontal ring knitting machine above an associated knitting station. In a multi-system ring knitting machine, as many yarn feeders are provided as the knitting machine has knitting stations. The fastening section 2 extends partly in and partly below the housing 1 and forms a support plate 2a for a vertical axis 3, on which four yarn feed wheels 4A, 4B, 4C and 4D are freely rotatably mounted, one above the other. Part of the circumference of each yarn feed wheel is from a belt 5A, 5B, 5C, 5D embraced. The belts are driven in a known manner in accordance with the knitting machine, in this case to feed four yarns FA, FB, FC, FD which come from yarn spools, not shown. The yarns are then fed, preferably via guide eyes, to the fingers in a ringing mechanism (not shown), from which they then run to the knitting needles in the knitting machine.

In the housing 1, yarn guide elements 6Ain, 6Bin, 6Cin, 6Din and 6Aout, 6Bout, 6Cout, 6Dout are each pivotably mounted in pairs, with an inlet guide element 6Ain, 6Bin, 6Cin, 6Din for each yarn FA, FB, FC, FD and a drain feed element 6Aout, 6Bout, 6Cout, 6Dout, which is firmly connected thereto, is provided.

Each feed guide element 6Ain, 6Bin, 6Cin, 6Din can be pivoted back and forth between a feed area and a non-feed area against the force of a spring, not shown, which acts counterclockwise, as can the drain guide elements 6Aout, 6Bout, 6Cout, 6Dout. When the yarn guide member of a yarn is in a feed area position, the yarn lies under the belt and is fed positively by it. If, on the other hand, the yarn guiding element of a yarn is in the non-feed area position, the yarn lies outside the engagement area of the belt and is no longer conveyed.

In Fig. 1, the inlet guide element 6Ain and the outlet guide element 6Aout are in the feed area position, so that the yarn FA is fed positively, while the other yarn guide elements are in their non-feed area positions, so that the other yarns FB, FC, FD are not fed.

The yarn guide elements are mounted in the housing 1 with shafts 8 lying perpendicular to the plane of the drawing (FIG. 1). A contact pin 7A ', 7B', 7C ', 7D' is connected to each shaft and, together with a correspondingly arranged contact plate 7a ", 7B", 7C ", 7D", forms an electrical position sensor for the respective position of the associated yarn guide element.

In this exemplary embodiment according to FIG. 1, the contact plates 7A ", 7B", 7C ", 7D" are only conductive in the left part, while they are non-conductive in the right part. In this way, the position sensor emits a signal when the associated yarn guide element is in the feed area position, while no signal is generated in the non-feed area position. Of course, this arrangement could also be reversed. The transition from the non-conductive part to the conductive part of each contact plate is arranged so that a signal is generated precisely when the associated yarn comes out of the engagement of the belt 5A, 5B, 5C, 5D or runs in under the belt, i.e. The switching points of the position sensors are precisely in these border areas, in which a positive delivery of the yarn begins or ends. The respective signal is then maintained unchanged when the yarn guiding element continues to move within the non-feed area or the feed area.

The contact plates 7A ", 7B", 7C ", 7D" are connected via a connecting line to a control relay CR, which on the other hand is connected to a positive voltage supply in the housing 1. The contact pins 7A ', 7B', 7C ', 7D' are connected via a common line to a negative voltage supply, also in the housing 1. The control relay CR has its relay contacts CR _c in a circuit which is routed via the switch-off relay of the knitting machine. This switch-off relay switches off the knitting machine, for example, when it is energized. This circuit in the housing forms an electrical logic switching unit which works in the aforementioned manner and then switches off the knitting machine when certain signal combinations are generated by all position sensors, which will be explained later.

Fig. 2 shows a circuit as it is known from EP-A-0 028 412 and which can be used in the yarn feeder of Fig. 1 per se, where a timing element or a timing circuit TC with a possibly before the control relay CR Time delay of t _{o is} provided. The position of the contact pins or the shafts 8A, 8B, 8C, 8D of the yarn guide elements corresponds to that shown in FIG. 1.

1, ie in the positions of FIG. 1, the yarn FA is fed positively. The associated contact pin 7A 'closes the contact with the contact plate 7A ", the direct current circuit from (-) (+) via the control relay CR and the possibly arranged timing element TC being closed. In the case of this circuit, this means that the control relay CR is tightened and keeps the contacts CR _c open, so that the circuit for the switch-off relay of the knitting machine is open. The knitting machine works. In the event of a yarn break in the yarn FA or a drop in the yarn tension due to an external influence, the yarn guide element 6Aout swings upward while the feed yarn guiding element 6Ain swings down. The contact pin 7A 'reaches the non-conductive area of the contact plate 7A ", so that the direct current circuit via the control relay CR is interrupted and the control relay CR drops out. The contacts CRc of the control relay CR close the circuit for the switch-off relay of the knitting machine, so that the knitting machine is switched off immediately.

The timer TC (FIG. 2) can be provided in the event that there is no overlap between the old and the new yarn in the knitting machine during a yarn change. This timer with its time t _o then bridges the short period of time during which no feed area signal occurs.

Another yarn error (overfeed) is when, for some reason, the old yarn being processed or a new yarn does not know properly from the knitting needles processed or has not been properly passed on to the knitting needles by the respective finger in the ringing mechanism. The position sensor for this yarn will generate a non-feed area signal as a result of the yarn tension reduction occurring with this yarn error, or a feed area signal will then no longer be generated by any position sensor of all the position sensors provided. The logical switching unit responds to this signal combination and actuates the switch-off relay, whereby the knitting machine is switched off suddenly.

However, this circuit does not respond if there is another yarn fault, namely if after changing the yarn the old yarn, which may no longer be processed, remains tensioned because e.g. has not been cut correctly in the striping mechanism or in front of the knitting needle. The old yarn is then also processed with the new yarn, i.e. both yarns are fed positively. In this case too, the knitting machine is to be switched off according to the invention. In the embodiments according to FIGS. 3 and 4, this is done in that the electronic switching unit provided in each case (indicated by dashed lines in FIG. 3A, in FIG. 4) detects a signal combination from the position sensors that indicates this yarn error condition and then switches off the knitting machine.

3, the contact plates 7A ", 7B", 7C ", 7D" are connected to a number of input connections of an electronic logic switching unit A, which, for. B. from conventional electronic logic components (as Fig. 4) or is formed by a microprocessor. The output of the logic switching unit A is connected to the coil of a control relay CR _A , the relay contacts of which lie in a circuit of the switch-off relay of the knitting machine.

The electronic logic switching unit A is designed so that it generates an output signal for switching the control relay CR _A under two fault conditions represented by certain signal combinations, in which the switch-off relay of the knitting machine is actuated.

The first fault condition consists of n non-feed area signals from the position sensors 7A ', 7A ", 7B', 7B", 7C ', 7C ", 7D', 7D", where n is the number of position sensors. This signal combination of n signals indicates that no yarn is being knitted or that the yarn intended for knitting is broken.

The second error condition is indicated by a signal combination consisting of (n minus a number greater than 1) signals, where n is the number of position sensors available. In other words, a signal combination in which more than one feed area signal is present at the same time as non-feed area signals represents this error condition. B. two yarns can be knitted simultaneously.

For both error conditions, the logic switching unit can be designed in such a way that it outputs an output signal for the switch-off relay of the knitting machine with a certain time delay, e.g. 20 milliseconds to prevent the knitting machine from being switched off incorrectly when changing yarn. Because when changing yarns with an overlap, two yarns are fed simultaneously for a short time, while when changing yarns without overlap, a certain amount of time is not fed at all, because the old yarn is no longer fed and the new yarn is not yet fed.

In the embodiment of FIG. 4, the position sensors are formed by four phototransistors T1 to T4 and four photodiodes D1 to D4 as opto-electronic position sensors for the yarn guide elements. The emitters of the phototransistors T1 to T4 are connected via a resistor network NET _r to an input of a first operational amplifier OP ₁ and to an input of a second operational amplifier OP ₂ . The other, negative input of the first operational amplifier OP ₁ is supplied with a reference voltage value. The other and positive input of the second operational amplifier OP ₂ is also connected to a reference voltage. The output of the first operational amplifier OP ₁ is connected to an input of a first NOR gate NOR ₁ . The output of the second operational amplifier OP ₂ is connected via an intermediate resistor and a first timing circuit RC ₁ to the second input of the first NOR gate NOR _i , the timing circuit RC ₁ having a time constant of approximately 140 milliseconds, for example. The output of the first NOR gate NOR ₁ is applied to both inputs of a second NOR gate NOR ₂ , the output of which is connected to a hold circuit via a second timing circuit RC ₂ . The timer circuit RC ₂ has a time constant of approximately 60 milliseconds, for example. The hold circuit consists of two NOR gates NOR ₃ and NOR ₄ , the output of the NOR gate NOR _{2 being} connected via an intermediate resistor to one input of the NOR gate NOR _{3 of} the hold circuit. The other input of the NOR gate NOR ₃ is connected via a feedback loop to the output of the NOR gate NOR _{4 of} the hold circuit. The output of the NOR gate NOR ₃ is connected to one input of the NOR gate NOR ₄ , while the other input of the NOR gate NOR _{4 is} connected to a contact of a reset switch SW ₁ via a resistor and a capacitor. The output of the holding circuit is connected to the base of a further transistor T5, which is connected via a connecting line to the switch-off relay of the knitting machine, an earthed indicator lamp L for visual indication of a fault condition being located in the connecting line.

The holding circuit NOR ₃ and NOR ₄ keeps the switch-off relay of the knitting machine open after the occurrence of an error condition until this error condition is deleted by actuating the switch SW ₁ .

The two operational amplifiers OP ₁ , OP ₂ and / or also the NOR elements NOR, -NOR ₄ can expediently each be contained in an integrated circuit of conventional design, which simplifies the manufacture of the circuit and keeps the space for accommodating the circuit small.

A switch SW _{2 is} arranged between the position sensors and the two operational amplifiers OP ₁ and OP ₂ via intermediate resistors, with which the position sensors can be bridged under certain operating conditions. A diode is used in the connecting line between the switch SW ₂ and the second operational amplifier OP ₂ .

This electronic logic switching unit according to FIG. 4 is attached to the inside of the housing 1 of the yarn feed apparatus according to FIG. 1, as indicated in FIG. 1. In the first and aforementioned fault condition, all four transistors T1 to T4 become conductive. Because of the first operational amplifier OP ₁ superior resistors R ₁ and R ₂ is the resistance network NET _R at the _1, a voltage level queue an input of the first operational amplifier OP, so that its output delivers a high voltage level or a voltage potential representing a as a signal corresponds to binary 1. If this high voltage potential is maintained for more than 60 milliseconds, the signal finally passes through to the base of transistor T5, which makes this transistor conductive and sends a switch-off signal on the connecting line to the switch-off relay of the knitting machine, which is generated by the holding circuit NOR ₃ and NOR ₄ is maintained and the lamp L also lights up.

In the second fault condition, only two of the four transistors T1 to T4 or less become conductive, so that a voltage level is applied to the one input of the second operational amplifier OP via the special design of the resistors R ₃ and R ₄ , which are placed in front of one input of the second operational amplifier OP _{2 is} supplied. The first operational amplifier OP ₁ is designed so that it does not respond to this voltage level. In contrast, the operational amplifier OP ₂ outputs a high potential at the output, which is supplied to the second input of the NOR element NOR ₁ via the timing circuit RC ₁ . If the high potential from the output of the second operational amplifier OP ₂ lasts longer than 140 milliseconds and 60 milliseconds = 200 milliseconds, the base of the transistor T5 receives a voltage potential, as a result of which the transistor T5 becomes conductive and generates a switch-off signal.

The invention is not intended to be limited to the exemplary embodiments explained above. These exemplary embodiments are only intended to provide an understanding of the idea according to the invention of generating a signal from the yarn movement between the feed area and the non-feed area exactly in the transition area from the positive feed to no feed and together with the signals which depend on the positions of the other yarns. Form signal combinations that exactly represent the presence of error conditions in which the knitting machine must be switched off. It is of secondary importance how the knitting machine is ultimately switched off. Depending on how the signals are evaluated by the bearing sensors, it is advantageous to choose whether the yarn fed in or the yarn not fed in is monitored, i.e. each feed area signal will then be a positive signal (e.g., a binary 1), while the non-feed area signals will be negative signals (e.g., binary 0), or vice versa. The preference is to give a check of the yarns that have not just been fed for several reasons.

Claims (9)

1. Yarn feeding device for the positive feed of several yarns to the striping mechanism of a knitting machine with striper, with fingers arranged movably in the striping mechanism for selectively and successively receiving the yarn and transferring it into a knitting position and for removing the yarn from a knitting position, with a number of delivery devices (1) corresponding to the number (N) of yarns (FA to FD) and each with a yarn transport element (5A to 5D) and a yarn guide element (6A to 6D) which are each movable to and fro between a feed region, in which the yarn is in the range of engagement of the yarn transport element, and a non-feed region, in which the yarn is outside the range of engagement of the yarn transport element, there being provided for each yarn guide element an electrical position sensor (7A to 7D, 8A to 8D) which generates a signal representing the feed or non-feed of the yarn (FA to FD), and with a circuit (A; NET_R, OP, NOR) for switching off the knitting machine which is connected to the position sensors, characterized in that the circuit switches off the knitting machine when either at least two signals representing the feed of the yarn or at most (N-2) signals representing the non-feed of the yarn are present simultaneously, N being the number of position sensors (7A to 7D, 8A to 8D).

2. Yarn feeding device according to Claim 1, characterized in that the circuit (A; NET_R, OP, NOR) switches off the knitting machine when either N signals representing the non-feed of the yarn are present simultaneously, N being the number of position sensors (7A to 7D, 8A to 8D), or no signal representing the feed of the yarn is present.

3. Yarn feeding device according to Claims 1 or 2, characterized in that the position sensors (7A', 7A", 7B', 7B", 7C', 7C", 7D', 7D"; T1, D1, T2, D2, T3, D3, T4, D4) are designed as switches or as optoelectronic switches.

4. Yarn feeding device according to one of Claims 1 to 3 characterized in that the switch unit converts the signals of the position sensors into a voltage level which is directly or indirectly proportional to the number of feedregion signals.

5. Yarn feeding device according to Claim 4, characterized in that the voltage level is proportional to the number of non-feed region signals.

6. Yarn feeding device according to at least one of Claims 1 to 5, characterized in that the switch unit has two comparators (OP1, OP2) which determine the presence of an error condition for switching off the knitting machine as a result of a comparison of the voltage levels with reference voltages.

7. Yarn feeding device according to at least one of Claims 1 to 6, characterized in that the switch unit contains a holding circuit (NOR3, NOR4) which keeps the knitting machine switched off after an error condition has occurred.

8. Yarn feeding device according to Claim 7, characterized in that the holding circuit (NOR3, NOR4) can be reset by means of a switch (SW1).

9. Yarn feeding device according to at least one of Claims 1 to 8, characterized in that the switch unit is mounted on the inner face of a housing wall of the yarn furnisher (1).

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