ELECTRONIC CONTROL DEVICE TO DISCRIMINATE FALSE CONTACTS AND SIGNAL TEMPORARY CONTACTS IN A LOOM WARP STOP MOTION DEVICE

Abstract: Electronic control device to discriminate the false contacts and to signal the temporary contacts in a warp stop motion device of a loom. Said control device allows to discriminate the temporary closing of the electric circuits of the banks determined by electrostatic phenomena, from those determined by temporary contacts of the drop wires, detecting the presence or absence, for a predetermined number of successive cycles, of the electric signals existing on the circuits of the banks, by means of a high-frequency synchronous time sampling.

Description: ELECTRONIC CONTROL DEVICE TO DISCRIMINATE FALSE CONTACTS AND SIGNAL TEMPORARY CONTACTS IN A LOOM WARP STOP MOTION DEVICE" ===o0o=== The present invention concerns an electronic control device to discriminate the false contacts and to signal the temporary contacts in a warp stop motion device of a weaving loom. In particular, the invention concerns an electronic control device for the operation of a warp stop motion device, allowing to discriminate the temporary closing of the electric circuits of the banks determined by electrostatic phenomena (hereinafter indicated as false contacts) from that determined by temporary contacts of the drop wires (hereinafter indicated as temporary contacts) and thus allowing, in the first case, to prevent any undesired loom stops and, in the second case, the operator to promptly locate the warp zone concerned by such temporary contacts . As well known to the skilled in the art, the warp stop motion device is a device used in looms to control the constant integrity and continuity of each single warp yarn. Said device generally consists of one or more contact rods, named "banks", positioned transversely to the warp yarns and above the same. Each bank is formed by an outer U-shaped body and an inner core, both of metal, separated by a thin sheet of insulating material. Each bank carries a plurality of "drop wires", namely thin metallic laminae, each drop wire comprising a slot - to allow its insertion on the bank - and an underlying hole, into which is inserted a warp yarn. During working of the loom, the body and the core of each bank are connected to the terminals of an electric detection circuit, while the drop wires are kept lifted above the bank by the tension of the warp yarns sliding through the hole of said wires. When one of the warp yarns breaks or loosens, the respective drop wire, no longer held up by the tension of said yarn, drops onto the bank creating a metal bridge between the body and the core of said bank, and thereby closing the electric circuit connected thereto. The closing of the electric circuit of one of the banks leads to the start of an automatic procedure to stop the loom and to signal the fault to the operator. Said warning normally includes both a rough or general signal - usually a signal light or an audible signal positioned on the loom turret - which allows the operator to ascertain, even from a distance, that the loom has stopped, and a fine or specific signal - usually a signal light positioned at one end of each bank - which allows the operator to reckon at once which of the different banks is involved with the broken warp yarn. More recently, it has been proposed to produce banks having a special structure, thanks to which the fine signal does not merely indicate the bank concerned with the broken warp yarn, but also the particular zone of said bank in which the breaking has occurred, so as to make it far quicker for the operator to seek the broken yarn. These improved signaling means also consist of signal lights or displays apt to indicate the position of the broken warp yarn thanks to their special positioning along the bank, or thanks to a numerical indication representing the distance between the point of yarn breakage and a "zero" reference point, normally corresponding to the starting end of the bank. In the practical accomplishment of a weaving operation, the theoretical situations described heretofore - namely those wherein the electric circuits of the banks find themselves only in the steady OPEN (no wire has dropped) or CLOSED (at least one wire has dropped) conditions - suffer however from several exceptions. In other words, there are frequent conditions in which the closing of the electric circuit of the bank takes place for a short lapse of time, whereupon the OPEN circuit condition is at once recovered. As already briefly mentioned further above, such temporary closing conditions of the electric circuits of the banks may correspond to quite different weaving conditions. To start with, there can be exclusively electric reasons: in fact, the movement of the warp yarns through the thousands of drop wires produces thereon an accumulation of static charges which may periodically discharge onto the electric circuit of a bank, determining its temporary closing. In the sector this situation is commonly called "false contact". There can moreover be mechanical reasons: in fact, a particular faulty condition may arise in the weaving operation - indicated by the skilled in the art as "temporary contact" - in which a warp yarn loosens to such an extent that the respective drop wire comes in contact with the bank, thereby closing the signaling circuit thereof, but soon after said yarn partially recovers its tension, hence lifting again the drop wire above the bank and restoring the OPEN condition of the electric circuit of said bank. This particular faulty condition can however be determined either by a temporary loosening of the warp yarn - which, in itself, may also not give rise to appreciable defects in the fabric - or, viceversa, by a true and proper breakage of the warp yarn, which however gets caught into the adjacent yarns and thus keeps the respective drop wire lifted above the bank. This last condition is of course far more serious, as it would give rise to the forming of a highly defective fabric; it is thus necessary for the operator to anyhow carry out an accurate control on the warp yarns, even in the case of a "temporary contact". On the other hand, since it is not possible, with the warp stop motion devices of prior art, to discriminate the "false contacts" from the "temporary contacts", the need consequently arises for the loom to be anyhow immediately stopped each time the warp stop motion detects one of such contacts, and for the aforecited rough signal of loom stopping to remain lighted in order to warn the operator of the existence of a problem in the feeding of the warp yarns. Viceversa, the aforecited fine signal immediately disappears upon ceasing of the false contact or of the temporary contact, just because said fine signal directly derives from the electric contact which the drop wire produces on the respective bank. The operator is hence compelled, whenever the contact is not permanent, either to check the whole group of warp yarns - so as to trace the yarn potentially affected by the temporary contact and, if necessary, provide to repair the same - or else to conclude that all the warp yarns are in a regular position and gather that it was a false contact. It seems evident from the above that this operation not only involves a considerable waste of time, but also requires the presence of highly skilled labor, namely capable of detecting, with certainty and within acceptable time limits, the presence or the absence of a fault among the warp yarns, failing any type of aid signal. The object of the present invention is to thus supply a control device which allows, first of all, to discriminate the false contacts from the temporary contacts , preventing the stopping of the loom when a false contact takes place. Another object of the present invention is to supply a signaling device which allows the operator to promptly locate the position of a warp yarn which has determined a temporary contact on the warp stop motion device, being guided by signals which are similar to those normally issued by said device when a warp yarn has definitively dropped, whereby the drop wire has come into permanent contact with the bank. According to the present invention, said objects are reached with an electronic control device for a warp stop motion device of a loom - of the type comprising: a plurality of side-by-side banks onto each of which there is inserted a plurality of drop wires, kept lifted above the bank by the tension of a respective warp yarn sliding through a hole or slot thereof; means to control the stopping of the loom; and signaling means to indicate the bank, or a zone thereof, onto which a wire has dropped - characterized in that it comprises an electronic circuit, apt to detect the current signals in the electric circuits of each bank of the warp stop motion device, and a processing unit apt to control said electronic circuit and to process the signals issued thereby, discriminating the false contacts, due to electrostatic discharges or other electric transients on the bank, from the true contacts due to the dropping, even temporary, of a drop wire on a bank and, in case of a true contact, stopping the operation of the loom and issuing a first warning sign referring to said bank, or bank portion. According to a characteristic of the invention, said processing unit, after having reckoned a true contact, further process the relative signal, checking if the true contact is or becomes a temporary contact and issuing, in this last case, a second warning sign. In a preferred embodiment of the invention, said current signal in the electric circuits of each bank of the warp stop motion device are converted into digital signals before sendig the same to said processing unit. According to a characteristic of this preferred embodiment of the invention, for discriminating the false contacts due to electrostatic discharges or other electric transients on the bank, from the true contacts due to the dropping, even temporary, of a drop wire on a bank, the processing unit performs the following operations on the above said signals: - detecting the presence, or the absence, of the current signal in the electric circuits of each bank or bank portion of the warp stop motion device, with a time sampling; - adding, for each sampling cycle and for each bank or bank portion, a preset value for any sampling cycles in which the presence of the signal has been detected, in an adder device; - subtracting the same preset value, or otherwise cancel all the added values, for any sampling cycles in which the absence of the signal has been detected, from the above said adder device; comparing the total value of said adder device with a predetermined threshold number (n, β) ; and - reckoning as a signal indicating a true contact of the drop wire on the bank the one for which the total value of said adder device has become equal to said threshold number. According to a further characteristic of the invention, for checking if the reckoned true contact is or becomes a temporary contact the processing unit performs the following operations on the above said signals : - continuosly detecting, with a time sampling, the presence or the absence of the current signal on the electric circuit of the bank, or bank portion, on which the true contact has occurred; - adding, for each sampling cycle and for each bank or bank portion, a preset value for any sampling cycles in which the absence of the signal has been detected, in an adder device; - subtracting the same preset value, or otherwise cancel all the added values, for any sampling cycles in which the presence of the signal has been detected, from the above said adder device; comparing the total value of said adder device with a predetermined threshold number (m, 3) ; and - reckoning as a signal indicating a temporary contact of the drop wire on the bank the one for which the total value of said adder device has become equal to said threshold number. According to a still further characteristic of the invention, said second intermittent signal light is associated to, or replaces, said first continuous signal light. The invention will now be described in further detail, with reference to the accompanying drawings, in which: Fig. 1 is a block diagram showing the general operating modes of the electronic control device for the warp stop motion device of a loom, according to the present invention; and Fig. 2 is a flow diagram showing the sequence of logic operations performed inside the processing unit of the electronic control device. According to the present invention, the electronic control device for the warp stop motion device of a loom is characterized - compared to the known-type electronic control devices - by the integration of a microprocessor in a signal detection electronic circuit known per se. Through appropriate algorithms, it is possible to process the signal in said microprocessor according to a sequence of logic operations, which allow to discriminate the false contacts from the true contacts and furthermore, among the true contacts, to signal in a different way the temporary contacts in respect of the permanent contacts . The block diagram of fig. 1 does not hence illustrate the general diagram of the circuit to detect and process the electric signal present on the electric circuits of the banks of the warp stop motion device G, which is achieved in a fully conventional way. Said conventional signal detection and processing electronic circuit is represented by the block E and also comprises a voltage generating unit and an analog-to-digital signal converter. The operation of the block E is controlled by the processing unit C consisting of a microprocessor, for example of the type produced by Motorola and sold under the code 68HC705J1A. The processing unit C also controls a first warning sign A and a second warning sign B, as well as a device S to stop the main motor of the loom. The sequence of logic operations performed by the processing unit C in a first embodiment of the present invention is now described, making reference to the flow diagram of fig. 2. To simplify the description, reference will be made hereinafter to the electric circuit of a single bank of the warp stop motion device; it is evident, however, that the operations described hereunder are repeated by the unit C exactly in the same way for all the banks or controlled bank portions existing in said device, by turning on the respective signal lights thereof. The unit C thus provides first of all to request the block E to perform a time sampling of the signal present on the bank (block 1), receiving in response a digital signal indicating the presence or the absence of the signal on said bank. Preferably the signal sampling lenght is much shorter than the sampling period, so that many false contacts having a short lenght are not detected at all or are detected in a reduced number of sampling cycles. For instance the signal sampling lenght is of the order of microseconds, while the sampling period is of the order of tenths of millisecond and it is preferably of the synchronous type. The digital signal indicating the presence or the absence of an electric signal on the circuit of the bank is then checked by the unit C (block 2), after having previously verified whether a warning flag (block 5) is already active or not. A description is now given of the operation of the unit C in the condition in which the warning flag is not active, while the operation of the unit C in the opposite condition shall be described subsequently. After having thus verified that the warning flag is not active, the digital signal is checked to reckon whether it indicates the presence (value 1) or the absence (value 0) of an electric signal on the electric circuit of the bank. If the signal is equal to 1, this value is added in a special counter (block 3); if it is instead equal to 0, the totalizator of the counter is reset to zero. The signal control process thus continues in a cyclic way, until the unit C has detected a predetermined number n of successive cycles in which the signal is present, namely until the totalizator of the counter has actually reached said value n. The value n has to be experimentally set according to the operating conditions, to the type of fabric, to the increased or reduced presence of electrostatic charges, and so on. In the working logic of the device according to the first embodiment of the present invention, the control of signal presence for a sufficiently high number of successive synchronous cycles is actually carried out for the purpose of discriminating the false contacts from the true contacts. From a statistical point of view, it is in fact highly improbable that an electrostatic discharge, or another electric transient on the bank, may arise with continuity and regularity for n successive sampling cycles, each having a very short lenght. It is thus evident that, if the counter should have totalized a signal presence for n successive cycles, one is certainly in the presence of a true contact, namely of a wire having dropped onto the bank, possibly even just temporarily. It should in fact be noted that the number n can be chosen sufficiently high to discriminate the false contacts, but sufficiently low to include, among the true contacts, also the temporary contacts of the drop wire on the bank. Since, in fact, the temporary dropping of the wire is a mechanical and not an electrical phenomenon, however short it may be it will anyhow last for a length of time of the order of thousandths of a second. During this contact period, the unit C is hence in a position to carry out a sufficiently high number of signal detections. From the first experimental tests of the device according to the present invention, it has been found that the number n is advantageously set between 2 and 20, and preferably between 3 and 10. The total number indicated by the counter (block 3) is verified by a detector of emergency conditions (block 4) which, as soon as it reckons that the preset threshold value n has been reached on the totalizator of the counter, it issues control signals to the loom stopping device S and to a first warning sign A. The value of the warning flag (block 5) - which is verified by the signal presence check (block 2), before acting on the counter (block 3) - is simultaneously changed from 0 to 1. In fact, when the above said control signals have been issued by the detector of emergency conditions (block 4), whereby the loom has been stopped and the value of the warning flag (block 5) has been brought to 1, the logic of the signal presence check (block 2) is changed as follows: - if the presence of a signal is detected, no further operation is carried out; - whereas, if the absence of the signal is detected, a second warning sign B is issued or, alternatively, the pre-existing warning sign A is modified. The signal absence detected by the signal presence check (block 2) corresponds in fact to the condition of a temporary contact, whereby the second warning sign B allows the operator, not only to know in which position the inconvenience has occurred (this information being always supplied to him by the sign A, which is left active), but also to knov.- what type of inconvenience has occurred (namely, a temporary contact instead of a permanent contact ) . If there should arise any phenomena of vibrations, or of slow damping of the oscillations due to dropping of the wire onto the bank - which phenomena can cause the temporary absence of the signal even when a permanent contact of the drop wire has actually occurred - an additional function can be foreseen (fully similar to the one illustrated in blocks 3 and 4), which provides to issue the second warning sign B only after the signal absence has been detected for m successive cycles, wherein m is the higher than 0 the longer the times required for damping the oscillations of the wire on the bank after it has dropped. Preferably, the second warning sign B is in the form of an intermittent signal light. In this case, it can advantageously consist of the same signal light used for the first warning sign A, by changing its working from a continuous one to an intermittent one. In this last case, it is evident that, when a permanent contact occurs, whereby the respective signal light is of the continuous type, said light will suddendly change into an intermittent signal light as soon as the operator will have provided to lift the drop wire above the bank; this change of signal light evidently creates no inconvenience to the operator who, in this case, actually receives a further confirmation to have operated on the actual drop wire which has determined the issue of the warning sign A. When the operator, guided by the aforedescribed indications, has finished repairing any possibly broken or loosened warp yarns and the loom is started again, the electronic control device according to the present invention automatically provides to zero-set both the totalizator of the counter (block 3) and the value of the active warning flag (block 5), whereby said device is set in conditions to start again the type of operations described heretofore. A sligthly different working logic of the device is provided in the second embodiment of the present invention, which embodiment can be successfully used in weaving looms where the drop wires should normally present high vibration phenomena, or a very slow damping of the oscillations due to the dropping thereof onto the bank. In this case, in fact, even in presence of a true contact of the drop wire, it is highly likely that the signal presence check (block 2)does find the above said number n of successive synchronous cycles sufficient to stop the loom only too late, i.e. when a defective cloth has already been woven. A different approach has been therefore studied for these cases , and the same will be discussed thereafter, referring to the same flow diagram of fig. 2. According to this approach when the signal presence check (block 2) reckons the presence of an electric signal on the bank (value 1 of the digital signal), a value 1 is added to the counter; when, on the contrary, it reckons the absence of the electric signal (value 0 of the digital signal), a value 1 is subtracted from the counter (block 3). The above described signal control process thus continues until the totalizator of the counter has reached a predetermined value p, namely until the unit C has detected a numer of cycles in which the signal is present higher, for said value p, than the detected number of cycles in which the signal is not present. Preferably the counter (block 3) is reset to zero at regular intervals of time, to prevent that the value p be seriously affected by any electrostatic discharge, or other electric transient on the bank. The above said approach is based on the following, statistically verified, assumptions. Firstly, that a true contact of the drop wire, even if affected by vibration phenomena or by a very slow damping of the oscillations, gives, from the very first contact, a number of sampling cycles in which is detected the signal presence higher than the number of sampling cycles in which is detected the signal absence. Secondly, that an electrostatic discharge or another electric transient on the bank gives, at least within a sufficiently short range of time, a number of sampling cycles in which is detected the signal presence lower than the number of sampling cycles in which is detected the signal absence. Experimentally adjusting the value j> it is so easy to discriminate between false and true contacts of the drop wire. The number p can in fact be chosen sufficiently high to discriminate the false contacts, but sufficiently low to include, among the true contacts, also the temporary contacts of the drop wire on the bank. Since, in fact, the temporary dropping of the wire is a mechanical and not an electrical phenomenon, however short it may be it will anyhow last, as already seen, for a length of time of the order of thousandths of a second. During -this contact period, the unit C is hence in a position to carry out a sufficiently high number of signal detections. From the first experimental tests of the device according to the present invention, it has been found that the number p_ is advantageously set between 0 and 15, and preferably between 2 and 12, while the range of time within which the signal presence or absence is counted is non particularly limited and depends from the particular weaving conditions of the loom. In normal applications, said range of time is usefully set in the order of tens of milliseconds, advantageously between 30 and 70 milliseconds, and preferably between 40 and 60 milliseconds. From what above stated, it should be clear that at the end of any range of time, as defined heretofore, if the counter (block 3) has not yet reached the preset value p., it is reset to zero, and a new count is started in the following range of time. The number indicated by the totalizator of the counter (block 3) is constantly verified by a detector of emergency conditions (block 4) which, as soon as it reckons that the preset threshold value p has been reached, it issues control signals to the loom stopping device S and to a first warning sign A. In a preferred version of the device, when the threshold value p. has been reached, the value of the totalizator of the counter (block 3) is suddendly brought to a predetermined full-scale value a of the counter, for istance 100 or higher, and the signal presence check (block 2) continues in performing the former functions, i . e . : - if the presence of a signal is detected, the value 1 is added in the counter (block 3), however without exceeding the above said full-scale value ; and - if the absence of the signal is detected, a value 1 is subtracted from the counter. A second warning sign B is issued or, alternatively, the pre-existing warning sign A is modified only when the counter is returned to a zero value. The full-scale value of the counter is in fact determined as high as necessary for obtaining in the corresponding time sampling lenght a complete damping of the oscillations of the drop wires. Any detection of signal absence persisting after the counter has returned to a zero value does therefore undoubtely mean that the true contact firstly detected has changed in a temporary contact, thus correctly signalled by the warning sign B. Preferably, the second warning sign B is in the form of an intermittent signal light. In this case, it can advantageously consist of the same signal light used for the first warning sign A, by changing its working from a continuous one to an intermittent one. When the operator, guided by the aforedescribed indications, has finished repairing any possibly broken or loosened warp yarns and the loom is started again, the electronic control device according to the present invention automatically provides to zero-set the totalizator of the counter (block 3), whereby said device is set in conditions to start again the type of operations described heretofore. In the above description the function in the block 3 has been always described as a counter. This function can be however accomplished as well by any kind of adder device. A time integrator, for istance, could be in fact advantageously used, preferably summing or subtracting to its totalizator, for each sampling cycle, a period of time identical to the sampling period. In this case the full-scale value of the integrator can be directly used, when a true contact of the drop wire has been detected, as a control signal to be sent to the loom stopping device S. From the above description it appears quite evident how the device according to the invention has fully reached its intended objects. It in fact allows to positively discriminate the false contacts, determined by electrostatic phenomena, from the true contacts due to drops, even temporary, of the wires onto the banks. Said device moreover allows, even in the case of temporary contacts, to get a precise indication as to the bank, or bank portion, on which the inconvenience has occurred, making it possible to drastically reduce both the loom stopping times and the operator ' s working times .

Claims: CLAIMS 1) Electronic control device for a warp stop motion device of a loom - of the type comprising: a plurality of side-by-side banks onto each of which there is inserted a plurality of drop wires, kept lifted above the bank by the tension of a respective warp yarn sliding through a hole or slot thereof; means to control the stopping of the loom; and signaling means to indicate the bank, or a zone thereof, onto which a wire has dropped - characterized in that it comprises an electronic circuit, apt to detect the current signals in the electric circuits of each bank of the warp stop motion device, and a processing unit apt to control said electronic circuit and to process the signals issued thereby, discriminating the false contacts, due to electrostatic discharges or other electric transients on the bank, from the true contacts due to the dropping, even temporary, of a drop wire on a bank and, in case of a true contact, stopping the operation of the loom and issuing a first warning sign referring to said bank, or bank portion. 2) Electronic control device as in claim 1), wherein said processing unit, after having reckoned a true contact, further process the relative signal, checking if the true contact is or becomes a temporary contact and issuing, in this last case, a second warning sign. 3) Electronic control device as in claim 1) or 2), wherein said current signal in the electric circuits of each bank of the warp stop motion device are converted into digital signals before sendig the same to said processing unit. 4) Electronic control device as in claim 3), wherein for discriminating the false contacts due to electrostatic discharges or other electric transients on the bank, from the true contacts due to the dropping, even temporary, of a drop wire on a bank, the processing unit performs the following operations on the above said signals: - detecting the presence, or the absence, of the current signal in the electric circuits of each bank or bank portion of the warp stop motion device, with a time sampling; - adding, for each sampling cycle and for each bank or bank portion, a preset value for any sampling cycles in which the presence of the signal has been detected, in an adder device; - subtracting the same preset value, or otherwise cancel all the added values, for any sampling cycles in which the absence of the signal has been detected, from the above said adder device; comparing the total value of said adder device with a predetermined threshold number (n, p) ; and - reckoning as a signal indicating a true contact of the drop wire on the bank the one for which the total value of said adder device has become equal to said threshold number. 5) Electronic control device as in claim 1) wherein, for checking if the reckoned true contact is or becomes a temporary contact the processing unit performs the following operations on the above said signals: - continuosly detecting, with a time sampling, the presence or the absence of the current signal on the electric circuit of the bank, or bank portion, on which the true contact has occurred; - adding, for each sampling cycle and for each bank or bank portion, a preset value for any sampling cycles in which the absence of the signal has been detected, in an adder device; - subtracting the same preset value, or otherwise cancel all the added values, for any sampling cycles in which the presence of the signal has been detected, from the above said adder device; comparing the total value of said adder device with a predetermined threshold number (m, g) ; and - reckoning as a signal indicating a temporary contact of the drop wire on the bank the one for which the total value of said adder device has become equal to said threshold number. 6) Electronic control device as in claim 1), wherein said first warning sign consists of a continuous signal light, apt to locate the bank or bank portion on which the true contact has occurred. 7) Electronic control device as in claim 2), wherein said second warning sign consists of an intermittent signal light. 8) Electronic control device as in any one of the preceding claims, wherein said adder device is a counter and said preset value is a number equal to 1. 9) Electronic control device as in any one of the preceding claims, wherein said adder device is an integrator and said preset value is a time equal to the sampling period. 10) Electronic control device as in claim 6) and 7), wherein said intermittent signal light is associated to, or replaces, said continuous signal light. 11) Electronic control device as in any one of the preceding claims, wherein said time sampling has a sampling lenght of the order of microseconds and a sampling period of the order of tenths of millisecond. 12) Electronic control device as in any one of the preceding claims, wherein said threshold number n is between 2 and 20, and preferably between 3 and 10. 13 ) Electronic control device as in any one of the preceding claims, wherein said threshold number m is higher than, or equal to 0. 14) Electronic control device as in any one of the preceding claims, wherein said threshold number p is between 0 and 15, and preferably between 2 and 12. 15 ) Electronic control device as in any one of the preceding claims, wherein said threshold number 3 is higher than, or equal to 100.

Inventors: BERNARDI LUIGI, BERNARDI, LUIGI
Applicants: ACTEX SPA, ACTEX S.P.A.
Application year: 1998
Main classification: D03D
IPC codes: D03D51