Abstract:
A device for the optical analysis, including two-dimensional, of a thread or yarn (F) fed to a textile machine, said device comprising at least one light emitter element ( 3, 4 ) and at least one receiver element ( 5 ), said emitter element ( 3, 4 ) generating a light signal which strikes said thread (F) before being sensed by the receiver element ( 5 ) which, based on this sensing, defines a characteristic of the thread (F) such as its movement or its stoppage, a dimensional defect or another dimensional characteristic, between said light emitter element ( 3, 4 ) and said receiver element ( 5 ), there being interposed light transparent means ( 6 ) which are encountered by the light signal after it has interacted with the thread (F), and which act as a thread guide.

Description:
FIELD OF THE INVENTION 
   The present invention relates to a device for the optical analysis of a thread or yarn in accordance with the introduction to the main claim. In particular, the invention relates to a device for monitoring its count variation and the possible presence of foreign bodies, and for analyzing its profile. 
   BACKGROUND OF THE INVENTION 
   Methods and devices for monitoring threads or yarns are well known, they using various technologies, for example capacitive or optical piezoelectric sensors. 
   Piezoelectric sensor devices, for example that described in EP 0117571, use for example a piezoelectric ceramic combined with a textile ceramic or other element for contact with the thread or yarn, to transmit vibrations, caused by the roughness of the yarn sliding on said element, to the piezoelectric ceramic. The main advantage of this technology is its almost absolute insensitivity to the presence of dirt or yarn residues in contact with the textile ceramic, the yarn itself automatically cleaning the point of contact with the ceramic. 
   However, this technology presents the main drawback of the absolute need for physical contact between the thread or yarn and the textile ceramic with which the piezoelectric ceramic is combined; this prevents monitoring of yarns which, for example, cannot be touched during their monitoring, to prevent undesired friction or rubbing, which could tear the thread or modify a controlled characteristic, such as tension. 
   Another drawback is the sensitivity of the piezoelectric ceramic to the presence of very intense vibrations or noises which by simulating the condition of the thread in its sliding state would prevent the device, in case of yarn breakage, from generating the signal for halting the textile machine. 
   In contrast, capacitive sensor devices measure the capacitance variation of said sensors caused by the variation in their dielectric, including the actual yarn subjected to monitoring. By measuring the variation in said dielectric, the state of movement the thread, its possible count variation, etc. can be measured. The advantage of this technology is the ability to monitor a yarn even without direct contact with it, the presence of dirt or yarn residues only slightly influencing the measurement capacity of said sensors. 
   The main drawback of these devices is however the impossibility of monitoring conductive threads or yarns, such as copper or steel threads or those in which carbon fibres are present; in the same manner, moist yarns or those wetted with water or treated with antistatic or conductive oils cannot be monitored. This is because a conductive thread or yarn or the presence of water would short-circuit the dielectric, hence making it impossible to measure and monitor the yarn. 
   Moreover the capacitive means present high sensitivity to electrical fields or electrostatic discharges, the presence of which could be mistaken for a moving thread condition, which often prevents its correct operation. 
   In contrast, optical sensor devices, see for example that described in EP 0519281, normally use a light transmitter and a receiver, between which the thread or yarn to be monitored is positioned. 
   The main advantage of this technology is the ability to monitor any type of thread or yarn, whether conductive or not, without any contact with it. The disadvantage of the technology is mainly its sensitivity to the formation of dirt and residues left by the monitored yarn on the receiver and/or transmitter. 
   OBJECTS AND SUMMARY OF THE INVENTION 
   An object of the present invention is to provide an optical sensor device which offers all the major advantages of the three different aforedescribed technologies, i.e. monitoring of any type of thread or yarn, whether conductive or not, monitoring achieved without any contact with the thread or yarn if necessary, insensitivity to the formation of dirt or yarn residues, insensitivity to the presence of conductive oils or more simply water, insensitivity to vibration, noise sources, electrical fields, etc. 
   Another object is to provide a device of the stated type which is of simple and economical construction. 
   Another object is to provide a device of the stated type, the form and ergonomics of which enable it to be used in any field of the textile machine sector or other sectors, for example for monitoring machines producing copper coils, motor windings, or oil transformers. 
   Another object is to provide a device of the stated type which also combines within itself the thread guide function necessary for guiding the thread. 
   Another object is to provide an optical device of the stated type in which the area sensitive to variation in the image of the yarn profile and/or position is as large as possible, being much larger than the dimensions of the sensitive areas of the photosensitive element used, and enabling any thread or yarn monitoring application to be satisfied with great flexibility. 
   A further object is to provide a device of the stated type which is sealed and able to operate without problems under very severe applicative conditions. 
   A further object is to provide a device enabling two-dimensional analysis of the monitored thread. 
   These and further objects which will be apparent to the expert of the art are attained by a device in accordance with the accompanying claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be more apparent from the accompanying drawing, which is provided by way of non-limiting example, and in which: 
       FIG. 1  represents schematically a device of the invention showing the spatial position of the transmitter and receiver elements when applying illumination for direct reading of the variation in position and/or image; 
       FIG. 2  represents a different embodiment of the device of the invention showing the spatial position of the transmitter and receiver elements when applying illumination for reading the variation in position and/or image by reflection; 
       FIG. 3  is an exploded perspective view of an embodiment of the device according to the present invention; 
       FIG. 4  is a front perspective view of the device of  FIG. 3  assembled; 
       FIG. 5  is a rear perspective view of the device of  FIG. 3  assembled; and 
       FIG. 6  shows a circuit schematic of the device of  FIG. 1 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   With reference to said figures, a device constructed in accordance with the present invention is indicated overall by  1  and comprises two infrared light transmitter elements  3  and  4  positioned at an angle to each other, and a receiver element  5  which can be a photodiode, phototransistor, a PSD, etc. The transmitter elements  3  and  4  are preferably orientated towards the centre of the receiver element. 
   The device  1  also comprises means  6  transparent to infrared light, such as a textile ceramic for example formed of zirconium, also acting as a thread guide. Within the means  6  there moves, fed to a textile machine (not shown), a thread F the movement of which is to be monitored, in order to halt said machine should the thread break, and prevent the machine from continuing to produce articles (formed from a plurality of threads fed thereto) which would inevitably be imperfect and have to be rejected. 
   The light transparent means act as a thread guide while at the same time preventing dirt or powder from depositing on the receiver element  5  and altering its operability. These means also increase the operability of the receiver element  5  by incrementing in a controlled manner the light beam which strikes them, to increment each striking shadow cone generated by the thread F encountered by the light emitted by the transmitter elements  3  and  4 . 
   The elements  3 ,  4  and  5  are associated with an electronic circuit  100  comprising a microprocessor unit  101  ( FIG. 3 ). The circuit  100  is of known type. 
   It will be assumed that the light transmitter elements  3  and  4  are activated simultaneously: this causes the formation of two separate shadow cones  10  and  11 , relative to the cross-section of the thread F, which strike the receiver element  5 . This generates, in known manner, an electrical signal proportional to the thread cross-section. 
   It will now be assumed that the thread moves within the light transparent means  6  and slides inside the sensitive area of the receiver element  5  or, while maintaining its position, it varies its cross-section (a totally usual occurrence because however perfect the thread or yarn, it still differs at each of its points): this sliding or cross-section variation causes in known manner a variation in the position and/or shape of the shadow cones  10  and  11  striking the receiver element  5 , to cause a variation in the electrical signal generated thereby. This signal is known to be a function of the image and/or position variation of the monitored yarn. 
   Because of the presence of more than one light transmitter element  3 ,  4 , a very large image-sensitive area on the receiver element  5  is obtained, enabling easy and reliable monitoring of a thread or yarn to be achieved independently of the position of the thread F inside this sensitive area, because in whatever position the thread F lies within the light transparent means  6 , the yarn is always encountered by the light emerging from at least one of the elements  3  and  4 , hence the element  5  continuously senses its presence (via its shadow or the sensed light reflection by said element  5 ). 
   The light transparent means  6  also enable the thread to be contained within and if necessary guided into this sensitive area. This element, besides being transparent to IR light, is also of wear resistant material and hence suitable for remaining if necessary in contact with the thread without being damaged. It should be noted that these means can either always be in contact with the thread F or be usually separated from it when fed to a textile machine by unwinding from a suitable support (bobbin), the term “usually” meaning that purely occasional transient contact can occur with the means  6  during this feed. 
   Contact between the thread and said means  6  also results in natural and automatic cleaning of said means, hence as stated making the device  1  insensitive to the formation of dirt or yarn residues: they cannot accumulate because the light transparent means are cleaned by the yarn as it slides. 
   In a variant, the transmitter elements  3 ,  4 , instead of being operated simultaneously, can be operated alternately to obtain a read-off signal as neither shadow cone (for example the cone  10  generated by the transmitter element  4 ) is reduced by the illumination provided by the non-operating transmitter element (in the example, the transmitter element  3 ). This enables a device of even better performance to be obtained, especially if the device  1  is not used simply to analyze the state of movement of the yarn F, but also for other purposes such as analysis and measurement of the yarn count or cross-section. 
   Alternatively, with reference to  FIG. 2  (in which parts equal to those of  FIG. 1  are indicated by the same reference numerals), the device  1  can use two receiver elements  3  and  4 , the transmitted light of which, after passing through the transparent means  6  containing and guiding the yarn, encounters the monitored thread or yarn F and is reflected towards the receiver element  5  (as indicated by the arrows  13  and  14 ). This latter, struck by said light, generates an electrical signal proportional to the light quantity reflected. 
   Again in this case the light transparent means  6  could be activated either simultaneously or alternately. 
   In a simplified version, the device  1  could use only one light emitter,  3  or  4 , or could use a reflection element (mirror type) in a position opposite the transmitter elements  3  and  4  of  FIG. 2 , to obtain a mixed configuration between the solutions proposed in  FIGS. 1 and 2 . 
   In a further more complex variant, the transmitter elements could be more than two in number, for example four or more, to further increase the sensitive area of the receiver element  5 . 
     FIGS. 3 ,  4  and  5  show a possible embodiment of the device  1  in accordance with the teachings of the present invention. In these figures, parts corresponding to those of the already described figures are indicated by the same reference numerals. 
   The figures show the infrared light transmitter elements  3  and  4 , for example KINGBRIGHT type, code No. K3010F3C, and the light transparent means  6 , for example of alumina, zirconium, sapphire or synthetic ceramic, or similar material, which also act as a thread guide; in a more economical form, these means  6  could be of simple plastic, of nylon, polycarbonate or other type, or glass. 
   The light transparent means  6  comprise a body  20  which, in the example, is in the form of an open ring. The body  20  comprises opposing edges  21  and  22  in which recesses  24  are provided to receive shoulders  26  projecting from a portion  27  for supporting parts  28  and  29  of the casing  30  of the device  1 . These parts are to be closed one on the other (see  FIGS. 4 and 5 ) to retain between them the elements  3 ,  4 ,  5  and an electronic circuit  40  connected to these elements. 
   The parts  28  and  29  fit together along the opposing edges  31  and  32 , which are preferably formed (in known manner with projections and corresponding recesses) such as to co-penetrate and enable the parts to be fixed together. Fixing means such as screws or the like (not shown) can also be provided or the connection can be made permanent by glue positioned along the edges  31  and  32  or by ultrasound bonding. 
   A substantially flat support  33  carrying the elements  3 ,  4 ,  5  and the circuit  40  is disposed between the parts  28  and  29 . This support is retained by said parts when they are fixed together. 
   The parts  28 ,  29  and the support  33  have an open portion ( 28 A,  29 A,  33 A respectively) corresponding to the aperture  35  in the body  20  of the light transparent means  6 . In the figures these open portions and said aperture  28 A,  29 A,  33 A and  35  have a substantially circular shape open on one side where they define a corridor  37  for inserting the thread F into the aperture  35  for its monitoring. 
   The body  20  could however be of different shapes or dimensions; instead of an open ring shape to facilitate insertion of the thread F as in the example shown in  FIG. 3 , it could be of closed ring shape if required to contain the rotary movement (ballooning) of a yarn being unwound from a bobbin or if a yarn is to be monitored during a twisting or spiralling process. 
     FIG. 3  shows the receiver element  5 , which can be a position sensor PSD produced by the known firm HAMAMATSU, code No. 7105-05. Two LEDs  43  and  44  (for example red and green) are also shown for indicating a fault or “all OK” respectively. These LEDs are located on arms  45  and  46  of the support  33 , extending from a main portion  33 A of this latter, in positions corresponding with windows  47  and  48  in the part  28  of the casing  30  which, like the part  29 , is preferably formed like the support  33  with regard to said arms. 
   In a position corresponding with the LED  43  there is located an IR light transmitter, for example of SUNLED code No. ZTNI54W type, with a phototransistor receiver  51 , for example of SUNLED code No. ZRMI54W type, located in a position corresponding with the LED  44 ; this transmitter and receiver pair form an optical key or barrier which if interrupted, for example by insertion of the operator&#39;s index finger, momentarily turns off the device. Another interruption of this barrier again turns on the device. This optical key could be advantageously used to reset an alarm signal, or an acceptance signal for the communication address code, etc. 
   Finally,  FIG. 3  shows a feed connector  55  for input and output signals to and from the device  1 ; for example, these signals can be used respectively for serial communication between the device  1  and the electronic control circuit of the textile machine to which the thread F is fed, for the stop signal for said machine if irregularities such as yarn breakage are present, or in the case of irregularities such as a count variation (for example because of knots, entanglements or extraneous fibres); or again, during twisting or when two yarns are combined by winding one yarn (like a spiral) round the other, if count variations are present caused by two or more troughs where the number of twists measured differs from the set parameter. 
   These functions can be activated by the device  1  via its circuit  100  and the unit  101  which can be connected via the connector  55  to the electronic control circuit of the textile machine. 
   The circuit  100  is formed and operates in the following manner. 
   With reference to  FIG. 6 , the electrical schematic of a device formed in accordance with the present invention comprises, in the example, an optical position sensor  110  identified by a known PSD circuit. It is used to intercept the direct ( FIG. 1 ) or reflected ( FIG. 2 ) image, this image consisting of modulation of the infrared light emitted by transmitter elements  3  and  4  defined by photodiodes. These diodes are biased by the biasing current defined by the biasing resistors  111  and  112 . 
   A microprocessor unit (or simply microcontroller)  120  is provided connected to the resistor  111  via its gate  113 . The unit or microcontroller  120  can reduce the value of the current passing through the diode  3 , when the system is under stand-by or low consumption conditions. 
   When the PSD sensor  110  is struck by infrared light based on the image of the monitored thread or yarn, it generates at its output terminals (photodiode anodes) two currents based on the position in which the infrared light image (yarn profile) strikes the PSD optical sensor. 
   These currents polarize resistors  124  and  125 , which enable a potential difference to be generated across the resistors, to enable voltage signals VA and VB to be emitted at the outputs  122  and  123  of the sensor  110 . 
   A two stage amplifier circuit  126 , formed from operational amplifiers  127  and  128  and relative biasing networks comprising resistors and capacitors  130 ,  131 ,  132 ,  133 ,  134 ,  135 ,  136  and  137 , receives the signals VA and VB. The circuit  126  presents a reference signal obtained from the resistors  140  and  141  and from a filter capacitor  142 ; this circuit arrangement enables a differential amplifier to be formed able to amplify the potential differences present across the already described resistors  124  and  125 , i.e. the signals VA and VB leaving the sensor  110 . 
   The circuit  126  generates suitably amplified signals leaving the two stage amplifier and directed to the gates  150  and  151  of the unit  120 . These amplified signals, for example equal to 1000 and respectively 100 times the image variation level sensed at the inputs of said two stage differential amplifier, result in a device with a double control scale. 
   The amplified signals present at the gates  150  and  151  of the microcontroller  120  are converted in known manner from analog signals to digital signals by the ADC unit forming part of said unit  120 . 
   Said conversion enables the previously amplified signals to be converted into numerical values which are a function of the image relative to the monitored yarn; by means of a processing algorithm they are able to define whether the image variation has values in terms of levels and frequencies which are equal to or greater than the programmed minimum reference value. 
   If the image variation level and frequency values are less than the programmed reference value for an abnormality time exceeding a programmable “alarm time” value, an alarm signal is generated leaving the gate  150  of the unit or microcontroller  120 . This signal is fed to a protection/alarm block  149 . 
   By way of biasing resistors  160  and  161  the signal from said gate  153  operates the output transistor  162 , which activates a (current) alarm signal present at the (STOP) input  163  of the connector. 
   A resistor  165  is used as a shunt resistor to enable the current operated by the transistor  162  to be measured, the voltage drop across the resistor being a function of the current generated by the transistor. 
   This voltage drop is measured by the unit  120  via the gate  168  connected via a decoupling resistor  170  to the resistor  165 . This protects the STOP output of the device  1  against short-circuits: in this respect, in the case of high current exceeding the defined maximum value, the unit  120  deactivates the transistor  162  to protect it. 
   A diode  170 , connected in parallel with the transistor  162 , also acts as protection against voltage inversions between the collector and emitter of said transistor  162 . 
   Via the respective biasing resistors  171  and  172  connected to the respective outputs  175  and  176  of the unit  120 , the LEDs  43  and  44  enable abnormalities of the device  1  to be indicated; an activated green light LED  43  indicates “all OK” whereas an activated red light LED  44  indicates an abnormality in the intercepted yarn. These LEDs  43  and  44  and their related resistors form an abnormality sensing block  180  for the device  1 . 
   The device  1  can be connected to a programming/communication unit for programming parameters relating to image variation level limits and relative alarm times, which if exceeded cause the device to activate the STOP output and the red alarm LED. 
   Said communication takes place via a suitable input and an appropriate output of the unit  120  interfaced with the connector  55  via an input decoupling resistor  185  and an output buffer  186  respectively. 
   A power circuit  190  is also present, formed by known L-C low pass filters  191  and  192 , by a protection diode against feed polarity inversion  193 , and by stabilizer circuits  196  and  197 . The first stabilizer has relative biasing components  200  and  201  and a filter  202 , the values of which predetermine the stabilized output voltage of the stabilizer  196 , identified by VCC 5  and fixed at 5V. The second stabilizer  197 , pertaining to a second power stage at 3.3V, comprises anti-disturbance filters consisting of capacitors  206  and  207 . 
   A power reset circuit  209  is also provided consisting of a stabilizer  210  connected to a resistor  211  connected to a gate  213  of the unit  120 , by which this latter obtains correct data control and saving in case of network abnormalities or holes. 
   Finally, the circuit  100  comprises the photodiode transmitter  49  (biased by the resistor  230  and piloted by the unit  120  via the gate  231 ) and phototransistor receiver  51  with relative biasing resistor  232 ; as stated, these form an optical key interruption barrier, the activation state of which can be read by the unit by reading the relative input at the gate  113 . This optical key can be used for example as a RESET key for the yarn monitoring device of the invention.