MONITORING SYSTEM FOR KNITTING MACHINES

Abstract: The invention relates to a monitoring system for knitting machines, in particular for such machines as are intended for the knitting of hosiery or socks, comprising a number of yarn guards allocated to each yarn intended for infeed into the machine, the guards each being operative, in response to a movement or absence of movement of the yarn, respectively, detected thereby, to generate and output signal to stop the machine in the event of, for example, yarn or thread breakage or other fault in the yarn infeed, by the intermediary of preferably electronic control unit connected to the yarn guards. The invention is primarily characterised in that the control unit includes memory and comparison means and is, in such instance, arranged to gather and memories, during an introductory, correct and approved working or report cycle of the machine, information representing the yarn infeed phase in the form of the actual pattern of output signals from the yarn guards. The control unit is further arranged thereafter to compare, during subsequent working or report cycles of the machine, the pattern of output signals thus registered and memorised during the introductory, correct and approved working or report cycle with the actual pattern of output signals registered during the current, subsequent working or report cycle in order, in the event of a discrepancy therebetween, to generate a fault signal for stopping the machine.

Description: Monitoring system for knitting machines The present invention relates to a monitoring system for knitting machines, in particular for such machines as are intended for the knitting of hosiery or socks, comprising a number of yarn or thread guards associated with. each yarn intended for infeed into the machine, the guards each being operative, in response to a movement or absence of movement of the yarn, respetively, detected thereby, to generate an output signal to stop the machine in the event of, for example, yarn or thread breakage or other fault in the yarn infeed, by the intermediary of a preferably electronic cont¬ rol unit connected to the yarn guards. In certain types of knitting machines such as, for example, automatic hosiery and sock knitting machines, one or more yarns are knitted in parallel in one or more systems and with variable speeds, according to the design and form of the sock. Thus, for example, reinforcements or replacement of yarn type may occur in the gusset rib, heel and toe por¬ tions of the sock. To this end, the machines are equipped with a program mechanism, of mechanical, pneumatic or elect¬ romechanical type, for controlling yarn carriers with scis¬ sors etc. In order, in an efficient manner, to keep the yarn ends under control on non-working yarns, as well as to take care of any possible yarn remnants, the machines are also equip¬ ped with a suction system. In yarn breakage, for example because the strength of the yarn, weak portions or defective knots have failed to cope with stitch, loop or rib formation, the majority of such breakages takes place in the stitch formation region proper. Normally, the knock-off devices, which sense the presence of a yarn or thread and are included as standard equipment in all machines, are incapable of detecting this fault, since the yarn, because of the action of the suction system, is still held under sufficient tension. If only one yarn or unopened needle latches and, this notwithstanding, stop the machine. However, when several yarns are used in parallel in the same system, it is not possible to detect the fault in this manner, nor is it possible on modern machines with positively controlled needles of the compound type. It is even more difficult to detect the loss of a laid-in yarn, for example, a plush yarn in a sports sock, since the loop formation of the basic yarn is still taking place. As a result, the machine may operate for a considerable time and produce a large number of defective products before the fault is discovered. In order to solve this problem, it is known in the art to employ conventional motion-sensing yarn or thread guards. However, these must be synchronised with the choice of yarn in the machine. By mounting additional sensors, for example micro-switches, on■the yarn carriers or their selector mec¬ hanisms, this is possible on many machine makes and machine models, while, on other models this is impossible because of lack of space. Such a solution also requires high quality switches which can cope with the extremely dusty and oily environment and, at the same time, not present an obstacle to operation and service of the main machine. There is a large number of variations of machine make and machine model, and the installation time for wiring is considerable. The design and spares storage for all of these variations are also costly items. This problem is solved according to the present invention in that said control unit includes memory and comparison means and is, in such instance, arranged to gather and memo¬ rise, during an introductory, correct and approved working or report cycle of the machine, information representing the yarn infeed phase in the form of the actual pattern of out¬ put signals from said yarn guards, and is further arranged thereafter to compare, during subsequent working or report cycles of the machine, the pattern of output signals thus registered and memorised during the introductory, correct and approved working or report cycle with the actual pattern working or report cycle in order, in the event of a discre¬ pancy therebetween, to generate a fault signal for stopping the machine. Said control unit is operative to collect or register the information representing the yarn- infeed phase in the form of the pattern of output signals from the yarn guards on the occurrrence of a pulse which is generated once per machine revolution by a signal emitter similarly connec¬ ted to the control unit. A further signal emitter, similarly connected to the control unit and being operative to genera¬ te and deliver to the control unit a pulse on the start of each reporting cycle in the machine. Primarily, the system according to the present invention is characterised in that the above-mentioned motion sensing yarn guard itself is used as a sensor in order, during a registration cycle, to build up a memory bank against which subsequent working cycles may operate. In the event of a discrepancy between the actual pattern of output signals from the above-mentioned sensor and the correct pattern of the output signals registered and memorised during the registration cycle, the system will generate a stop signal to the machine in question. The system according to the present invention essentially comprises the following components: - emitter (sensor) for registering yarn motion or absence of yarn motion; - central unit with memory function; - emitters for generating one pulse per machine revolution; - emitters for generating one pulse on each report start. The operational mode in the system according to the present invention proceeds such that the machine is set at a new working cycle with the stop function of the system de-acti¬ vated. This entails but a minor drawback, since the machine is still constantly monitored manually at this stage and with ordinary stop functions. After approval of the working cycle, a registration button on the central unit is depres¬ start pulse (report start pulse). Those emitters (sensors) which detect running yarn on the occurrence of each revolu¬ tion pulse are then registered and memorised in the central unit, this procedure continuing until such time as the next report start pulse occurs. By such means, a memory bank is created in the central unit in the form of a pattern of the yarn consumption or yarn motion sequence during one machine or report cycle. Hereafter, the system is arranged such that the stop func¬ tion automatically becomes operative in the event of a discrepancy between the actually registered pattern of out¬ put signals from the yarn motion sensors on each revolution pulse and the norm values of sensor signal patterns on each revolution pulse which were memorised in the memory bank of the central unit during the registration cycle. On the occurrence of faults, when the machine is run to the next report start by a so-called short cycle procedure, the¬ re is a reset button on the central unit which disconnects the stop function until the next report start pulse occurs. The advantages inherent in the system according to the pre¬ sent invention are obvious to the skilled reader: - installation is considerably facilitated in that only motion sensors, pulse emitters and central unit need by installed, in standardised design for all machine types; - no adapation of sensors to machine type is required; - in operational terms, reliability is improved in that fewer elements and parts are employed as compared with prior art systems; - for the same reason, accessibility is greatly improved for the machine operator; - all previously known machine types can be served. An embodiment of the present invention will be described in greater detail below with reference to the accompanying dra¬ wings. Fig 1 is a flow diagram of one physical application of the present invention. Fig 2 is a block diagram of one embodi¬ ment for carrying out the practical application according to fig l. The embodiment of the present invention, as illustrated on the drawings, may be applied on a machine for knitting of different types of products, for instance stockings or socks. Each one of the included threads is allocated an emitter which is operative to emit an electric signal on thread movement. Furthermore, the machine is provided with an emitter which is operative to generate an electric signal or flag pulse (designated "FLAG" in figs 1 and 2) and which defines a thread movement sensing period during one machine revolution, which may also be designated a pattern stage or knitting revolution. The term machine revolution may also be taken to refer to a machine cycle. The products which is to be knitted consists of a number of knitting cycles or pat¬ tern stages which together form the product and its pattern. The machine also includes an emitter which is operative to generate an electric signal or sync-pulse ("SYNC" in figs 1 and 2) on the commencement of each products, and thereby on the initiation of a new pattern. The electronic coupling diagram illustrated in fig 2 is, in principle, self-evident to a person skilled in the art and makes it possible for the skilled reader of this specifica¬ tion to reduce into practice an apparatus for monitoring the manufacture of stockings or socks in a knitting machine. Hence, fig 2 shows the hardware section, while fig 1 illust¬ rates the software section or a flow diagram for the softwa¬ re section, which is also easy to reduce into practice according to generally accepted methods for a person skilled in this art. The hardware section according to fig 2 includes a number of integrated circuits 1-11 which are all currently available on the market. The integrated circuit IC3 is a micro-com¬ tains the program requisite for the function of the circuit. The integrated circuit IC8 is a registration or memorization circuit. The integrated circuit IC10 is an AD converter, while the integrated circuit IC2 is both an input and output circuit. The integrated circuit IC7 is a battery back-up circuit for the registration circuit IC8, while the integra¬ ted circuit subunits IC4, IC5 and IC6 form decoder units. Otherwise, the symbols in the coupling diagram are of the generally accepted type. A switch Si is connected to the input and output circuit IC2 for switching the apparatus to and from a learn mode or learn phase. Furthermore, there is connected, to the circuit IC2, a reset button "RESET", which, after actuation, always entails resetting of the electronic circuits and the program to the initial position. There is further coupled-in a sensor circuit "SENS" which receives a flag pulse which determines that period of time during which thread movement is to be sensed in each pattern stage or machine revolution. Moreover, a circuit unit "SYNC" is coupled to the input and output circuit IC2 for entry of a sync-pulse on commencement of each product. There are further connected to the input and output circuit IC2 a num¬ ber of light emitting diodes (LEDs) LD1-LD4 for indicating the presence of a flag pulse, sync-pulse, check total CHK and learn mode, respectively. There are further coupled to the input and output circuit IC2 two relays RE1 and RE2. On the occurrence of a signal triggering an alarm and/or stop function, the relay RE1 entrains the lighting of an indica¬ tion lamp or other type of signal emitter, while the relay RE2 entails stop of the machine. All thread movement signal emitters are of the current emit¬ ter type and are installed on the machine on per se known way to be actuated by the threads at least when they are moving, are coupled in parallell and to the AD converter IC10 via the connection points 9P14, 2P14 and 10P14. The more threads there are in movement on each sensing, the greater will be the signal to the AD converter, and the les¬ ser will be the digital signal departing from the AD conver¬ ter, which digital signal may have a value from 0 to 255. the integrated circuit IC11 and the potentiometer PI and is supplied by the circuit connected to the connection point 1P14. Taking the flow diagram in fig 1 as the point of departure, the operational mode of the above-described circuitry will be described. Apart from the major flow from "START" to "STOP", or the next pattern stage, there is also an "INTER¬ RUPT" flow which is made operative on the intentional desire for a learn phase which is initiated on every second depres¬ sion of the current switch or switch SI in fig 2. How the learn phase proceeds is apparent in the major flow. When current has been turned on and a number of initial coupling checks have been executed, the apparatus waits for a sync- pulse, which is the start pulse proper. As soon as a cync-pulse occurs, it is ascertained that the pattern stage 0 has been introduced. On condition that the check total is correct, it is queried whether there is to be carried out a learn phase or a normal sensing phase. Prior to the commencement o£ a completely new product, for example a sock, a learn phase must, naturally, always be carried out, in which the light emitting diode LD4 is lit. Irrespec¬ tive of whether the apparatus is in its learn mode or sen¬ sing mode, during which latter the light emitting diode LD4 is extinguished, the apparatus awaits a flag pulse which entails that pattern stage 1 has been commenced and CLR cleared, the registration circuit or memory circuit IC8 (the computer circuits) are zeriozed. As long as there is a flag pulse, the signal from the AD converter IC10 is read at very short intervals, eg 100 microseconds and these readings are stored or registered in the memory cirucit IC8. When the flag pulse disappears and the pattern stage and machine revolution have been completed, the mean value of the read-offs executed during the pulse flag is calculated and, if the apparatus is in the learn mode (LEARN) , the resultant mean value is registered. If, on the other hand, the appara¬ tus is in the sensing mode, the thus resultant mean value is compared with the value previously memorized during a learn tion. If the difference between the mean value arrived at during the sensing operation does not deviate by more than a certain predetermined number of units from the memorized value, the apparatus passes to the next pattern stage, but if the difference is greater, a signal which triggers an -alarm or stop function is generated, whereby the relays RE1 and RE2 are energized. After the finish of a complete pro- . duct or a complete sock, which is approved after inspection, there will be, in the registration or memory circuit IC8, a signal value for each machine revolution which is, in the sensing mode (SENSE), to be compared with the calculated mean value of the sensed signal on normal running operation. While fig 1 illustrates an automatic switching to the learn mode if the check total is incorrect, it is difficult, in most cases, to carry out an automatic learn mode run. If the check total is incorrect, this should lead to a signal trig¬ gering an alarm and/or stop function. In principle, all learn mode runs must be monitored and the subsequently finished product must be inspected before switching to the sensing mode is executed. After running of a learn phase or learn mode and approval of the thus produced product, the signals for each pattern sta¬ ge are stored in the registration or memory circuit IC8 and the machine may be run for manufacture of identical products for several days, several weeks or several months, without the necessity of implementing a new learn phase. Thus, in every machine revolution there may be included any given number of threads or yarns, and also threads or yarns of different types, since the apparatus senses every machine revoltuion and ascertains whether the thread movements sen¬ sed during the manufacturing operation give a signal in the present machine revolution which had previously been obtai¬ ned with a so-called master sock or the first-manufactured sock, or the sock produced during the learn phase. Since, in every machine revolution, and immense number of sensing ope¬ rations is carried out, and since it is preferably the mean value of all sensin s which is com ared with the reviousl memorized signal, certain deviations in the signal are per¬ mitted without therefore giving rise to machine stop. When reading the appended claims in relation to the above-illustrated practical application of the present invention, the term a plurality of mutually subsequent sig¬ nals will be understood as the signal from one and the same pattern stage in mutually subsequent products, but it may, naturally, just as well relate to signals from several mutually subsequent pattern stages in the same product, whe the pattern stages are alike and the registered signals for each respective pattern stage are substantially alike or do not differ from one another more than by the predetermined number of units permitted between registered signal and sen sed signal, i e the calculated mean value of a number of sensings of one and the same signal. Every working or report cycle may include one or several machine revolutions or all the machine revolutions necessary to obtain a comple¬ te sock or stocking. Further a pattern step may include one or several machine revolutions and a sock or stocking may include one or several pattern steps.

Claims: CLAIMS 1. A monitoring system for knitting machines, in particular for such machines as are intended for the knitting of hosie¬ ry or socks, comprising a number of yarn or thread guards associated with each yarn intended for infeed into the mac¬ hine, the guards each being operative, in response to a movement or absence of movement of the yarn, respetively, detected thereby, to generate an output signal to stop the machine in the event of, for example, yarn or thread breaka¬ ge or ^ other fault in the yarn infeed, by the intermediary of a preferably electronic control unit connected to the yarn guards, characterised in that said control unit includes memory and comparison means and is, in such instance, arranged to gather and memorise, during an introductory, correct and approved working or report cycle of the machine, information representing the yarn infeed phase in the form of the actual pattern of output signals from said yarn guards, and is further arranged thereafter to compare, during subsequent working or report cycles of the machine, the pattern of output signals thus registered and memorised during the introductory, correct and approved working or report cycle with the actual pattern of output signals registered during the current, subsequent working or report cycle in order, in the event of a discrepancy therebetween, to generate a fault signal for stopping the machine. 2. The monitoring system as claimed in claim 1, characteri¬ sed in that said control unit is operative to collect or register the information representing the yarn infeed phase in the form of the pattern of output signals from the yarn guards on the occurrrence of a pulse which is generated once per machine revolution by a signal emitter similarly connec¬ ted to the control unit. 3. The monitoring system as claimed in claim 1 or 2, charac¬ -li¬ the control unit and being operative to generate and deliver to the control unit a pulse on the start of each reporting cycle in the machine.

Inventors: JACOBSSON KURT ARNE GUNNAR, JACOBSSON, KURT, ARNE, GUNNAR
Applicants: IRO AB, AKTIEBOLAGET IRO
Application year: 1988
Main classification: D04B35
IPC codes: D04B35