APPARATUS FOR THE CONTROL OF THE ROTATIONAL SPEED OF A DRIVING UNIT FOR A YARN WINDINGS STORAGE DRUM

Abstract: An apparatus for controlling the rotation speed of a yarn windings storage drum (1) comprises a motor for driving said drum; a scanning device sensitive to the quantity of reserve windings on the drum, whose sensed signals are processed by a signal processing unit. The scanning device comprises a light source (3), whose optical path (33) is guided so as to impact the surface of storage windings wound on said drum, characterized in that it comprises a plurality of light guiding blocks (5) connected with a related light source for guiding a related plurality of light paths (33); and a plurality of sensor means (4) capable of receiving a related light path; said light guiding block (5) and said sensor means (4) being arranged on one side or the other, in a radial direction, of said storage winding drum made at least partially of light transparent portions.

Description: APPARATUS FOR THE CONTROL OF THE ROTATIONAL SPEED OF A DRIVING UNIT FOR A YARN WINDINGS STORAGE DRUM Technical Field The invention relates to an apparatus for the control of the rotational speed of a driving unit for a yarn windings storage drum, as usually in use with devices for storing and delivering yarns in textile machines. Background Art Such an apparatus is particularly useful for machines, which during the progress of the manufacturing process show continuously or even only intermittently an irregular consumption of yarn, as occurs for inst. with knitting or hosiery machines, which In ter ali a knit special patterns of knitwear or rely on jacquard systems, or operate according to stripe patterns, or with shuttle systems or systems which knit plush, said apparatus being also applicable to straight knitting machines or to looms with so-called thread shot. The main object of such an apparatus, which is active in the unwinding of the yarn from a yarn bobbin and in the delivery of such to a related knitting point of a textile machine, is to eliminate the tension differences which practically always appear as a consequence of the fact that the diameter of the bobbin is continuously varied by the yarn unwinding process, for inst. in connection with different yarn speeds, and is further to eliminate or simplify the conventional means for guiding, braking and differently controlling the yarn, which conventional means have a yarn tension increasing effect, thus achieving that the yarn may be delivered to said knitting point in controlled, constant conditions. By inserting such an apparatus in between the yarn bobbin and the knitting point, it is aimed at obtaining principally a uniform knitwear as to length and knitting quality (for inst. the pattern of the stitches) and at obtaining a higher efficiency of the machine as a consequence of less disturbances, for inst. caused by yarn breakings. It is already known in circular knitting machines to rely on the method which provides that all yarns to be processed are supplied through yarn delivery devices, which have additionally the task to stop the machine when a yarn breaking occurs, so as to avoid or at least to strongly limit the damaging of needles and cylinders which otherwise would inevitably occur. The yarn winding serves here as an additional reserve. However the problems in such circular knitting machines are much simpler, at least with the knitting of so-called straight or approximately straight knitwear, if compared with the requirements existing in a comparable apparatus for supplying the yarn in connection with an irregular, i.e. intermittent yarn consumption, as occurs in the textile machines of the kind above mentioned. in such known devices for circular knitting machines, as a consequence of the synchronism between the movement of the machine cylinder and the consumption of the yarn of each single knitting point, it is possible to supply the yarn, through relatively simple mechanical means, in correct quantities. Practically, such yarn supply devices are directly driven, mostly in a synchronous way through a continuously adjustable gear device, which is controlled through a toothed belt or the like by the machine cylinder. For obvious reasons such a yarn supply device is not applicable to textile machines with an intermittent yarn consumption. The sudden variations of the speeds of the yarn which occur with such machines while the cylinder is per se constantly operated cannot be performed by any yarn bobbin of a conventional yarn supplying device. Accordingly, in this complex field so-called storage drums are used, in order to solve the problems which are posed. Of these so-called yarn storage means, there are at least two main forms: one form provides for a yarn storage drum which is intermittently brought to stilstand, which has a rotating winding means which winds up the yarn on the storage drum; the other form provides only for a rotating storage drum, on which the yarn is wound. The common feature of such embodiments is the principle of the winding of the yarn on a storage drum, so as to render ready a sufficiently large reserve of yarn, while sensitive means ascertain in due time when the yarn reserve has to be replenished as a consequence of the unwinding requested by the textile machine. A further common feature is the fact that collector-free three-phase electrical motors are provided for their driving, which do not suffer from wear. This also means that as a difference from conventional yarn supplying devices for circular knitting machines, each yarn storage drum needs - in connection with its own driving - specially devised sensitive means, and furthermore there is a need for complex signal processing means with electronic control, in order to achieve a correct working operation. For easily understandable reasons, the technical effort is thus considerable, if one wants to serve, in a textile machine as for inst. hosiery manufacturing automatic machine, each knitting point individually through a yarn storage means of the above kind. Already the monstrous mechanical construction above all in relation to yarn storage means with winding elements and standstill storage drum with three-phase motors fed by the main voltage render a correct and above all a convenient application practically impossible, even besides the high costs for installation and getting the main voltage, which such devices imply. Known are since a certain time devices for supplying yarns, with yarn storage means of small constructional requirements, such as those disclosed in US. Patent A 3,225,446 or German Patent Bl 1 635 899, however such devices do not offer a real solution in particular for the optimal application in relation to the most differentiated kinds of yarns, as for inst. the thinnest synthetic or natural fiber yarns, which include rubber or elastomer yarns on which synthetic or natural fiber yarns are wound around or the newer economically more convenient fiber whirling versions thereof. However also with conventional standard yarns, difficulties appear. In fact a drawback of the device according to German patent D- PS 1 635 899 resides in the fact that the reserve winding wound on the winding drum requires always a relatively high number of windings, before an oscillation of the arms under the action of the total friction resistance of the reserve winding on the winding drum starts to be operational. On the basis of the high total friction resistance which is needed to trigger the mechanical action and to eventually correctly control the driving of the winding drum, one meets practically always with undesirable over or under bobbining of the single windings in the reserve windings, which does not permit a uniform axial unwinding tension of the yarn. Other disadvantages are seen in the bulky construction, with deleterious inertial consequences; a further disadvantage is seen in the fact that the sensitive means to control the bobbin work on an on/off system, which does not permit a synchronous relationship between the unwinding status and the rewinding operation, etc. A disadvantage of the device according to US Patent 3 225 446 is that the so-called optical electrical control of the reserve quantity is ineffective in practical use, and is biased by any light source, for inst. by daylight, artificial illumination, machine illumination etc. or by volatile floating fiber particles, etc. Other known devices as those taught by German Patent DE 28 49 388 or DE 26 51 857, are also complex and affected by fiber impurities always floating in the related environment. Further known devices are shown in German published Patent applications DE 40 37 575 Al and DE 39 04 807 Al, which all do not offer a simple solution to the problem inasmuch as they rely on massive storage drums, with the related problems of driving with collector-free three- phase motors. In fact, the larger the motor, the slower the reaction, and thus the larger the storage drum, and the reserve winding. Disclosure of the Invention A main object of the invention is to provide control apparatus which permits to substantially reduce the yarn reserve, with beneficial consequences on the largeness of the storage drum and of the number of windings. A further object is to reduce the driving mechanism requirements, with beneficial consequences on the energy consumption. These and further objects of the invention are reached by an apparatus according to the invention as more clearly set forth in claim 1. Brief Description of the Drawings The apparatus according to the invention is more closely disclosed in connection with a number of embodiments thereof, as exemplified in the enclosed drawings, in which: Fig. 1 is a vertical cross section through the storage winding drum, with parts of the control apparatus; Fig. 2 is a lateral view of light source, with a limited radiation angle, Fig. 3 is a lateral view of a further embodiment with a limited radiation angle; Fig. 4 is a vertical cross section through the storage winding drum with a view of the optical window of the light guiding block; Fig. 5 is a horizontal cross section through the storage winding drum, with a view from above on the optical path; Fig. 6 is a horizontal cross section through the storage winding drum, with a view from above on a movable, adjustable light guiding block; Fig. 7 is a horizontal cross section of the storage winding drum, with a view from above of a spring biased, movable light guiding block; Fig. 8 is a vertical cross section of a part of the cylindrical end of the storage winding drum; Fig. 9 is a vertical cross section of a further embodiment of the cylindrical end of the storage drum; Fig. 10 shows the electronic control apparatus and the signal processing device, in diagrammatical representation. Fig. 11 is a vertical cross section of a part of the storage winding drum, whose securing plate activates the yarn with the storage winding and the mechanical disconnecting device. Fig. 12 is a vertical cross section through a part of the device of the storage winding drum, whose securing plate activates the yarn and the mechanical disconnecting device. Ways of carrying out the Invention According to the invention, the apparatus comprises a scanning unit and a signal processing device. The scanning unit comprises a plurality of optical paths 33 generated by a related light source 3. Each of such light sources comprise one or more IR-diodes with a limited radiation angle 6, the light beam of which is directed substantially radially towards the inner side of the storage winding drum 1, which at least on the surface on which the windings 2 rest is transparent to the light. The light sources furthermore comprise a related light sensor 4, which is preferably arranged outside the storage winding drum, as well as a light guiding block 5, which is arranged between the usually available storage winding and the sensor. The task of the light guiding block 5 is to take care - through its light window 9 which is tuned to the maximum width of the storage winding area to be scanned - for the exact optical light conditions (i.e. to exclude stray light, external light, and the like) and above all to keep free the light stroke between the upper surface 2 of the storage winding, which it has to scan, and the sensor 4 from undesirable disturbances, as for inst. floating fibers, paraffin deposits and dust. To this end, the light guiding block 5 is provided with a light non transparent cover 10 or a coating 8, enveloping the block on all sides, except the one permitting the desired light conductive path to progress. It is a principal feature of the invention to mount the light guiding block (5) on a support means which is connected with adjustable means 15 (Fig. 6) or spring means 16, so as to be movable in the direction of the light conductive path. More particularly the movement of the support means is spring biased as shown in Fig. 7. This solves the problem otherwise existing that, independently of the variable thickness of the yarn, it is provided for the light window 9 to be always in physical contact with the upper surface of the storage winding 2, which surface is thus constantly and automatically cleaned as a consequence of the rotation of the storage windings. The apparatus comprises a mechanical disconnecting device, comprising an oscillating lever member 28' (Fig. 11 and 12) articulated in 28, and capable of acting on a contact 31 which may disconnect the machine. In fact, if the apparatus is disconnected, or there is a failure, even an electrical one, in the apparatus, such lever member 28' is brought to oscillate by the action of the yarn 29, guided in guide 30, which yarn loosens itself from the drum 1, bringing the lever member to oscillate and act on contact 31. The drum 1 is provided (Fig. 8 and 9) at the side where the yarn is supplied with a cylindrical end 11, and is supported with at least one side exactly in a recess 12 of the lateral support or securing plate 13, preferably lined with a gasket sleeve member 14, for receiving the driving shaft of the transparent drum in a manner efficiently capable of avoiding of foreign bodies, which can dirty the optical path 33. The electronic circuit is shown in Fig. 10, where the signal processing unit is shown generally by numeral 40. The optical path 33 consists in this example of a light source with two IR-diodes 3, 3' and one sensor 4, in form of a phototransistor. The two IR diodes 3,3' with the two radiation surfaces 6, which are tuned on the maximum width 2 of the storage windings and on the relatedly dimensioned size of the light window 9 of the light guiding block 5, are fed by a common adjustable electrical current source 17. The adjusting means 19 is providing for adjustment and preset of the maximum and the minimum width of the storage winding and the adjustment element 18 provides for the possibility of a continuous adjustment between these two end preset values, so that eventually, in case of empty storage drum even in the event of a displacement of the adjusting element 18 the full preset maximum intensity of the light is coming into play in relation to the sensor 4. This maximum value is inter alia used in order to bring about a disconnection of the machine and simultaneously to activate a error signal device, for inst. in form of a signaling light. According to the kind of yarn to be processed, the adjusting means permits to be adjusted in relation to a width of the windings required for a correct operation of the apparatus (always about ten up to a maximum of fifteen windings). Four to five windings are needed for the so-called positive operation - a safe transport of the yarn through the storage drum - and the remaining windings operate as reserves in order to cope with an abrupt need for yarn. In case of a too small number of windings the danger appears of an abrupt emptying of the bobbin, while with a larger number of windings the danger of an under or over bobbining occurs, with the consequence that the yarn can no more, as instead is desired, be unwound in a uniform manner from the storage drum. It is a particular feature of the invention the fact that, since the yarn windings are wound on the drum without interspace, the intensity of the light impacting the sensor varies always in reverse proportion to the number of present windings. The sensor converts the light intensity each time impacting in a corresponding analog signal (many windings = low intensity = small signal; few windings = high intensity = large signal). Successively to the sensor 4 a signal amplifier and more precisely an impedance converter 20 is connected, which avoids retroactions on the same through the successive signal processing functions. From the same the main signal is led to two comparators 21, 22 and to a transistor 25, which operates like a switch. The comparator 21 compares the level of the main signal with the pre-selected value, which is set through the adjustment of the adjustment member 18', which is positively connected with the adjustment element 18. As already disclosed, the adjusting element 18 presets the effective storage winding width. By means of the simultaneous variation of the nominal (desired) value of the comparator level, for inst. by means of an increase, which occurs in relation to a diminishing of the adjustment related to the storage winding width (which may be desired or required by thinner yarn kinds), a higher level of the main signal is required in order to activate the comparator 21 and thus to bring the switch 25 in its conductive position, so that the main signal reaches the input to the voltage/frequency converter 24. In the practical embodiment it has been found that such a double function is indispensable in the adjustment of the width of the storage winding, since otherwise not all the different yarns existing on the market (which differ in thickness, color, structure, etc.) can be correctly processed. The comparator 22 has the task to survey the level of the main signal and in case a certain preset value is exceeded, which fact occurs when the reserve of windings is empty or almost empty, its trigger means 26 has to trigger a failure signal, for inst. the switching on of a failure indicating lamp and/or a disconnection relay, which may bring about a stilstand of the machine. Simultaneously or with a certain delay, the comparator 22 can, through the timing element 23, disconnect the voltage/frequency converter 24, so that the driving unit of the storage drum does not continue to needless operate. The stopping is reached through the diode 40 and the reactivation of the comparator 22 occurs through the switching of the main switch 27. The voltage/frequency converter 24 generates for inst. a series of impulses required for a stepping motor, within the framework of a conventional here not disclosed motor control electronic system.

Claims: C L I M S 1. Apparatus for controlling the rotation speed of a yarn windings storage drum (1) suitable for use with a yarn delivery device, comprising a motor for driving said drum; a scanning device sensitive to the quantity of reserve windings on the drum, whose sensed signals are processed by a signal processing unit arranged between said scanning device and said signal processing unit, said scanning device comprising a light source (3), whose optical path (33) is guided so as to impact the surface of storage windings wound on said drum, characterized in that it comprises a plurality of light guiding blocks (5) connected with a related light source for guiding a related plurality of light paths (33); and a plurality of sensor means (4) capable of receiving a related light path; said light guiding block (5) and said sensor means (4) being arranged on one side or the other, in a radial direction, of said storage winding drum made at least partially of light transparent portions; said light guiding block being provided with light passage preventing means which prevent the passage of light except through window means facing said transparent portion of said drum, on which drum windings are wound so that contiguous winds form a winding width, which is capable of biasing said related light path before it reaches the related sensor means (4) which derives from such so biased light a signal to be processed by the signal processing unit, thereby controlling said control apparatus. 2. Apparatus according to claim 1, characterized in that the radiation area of said light sources (3) are provided with means which direct on the portion of said drum (1) provided with windings a restricted radiation impact area thereon of preset width. 3. Apparatus according to claim 1, wherein said light passage preventing means are formed of a non transparent cover means (10) which leaves uncoated only said window means. 4. Apparatus according to claim 1, characterized in that said window is arranged in the closest distance relationship to -said windings, so as to bring about a light physical contact. 5. Apparatus according to claims 1 and 4, characterized in that said light guiding block (5) is supported by means (15) movable in the direction of said path. 6. Apparatus according to claim 5, wherein said means comprise spring members (16) to bias said movement. 7. Apparatus according to claim 1, characterized in that the signal processing unit (40) comprises means (18', 21, 25, 24) for adjusting a threshold for starting or stopping the driving of the drum. 8. Apparatus according to claim 7, comprising an element (18) for adjusting of the radiation of the light sources, which are positively connected with a adjusting member (18') for controlling the said apparatus. 9. Apparatus according to claim 1, comprising a disconnecting device including an oscillating disconnection member (28 1 ) arranged to cooperate with the yarn (29), and sensitive to the position the yarn takes up when the apparatus is disconnected or there is a failure in the operation of the apparatus, for inst. because of a failure in the current feeding the apparatus, so as to close in such case a contact (31) and disconnect the machine.

Inventors: FABSCHITZ HEINRICH, FABSCHITZ, HEINRICH
Applicants: FABSCHITZ HEINRICH, FABSCHITZ, HEINRICH
Application year: 1996
Main classification: D04B15
IPC codes: B65H49, B65H51, B65H54, D03D47, D04B15