Yarn Feeder Device

Abstract

The device comprises a sensor (15) for reading the tension of the yarn being fed to the machine and a variable-speed motor-driven yarn feed roller (3). The roller is driven by a microprocessor-controlled unit suitable for adjusting the speed of the roller as a function of the signal coming from said tension sensor. The yarn delivered by the feed roller (3) is wound through approximately 180° onto an idle pulley (13) before it is fed to the textile machine.

Description

This invention relates to a device for feeding yarns to textile machines, such as circular or straight knitting machines, that can be adapted either to machines in which the yarn consumption rate is constant or to machines in which the yarn is knitted discontinuously (it is a well-known fact that said discontinuous yarn consumption induces periodic changes in the yarn's tension that can combine with tension variations due to irregularities in the yarn itself in negatively influencing the quality of the resulting fabric and the continuity of its production).

The device forming the object of this invention can also be used in certain stages of the spinning process, e.g. to feed yarn at a uniform tension to twisting or stranding machines, or the like.

This invention refers to a yarn feeder device comprising a yarn tension sensor and a yarn feed roller around which the yarn is wound to prevent any relative slipping, the roller being motorized by means of a variable-speed motor complete with a rotation sensor and governed by a microprocessor-controlled electronic unit suitable for adjusting the speed of the roller as a function of the signal coming from said tension sensor.

According to this invention, the device comprises a pulley for carrying the yarn, wherein the incoming and outgoing lengths of yarn together form a relatively narrow, or substantially near-zero angle (α). The pulley is suspended from a sensitive element of the tension sensor suitable for transmitting a signal to said feed roller motor control unit that is proportional to the resultant of the forces exerted on the pulley by the yarn, and the control unit has a program resident in its memory for keeping the value of said resultant of the forces (corresponding to the yarn tension) within a pre-established range of yarn tensions by adjusting the speed of the motor, and consequently of the feed roller. The yarn thus brings a force to bear on the tension sensor that is approximately twice the actual tension of the yarn, thereby increasing the sensor's sensitivity by comparison with known feeder devices.

The electronic control unit of the device can also be interfaced with the machine to which the device is attached in order to receive data (e.g. using suitable sensors) and/or instructions from the latter, and to adjust the working tension of the yarn being fed to the machine accordingly, depending on its working program, or it can send the machine information such as the length of yarn delivered in each working stage. The previously-mentioned tension adjustments can be made in steps or continuously, depending on the needs of the garment being made by the machine, and they can be set by means of an operator interface connected to the control unit of the device, such as a personal computer either connected to said control unit or on board the machine itself.

In a first preferred embodiment of the invention, the pulley supporting block comprises a U-shaped bracket housing the pulley, the stud supporting the pulley being attached to the ends of said bracket. The sensor is of the slender cylinder-shaped type and is glued to a flat or concave seat coinciding with the end of the rod, with its axis lying parallel to said rod, said U-shaped bracket resting up against the sensor on the side opposite said seat on the rod.

In a second preferred embodiment, the pulley block bracket is hinged onto one free end of a tab to which a bending sensor is attached, composed for instance of one or more strain gauges.

According to the invention, the tension sensor, and consequently also a stud from which the pulley carrying the yarn is suspended, can be solidly attached to the body of the feeder device, or applied to the free end of a yarn take-up rod. This second solution is particularly suitable when the machine served by the feeder device has a discontinuous yarn consumption rate.

Various structural variants and possible uses of the device according to this invention are described in the dependent claims.

The invention is better explained in the following description and attached drawings, which illustrate a non-restrictive example of the invention in question.

In the drawings:

FIGS. 1 and 2 schematically illustrate an elevational view and a view from above (along II-II of FIG. 1), respectively, of the device according to a first embodiment of the invention;

FIGS. 3 and 4 show partial views from above along III-III and IV-IV of FIG. 1;

FIG. 5 is an enlargement of the detail V in FIG. 1;

FIG. 6 is a cross-section along VI-VI of FIG. 5;

FIG. 7 shows a side view of another form of embodiment of the device according to the invention;

FIG. 8 shows an enlargement of the detail VIII in FIG. 7; and

FIG. 9 shows a view along IX-IX of FIG. 8.

With reference to FIGS. 1 and 2, the device according to the invention has a plate-shaped body 1, to which a variable-speed electric motor (e.g. of the brushless, direct-current type) and a corresponding electronic control unit (not illustrated in the drawing) are attached. On the front of the body 1 illustrated in FIG. 1, the device has a revolving roller 3 mounted co-axially on the output shaft of the motor, a plate-type yarn tensioner 5, a rod 7 swinging around an axis X-X, a rod-returning spring 9, an arched blade serving as a rabbet 10 for the rod 7, and a graduated segment 12 of a circle whose center lies on the axis X-X, suitable for identifying the angular position of the rod 7.

The roller 3 has a cylindrical outer surface suitable for generating a friction with the yarn wound thereon, made of elastomer for instance, or with a hard, rough metal surface layer. The plate-type yarn tensioner comprises a pair of plates 5A, 5B (FIG. 3) kept in contact with each other—on their smooth, wear-proof sides—by a compression spring 5C adjustable by means of a threaded knob 5D. The spring 9 is a traction spring that obliges the rod 7 to turn in the direction of the arrow F1, one end of the spring being attached by means of a screw to the periphery of the hub 7A of the rod, and the other end being fixed by means of another screw to the periphery of a bush 8 attached to the front of the body 1 by means of a swivel screw 8A (FIG. 4). The tension on the spring 9 can be adjusted by loosening the screw 8A, turning the bush 8 one way or the other, and then tightening it again in the required position.

A block 11 is attached to the free end of the rod 7 and comprises an idle pulley 13 with an outer race 13A, and a holder for the pulley substantially composed of a bracket 11A bent into a U shape, with the stud 11B supporting the pulley 13 caulked onto its ends.

The block 11 is kept axially on the rod 7 with some degree of clearance by means of a pair of elastic rings 7B inserted in corresponding grooves (not illustrated) in the rod 7, and rests against the rod 7 with a pressure sensor 15 sandwiched between the two and attached to the rod, e.g. by means of glue, in a cavity 7C in said rod. The pressure sensor 15 is electrically connected to the electronic control unit contained in the body 1, by means of electric wires not illustrated in the drawing.

The above-described device can feed yarn 17 to a textile machine for processing, to produce a knitted fabric for instance. The yarn (coming from a reel that is not illustrated in the drawing) passes through the adjustable yarn tensioner 5, then winds at least one turn around the roller 3 before passing through the race 13A in the pulley 13, which returns it through a yarn guide 19 to deliver it to the machine for processing. The lengths of yarn entering and exiting from the pulley 13 together form a very narrow angle α (e.g. approximately 7° in the example in FIG. 1). Using this arrangement, the tension of the yarn is unloaded onto the sensor 15 with a resultant corresponding to approximately twice its real value.

In working conditions, the tension of the yarn being processed makes the rod 7 turn in the direction opposite the arrow F1 of FIG. 1, overcoming the effect of the spring 9. The force exerted by the spring is adjusted by the operators, who adjust the angular position of the bush 8 so that, with the required tension on the yarn, the rod 7 is positioned at a certain angle with respect to the graduated segment 12, e.g. approximately at the midline thereof. The control unit contained in the body 1 receives a signal from the pressure sensor 15 that is proportional to the tension on the yarn 17; it compares the signal with the required tension previously specified in its resident memory, and then it adjusts the speed of the motor driving the roller 3 so as to keep the tension of the yarn 17 close to the required value. For instance, if the pressure recorded by the sensor 15 corresponds to a tension higher than the required setting, the control unit accelerates the movement of the roller 3; vice versa, it makes the roller turn more slowly if said pressure tends to diminish with respect to the pre-set value.

When the machine upstream calls for more yarn than is currently being delivered by the roller 3, the rod 7 is drawn downwards, even to the point where it comes up against the arched rabbet blade 10. This movement of the rod 7 prevents any excessively rapid increases in the tension of the yarn 17, an action that is prolonged both by the rod 7 bending (thanks to its flexibility) against the rabbet 10 and by the shape of said rabbet 10.

With reference to FIGS. 7 to 9, the following is a description of another particularly preferred embodiment of the invention. As in the case of FIG. 1, the device has a plate-shaped body 201, to which a variable-speed electric motor (e.g. of the brushless, direct-current type) and a corresponding electronic control unit (not illustrated in the drawing) are attached. On the front of the body 201 illustrated in FIG. 7, the device has a revolving roller 203 mounted co-axially on the output shaft of the motor, that is on the opposite side of the plate 201, a plate-type yarn tensioner 205 entirely similar to the one 5 in FIG. 1, a rod 207 swinging around an axis X-X, and a rod-returning device 209.

The take-up rod 207 is obliged to move clockwise (looking at FIG. 7) by a wheel 212 idly supported onto the end of a small rod 214, which is in turn hinged along an axis Y-Y to a saddle 216 sliding on a horizontal guide 217 and attachable thereto, in the preferred position, by means of fixing means that are not illustrated in the drawing. A spiral spring 220, working between the small rod 214 and the saddle 216, obliges said small rod to move clockwise so as to rest against the take-up rod 207, making the latter turn in the same direction. Changing the position of the saddle 216 along the guide 217 induces a variation in the point where the wheel 212 comes to rest along the rod 207, and this consequently enables an accurate adjustment of the return torque brought to bear thereon. The saddle 216 also has an extension 216A, which serves as a rabbet for the rod 207, restricting its downward movement due to the tugging of the yarn.

One end of a tab 221, in the form of a thin, narrow and elongated plate, is welded onto the free end of the rod 207; the upper side of the other end of said tab is welded to a bush 221A for a stud enabling the swinging of a bracket 211, which carries an idle pulley 213, said bracket and pulley being similar and serving the same purposes as the corresponding elements 11 and 13 of FIG. 1. Two strain gauges 215 are attached to the two sides of the tab 221, which are electrically connected, forming a bridge, to the control unit (not illustrated) of the device and serving the same purpose as the sensor 15 of FIG. 1.

Normally, as it moves along, the yarn 17 (FIG. 7) fed by the device encounters the plate-type tensioner 205 first and then, after being diverted by a counter-roller 223 (which is idly hinged onto a lever 225, that is in turn hinged to the plate 201 and held by a spring 227 up against the roller 203), the yarn is wound through approximately 180° onto the motor-driven roller 203 and then passes onto the pulley 213, being diverted by the latter through approximately 180° and exiting from the device through a yarn guide 219 attached to the plate 201.

The device according to this embodiment of the invention is extremely sensitive to the feed tension of the yarn due to the sensor with the two bridging strain gauges 215, so it facilitates the passage of the yarn onto the feed roller 203, where it is wound only through 180°, and it also enables a precise and easy adjustment of the take-up rod 207 returning torque by means of the adjustable saddle 216.

Clearly, the drawing only shows one example, given exclusively as a practical illustration of the invention, which may vary in form and arrangement without departing from the concept underlying said invention. Any use of reference numbers in the attached claims is made exclusively to facilitate the reading of the claims with reference to the description and shall in no way restrict the scope of protection represented by the claims.

Claims

1-19. (canceled)

20: A yarn feeder device for use with textile machines, and particularly for circular or straight knitting machines, or for spinning machines, e.g. twisting or stranding machines, etc., comprising:

a yarn tension sensor; and

a revolving roller, around which the yarn is at least partially wrapped to prevent any relative slipping, the roller being motorized by means of a variable-speed motor provided with a rotation sensor and driven by a microprocessor-controlled electronic unit or other equivalent device for adjusting the speed of the roller as a function of the signal coming from said tension sensor;

wherein said device further includes a pulley carrying the yarn, in which the incoming and outgoing lengths of yarn together form a relatively narrow, substantially near-zero angle, the pulley being suspended from a sensitive element of the tension sensor so as to transmit a proportional signal to said control unit for the motor of the feed roller that is approximately twice the tension of the yarn, the control unit being provided with a program resident in its memory capable of keeping said signal, which corresponds to the tension of the yarn, within a previously-established range of yarn tensions by adjusting the speed of the motor and consequently of the roller.

21: The device as in claim 20, wherein said pulley block comprises a U-shaped bracket for housing the pulley, the stud supporting the pulley being attached to the ends of said bracket, and wherein said sensor is of the slender cylinder-shaped type and is glued to a flat or hollow seat at the end of the rod, with its axis lying parallel to said rod, said U-shaped bracket resting up against the sensor on the side opposite said seat in the rod.

22: The device as in claim 20, wherein the U-shaped bracket is held axially with respect to the rod by means of elastic rings inserted in corresponding grooves in the rod or in the stud, and arranged on opposite sides of the bracket.

23: The device as in claim 21, wherein the U-shaped bracket is held axially with respect to the rod by means of elastic rings inserted in corresponding grooves in the rod or in the stud, and arranged on opposite sides of the bracket.

24: The device as in claim 20, wherein said sensitive element of the sensor comprises a tab in the shape of a thin, narrow, elongated plate on one free end of which a bush is welded, that is engaged or hinged to a pulley block comprising a bracket that carries the idle pulley, with at least one strain gauge attached to at least one of the two sides of the tab, electrically connected to the control unit of the device and acting as the tension sensor.

25: The device as in claim 24, wherein respective strain gauges are attached to the upper and under-sides of the tab and said strain gauges are connected to form an extensometric bridge with said control unit.

26: The device as in claim 20, wherein said sensitive element for the tension sensor is fixed to the body of the device.

27: The device as in claim 20, wherein said sensitive element for the tension sensor is fixed to the free end of a yarn take-up rod.

28: The device as in claim 27, wherein said rod is flexible so that, when it is drawn down by the yarn against a rabbet that restricts its movement, the rod opposes a gradually increasing resistance to the yarn to absorb the peaks in the tension of the yarn.

29: The device as in claim 28, wherein said rabbet is also flexible so as to further absorb the peaks in the tension of the yarn.

30: The device as in claim 28, wherein said rabbet is in the form of an arch so as to oppose an increasing resistance as rod bends, and thus further absorb the peaks in the tension of the yarn.

31: The device as in claim 20, wherein said rabbet is attached to an adjustable saddle that also carries a device suitable for exerting an adjustable return torque on the rod.

32: The device as in claim 31, wherein said device for adjusting the return torque on the take-up rod includes a lever hinged to the saddle, whereon a spring comes to bear, the lever resting, under the influence of said spring, either directly or by means of a wheel, against said take-up rod at a point on the latter that depends on the position where the saddle is attached along the guide.

33: The device as in claim 20, wherein, depending on the signals transmitted by the yarn tension sensor, the control unit of the device enables the operation of the machine to which the device is applied to be controlled: stopping it, for instance, in the event of the yarn breaking; or slowing it down, for instance, in the event of the passage of knots in a yarn clearer, or when the yarn runs out or breaks, in which case the tension sensor registers a lack of tension persisting beyond a given time threshold.

34: The device as in claim 20, wherein, based on the signals transmitted by the yarn tension sensor, the control unit of the device enables weaving parameters to be recorded, such as the actual quantity yarn instantaneously or globally fed to the machine for the preparation of a given quantity of fabric, the total number of stoppages, and so on.

35: The device as in claim 1, wherein the control unit of the device is interfaced with the machine to which the device is attached in order to receive data and/or instructions from said machine and thus adjust the working tension of the yarn being delivered accordingly, depending on a working program of said machine, said adjustments being possible both in stepping or in continuous mode

36: The device as in claim 20, wherein the control unit of the device also includes means for turning a waxing device on or off.

37: The device as in claim 20, wherein the control unit of the device also includes means for changing the turning speed of a variable-speed to suit the turning speed of the feed roller.

38: The device as in claim 20, wherein the motor driving the roller is of the type that can be made to turn in both directions to allow for the use of the device to undo knitted articles by coupling it with a reel-winding device.