Storage yarn feeder with rotary drum and yarn-unwinding sensor

Abstract

 A motorized, yarn-winding rotary drum (12) rotatably supported with respect to a motor-housing (16) is adapted to have a plurality of yarn loops (Y) wound on itself, which are adapted to be unwound upon request from a downstream machine. A yarn-unwinding sensor counts the yarn loops unwinding from the rotary drum (12) and comprises light-emitting means (42) and light-receiving means (44), both integral with the motor-housing (16), one of which has an annular configuration operatively facing an annular surface (30a) of the rotary drum (12) from which the yarn is unwound. Light-guiding means (66) integral with the rotary drum (12) guide the light from the light-emitting means (42) to the light-receiving means (44) through a light passage (30c) defined on the annular surface (30a). The unwinding of yarn from the rotary drum (12) is determined on the basis of the light dimming resulting from the yarn transiting on the light passage (30c).

Description

[0001] The present invention relates to a storage yarn feeder with rotary drum and yarn-unwinding sensor.

[0002] As known, in a textile process the yarn may be fed to a textile machine, e.g., a circular knitting machine, by a plurality of so-called "storage" yarn feeders. A storage yarn feeder is generally provided with a drum which has a plurality of yarn loops wound thereon which are adapted to be unwound upon request from a dowstream machine. As the yarn is unwound from the drum, it may be re-loaded either by a motorized swivel arm which rotates about an axis coaxial with the axis of the drum, or, in the case of feeders as considered herein, by driving the drum to rotate, which drum, in this case, must be motorized.

[0003] As well known to the person skilled in the art, it is very important to maintain the amount of yarn stored on the drum substantially constant on an optimal level, in order to stabilize the tension of the yarn delivered by the feeder. In fact, a reduction of the stock below the optimal level would cause the yarn tension to rise eccessively, resulting in defects in the finished product. On the contrary, a growth of the stock above the optimal level would cause the yarn to accumulate at the delivery end of the drum, with the yarn loops overlapping unevenly and consequent anomalies in the feeding process.

[0004] In EP 2 592 032, the rotation of the motor is controlled in such a way as to maintain the amount of yarn substantially constant with respect to a predetermined amount which is wound on the drum during an initial loading procedure. The feeder is provided with a sensor which is arranged at the delivery end of the drum and is provided with three, or even more, stationary photoelectric cells which are spaced at equal angles about the axis of the drum for detecting the unwinding yarn. Based on the sequence of activation of the photoelectric cells, the control unit determinates wether the yarn is wound or unwound and controls the motor in such a way that, in a steady-state, the amount of yarn wound is equal to the amount of yarn unwound, so that the sensor does not detect any yarn unwinding. Therefore, in a steady-state, an outer observer will see the yarn substantially rotationally motionless, because the winding speed in one direction is equal to the unwinding speed in the opposite direction.

[0005] Consequently, with the system described in EP 2 592 032, the sensor is not capable, per se, of providing an absolute binary information about the amount of yarn which is unwound from the drum, but only a relative information based on the amount of yarn which is wound.

[0006] It is a main object of the present invention to provide a storage yarn feeder having a rotary drum with a yarn-unwinding sensor which is capable, per se, of providing an accurate, reliable absolute information about the amount of yarn which is unwound from the drum in any steady/transient state.

[0007] The above object and other advantages, which will better appear from the following description, are achieved by a yarn feeder having the features recited in claim 1, while the dependent claims state other advantageous, though secondary, features of the invention.

[0008] The invention will be now described in more detail, with reference to a few preferred, non-exclusive embodiments shown by way of non-limiting example in the attached drawings, wherein:

Fig. 1 is a perspective view showing a yarn feeder provided with a yarn-unwinding sensor according to a first embodiment of the invention;

Fig. 2 is a view in axial cross-section of the yarn feeder of Fig. 1;

Fig. 3 is a perspective view showing a component of the yarn-unwinding sensor of Fig. 1;

Fig. 4 is a view in axial cross-section of the component of Fig. 3;

Fig. 5 is a view in cross-section of Fig. 4 made along line V-V;

Fig. 6 shows a first detail of Fig. 2 to an enlarged scale;

Fig. 7 shows a second detail of Fig. 2 to an enlarged scale;

Fig. 8 diagrammatically shows the yarn-unwinding sensor according to a first alternative embodiment of the invention;

Fig. 9 is a view similar to Fig. 2, which shows the yarn-unwinding sensor according to a second alternative embodiment of the invention;

Fig. 10 is a perspective view showing a component of the yarn-unwinding sensor of Fig. 9;

Fig. 11 shows a first detail of Fig. 9 to an enlarged scale;

Fig. 12 shows a second detail of Fig. 9 to an enlarged scale.

[0009] With reference to the above Figures, a storage yarn feeder 10 comprises a yarn-winding drum 12 having a plurality of loops of yarn Y wound thereon, which form a stock S and are adapted to be unwound upon request from a general downstream machine (not shown). As the yarn is unwound from drum 12, the latter is driven to rotate by a motor 14 to draw fresh yarn from a reel (not shown) and wind it upon itself in the form of new loops.

[0010] As shown in Fig. 2, motor 14 is received in a motor-housing 16 of feeder 10, and comprises an annular stator 18 fixed within motor-housing 16, and a rotor 20 which is inserted into annular stator 18 and is fitted to a hollow driving shaft 22. Hollow driving shaft 22 is supported within motor-housing 16 by a pair of rolling bearings 24, 26 and projects outside of motor-housing 16 with a projection 22a, which has drum 12 keyed thereto.

[0011] Drum 12 incorporates a loop-separing device 28, which is adapted to maintain the loops on drum 12 spaced from each other in the longitudinal direction. Loop-separing device 28 is known per se and, therefore, will not be discussed in more detail herein.

[0012] The delivery end of drum 12 is closed by a cover 30. The outer surface of cover 30 has an annular surface, in particular, a cylindrical surface 30a, from which the yarn is unwound, as well as a rounded delivery edge 30b.

[0013] Feeder 10 is also provided with a braking device 32 known per se, which is supported by an arm 33 projecting from motor-housing 16 parallel to the axis of drum 12.

[0014] Braking device 32 comprises a hollow, frustoconical braking member 34 which is biased by elastic means 36 to coaxially abut with its inner surface against rounded delivery edge 30b of cover 30, in order to apply a static braking action by friction upon the unwinding yarn. The braking action is manually adjustable by a knob 38 which controls adjusting means 39 incorporated in arm 33, which are also known per se and therefore are not disclosed in detail herein.

[0015] Yarn Y coming out from the feeder is guided by a yarn-guide eyelet O which is also supported by arm 33.

[0016] A control unit is programmed to drive motor 14 in such a way as to stabilize the stock on drum 12 on a predetermined optimal level. In particular, the stock of yarn is determined on the basis of the number of loops which are unwound from drum 12 and the number of loops which are wound on it.

[0017] The number of loops which are wound on drum 12 can be calculated on the basis of either the speed of rotation or the position of motor 14, in a way known per se.

[0018] For the detection of the unwinding loops, yarn feeer 10 is provided with a sensor 40 which comprises light-emitting means 42 and light-receiving means 44 both integral with motor-housing 16, one of which has an annular configuration operatively facing cylindrical surface 30a of the drum, as well as light-guiding means integral with drum 12, which are arranged to guide the light from light-emitting means 42 to light-receiving means 44 through a light passage 30c defined on cylindrical surface 30a; accordingly, the unwinding of one loop from drum 12 is determined on the basis of the light dimming resulting from the yarn transiting above light passage 30c.

[0019] In a first embodiment of the invention, as shown in Figs. 1-7, light-emitting means 42 have the above annular configuration to generate an annular light beam which radially and continuously invests the whole periphery of cylindrical surface 30a.

[0020] In particular, light-emitting means 42 comprise a light source, which advantageously consists of an infrared light emitting diode 46 which is operatively connected to a first circuit board 48 of the control unit incorporated in arm 33. Emitting diode 46 is arranged so that it emits a linear, infrared light beam in the radial direction towards drum 12. An annular light-guide 50 arranged between drum 12 and emitting diode 46 is sandwiched between two annular supports 51 a, 51 b attached to arm 33.

[0021] Annular light guide 50, which is separately shown in Figs. 3 and 4, has a light propagation annular portion 52 and a light insertion tangential portion 54 that tangentially projects from annular portion 52 and terminates with an inlet surface 56 facing emitting diode 46.

[0022] The linear, infrared light beam generated by emitting diode 46 hitting inlet surface 56 is channeled, via tangential projection 54, into annular portion 52, wherein it propagates by total inner reflection.

[0023] Annular portion 52 has a substantially L-shaped cross-sectional profile (Fig. 4). An outer edge 58 defined between the two branches of the L-shape is slanting at an angle of 45°. As shown in detail in Fig. 5, an annular surface 59, which axially delimits annular portion 52 on the side facing away from outer edge 58, is shaped in such a way as to reflect the light propagating within annular portion 52 into a longitudinal direction towards outer edge 58 (Fig. 5). Advantageously, annular surface 59 is knurled with triangular profiles. Chamfered edge 58 reflects the light inwards by 90° in the radial direction (Fig. 4). Accordingly, a continuous, annular beam of infrared light is generated projecting from an inner cylindrical edge 60 of annular light-guide 50 and investing cylindrical surface 30a.

[0024] Annular light-guide 50 is preferably made of a transparent material such as polycarbonate, PMMA, and the like.

[0025] Having now particular reference to Figs. 6 and 7, with this embodiment the light-guiding means comprise an optical device 62, which is incorporated in cover 30 and is adapted to focus the light from annular light-guide 50 towards an inlet end 64 of an optical fiber cable 66. Optical fiber cable 66 is received within hollow driving shaft 22 and its projection 22a, and has its opposite end, or outlet end 68, attached to the rear end of hollow driving shaft 22 (i.e., the end facing away from projection 22a) via a clamp 70. Outlet end 68 of optical fiber cable 66 faces light-receiving means 44, which, in the embodiment described herein, advantageously comprise an infrared light receiving diode 72 operatively connected to a second circuit board 74 of the control unit which is received within motor-housing 16.

[0026] Optical device 62 comprises a cylindrical shell 76 which is coaxially received within a radial cylindrical seat 78 of cover 30, which is open on cylindrical surface 30a to define the above light passage 30c. The inner end of cylindrical shell 76 is closed by an axially holed nut 80, into which inlet end 64 of optical fiber cable 66 is inserted. A spherical lens 82 housed within cylindrical shell 76 is sandwiched between nut 80 and an inner annular abutment 84 of cylindrical shell 76. Inner annular abutment 84 internally defines a calibrated hole 85 adapted to diaphragm the infrared light beam coming out from annular light-guide 50. The diaphragmed light beam is focused towards the inlet end 64 of optical fiber cable 66 by spherical lens 82. The axial end of cylindrical shell 76 leading to light passage 30c is closed by a disc-shaped window 86 of a transparent material, e.g., glass, arranged at the same level of cylindrical surface 30a. Cylindrical shell 76 is retained by a grub screw 87 which is screwed into cover 30.

[0027] In operation, as shown in Fig. 1, each time one loop of yarn is unwound from drum 12, the yarn transits on light passage 32c, thereby dimming the infrared light beam generated by emitting diode 46. The control unit detects the interruption of light and consequently counts one loop of yarn unwinding.

[0028] It is easily understood that the sensor according to the invention allows the number of unwinding yarns to be counted in absolute terms, regardless of the speed of rotation of the drum, rather that in relative terms with respect to the number of loops which are wound on the drum, as it occurs with the prior art discussed at the beginning of the present disclosure.

[0029] Fig. 8 diagrammatically shows an alternative embodiment of the invention. In this embodiment, the light-guiding means, which in the previous embodiment included optical fiber cable 66, are replaced by a mirror 166 incorporated in the drum (not shown in Fig. 7) and slanting at an angle of 45° with respect to the axis of the drum. The infrared light beam generated by emitting diode 146 is first converted into an annular light beam by annular light-guide 150, then again into a rectilinear light beam by an optical device 162 integral with the drum, is reflected by 90° by mirror 166 and finally hits receiving diode 172. Other conventional optical devices 190, 192, which are adapted to maintain the light beam sufficiently thin, may be provided between annular light-guide 150 and mirror 166 and between mirror 166 and receiving diode 172 respectively.

[0030] Figs. 9-12 show a further embodiment of the invention, in which the light-guiding means are arranged in such a way as to project a rectilinear, outward light beam through the light passage, while the light-receiving means have the above annular configuration for receiving the light beam. Description of the elements similar to the previous embodiment will not be repeated.

[0031] With this embodiment, the light-emitting means comprise an infrared light emitting diode 246 arranged in front of the rear end of driving shaft 222 and operatively connected to circuit board 247 housed within motor-housing 216 of feeder 210 (Figs. 9 and 11).

[0032] Light-receiving means 244 comprise a series of receiving diodes 272 mounted on an annular circuit board 273 (Fig. 10) at equally-spaced angular positions. Annular circuit board 273 surrounds drum 212 and is operatively connected to circuit board 248 incorporated in arm 233.

[0033] Receiving diodes 272 operatively face cylindrical surface 230a of cover 230 (Fig. 12). The latter has a radial through channel 278 leading to cylindrical surface 230a to define light passage 230c. A tubular support 277 housed within radial through channel 278 is closed at its outer end by a disc-shaped window 286 made of a transparent material, e.g., glass, arranged at the same level of cylindrical surface 230a. Tubular support 277 is retained by a grub screw 287 which is screwed into cover 230.

[0034] With this embodiment, the light-guiding means further comprise an optical device 262 which is inserted into the rear end of driving shaft 222 for collimating the light emitted by emitting diode 246. Optical device 262 comprises a spherical lens 282, which is locked in a seat defined between a flanged nut 280 screwed into the rear end of driving shaft 222, and an axially holed threaded cap 276 which is screwed into flanged nut 280. The light beam generated by emitting diode 246 and collimated by spherical lens 282, in a way similar to the above-described second embodiment, passes through hollow driving shaft 222 and is reflected towards receiving diodes 272 by a mirror 266 incorporated in drum 212. Mirror 266 is slanting at an angle of 45° to the axis of drum 212 for reflecting the light beam towards radial through channel 278, into tubular support 277. Advantageously, mirror 266 is attached to a support 267 incorporated in cover 230.

[0035] A few preferred embodiment of the invention have been described herein, but of course many changes may be made by a person skilled in the art within the scope of the claims. For instance, the yarn-unwinding sensor according to the invention can be located at an intermediate position of the drum to be simply used as a stock sensor adapted to provide a binary information about the presence/absence of stock at a predetermined area of the drum. Moreover, in the first two embodiments described above the annular light-guide surrounds the drum, whereby the light-emitting means and the light-receiving means radially face each other to intercept the yarn upstream of the rounded delivery edge. However, it would be possible to coaxially arrange the light-emitting means in front of the delivery end of the drum in such a way as to intercept the yarn downstream of the rounded delivery edge.

Claims

1. A storage yarn feeder (10), comprising:

- a motorized, yarn-winding rotary drum (12), which is rotatably supported with respect to a motor-housing (16), and is adapted to have a plurality of yarn loops (Y) wound on itself which are adapted to be unwound upon request from a downstream machine, and

- a yarn-unwinding sensor which is adapted to count the yarn loops unwinding from the rotary drum (12),

characterized in that said yarn-unwinding sensor comprises:

- light-emitting means (42) integral with the motor-housing (16),

- light-receiving means (44) integral with the motor-housing (16),

- one of said light-emitting means (42) and said light-receiving means (44) having an annular configuration operatively facing an annular surface (30a) of the rotary drum (12) from which the yarn is unwound, and

- light-guiding means (66) integral with the rotary drum (12), which are arranged for guiding light from said light-emitting means (42) to said light-receiving means (44) through a light passage (30c) defined on said annular surface (30a),
whereby the unwinding of yarn from the rotary drum (12) is determined on the basis of the light dimming resulting from the yarn transiting on said light passage (30c).

2. The storage yarn feeder of claim 1, characterized in that said light-guiding means comprise an optical fiber cable (66).

3. The storage yarn feeder of claim 1, characterized in that said light-guiding means comprise a mirror (166) arranged to reflect light from said light-emitting means (146) to said light-receiving means (172) through said light passage.

4. The storage yarn feeder of any of claims 1 to 3, characterized in that said light-emitting means (42) have said annular configuration for generating an annular light beam investing said annular surface (30a) of the rotary drum (12).

5. The storage yarn feeder of claim 4, characterized in that said light-emitting means (42) comprise a light source (46) adapted to generate a rectilinear light beam, and an annular light-guide (50) which is arranged between said rotary drum (12) and said light source (46) and is shaped to convert said rectilinear light beam into said annular light beam.

6. The storage yarn feeder of claim 5, characterized in that said annular light-guide (50) has a light propagation annular portion (52) and a light insertion tangential portion (54), which tangentially projects from said annular portion (52) and terminates with an inlet surface (56) facing said light source (64) to receive the rectilinear light beam and channelling it into the annular portion (52).

7. The storage yarn feeder of claim 6, characterized in that said annular portion (52) coaxially surrounds the rotary drum (12) and has a substantially L-shaped, cross-sectional profile having:

- an oblique outer edge (58) defined between the two dashes of the L-shape, and

- an annular face (59), which axially delimits the annular portion (52) at its end facing away from the oblique outer edge (58), and has a processed surface adapted to reflect the light (I) propagating within said annular portion (52) in a longitudinal direction towards said oblique outer edge (58),

whereby the light investing said oblique outer edge (58) is radially reflected at right angles towards said annular surface (30a) of the rotary drum.

8. The storage yarn feeder of claim 4, characterized in that said light-guiding means comprise an optical fiber cable (66) having an inlet end (64) arranged to receive said annular light beam via an optical device (62), which is integral with the rotary drum (12) and is provided with a lens (82) arranged to focus said annular light beam onto said inlet end (64), and an outlet end (68) facing said light-receiving means (72).

9. The storage yarn feeder of claim 8, characterized in that said optical device (62) comprises a gauged hole (85) arranged upstream of said lens (82) with respect to the incoming direction of the annular light beam, which is adapted to diaphragm said annular light beam.

10. The storage yarn feeder of claim 1, characterized in that said light-guiding means are arranged in such a way as to project a light beam outwards through said light passage (230c), and said light-receiving means (244) have said annular configuration to receive said light beam.

11. The storage yarn feeder of claim 10, characterized in that said light-receiving means (244) comprise a plurality of light receivers (272) surrounding the rotary drum (212).

12. The storage yarn feeder of any of claims 1 to 11, characterized in that said rotary drum (12) is mounted on a hollow driving shaft (22), through which the light transmitted from said light-emitting means (46) to said light-receiving means (72) via said light-guiding means (66) passes.

Drawing