EP1152970A1

EP1152970A1 - Optoelectronic thread sensor or optoelectronic sensor

Info

Publication number: EP1152970A1
Application number: EP00907583A
Authority: EP
Inventors: Jerker Hellström; Lars Helge Gottfrid Tholander
Original assignee: Iro Patent AG
Current assignee: Iropa AG
Priority date: 1999-02-19
Filing date: 2000-02-18
Publication date: 2001-11-14
Also published as: SE9900610D0; WO2000048934A1

Abstract

The invention relates to an optoelectronic thread sensor (S) of a thread guide. A reflection area (M) is located on one part (3) of the thread guide and a light source (L) or a receiver (R) is located on another part (11), an area for the passage of the thread being provided between said reflection area and said light source. The light source (L) is a laser light source. The reflection area has a retroreflective surface structure (A). The reflection area (M) could alternatively have a semi-retroreflective surface structure with a spread curvature as another way of obtaining high modulation while shading the light patch formed by the light source.

Description

Optoelectronic thread sensor or optoelectronic sensor

The invention relates to an optoelectronic thread sensor according to the preamble of claim 1 and an optoelectronic sensor according to the preamble of claim 10

Optoelectronic thread sensors are used in thread processing, in particular on or in thread delivery devices, for example for detecting the presence or absence of the thread or the movement of the thread through a detection area, for measuring the speed of the movement of the thread through a passage area, for detecting a thread break or If the light source illuminates a reflection area, the light there forms an approximately round light spot. The receiver responds to the shadow of the light spot or the reflection of the light from the thread and generates a useful signal. An important parameter for the goodness of the useful signal is the so-called Modulation, i.e. the way, the strength and the speed of the switch-off process or the palpable change in reflected light The higher the modulation, the more powerful the useful signal A small, concentrated light spot has the advantage of relatively high modulation, better scanning precision and high sensitivity to interference With conventional thread sensors that work with LEDs, only a maximum of 10% modulation can be achieved without aids due to unavoidable light scattering. High signal processing costs are required for signal evaluation. Manufacturing and assembly are necessary, especially in the case of series production of thread sensors, incorrect positioning of the light cannot be avoided from the light source, the reflection area and the positioning of the receiver.For example, an LED sits differently in its holder in one installation case than in the next installation case. The more serious the malposition, the smaller the light spot on the reflection area and the greater the distance between the light source and the reflection area are in a thread delivery device with a reflection thread sensor, the light source or the receiver and the reflection area are usually attached to structurally separate parts of the thread delivery device because the thread passes between them Functional relative movements between these parts (e.g. the storage body with the reflection area, and the housing bracket containing the light source and the receiver), which impair the precise response of the receiver.Therefore, practice-related interference influences the theoretical pursuit of high reliability and scanning accuracy with a small, concentrated and high-contrast light spot an undesirable limit

Optoelectronic thread sensors of this design are described in W097 / 37247

Furthermore, EP-A-0 460 699 discloses a thread sensor with a light barrier, which emanates from a laser light source mounted on one part and is directed at a receiver mounted in another part of the thread device, which affects misalignments due to manufacturing tolerances or assembly deviations and inevitable relative movements between the parts the reliability of the thread sensor, although a high modulation would actually be expected with the bundled and concentrated laser light and a small light spot. For this reason, laser light sources have so far not been used for thread sensors working with a reflection area

The object of the invention is to increase the scanning accuracy in a thread sensor of the type mentioned at the outset, ie to achieve the highest possible modulation, and to improve the reliability under influences which are caused by manufacturing, operating and assembly-related malpositions and / or based on relative movements between the light source or the receiver and the reflection area

The problem is solved with the features of claim 1 and the independent claim 10

Laser light creates an exact, sharply defined and high-contrast light spot on the reflection area, which leads to very strong modulation at the receiver and thus to strong useful signals when the thread passes through, so that without Notable additional electrical expenditure not only allows the presence or absence or the passage of the thread to be detected very precisely, but even the speed of passage can be determined with high accuracy. The retroreflective surface structure has the peculiarity of returning incident light rays to the light source with high power regardless of the direction of impact The reflection light is available at the location determined by the position of the laser light source, from which it can be directed to the receiver, which may be positioned on the same part. Manufacturing, operational and assembly-related misalignments and relative movements between the parts have no influence on the reliability In addition, a large degree of freedom in the positioning of the light source and the receiver and also the reflection area can be used, since the retroreflective surface structure reflects laser light with very good efficiency exactly to the laser light source A modulation of 40% or more can be achieved with laser light

In the optoelectronic sensor with the semiretroreflective surface structure, an optimally small-sized light spot on the surface structure is spread during reflection by the overlapping reflection behavior of the convexly curved surface structure in the direction of the curvature, i.e. the reflection light reflected to the light source forms a spread ellipse from a small light spot or an elongated light bar from which the receiver generates precise and strong useful signals due to the high light density in the transverse direction with high modulation.This applies above all to laser light, but also to conventional light sources which, with or without auxiliary devices (aperture or lens), produce a small, bright light spot capable of producing because in the respective direction of the plane of the retroreflection, the reflection light has a very high light density. In addition, the retroreflection prevents the interference factors mentioned

A VCEL or a surface emitting laser diode (SELD) as a laser light source is inexpensive, easy to install and requires only a small additional electronic effort Forming the retroreflective surface structure from prisms or cooperating reflectors leads, depending on the requirements, to high reflection non-yield and the desired strong modulation during thread passage

Since the combination of the laser light source and the retroreflective surface structure results in a high level of insensitivity to manufacturing or assembly-related malfunctions of the optically cooperating components that occur during operation, an extremely small light spot of only 1.0 mm in diameter can be used, which guarantees the desired is strong modulation

If the retroreflection can result in even a slight scatter, the receiver should be positioned close to the laser light source, whereby the orientation of the laser light source can be adapted to the structural conditions in the area of the thread sensor and not due to the need for the smallest possible distance or one Direction of impact as vertical as possible

If a reflection light deflection device is provided, the receiver can be positioned at any point. Since the reflection light is reflected exactly in the direction of the laser light source and must be deflected from this direction to the receiver, the deflection device for the laser light must be transparent

It is expedient to use a mirror which is broken through for the concentrated and thin laser light beam, the mirror surface of which reflects the reflection light to the receiver. Alternatively, a semi-permeable mirror can be used, which penetrates the laser light, but on the other hand the reflection light is deflected

In order to be able to mount the laser light source and the receiver next to one another and with the same orientation, which brings advantages in terms of assembly technology and saves installation space, it can also be useful to redirect the laser light and to use either a semi-permeable or a perforated mirror for the reflection light A cost-effective and relatively precise positioning of the laser light source of the receiver is useful with the so-called surface mounting technology (SMD) on a common circuit board.The two components can be covered by a common housing, which offers protection against contamination and allows the laser light or reflection light to penetrate

In the case of the sensor using the semiretroreflective surface structure with its spreading curvature, the light source can be a laser diode, preferably a VCEL or surface emitting laser diode (VCEL vertical cavity emitting laser)

In the case of the sensor, the concentrated and bright light spot on the semiretroreflective surface structure is spread in one dimension when reflecting due to the normal reflection behavior of this surface structure. The spread dimension should expediently coincide approximately with the longitudinal axis of the thread, which extends across its longitudinal axis through the passage area of the sensor Then a very high modulation can be achieved and a disruptive influence, for example of relative movements, on the scanning reliability is better eliminated

A light-emitting diode could also be used as the light source, which is able to form the small, bright light spot on the semiretroreflective surface structure

If the semiretroreflective surface structure is arranged on a drum-shaped storage body of a thread delivery device, the spreading curvature is expediently at least largely identical to the surface curvature of the storage body, and the direction of the spreading curvature is oriented in the circumferential direction of the storage body, which inevitably and inevitably causes torsional vibrations of the storage body the axis of the memory body can occur thanks to the curvature, do not produce any rotational displacements of the reflected light spot

Embodiments of the subject matter of the invention are explained with reference to the drawing

1 is a schematic side view of a thread delivery device with at least one optoelectronic thread sensor,

2 shows an enlarged section of an axial section of the thread delivery device from FIG. 1 with a first embodiment of a thread sensor,

3 shows a further embodiment of a thread sensor,

4 shows a further embodiment of a thread sensor,

5 shows a schematic perspective illustration of the operation of, for example, the thread sensor from FIG. 2,

6 shows a further embodiment,

7 shows a perspective illustration of a detail of a further embodiment, in particular for an optoelectronic sensor,

8 schematically shows a frontal view of a thread delivery device with the sensor from FIG. 7,

9 is a side view of FIG. 8, and

10 is a diagram showing the spread of a light spot A yarn delivery device F in FIG. 1, for example a weaving machine weft delivery device, has a housing 1 with an electric drive motor 2 and a drum-shaped storage body 3, which is rotatably mounted on a drive shaft (not shown), but by means of cooperating magnets 3 'but rotating with it Drive shaft is prevented A winding element 4 is driven by the drive shaft, which temporarily stores a thread Y inserted into the thread delivery device F from the left in adjacent windings on the storage body 3. From there, the thread Y becomes the overhead of the storage body 3 and, if appropriate, is pulled axially by a trigger 6 withdrawn The housing 1 has a housing extension 5, in which two optoelectronic thread sensors S are arranged in the embodiment shown, which are aligned with reflection areas M on the storage body 3. The sensors S are connected to a control unit C of the thread delivery device, which controls the drive motor 2 carries out

Each thread sensor S has at least one light source E and a receiver R. The light source E directs a light beam onto the reflection area M, the receiver R is subjected to reflection light. The light beam generates a light spot on the reflection area, which is shaded when the thread passes. The receiver speaks the shading or the release of the light spot and generates an output signal

The sensor S on the left in FIG. 1 is used, for example, to monitor the position of the front limit of the thread supply on the storage body 3. The sensor on the right in FIG. 1 monitors the removal of the thread by generating a signal with each thread pass. These signals are used to either pull off Number of windings is paid or the speed of the thread is determined during take-off In addition, a further sensor, not shown, could be arranged at the exit area of the thread from the take-up element 4 in order to detect a thread break. A sensor could also be provided in the area of the take-off can 6 Thread delivery devices Such optoelectronic thread sensors are also used in thread delivery devices for knitting machines in which the storage body can be driven in rotation, if necessary According to the invention, a laser light source L, for example a VCEL or surface-emitting laser diode, and a retroreflective surface structure A are provided in each sensor S as light source E, and a retroreflective surface structure A is provided in the reflection region M. The laser light source (FIGS. 2 to 4) is used to produce a precisely dimensioned, approximately cylindrical and thin light beam 7, which produces a very small, bright and high-contrast light spot 8 on the surface structure A. The peculiarity of the retroreflective surface structure A is that it reflects incident light essentially in the incident direction, ie essentially back to the laser light source L, with a small amount Loss and little scattering If the thread Y moves in or through the light spot, strong modulation occurs at the receiver R, which leads to a powerful useful signal. The modulation achievable with the laser light source and the retroreflective surface structure A is approximately 40% or even higher

2, the receiver R and the light source E, ie the laser light source L, are mounted next to one another on a printed circuit board 12, for example in surface mounting technology (SMD). The receiver R and the laser light source L are expediently diodes. These diodes are accommodated in a common housing 11. which is located at a distance from the surface of the storage body 3 and has a light passage 13. The direction of the light beam 7 from the laser light source can be chosen freely, since the retroreflective surface structure A always reflects the light in the opposite direction to the direction of incidence slightly larger image of the light spot 8 on the receiver R

The retroreflective surface structure A can be arranged on the surface of the storage body 3, or set slightly lower in a recess 10. For example, it has a large number of prisms or a large number of reflectors arranged at certain angles relative to one another. For example, the retroreflective surface structure is made of a transparent plastic or integrated glass plate or arranged on a plastic film that is attached to or in the storage body 3, the laser light source L in the housing 11 of the thread sensor S is aligned directly with the retroreflective surface structure A of the reflection area M. In front of the laser light source L, a reflection light deflection device D is provided, for example a mirror 14 with an opening 15 for the laser light 7, the mirror surface being inclined at an angle to the reflection light 9 as indicated at 9 ', on the side and below throw receiver R offset approximately 90 ° with respect to light source E. Shields 16 prevent mutual interference.

In the thread sensor in FIG. 4, the light source E or laser light source L and the receiver R are mounted on a common printed circuit board 12 which is oriented approximately vertically or relatively upright in relation to the retroreflective surface structure A. The direction of light emission and the direction of reception are approximately parallel to one another. The laser light source L is spaced from the receiver R. The light beam 7 is deflected in a housing 11 on a deflecting mirror 19 by approximately 90 ° and directed as a deflected light beam 7 'onto the retroreflective surface structure A. A deflection mirror 14 equipped with an aperture 15 directs the reflection light 9 onto the receiver R, as indicated at 9 ′. The laser light source L and the receiver R are expediently positioned in channels 17, 18 that avoid mutual interference.

FIG. 5 schematically illustrates how the laser light source L throws the light beam 7 onto the retroreflective surface structure A, which is, for example, plate-shaped, and generates the small, approximately circular light spot 8 there. The diameter of the light spot can be approximately 1.0 mm or be somewhat smaller or somewhat larger. The reflection light 9 forms the light spot 8 on the receiver R arranged next to the laser light source L. If the thread shown in FIG. 5 moves transversely to its longitudinal axis over the light spot 8, the light spot 8 is disturbed, changed or shadowed, to which the receiver R responds with a signal. Thanks to the small size and the high light density of the light spot 8, a strong modulation occurs. The reflection area M is shown large, and can actually be much smaller and of a different shape. A relatively large reflection area Rich M of the retroreflective surface structure A offers the advantage of being able to arrange the laser light source L and the receiver R as desired, or, if appropriate, of letting two or more laser light sources use the same retroreflective surface structure A for a plurality of sensors working in an adjacent manner

In the thread sensor S in FIG. 6, the laser light source L serving as the light source is oriented approximately vertically onto the retroreflective surface structure A in order to generate the light triangle 8 there. Since the receiver R is arranged offset by approximately 90 ° to the laser light source L, reflection is avoided -Umlenkvorπchtung D a semipermeable mirror 23 is provided, which is transparent in the direction of arrow 24 for the light beam 7, in the direction of arrows 25, however, acts as a full mirror and throws the reflection light 9 on the receiver R. Such a semipermeable mirror 13 could also be used in the 3 and 4 are used

An optoelectronic sensor S is indicated in FIG. 7, in which the light source E is a laser diode L or a conventional LED, which generates a highly concentrated light beam and thus a small light spot 8. The reflection area M in this sensor S is a semiretroreflective surface structure A ', which - facing the light source E - has a convex spreading curvature K. It is, for example, a transparent plastic plate 20, on the underside 21 of which the semiretroreflective surface structure A 'is provided. The surface structure A' is retroreflective in the plane caused by the longitudinal direction X and A straight line defined by the light beam 7 is formed, ie expediently in all radial planes which contain the axis of the expansion curvature K. The plate 20 can be a section of a cylinder jacket. The surface structure reflects in all planes which are oriented parallel to the direction Z. A 'normal, ie incident light is reflected in accordance with the angle of incidence. This ensures that the light spot 8 is reflected by the retroreflection in the opposite direction to the light beam 7, but at the same time is brought about by the spreading curvature K from an approximately round shape into an elliptical shape or into the shape of a light bar, its longitudinal extension is parallel to the Z direction A semipermeable mirror 23 in the light beam 7, for example, which is transparent to the light beam 7, reflects the spread light spot G onto the receiver R Specifically, such a semiretroreflective surface structure A 'can be formed, for example, in an approximately 3 mm thick, curved plastic plate by parallel grooves with an opening angle of 90 ° and a flank angle with respect to the vertical of 45 ° are formed on the underside in the direction of Z, and their flanks are reflective, e.g. mirrored, because the spread light spot E has a high light density in the direction of its narrow dimension has a high modulation, which is particularly high if a laser light source L is used. As mentioned, other light sources can be used which are capable of producing a highly concentrated light beam 7, for example with the help an additional aperture or lens system (not shown)

The sensor S from FIG. 7 can expediently be used in a thread delivery device, as shown in FIGS. 8 and 9, the semiretroreflective surface structure A 'having the same spreading curvature K as the curvature of the surface of the storage body 3, thereby losing torsional vibrations (arrow 22 in FIG 8) of the storage body 3 about its axis their influence on a proper reflection to the receiver R in a yarn delivery device with a stationary storage body 3, namely, torsional vibrations occur during operation, which impair the scanning result when the reflected light participates in the torsional vibrations through the axis of the storage body 3 as the spreading curvature K having the curvature axis and the semiretroreflective property of the surface structure A ', the reflection light 9 ″ hits the receiver R correctly despite torsional vibrations

In FIG. 9, the light beam 7 is directed obliquely onto the surface structure A ′ in the radial plane of FIG. 8, in which the light source E and the axis of the storage drum 3 are located. The reflection light 9 ″ is directed onto the deflecting mirror 14 formed here with the opening 15 thrown and reflected by this at 9 '"on the receiver R, thanks to the spreading curvature K, the longitudinal direction of the spread light spot G approximately coincides with the longitudinal axis of the thread Y, so that this causes a strong modulation at the receiver R when passing through the light spot 8 10, the light spot 8 is deformed with its diameter d1 from the reflection light to the spread light spot G, the narrower dimension d2 of which is only slightly larger than d1, while its spread dimension d3 is considerably larger than d1. This not only ensures that the reflected one and the spread light spot G reliably hits the receiver R despite manufacturing and assembly-related mispositions, but that a strong modulation is also achieved if the thread Y shadows or releases the spread light spot G with the longitudinal direction oriented parallel to its longer dimension very fast and therefore also with strong modulation

1 to 5 with the retroreflective surface structure A and the laser light source L, the surface structure A can be flat or curved

Claims

claims

1. Optoelectronic thread sensor of a thread delivery device (F), with at least one reflection area (M) on a thread delivery device part (3) and at least one light source (E) and at least one receiver (R) on another thread delivery device part (5), wherein between the reflection area and a thread passage area is provided for the light source or the receiver, characterized in that the light source (E) is a laser light source (L) and that the reflection area (M) has a retroreflective surface structure (A).

2. Thread sensor according to claim 1, characterized by at least one laser light source (L) in the form of a VCEL or a surface emitting laser diode.

3. Thread sensor according to claim 1, characterized in that the retroreflective surface structure (A) is composed of prisms or retroreflective cooperating reflectors.

4. Thread sensor according to claim 1, characterized in that with the laser light source (L) on the retroreflective surface structure (A) light spot (8) between 0.5 and 4.0 mm, preferably about 1, 0 mm, is large .

5. Thread sensor according to claim 1, characterized in that the receiver (R) is arranged closely adjacent to the laser light source (L) and in the reflection light region (9) of the retroreflective surface structure (A).

6. Thread sensor according to claim 1, characterized in that the receiver (R) is spaced apart and / or offset from the laser light source (L), and that in front of the laser light source (L) is a reflection light deflection device for the emerging laser light (7) ( D) is provided and aligned with the receiver (R).

7 thread sensor according to claim 6, characterized in that the receiver (R) and the laser light source directed directly onto the retroreflective surface structure (A) are offset from one another at a certain angle, preferably approximately 90 °, and that the deflection device (D) is used for the laser light (7) has a perforated mirror (14) or a semipermeable mirror (23) that is transparent to the laser light (7) and reflects the reflection light (9), the mirror surface of which has the angle between the reflection light (9) and the receiver (R ) halved

8 thread sensor according to claim 6, characterized in that the laser light source (L) and the receiver (R) are arranged spaced apart from one another with approximately parallel exit or reception directions, that between the laser light source (L) and the retroreflective surface structure, a deflecting mirror (19) It is provided that between the deflecting mirror (19) and the retroreflective surface structure (A) a further, either semipermeable or perforated mirror (14, 23) for the reflection light (9) is provided, which is the angle between the reflection light and the direction of reception of the receiver (R) cut in half

9 thread sensor according to claim 1, characterized in that the laser light source (L) and the receiver (R) on a common circuit board (12) surface-mounted (SMD) laser or photodiodes, and, preferably, by a common housing (11) are covered

10 optoelectronic sensor, in particular for detecting thread-like material, with a light source (E) emitting a bundled light beam (7) onto a reflection area (M) and at least one receiver (R) aligned with the reflection area (M), characterized in that in the reflection area (M) a semiretroreflective surface structure (A) is provided with a spreading curvature (K) that is convex to the light source (D) and the receiver (R), the semiretroreflective surface structure (A) reflecting normally in curvature (Z) and in a direction curvature (Z) Z) transversely oriented second direction (X) is retroreflective

11. Sensor according to claim 10, characterized in that the light source (E) is a laser light source (L) such as a laser diode, preferably a VCEL or surface emitting laser diode.

12. Sensor according to claim 10, characterized in that the approximately round light spot (8) formed by the light beam (7) on the semiretroreflective surface structure (A) when it is reflected with the semiretroreflective surface structure (A ') on the receiver ( R) or a reflection deflection device (D), preferably a semipermeable or perforated mirror (14, 23), a slender light ellipse (G), which is placed in front of the receiver (R) and is transparent to the light beam (7) from the light source (E). or a narrow reflection light spot (G) spread in the transverse direction can be formed, the main axis or longer dimension of which corresponds to the direction of curvature (Z) of the semiretroreflective surface structure (A ') and has a dimension which is several times larger in the Z direction than in that with the direction (X) of the semiretroreflective surface structure A) corresponding direction.

13. Sensor according to claim 10, characterized in that the light source (E) is a light-emitting diode (LED).

14. Sensor according to claim 10, characterized in that the semiretroreflective surface structure (A ¹ ) is arranged on or below the surface of a drum-shaped storage body (3) of a thread delivery device (F) that the light source (E) and the receiver (R) in a cantilever (5) separate from the storage body (3) that the spreading curvature (K) corresponds at least approximately to the surface curvature of the storage body (3) or has the storage body axis as the axis of curvature, and that the direction of curvature (Z) with the circumferential direction of the memory body (3) matches.