GB1589323A - Device for continuously measuring a transverse dimension of a travelling yarn - Google Patents

Abstract

The measuring device consists of a mechanical scanning device having two mutually sprung contact members (22, 24) bearing against the textile thread (F) or other item, and of a pickup which operates without inertia, e.g. a capacitive pickup, and converts changes in the mutual spacing of the contact members into an electric signal. In the preferred embodiment, one contact member is designed to be fixed and the other is designed as an adjustable leaf spring of low thickness. The adjustability enables the scanning device to be matched to the thickness and softness of the textile thread. <IMAGE>

Description

(54) A DEVICE FOR CONTINUOUSLY MEASURING A TRANSVERSE DIMENSION OF A TRAVELLING YARN (71) We, GEBRijDER LOEPFE AG, a Swiss Company, of Zypressenstrasse 85, 8040 Zurich, Switzerland, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a device for continuously measuring a transverse dimention of a travelling yarn.

Measuring and testing devices for continually detecting and assessing a transverse dimention, such as the cross-sectional area or diameter of fast travelling textile yarns and other like structures are generally known and in commercial use. Such devices are, by way of example, part of electronic yarn clearers on yarn winding machines which serve for eliminating thick and thin places of the yarn by means of a severing device.

Prior measuring devices of substantially inertialess operation are based on the capacitive or optoelectrical method for detecting the cross-sectional dimension of a travelling yarn.

With both of those measuring devices, the sensing signal is dependent not only on the cross-sectional dimention of the yarn, but also on various interferences. With the capactive method, the result is influenced by the dielectric properties of the yarn material which essentially depend upon the chemical nature and the humidity thereof. With the optoelectrical measuring method, the result is affected by the absorption and reflection, in particular the colour of the material.

A so-called evenness tester is known where the yarn passes between a pair of rotatable rollers at a relatively low speed ofe.g. 12 yards per minute. One of those rollers is supported by a pivotable lever which is weight-loaded and thus held toward the other roller by gravity.

The pivoting movements of said lever induced by the irregularity of the travelling yarn are transferred to an electromagnetic transducer through a micrometer which serves for zero adjustment. This evenness tester furnishes time average values of the yarn diameter, and thus is unsuitable for detecting instantaneous values, in particular of yarns which travel at a high speed of 100 m/min or more. On the other hand, the result of such a measurement is independent of the optical and dielectrical properties of the yarn material.

According to the invention ,there is provided a device for continuously measuring a transverse dimension of a travelling yarn, the device comprising a base body; mechanical yarn sensing means supported by the base body and including a fixed member and a movable member defining a yarn path between them a leaf spring having one end mounted on the base body in such a way that the pressure exerted on the yarn by the leaf spring can be adjusted, the other end being free and integral with the movable member which is urged towards the fixed member by the spring; and means contac tlessly co-operating with the free end of the leaf spring for detecting instantaneous deflections thereof and trandsducing them into electrical sensing signals.

The invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Figures 1 , 2 and 3 are block diagrams of various transducers and associated electronic circuits; Figure 4 is a schematic representation of a prior art capacitive transducer; Figure 5 and 6 are schematic representations of capacitive transducers which may be used in a device according to the invention; Figures 7, 8 and 9 show a measuring device comprising an inductive transducer in front view, plan view, and end view, respectively; Figures 10,11 and 12 are respective front, top and end views of a measuring device comprising an inductive transducer; Figures 13 and 14 show a measuring device in end view and front view, respectively, provided with an optoelectrical transducer;; Figures 15 and 16 show a modification of the contact members of a sensor in front view and end view, respectively; and Figures 17 and 18 show still another modification of the contact members of a sensor With reference to Figure I, a capacitive transducer 1 which is part of a measuring device (not shown) is connected to a resonant circuit (not shown) of a high frequency generator 10 which provides an A.C. voltage in the Megahertz frequency range. The output signal of high frequency generator 10 is supplied to a series connection of circuits 11, 12 and 13, where it is rectified in rectifier 11, smoothed in smoothing circuit 12 and delivered to switching device 13, e.g. a relay. Electronic stages such as the circuits 10,11 and 12 are known in the art and need not be described in detail.

The sensitivity of response of the electronic circuitry shown in Figure 1 may be adjusted, for a specific yam travelling through transducer 1, such that switching device 13 is not operated by anormal yarn end, however, is operated by a thick place having a diameter of e.g. more than 200% of the normal or mean diameter of the yarn. In this event, relay 13 responds and stops the travel of the yarn.

According to Figure 2, an inductive transducer 2,e.g. an induction coil with a ferrite core, is connected to electronic circuitry 10, 11, 12, 14 which substantially operates in a similar manner as the circuitry illustrated in Figure 1, however, a monoflop 14 is provided in the place of relay 13.

In Figure 3, and optoelectrical transducer 3 comprises a light source 4, e.g. a light emitting diode, and a photocell 5, e.g. a photodiode.

Pulse generator 6 supplies light source 4 which rectrangular pulses of a repetition rate in the range of some 10 KHz, e.g. 50 KHz. An A.C.

amplifier 15 is connected to photocell 5, and the following circuits 11, 12 and 14 are similar to those shown in Figure 2. Optoelectrical transducer 3 may be arranged for measuring the cross-sectional area of the light beam through which the yam travels, or for detecting the position of a member contacting the travelling yarn, by means of light reflected from said contacting or contact member.

With reference to Figure 4, two fixed electrodes la, 1b arranged at a mutual distance do constitute a measuring capacitor through with the yarn G travels. Electrodes 1a, Ib form a measuring gap Mo between them.

Measuring gap Mo has a fixed volume indpendent of the volume or diameter of the yarn G. With this known transducer, the changes of the capacitance caused by the irregularity of the travelling yarn G are sensed and measured. Generally, the volume of measuring gap Mo is substantially greater that the volume of the yarn end G contained in gap Mo. With this known capacitive transducer, the result of the measurement depends not only on the dimensions, in particular the crosssectional area of the yarn G, but also on the dielectrical properties thereof, i.e. the material and humidity of the yarn G.

Corrections must be made for eliminating those desired effects.

According to Figure 5, a capacitive transducer or measuring capacitor comprises a fixed electrode la and a movable electrode lc which is loaded by a pressure spring 19 toward fixed electrode la. Electrodes la, lc serve at the same time as members contacting the travelling yarn G, and provide a variable measuring gap M whose width d varies continually with the changes of the crosssectional dimensions of the travelling yarn G.

A certain change of the yarn diameter results in a corresponding proportional change of the volume of measuring gap M, and thus in a much greater absolute and relative change of the capacitance when compared with the known transducer shown in Figure 4. Thus, the novel capactive transducer provides for much greater sensitivity of response. Moreover, the effect of the dielectric properties of yarn G upon the measurement is relatively small, since the yarn G only slightly contributes to the changes of the capacitance which, with this inventive embodiment, are due mostly to the changes of the volume of the variable measuring gap rather than the capacitance of the yarn itself.

The capacitive transducer which is shown in Figure 5 in schematic representation may additionally be used for detecting the condition "no yarn present" and "yarn at a standstill". In the former event, electrodes la, Ic are shortcircuited, in the latter event the irregular A.C.

component of the sensing signal indicative of yarn travel disappears. Both conditions may be indicated by known electronic circuitry.

In the structure shown in Figure 6, the lower gap through which yarn G travels is separate from the capacitive measuring gap M. A fixed lamella 24 which may be made of insulating material, such as ceramic oxide, and a movable spring-loaded electrode Ic are in contact with the travelling yarn G. A fixed counterelectrode la' is provided above movable electrode Ic, such that the electrodes la' Ic confine a variable measuring gap M. The width h of measuring gap M is not the same and the mutual distance d of contacting or contact members Ic, 24. With this embodiment, the effect of the dielectric properties of yarn G upon the result of the capacitance measurement is entirely eliminated.

In Figures 7 through 14 various measuring devices each comprising a sensor and a transducer are represented. With the yarn G travelling through such a measuring device, the deviations of the crosssectional dimentions of the yarn G induce positional changes of one of the yarn contacting or contact members as mentioned above. Those positional changes are detected by a transducer and translated into electrical sensing signals.

The measuring devices are shown in approximately natural scale in Figures 7 through 14.

However, the dimensions of those devices are in no way critical and may be accommodated to the desired applications within broad limits.

The embodiment of measuring device represented by Figures 7, 8 and 9 comprises a base body 16 which, as shown by the front view of Figure 7, is substantially L-shaped. A perpendicular extension 17 of base body 16 serves for supporting a thin leaf spring 19 made of elastic metal, such as spring steel, and provided with a longitudinally extending slotted hole 20 through which a fixing screw 21 or equivalent structure is passed which is screwed into extension 17. The latter has a recess 18 for receiving leaf spring 19. The bottom 23 of recess 18 slopes towards the front end 22 of leaf spring 19. Front end 22 represents a first contact member which touches the yam at the upper side thereof.A rectangular lamella 24 composed of three layers 25, 26, 27 is arranged beneath first contact member 22 and forms a second contact member which may be cemented to the top of base member 16. Lamella 24 comprises a base support 25 which may be made of insulating material, such as ceramics, an electrode 26 applied to base support 25, and a hard protective layer 27 provided on electrode 26.

Electrode 26 may be a metallic lamella or made of sheet material, or applied to base support 26 as a thin metal layer, using known technology. Protective layer 27 may be made preferably of a hard material, such as ceramic oxide, and may be applied onto electrode 26 by means of the known process of plasmation.

The front end 22 of leaf spring 19 operates as a counterelectrode to electrode 26, and both electrodes form the plates of a capacitor 1, Figures 1 and 5, whose capacitance depends upon the distance d between the surface of lamella or contact member 24 and the opposite surface of front end 22. Electrode 26 and counterelectrode 22 are connected to high frequency generator 10, Figure 1 , through lead wires (not shown). The capacitance of capacitor 1 continually changes with the variable distance d between the contact members 22, 24, when a yarn travels through the gap M between electrode 26 and counterelectrode 22.

In Figures 7 and 8, the path along which the yarn travels is schematically represented by line F-F. A yam channel 28 of substantially U-shaped cross-section is provided in base body 16, which channel passes through extension 17.

Leaf spring 19 may be made of spring steel of a thickness of about 0.05mm. The length of leaf spring 19 may be about 40mm and its width about 1 Onam. Due to its small thickness leaf spring 19 has a very low mass and thus a low inertia, enabling the front end 22 to follow the changes of the yarn diameter substantially without inertia. The pressure which leaf spring 19 exerts on the yarn may be of the order of one pond.

By means of slotted hole 20 and fixing screw 21 it is possible to adjust leaf spring 19 in its lengthwise direction and thus to change the length of measuring gap M in the direction of yarn travel. Such length may be about 1 Omm.

At the same time, lengthwise adjustment of leaf spring 19 will alter the distance of between the members 22 and 24, because of the slope of recess 18, and if a yarn is present between the members to prevent the distance d being decreased, the pressure exerted on the yarn will be altered.

The design of contacting or contact members 19, 24 shown in Figures 7 and 8, where the upper contact member 19 is shaped as a flat leaf spring offers the valuable advantage that the electical sensing signal is only slightly responsive to the unavoidable traversing movements of the travelling yarn in measuring gap M. This holds true also for the devices shown in the figures to follow.

Contrarily, due to the lack of homogeneity of the measuring zone, with known optoelectrical and capacitive transducers the traversing movements of the travelling yam have a relatively great influence upon the sensing signal, which traversing movements cannot be completely avoided even when using tight yarn guides.

The measuring device represented by Figures 10, 11 and 12 has a block-shaped base body 16' having a rear recess 18' and a front recess 31.

Two side walls 17' arranged on base body 16' to both sides of rear recess 18' are provided with perpendicularly extending slotted holes 20'. Leaf spring 19' has a rear end which is fixed at a cylindrical bearing member 29. The latter is mounted between side walls 17' by means of a support bolt 21' and nut 30 so as to be adjustable in a perpendicular direction to adjust the pressure exerted on the yarn by the leaf spring, and is pivotable about axis A (Figure 12) of support bolt 21'.

An inductive transducer comprising a coil 32 and a core 33,e.g. a ferrite core, is fixed at the ceiling of front recess 31 near to the above the front end 22' of leaf spring 19'. Thus, a measuring gap M' is formed between the front end 22' of leaf spring 19' and core 33. Beneath the front end 22' of leaf spring 19' a lamella 24 of hard material, such as ceramic oxide, is fixed on the bottom of front recess 31. In the bottom of rear recess 18' there is provided a yarn channel 28' extending beneath leaf spring 19' in the longitudinal direction of base body 16'.

As shown in Figure 2 for the inductive transducer 2, coil 32 may be connected to a highfrequency generator 10 and the thereto joined circuitry 11, 12 and 14. When the thickness of a yarn G passing between lamella 24' and front end 22' of leaf spring 19' changes, said front end 22' is moved up and down in a direction parallel to the axis of induction coil 32. These positional changes induce changes of the high frequency voltage over coil 32, in a similar manner as with the capacitive transducer illustrated above with reference to Figures 1,7,8and9.

Figures 13 and 14 show another measuring device in end view and front view, respectively, Base body 16" is substantially similar to base body 16 shown in Figures 7,8 and 9 and the adjustable mounting of the leaf spring 19", although not shown in these Figures, will be as shown in Figures 7 and 8. The body 16" differs from body 16 of Figures 7 to 9 in being additionally provided with extensions 8, 9 and 34 which support the various components 4,5 and 7, respectively, of an optoelectrical transducer. Leaf spring 19" has a front end 22", the edges of which are bent upward as to form a flat substantially U-shaped cross-section as may be seen from Figure 13. Above front end 22" and at a small distance therefrom, there is fixed a sheild 7 at shield support 34.Thus, a slot-shaped measuring gap M" is formed whose width h varies with the position of front end 22' in a perpendicular direction.

A lamella 24" is fixed on top of base body 16" beneath the front end 22". When a yarn G travels between lamella 24" and front end 22" of leaf spring 19", the width of measuring gap M" changes in an opposite sense to any change in the cross-sectional dimension of yarn G. The position of shield 7 in perpendicular direction is preferably adjusted such that the width h has a small positive value of one or some tenths of a millimeter for the thickest yarn places to be detected and measured. For this purpose, an adjusting device (not shown) may be provided for shield 7.

For sensing the width of measuring gap M" there are provided, on both sides thereof, a light source 4, e.g. a light emitting diode, and a photocell 5,e.g.a photodiode or a phototransistor. The whole of the measuring device is arranged such that ambient light is shielded from photocell 5 as far as possible.

Also with this embodiment, measuring gap M" is separated from the zone between contact member 22", 24" which is passed by the yarn.

In an alternative embodiment the yarn may pass through measuring gap M in a direction transverse to the longitudinal extension of the leaf spring 19.

Figures 15 and 16 represent an arrangement of contacting or contact members l9b, 24b of a sensor. A lamella 24b fixed at base body 16b forms one of the contact members.

Lamella 24b may be composed of three layers as is lamella 24, Figure 7. Leaf spring 19b is attached to a bearing bolt 29b which is rotatable about axis A. The front end 22b of leaf spring 1 9b has a flat substantially U-shaped cross-sectional and forms the other contact member. The yarn path F-F extends in transverse direction to the longitudinal extension of leaf spring 19b.

By rotating leaf spring 19b about axis A, front end 22b may be lifted from lamella 24b for the purpose of cleaning and checking and, moreover, the contact pressure exerted by front end 22b may be regulated within a broad range by such rotation. Thus, it is possible to adjust the mutual distance d of contact members 22b 24b within wide limits, for accommodation to the cross-sectional dimensions of the respective yarn G, so that very thin as well as very thick yarns can be measured.

With reference to Figures 17 and 18, a specific modification of the contact members of a sensing device comprises two leaf springs 19c, 19d whose front ends 22c, 22d contact the yarn. By way of example, one of these members 19c may be mounted fixedly, the other 19d rotatably at a base body (not shown). Rotation of member 19d about its mounting point will alter the contact pressure exerted on the yarn. For the purpose of mounting, bearing members 29c and 29c are attached to the rear ends of leaf springs l9c and 19d, respectively. In order to protect the upper or inner surface of the front end 22d against abrasion by the travelling yarn,said surface is provided with a protective layer 27d which may consist of ceramic oxide or other hard material and may be applied by plasmation.For the sake of clarity in illustration protective layer 27d is reproduced in Figures 17 and 18 on a scale substantially larger than the scale of the other parts. The front end 22c of leaf spring 19e has a transverse corrugation 27c so as to contact the front end 22d of the opposite leaf spring 1 9d or the protective layer 27d thereof along a line extending in the transverse direction of yarn path F-F. By this structure it is possible to also detect very short thick places of a yarn, such as knots and slubs, even when the yarn travels very fast. That means that the electrical sensing signal exhibits a high time resolution.

The device described can assess periodic small vibrations of transverse dimensions of yarns, which variations cannot be measured by known devices but are disturbing since they produce the socalled Moire effect in textile products.

The device described can be used in yarn travel monitors, yarn clearers, yarn evenness testing equipment or thread-bread stop mechanisms.

WHAT WE CLAIM IS: 1. A device for continously measuring a transverse dimension of a travelling yarn, the device comprising a base body; mechanical yam sensing means supported by the base body and including a fixed member and a movable member defining a yarn path between them, a leaf spring having an end mounted on the base body in such a way that the pressure exerted on the yarn by the leaf spring can be adjusted, the other end being free and integral with the movable member which is towards the fixed member by the spring; and means contactlessly co-operating with the free end of the leaf spring for detecting instantaneous deflections thereof and transducing them into electrical sensing signals.

2. A device as claimed in claim 1 ,wherein the leaf spring is arranged such as to exert a pressure of the order of one pond (gramme weight) onto the yarn.

3. A device as claimed in claim 1 or 2, wherein the leaf spring is mounted so as to be

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (12)

**WARNING** start of CLMS field may overlap end of DESC **. although not shown in these Figures, will be as shown in Figures 7 and 8. The body 16" differs from body 16 of Figures 7 to 9 in being additionally provided with extensions 8, 9 and 34 which support the various components 4,5 and 7, respectively, of an optoelectrical transducer. Leaf spring 19" has a front end 22", the edges of which are bent upward as to form a flat substantially U-shaped cross-section as may be seen from Figure 13. Above front end 22" and at a small distance therefrom, there is fixed a sheild 7 at shield support 34. Thus, a slot-shaped measuring gap M" is formed whose width h varies with the position of front end 22' in a perpendicular direction. A lamella 24" is fixed on top of base body 16" beneath the front end 22". When a yarn G travels between lamella 24" and front end 22" of leaf spring 19", the width of measuring gap M" changes in an opposite sense to any change in the cross-sectional dimension of yarn G. The position of shield 7 in perpendicular direction is preferably adjusted such that the width h has a small positive value of one or some tenths of a millimeter for the thickest yarn places to be detected and measured. For this purpose, an adjusting device (not shown) may be provided for shield 7. For sensing the width of measuring gap M" there are provided, on both sides thereof, a light source 4, e.g. a light emitting diode, and a photocell 5,e.g.a photodiode or a phototransistor. The whole of the measuring device is arranged such that ambient light is shielded from photocell 5 as far as possible. Also with this embodiment, measuring gap M" is separated from the zone between contact member 22", 24" which is passed by the yarn. In an alternative embodiment the yarn may pass through measuring gap M in a direction transverse to the longitudinal extension of the leaf spring 19. Figures 15 and 16 represent an arrangement of contacting or contact members l9b, 24b of a sensor. A lamella 24b fixed at base body 16b forms one of the contact members. Lamella 24b may be composed of three layers as is lamella 24, Figure 7. Leaf spring 19b is attached to a bearing bolt 29b which is rotatable about axis A. The front end 22b of leaf spring 1 9b has a flat substantially U-shaped cross-sectional and forms the other contact member. The yarn path F-F extends in transverse direction to the longitudinal extension of leaf spring 19b. By rotating leaf spring 19b about axis A, front end 22b may be lifted from lamella 24b for the purpose of cleaning and checking and, moreover, the contact pressure exerted by front end 22b may be regulated within a broad range by such rotation. Thus, it is possible to adjust the mutual distance d of contact members 22b 24b within wide limits, for accommodation to the cross-sectional dimensions of the respective yarn G, so that very thin as well as very thick yarns can be measured. With reference to Figures 17 and 18, a specific modification of the contact members of a sensing device comprises two leaf springs 19c, 19d whose front ends 22c, 22d contact the yarn. By way of example, one of these members 19c may be mounted fixedly, the other 19d rotatably at a base body (not shown). Rotation of member 19d about its mounting point will alter the contact pressure exerted on the yarn. For the purpose of mounting, bearing members 29c and 29c are attached to the rear ends of leaf springs l9c and 19d, respectively. In order to protect the upper or inner surface of the front end 22d against abrasion by the travelling yarn,said surface is provided with a protective layer 27d which may consist of ceramic oxide or other hard material and may be applied by plasmation.For the sake of clarity in illustration protective layer 27d is reproduced in Figures 17 and 18 on a scale substantially larger than the scale of the other parts. The front end 22c of leaf spring 19e has a transverse corrugation 27c so as to contact the front end 22d of the opposite leaf spring 1 9d or the protective layer 27d thereof along a line extending in the transverse direction of yarn path F-F. By this structure it is possible to also detect very short thick places of a yarn, such as knots and slubs, even when the yarn travels very fast. That means that the electrical sensing signal exhibits a high time resolution. The device described can assess periodic small vibrations of transverse dimensions of yarns, which variations cannot be measured by known devices but are disturbing since they produce the socalled Moire effect in textile products. The device described can be used in yarn travel monitors, yarn clearers, yarn evenness testing equipment or thread-bread stop mechanisms. WHAT WE CLAIM IS:

1. A device for continously measuring a transverse dimension of a travelling yarn, the device comprising a base body; mechanical yam sensing means supported by the base body and including a fixed member and a movable member defining a yarn path between them, a leaf spring having an end mounted on the base body in such a way that the pressure exerted on the yarn by the leaf spring can be adjusted, the other end being free and integral with the movable member which is towards the fixed member by the spring; and means contactlessly co-operating with the free end of the leaf spring for detecting instantaneous deflections thereof and transducing them into electrical sensing signals.

2. A device as claimed in claim 1 ,wherein the leaf spring is arranged such as to exert a pressure of the order of one pond (gramme weight) onto the yarn.

3. A device as claimed in claim 1 or 2, wherein the leaf spring is mounted so as to be

shiftable relative to the base body.

4. A device as claimed in claim 1 or 2, wherein the leaf spring is pivotably mounted on the base body.

5. A device as claimed in any one of claims 1 to 4, wherein the fixed member has a free surface exposed to the travelling yarn, and the movable member has a free surface facing said free surface of said fixed member.

6. A device as claimed in any preceding claim, wherein said transducing means is a capacitive transducer.

7. A device as claimed in claim 6, wherein the capacitive transducer electrodes fixed to said fixed and movable members.

8. A device as claimed in any of claims 1 to 5, wherein said transducing means is an inductive transducer.

9. A device as claimed in claim 8, wherein the transducer comprises an induction coil provided with a core and fixed to the base body for electromagnetically co < )perating with said movable member.

10. A device as claimed in any of claims 1 to 5 wherein the transducing means is an optoelectrical transducer.

11. A device as claimed in claim 10, wherein the transducer comprises a shield fixed to the base body adjacent said said movable member such as to provide a measuring gap between said shield and the movable member, and further comprising a light source on one side of said measuring gap and a photocell on the opposite side of the measuring gap.

12. A device for continuously measuring a transverse dimension of a travelling yam, substantially as herein described, with reference to any one embodiment shown in Figures 7 to 18 of the accompanying drawings.