Measuring instrument

Abstract: An instrument (10) is provided with several sensing elements (14, 15, 16) to enable several parameters of a processed yarn (12) to be measured or determined. In order to minimise the total sensing element/guide contact with the yarn (12) within the complete process threadline, the yarn (12) is guided through the instrument (10) by contact only with the inlet and outlet guiding elements (13, 17) of the instrument (10) and contact operative sensing elements (20). One particular instrument (10) consists, in succession, of an interlace sensing device (14), a tension sensing device (15) and an oil content sensing device (16). The electrical resistance of the yarn (12) is measured between two pins (20, 17) of the oil content sensing device (16) and in this case, the first pin (20) is also a tension sensing pin (20) of the instrument (10), and the second pin (17) of the oil content sensing device (16) is also the outlet guide (17) of the instrument (10).

Description: This invention relates to a measuring instruments for measuring the various parameters of a textile yarn, and in particular to instruments for measuring yarn parameters whilst the yarn is running through a textile machine during the processing of the yarn. There is a requirement to measure various parameters of a textile yarn during and subsequent to the processing of the yarn, to determine the efficiency and effectiveness of such processing and the quality of the processed yarn. To this end, there are many sensing instruments available, each adapted to measure a specific parameter. US 5768938 discloses a yarn sensing instrument that has no yarn contacting elements. WO 96 04100 discloses an instrument comprising an input guiding yarn driving device, an outlet guiding yarn driving device and in between these two driving/guiding devices a single yarn contacting tension sensing device. GB 2029023 also discloses a single yarn contacting tension sensing device disposed between input and output guides. A rotary guide intermittently pushes the yarn against the tension sensing device. A typical yarn process on POY or DTY may require the measurement of interlace, oil level and tension and the determination of the presence of broken filaments. To perform all of these measuring or sensing functions requires the use of at least three sensing instruments. Whilst some of the actual operative sensing elements may be non-contact, e.g. optical sensors, each sensing instrument requires two or more yarn contacting sensing elements and/or yarn guides to locate the running yarn in the sensor relative to the operative sensing elements. The result of adding three sensing instruments to a typical process threadline can add over 45° of sensing element/guide wrap, thereby undesirably increasing by a considerable amount the tension in the yarn downstream of those instruments. Hence the quality of the processed yarn is often compromised by the act of monitoring its quality. For this reason, and having regard to the high process speed with some processes, it is desirable or even essential to minimise the total sensing element/guide contact with the yarn within the complete process threadline. It is an object of the present invention to provide a yarn parameter measuring instrument which minimises the abovementioned problem. The invention provides a yarn parameter measuring instrument comprising an inlet yarn guiding element and an outlet yarn guiding element, and a plurality of sensing devices mounted successively within the instrument between the inlet yarn guiding element and the outlet yarn guiding element, each sensing device having at least one operative sensing element adapted to be responsive to a respective yarn parameter, wherein the yarn is guided through the instrument by contact only with the inlet and outlet guiding elements and contact operative sensing elements, the contact operative sensing element of one sensing device serving to guide the yarn to a successive sensing device. The instrument may comprise a yarn tension sensing device, having an operative sensing element which may comprise a tension sensing pin. The tension sensing pin may have stress measuring means secured thereto adapted to be responsive to the deflection of the tension sensing pin due to the tension in a yarn passing therearound. The stress measuring means may comprise at least one strain gauge secured to a stem which supports the tension sensing pin. The instrument may comprise an interlace sensing device having operative sensing elements which may comprise a laser beam generating device and a photo diode operable to receive the laser beam. The instrument may comprise an oil content sensing device, having a first operative sensing element which may comprise a first pin to which an electrical voltage is applied and a second operative sensing element which may comprise a second pin adapted to measure the voltage on the yarn to determine the electrical resistance of the yarn between the first pin and the second pin. The instrument may comprise, in succession, an interlace sensing device, a tension sensing device and an oil content sensing device. In this case the first pin may be the tension sensing pin, and the second pin may be the outlet guiding element. One embodiment of the invention will now be further described with reference to the accompanying drawing in which: Fig. 1 is a side view of a parameter measuring instrument, and Fig. 2 is a front view of the instrument of Fig. 1. Referring now to the Figures, there is shown a yarn parameter measuring instrument 10, having a housing 11 in which there is mounted in succession in the direction of passage of a yarn 12, an inlet guiding element 13, three sensing devices 14, 15 and 16, and an outlet guiding element 17 as described below. Sensing device 14 is an interlace sensing device which comprises non-contact sensing elements in the form of laser beam generating device 18 and a laser beam receiving photodiode 19, between which the yarn 12 passes from the inlet guiding element 13. The photodiode 19 senses changes in the width of the yarn 12 passing through the laser beam, and the resulting signal from the photo-diode 19 is representative of the presence or absence of interlace nodes in the yarn 12. Sensing device 15 is a tension sensing device which comprises a contact operative sensing element in the form of a tension sensing pin 20 having at least one strain gauge 21 secured to a stem 22 which supports the pin 20 in the housing 11. The signal provided by the strain gauge 21 is a measure of the deflection of the pin 20 under the tension of the yarn 12 passing in contact with it, and hence a measure of that tension. Sensing device 16 is an oil content sensing device which comprises two contact operative sensing elements in the form of a first pin 20 to which an electrical voltage, e.g. 200 V, is applied and a second pin 17 adapted to measure the voltage on the yarn 12 as it reaches the pin 17 to determine the electrical resistance of the yarn 12 between the pins 20 and 17. This resistance depends upon the oil content of the yarn 12, being high when no oil is present on the yarn 12 and reducing with increasing oil content. In this case the first pin 20 is the tension sensing element of the tension sensing device 15, and the second pin 17 serves also as the outlet guiding element 17. By means of the invention an instrument is provided which enables several parameters of a processed yarn 12 to be measured or determined. In the above described embodiment, interlace, tension and oil content are measured, but other parameters may be measured or determined in addition to or instead of the those parameters. In order to measure the three parameters as described above using separate instruments, two yarn guides/contact operative elements would normally be provided for each of the interlace and oil content measuring instruments, and three yarn guides/contact operative elements would normally be provided for the tension measuring instrument. These seven yarn guides/contacting elements could require at least 35° and probably over 45° of yarn wrap. In the present case however there are only three yarn guiding/contact operative elements requiring some 15° to 20° of yarn wrap, a reduction of 57%. This will lead to a considerable reduction in output tension in use of the instrument of the present invention by comparison with the use of three separate instruments, and hence considerably less detrimental effect on the quality processed yarn 12 as a consequence of monitoring that quality than has been the case in the past.

Claims: A yarn parameter measuring instrument (10) comprising an inlet yarn guiding element (13) and an outlet yarn guiding element (17), and a plurality of sensing devices (14, 15, 16) mounted successively within the instrument (10) between the inlet yarn guiding element (13) and the outlet yarn guiding element (17), each sensing device (14, 15, 16) having at least one operative sensing element adapted to be responsive to a respective yarn parameter, whereby the yarn (12) is guided through the instrument (10) by contact only with the inlet and outlet guiding elements (13, 17) and contact operative sensing elements (20), the contact operative sensing element (20) of one sensing device (15) serving to guide the yarn (12) to a successive sensing device (16). An instrument according to claim 1, characterised by a yarn tension sensing device (15). An instrument according to claim 2, characterised in that the yarn tension sensing device (15) has a contact operative sensing element (20) which comprises a tension sensing pin (20) and in that the tension sensing pin (20) has stress measuring means (21) secured thereto responsive to the deflection of the tension sensing pin (20) due to the tension in a yarn (12) passing therearound. An instrument according to claim 3, characterised in that the stress measuring means (21) comprises at least one strain gauge (21) secured to a stem (22) which supports the tension sensing pin (20). An instrument according to any one of claims 1 to 4, characterised by an interface sensing device (14). An instrument according to claim 5, characterised in that the interlace sensing device (14) has operative sensing elements (18, 19) comprising a laser beam generating device (18) and a photo diode (19) operable to receive the laser beam. An instrument according to any one of claims 1 to 6, comprising an oil content sensing device (16). An instrument according to claim 7, characterised in that the oil content sensing device (16) has contact operative sensing elements (20, 17) which comprise a first pin (20) to which an electrical voltage is applied and a second pin (17) adapted to measure the voltage on the yarn (12) to determine the electrical resistance of the yarn (12) between the first pin (20) and the second pin (17). An instrument according to claim 1, characterised by , in succession, an interlace sensing device (14), a tension sensing device (15) and an oil content sensing device (16). An instrument according to claim 9, characterised in that the oil content sensing device (16) has contact operative sensing elements (20, 17) which comprise a first pin (20) to which an electrical voltage is applied and a second pin (17) adapted to measure the voltage on the yarn (12) to determine the electrical resistance of the yarn (12) between the first pin (20) and the second pin (17), and in that the first pin (20) is a tension sensing pin, and the second pin (17) is the outlet guiding element (17).

Inventors: HINCHLIFFE MALCOLM GEOFFREY, HINCHLIFFE, MALCOLM GEOFFREY
Applicants: MERLIN PARTNERSHIP, THE MERLIN PARTNERSHIP
Application year: 1999
Main classification: G01N21
IPC codes: D02J1, B65H59, D06H3, G01N21