GB1585775A

GB1585775A - Method of and an arrangement for measuring indicating and/or recording the movement patterns or changes in path of moving machine parts

Info

Publication number: GB1585775A
Application number: GB34329/77A
Authority: GB
Original assignee: Wirkmaschinenbau Karl Marx Veb
Current assignee: Wirkmaschinenbau Karl Marx Veb
Priority date: 1976-08-17
Filing date: 1977-08-16
Publication date: 1981-03-11
Also published as: IT1116669B; ES461678A1; JPS5344069A; DE2730238A1

Description

(54) A METHOD OF AND AN ARRANGEMENT FOR MEASURING, INDICATING AND/OR RECORDING THE MOVEMENT PATTERNS OR CHANGES IN PATH OF MOVING MACHINE PARTS (71) We, VEB WIRKMASCHINENBAU KARL-MARX-STADT, of 73, Annaberger Strasse, 90 Karl-Marx-Stadt, German Democratic Republic, a Corporation organised under the laws of the German Democratic Republic, 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: This invention relates to a method of and an arrangement for measuring, indicating and/or recording the movement patterns or change in path of moving machine parts, for example of stitch forming elements in moving needle carriers.For example, the invention is applicable for measuring and recording the relative movement of the knitting needle in relation to the rotating needle carrier of a circular knitting machine or for measuring and indicating the adjustment of the stitching depth of the knitting needles.

The hitherto known solutions to the problem of measuring directly the position of the stitch forming part, for example by means of gauges, have the disadvantage that wear phenomena in respect of the stitch forming part and the play in the transmission gearing, and their effects on the stitch depth are not taken account of. Also known in general instrumentation technology are travel pick-ups which operate on inductive or capacitative principles. They consist of a measuring coll or a measuring capacitor, in which a core or a dielectric is located. In known constructions, these parts are accommodated inside a housing. The movement to be picked-up is transmitted to the movable parts through a rod projecting from the housing.The travel pick-up is connected by a cable to the evaluating instrument, ili which the variation in inductance or capacitance, as the case may be, is converted into an electrical signal, for example a voltage, proportional to the travel. A method of the further processing of this signal is not disclosed. The travel pick-ups are so designed that during measurement the housing is allowed to effect only movements which the connecting cable to the evaluating instrument permits. A direct loading of the measuring needle with the core of the inductive transmitter leads to a critical loading of the measuring needle and to false readings.Relative movements in respect of rotating machine parts, such as are effected by the knitting needles of circular knitting machines, could with these instruments only be measured by means of expensive and failure-susceptible slip-ring contacts between travel recorder and evaluating instrument.

The adjustment of machine elements, particularly of stitch forming parts, indirectly via the length of thread processed per unit of time admits of no unequivocal association of measurement results with the length of thread processed by just one of two needle carried in the circular knitting machine, the dial or cylinder. The method is expensive in terms of use of working media, labour and materials. Measurement and adjustment are not reproducible.

The invention aims, with minimum expenditure, to provide a portable measuring and evaluating instrument which offers measured value transmission to the measuring instrument without interference, even under production conditions, and provides a readable and reproducible measured value.

The invention is based on the problem of contactless measuring the movement of the stitch forming element in the moving needle carrier, transmitting it to an evaluating unit and obtaining the result of the measurement in a readable and/or recorded form.

Accordingly, the present invention consists in a method of measuring, indicating and/or recording patterns of movement or path changes of moving machine parts, for example the patterns of movement of stitch forming elements in moving needle carriers of knitting machines, using a measured value generator comprising a dielectric mounted on the moving machine part and a measuring capacitor arranged in the range of movement of the dielectric, and an evaluating unit associated with said generator, characterised in that a) the measured values are converted into frequency signals at the moving machine part b) the frequency signals are superimposed on a carner frequency c) the frequency-modulated signals thus obtained are transmitted wirelessly to a stationary evaluating unit d) the transmitted signal is demodulated by means of a discriminator, and e) the measured signal is made visible by means of an indicating apparatus.

The invention provides a measuring arrangement for indicating or permanently recording the relative movement of a machine part, particularly of a needle of a circular knitting machine, in relation to another likewise moving part, such as the needle carriers, without notably influencing the dynamic properties and pattern of movement of the machine part which is to be monitored. The invention makes it possible, without contact to measure the needle travel, to record it permanently and reproducibly and/or to indicate the extreme value of the needle movement at the stitch forming point as the stitching depth. The changes required at the needles of the knitting machine do not lead to any substantial increase in mass. The expenditure incurred for the measured value transmitter with which every machine is equipped is minimal.

The measuring device (evaluating unit) is portable and can therefore be used for sev eral machines. Measured values are transmitted without interference. An accurate and reproducible adjustment of the stitch forming part is possible independently of the thread intake measurements. Thus time spent and material lost in adjusting the machine are reduced. The invention may be utilized in a hosiery and knitted goods plant as well as in machine installations, and serves to save time and ensures precision in adjustment procedures. The knowledge of needle travel, made possible by the invention, including the irregularities caused by abrupt loadings and the necessary play is an essential prerequisite of evaluation of the needle-needle bed-cam system and the optimising of this system.

In an arrangement according to the invention, there is provided on the moving machine part a dielectric which, in use, projects between the plates of a measuring capacitor located in the range of movement of the machine part. By reason of the variation in capacitance proportional to the travel and produced in the measuring capacitor, it is possible to generate in a transmitting oscillator electrically connected to the measuring capacitor a travelproportional frequency change which can be transferred by the transmitter-oscillator via an antenna wirelessly as a frequencymodulated signal to a receiving antenna of a receiver of a stationary evaluating unit in which there are provided, for demodulation of the frequency-modulated signal and for reconverting it to a frequency-proportional current, an enumerating discriminator and also an operational amplifier serving to provide an appropriate input voltage for a counter mechanism or an indicating means.

In an arrangement according to the invention in a knitting machine one needle on each needle carrier is constructed as a measuring needle in that there is mounted thereon a dielectric in the range of movement of which, on the needle carrier, there is provided a measuring capacitor which forms one preferably battery-fed structural unit with a transmitter-oscillator the said unit being electrically connected to a flagshaped transmitter antenna at the least possible distance from which there is arranged on a stationary part of the machine a receiving antenna which is electrically connected to a likewise stationary evaluating unit.

Conveniently there is provided on the needle shank of the measuring needle a tag of dielectric material which projects into. a recess in the needle carrier, into which project the plates of the measuring capacitor, while the movement gap for the tag is retained.

Preferably, the electrical field in the gap of the measuring capacitor is narrowly confined spatially by a screening which encloses it with a fault-free gap and the tag projects through the gap in the measuring capacitor in the direction which is not involved in the measurement.

The receiver antenna may be circular in construction, mounted on the fixed machine part coaxially of the needle carrier axis and the flag-shaped transmitter antenna are disposed coaxially on the needle carrier at a short spacing from the receiver antenna.

The indicating device may be constructed as an indicating recorder, oscillograph with storage picture screen or as a loop oscillograph.

Finally, the counter may be electrically connected to a switch system and a clock oscillator.

In order that the invention may be more readily understood, reference is made to the accompanying drawings which illustrates diagrammatically and by way of example embodiments thereof, and in which: Fig. 1 is a cross-section through the needle carriers of a circular knitting machine; Fig. 2 shows a knitting needle constructed as a measuring needle; Fig. 3 shows a side view of a measuring capacitor; Fig. 4 shows a plan view of the measuring capacitor with equal-size capacitor plates; Fig. 4a shows a perspective view of the measuring capacitor with two different-size capacitor plates; Fig. 5 shows a circuit diagram of the measuring arrangement with an analog indicator, and Fig. 6 shows a circuit diagram of the .measuring arrangement with a digital indicator.

Referring to the drawings, the needles which effect a reciprocating movement and which are constructed as measuring needles 3 and 4 are shown on the respective needle carriers 1 and 2 (fig. 1) which are mounted for rotation about a common axis. Each measuring needle 3, 4 has an actuating butt 5, 6 acted upon by the operating surfaces of cams 7 and 8 respectively. Mounted on the needle shank 9 of each measuring needle 3, 4 by means of a connecting plate 10 (fig. 2) is a dielectric 11, which is constituted by a tag consisting of plastics material. This tag 11, projects into a recess 12, 13 disposed adjacent each measuring needle 3, 4 in the needle carrier 1, 2. In each recess 12, 13 is located a measuring capacitor 15, 14 which is mounted on the needle carrier 1, 2.Each measuring capacitor 14, 15 has two capacitor plates 16, 17 (fig. 4) arranged parallel to one another and which, within the range of movement of each tag 11, protrude into the recesses 12, 13 at a distance permitting the movement of the tag 11 between them. The electrical field in the gap in each measuring capacitor 14, 15 is spatially narrowly restricted by a screening 1 7a which encloses the capacitor plates 16, 17 with a field-free gap. The tag 11 projects, in the direction which is not important for measurement purposes, through the gap in the measuring capacitor 14, 15. This arrangement diminishes external interference influences and enlarges the linearity range. Each measuring capacitor 14, 15 is electrically connected to a transmitter-oscillator 18, 19 and forms one structural unit therewith.

This structural unit is mounted in a dovetail guide (not shown) in each needle carrier 1, 2 in which it can, by means of an adjusting spindle (not shown) be so adjusted that the needle movement takes place within the linear recording range, or alternatively each measuring capacitor 14, 15 is so adjustable that measurement can take place in a part of the needle curve as yet to be determined.

As a result of movement of the measuring needles 3, 4 during the knitting process, the engagement of the tag 11 into the gap between the capacitor plates 16, 17 due to the higher dielectric constant of the tag 11, the capacitance of the measuring capacitor 14, 15 is increased in proportion to the depth of engagement. Since it is intended only to register the longitudinal component of the movement of the measuring needles 3, 4 but not any transverse oscillations, the tag 11 projects through the gap in the measuring capacitor 14, 15 in a transverse direction.

Transverse movements of the tag 11 do not give rise to variation in capacitance. The travel-proportional variation in capacitance of the measuring capacitor 14, 15 produces a travel-proportional variation in frequency of the transmitter-oscillator 18, 19. The transistorised transmitter-oscillator 18, 1 9 is supplied by a pocket receiver battery 20, 21 constructed as a unit which can be inserted into the transmitter-oscillator 18, 19. By means of a trimming capacitor (not shown) the transmitter-oscillator 18, 19 can, at the midway position of the measuring needles 3, 4 be adjusted to 27.12 MHz. Needle movement causes this frequency to vary by a few thousandths of a millimetre.Since the measuring capacitor 14, 15 is a component part of the relevant associated co-rotating transmitter-oscillator 18, 19, thus its signal frequency is varied in proportion to the displacement of the dielectric 11. The sinusoidal frequency-modulated oscillator signal is transmitted wirelessly to the measured value processing part, the evaluating unit, of the plant. For this purpose, the transmitteroscillators 18, 19 are each electrically connected to a respective transmitter antenna 22, 23. The transmitting antenna 22, 23 is formed by a few square centimeters of sheet metal strip attached to the needle carrier 1, 2 in the immediate vicinity of a respective associated receiving antenna 24, 2 . The receiving antennae 24 and 25 are of circular construction. They are mounted on stationary parts of the machine, i.e. spindle 26 or head 27.The oscillator signal picked up by the receiving antennae 24, 25 is fed to a receiver 28, 29 (figs. 5 and 6). This receiver 28, 29 resembles conventional frequencymodulated receivers, but instead of the otherwise conventional radio detector, an enumerating discriminator is used to achieve demodulation of the frequencymodulated signal, which is characterised by high linearity and amplitude-modulated suppression. The receiver 28, 29 works on the superimposition principle. The frequency of the received signal is superimposed on a somewhat lower, quartzstabilised auxiliary frequency.

Within the signal preparation 30 (fig. 6), in known manner, the resultant intermediate frequency of a few hundred kilohertz is amplified, rectangularly formed by overmodulation and in an enumerating discriminator converted to a frequencyproportional current. A current-sensitive operational amplifier forms therefrom a corresponding voltage which is available at the output of the arrangement.

Sensitivity and frequency range can be adjusted at the receiver 28 and 29. This output voltage is then fed to a digital or analog indicating device in which the looping depth is indicated or a permanent travel-time diagram of the needle movement is depicted.

In order to measure the looping depth (fig. 4a and 6), the output voltage is fed to a synchronous forwards and backwards counter 31. Switches 32, 33 and 34 are associated with this counter 31. The effect of these switches 32 and 34 is that only the measuring frequency proportional to the needle movement is indicated and the oscillator drift is eliminated. In order to prevent erroneous measurements, whenever there is no frequency change between the switching timesof the switches 32 to 34, the counter 31 is reset by means of the switch 34. If there is a frequency change, the switch 34 remains ineffectual.

The switches 32 to 34 are actuated one after another. Furthermore, a signal derived from the switches 32 to 34 activate a clock oscillator 35 which is electrically connected to the counter 31 and which establishes the measuring time of the counter 31. Shortly before the looping zone is reached, in other words as long as the tag 11 is still outside the capacitor plates 16, 17 the basic frequency applied at this point in time only is counted in backwards into the counter 31 which is zeroed prior to commencement of the process. The actual measuring process is initiated at the looping point and the now available intermediate frequency, which consists of measuring frequency and basic frequency, is counted forwards in the same counter 31, so that as an end result it is only the measuring frequency which is present in the counter 31 and which is indicated in the indicator 36.By using one and the same counter 31 twice, it is possible to eliminate the influence of the oscillator drift on the result.

In a further example of embodiment (Fig.

5), the output voltage is fed to an oscillograph 37, for example an indicating recorder, in order to record the pattern of movement (travel-time diagram) of the measuring needles 3, 4 relative to their rotating needle carriers 1, 2. This oscillograph 37 is triggered once or line by line by a trigger signal by means of a switch 38 at the desired instant, the trigger signal being derived from the machine movement. This arrangement results in the effective travel of the measuring needles 3 and 4 being directly displayed.

The display is independent for the two needle carriers 1, 2 of the circular knitting machine or for one or more knitting system.

On the screen of the oscillograph 37 appears a permanent travel-time diagram which can be photographed to convert it into a durable record. Particularly suitable are indicating recorders, oscillographs with storage screens and loop oscillographs.

The latter provide a lasting diagram immediately, while with the first-mentioned equipment, such a diagram is provided only by photographing the screen display.

WHAT WE CLAIM IS:- 1. A method of measuring, indicating and/or recording patterns of movement or path changes of moving machine parts, for example the patterns of movement of stitch forming elements in moving needle carriers of knitting machines, using a measured value generator comprising a dielectric mounted on the moving machine part and a measuring capacitor arranged in the range of movement of the dielectric, and an evaluating unit associated with said generator, characterised in that a) the measured values are converted into frequency signals at the moving machine part b) the frequency signals are superimposed on a carrier frequency c) the frequency-modulated signals thus obtained are transmitted wirelessly to a stationary evaluating unit d) the transmitted signal is demodulated by means of a discriminator, and e) the measured signal is made visible by means of indicating apparatus.

2. In a machine an arrangement for measuring, indicating and/or recording patterns of movement or path changes of moving machine parts, characterised in that mounted on the moving machine part is a dielectric which, in use, projects between the plates of a measuring capacitor disposed in the range of movement of the machine part and in that the travel-proportional variation in capacitance produced in the measuring capacitor produces in a transmitter-oscillator connected electrically to the measuring capacitor a travel proportional variations in frequency which is, in use, transmitted by the transmitteroscillator through a transmitting antenna wirelessly as a frequency-modulated signal to the receiving antenna of a receiver of a stationary evaluating unit in which are arranged for demodulation of the frequency-modulated signal and for reconverting it to a frequency-proportional current, an enumerating discriminator and an amplifier which generates a corresponding input voltage for a counter or for an indicating device.

3. In a knitting machine, having stitch forming elements in moving needle carrier, an arrangement for measuring, indicating and/or recording pattern of movement of the stitch forming elements, characterised in that one needle on each needle carrier is constructed as a measuring needle in that there is mounted thereon a dielectric in the range of movement of which on the needle carrier, there is provided a measuring

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Claims

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analog indicating device in which the looping depth is indicated or a permanent travel-time diagram of the needle movement is depicted.

In order to measure the looping depth (fig. 4a and 6), the output voltage is fed to a synchronous forwards and backwards counter 31. Switches 32, 33 and 34 are associated with this counter 31. The effect of these switches 32 and 34 is that only the measuring frequency proportional to the needle movement is indicated and the oscillator drift is eliminated. In order to prevent erroneous measurements, whenever there is no frequency change between the switching timesof the switches 32 to 34, the counter 31 is reset by means of the switch 34. If there is a frequency change, the switch 34 remains ineffectual.

The switches 32 to 34 are actuated one after another. Furthermore, a signal derived from the switches 32 to 34 activate a clock oscillator 35 which is electrically connected to the counter 31 and which establishes the measuring time of the counter 31. Shortly before the looping zone is reached, in other words as long as the tag 11 is still outside the capacitor plates 16, 17 the basic frequency applied at this point in time only is counted in backwards into the counter 31 which is zeroed prior to commencement of the process. The actual measuring process is initiated at the looping point and the now available intermediate frequency, which consists of measuring frequency and basic frequency, is counted forwards in the same counter 31, so that as an end result it is only the measuring frequency which is present in the counter 31 and which is indicated in the indicator 36.By using one and the same counter 31 twice, it is possible to eliminate the influence of the oscillator drift on the result.

In a further example of embodiment (Fig.

5), the output voltage is fed to an oscillograph 37, for example an indicating recorder, in order to record the pattern of movement (travel-time diagram) of the measuring needles 3, 4 relative to their rotating needle carriers 1, 2. This oscillograph 37 is triggered once or line by line by a trigger signal by means of a switch 38 at the desired instant, the trigger signal being derived from the machine movement. This arrangement results in the effective travel of the measuring needles 3 and 4 being directly displayed.

The display is independent for the two needle carriers 1, 2 of the circular knitting machine or for one or more knitting system.

On the screen of the oscillograph 37 appears a permanent travel-time diagram which can be photographed to convert it into a durable record. Particularly suitable are indicating recorders, oscillographs with storage screens and loop oscillographs.

The latter provide a lasting diagram immediately, while with the first-mentioned equipment, such a diagram is provided only by photographing the screen display.

WHAT WE CLAIM IS:- 1. A method of measuring, indicating and/or recording patterns of movement or path changes of moving machine parts, for example the patterns of movement of stitch forming elements in moving needle carriers of knitting machines, using a measured value generator comprising a dielectric mounted on the moving machine part and a measuring capacitor arranged in the range of movement of the dielectric, and an evaluating unit associated with said generator, characterised in that a) the measured values are converted into frequency signals at the moving machine part b) the frequency signals are superimposed on a carrier frequency c) the frequency-modulated signals thus obtained are transmitted wirelessly to a stationary evaluating unit d) the transmitted signal is demodulated by means of a discriminator, and e) the measured signal is made visible by means of indicating apparatus.
2. In a machine an arrangement for measuring, indicating and/or recording patterns of movement or path changes of moving machine parts, characterised in that mounted on the moving machine part is a dielectric which, in use, projects between the plates of a measuring capacitor disposed in the range of movement of the machine part and in that the travel-proportional variation in capacitance produced in the measuring capacitor produces in a transmitter-oscillator connected electrically to the measuring capacitor a travel proportional variations in frequency which is, in use, transmitted by the transmitteroscillator through a transmitting antenna wirelessly as a frequency-modulated signal to the receiving antenna of a receiver of a stationary evaluating unit in which are arranged for demodulation of the frequency-modulated signal and for reconverting it to a frequency-proportional current, an enumerating discriminator and an amplifier which generates a corresponding input voltage for a counter or for an indicating device.
3. In a knitting machine, having stitch forming elements in moving needle carrier, an arrangement for measuring, indicating and/or recording pattern of movement of the stitch forming elements, characterised in that one needle on each needle carrier is constructed as a measuring needle in that there is mounted thereon a dielectric in the range of movement of which on the needle carrier, there is provided a measuring

capacitor which forms one battery-fed structural unit with a transmitter-oscillator, the said unit being electrically connected to a transmitter antenna, at the least possible distance from which there is arranged on a stationary part of the machine a receiving antenna which is electrically connected to a likewise stationary evaluating unit.
4. An arrangement according to claim 3, wherein mounted on the needle shank of the measuring needle is a tag of dielectric material, which protrudes into a recess in the needle carrier, into which recess projects the capacitor plates of the measuring capacitor, leaving a gap for movement of the tag.
5. An arrangement according to claim 2 or 4, wherein the electrical field in the gap of the measuring capacitor is spatially narrowly restricted by a screening which surrounds it with a field-free gap, and in that the tag projects through the gap in the measuring capacitor in a direction which is not involved in the measurement.
6. An arr?ngement according to any of claims 3 to 5 ,vherein the receiving antenna is of circular construction, is mounted on the fixed part of the machine coaxially of the needle carrier axis, and in that the taglike transmitter antennae are coaxially mounted on the needle carrier.
7. An arrangement according to claim 2, wherein the indicating device is constructed as an indicating recorder, oscillograph with storage screen or as a loop oscillograph.
8. An arrangement according to claim 2, wherein the counter is electrically connected to a switching system and a clock oscillator.
9. In a knitting machine, having stitch forming elements in moving needle carriers, an arrangement for measuring, indicating and/or recording pattern of movement of the stitch forming elements, substantially as herein described with reference to and as shown in the accompanying drawings.