US2950436A

US2950436A - Apparatus for controlling or checking the irregularity of a flow of textile or like materials

Info

Publication number: US2950436A
Application number: US652785A
Authority: US
Inventors: Butticaz Andre; Tesage Charles; Dembowski Heinz
Original assignee: Individual
Current assignee: Individual
Priority date: 1956-05-03
Filing date: 1957-04-15
Publication date: 1960-08-23
Anticipated expiration: 1977-08-23
Also published as: FR1150424A

Description

g- 1960 A. BUTI'ICAZ ETAL 2,950,436

APPARATUS FOR CONTRQLLING OR CHECKING THE IRREGULARITY OF AFLOW OF TEXTILE OR LIKE MATERIALS Filed April 15, 1957 I 4 Sheets-Sheet 1 f7 I 8 I YV/IVVEIYTOKS I 9. 46f flrvoe 5077/662 CH/QBLES 72-34 45 f/z-v/vz EMBOWJK/ f 454 C 8y JAW' if Aug. 23, 1960 A. BUTTICAZ ETAL 2, 5 ,4 6

APPARATUS FOR CONTROLLING OR CHECKING THE IRREGULARITY OF A mow OF TEXTILE OR LIKE MATERIALS 4 Sheets-Sheet 2 Filed April 15, 1957 Aug. 23, 1960 A. BUTTICAZ ET AL APPARATUS FOR CONTROLLING OR CHECKING THE IRREGULARITY OF A FLOW OF TEXTILE OR LIKE MATERIALS Filed April 15, 1957 4 Sheets-Sheet s Aug. 23, 1960 A. BUTTICAZ ETAL 2,950,436

APPARATUS FOR CONTROLLING OR CHECKING THE IRREGULARITY OF A FLOW OF TEXTILE OR LIKE MATERIALS Filed April 15, 1957 4 Sheets-Sheet 4 United States Patent APPARATUS FOR CONTROLLING OR CHECKING THE IRREGULARITY OF A FLOW OF TEXTILE OR LIKE MATERIALS Andr Butticaz, 45 Rue de la Bolle, Charles Tesage, 24

Rue Folmard, and Heinz Dembowski, 92 Rue de la The present invention relates to a method and apparatus for controlling or checking the irregularity of a flow of textile or like materials, with a view to measuring and/or recording the irregularities of strips, ribbons, wicks, threads, etc., made of textile material or other like materials.

The invention has also for its object to provide an indication and counting of the difference, either above or below, exceeding a pre-determined percentage with respect to a given mean value. I

An indication of this kind ofiers in particular the possibility of determining the frequency of an irregularity observed in a How of products resulting from a process of manufacture and to permit of the identification, for example, by means of measurement of the period or of the wave-length of the irregularity of the member or the stage of the manufacture which may be the cause.

The invention constitutes an application and a development of the method described in the U.S.A. patent specification filed October 1, 1956, under No. 613,099, for Process and Apparatus for Controlling a Flow of Textile Fibres or Similar Materials, and consisting essentially in causing the flow of material to be controlled between the two plates of a condenser and in measuring the increase in capacity of this condenser with respect to its value in the absence of the material: under certain conditions which are always obtained in practice, this variation in capacity is proportional to the mass'of textile or like material introduced between the plates of the measuring condenser. Mention has been made in the above-mentioned patent of the advantageous use of a differential condenser forming a measuring condenser and a reference condenser on each side of a central plate, in association with means known per se as a whole, to translate the variationsin capacity of the measuring condenser into a control signal. It is this same arrangement which has again been adopted in the scope of the present invention with a view to the formation of a regularimeter capable of checking the irregularity of a flow (thread, wick, strip, ribbon, etc.) of textile material or the like.

The method in accordance with the invention consists essentially in causing the flow of material to be controlled to pass at a constant but adjustable speed through a measuring condenser, in producing an electric out-ofbalance signal resulting from the comparison of the capacity of this measuring condenser with the capacity of a reference condenser, in comparing this out-of-balance signal with a signal which represents a mean reference value, and in controlling the variations of the differential signal resulting from this comparison and representing the irregularity.

In accordance with one method of procedure, a mean fixed pre-determined reference value is adopted corresponding to the nominal characteristics of the flow of material under control, and in this case any irregularity will be termed an absolute irregularity.

In accordance with a further method of procedure, a variable mean reference value is adopted corresponding to the mean real value of the signal obtained during a limited period of time preceding the instant of observation, and in this case the irregularity will be termed a relative irregularity.

Whether it is a question of absolute or relative irregularity, its instantaneous value may be observed and/or recorded in magnitude and in sign by means of appropriate instruments.

With a view to the determination of a mean value of the irregularity, a full-wave rectification is effected of the differential signal obtained by a comparison of the actual value of the signal with the mean value of reference, this rectification being followed by an integration of limited memory of the differential signal thus rectified. The result of this integration may be indicated in an intermittent manner at the end of each of a succession of discrete periods of integration, or again it may be indicated and/or recorded in a permanent manner.

These controls will preferably be completed by a detection with a view to counting and indicating the crossing, by the actual value of the differential signal representing the irregularity, of two pre-determined threshold values which are respectively positive and negative, the frequency of these crossings supplying information as to the frequency of the irregularity. Before being subjected to this detection of departure outside a range of values, the signal will preferably be filtered in a low pass filter with an adjustable cut-off frequency, which enables the elimination at will of variations in frequency greater than a certain value for a given speed of fiow.

The apparatus proposed for the purpose of carrying the method described into effect comprises in accordance with a preferred form of embodiment, a measuring cir cuit formed by a high frequency oscillation generator with a symmetrical output, a differential condenser comprising at least one measuring condenser and one reference condenser formed by two external plates arranged symmetrically on each side of a central plate, the outer plates being comiected to the terminal of the said generator, a tuned amplifier, means for applying to the input of this amplifier the out-of-balance potential of the said central plate, a detector connected to the output of the amplifier, and an interpretation apparatus comprising a continuous reference source of potential and means for controlling variations of the differential signal resulting from the comparison of the potential delivered by the said detector with the reference potential.

For the purpose of varying its gain, the amplifier will preferably be provided on the one hand with a manual regulating device and on the other hand with an automatic control device operating with a pre-determined time-constant, either the one or the other of these devices being put into use, depending on whether it is desired to observe the absolute or relative irregularity.

The interpretation device will preferably comprise a differential aperiodic amplifier with two input terminals which are respectively connected to the reference source and to the detector; the differential signal delivered by this amplifier will be passed in the first place to an indicating and/or recording instrument by means of which variations in irregularity can be observed, and in the second place to a rectifier-integrator intended to determine the mean value of the irregularity, and thirdly to a device for detecting, indicating and counting the passages of the irregularity beyond two threshold values, respectively positive and negative, and which are separately adjustable.

The special features and advantages of the invention will become further apparent from the description which follows below of a form of embodiment given by way of example, reference being made to the accompanying drawings in which:

Fig. 1 is a general diagram of the apparatus.

Fig. 2 is an explanatory diagram of the operations of measurement of irregularity.

Fig. 3 is a diagram relating to the operation of selec tion and counting of amplitude.

Fig. 4 is a perspective view of the measuring con denser.

Figs. 5, 6 and 7 are front views of the three first plates of this condenser.

Fig. 8 is a view in cross-section taken along the line VIIIVIII of Fig. 7.

Fig. 9 is a diagram showing the measuring circuit and the gain-control device of the amplifier.

Fig, 10 is a detail view in cross-section of a part of the amplifier casing.

Fig. 11 is a diagram showing the shape of the fre quency-response curve of the automatic gain-control device.

Fig. 12 and Fig. 12a taken together are an electrical diagram of the interpretation apparatus unit.

In accordance with the form of embodiment shown diagrammatically in Fig. l, and intended to control the irregularity of a strip, ribbon, wick or thread 10, the latter is caused to pass at a constant speed, by means of a pair of driving rollers 11, coupled to a motor (not shown), between the central plate 12- and one of the

outer plates

13, 14 of an air condenser of the symmetrical or differential type. Each of the

armatures

12, 13 and 14 is framed in known manner by corresponding keeperof antistr-ay plates 12', 13 and 14' held at the potential of the mounting frame and intended to make the electric field uniform between the plates by eliminating the edge effects. The

outer plates

13, 14 are connected by

symmetrical wires

15, 16 to the two terminals of a balanced output transformer 17 of an oscillator 18, the centre point 19 of the secondary winding of this transformer being connected to the earth of the assembly. 4

The central plate 12 is coupled through a coupling condenser 20 and a leakage resistance 21 to the input grid of a tuned amplifier 22. The output signal from this amplifier is simultaneously applied to the input of two

detectors

23 and 24. The detector 23 supplies an automatic gain-control 25 for the tuned amplifier 22. This gain may also be controlled by a manual regulation shown by the arrow 26. The detector 24 supplies an interpretation device, of which the unit is indicated by the reference 27.

The interpretation device comprises a differential amplifier 28, to the input of which is applied on the one hand the detected voltage from 24, and on the other hand a continuous reference potential or datum potential supplied by a source of reference 29. The differential signal resulting from this comparison is applied in the first place to an indicator instrument 30 with a central zero, enabling an instantaneous positive or negative value to be read at any moment.

The signal is applied in the second place to a rectifier integrator 31, to the output of which is connected an indicating instrument 32 with left-hand zero, enabling the mean integrated value to be read with a certain timeconstant of the said differential signal. The latter is finally applied in the third place to a device 33 known as an amplitude counter and comprising two

indicator lamps

34, 35 of different colours (red and green for example) and arranged so as to light the first lamp when the signal passes over a pre-determined and adjustable positive threshold value, and to light-up the second lamp when the signal passes over a negative threshold value which is also predetermined-and adjustable. p

Before beginning the detailed description of an example of construction of these various elements of the apparatus in accordance with the invention, and in particular of the interpretation device, with reference to Figs. 4 to 12, the method of measurement or control of the regularity will first of all be explained with reference to Figs. 2 and 3,

If a great length of thread, wick or ribbon is weighed per unit of length, centimetre by centimetre, for example, there is obtained a curve the general shape of which is that shown by the curve in full lines given in Fig. 2, in which P is the weight per unit of length, plotted as ordinates, and L is the length plotted as abscissae. By integrating a curve of this kind, or by dividing the total weight by the total length, a mean weight Pm can be determined; the straight line MM parallel to the axis of the abscissae, at an ordinate value Pm, would be the curve of a perfectly uniform thread of the same metric number. The metric number Nm is the term given to the quotient of the length in metres by the weight in grams; it is thus the reciprocal of the mean weight as defined above. By irregularity is meant the deviation of the real curve from the ideal straight line MM: it is thus essentially a variable quantity, changing in sign at a certain frequency, depending on the conditions of manufacture of or treatment of the thread, Wick, ribbon, etc

In accordance with the invention, it is proposed on the one hand to measure the mean value of the irregularity, and on the other hand to obtain information as to the frequency of its variations.

The o-ut-of-balance signal applied to the input of the amplifier 22 being proportional to the mass of textile or like material which is located at any instant between the plates of a measuring channel, the same thing will be true of the amplitude of the signal applied to the input of the

detectors

23 and 24 with the reservation that the potential delivered does not pass out of the range of linearity of the amplifier. The rectified voltage will, under these conditions, be subjected to variations in function of time corresponding to the curve in full lines as shown in Fig. 2, the time scale being obviously coupled to the scale of lengths L by the speed of passage adopted. By varying the gain of the amplifier in such manner that for a thread, strip or ribbon of mean weight Pm, the rectified voltage will be equal to the reference potential of the source 2 (see Fig. 1), it is seen that the instrument 3%) will indicate at every instant the instantaneous value of the irregularity as defined above, and this instrument may with advantage he graduated directly in percentages, on each side of the central zero.

The control of the gain of the amplifier may be effected either by hand or automatically. In the case of manual regulation, the gain is controlled in a fixed manner, using a previous calibration as a base, to a value such that the detected potential applied to the input of the differential amplifier 28 is equal to the reference potential of the source 29 for a predetermined nominal weight or metric number. The measurements of the irregularity will then be carried outwith respect to this predetermined nominal or theoretical weight, and it is this that will be termed an -absolute" measure of the irregularity.

In the case of automatic control of the gain by means of the circuit 25, the gain will be automatically controlled in such manner that thereal mean level of the detected potential remains constantly adjusted to the reference potential, the said mean level being established with a certain time-constant proper to the circuit 25, that is to say on the basis of an integration of the output potential with a limited memory. The measurements of the irregularity will then be effected with respect to this real mean weight measured over a certain length of thread, ribbon or strip, and it is this measurement which will be termed a relative measurement of the irregularity.

In the rectifier-integrator 31, the signal passing out of the differential amplifier 28 is first subjected to a fullwave rectification which supplies a quantity corresponding in Fig. 2 to the curve forming the upper contour of the shaded surface, this curve being obtained by reversing in symmetry with respect to the straight line MM, all the negative half-waves of the irregularity curve. By integration of this rectified signal, there is then obtained a mean level Em, and the ratio Em/Pm will represent the desired mean value of the irregularity, which will be preferably indicated directly as a percentage on the instrument 32 which is graduated from zero to 100%. This value will be an absolute mean value in the case of a manual control of the gain, fixing the straight reference line MM at a level corresponding to a predetermined theoretical nominal weight or metric number; it will be a relative mean value in the case of automatic gain control, in which case the straight reference line MM will in fact be replaced by a slowly-varying curve having ordinates which correspond at every instant to the real mean weight of a certain length of thread which has previously passed through the measuring condenser. v Finally, in order to obtain information on the periodicity of the irregularity, there is arbitrarily fixed a positive threshold B, (see Fig. 3) and a negative threshold value E with respect to the mean value MM and the periods of overrunning p p 11 n n n of these two respective threshold values will be observed. This operation is efiected in the device 33 known as an amplitude counter, the positive over-runs p and .the negative over-runs n being indicated respectively by the lighting of the two

lamps

34, 35. This device will preferably comprise a low-pass filter with an adjustable cutofl! frequency which enables the variations, the frequency of which exceeds the cut-off frequency to be eliminated for a given speed of passage and in consequence to smooth-down the curve examined to a corresponding extent.

Figs. 4 to 8 show a preferred form of embodiment of the measuring condenser. With a view to a better adaptation of the threads, wicks and ribbons, the condenser is provided with four measuring channels, of which two are for the threads. To this end, it is provided with nine plates 41 to 49, each separately fixed by means of screws on a base 50. Both plates and base are of electrolytic copper; the surfaces are polished and chromiumplated in order to prevent wear and corrosion, and to reflect thermal and light radiations.

As can be seen in Fig. 5 for example, with respect to the first plate 41, an internal zone such as 41a of small surface has been cut-out of each plate, this zone being insulated from the external zone 41'!) by a layer 410 of insulating low-loss material such as mica or trolitul for example. In each plate, the inner zone a forms a plate of the condenser, whilst the outer zone forms the corresponding keeper plate. The plate 42 thus forms the central plate and the

plates

41 and 43 are the two outer plates of a first differential condenser or first measuring channel. The plate 44 of smaller height than the preceding plates forms the central plate of a second differential condenser or measuring channel; it is enclosed between the

plates

43 and 45. The central zone 43a of the plate 43 thus forms an outer plate at the same time for the first and for the second measuring condenser; as shown in Figs. 7 and 8, it is cut-out with a bevelled edge, so that its face turned towards the plate 42a is higher than that turned towards the plate 44a, which is smaller than 4201. The same condition applies for the inside zone of the plate 45 which is associated at the same time with condensers No. 2 and No. 3, and for the inner zone of the plate 47 which forms part simultaneously of the condensers No. 3 and No. 4.

Figure 9 shows the diagram of the measuring and gain-control circuits.

Three

parallel wires

51, 52, 53 are stretched to form a flat surface in a hollowed-out portion formed for that purpose in the base of the measuring condenser (see also Fig. 10): the

central plates

42a, 44a, 46a and 48a are connected to the central Wire 51, whilst the outer plates are respectively connected to the

outer wires

52 and 53. Two

screws

54 and 55 can be passed at will either between the

Wires

51, 52 or between the

wires

51 and 53; the first is used for the zero setting or the balancing of the measuring condenser, whilst the other, when it is fully screwed home serves to produce a welldefined change in capacity for the purpose of calibration of the apparatus. This calibrating screw is normally unscrewed.

The oscillator comprising a tube 60 is of a standard type with a grid coil 61, a plate coil 62 tuned by a condenser 63 and a balanced coupling coil 64 having a centre point earthed. The working frequency is for example 100 kilocycles per second. The oscillator assembly is placed in a compartment 65 of a screened casing 66, of which a further compartment 67 contains theinput stage of the amplifier. The base 68 of the measuring condenser carries two threaded

rods

69, 70 which pass respectively into the compartments 65 and 67 inside insulating

guide tubes

71 and 72 respectively. The rod 69 carries a magnetic core 73 on which is formed the coupling coil 64. The tube 71 carries the grid coil 61 and plate coil 62 arranged round the coupling coil 64. The coupling coil 64 comprises a bi-filar winding, and it is connected by plaited connection wires 73 to the

outer wires

52 and 53 of the measuring condenser.

The central wire 51 of the measuring condenser is connected by a wire 74 to the coupling condenser 20, already referred to in connection with Fig. 1. This condenser is formed by a cylindrical condenser comprising an inner plate 75 carried on the threaded rod 70 by means of an insulating core 76, and an outer plate 77 carried on the insulating tube 72.

The base of the measuring condenser thus forms a single unit with its coupling members to the oscillator on the one hand and the amplifier on the other. The arrangement described ensures however a strict separation of the oscillator from the amplifier, avoiding all direct induction, both electro-magnetic and electro-static; it also avoids any very delicate direct contacts in the coupling zone, since an even very small change in contact resistance would result in phasing errors and in consequence in errors of measurement.

The construction of the amplifier 22 itself does not give rise to any special difficulty and will not be described in a detailed manner; although a relatively high gain is desirable, it is possible to avoid the necessity for frequency changing and to employ only a direct amplification. It will be necessary to take precautions in respect of the construction of the first stage, which should be decoupled in a particularly efiicient manner on the one hand with respect to high frequency, and on the other hand to suppress all the residual hum of the high tension, which will be stabilised. At the output, a push-pull stage will preferably be provided in order to feed the two

detectors

23 and 24 by means of a transformer 80 having two identically similar secondaries.

The cathode of the first amplifier tube 81 may be connected either to a fixed resistance 82 or to a group of three

potentiometers

83, 84 and 85. This changeover is effected by means of a change-over switch 1 with four blades and three positions a, b and c. The position a corresponds to the manual gain-control, the position c to automatic control, whilst the position b is an intermediate transition position. A resistance 86 arranged in parallel with the tube 81 and its load 87, formed in the usual manner by a circuit tuned to the frequency to be 7 amplified, forms with the

cathode resistance

82 or 83 to 85 a potential divider which tends to compensate for the effect on the gain of the first stage, of any possible variations of the anode potential, by a corresponding variation of the potential of the cathode.

It will be noted that in the manual gain control position (position a of the switch I), the control grid of the tube 81 is connected through the leakage resistance 21, the wire 88 and the wire 89 to the slider of the potentiometer 85. In the automatic control position (position 'c), it is connected by the wire 88 to the output of the filter with two resistance'capacity sections 91--92 and 9394, the input of which is then connected by the wire 95 to the negative terminal of the detector 23, whilst the positive terminal of this detector is connected by a wire 96 to the slider of a potentiometer 97 inserted in a series potentiometer group 98 connected between the high tension supply and earth. The wire 88 is connected on the other hand through a diode 99 to a point 90 of this group, which fixes a maximum limit (+4 volts for example) to the direct current potential of the grid.

The slider of the potentiometer 97 being fixed on the other hand at a higher potential which is known as the positive reference potential (of +65 volts for example), it can be seen that the potential applied to the input of the filter is the result of the comparison of the detected potential with this reference potential.

In the position b of the switch I, the resistances 91 and 93 are short-circuited and the filter is reduced to two condensers 9'2. and 94 in parallel: the change-over to this position enables the

condensers

92 and 94 to be instantaneously charged and thus avoids useless waiting periods. In the position 0, the filter is inserted between the input wire 95 and the output wire 88. A damping resistance 100 arranged in series with the first condenser 92 serves to attenuate the resonance by positive reaction which tends to be produced at a certain value of frequency, by reason of the double de-phasing effect.

Fig. 11 shows the shape of the response curve obtained under these conditions: the magnitudes plotted in abscissae are the frequencies of the variations of the amplitude of the input signal, that is to say variations in the capacity of the measuring condenser resulting from variations in the thickness of a thread, for example, whilst as ordinates there have been plotted the relative values at which these same variations are found at the output side of the amplifier. It can be seen that the effect of very slow variations (low frequencies) is completely suppressed by the regulation; that there is then an intermediate zone in the vicinity of the opening frequency f of the filter, a resonance zone r of slightly higher value, and a progressive transition to the normal zone at which the variations of the output signal faithfully reproduce those of the input signal. By introducing the notion of wave-length of the variations in irregularity of the thread or ribbon under study, that is to say the ratio of the speed of passage to the frequency of the variations, it can be said that the automatic regulation causes the suppression of the effect in the output signal of the variations of long-waves lengths, that is to say of wavelengths definitely greater than a wave-length of cutofi; it is clear that this wave-length of cut-off is proportional,'for a given thread, to the speed of passage and that, in consequence, by increasing this speed, it is possible to progressively cause to appear in the output signal variations which are slower and slower and the effect of which was previously suppressed.

These considerations :show a further aspect of the difference between the absolute measurement and the relative measurement of the irregularity: with the absolute measurement (manual gain regulation) all the variations appear both slow and rapid; the relative measurement (automatic gain regulation) suppresses the variations having frequencies lower that the opening frequency f0 "of the filter forming the regulation circuit, or in other 8 words, the variations in wave-length greater than the Wave length corresponding to cut-off. This Wave-length being however proportional to the speed of passage, an increase in this speed will have the effect of bringing closer together the relative measurement and the absolute measurement.

The description can now be given of one form of em bodiment of the interpretation device itself, with reference to the diagram shown in Fig. 12. The rectified potential delivered by the detector 24, represented by U is compared with a positive reference potention U0, taken froma potentiometer group 101 provided for that purpose between the positive of the stabilised high tension supply and earth. A series of calibrated resistances 102 to 105, connected between the output of the detector and the tapping 106 on the potentiometer group, enables he whole or a fixed fraction of the differential potential U-U0 to be taken-off by means of a rotary switch 107, and thus to obtain various sensitivities of measurement. Thus, for example, in the first position marked 12.5%, the Whole of the said potential is taken-off through the intermediary of a series protecting resistance 108; in the position 25%, one-half; in the position 50%, onequarter, and in the position one eighth of the said potential. The two last positions R and B are used in the calibration operations of the apparatus.

The signal taken-oil by the switch 107 is transmitted by the intermediary of a low-pass resistance-capacity filter 109110, which can be put partly or wholly out of action by means of a double change-over switch II with three positions: in the position a, the filter is out of action (condenser open circuited, resistance short-circuited); in the position b, the resistance remains short-circuited, but the condenser is in circuit and in practice absorbs the very rapid variation; in the position 0 the entire filter is inserted and produces a damping of the frequencies greater than its cut-off frequency; this facilitates a search for the mean on long wave-lengths. I

The signal taken from the output of this filter passes through one of the four contacts of a four-pole switch with two positions (a, b) or reversing switch III in order to be brought by a wire 111 to the control grid of a differential amplifier 28 with two tubes 113, 114 connected as a cathode-follower circuit; the signal is collected at low impedance between the cathodes at 115 and 116, at the head of two

load resistances

117, 118 of equal values. The grid of the second tube or reference tube 114 is connected to the slider of a potentiometer 119, connected in parallel to the bridge 101 on each side of the reference potential tapping 106.

In position a of the reversing switch III, the indicator 30 with a centre Zero is connected between the

points

115 and 116, and in the position b of the said reversing switch; the indicator 32 with left-hand zero or integration indicator is connected between the

same points

115 and 116 Suitable

variable resistance

121, 122 are respectively connected in series with these two instruments. In addition, there is permanently connected between the

output terminals

115 and 116 of the amplifier a branch containing a variable resistance 1'23 and a jack 124 intended to permit of the connection of a recorder by means of a plug. The resistance 123 is short-circuited when the plug is engaged in the jack and replaces the recorder when the latter is disconnected, so as to avoid a modification of the total impedance coupled between the terminals .115 and 116.

The signal available between the

terminals

115 and 116 of the differential amplifier is on the other hand simultaneously applied to the input of the rectifier-integrator 31 and to a device known as the amplitude-counter, the whole of which is indicated by the reference 33.

The rectifier-integrator 31 comprises essentially a bridge of diodes 13 2 intended to charge an integrating condenser 134 (of'2 microfarads for example) by the full-wave rectifled signal potential, through the intermediary of a load resistance 133 of very high value (20 megohms for example). The load resistance is shunted by a push-button 135 which enables the condenser 134 to be charged or discharged instantaneously during a checking of the calibration. In parallel with the integration circuit 133-134 is connected an auxiliary source of voltage 136, of 20 volts for example, in series with a resistance 137 of 2 megohms for example. This auxiliary circuit is provided in order to make the discharge resistance practically equal to the charge resistance, this being an essential condition in order to obtain a correct integration, that is to say a good linearity and a very low threshold of excitation. The integration is effected with a memory limited to periods of the order of the time-constant, or forty seconds with the values given by way of example. For long lengths of thread, a number of successive integrations will thus be carried out, separated by periods of about thirty seconds for example.

After each integration period, the reversing switch III is turned over to the position b, which has the effect of changing-over the positive plate of the integrating condenser 134 to the slider of a potentiometer 120 connected in parallel with the potentiometer 119, and its negative plate to the grid of the tube 113: the instrument 32 is substituted at the same time for the instrument 30, and its deflection indicates the mean level of the irregularity during the period of integration considered.

The amplitude-counting device 33 comprises at its input a variable loss-pass filter 140141 which has a cut-off frequency variable between certain limits, so that the variations of frequency greater than this cut-off frequency will be eliminated from the signal passed to the counter. The signal having passed through this filter is applied through the medium of a protection resistance 142 to the slider of a potentiometer 143 forming part of a potentiometer chain connected across the terminals of an auxiliary polarising source 144, of about 20 volts for example. Two

other potentiometers

145 and 146, forming a second chain at the terminals of the source 144 have their sliders connected to the grids of two thyratrons 147 and 148 through the intermediary of the

respective coupling resistances

149 and 150.

Condensers

151 and 152 are connected on the other hand between the grid and the cathode of each of the thyratrons. The latter are supplied between cathode and anode by a source 153 of alternating-current potential and are loaded respectively by the

relay windings

155 and 156, shunted in the usual manner by a condenser-

resistance combination

157, 158.

The contacts of the

relays

155 and 156 control, one at rest and the other in the Working position, the lighting of the

respective lamps

34 and 35, one of which is intended to indicate the passage above and the other the passage below two given threshold values. These two lamps are supplied from an alternating source 159 of 6.3 volts for example. The relays operate in addition the

respective counters

161 and 162.

Finally, a switch 160 is arranged between the input of the device and earth: when this switch is closed, a highly negative potential is applied to the grids of the thyratrons (the cathodes of which are brought up to the potential of the output 116, or +60 volts for example), so that the counting is then stopped.

As the thyratrons become active at a certain negative value of the biasing potential of their respective grids, thjere results an asymmetry between the behaviour of the two thyratrons, which is compensated for by means of the potentiometer 143; in other Words, this potentiometer serves to ensure the symmetry of behaviour of the two thyratrons with respect to a zero input voltage corresponding to the reference line MM of Fig. 3. The

potentiometers

145, 146 serve on the other hand to fix respectively the passage of the lower threshold E2, below which the relay 155 operates to light the lamp 35, and the passage of the upper threshold E1, above which the relay 156 operates to light the lamp 34.

It is known that the operation of thyratrons supplied on the anode with alternating current and controlled at the grid by a continuous or slowly varying potential, is unstable in a circuit of the kind employed here: the firing curve is actually displaced, depending on the value of the direct current potential at the terminals of the condenser which shunts the anode load, and this results in hunting. This drawback is avoided in this case by means of the resistance-capacity sections 149151 and 150 152, which play the part of stabilisers. By a suitable choice of the time constant of these sections, an excellent regularity of operation is obtained, the difference between the firing and extinction thresholds being reduced to about 0.5 volt for example, for an anode potential of volts R.M.S. The time-constant of the stabilising sections will be of the order of magnitude of the period of the alternating potential of the anode supply. The results indicated above were obtained, for example, with a supply at 50 cycles per see. with

resistances

149, 150 of 10 megohms and

condensers

151, 152 of 2,000 micromicrofarads.

The form of embodiment which has just been described is simple and economical in construction and has the additional advantage of being very easy to use. In particular, it lends itself to a calibration and re-calibration which is both rational and simple, so that the operator himself can regularly carry out a check of the calibration and even a complete re-calibration which may be made necessary from time to time by the inevitable wear of the electronic tubes. In this way, returning the apparatus to the works and visits of technicians are avoided, both of which are costly and useless, since the complete calibration can be carried out in a time of the order of one minute.

Calibration comprises the following operations:

After checking and when necessary correcting, in the usual manner the,zero settings of the indicating instruments and also the supply voltages, the rotary switch 107 (Fig. 12) is first of all placed in the position B, and the change-over switches I, II and III in the position a. The reference potential is then applied to the input of the differential amplifier 28. By acting on the potentiometer 119, the needle of the indicator 30 is brought back to Zero. The push-button is then depressed for half a second, to short-circuit the load resistance 133 of the integrating condenser and ensure the discharge of the latter, the reversing switch III is then changedover to the position b; as the instrument 32 should then indicate zero, its deflection is adjusted by acting on the potentiometer 120.

The rotary change-over switch 107 is then put into the position R (equivalent to the position 100%); in the absence of a signal, the centre-zero instrument 30 should then indicate -100%. This deflection is adjusted by acting on the series resistance 122. By depressing the short-circuited button 135, the instantaneous charge of the integrating condenser 134 is ensured at the maximum potential corresponding to 100% irregularity: after having turned the reversing switch III into the position b, the series resistance 121 is adjusted, if this is necessary, so as to bring the instrument 32 to the corresponding deflection, after which the reversing switch III is brought back to the position a.

The manual gain control potentiometer 84 (see Fig. 9) is provided with a regulating dial graduated in usual values of metric number or of nominal weight of thread, strip, ribbon, etc., depending on the applications considered. This is placed on a reference mark corresponding to the minimum nominal weight or maximum metric number provided for. The zero-setting screw or balancing screw 54 of the measuring condenser is then regulated so as to bring the needle of the irrggurality indicator 30 to the position l00%: this amounts to the same thing as adjusting the balance of the measuring condenser in the absence of material under test. The calibrating screw 55 is then introduced fully into the screwed hole provided for that purpose; the change in capacity produced by this calibrating screw replaces the change in capacity which would be caused by a standard of textile or like material, since it is not possible to establish a durable standard of such material. The other potentiometer 83 of the manual gain control device is then adjusted so as to bring the needle of the indicator 30 into the position +100%.

Still keeping the calibrating screw fully engaged, the dial potentiometer 84 is brought into another position marked for that purpose, and for which the third potentiometer 85 of the manual gain-control device is adjusted so as to bring the needle of the instrument 30 onto a corresponding mark situated at 80% for example. The calibrating screw is then disengaged.

t only remains to adjust the reference potential employed in the automatic gain-control circuit, in opposition to the potential detected by the detector 23, that is to say the position of the slider of the potentiometer 97 (see Fig. 9). For this purpose, there is introduced for example a thread of average metric number into the measuring condenser, and the rotary change-over switch (Fig.

12) is put into the position of maximum sensitivity (12.5% for example); the potentiometer 97 is then adjusted so as to bring the needle of the indicator 30 opposite its central zero. It is thus made sure that the automatic gain-control device really tends to regulate the potential delivered by the detector 24 to a value equal to the reference potential U which is employed at the input of the interpretation device.

The calibration is then finished and the apparatus is ready for use. It can be seen that the various adjustments are entirely independent one from the other, that is to say they have no mutual influence on each other. This particularly useful property enables, in addition, an arrangement to be employed such that the various regulating and adjusting members on the control panel of the apparatus are each disposed either opposite the reference mark as a function of which it is to serve, or is characterised by a colour matching with that of this mark; these two methods may of course also be combined. Thus, for example, the spindles of the

potentiometers

83 and 85 which will be operated by a screwdriver will be placed opposite the two respective reference marks of the scale of the potentiometer 84, on to which this latter has to be brought during the corresponding adjustments; the spindles of the potentiometer 119 and of the rheostat 112 will be placed respectively opposite the positions B and R of the rotary change-over switch 107 opposite which the knob of this switch should be placed during the corresponding adjustment, etc.

It will be appreciated that this arrangement still further facilitates the operation of calibration and enables all risk of error or confusion to be avoided.

The invention is of course not limited to the forms of enbodiment chosen and shown, these having been given by way of example only; the invention may, on the contrary be given various alternative forms which will be clearly apparent to those skilled in the art, both as concerns the construction of the condenser and the measuring circuit and also that of the interpretation device itself.

What We claim is:

1. In an apparatus for determining the irregularity of a continuous flow of textile or like materials, the combination comprising, a differential condenser having a central plate electrode, an external plate electrode symmetrically disposed on each side of said central electrode, so as to form a measuring condenser and a reference condenser; means for passing said continuous flow between the central plate electrode and the external plate electrode forming said measuring condenser; an oscillator having a central output terminal and two external output terminals which are symmetrical with respect to said central terminal; a measuring circuit, to determine the difference between the capacities of said measuring and reference condensers, comprising said oscillator, said differential condenser, an output impedance element, means for symmetrically connecting one of said external terminals of said oscillator to said external plate electrode forming said measuring condenser and the other of said external terminals of said oscillator to said external plate electrode forming said reference condenser, and means for connecting said output impedance element to said central plate electrode on the one hand and to said central output terminal of said oscillator on the other hand; a tuned amplifier; means for connecting the input of said amplifier across said impedance element; a detector coupled to the output of the said amplifier; an interpretation device comprising a source of continuous reference potential and means connected to the output of said detector, including means for comparing the reference signal and the signal at the output of said detector to produce a differential signal, and means for determining the variation of said dilferential signal.

2. An apparatus as claimed in claim 1 in which the differential condenser associated with the said measuring circuit is a multiple condenser comprising a plurality of differential units, each comprising a measuring condenser and a reference condenser formed respectively on each side of a central plate electrode; the said central plate electrodes decreasing in surface area along one direction of the plurality of units composing the said multiple differential condenser; the outer plates respectively disposed on each side of the said central electrodes each having a greater surface area than that of the corresponding central electrode, thereby forming a plurality of measuring channels having dimensions adapted to receive a range of possible dimensions of the materials to be examined.

3. An apparatus as claimed in claim 1, in which the plate electrodes of the said differential condenser each comprises plate electrodes fixed in and forming part of larger plates from which the said electrodes are insulated with a layer of low-loss insulating material, the outer plate portions acting as anti-fringing plates to prevent electrostatic fringing-field effects at the edges of the same plate electrodes.

4. An apparatus as claimed in claim 1, in which the differential condenser of the said measuring circuit is formed by a plurality of metal plates of generally rectangular shape, each fixed as a bridge above two longitudinal walls of a base, also of metal, an internal c0- planar portion of each plate forming a condenser plate electrode separated by a layer of low-loss insulating material from the remaining external portion, the latter portion serving as an anti-fringing plate around the periphery of the said condenser plate and being electrically connected to earth through the said base, the said plurality of plates being an odd number, the end plates and each odd-numbered plate forming the external plates, and the even-numbered plates forming central plate'electrodes of decreasing dimensions, at least one of the peripheral edges of each internal plate portion which forms the common external plate between two successive central plate electrodes being cut with a bevel edge in order that its outer surfaces may be in correlation with the corresponding facing surfaces of the said central plates.

5. An apparatus for determining the irregularity, of a continuous flow of textile or like materials, the said apparatus comprising in combination: a measuring circuit including a high-frequency generator with a symmetrical output: a tuned amplifier; a multiple differential condenser associated with the said measuring circuit; said multiple condenser comprising; a metal base member; an odd number of metal plates of generally rectangular shape, each fixed as a bridge above two longitudinal walls of the said base; an internal portion of each plate forming a condenser electrode, separated from the remainder of aesas said plate by a layer of low-loss insulating material; means for earthing the external portion of each said plate; each odd-numbered electrode forming the external plate electrodes and the even-numbered plates forming the central electrodes of a plurality of geometrically symmetrical differen'tial condenser units, the said central electrodes decreasing in surface area along one direction of the said multiple condenser; means for passing the flow of material to be examined between the plates of one side of the said differential condenser; a screened chassis divided into two compartments, the said tuned amplifier being housed in one of the said compartments and the said oscillation generator in the other said compartment; two lateral edges of the said differential condenser base fixed on the upper part of the said screened chassis; two threaded rods screwed into said lateral edges and passing each into one of the said screened compartments; means for mounting respective coupling members of said differential condenser on said threaded rods, thereby forming an assembly which is movable as a unit within the base of the said condenser, said coupling members being adapted to connect respectively the said oscillator to the external electrodes of said differential condenser and the central electrodes of said differential condenser to the input of said amplifier; and an interpretation device connected to the output of said amplifier for determining the variations of the signal at this output.

6. Apparatus as claimed in claim 5, and further comprising: three wires stretched longitudinally in a plane surface between insulated fixing points inside the said condenser base; means for connecting the outer wires to the outer plates and the central wire to the central plates of said differential condenser, the said wires being connected to the corresponding coupling members in the said screened chassis and thus forming part of the means for connecting to said differential condenser the said oscillator and amplifier; a transverse wall provided in said condenser base; two threaded holes formed in said wall so as to introduce a balancing screw for the differential condenser between the central wire and one of the outer wires, and a calibrating screw between the central wire and the other outer wire, the introduction of the said calibrating screw causing a pre-determined variation of capacity, the said screw being normally in the disengaged position.

7. An apparatus as claimed in claim 1, in which the said tuned amplifier comprises: a manually-operated gaincontrol device and an automatic gain-control device, acting with a predetermined time-constant; and switching means for putting one or the other of the said devices into operation at will, depending on whether it is desired to determine the absolute irregularity or the relative irregularity.

. 8. An apparatus as claimed in claim 1, in which the said tuned amplifier comprises: a manually-operated gaincontrol device and an automatic gain-control device, acting with a' predetermined time-constant; and switching means for putting one or the other of the said devices in operation at will; the said manually-operated gain-control device including a group of three potentiometers connected in the cathode-return circuit of the input tube of the said amplifier, namely: a first potentiometer connected as a rheostat and having its position-indicating member asso-' ciated with a dial graduated in pre-determined values of nominal weight or metric number for example, of the flow of material to be examined; a second potentiometer connected in parallel with the first potentiometer and having its slider coupled to the return connection of the control-grid of the said input tube, the said slider being set during the calibration of the apparatus; and a third potentiometer connected as a rheostat in series with the said first and second potentiometers, and also intended to be set during the calibration of the apparatus. I

9. An apparatus for determining the irregularity of a continuous flow of textile or like materials, the said apparatus comprising in combination: a differential cori denser comprising a central plate electrode, an external plate electrode symmetrically disposed on each side of said central electrode to form a measuring condenser and a corresponding and geometrically symmetrical reference condenser, means for passing said continuous flow between the central plate electrode and the external plate electrode forming said measuring condenser; a high frequency oscillation generator with a symmetrical output circuit: a measuring circuit to determine the difference between the capacities of the said measuring and reference condensers, comprising said generator, said differential condenser, means for connecting said external plate electrode to said output circuit of said generator, an output terminal and means for connecting said central plate electrode to said output terminal; a tuned amplifier connected to said output terminal of said measuring circuit and comprising a manually operated gain-control device and an automatic gain-control device acting with a predetermined time-constant; switching means for selecting one or the other of said devices at will: a detector .coupled to the output of said amplifier; a source of reference potential; means for comparing the signals from said detector and the said source; and an interpretation device fed by the differential signal resulting from the comparison of the signal from said detector with the said reference potential.

10. An apparatus as claimed in claim 9, in which the said automatic gain-control device includes a reaction circuit formed by a low-pass filter; a further detector connected to the output of the said amplifier in parallel with the detector supplying the interpretation device; and a further source of continuous reference potential connected in series with the said further detector, to the input of the said reaction circuit.

11. An apparatus as claimed in claim 9, in which, in the automatic gain-control position, the said tuned amplifier comprising an input tube with a grid and a cathode, and the said automatic gain control device including a reaction circuit, the said switching means couples the grid-return of the input tube to the output of the reaction circuit, and the cathode of the said tube over a fixed cathode-return resistance, the output of the reaction circuit being further connected through a diode to a source of positive potential, in order to fix an upper limit for the potential applied to the control-grid of the said input tube.

12. An apparatus as claimed in claim 9, in which the said automatic-gain-control device comprises a reaction circuit formed by a low-pass filter, a further detector connected to the output of the said amplifier in parallel with the detector supplying the interpretation device, and a source of continuous reference potential connected in series with the said further detector to the input of the said reaction circuit, the said'low-pass filter being of the resistance-capacity type with two sections, a damping resistance being provided in series with the capacity branch of at least one of the said sections.

13. An apparatus as claimed in claim 12, in which the said switching means is constituted by a multiple switch having a third intermediate position between the manual and automatic control positions, in which third position the resistances of the said filter are short-circuited so as to enable an almost instantaneous charge of the condensers of the filter to be effected during the transition from manual to automatic control.

14. An apparatus for determining the irregularity of a continuous flow of textile or like material, the said apparatus comprising in combination: a differential condenser comprising: at least one central plate electrode; at least one plate electrode symmetrically disposed on each side of each said central electrode, so as to form at least one measuring condenser and at least one reference condenser; means for applying high frequency potentials of a given frequency, equal amplitudes and opposite.

phases to the outer plates of each said differential condenser; a tuned amplifier; means for applying the potential of the said central plates to the input of the said amplifier; a detector coupled to the output of the said amplifier; an interpretation device comprising a source of continuous reference potential and an aperiodic differential amplifier with two input terminals connected one to the output of the said source of reference potential and the other to the output of the said detector, indicator means connected to the output of said differential amplifier, and further comprising a low-pass filter which is capable of being short-circuited and is disposed in front of the input of the said differential amplifier.

15. An apparatus as claimed in claim 14, in which the output of the said differential amplifier is coupled to an indicating instrument graduated directly in percentages and with a centre zero, in order to determine both the magnitude and the sign of the diflferential signal, the calibration of the said instrument bing effected for its extreme deflections, on the one hand by annulling the output voltage of the detector and, on the other hand, by the insertion of a calibration screw into the measuring condenser.

16. An apparatus as claimed in claim 14, in which said indicator means include a rectifier-integrator comprising a full-wave rectifier-bridge and an integration circuit comprising an integrating condenser and a high load resistance, the input of said rectifier bridge being connected to the output of said differential amplifier, said integration circuit being connected across the output of said rectifier bridge, the apparatus also comprising means for temporarily disconnecting said integrating condenser from said integration circuit and connecting it to the first said input of said difierential amplifier.

17. An apparatus as claimed in claim 16, in which the said integration circuit is shunted by a discharge circuit comprising an auxiliary source of direct current potential having a polarity such that it tends to discharge the integrating condenser, and a resistance of the order of onetenth of the said load resistance, with the further provision of a push-button enabling the load resistance to be temporarily short-circuited.

18. An apparatus as claimed in claim 14, in which the output of the said differential amplifier is connected to an indicator instrument with a centre zero, and further comprising a switch for changing-over the output of the said amplifier to the terminals of an integrating condenser, and simultaneously to substitute an indicating instrument with a left-hand zero for the said centre-zero instrument.

19. An apparatus for determining the irregularity of a continuous flow of textile or like material, the said apparatus comprising in combination: a differential condenser comprising: at least one central plate electrode; at least one plate electrode symmetrically disposed on each side of each said central electrode, so as to form at least one measuring condenser and at least one reference condenser; means for applying high frequency po tentials of given frequency, equal amplitudes and op posite phases to the outer plates of said differential condenser; a tuned amplifier; means for applying the po tential of the said central plates to the input of the said amplifier; a detector coupled to the output of the said amplifier; an interpretation device comprising a source of continuous reference potential and an aperiodic differential amplifier with two input terminals connected one to the output of the said source of reference potential and the other'to the output of the said detector, and further comprising a low-pass filter which is capable of being short-eircuited and is disposed before the input of the said differential amplifier, the output of the said differ ential amplifier being coupled to the input of a device adapted to indicate the passing of the differential signal beyond two pro-determined threshold values, respectively positive and negative, the said device comprising a lowpass filter with an adjustable cut-off frequency, and two- 16. operating circuits with adjustable thresholds and adapted respectively to control two indicator relays.

20. An apparatus as claimed in claim 19, in which each said operating circuit comprises a thyratron, the amplified and filtered differential signal being applied to the grids of the two said thyratrons through a polarising circuit comprising an auxiliary source of continuous potential and, in parallel with the said source, on the one hand a potentiometer receiving the signal on its slider and enabling an equal polarising potential to be applied to the two grids, and on the other hand a branch comprising two potentiometers in series, having their sliders respectively connected to the two grids and enabling two independently-variable polarising potentials to be applied to the said thyratrons.

21. An apparatus as claimed in claim 19, in which each said relay is adapted to operate the supply contacts of an indicator lamp, one of the said relays causing its associated lamp to light-up in its working position, while the other relay lights-up its associated lamp in its position of rest.

22. An apparatus as claimed in claim 19, in which each of the said relays vis adapted to actuate a counter device.

23. An apparatus as claimed in claim 20 in which the operation of the two said thyratrons, the anodes of which are supplied with alternating current is rendered stable by applying the control potential to their grids through the intermediary of a resistance-capacity combination having a time-constant of the order of the period of the said alternating current supply.

24. In a high frequency measuring device for determining the substance cross section variations of materials such as ribbons, wicks and threads, a measuring condenser comprising a plurality of differential units, each comprising a measuring condenser and a reference condenser formed respectively on each side of a central plate electrode; the said central plate electrodes decreasing in surface area along one direction of the plurality of units composing the said measuring condenser, the outer plates respectively disposed on each side of the said central electrodes each having a greater surface area than that of the corresponding central electrode; means for connecting all the plates of the reference condenser in parallel; means for connecting all the plates of the measuring condensers in parallel, thereby forming a plurality of measuring channels having dimensions adapted to re ceive a range of possible dimensions of the materials to be examined.

25. The invention claimed in claim 24 in which the plate electrodes of the said differential condensers each comprise plate electrodes fixed in and forming part of larger plates from which the said electrodes are insulated with a layer of low-loss insulating material, the outer plate portions acting as anti-fringing plates to prevent electrostatic fringing-field effects at the edges of the said plate electrodes.

26. The invention claimed in claim 24 in which the said measuring condenser is formed by a plurality of metal plates of generally rectangular shape, each fixed at a bridge above two longitudinal walls of a base, also of metal, an internal co-planar portion of each plate forming a condenser plate electrode separated by a layer of low-loss insulating material from the remaining external portion, the latter portion serving as an anti-fringing plate around the periphery of the said condenser plate and being electrically connected to earth through the said base, the said plurality of plates being an odd number, the end plates and each odd-numbered plate forming the external plates, and the even-numbered plates forming central plate electrodes of decreasing dimensions, at least one of the peripheral edges of each internal plate portion which forms the common external plate between two successive central plate electrodes being cut with a bevel edge in, order that its outer surfaces may be in cor- 17 relation with the corresponding facing surfaces of the 1,996,063 said central plates. 2,817,815

in the file of this patent UNXTED $TATES PATENTS 5 122579 Re. 23,368 Grob et a1. May 22, 1951 262,827

18 Corkran Apr. 2, 1935 Evans Dec. 24, 1957 FOREEGN PATENTS Sweden Aug. 31, 1948 Switzerland Oct. 17, 1949