Automatic Yarn Inspector Comprising Double Integrating Means And Electronic Calibrating Means

Abstract

A detection system for inspecting strands of elongated material such as yarn, fishing line, sutures, cord, string, thread and the like while being advanced longitudinally individually or as a multiplicity in sheet form and for inspecting fabric and web materials. A lamp provides a beam of light applied to the material being inspected which impinges on photoresponsive means that provides voltage signals when defects occur in the material being inspected. A circuit is provided for generating signals corresponding to selected ones of the voltage comprising an integrating circuit receives these corresponding signals and generates composite signals the amplitude of which depends on the quantity and amplitude of the corresponding signals produced in preselected periods of time. Length-adjust means adjust the quantity of the corresponding signals which will be integrated to determine the length of the defects which are detected on the material being inspected.

Parent Case Text

This a continuation of our application, Ser. No. 490,773 filed Sept. 17, 1965 which is a continuation of our application Ser. No. 142,373, filed Oct. 2, 1961 and both of which are now abandoned.

Description

This invention relates generally to continuous automatic monitor systems and more particularly to a transistorized photoelectric yarn inspector.

Photoelectric yarn inspection apparatus having controllable sensitivity for detecting defects in yarns particularly synthetic yarns are known. Such apparatus are employed to detect yarn defects such as strip-backs, fluff balls, filament loops and broken filaments. Known photoelectric systems comprising a concentrated light source and a collimating optical system to project a long narrow beam of light across the yarn fibers, arranged as a "sheet," and a photoelectric receiver to receive the light, convert the light and any variations to electric energy which is transmitted to an electronic control circuit.

It is a principal object of the present invention to provide an improves automatic photoelectric yarn inspector employing transistorized control circuitry and an improved optomechanical system.

The new and improved optical system, according to the invention, improves the signal to noise ratio of the system by minimizing the possibility of stray or ambient light entering the photoelectric transducer means and substantially precluding light reflected from the yarn, which is being inspected, in "sheet" form, from affecting the photoelectric transducer thereby improving sensitivity and uniformity of sensitivity to defects.

The optical system is mounted in a detecting head of the inspector and employs a collimating lens at the light source and an objective lens, a pickup or magnifier lens unit in conjunction with a field limiting aperture in front of a phototube to exclude stray light and minimize electronic "noise" caused by tension irregularities of the yarn being inspected, jumping yarn, yarn twist, and rolling ends in the yarn sheet so that the phototube responds almost exclusively to light changes, in the inspection light beam, due to variations of radiant flux impinging on it which are caused by actual defects. Rectangular apertures which define the effective size and shape of the light beam so as to give maximum signal amplitude and frequency while still maintaining a workable light level on the phototube, are used at both light sources and receiver optical units.

The optical system accomplishes its intended purpose by causing the objective lens to form an image of the filament of a light source lamp in the plane of a small field-limiting slit or aperture in a diaphragm placed between the lenses. The greatest part of the unwanted light is prevented from falling on the phototube by not being able to pass through this aperture because it does not enter the objective lens substantially parallel to the optical axis. The pickup or magnifier lens serves to project an enlarged secondary image of the primary filament image on the cathode of the phototube. The purpose of the enlarged image is to prevent localized saturation of the cathode.

The exclusion of unwanted light and the minimizing of electronic "noise" along with other features of the yarn inspector, according to the invention, result in a highly uniform sensitivity of defect detection from one side to the other of the yarn sheet. This is especially important where it is desired to detect very small defects.

A special new light source is used with the improved optical system. The new light source lamp has a selected pear-shaped clear glass envelope of blown rather than drawn tubular construction to minimize striae and other irregularities that affect the uniformity of the projected light beam. The lamp is mounted on a new universally adjustable base to allow precise alignment of the lamp in both vertical and horizontal planes so that it can be readily and precisely aligned relative to the optical system and to permit precise positioning of the light projected by the beam relative to the yarn sheet being inspected.

Another feature of the invention is the use of solid state electronic components in transistorized control circuits thereby optimizing reliability of the apparatus due to the inherent reliability of the long lived components along with optimization in size, weight and power requirements.

The transistorized circuitry is so designed that circuit boards on which the circuitry is assembled may be removed from the system by disconnecting at multiple terminals and returned to the factory, for example by airmail, where repair can take place and the boards be quickly returned to the user.

Another feature of the apparatus is the provision of a variable and extremely well regulated high voltage supply employing a compensating system which compensates for any change in the output of the phototransducer during the effective life of the photomultiplier tube or transducer means. The high voltage from the high voltage supply itself is well regulated and is ripple free which, in part, is due to the use of transistors and silicon diodes. The improved power supply circuitry and compensation system allows the light source of the apparatus to be operated at less than 60 percent of its rated voltage capacity thereby greatly extending the life of the light source as well as protects from variant ambient conditions such as power line fluctuations.

Still another feature of the invention is an improved frequency range so that the apparatus can inspect over a very wide range of yarn speeds. The frequency range is also improved in that the apparatus is able to detect tapered type defects which may result in low frequency signals due to their contours.

Other features and advantages of the yarn inspecting apparatus in accordance with the present invention will be better understood as described in the following specification and appended claims, in conjunction with the following drawings, in which:

FIG. 1, is a diagrammatic illustration of an installation for use of the apparatus or yarn inspector, according to the invention;

FIG. 2, is a front elevation view of the yarn inspector, according to the invention;

FIG. 3, is an end elevation view of the apparatus shown in FIG. 2;

FIG. 4, is a cross-sectional view taken at line 4-4 of FIG. 2;

FIG. 5, is a cross-sectional view illustrating another embodiment of the yarn guide and is illustrative of two cylindrical yarn guide bars, according to the invention;

FIG. 6, is a cross-sectional view of still another embodiment of a yarn guide and is illustrative of a single yarn guide for guiding the yarn sheet during inspection;

FIG. 7, is an enlarged elevation view, partly in section, of a light source unit mounted on a detecting head, according to the invention;

FIG. 8, is an enlarged elevation view partially in section of an optomechanical system in the detection head forming a part of a photoelectric receiver unit;

FIG. 9, is a block diagram of an embodiment of a control unit, according to the invention;

FIG. 10, is a block diagram of a second embodiment of a control unit, according to the invention;

FIGS. 11 and 12, are block diagrams of the control unit in FIGS. 9 and 10 respectively provided with defect length detectors capable of providing another dimension of detection, namely the length of a defect;

FIGS. 13a and 13b, are diagrams of the electronic circuitry of the control unit common to all embodiments of the yarn inspector control unit, according to the invention;

FIGS. 14a and 14b, are a circuit diagram of a dual-level electronic control unit, according to the invention;

FIG. 15, is a block diagram of a length selector circuit for use with the control units, according to the invention;

FIG. 16, is a circuit diagram of the length selector circuit shown in FIG. 15;

FIGS. 17a, 17b, and 17c, are a schematic diagram of the control unit in FIG. 11;

FIGS. 18a, 18b, 18c and 18d, are a schematic diagram of the control unit in FIG. 12;

FIGS. 19 and 20, are composite diagrams illustrating how FIGS. 17 and 18 are assembled respectively;

FIG. 21, is a block diagram illustrative of a circuit for carrying out inspection only by defect length, according to the invention;

FIG. 22, is a block diagram of a calibrator for use with the various control units, according to the invention, and illustrated therewith in FIG. 12; and

FIG. 23, is a circuit diagram of the calibrator of FIG. 22.

Referring to FIGS. 1--8, the automatic yarn inspector, according to the invention, is intended to inspect and detect defects on a plurality of yarn fibers. The term yarn includes silk, wool, cotton, nylon, dacron, terrylene, acetate, viscose, rayon, cupra acrylic, and other synthetic fibers. The inspection apparatus is installed, for example, in a mill to inspect yarns 1 delivered by a creel 2 and in which the yarns are advanced through an eye-board 3 mounted on an eye-board holder 4 and through a reed 5 and are held down on yarn guides in sheet form by a hard chrome plated holddown or flattening bar 7. The yarns are advanced longitudinally in parallel, in sheet form, through the yarn inspector 8 according to the invention later herein described at length. The sheet of yarn fibers is advanced through a movable reed 9 selectively actuated by rack means 10 and the yarn advances over a recoding roller 12 onto a beam 13. It being understood that the arrangement described above is simply illustrative of the manner in which the yarn inspector may be employed and, moreover it is readily apparent to those skilled in the art that static eliminators 14 may be provided in the arrangement to reduce static in the yarn sheet.

The yarn inspector 8, according to the invention, comprises a detecting head 16 mounted as hereinafter described and comprises a light source unit 19 provided with a new light source lamp 20 and a photoelectric unit 21 having a photoelectric transducer, for example a phototube 22, mounted opposite to the light source unit 19. A yarn guide unit or assembly 23 mounted between the light source unit and the photoelectric unit completes the main units of the detecting head. The photoelectric unit is connected to an electronic control unit 24 which is alternatively mounted on a floor stand 26 or remote from the inspector. A second floor stand 28 is provided for supporting the detecting head. The two stands 26, 28 are provided with threaded screw members 30, 31 respectively for variably adjusting the height of the detecting head 16 and making coarse adjustments in leveling it.

The yarn guide assembly 23 is mounted on a tubular member 32 mounted on cross arms 33 supported on shock mounts 34. Different types of yarn guide bars, hereinafter described, form the assembly and are positionable in height by means of the adjustably set adjustment means at opposite ends of the detecting head and each consisting of a screw 37 and lock nut 38 and an upright internally threaded member 39 for fine adjustment of the optical alignment of the guide bars. The fibers move in sheet form over yarn guiding surfaces, for example flattened guide surfaces 40, 41 of a pair, FIG. 4, of rods or bars 42, 43 which are held in place and an assembly by means of a clip 44 and an externally threaded member 45 both of which are embedded along with the bars in electrically conductive epoxy resin cement 47 in a channel member 48. The conductive epoxy cement tends to bleed off static charges. The surfaces 40, 41 are precisely aligned and parallelism along their entire length is set by axially spaced set screws 49 so that even in the longest axially extending detecting head there is no part of the guide surfaces that are more than a few thousandths of an inch out of parallelism with the optical axis of the equipment hereinafter described. In order to obtain complete parallelism the bars 42, 43 are lapped. These bars are preferably conductive. The surfaces 40, 41 while flattened have the outer boundaries thereof arcuate so that the greater radius of the surface over which the yarn runs minimizes any tendency for twist or "backup" in the yarn and minimizes yarn loops and other irregularities that can cause false stopping of the yarn inspector as hereinafter explained and yarn wear is likewise reduced. The length of the guiding surfaces is sufficient to allow optimum separation of the yarn ends thereby minimizing "rolling" ends and other difficulties due to crowding of the ends.

The double-type construction shown in FIG. 4 of the guide bars is employable for all ordinary yarn inspection applications and the position of the parallel guiding surfaces are so adjusted that the yarn sheet crosses through the center of an inspection light beam 59 so that any defects which project upward or downward change the light falling on the phototube 22 by a minute amount causing an electric impulse as hereinafter explained.

Preferably, the guide bar assembly is constructed of two parallel guide bars 52, 53 circular in cross section held in position by a clip 54 and embedded in epoxy resin 55 in the manner heretofore described. The bars' upper surfaces are aligned by set screws 56 and held in position by the resin after alignment. The completely round surfaces thereof permit optimum guide bar wear and reduce the possibility of yarn damage since war is more evenly distributed over a greater surface. Moreover, any tendency of the twist to "backup" is substantially eliminated. In this construction of the guide bar assembly, FIG. 5, a groove 57 is shown formed between two guide bars 52, 53 which is sufficiently deep to permit an inspection light beam 59, formed by the unit 19, to be projected along the groove, transversely of the yarns 1, so that it is just underneath the yarn sheet passing over the upper surfaces of the bars 52, 53. This construction minimizes the problem of false stopping resulting from yarn looping due to poor tension control, transfer jerks and backup of a yarn twist which generally cause the yarn to jump upward and away from the guide rather than into the light beam. This unit is useful for heavy yarns and tire cord. While the groove 57 is shown in the embodiment in FIG. 5 it will be understood that this type of groove can be used in the embodiment in FIG. 4 in which case the beam would not intersect the yarn sheet 1 as illustrated.

A third embodiment of the guide bar assembly of the invention makes use of a single guide bar 62 in which only one guide surface is located just below the light beam. The bar 62 is held in position by holding members 64, 65 which adjustably hold the bar under control of a threaded screw 67 and permit selective rotation thereof to prevent grooving of the guide surfaces by excessive wear. Threaded screws disposed axially of the bar such as an adjust screw 68 provide a fine axial level adjustment of the bar 62. This particular construction is preferable for heavy yarns, as for example, tire cord. The yarn sheet in such constructions is outside of the light beam which is directly above the sheet so that large defects upon passing over the guide are pushed upward into the beam for detection and actuation of the apparatus as hereinafter described.

In the various embodiments of the yarn guide assemblies the bars are made of conductive or nonconductive ceramic or satin-finished chrome plate or flame coated ceramic or hard metal. Ceramic guide bars are preferably used when abrasive yarns, for example nylon, are being inspected. The same guide bars are employed in inspecting multifilament and spun yarns, thread, cord, fishing line, medical sutures and the like.

While the yarn inspector or monitor has been described as applicable to the inspection of yarn ends arranged in sheet form it is to be understood that the monitor is applicable to detection of defects in single ends. In single and inspection the guide, not shown, is constructed in known manner.

LIGHT SOURCE UNIT

The detecting head light source unit 19 comprises a lamp 20 which has a pear-shaped envelope which has been blown thereby resulting in minimum distortion of the luminous flux emitted therefrom. The light bulb is held in a mount or base 70 fixed to a casting 71 fixed to the tubular member 32 and has a vertical or preferably horizontal filament 72 positionable relative to the optical axis of an optical system of the inspection apparatus hereinafter described. The lamp base permits optimum alignment of the bulb filament 72, which may be a horizontal or vertical filament, in the optical axis of an optical system of the inspection apparatus. The radiated flux enters a collimating lens unit of the optical system comprising a tubular member 74 in which a diaphragm 75 provided with an aperture 77 is disposed substantially adjacent one end of the tube. A beam-forming or collimating lens 78 for rendering the luminous flux rays parallel is disposed axially spaced from the aperture 77. The parallel light rays pass outwardly of the tube 74 through an aperture 79 preferably rectangular provided in a diaphragm 80 which is held in position by an externally threaded bushing 82. The rays then pass outwardly of the light source unit through a window 82 in a housing 85 for the unit. The light rays are projected as the beam 59 across the yarn sheet formed by the yarns 1. It will be remembered that the light beam 59 is positioned with respect to the yarn sheet in accordance with the type of yarn being inspected and the yarn guide bar arrangement being employed in the unit during the inspection function as heretofore described.

The lamp mount 70 comprises a lamp base member 88 having a threaded flange portion 89 bearing on a threaded pivot 90. Threaded pivot 90 is seated in an unthreaded groove in 92 so that it can rotate without moving axially. It is prevented from moving axially by having a groove (not shown) around its periphery which is engaged by a pin (not shown) held in 92. The flange portion 89 is held in position bearing on the pivot by a threaded screw 91 threaded into a member 92 and having a spring 95 peripherally thereof bearing on the portion 89. Another threaded screw, not shown, is disposed on the opposite side of the base member 88 and is threaded into the fixed member 92. The head of this second screw bears on the portion 89 so that by axially adjusting this second screw the member 88 is pivoted relative to the pivot 90 so the filament 72 can, therefore, be positioned precisely in a horizontal plane. The threaded pivot 90 provides vertical adjustment of the bulb 20 so that the filament 72 can be readily accurately positioned relative to the optical axis of the optical system of the inspector.

PHOTOELECTRIC UNIT

The light beam is received in the photoelectric unit 21 where it enters a light-impervious housing 98 through a window 99 and passes through the rest of the optical system comprising an objective or condensing lens 103 and a magnifying lens system of two lenses 100, 101, coaxially mounted in a tubular element 105 and impinges on the cathode of the photomultiplier tube or transducer means 22.

The tubular element 105, in which is mounted the magnifying system, has an internally threaded bushing 106 disposed on an externally threaded bushing 107 adjustably set axially internally of the bushing 106. The bushing 107 has axially spaced therein the pair of magnifying lenses 100, 101. A diaphragm 110 is disposed in the bushing 106 axially spaced from the magnifying lenses and is provided with a small slit or aperture 111. The diaphragm is held in place coaxially with the two magnifying lens internally of the bushing 106 by a keeper 113. The bushing 106 and diaphragm (not shown) is biased in a direction away from the opening 99 by a blackened spring 115 which also serves to eliminate stray reflections from the internal walls 105 and which is seated on a shoulder 116 of the tube 105 and held in axial position by a set screw 117. At the opposite end of the tube is disposed the objective lens 103 which is held in position in the tube 105 by an externally threaded bushing 118 axially adjustable in the tube. A diaphragm 119 is staked in position in a cap 121 at the starting end of the tube and is provided with a relatively large rectangular aperture 123, preferably of the same size and shape as 79, through which the light beam passes. The lens unit and the photomultiplier tube or photoelectric transducer are removably mounted on a casting 125 removably fixed to the tubular member 32 by cap screws 126 as shown.

An image of the filament 72 is formed in the plane of the slit 111. The greatest portion of undesired light is unable to pass through this very small slit so that as a result substantially only the modulated light rays of the beam pass through the slit. The magnifying lenses 100 and 101 project an enlarged second image of the filament on the cathode of the photomultiplier tube 22. On the passage of a defect the effect of the optical system is to cause a substantially uniform dimming of the illuminated area formed on the transducer cathode which improves the life, the sensitivity and uniformity of sensitivity response of the photomultiplier. It is apparent that the housing or cover 98 forms a light-tight compartment in which the lens unit and the tube are mounted to form the photoelectric unit of the detecting head and ambient unwanted light is eliminated from the system.

CONTROL UNITS IN GENERAL

The photomultiplier 22 is connected to the control system or unit 24 which comprises circuitry to obtain optimum sensitivity and accuracy of the yarn inspector with well regulated circuitry of utmost ability later described in detail, in FIGS. 9--22. A power supply 130 in the control unit is connected to a line voltage with a lead 131 and transforms the line voltage to a DC filtered output applied to a transistorized lamp voltage regulator circuit 133 which applies a low level voltage to the light source lamp 20 and a collector voltage regulator 135 whose output is connected to collectors of the transistorized lamp voltage regulator 133 and to collectors of emitter follower circuits in a compensator 137 which has a high voltage supply and oscillator circuit 138 and the phototransducer or photoelectric tube 22 connected in a self-compensating loop herein later described. The voltage regulator circuit 135 has a well regulated ripple-free output for use as supply to the high voltage compensating circuit 137 which functions essentially as a feedback regulator and applies an output to the high voltage supply and oscillator circuit 138 which supplies its output to the phototube 22 and to emitter followers in the compensator which make it possible to obtain extreme stability. The outputs of the phototube 22, the compensator 137, and the regulator 135 are applied to an amplifier 140.

The overall theory of operation of operation of the automatic inspector is as follows:

A very small change in the amount of light impinging on the face of the photomultiplier tube 22, due to variations in the beam 59 due to yarn defects, will produce an electrical pulse. The pulse is amplified by the amplifier 140 and used to operate an output relay 142 to open or close a circuit such as a stop motion, a motor or a light and can stop the warper or beam 13. Each part of the circuit required to accomplish the above has been precisely engineered in the control units, later herein described at length, for the yarn inspector permitting high and low sensitivity control which enables the user to easily adjust the unit to detect defects larger than any desired minimum size from a single broken filament to large fluff balls.

The circuitry, FIG. 9, of the above-described block diagram is that of an embodiment of a single level control unit usable in an application which it is desired either to detect and count or detect, count and stop a warper only for defects over one certain size. The control unit according to the invention, is made in five embodiments thereof; single level, dual level, single level with length selector, dual level with length selector, and a length selector arrangement. These different control units are used separately with the detecting head depending on the inspecting to be done. In order to simplify the drawings the circuitry common to the various types of control units have the same reference numbers.

The dual level control unit, FIG. 10, is used for those applications where it is desired to detect yarn defects on two different sensitivity levels as later herein described. The dual level control unit is particularly applicable to situations where all defects are counted, both major and minor, but the warper is made to stop only for major defects which are then later removed from the yarn. The purpose of the count of minor defects is to establish quality control information and this type of electronic control unit is particularly applicable to yarn inspection production functions.

The single level control unit with a length selector, FIG. 11, hereafter described adds another dimension of detection, namely the length of the defect, to the single level control unit illustrated in FIG. 9. This unit can either detect and count or detect, or count and stop a warper for defects over one certain size or diameter and one certain length.

The fourth type or model of the control unit, FIG. 12, according to the invention, provides for dual level sensitivity with a length selector which provides an additional dimension of detection, namely the length of the defect. By means of this unit both major and minor defects may be detected on a basis of not only the size but also the length. This allows the user of yarn inspector to allow knots and short defects to pass by undetected yet to catch longer defects which may be smaller in size. Detection of filament loops, slack filaments and long, tapering defects are conditions easily detected by this type of unit hereinafter described.

Each of the four above-mentioned different types of control units have types of controls equipped with high and low sensitivity controls, as hereinafter described, which enable the user to easily adjust the unit to detect defects larger than almost any desired minimum size from single broken filaments to large fluff balls. It being understood that the dual level units are equipped with two sets of controls. Moreover, all of the series of control units are equipped with fail-safe protection and indicating lights, as later described, so that any failure of the lamp or tube system will automatically stop the warper 13 and indicate the failure by means of a light on the control unit 24.

In addition, each unit is provided with a receptacle in which can be plugged a small auxiliary electronic calibrator, FIGS. 22 and 23, and sensitivity checking device hereinafter described. This is automatically actuated each time the warper stops for any reason whatsoever and indicates whether or not the yarn inspector is performing properly at the sensitivity for which it was set. Failure of this unit to operate properly at the present sensitivity is indicated by a light in the panel of the auxiliary unit and the user of this auxiliary unit in conjunction with the fail-safe built into the control unit itself guarantees complete protection against malfunction of the yarn inspector.

The fifth unit is a circuit, FIG. 21, for carrying out inspection only by defect length. Defects over one certain length are detected and counted or if desired the apparatus can detect, count and stop a machine when defects over one certain length are sensed.

A low frequency cutoff switch arrangement on the panel of each of the four first-mentioned control units, as hereinafter described, provides three degrees of selection of the low frequency response cutoff point enabling the user to choose the optimum low frequency cutoff point to get best performance from the yarn inspector for given types of yarn defects and conditions. It will be understood that in the length selector low frequency cutoff switch is not utilized. The low frequency cutoff arrangement permits a minimization of "false stops" due to faulty tension control in the yarn plucking originating in the pirn static and other conditions. Moreover, at the same time it permits the catching of long, gradually tapered defects which cause low frequency signals that may be difficult to distinguish from electronic "noise" resulting from external factors.

Referring now to the circuitry to be found in each of the various series of control units, according to the invention, and described in detail in FIGS. 13a and 13b; these two FIGS. illustrate in detail the circuitry of the various blocks of the block diagram of FIG. 9 which illustrates the circuit of the single level control unit version or embodiment of the control unit. This basic circuitry is common to each of the embodiments of the control unit except the length selector.

POWER SUPPLY

A power supply 130, for both the lamp voltage regulator 133 and the voltage regulator 135 which functions as a collector voltage regulator, is provided with a lead 131 and an on-off switch 146 for connecting the control unit 24 to a source of line voltage, not shown. The desired voltage is obtained by transforming the line voltage, which may be 115--230 volts, 50--60 c.p.s. by a transformer 149 which has two secondary output windings 150, 151 for applying power to the collector voltage regulator 135 and the lamp voltage regulator 133 respectively. A power pilot light 154 is connected as shown to indicate when the switch 146 is on the on condition.

The output voltage of winding 150 is applied to a silicon bridge rectifier 157 and a DC filtered output of this circuit is taken out at DC terminals 158, 159 and applied as collector voltage in the volt regulator circuit 135 as hereinafter explained. A voltage doubler consisting of a pair of diodes 161, 162 and a pair of capacitors 165, 166 is connected to the regulator circuit 135. The other secondary winding 151 of the transformer 149 is fed into a silicon bridge rectifier 173 and a DC filtered output is taken out at DC terminals 174, 175 and applied to the lamp voltage regulator circuit 133 along two leads 176, 177.

VOLTAGE REGULATOR CIRCUIT

The regulator circuit 135 is a series transistor regulator. This circuit is a feedback regulator using a zener diode as a reference element. Two transistors 180, 181 are connected to act as the control element as a zener diode 182 connected across the regulator is the reference element. A power transistor 183 is connected to the rectifier 157 as a series element to absorb voltage variation and functions as an emitter follower whose base is held at a fixed voltage and, therefore, the emitter voltage is constant. The well regulated output voltage is ripple-free and is fed out of leads 184, 185 and is controlled by adjustment of a potentiometer 186.

A reference voltage from the zener diode 182 maintains the emitter of the control transistor 180 at a constant voltage. The collector voltage of the control transistor then changes inversely with the voltage change on the base and this change is fed to the base of the transistor 181, which functions as an emitter follower. A zener diode 192 is connected in the regulator circuit to maintain a constant voltage drop from the voltage double circuit to the emitter of the emitter follower transistor 181. The change at the emitter of this transistor is directly coupled to the power transistor 183.

The output from the emitter of the power transistor 183 is a well regulated, ripple free output for use as a transistor collector supply applied to the compensator 137 by leads 184, 185 as shown and applied to the lamp voltage regulator 133 by a lead 195 as a reference voltage.

LAMP REGULATOR CIRCUIT

The lamp power supply or lamp regulator circuit 133 is substantially similar to the regulator circuit 135. A control transistor 198 in cascade with a buffer transistor 200 jointly function substantially similar to the control element transistors 180, 181 of the voltage regulator circuit. A series transistor 203 is series with the power supply rectifier 173 provides a well regulated output voltage along an output lead 204 connected to a base pin A for providing a steady lamp voltage to the lamp 20. In order to maintain the lamp voltage at a desired level a potentiometer 206 connected to the base of the control transistor 198 is provided.

In the lamp regulator circuit a reference voltage is not obtained by use of a zener diode in the manner of the voltage regulator circuit. Instead, the regulated output of the voltage regulator circuit is used as a reference voltage and applied along the lead 195 and a voltage divider network as shown. In order to protect the unit a protective resistor 208 is utilized to prevent damage if the lamp accidentally shorts. This resistor is in series with the lamp regulator circuit 133 so that if a short occurs the current will be limited.

PHOTOELECTRIC TRANSDUCER

The photoelectric transducer used in the yarn inspector, according to the invention, is the photomultiplier 22. It operates on the following principle:

As the light from the beam 59 strikes the photosensitive cathode 210 electrons are emitted. These electrons are drawn with high velocity to a more positively charged dynode. When they strike the dynode more electrons are dislodged resulting in secondary emission and they are attracted with high velocity to a still more positively charged dynode. This procedure occurs in all ten stages of the photomultiplier tube, until a comparatively large current is built up for a given amount of light incident on the photocathode 210. In normal operation, as a photomultiplier is used its sensitivity decreases. This is in great part overcome by use of the novel voltage compensating circuit 137 to be described in detail later.

The phototube has a shield 211 of magnetic material to protect the electron beam from any stray magnetic field. The shield is connected to the cathode 210 with a resistance 212 to protect the electron beam from any stray electrostatic field. The output of the photoelectric transducer, therefore, substantially corresponds to the light impinging on it cathode. The shield has an aperture, not shown, through which the rays of the beam 59 enter and impinge on the cathode.

In order to simplify the drawings the photomultiplier and lamp 20 bases are shown schematically on a common base 215 with pins as indicated. The various pin connections are as shown and later explained.

AMPLIFIER CIRCUIT

The output of the photomultiplier, in the form of a pulse when a variation in light occurs due to a beam change caused by a yarn defect varying the amount of light impinging on the photomultiplier, is fed into a transistor emitter follower 219 in the detecting head in order to minimize extraneous noise. This is accomplished by lowering the output impedance of the detecting head. A biased diode 220 protects the transistor 219 from overvoltage damage. The pulse is then applied through pin G to the base of a transistor 221 connected as an emitter follower in the compensator 137. From the emitter of this transistor 221 the signal goes along a lead 223 to a rotary switch 225 which is operable to a position 226 when a calibrator unit, hereinafter described, connectable to the control unit at a plug 227 is to be used with the yarn inspector and is operable to a position 228 when the calibrator is not in circuit. The signal then goes to a "High-Low" sensitivity control switch 230. Sensitivity to the defects being detected is adjusted by a sensitivity adjust potentiometer 233. On a "High" position 234 of the switch it is possible to catch a single filament without reaching the maximum position of the sensitivity control. On a "Low" position 235 a series resistor 236 decreases the signal thus permitting finer adjustments whether small or large defects are being detected.

From the sensitivity control the signal must pass a rotary frequency cutoff switch 237 which places various capacitors 238, 239, 240 in the circuit, thereby permitting a choice of frequency response. When the frequency cutoff switch is on a "Low" position 242 an extremely flat frequency response is obtained. On a "Medium" position 243 and a "High" position 244 the low frequency response is decreased so that maximum sensitivity and minimum noise is obtained. As the noise due to yarn vibration, 60 c.p.s. pickup and most other noises are under, for example, 200 c.p.s. in frequency, the choice of capacitors allowed by the "frequency cutoff" switch 237 permits discrimination against the noise. As the signal frequency is normally not less, for example, than 500 c.p.s., and most often about, for example, 1000 c.p.s., any position of the switch scarcely affects it. On a "Medium" and "High" position a slight loss in signal occurs but this is not more than 5 percent and 10 percent respectively.

After the signal, in the form of a positive pulse, goes through the emitter follower 221 the "High-Low" switch 230, the sensitivity adjust 233 and the "Frequency Cutoff" switch 237 it is fed through two transistor amplifiers 249, 250. These transistors have a great deal of negative feedback for maximum stability and constant gain. A biased diode 251 couples the output of the output amplifying transistor 250 to the base of another amplifier transistor 253. The coupling diode 251 helps to get rid of all unwanted negative signal noise and most of the unwanted positive noise, while passing most of the wanted positive signal. The transistor amplifier 253 amplifies the signal and inverts it so that a comparatively large negative triggering pulse is applied to the base of a transistor 255 connected to a transistor 257, in a monostable multivibrator configuration.

The monostable multivibrator circuit is triggered by the negative pulse from the collector of the transistor amplifier 253 described above. Once the multivibrator is triggered the pulse amplitude and duration are determined by the parameters of the multivibrators. The input pulse itself is merely the triggering factor. The action of the multivibrator is as follows:

When a negative pulse of sufficient amplitude is fed into the base of the multivibrator transistor 255 it causes the transistor to conduct heavily. This increase of current through a resistance 260 will decrease the voltage at the collector of the transistor 255 which will in turn appear as a positive pulse at the base of the output transistor 257. This positive pulse is sufficient to cutoff the output transistor 257 deenergizing the output or control relay 142 momentarily opening a contact 262. The opening of the contact 262 deenergizes a stop motion relay 263 which has its operating coil in the circuit of the contact 262 and which either opens or closes a stop motion circuit comprising a receptacle 264 to which the warper is connected. A separate set of contacts 265 on the control relay 142 operate a counter 267 for counting the defects and a signal lamp 268 connected to a receptacle 269 as shown. The time the relay 142 is deenergized is a function of the values of the resistances 260, a resistance 271 and a capacitor 272 and not a function of the input pulse. When the resistances 260, 271 and capacitor 272 allow the circuit to regain equilibrium the multivibrator is again ready to receive a triggering pulse.

Thus, it will be seen that a positive pulse from the phototube is adjusted to the correct sensitivity; passed through the frequency selector; amplified and fed through the noise limiting diode; and as a noise free negative pulse, used to trigger the input of the monostable multivibrator; and finally the pulse operates the output or control relay 142 connected in the collector of the multivibrator output transistor 257.

FAIL-SAFE

As indicated heretofore fail-safe protection is provided in the yarn inspector, according to the invention, and operated as follows:

A fail-safe relay 280 is provided, FIG. 13b, in the control unit and is normally in an "on" condition. If the yarn inspector is not turned "on"; or if a fuse blows; or if the line cord is not plugged in the socket; or if the collector voltage in the regulator 135 decreases, the relay 280 does not "Pull in" and thus opens the energizing circuit to the stop motion relay 263 and the receptacle 264 to which the warper is connected and prohibits the warper 13 from running and in opening the fail-safe circuit turns off a fail-safe indicator light 282 on a front panel 285 of the control unit 24 and in series with a resistance 284 that may be connected in series therewith. The fail-safe relay 280 obtains its "on" current through a transistor 286 in the circuit of the relay coil 287. This transistor conducts due to the voltage applied to its base. This voltage is obtained from the output of the phototube 22 along a lead 289 and through transistor 221. Should this voltage decrease for any reason, as for example, if the lamp voltage circuit fails; the lamp burns out; the phototube is nearly dead; the high voltage circuit fails; transistor 221 or transistor 286 burns out; the compensator circuit fails; the relay will fail to pull in. This also will keep the energizing circuits to the stop motion relay open and prohibit the warper from running and turns off the fail-safe light 282.

HIGH VOLTAGE COMPENSATING CIRCUIT

The high voltage compensating circuit 137 is essentially a feedback regulator, not unlike the collector voltage regulator 135 and lamp voltage regulator 133 described previously. The output from the photomultiplier 22 is directly coupled from the pin G, to the emitter follower transistor 221, which is connected to two other emitter follower transistors 292, 293 which together with the transistor 221 form a feedback circuit. The correct voltage is obtained from a potentiometer 295 and directly coupled into the base of a compensator control transistor 297. The emitter of this control transistor is held at a constant reference voltage by a zener diode 298. The collector of the control transistor 297 is connected to the base of a series transistor 299 in the compensating circuit.

From the foregoing it can be seen that the output voltage of the compensator circuit is dependent on the input voltage to the base of the control transistor 297. This input voltage in turn depends on the output voltage of the photomultiplier 22. If the output voltage of the tube decreases with time the input voltage to the control transistor 297 will also decrease. Since the emitter of the control transistor is held at a constant reference voltage by the diode 298 the collector output thereof will increase, whereby the output of the series transistor 299 will increase and compensation for loss of output voltage of the tube 22 take place. It will be remembered that the collector voltage to the transistors in the compensating circuit 137 is provided from the regulator 135 along its output leads 184, 185.

HIGH VOLTAGE OSCILLATOR CIRCUIT

The output from the compensating circuit series transistor 299 is fed by a lead 304 into the collector of an oscillator transistor 305 in the high voltage supply and oscillator circuit 138. The output of this oscillator has a preselected frequency, for example a frequency of about 7500 c.p.s., and is transformed to a high voltage by a transformer 306. This high AC voltage is directly dependent on the collector voltage at the oscillator transistor 305. This means that, depending on the output of the photomultiplier 22 the oscillator output voltage will vary, for example, from 200 volts to 400 volts.

The transformer output voltage is applied to a half-wave voltage doubler rectifier circuit comprising an input capacitor 308 and a pair of silicon rectifiers 311, 312. This enables obtaining a minus DC voltage, for example 280 volts to minus 550 volts DC across each of the rectifiers, or a minus DC voltage for example, 550 to 1000 volts D.C., across a capacitor 315a. The theory of the voltage doubler is that the input capacitor 308 to the junction 313 of the two silicon rectifiers 311, 312 charges to the peak supply voltage so that the voltage fluctuates between zero and twice the peak supply voltage. The output capacitor 315a, holds the voltage to twice the peak input voltage, accordingly, the term "doubler" describes the rectifier circuit. After elimination of AC ripple or filtering by the capacitor 315a, 315b and a resistor 317 the DC or (B-) voltage from the rectifier circuit is applied to the photomultiplier tube along a lead 318 to the base pin E to which the cathode 210 is connected. The output of the photomultiplier is dependent on the DC voltage applied. Therefore, as the phototube decays the action of the compensating circuit, the oscillator and the half-wave voltage doubler circuit combine to increase the supply voltage in order to maintain the phototube output the same at all times and throughout the life of the tube.

The detecting head is provided with a sensitive microammeter 320 in series with a resistance 321 for visually indicating the output of the photomultiplier tube 22 which, as indicated heretofore, must be a steady state current and constantly held steady. In order to maintain a count on the defects the pulse counter 267, for example a four digit "Veeder Root" counter, provides visual indication of the counts and is under control of the control relay 142.

As mentioned heretofore the stop motion circuit and receptacle 264 connect the inspector to the warper in order to stop the warper under control of the stop motion relay 263. The alternating current receptacle 269 is connected in and out of circuit with line voltage applied under control of the relay contact 265.

The above-described circuitry, as mentioned heretofore, is that of a single level control unit and is also the circuitry of each of the other embodiments of the control unit hereafter described, except the length selector, which are primarily modifications of the basic single level control unit.

DUAL LEVEL ELECTRONIC CONTROL UNIT

The dual level electronic control unit, FIGS. 10, 14a, 14b, according to the invention, includes a second amplifier 325, receptive of the output of a compensator 137' and in parallel with an amplifier 140' which functions similarly to the amplifier 140. The output of the second amplifier is delivered to a second output relay 327 functioning in a manner similar to the output relay 142' which corresponds to the relay 142. It will be understood that in FIGS. 14a, 14b the component patts 130'--142' and others corresponding to the single level control unit parts of FIGS. 13a and 13b bear corresponding reference numerals thereto except they are primed in order to simplify the disclosure.

The second amplifier 325 is constructed similar to the amplifier 140 heretofore fully described. This means that the inspector dual level electronic control unit has two sets of controls that permit settings on the inspector to detect yarn defects on two different sensitivity levels. The dual level inspector or system is usable to count all defects, both major and minor. The system is provided with a major defect counter 267' operably connected to a relay 142' comparable to the relay 142 in the single level electronic control unit heretofore described and connected to a stop motion relay 263' controlling an output receptacle 264' which controls the warper 13. The warper is under control of the amplifier 140' which detects the major defects and the warper is made to stop only for major defects which are then removed from the yarn.

The counting of defects at two sensitivity levels are set on the control unit as heretofore described with respect to the single level unit. The dual level control unit is provided with mechanically interconnected switches 350, 351 connected to the two control relays for connecting control relay 142' and a minor defect counter 356 to the system. These switches are operable to an off position in which the apparatus only counts defects, a second position in which the stop motion relay 263' operates when a major defect is detected and in which the minor defect counter simply counts. The switches are operable to a third position in which the switches 350, 351, set the apparatus for stop-motion operation in response to sensing of minor defects and the major defects are only counted. The switches are operable to a fourth position in which both counters are in circuit and both minor and major defects are counted and the stop motion relay 263' is rendered effective by either major or minor defects detected. As indicated heretofore the major defect control relay 142' can control the stopping of the warper 13 and the minor counter 356 can be used in counting minor defects. In this type of operation the purpose of the minor defect count is generally to establish quality control information. This type of electronic control unit is ordinarily used by yarn producers.

The second amplifier 325 receives the positive pulse generated by the transducer 22 through a frequency cutoff switch 324 after passing through a sensitivity control 363, a "High-Low" switch 361 and two mechanically interconnected switches 225' corresponding to the switch 225 for placing in circuit a receptacle 227' to which a calibrator unit, hereinafter described, is connected to the system. The switches 225' are operable to positions in which the receptacle 227' is isolated or otherwise pins thereof placed in circuit with either of the amplifiers 140' or 325 so the output of the calibrator can be applied to either of the amplifiers for calibration thereof as hereinafter described.

After passing through the "High-Low" switch 361 and through a frequency cutoff switch 364, comparable to the switches 237 and 237' and capable of connecting frequency response control capacitors in circuit as shown, the signal is applied to two transistor amplifiers 365, 366. These transistors have a great deal of negative feedback for maximum stability and constant gain. A biased diode 368 couples the output of the amplifying transistor 366 to the base of another amplifier transistor 369. The coupling diode 368 helps to get rid of all unwanted negative signal noise and most of the unwanted positive noise while passing most of the wanted positive signal. The last-mentioned transistor amplifier amplifies the signal and inverts it so that a comparative large negative triggering impulse is applied to the base of a transistor 370 which is the input transistor of the monostable multivibrator formed in conjunction with another transistor 371.

The monostable multivibrator circuit is triggered as heretofore described with respect to the amplifier 140. Once a multivibrator is triggered the pulse amplitude and duration are determined by the time constants of the multivibrator. The action of the multivibrator is as heretofore described.

As indicated heretofore fail-safe protection is provided in the yarn inspector in the dual level electronic control unit arrangement. A fail-safe relay 280' is provided in the dual level control unit comparable to the relay 280 heretofore described. The relay 280' obtains its "on" current through a transistor 286' and the control relay 327 obtains its "on" current from a circuit 371 in the circuit of the respective relay coils. The transistor 286' conducts due to the voltage applied to the base thereof. Should this voltage decrease for any reason, for example for the reasons described with respect to the single level control unit, the fail-safe relay 280' will prohibit the warper from running and turn off a fail-safe light 282' in series with a resistance 284' which may or may not be used.

The dual level control unit is provided with an ACO connector 268' and an AC receptacle 269' connected to the power supply 130' through a lead 378 and to the major counter 267' as shown so that a signal is applied thereto only when major defects are being detected. The unit is connected to the regulator 135' through a lead 379 and to the compensator 137' through a lead 380.

LENGTH SELECTOR AMPLIFIER

As stated heretofore the length selector amplifier provides detection of defects according to their length and diameter. The length selector will first be described as to its mode of operation and then described as applied to the single level and dual level control units. The mode of operation of the length selector is as follows:

The length selector 400 comprises, FIGS. 15 and 16, an input sensitivity control 405 to which the output signal, comprising pulses, of the photomultiplier is applied. From the sensitivity control the signal, FIG. 15, is applied to an amplifier 406 and then to a biased diode 408 to produce a comparatively noise-free signal. This signal is fed into a saturated amplifier 409 that will saturate so that the output is essentially constant over an extremely wide range of inputs. From this amplifier the signal is applied to an indicating circuit 410 which causes a neon indicator light 413 to blink in the event the signal and/or noise is large and over a predetermined limit. The signal from the saturated amplifier is also applied to a storing and a first integrating circuit 415 where it is integrated and is substantially applied to an emitter follower and amplifier 417 and fed into another emitter follower and integrating network 419. The output at this point is a direct function of defect length, rather than defect amplitude. The output is adjustable, by a length adjust circuit 420 as hereinafter explained, so that any length defect, for example up to ten or twelve inches in length may be discriminated against. In operation this means the equipment may be set to detect any length of defect, for example from one-half inch and over. The maximum length the inspector will discriminate against is about ten to twelve inches depending on the warping speed.

The signal is applied from the length adjust circuit to a transistor monostable multivibrator 422 triggered by the signal and which permits a control relay 425 to function.

The output of the photomultiplier 22, for example, is fed, FIG. 13a, 13b, into the base of the emitter follower transistor 219 and then to the emitter follower transistor 221. From the emitter of the transistor 221 the signal is applied, FIG. 16, to the input sensitivity control 405 which is in the form of a potentiometer and permits a given amount of signal and noise to be fed to the base of a transistor 406 connected as an amplifier. From the collector of the transistor 406 the signal and associated noise is applied to a biased diode 408 which eliminates all of the positive signal and noise, most of the negative noise and some of the negative signal. This is accomplished by varying a noise adjust control or potentiometer 457 which varies the amount of bias it and a pair of resistances 358, 359, permit to be applied to the biased diode 408 thereby controlling the amount of noise passed through this circuit. Thus, the noise that passes through the biased diode 408 will be too small to affect the rest of the circuit. The signal then goes to the base of a transistor 409, which forms the saturated amplifier, and is amplified until saturation occurs, so that all defects over the size chosen by the setting of the input sensitivity control 405 and the noise adjust control 457 will produce the same pulse amplitude at the output, the collector of the amplifier 409. It will be understood that the saturated amplifier is connected with biasing resistances and a feedback loop, as shown. These pulses of constant amplitude, with any small amount of noise remaining, goes to a diode 462 which acts as a DC restorer, and to a .01 capacitor 464 which is the pulse storer of the circuit 415.

The signal and noise is also applied to the base of a transistor 467 which is capacitance coupled by a capacitor 468 to a second transistor 469 which jointly therewith forms the indicating circuit 410 which controls the noise indicator lamp 413. When the signal and/or noise is large enough the pair of transistors in the indicating circuit will allow the noise indicator lamp to blink. From the pulse storer 464 a modified pulse is fed into the first integrating circuit 415 which comprises a pair of resistances 471, 472 and a capacitor 473. The integrating circuit and the pulse width (length of defect), which is adjusted as hereafter explained, determine the amplitude of the input to the base of an emitter follower transistor 475 connected to buffer the integrating circuit from an amplifier transistor 476 which has a low impedance input and which together with the buffer form the circuit 417. After the amplifier 476 the remainder of the length selector circuitry is directly coupled since the signal at this point is a DC pulse. Three transistors 480, 481, 482 are connected directly coupled to the amplifier as emitter followers. The second integrating circuit 419 consists of a resistor 485 and a capacitor 486 further refines the pulse. The length of the defect selection desired is obtained from a length selector potentiometer 490 connected to the emitter of the emitter follower transistor 481. At this point, the length of the defect is directly related to the output voltage. Accordingly, the higher the setting of the length selector potentiometer, the smaller the defect length the yarn inspector will detect; the lower the setting, the longer the defect length detected.

The output from the potentiometer 490, which is a part of the circuit 420, is fed into transistor 482 and then to the base of input transistor 492 of the monostable multivibrator 422 which jointly with an output transistor 493 capacitance coupled thereto by a capacitor 495 forms the multivibrator. This output is a comparatively large negative signal and since the monostable multivibrator circuit is identical to that of the single and dual level yarn inspector electronic control units heretofore described the input to the base of the output transistor 493 will cut that transistor off, permitting the control relay 425 to operate. The relay is provided with contacts which can be connected to a stop motion circuit, a counter, and a fail-safe circuit, and as hereafter described with respect to the two basic types of control units.

SINGLE LEVEL WITH LENGTH SELECTOR

As indicated heretofore the invention provides electronic control units which include an additional dimension of detection, namely, the length of the defect. An embodiment of a single level electronic control unit with a length selector, FIGS. 11, 17a, 17b, and 17c, having the additional dimension of detection can detect defects as to amplitude, as heretofore described and as to length. This unit enables the user to allow knots and short defects to pass by undetected, yet to catch longer defects which may be smaller in size or amplitude. The unit is used for detection, for example filament loops, slack filaments and long tapering defects.

In a single level electronic control unit with a length selector, FIG. 11, the circuitry is the same as described with respect to the single level control unit with the exception of the fact that a length selector amplifier 400 and output relay 425, described with respect to FIG. 16, are added thereto. In order to simplify the description and drawings, the same reference numerals applied to the single level control unit and to the description of the length selector, FIG. 16, are used in the description of the two combined into a single level with length selector unit. Thus, the power supply 130 having a line input 131 is connected to the voltage regulator 135 and to the lamp voltage regulator 133. The lamp voltage regulator supplies power to the lamp 20 and the voltage regulator 135 to the compensator 137, as heretofore described. The loop circuit between the high voltage supply and oscillator circuit 138 and a photoelectric transducer 22 and the compensator 137 is provided. The amplifier 140 is connected to the output or control relay 142 and a stop-motion relay 263 is provided. The output relay 425 of the length selector is likewise connected to the stop-motion relay, as hereafter described.

The details of the circuitry of the amplifier 140 in conjunction with the length selector amplifier 400 and the manner in which they are connected is illustrated in FIGS. 17a, 17b, and 17c. It being understood that the circuitry of the blocks illustrated in FIG. 11, is the same as heretofore described except to the extent that will be described hereafter with respect to FIG. 17. The length selector amplifier 400 when used in conjunction with the single level selector is illustrated in detail in FIGS. 17b and 17c wherein the reference numerals corresponding to the discussion with respect to FIG. 16 are employed. The length selector amplifier circuits are the same and the indicating circuit 410 is connected in the same manner as heretofore described except that the light 413, acting as a noise indicator, is illustrated as being connected on the front panel of the control unit. The input sensitivity adjust 405, the noise adjust 457 and the length selector 490 are likewise illustrated as being mounted on the front panel 285 of the control unit and are thus illustrated as being disposed in the unit or on the panel. A half-wave rectifier power supply 500 connected to the power supply through leads 501 is provided for receiving an AC input and rectifying it and applying it to the indicating device through connections to the noise indicating circuit 410.

The unit is provided with the control relay 142 and the fail-safe 280 which control a supply of a signal to the receptacle 269, and ACO connector 268 and the fail-safe lamp 282, as heretofore described. The control relay 142 and the output relay 425 of the length selector control the stop-motion relay 263 which controls the stop-motion output receptacle 264. The fail-safe relay is likewise connected to the stop-motion relay for carrying out stop-motion, as heretofore described, with respect to the single level control unit.

The control unit is provided with the "High-Low" sensitivity control switch 230, the sensitivity adjust potentiometer 233 and the frequency cutoff switch 237. Since in this unit both a single level amplifier and a length selector amplifier are used provision is made for connection of two external calibrators for calibrating the amplifiers through the plug or receptacle 227. However, the rotary switch 225 illustrated in FIG. 13 in the single level unit is replaced by a two pole three-throw rotary switch 505, 506. The input sensitivity adjust 405 of the length selector amplifier is connected to the rotary switch pole 506. This switch is operable to three positions: a first position in which the plug 227 for the calibrators is out of circuit with the unit and the output of the transducer is applied to the yarn inspector amplifier 140 and to the input sensitivity adjust 405 of the length selector amplifier through the switch connections 505, 506. A second position in which a yarn inspector calibrator, hereafter described, for the amplifier 140 can be connected to this amplifier for calibration thereof, and a third position in which a length selector calibrator, not shown, for the length selector amplifier is connected thereto for calibrating this last-mentioned amplifier. The switch 505, 506 is illustrated in its first position.

The unit is provided with the major defect counter 267 comparable to the counter in the single level control unit and an additional counter 507 for counting the defects detected as to length is connected to the control relay 425 and the major defect counter, and the control relays 142, 425 as illustrated. In order to provide for selection of the operation to be carried out by the control unit a four pole four-throw switch 510 is provided. The switch is operable to four positions comprising a first position in which the stop motion relay is inoperable. In the second position the apparatus is set so that the stop motion relay is inoperable when an amplitude defect is detected only in which case the apparatus functions comparable to the single level unit. In the third position the additional dimension of sensing by length is established and the apparatus functions to detect defects solely by length and allows the warper to stop for these defects. The switch is operable to a fourth position in which case the unit operates to detect both as to amplitude and length and carry out stop motion in response to long tapering defects and those of a selected diameter or amplitude.

The amplifiers are connected to the compensator through lead 517 and to the transducer output through lead 517. An amplifier input test point 520 is provided.

DUAL LEVEL WITH LENGTH SELECTOR

Another embodiment of the electronic control unit, FIGS. 12, 18a, 18b, 18c and 18d, according to the invention, is substantially the same as the dual level arrangement, heretofore described, but includes an additional dimension of detection, namely the length of the defect. In this control unit the length selector is combined with the dual level arrangement in a manner comparable to the combination with the single level arrangement heretofore described. By means of the dual level with length selector control unit both major and minor defects may be detected on the same basis of not only size but also length. This unit enables the user to allow knots and short defects to pass by undetected, yet to catch longer defects which may be smaller in size. The unit is used for detection, for example of filament loops, slack filaments and long tapering defects. Thus, the dual level control unit which provides detection for defects only, according to the diameter or amplitude, is modified in the arrangement to detect also by length of defect.

The electronic unit, according to this arrangement, includes the basic circuitry heretofore described with respect to the dual level control unit and the length selector heretofore described and illustrated in FIG. 16. In this unit as heretofore in FIG. 12, the block diagram of the circuitry includes all of the blocks illustrated in FIG. 10. A third amplifier comprising the length selector amplifier 400 is connected to the compensator 137' and in parallel with the amplifiers 140' and 325. The length selector amplifier has its output delivered to the third output relay 425 to control devices, as heretofore explained with respect to relays 142' and 327.

It will be understood and remembered that in order to simplify the drawings and discussion the components of this electronic unit have the reference numerals of the dual level control unit and the length selector heretofore described.

The block diagram in FIG. 12 illustrates the use of a YI (yarn inspector) calibrator and length selector calibrator 900 as attached to the dual level control unit with length selector. The YI calibrator is used to calibrate the amplifiers 140, 325 of the unit and is described in detail hereinafter. The length selector calibrator 900 is used to calibrate the length selector amplifier 400 and is not described herein.

The detailed circuitry of the manner in which the length selector amplifier 400 is connected to the dual level control unit to form a dual level with length selector control unit as illustrated in FIGS. 18a-.about.d. The three amplifiers are connected to the compensator 137' through a lead 552. The unit comprises dual level adjustments heretofore described with respect to the dual level control unit. Thus, the unit comprises the "High-Low" sensitivity switch 230' connected to receive the transducer output as hereafter described, the sensitivity adjust potentiometer 233' and the frequency cutoff rotary switch 237' all of which are connected to the NO. 1 amplifier 140'.

The second level adjustment means connected to the No. 2 amplifier 325 comprise the "High-Low" sensitivity switch 361', the sensitivity potentiometer 363', and frequency cutoff rotary switch 364 functioning as heretofore explained with respect to the dual level unit. The calibrator switch 350 illustrated with reference to the dual level unit is modified in this embodiment and its functions are carried out by a three pole-four-throw calibrator switch 555 operable to four positions. In a first position, the position illustrated in the drawing, the external calibrator plug 227' is not connected to the control unit and the transducer output is applied to the sensitivity adjustment means of both amplifiers. In this first position the transducer output is also applied through the switch to the length selector sensitivity adjust 405. This adjust is mounted on the front panel of the unit.

It will be remembered that provision is made for calibrating the three amplifiers of the unit and external calibrator units are connectable to the unit through the plug 227'. Accordingly, in the second position an output of the yarn inspector calibrator, to be hereinafter described, is applied to the No. 1 amplifier 140' and in its third position the output is applied to the No. 2 amplifier 325 for calibrating it. In its fourth position the output of the length selector calibrator 900 is applied to the length selector amplifier 400. It is to be understood that the unit functions to detect defects only in the first position of the calibrator switch 555 illustrated and that in the other positions the warper is stopped and the unit is receiving inputs from the calibrator simulating defects in order to calibrate the unit.

The unit is provided with the fail-safe relay 280' controlling the fail-safe lamp 282' and the ACO connector 268' and the AC signal receptacle 269' are controlled as described above. An DC input through leads 559 is applied to a half-wave rectification circuit 560 providing a DC supply to the indicating circuit 410 of the length selector.

Each of the amplifiers has its respective control or output relays 142', 327 and 425. The stop-motion relay 263' in this unit controls the stop-motion output receptacle 264'. The stop-motion relay can be actuated by the fail-safe relay 280' or any one of the control relays 142', 327 and 425 when the control unit is set to operate and detect defects to which the control relays respond as hereafter explained.

This unit can detect major and minor defects sensed and detected as to their amplitude and long tapering defects. Provision is made for counting these defects in counters 267', 356 and 563 respectively. A switching arrangement, switches 565, 566, 567, is provided for allowing various combinations of the control relays to permit detection of defects in various combinations of amplitudes and lengths and to provide stop-motion control in response to these various combinations.

Accordingly, when the switch 565 is on its "on" position warper stop-motion control is under the control of the control relay 142' associated with the No. 1 amplifier detecting major defects. It being understood that the other switches 566, 567, are in an "off" position as illustrated in this case. With the switch 566 only in an "on" position the control relay 327 controls the stop-motion relay 263' and warper stop-motion is in response to minor defects or defects of a lesser amplitude. With only the third switch 567 in an "on" position the stop-motion relay is under the control of the length selector control relay 425 and warper stop-motion is in response to long tapering defects of a predetermined length adjustably set in the length selector as described in detail heretofore.

It is apparent that either one of the switches 565, 566 can be set on an "on" condition with the third switch 567 on an "on" condition in which case stop-motion control is carried out in response to defects of a given amplitude and in response to defects of a given length. Moreover, each type of defect is counted regardless of the combination set for warper stop-motion control.

LENGTH SELECTOR CONTROL UNIT

According to the invention the control unit can be constructed to carry out warper stop-motion control in response only to the length of defects. In such a construction the control unit, FIG. 21, comprises a power supply 630 having a line input 631 provides power to a voltage regulator 635 and a lamp voltage regulator 633 connected to a lamp 20. The voltage regulator 635 is connected to a compensator 637. The output of the regulator 635 is provided to the length selector amplifier 400 and an output relay 425 controls the stop motion relay 263. The same loop is provided between the compensator 637 and a high voltage supply and oscillator circuit 638 and the phototube 22.

In this arrangement the circuitry corresponding to each of the blocks is that of the basic circuitry heretofore described with respect to the other control units. This control unit will respond solely to the length of defect established by the length selector.

CALIBRATOR

Each type of control unit is provided with a receptacle 227, 227', as heretofore mentioned, into which can be plugged an auxiliary electronic calibrator and sensitivity checking device 700. This device, FIGS. 22 and 23, is automatically actuated every time the warper stops for any reason whatever and it indicates whether or not the yarn inspector is performing properly at the sensitivity for which is was set. Failure of the electronic control unit to operate properly at the present sensitivity is indicated by a light 282, 282'. This device in conjunction with the fail-safe built into the individual control units guarantees complete protection against malfunction of the yarn inspector. In order to simplify the drawings the calibrator 700 is shown connected only in the control unit shown in FIG. 12, however, the calibrator is usable with the other electronic units disclosed.

The electronic calibrator 700 produces pulses of a predetermined size to simulate the defects seen by the phototube in the detecting head. It should be remembered, that the calibrator 700 is calibrating (and/or monitoring as will be described later), the electronic control unit only and not the detecting head of the yarn inspector. The standard calibrator has a plurality for example ten, simulated defect sizes that may be chosen merely by turning a precise selection switch later described. These standard sizes are, for example, 1 percent, 2 percent, 3 percent, 4 percent, 6 percent, 8 percent, 10 percent, 12 percent, 15 percent, and 20 percent, other sizes may be obtained. All of the above sizes are obtained by use of 1 percent resistors, using extremely stable multivibrator circuits, and voltage regulator zener diodes. However, taking all possible errors into account, including mill conditions, the simulated defect sizes may be off by as much as 10 percent from the actual size defect. Therefore, a 1 percent simulated defect may actually be 0.9 percent. A 20 percent defect may actually be only 18 percent. The output of the calibrator has been designed to remain constant over an extremely long period of time. The calibrator functions as follows:

A power supply 704 connectable to line voltage and having a zener diode regulated output provides the voltage for the calibrator. This supply has a switch 706 to apply line voltage to an isolation stepdown transformer 707 having its secondary output connected to a full wave bridge rectification circuit 709. A pilot light 710 indicates in the usual manner when the device is on. A Pi-type filter comprising a pair of capacitors 711, 712 and a resistor 713 reduces the AC ripple from the rectifier to a negligible amount. In order to maintain the output voltage constant, a zener diode regulator 715 is connected across the output. This constant supply voltage is supplied to the rest of the calibrator circuit.

The calibrator proper comprises an astable multivibrator 717 formed by a pair of transistors 718, 719. This multivibrator has a positive feedback built into the circuit so that the transistors will oscillate at a value or free-running frequency determined by the circuit time constant which is determined by combinations of a plurality of capacitors 720, 721, 723 and a plurality of resistors 725--728 whose values are so chosen that a preselected pulse width, for example, of about 0.2 seconds, and preselected repetition rate, or frequency for example of 0.5 seconds, is thus obtained. The output from the astable multivibrator is fed into a differentiating circuit 730 comprising a resistor 732 and a capacitor 733. This circuit "sharpens" the pulse from the astable multivibrator so that it can be used to fire a monostable multivibrator 735 and not have any further influence upon this monostable multivibrator.

A pair of transistors 737, 738 are connected as the monostable multivibrator configuration. The sharpened negative pulse upon leaving the differentiating circuit 730 causes the multivibrator input transistor 737 to conduct heavily which in turn produces a pulse of a given size and width depending only on the monostable multivibrator time constants. These time constants are determined by a combination of resistances 740, 741 and a capacitor 742. The frequency or repetition rate of the pulse from the monostable multivibrator is dependent upon the repetition rate of the astable multivibrator which supplies the triggering pulse. It has been found that to best simulate actual mill conditions a somewhat rounded pulse is best, for example a pulse of 0.001 seconds every half second.

The output of the monostable multivibrator is applied to a pulse shaping network 750 consisting of a diode 751, a resistor 752 and a capacitor 753. This network forms the desired pulse shape. The pulse from the shaping network is applied to the base of an emitter follower transistor 757 to the output of which is connected a zener diode voltage regulator 760, therefore, whatever the input to the base of the transistor 757 over a selected level, for example, 3.9 volts the output is maintained at the selected level. The calibrator is provided with a precision switching arrangement comprising a potentiometer 762 and a rotary switch 763 for placing in circuit a plurality of series resistances 765 each of a selected value for controllably establishing a pulse simulating any defect size that may be obtained or detected by the yarn inspector. A switch 767 provides a bypass for a resistance 768 also providing greater precision adjustment.

The switch is connected to a calibrator relay 769. When the calibrator is connected from a receptacle, for example the receptacle 227, connections are established through the five pin base socket 789 so that if the calibrator is plugged into a yarn inspector electronic control unit and left in it will be automatically placed in circuit by the calibrator relay 769 when the warper is stopped and will not operate while the warper is operating. A receptacle 780 is shortened when the warper is running and open when it is stopped to allow the predetermined calibrator output signal to enter the control unit and this checks or calibrates the control unit. Plug connections 788, 789 are provided for connecting the unit to various models of the control units and a plug connection 790 is provided for connection to a length calibrator, not shown. Thus, in dependence upon the setting of the switch 763 a predetermined signal will automatically be fed into the yarn inspector causing the fail-safe light on the front panel of the control unit to blink. If this blinking occurs, the amplifier of the control unit is working correctly, if no blinking occurs then there has been a loss in output in the amplifier and it should be corrected. Thus, the calibrator can be used to calibrate the yarn inspector and to continuously, if left plugged into the control unit, check the sensitivity level.

While preferred embodiments of the yarn inspector, according to the invention, have been shown and described it will be understood that many modifications and changes can be made within the true spirit and scope of the invention.

Claims

We claim:

1. A detection system for inspecting strands of elongated material such as yarn, fishing line, medical sutures, cord, string, thread and the like while being advanced longitudinally individually or as a multiplicity in sheet form and for inspecting fabric and web materials comprising, circuitry having a lamp from which emanates a beam of light relative to which the material being inspected is moved transversely thereof and including photoresponsive means on which said light impinges to provide voltage signals when defects occur in the material being inspected, first circuit means connected to respond to said voltage signals for generating corresponding signals from selected ones of said voltage signals, second circuit means connected to receive said corresponding signals in a configuration responsive to said corresponding signals and including integrating circuit means for generating composite signals the amplitude of which depends on the quantity and amplitude of said corresponding signals produced in preselected periods of time, means responsive to each of said composite signals generated controlling the movement of said material, in response to at least some of said composite signals and length-adjust means to adjust the quantity of said corresponding signals said second circuit will integrate to determine the length of the defects which are detected on said material being inspected.

2. In combination an automatic photoelectric inspector apparatus and an electronic calibrator for inspecting strands of elongated material, yarn, fishing line, medical sutures, cord, string, thread and the like while being advanced longitudinally and as a multiplicity in sheet form and for inspecting fabric and web materials comprising, a detecting head comprising a source of light, an optical system cooperative with said light source having an optical axis for projecting a substantially collimated inspection beam of light rays across the strand or sheet of strands to be inspected, means providing at least one guide surface over which said strand or sheet of strands pass when being inspected comprising means for disposing said guide surface substantially parallel to said optical axis, a photoelectric unit having means disposed for receiving the light beam rays after projection across said strand or sheet of strands and comprising pulse generating means to generate discrete pulses representative of discrete defects detected by the light beam and in response to modulated light rays causing variations of the amount of light in said beam due to said defects, control circuitry connected to said pulse generating means for establishing variable pulse amplitude effective levels representative of a variable lower limit of diameters of the defects to be detected, and actuating means responsive only to pulses within said limit of amplitudes, an electronic calibrator comprising, means for generating a pulse, a differentiating circuit connected to receive said pulse and sharpen it, a monostable vibrator triggered by said pulse connected to receive said sharpened pulse, a pulse shaping network for shaping the pulse to a preselected shape, means for applying the output of said vibrator to said shaping network, and means controllable for establishing a variable amplitude level for said pulses so that the amplitude level is indicative of a predetermined value of a physical variable.

3. In combination an automatic photoelectric inspector apparatus and an electronic calibrator for inspecting strands of elongated material, yarn, fishing line, medical sutures, cord, string, thread and the like while being advanced longitudinally individually and as a multiplicity in sheet form and for inspecting fabric and web materials comprising, a detecting head comprising a source of light, an optical system cooperative with said light source having an optical axis for projecting a substantially collimated inspection beam of light rays across the strand or sheet of strands to be inspected, means providing at least one guide surface over which said strand or sheet of strands pass when being inspected comprising means for disposing said guide surface substantially parallel to said optical axis, a photoelectric unit having means disposed for receiving the light beam rays after projection across said strand or sheet of strands and comprising pulse generating means to generate discrete pulses representative of discrete defects detected by the light beam and in response to modulated light rays causing variations of the amount of light in said beam due to said defects, control circuitry connected to said pulse generating means for establishing variable pulse amplitude effective levels representative of a variable lower limit of diameters of the defects to be detected, and actuating means responsive only to pulses within said limit of amplitudes, said electronic calibrator comprising, means comprising an astable multivibrator for generating a negative pulse, a differentiating circuit connected to receive said negative pulse and sharpen it, a monostable vibrator triggered by said pulse connected to receive said sharpened pulse, a pulse shaping network for shaping the pulse to a preselected shape, means for applying the output of said vibrator to said shaping network, and means controllable for establishing a variable amplitude level for said pulses so that the amplitude level is indicative of the level of a physical variable.