US2567751A - Magnetic shuttle detector - Google Patents

Description

Sept. 1 l, 1951 Filed Feb. 21, 1950 R. w. WOLKE 2,567,751

MAGNETIC SHUTTLE DETECTOR 2 Sheets-Sheet l Inventor: 'RiChaTd w. Wolke, y W

His Attorn ey.

Sept. 11, 1951 R. w. WOLKE MAGNETIC SHUTTLE DETECTOR 2 Sheets-Sheet 2 Filed Feb. 21, 1950 4-AAAAAAA hqam .EDUEU lllA Wm JmW W d mr a I m m R wk y WW5? His AttOP'ney.

Patented Sept. 11, 1951 MAGNETIC SHUTTLE DETECTOR Richard W. Wolke, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application February 21, 1950, Serial No. 145,337

2 Claims.

My invention relates to textile weavin looms and more particularly to protective apparatus for the detection of abnormal shuttle motion therein.

In conventional weaving looms the shuttle which carries the weft yarn to and fro across the warp yarn may, for a variety of reasons, be deflected or retarded in its normal flight, so that it fails to box properly at the end of it flight. If

the shuttle is not boxed properly when he lay beam and its reed swing forward to press the weft yarn into the fabric, the shuttle is forced into the warp yarn causing breaking thereof and necessitating expensive and time-consuming repairs. Moreover the continuity of properly woven fabric is, broken and in the case of a closed fabric, such as a drying felt for a papermaking machine, the fabric is ruined for its in tended purpose.

Heretofore mechanical feelers have been employed to determine whether the shuttle has boxed at the proper point in the loom cycle and to control the position of stop daggers on the lay beam. If the shuttle is delayed in arriving, the daggers, which are normally moved to an inactive position in response to boxing of the shuttle, remain in their active position and by interference with the breast beam impede forward motion of the lay beam. Through an associated actuating mechanism, power is removed from the loom and a brake is applied. Since detection by the feelers occurs near or at the end of the shuttle flight, and therefore late in the loom cycle, if it is necessary to halt the progress of the lay beam relatively high forces are required to produce rapid deceleration thereof. The shock effects resulting from such decelerating forces are responsible for a considerable amount of costly damage to looms and place a limitation on maximum loom speeds.

Recently magnetic detecting devices have been employed whereby the position of a shuttle may readily be sensed at any desired point in its flight. An electrical signal indicative of the position of the shuttle relative to the cycle of the loom is thus provided to actuate a stopping mechanism in the event of abnormal shuttle motion. Such a signal may be derived at an earlier point in the loom cycle than is possible with mechanical feelers, and accordingly a greater period of time is available to stop the loom and correspondingly reduced decelerating forces may be applied thereto.

In utilizing a signal from a magnetic shuttie detecting device it is necessary to interpose a suitable control apparatus between the detector and the particular stopping means employed. The latter may be, for example, dynamic braking of electric driving motors. It is the function of the control apparatus to effect comparision of the progress of the shuttle in its flight with the time cycle of the loom, and to effect stopping of the loom in the event of faulty shuttle motion.

It is accordingly a principal object of my invention to provide a new and improved control apparatus which is particularly suitable for use in looms for the purpose of effecting shutdown thereof in the event of faulty shuttle motion.

It is a further object of my invention to provide a new and improved control apparatus for use with a magnetic detecting device to detect faulty shuttle motion in weaving looms and to effect stopping of the looms in the event thereof.

In accordance with a preferred embodiment of my invention I provide an arrangement whereby a pulse from a magnetic detector, positioned to be responsive to motion of the shuttle relative to the lay beam, is compared with motion of the loom by the use of a switching device actuated by the loom. An electromagnetic device, such a a relay, is normally energized through the switching device. The latter is opened for a short period during each loom cycle, however, and during this period the electromagnetic device is normally energized through an electron discharge device which is rendered conductive by means of a pulse from the magnetic detecting device. If the pulse from the detector does not occur at the proper time in the loom cycle, or, in other words, does not occur in synchronism with opening of the contacts of the switching device, the electromagnetic device is deenergized to effect stopping of the loom through a braking device.

My invention will be better understood from a consideration of the following description taken in connection with the fiigures of the accompanying drawings, and its scope will be pointed out in the appended claims. In the drawings, Fig. 1 is a schematic elevational view of a portion of the lay assembly of a loom; Fig. 2 is a cross section taken along line 2--2 in Fig. 1; Fig. 3 is an enlarged view of a magnetic detecting device shown generally in Fig. 1; and Fig. 4 is a schematic diagram of a magnetic shuttle detecting apparatus constructed in accordance with my invention.

Referring now to Fig. 1, there is shown an elevational view of the lay assembly I of a weav- 3 ing loom. Shown in conventional relationship are the lay swords 2 with their journals 3, the lay beam 4, the crankshaft together with journals 5 and cranks 1, and shuttle boxes 8 and 3. A magnetic detecting device III is positioned in the lay beam near the path of flight of the shutt e II. A rotary switch assembly I2 is positioned at one extremity of crankshaft 5 and is arranged to have its contacts actuated in response to rotary motion of shaft 5. Magnetic device It and switch I2 will be more fully described hereinafter.

Fig. 2 is a cross section taken along the line 2-2 of Fig. 1 showing, in addition to certain of the elements of the lay assembly shown in Fig. I, the reed I3 and portions of the heddle I4 and the warp yarn I5. The extreme rearward and forward positions occupied by the lay assmbly in the operation of the loom are shown, respectively, by solid-line and broken-line views of lay swords 2, lay beam 4 and reed I3, these elements being given prime numerals in the forward position. The shed I5 is formed by groups of alternate strands of yarn, which are separated by action of the heddle, and reed I3 when the lay assembly is in it rearward position.

Shuttle I I is thrown to and fro across the lay beam by action of the picker sticks (not shown) carrying the weft yarn through shed I5. Following a flight across the lay beam, shuttle II is boxed in either shuttle box 8 or 9 (shown in Fig. 1) and the lay assembly is moved forward to force the weft yarn into the fabric I! at the fell I8. The action of the lay assembly and shuttle, as described, is conventional in nature and is included for the purpose of assisting in understanding my invention.

Attention is now directed to Fig. 3 which is a cross section of magnetic detecting device ID, as positioned in lay beam 4, and a portion of shuttle II showing a magnetic element I9 embedded therein. Device ID comprises a pair of coils 20 and 2| positioned on legs 22 and 23 of a generally U-shaped core 24, the center portion of which is a permanent magnet 25. Legs 22 and 23, which are preferably formed of a plurality of relatively thin laminations of a magnetic material such as silicon steel, are engaged with magnet 25 at joints 26 and 21 in a manner to assure substantially no air gap between magnet 25 and legs 22 and 23. The assembly of coils 20 and 2I and core 24 is positioned on a non-magnetic base plate 28 in a cavity 29 of lay beam 4 and may be secured to the latter by screws or any other suitable fastening device (not shown). The depth of cavity 29 is such that coils 20 and 2| and the extremities of legs 22 and 23 are positioned slightly below the surface 30 of lay beam 4.

Shuttle II, in its flight across the lay beam, generally is in contact with the surface formed by the strands of warp yarn I5 which are shown in cross section in Fig. 3. A gap 3I exists between the upper surface 30 of lay beam 4 and lower surface 32 of shuttle II. Magnetic element I9, which is positioned in shuttle I I to be flush with surface 32, is a relatively thin member which may be made up of laminations of a magnetic material such as silicon steel. The exact size of element I9 is dependent to a large extent on the length of gap 3| and the speed of shuttle II and may be varied to suit the gap encountered in weaving a particular fabric.

Attention is now directed to Fig. 4 which is a functional schematic diagram of the control apparatus to which signals are supplied from magnetic detector I0 and rotary switch I2 to effect stopping of the loom in the event of faulty motion of shuttle II. Rotary switch I2 comprises a fixed contact 33 and a movable contact 34, the latter being fixed to an arm 35 arranged to rotate about a pivot 36. Arm 35 is normally forced by a compression spring 31 into engagement with a cam 38. Cam 38 is fixed on a shaft 39, and the latter is connected to crankshaft 5, as shown in Fig. 1, so that cam 38 is rotated by motion of shaft 5. Cam 38 is provided with a raised portion 40 at one point on its periphery. Contacts 33 and 34 are forced into electrical engagement with each other by the action of spring 31 against arm 35 except when raised portion 40 of cam 33 engages the opposite side of arm 35. In the latter case, contacts 33 and 34 are forced apart and the electrical engagement therebetween is broken. Electrical connections to switch I2, for use in the control apparatus, are made to arm 35 and a mounting block 43 to which contact 33 is fixed. Cam 38 is preferably formed of an insulating material and the conducting elements of switch I2 are mounted on a suitable base 44 of an insulating material.

The control apparatus shown in Fig. 4 comprises principally a pulse rectifier circuit 50 provided with pulse signals from magnetic detector I0; an amplifier and pulse-shaper circuit 5I to modify signals from rectifier 50; and an output circuit 52 provided with signals from rotary switch I2 and circuit 5|, and arranged to actuate a magnetic switching device. 53. Switch 53 may be connected to any suitable loom-stopping ar rangement, such as a dynamic braking circuit (not shown).

Rectifier circuit 50 includes an electron discharge device 54 having an indirectl heated cathode 55, a heater 5'! and an anode 58. One terminal of heater 5! is connected to ground and the other terminal is connected to the positive terminal of a direct-current source shown as a battery 59. The negative terminal of battery 59 is connected to ground through a switch 5|. Windings 20 and 2I of magnetic detecting device III are connected in seriesrelation in an aiding sense. One end of the series combination of windings 20 and 2| is connected to cathode '55 and the other end is connected to ground. A resistance BI is connected between cathode 55 and ground. A capacitor 64 and a variable resistance 65 are connected in parallel relation between anode 58 and ground.

Amplifier and pulse-shaper circuit 5| includes an electron discharge device 56 having a pair of indirectly heated cathodes 61, a pair of heaters 68, a pair of anodes 59, and a pair of control electrodes 10. While device 65 is shown as a dual triode, it will be understood that a single triode may be employed if desired. Heaters 68 are connected in parallel relation between ground and l the positive terminal of battery 59. Cathodes 51 are connected to ground. Control electrodes II are connected together andv are connected to anode 58 of device 54 through a coupling resistance II. Anodes 69 are connected together to form a junction point 12 and are connected through a pair of serially connected resistances I3 and I4 and a time-delay switch 15 to the positive terminal of a battery 15. The negative terminal of battery I5 is connected to ground through switch 60. Switch I5 is of the thermally actuated type and is provided with a heater I1 and a pair of normally open contacts 13. The latter are arranged to be closed by a thermal dea vice, such as a bimetallic strip, in response to heating thereof. Heater 11 is connected between ground and the positive terminal of battery 56. The junction point between resistances 13 and 14 is connected to ground through a capacitance 19. Junction point 12 of anodes 69 is connected to ground through the series combination of a' capacitance 80 and a resistance 8|.

Output circuit 52 includes an electron discharge device 82 preferably of the gaseous discharge type having a cathode 83, a heater 84, an anode 85, a screen electrode 86, and a control electrode 81. Heater 84 is connected between groundand the positive terminal of battery 59. Control electrode 81 is connected through a coupling resistance 9| to the junction point 92 between capacitance 80 and resistance 8|. Electrode 81 is also connected to ground through a capacitance 93. Electrode 86 is connected to cathode 83 and the combination thereof is connected to the common point 88 between a pair of resistances 89 and 90, the latter being connected in series relationship across the output of battery 16 in a potential-dividing arrangement. More particularly, the series combination of resistances 89 and 9|] is connected between ground and the common point 94 between switch contacts 18 and resistance 13. Anode 85 is connected to point 94 through the series combination of actuating coil 95 of magnetic switching device 53 and also a pair of normally open contacts 96 thereof. Device 53 is preferably a sensitive relay such as the type commonly known as a telephone relay. A resistance 91 and 2. ca.- pacitance 98 are connected in parallel relation with coil 95. One terminal of rotary switch I2 is connected to the common point 99 between coil 95 and contacts 96 and the other terminal of switch I2 is connected to ground. Switch 53 is provided with a second pair of normally open contacts I00 which may be connected in any desired loom-stopping circuit (not shown).

In operation, shuttle travels to and fro across lay beam 4 causing magnetic element 9 to be moved across magnetic detector ID. A magnetic fluxis normally established by magnet 25 in a series path including leg 22, the air gap between the upper extremities of legs 22 and 23, and leg 23. The path of flux between legs 22 and 23 is shown approximately in Fig. 1 by magnetic flux lines |0|. As magnetic element I9 passes through the air gap between legs 22 and 23, the reluctance of the air gap is modified, thereby causing a change in the fiux established by magnet 25 and causing pulses of voltage to be induced in windings 20 and 2| of detector H). The passage of magnetic element l9 across detector I!) initially causes an increase in the flux circulated by magnet 25 followed by a decrease of the flux, and hence the induced pulses are initially positive and then negative, or vice versa, as shuttle l and magnetic element l9 approach and then leave the vicinity of detector H). The polarity of the pulses is independent of the direction of travel of shuttle While a single 6011 may be employed in detector Hi, the use of a pair of coils connected in series relation, as in the present embodiment, provides a higher voltage pulse which is more readily utilized in the control apparatus.

In initially placing in operation the control apparatus shown in Fig. 4, switch 60 is closed to apply voltage from battery 59 to heaters 51, 68, 84 and 11 of electron discharge devices 54, 65 and 82 and time-delay switch 15, respectively.

thereby, thus permitting the negatively induced voltage ofwindings 20 and 2| to be impressed on resistance 65 and capacitance 64. -Capacitance 64 is immediately charged to the voltage impressed thereacross, which is preferably on the order of 4 or more volts. As the amplitude of the pulse voltage returns to zero, capacitance 64 discharges through resistance 65 at an exponential rate determined by the relative values of capacitance 64 and resistance 65.

When the voltage across resistance 65 exceeds a predetermined negative value, as, for example,

approximately -2 volts, electron discharge device 66 is in a state of cutofi. Device 66 remains in the cutoff state for a period of time determined by the amplitude of the pulse voltage and the setting of resistance 65. By varying the value of resistance 65, the period of cutoff of device 66 may be varied, the degree of variation preferably being, for certain applications, from zero to approximately milliseconds. While device 66 is in a state of cutofi, the potential of junction point 92 assumes a positive value, preferably approximately 25 volts, this value being achieved immediately as device 66 is cut oil. Since the time constant of capacitance 86 and resistance 8| is long compared to the time constant of capacitance 64 and resistance 65, the voltage across re sistance 8| is essentially constant while device 66 is in a state of cutoff. Thus the voltage across resistance 8| is essentially a square-wave pulse, the width or duration of which is determined principally by the setting of resistance 65.

This square-wave pulse of voltage is impressed on control electrode 81 of device 82, which is rendered conductive thereby. Whether or not device 82 conducts, however, is dependent on rotary switch |2 which under certain conditions is arranged to provide a short circuit across device 82, and on contacts 96 the closing of which is necessary to complete the circuit of device 82. Whenever switch |2 is closed, winding of relay 53 is energized and contacts 96 are closed. It will be noted that when contacts 96 are closed, contacts Hill of relay 53 are likewise closed. Contacts Hill are connected in a suitable loom-stopping circuit which is arranged to interrupt operation of the loom in response to opening of contacts I06. Thus for continuity of operaiton of the loom to be maintained, it is necessary for relay 53 to be energized at all times.

Switch |2, which is opened and closed in response to motion of crankshaft 5, is closed during the greater portion of the loom cycle but is arranged to be open during the relatively short period during the loom cycle when shuttle normally passes in the vicinity of magnetic detector Hi. When switch I2 is opened during each loom cycle, therefore, it is necessary that device 82 be rendered conductive so that the actuating current for relay 53 previously flowing through switch |2 may flow through device 82 and dropout of relay 53 does not occur. In other words, the signal from detector l9, which is responsive to passage of shuttle II in the vicinity thereof and which render device 82 conductive, must occur substantially in synchronism with cpening of switch I2, which is indicative of a predetermined point in the loom cycle, to prevent deenergization of relay 53 and stopping of the loom.

The detailed operation of the principal portions of the control apparatus having beendescribed, the over-all operation of the apparatus will now be considered to assist in the understanding of the invention. As shuttle II makes a flight across the loom a voltage pulse is provided by detector I through cooperative action of magnetic device I9 therewith. The pulses obtained in this manner, however, are relatively weak and are of variable magnitude and duration, making them generally unsuited for rendering device 82 conductive. By the use of amplifier and pulse-shaper circuit substantially squarewave pulses are obtained, the duration of which may be varied by adjustment of resistance 65. The square-wave pulses thus obtained are impressed on device 82 which is rendered conductive thereby. Device 82 does not conduct, however, unless switch I2 is open since the latter, when closed, short circuits device 82.

Relay 53 is maintained closed during the greater portion of the loom cycle by switch I2. However, during a relatively short portion of the cycle switch I2 is open and relay 53 tends to drop out. It is during thi period that shuttle II in a normal flight passes in the vicinity of detector I0. I-f shuttle II is traveling normally the pulse signal provided by detector I0 renders device 82 conductive prior to opening of switch I2. When the latter opens, device 82 conducts current to complete the circuit of relay 53 thereby preventing drop-out thereof. If device 82 is of the gaseou discharge type, as is preferably the case, conduction therein, once initiated, continues even though the signal pulse dies out until the point in the loom cycle when switch I2 is closed. Closing of the latter short circuits device 82 and prevents conduction thereby. Following dying out of the signal pulse and closing of switch I2, device 82 is no longer conductive and is thus ready for the next loom cycle.

If the signal from detector III is out of synchronism with the opening of switch I2, device 82 is not rendered conductive at the proper time and, when switch I2 opens, relay 53 is deenergized causing the loom to be stopped. Although device 82 may be rendered conductive by a signal from detector I0 at a later than normal point in the loom cycle due to lateness of the shuttle in its flight, it will be noted that after relay 53 is deenergized by opening of switch I2 contacts 88 are opened, thereby preventin the reclosing of relay 53 by device 82. Should the shuttle be too early in its flight, the signal pulse dies out by the time switch I2 opens so that device 82 is no longer conductive, causing relay 53 to be deenergized by opening of switch I2. It will be seen from the foregoing that it is necessary for the opening of switch I2, which may b regarded as instantaneous, to occur during the period when control electrode 81 of device 82 is provided with a potential which renders device 82 conductive. Thus it is desirable to provide this Period with a predetermined duration, which is readily accomplished by the use of a square-wave pulse. It is further desirable that this duration be readily adjustable to take account of normal inconsistencies in shuttle travel and for loom conditions, which is accomplished conveniently by adjustment of resistance 65.

In the embodiment of my invention herein shown and described a single magnetic detecting device III, positioned approximately at the center of lay beam 4, is employed to detect motion of shuttle II. The use of a single detector in this manner generally provides reliable and adequate indications of normal shuttle motion. Furthermore, the use of a single detector at the mid-point of shuttle flight has the advantage 0! indicating faulty shuttle motion at a relatively early point in the loom cycle to allow maximum time for stopping the loom to prevent damage to the fabric. In certain cases, however, it may be desirable to employ more than one detector located, for example, near the extremities of the lay beam. In such cases additional detector windings may readily be connected in additional rectifier circuits similar to circuit 50, the rectified signals therefrom being supplied to amplifier and pulseshaper circuit 5I in the manner previously described.

While I have shown and described a preferred embodiment of my invention, it will be under= sto'od that my invention may well take other forms and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope oi the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. For use in a weaving loom having a shuttle and means to move said shuttle from an initial position in a flight toward a final position during each cycle of motion of said loom, said flight normally being at a predetermined velocity, electromagnetic means for providing a signal pulse responsive to passage of said shuttle in the vicinity of a predetermined point in said loom between said initial and final positions, means for providing a secondary pulse of predetermined duration in response to said signal pulse, switching means responsive to motion of said loom, said switching means being closed during a substantial portion of said cycle of motion and open during the remainder of said cycle, opening of said switching means being efiected at a predetermined time in said cycle, electromagnetic switching means for effecting stopping of said loom, said stopping being effected in response to deenergization of said electromagnetic switching means, and an electron discharge device having a cathode, an anode and a control electrode, said electron discharge device being rendered conductive in response to impressing of said secondary pulse on said control electrode, said firstmentioned switching means in the closed condition thereof constituting a first means to efiect energization of said electromagnetic switching means and said electron discharge device being connected to form a second means to effect said energization when said electron discharge device is conductive, deenergization of said electromagnetic switching means and stopping of said loom being effected in response to opening of said firstmentioned switching device prior to said electron discharge device being rendered conductive in response to said secondary pulse.

2. For use in a weaving loom having a shuttle and means to move said shuttle from an initial position in a flight toward a final position during each cycle of motion of said loom, said flight normally being at a predetermined velocity, an electromagnetic device for providing a signal pulse responsive to passage of said shuttle in the vicinity of a predetermined point in said loom bewave pulse having a predetermined duration, a

switch actuated in response to motion of said loom, said switch being closed during a substantial portion of said cycle and open during the remainder of said cycle, opening of said switch being eifected at a predetermined time in said cycle corresponding to the time in said cycle when said shuttle normally passes in the vicinity of said predetermined point, an electromagnetic relay for eifecting stopping of said loom, said stopping being effected in response to deenergization of said relay, and an electron discharge device having a cathode, an anode and a control electrode, said electron discharge device being rendered conductive in response to impressing of said square-wave pulse on said control electrode, said switch in the closed condition thereof eonstituting a first conducting path to efiect energization of said relay and said electron discharge device being connected to form a second conducting path to effect said energization, deenergization of said relay and stopping of said loom being effected in response to opening of said switch prior to said electron discharge device being rendered conductive in response to said square-wave pulse.

RICHARD W. WOLKE.

No references cited.

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