Patent Publication Number: US-3874198-A

Title: Apparatus for regulating pulsatory operation of an electromagnet in a circular knitting machine

Description:
United States Patent 1191 Kouklik et a1.  
 1 1 APPARATUS FOR REGULATING PULSATORY OPERATION OF AN ELECTROMAGNET IN A CIRCULAR KNITTING MACHINE [75] Inventors: Ivo Kouklik; Jarosiav Lorene, both of Trebic. Czechoslovakia [73] Assignee: Elitex. Zavody textilniho strojirenstvi generalni reditelstvi. Liberec, Czechoslovakia 22 Filed: Apr. 24, 1972 [21] Appl. No.: 246,791  
 [30] Foreign Application Priority Data Apr. 30. 1971 Czechoslovakia 313572 [52] US. Cl. 66/50 R, 317/D1G. 4 [51] Int. Cl D04b 15/78 [58] Field of Search 66/50 R, 50 B, 25, 75;  
 317/DIG. 4  
 [56] References Cited UNITED STATES PATENTS Farmer 66/50 R [111 3,874,198 1451 Apr. 1, 1975 3,634,733 1/1972 Boyer 317/DIG. 4 3.660.730 5/1972 Mason .7 317/D1G. 4 3.665.731 5/1972 Groezinger 66/50 R 3.702.425 11/1972 Hoffman et a1 317/D1G. 4 3,708,726 1/1973 Puvogel 317/D1G. 4 FOREIGN PATENTS OR APPLICATIONS 1,107,580 3/1968 United Kingdom 66/50 R Primary Examiner-Wm. Carter Reynolds Attorney. Agent. or Firm Murray Schaffer [57] ABSTRACT Apparatus for regulating the pulsating operation of eiectromagnet control means for selecting the appropriate knitting instrumentalities comprising a main source of DC. current for activating the electromagnet. The source is provided with circuit means for causing a rapid current rise in the winding of the electromagnet, circuit means for thereafter maintaining the current in said winding at a constant level for a predetermined interval and means for subsequently rapidly dropping the current in said winding on the expiration of the predetermined interval.  
 8 Claims, 2 Drawing Figures E bI .L W  
 APPARATUS FOR REGULATING PULSATORY OPERATION OF AN ELECTROMAGNET IN A CIRCULAR KNITTING MACHINE BACKGROUND OF INVENTION The present invention relates to an apparatus. particularly to a circuit for regulating the pulsating operation of the solenoid control means for effecting operation of knitting instrumentalities in circular knitting machines.  
  Com cntional knitting machines are provided with knitting instrumentalities such as needles, etc., which are individually or cooperatively operated in selected sequence to provide a patterned knit product. Electromechanical means such as electromagnets or solenoids are employed to control the movement of such instrumentalities. The elcetromagncts are fed signal impulses selectively from electronic patterning means such as a recorded matrix and pulse generators. Such electronic patterning means are described, for example, in our copending applications, Scr. Nos. 246,972; 246,263 and 246,699 now abandoned based upon our Czechoslovak applications PV 3l32, PV 3133, and PV 3l34, respectively, all filed Apr. 30, l97l.  
  In the heretofore known devices a control pulse signal derived from the matrix means causes the electromagnets or solenoids to act upon the appurtenant movable mechanical needle elements which in turn cause them to be brought into their operative positions as the cylinder is rotated. The maximum speed of the revolution of the needle cylinder for any given gauge of knitting machine is dependent upon the time needed within a control pulse cycle for mechanically adjusting the appurtenant movable clement (needle) into its operative position by means ofthe elcctromagnct. This is particularly significant for the finer gauges. The given interval necessary for this operation is determined by the time needed after receipt of a control pulse to raise the current in the coil of the electromagnet to operating condition, the interval of impression of this constant operating current, and the velocity or speed of current drop, at the end ofthe control pulse. Between separate working cycles, a break always occurs, during which no eurrcnt flows through the coil of the elcctromagnet. During this latter time interval, the selected mechanical element is in its operative position, i.e.: the position into which it has been introduced by the electromagnet during the control pulse, and it is fixed in that position by means of a known device, for given transitory time, while the needle cylinder rotates to advance a subsequent knitting instrumentality into association with the elcctromagnet.  
  A disadvantage of the known devices consists in the limitation of the maximum number of revolutions and the speed of the needle cylinder, particularly with finer gauges. These limitations are caused by the fact that the time intervals need to first raise and then drop the running current in the coil of the electromagnet are too long and result in the undue shortening of the time interval actually needed for the operation of the electromagnet itself. The relatively long time, within the rest or break time of the electromagnet, during which the power and voltage values in the separate elements of the knitting machine are brought to the initial state and thus enabling the reinitiation of the next control pulse, is also disadvantageously long.  
  It is the object of the present invention to provide an improved circuit arrangement for regulating the knitting machine instrumentalities control elements, which overcome the difficulties of known devices.  
  It is another object of the present invention to provide an improved circuit for the control means described, which shortens the operating time intervals and which permits the operation of solenoid or electromagnetic devices at increased speeds.  
  It is a further object of the present invention to provide an electronic regulating circuit for the control elements of circular knitting machines which enables the use of such machines at higher speeds, and with finer gauge knitwork.  
  These objects, other objects and advantages will be seen from the following disclosure.  
 SUMMARY OF INVENTION According to the present invention the apparatus for regulating the pulsating operation of electromagnet control means for selecting the appropriate knitting instrumcntalities comprises a main source of DC. current for activating the electromagnet. The source is provided with circuit means for causing a rapid current rise in the winding of the electromagnet, circuit means for thereafter maintaining the current in said winding at a constant level for a predetermined interval and means for subsequently rapidly dropping the current in said winding on the expiration of the predetermined intcrval.  
  The operation is dependent upon a signal pulse received from the patterning recording means, which provides a pulse signal for activation ofeach of said circuit means. Preferably, the time intervals for effecting the circuit operations, particularly the time interval for maintaining the constant current level, is adjustable and selectively variable.  
  Full details of the present invention are given in the following description and in the accompanying draw mgs.  
 BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:  
  FIG. 1 is a diagram showing the circuit of the present invention, and  
  FIG. 2 is a diagram of the currents produced in the operation of the present circuit during the pulse operation of the electromagnet and their time dependence upon operation of the circuit.  
 DESCRIPTION OF INVENTION Before turning to the description of the present invention, it is to be noted that various elements, devices, and structure relating to the present invention are shown in greater detail in the companion application referred to in the preamble of the present specification. Such details are not described at length herein since they are not believed necessary for a full explanation of the present invention. However, reference is made to the disclosures of the aforementioned applications, as if they were more fully disclosed herein.  
  Turning to FIG. I, the present invention is embodied in circuit apparatus comprising a pair of constant DC. voltage supply sources Um and U of which the first is larger than the second. Connected in series with the first supply source U at the positive terminal through a lead 1 is a self-breaking, automatic switch member 2 (preferably a thyristor adapted to break when zero current is impressed on it) a resitor 3, a choke 4, comprising a winding and a core, the winding of an electromagnet 5 and a second switch element 6 such as a thyristor, photothyristor or other form of transistorized switch element. The first switch element 2 is controlled by electric pulses from point 7 while the switch element 6 derives its control pulses from point 8. The control pulses are received from the pattern record, matrix and pulse generating means of the type described in our aforementioned applications, and by selective sequential operation function via the regulating circuit of the present invention to activate the electromagnet S which operates the needle or knitting instrumentalities of the knitting machine (not shown).  
  Connected at point 9, between the positive terminal of the first source U, and the first switch element 2, is a line it) on which a diode ll, oppositely directed to that of the switch 2. is arranged. The line I is connected at point 12 between the electromagnet and the second switch 6 so that the diode ll bridges in parallel the first switch 2, the resistor 3, the choke 4 and the electromagnet 5. Bridging lines I and 10. between points 14 and I3 respectively is a line 15 on which another resistor ]6 is arranged. Extending from point 14, in parallel across the electromagnet S and the second switch 6, is a line 17 on which a capacitor 18 is arranged. The line 17 is connected at point 19 to line I on the opposite side of the switch 6. The resistance of the winding of the electromagnet 5, the inductance of its core and the capacitor 18 form a resonant circuit. Preferably, the resistance ofwinding of the electromagnet 5 is maintained low as to obviate dampening of the circuit. Further, bridging the capacitor 18, between points 20 and 2| is a line 22 on which are serially connected a distributing or separating diode 23, an adjustable resistor 24 and the second D.C. supply source U The second source U is provided with a lower voltage level than the first DC. voltage source U Both sources may be adjustable. Bridging the resistor 3 and the choke 4 between points 25, on the line 22, and the point 26, on the line I. is a line 27 on which is arranged a fourth diode 28. Finally, between point 9 and point 29 bridging the first source of voltage U,,, is another line 30 on which is arranged a variable, adjustable capacitator 31.  
  The values, functions and circuit operation of the elements catalogued above may be best seen by a simultaneous description of the sequence of the circuit operation and of the graphical form of the current timeinterval and peak level parameters produced, as in FIG. 2. At the initial state of operation and prior to the introduction of pulses, through points 7 and 8 the switch elements 2 and 6 are disconnected, i.e. non-conductive,  
 although the DC. sources supply current. The capacitor 3] is charged to its rated adjusted value by the first source U,,,. The capacitor 18 is capable of being charged by either source U through circuit lines 1, l0, l5, l7 and l or by source U through circuit lines 22, I5 and [7. Generally, however, in the absence of pulses on either point 7 or 8 the capacitor 18 is charged to the nominal voltage value of the first D.C. source U,, through the resistor 16. Since the normally lower voltage sourcc U is split by the separating diode 28 and the distributing diode 23 does it not initially effect the charge on the capacitor 18 made by the higher voltage source U,,,. The time constant required to charge capacitor 18 through resistor 16 is so great that it requires the electromagnet 5 to be in an at rest condition so that current can not pass through the resistor 16. The time interval between pulses at points 7 and 8 is sufficiently large to allow this charging of the capacitor 18 via the resistor 16.  
  The capacitor 18 is, however, instantly charged by means for causing a rapid current rise therein, when an actuating pulse is applied to point 7. This pulse closes. i.e. makes conductive, the switch element 2 so that the current from source U,, changes the capacitor 18 through current lines l, 17 and 1. This path bypasses the resistor l6, since this resistor is of such a high resistance. The capacitor 18, will be charged actually to the nominal voltage of U less the drop across elements 2, 3 and 4. Separation of the voltage level between sources U and U is provided by the unidirectional separating diode 23.  
  The capacitor 31 normally has no practical influence on the charging of capacitor 18. The nominal voltage value on the capacitor 3! is maintained continuously and independently by the source U regardless of the charging of capacitor 18. As will be seen later the capacitor 3] absorbs from the electromagnet 5 energy, when switch element 6 is non&#39;conductive. Any excess voltage then charged to capacitor 3], beyond the value of U may be applied to charge capacitor 18 when the switch element 2 is conductive. It will not, however, be applied via resistor 16, due to its high resistance and the excessive time constant of the capacitor 18.  
  To operate the knitting instrument via the actuation of the electromagnet, a pulse is applied at point 8 clos ing switch 6. This immediately causes the creation of circuit means for causing a rapid current rise in the winding of the electromagnet 5 by the discharge of the capacitor 18.  
  The introduction of the control pulses to point 8 causes the closing of switch element 6, whereupon the resonance circuit, which is constituted by the resistance of the electromagnet winding, the inductance of electromagnet 5, and the capacity of capacitor 18, is closed via line I in the portion situated within points 14 and I2. and via line 17. While the source is supplied at a constant voltage to U,,,, when the switch 6 is closed it does not have any effect due to the high resistor constant of resistor 16. The capacitor 18 begins to discharge via the winding of electromagnet 5 and the current in this circuit rises, as seen in FIG. 2 sinusoidally in accordance with curve 1,, until it reaches, within time interval 1,, its maximum value i,,,,,,. The slope of the gradient of voltage rise, is determined by the voltage value on capacitor 18 (i.e. by which it is charged) and the constants of the resonance circuit. The resistance of the electromagnet winding, of course, has a low value which prevents any substantial damping of the circuit. When switch element 6 is closed, the resonance circuit formed by inductance of the electromagnet 5 and by condenser 18 (at capacity) closes, whereby the condenser resonates within the time I, only. The inductance and circuit capacity values are determined by the time t, (for a small-diameter knitting machine the time is lower than 1 milisecond) a calculated according to Thomsons formula 1, 1r/2 1/ LC. Practically, the circuit does not resonate but a current rise up to time t, is utilized only, (maximum current) and the current is then kept by means of the source U Maintenance of current through the eleetromagnct 5, even after termination of the pulse on switch element 2, so as to obtain an operating pulse of sufficient length to operate the knitting instrument after discharge of the capacitor 18, is provided by the second DC source U through its circuit means with the electromagnet. The length of the operating pulse period Tp corresponds to the time switch element 6 is rendered conductive by application of a pulse at point 8.  
  As soon as the voltage on capacitor 18 drops at point 14 to such an extent that it equals the voltage of the second DC. voltage supply U the permeation level set by means of the adjudstablc resistor 24, and separating diode 23 permits the formation of a circuit which is constituted by line 1 within the part between point 20, 2l, and by line 22 connected in parallel thereto to be closed. Thcrcupon current begins to flow through winding of clectromagnet 5 from the second D.C. voltage supply U via adjustable resistor 24, separating diode 23 and switch element 6. This is within the time 1 The current value I in this circuit, as seen in FIG. 2, has a course which corresponds to curve l the actual current value i being determined by voltage value ofthe second DC. voltage source U less the value of the adjustable resistor 24 and the sum of voltage drops at the separating diode 23. the resistance of the winding of electromagnet 5 and switch element 6. Should the voltage of the second DC. voltage supply U be changed as for example by reducing it, the current value i would flow in the winding of electromagnet 5 according to the course of curve a, shown in dash lines The time during which the current flows through the winding of clectromagnet 5, depends upon the length oftime of closure of switch element 6, i.e. from the length ofa driving pulse T, as seen on curve 2 The state or position A denoting cut-off and state B closure of switch element 6.  
  At the termination of an operating pulse Tp (i.e. after cut-off of a pulse at point 8 to switch element 6, the magnetic energy accumulated in the core of the electromagnet 5 inductively charges capacitor 31 via lines 1,10 and 30 through diode ll. The current i, in the winding of the eleetromagnet 5 drops, as seen in curves 1,, or 0, reaching its zero value within the time interval 1;, or 1 Thus capacitor 31 is charged with a voltage from clectromagnct 5. in excess ofthe rated voltage derived from the first DC source Ub The voltage in crease on the capacitor 31, within the limits of its nominal value, is determined by the energy of the electromagnet 5. Any additional charge from the capacitor 18 on discharge of the clcctromagnet will be accepted by capacitor 31 since such charge will be well within the nominal 1- boundaries of tolerance of the capacitor 31.  
 During the time interval I5, after the ending of the opcrating pulse Tp, a control pulse is introduced at point 7 causing the closing or conductivity of the self-braking switch element 2. This operation is shown in FIG. 2, as curve 3-, in which C shows the cut-off or opening of switch element 2 and D the closing or conductivity of the switch element 2. At the closing of switch element 2. a resonance circuit is set up including on the one hand the capacitor 18 and on the otherthe capacitor 3|. Both are employing circuit lines I; elements 2. 3 and 4, line l7. and 30. Capacitor [8 will be charged from source U,,., as described before, but in the event excess voltage is formed in the capacitor 31, the capacitor 18 will act to absorb the excess until the capacitor 3| stabilizes at its rated value being further charged by source U,,,. The capacitor 3| and capacitor 18 cannot be discharged simultaneously since switch element 2 is open, i.e. non-conductive, during application ofa pulse at point 8, causing discharge of the capacitor l8.  
  As noted earlier, when switch element 2 is conductive and switch element 6 is non-conductive, the path through resistor 16 is of very little significance. because the time constant of capacitor 18 is several orders higher than the period of non-conductivity through the electromagnet 5. Thus capacitor 18 is charged from U,,, basically by the path through switch element 2, resistor 3. choke 4 and line [7. In FIG 2 the current through resistor 3 is seen as curve 4;, which reaches its maximum during the time interval I&#34;, being well within the time interval constituting the pulse signal to point 7.  
  During time interval 1;, the voltage value on the capacitor 18 at point [4 is only slightly higher than the voltage value on self-breaking switch element 2 at point 26, and current begins to flow through diode 28. The difference in voltage between points 14 and 26 is brought about in the following manner: At point 9 the voltage is equal voltage of the source U At point 26 the voltage is less by an amount equal to drop across element 2. And at point 20, or 14, the voltage is somewhat inbetween, being the voltage at point 26 plus voltage drop on diode 28. Were it not for the diode 28. then the capacitor [8 would be theoretically charged from source U up to a double value. However, as soon as the voltage on the capacitor 18 increases above the nominal value, by a value which equals that ofthe voltage drop due to current flowing through diode 28, then current starts flowing through diode 28. The current flows only through the circuit constituted by line I between point 26 and 20, by line 22 between points 20 and 25 and by line 27. This means, that the current which flows through self-breaking switch element 2, drops during time interval t-, to its zero value, as shown in curve 5 thus causing the cut-off of self-breaking switch element 2 which is of such construction, that it is cut-off automatically upon zero current value. By resonance influence of the choke 4 and condenser l8, the voltage on condenser 18 could reach to double the height of the voltage U (without losses), because the choke 4 causes a continuous increase of the voltage. But as the diode 28 begins to permit current on the condenser 18 at an U,, voltage, the current will pass through a circuit formed by choke 4. resistor 3 and diode 28. Due to this the current flow stops at the switch element 2 which automatically is opened to off. Higher voltage on the condenser 18. at point 14, respectively, is caused by the characteristics of the choke 4. because the choke continuously forces the current through.  
  After cutting-off of the self-breaking switch element 2, the power which is accumulated in the magnetic core of choke 4, begins to supply current into the circuit constituted by choke 4, diode 28 and resistor 3. The current value diminishes gradually according to curve 4 until zero value is reached during the time interval t,.. The velocity or speed of the current drop depends of the time constant of the circuit which is constitued by the inductance of choke 4 and resistor 3.  
  Thereafter, by charging the capacitor 18, cutting-off the self-breaking switch element 2 and extinguishing the current in resistor 3, the whole circuit is brought into its initial state. Upon arrival of a further pulse into switch element 6, the whole action is repeated. As seen above the present invention provides three integrated circuits, ie a first circuit means for quick current increase (U elements 2,3,4 and 18), a second means for maintaining and holding a constant current (U elements 24, 23 and I8) and a third circuit means for a rapid current drop (path through elements 6.5.18). The circuit for quick current increase is charged by a special circuit, the voltage magnitude within this first circuit is kept by a special circuit. These three circuits are independent and ensure a steep current rise to a maximum value, level current keeping and swift dropping.  
  An advantageous result according to the present invention is that the separate elements of the circuit for pulse operation of electromagnet can be chosen in such a manner as to make possible a substantial shortening of time intervals for rise and drop of current in winding of electromagnet 5, and a substantial acceleration of the regeneration of electric values on the separate elements of the electric circuit. This permits the bringing of the circuit to its initial state during the time interval of release of electromagnet 5 upon simultaneous reduction of the power losses.  
  A further advantage consists in that the separate time intervals within the period of activity of electromagnet 5 can be adjusted independently of each other. Particularly, it is possible to omit the time interval during which steady current flows through the winding of electromagnet 5, and thus the time interval of current rise can be followed immediately by the time interval of current droppage in the winding of electromagnet S.  
  The foregoing is illustrative of the present invention, and various modifications and changes will be apparent to those skilled in the appropriate arts. Consequently,  
 the description is not to be taken as limiting of the scope of the invention.  
 What is claimed:  
  1. Apparatus for regulating the operation of the electromagnetic means for selecting the knitting instrumentalities of a circular knitting machine comprising a source of D.C. current for said electromagnet having a winding and a core, a pulse actuated switch interposed between said source and said electromagnet, and control means for regulating the flow of current through the winding of said electromagnet comprising an integrated circuit for causing a rapid current rise in the winding of said electromagnet on actuation of said switch by a pulse comprising a resonant circuit consisting of the resistance of the winding of the electromagnet, the inductance of the electromagnet and the capacitance of a first capacitor connected therewith, said pulse actuated switch element being connected in parallel across said electromagnet and said first capacitor means for thereafter maintaining on deactivation of said switch a constant current on said winding for a predetermined interval comprising a second D.C. current supply, an adjustable resistor. and a separating diode serially connected therewith, said second D.C. current supply, said adjustable resistor and said separating diode being connected in parallel across said resonant circuit between a point between said electromagnet and said pulse actuated switch and a point between said first switch element and said first capacitor and means for rapidly dropping the current in said winding on the expiration of said predetermined interval.  
  2. The apparatus according to claim I wherein said integrated circuit for rapidly raising the current in said electromagnet includes a diode and a second capacitor connected in parallel across the resonant circuit, between a point between the switch element and the electromagnet, and at a point between the first capacitor and the switch element.  
  3. The apparatus according to claim 2 including means for charging said first capacitor, comprising said D.C. supply source, a serially connected second switch element, a second resistor and a choke connected in parallel across the resonant circuit and simultaneously across the circuit for maintaining the constant current, between a point between the electromagnet and the first capacitor, and a point between the first switch element and the first capacitor.  
  4. The apparatus according to claim 3 wherein said second switch element is automatically self-breaking on the application of zero current thereto.  
  5. The apparatus according to claim 4 including a diode connected across said second resistor and said choke, between a point between said second resistor and said second switch element, and at a point between said separating diode and the parallel connection between said choke and said electromagnet.  
  6. The apparatus according to claim 5 wherein the integrated circuit for causing the rapid drop in current and the integrated circuit for charging said first capacitor are interconnected between the positive pole of the first D.C. current supply and the second switch element, said point being situated between the diode and the second capacitor.  
  7. The apparatus according to claim 6 including a third resistor connected across said electromagnet at a point between the separating diode and said second capacitor and a point between said electromagnet and said choke.  
  8. The apparatus according to claim 6 wherein said first D.C. voltage is greater then said second D.C. volt-