y 2, 1968 T. w. ROGERSON ET AL 3,390,751
DRIVING ARRANGEMENT FOR KNITTING MACHINES OR THE LIKE Original Filed Nov. 20. 1962 4 Sheets-Sheet 1 INVENTORS. 76 0/ 143 It. P0673504 6166410 I. .filViiAf) ZOE/my July 2,1968
T. w. ROGERSON ET l.
4 Sheets-Sheet f2 Original Filed Nov. 20, 1962 T: r mm m \& M m jQ Q H v QQ wmQ July 2, 1968 T. w. ROGERSON ET AL 3,390,751
DRIVING ARRANGEMENT FOR KNITTING MACHINES OR THE LIKE Original Filed Nov. 20. 1962 4 Sheets-Sheet 3 73k b V /77 /75 VII/I'm J 52" M a: li
INVENTORj. mama mwazesw/ 4:24.42 1 swam? if/a/my- United States Patent "ice 3,390,751 DRIVING ARRANGEMENT FOR KNI'ITING MACHINES OR THE LIKE Thomas W. Rogerson and Gerald A. Sweeney, Harwinton, Conn., assignors to General Time Corporation, New York, N.Y., a corporation of Delaware Original application Nov. 20, 1962, Ser. No. 238,968. Divided and this application Mar. 22, 1965, Ser. No.
- 14 Claims. (Cl. 192- 150) The present invention relates to an electric drive and more particularly to an automatic electrical driving arrangement for a knitting machine or the like. This is a division of our copending application, Ser. No. 238,968, filed Nov. 20, 1962, and assigned to the assignee of the copending application.
It has been common practice in the knitting industry to employ variable speed motors having relatively complex control arrangements in order to vary the speedsetting to accommodate the machine to different kinds and weights of yarns and to different modes of operation as required during the knitting of the different parts of a stocking. Accurate speed control is necessary to insure maximum output of the machine while, nevertheless, preventing damage to the needles, sinkers and other related parts of the machine. It is particularly desirable that the machine be halted just as promptly as possible following breakage of the yarn or breakage of a thread or other fragile knitting element in order to prevent snowballing of the damage to other parts of the machine and to minimize down time. Prior driving end control arrangements for knitting machines have been unsatisfactory for a number of reasons since they have been heavy and complex, since they have not been fail safe uzpon cessation of control current, since they have suffered from the effect of inertia and, where plugging or similar techniques have been used to control inertia, they have required the making and breaking of large amounts of electric current.
It is an object of the present invention to provide a knitting machine drive which is capable of extremely rapid response to a control signal, and which is substantially free of the inertia whcih characterizes drives of conventional type.
It is another object of the present invention to provide a driving arrangement for a knitting machine or the like which is particularly useful where a large number of machines are operated at the same location. In this connection, it is an object to provide a driving arrangement for the knitting machine which permits all of the machines to be driven from the same power source usually by means of a line shaft but which, neverthless, permits the speed at the input of each of the machines to be independently adjustable and automatically maintained in spite of wide variations in the speed of the power source. It is a related object to provide a driving arrangement for a plurality of knitting machines in the same room but in whichthe total amount of dissipated heat is substantially less than that where individually controlled driving motors are use on the machines.
It is still another object to provide a drive for knitting machines or the like which enables the driving speed to be maintained with a high degree of accuracy but which, nevertheless, is independent of the type of driving motor which may be used, thereby enabling motors to be employed which are common to the particular area, regardless of voltage, whether A-C or DC, and regardless of whether the motor has good or poor speed regulation. Thus, it is an object to provide a knitting machine having a built-in coupling mechanism and control circuit but which may be universally used in any part of the world.
It is yet another object related to the foregoing to pro- 3,390,751 Patented July 2, 1968 vide a drive for a knitting machine or the like which is extremely simple, consisting of only two rotating parts under the control of a simple control circuit readily serviced and maintained by local technicians having only a limited amount of knowledge and ability in electronic control techniques. Moreover, the entire control circuit or subassem'blies thereof may be fabricated in the form of compact plug-in units so that a new unit may be substituted promptly for a defective one and with the actual servicing being taken care of at a central service center. It is a related object to provide a driving and control arrangement for a knitting machine or the like which isnot only simple but which is capable of operating without maintenance for long periods of time, avoiding the common sources of trouble including commutators, slip rings, relay or contactors, all of which are subject to the effects of dirt and wear within a relatively short period of time.
It is still another object of the present invention to provide a variable speed electric drive having speed regulation which is as good and in many cases superior to that of conventiional motor drives and which is, in addition, lower in initial cost, particularly in the integral horsepower range.
It is an object of the invention, in one of its aspects, to provide a novel and effective oil clutch in which a film of oil is maintained between input and output discs together with means for changing the thickness of the film correctively to maintain a predetermined but adjustable output speed.
It is another object of the invention, in one of its aspects, to provide a drive which utilizes intentional slipage but in which the energy lost in the slippage is constantly and efficiently dissipated so that the device may be operated for long periods of time, where necessary, at high slippage rates, without noticeable wear and without buildup of excessive temperatures.
It is finally an object to provide a clutch control circuit employing transistors which avoids the effects of high reverse voltage and current leakage, particularly where the device is employed in spaces having a high ambient temperature. As one of the features of the control, the power output element may be locked in to the power input element so that there is no loss of power through the drive. 4
Other objects and advantages of the invention will become apparent upon reading the attached detailed description and upon reference to the drawings in which:
FIGURE 1 shows a portion of a knitting machine including a driving arrangement constructed according to the teachings of the present invention;
FIG. 2 is a view taken along the line 2-2 in FIG. 1 showing the end of the oil clutch;
FIG. 3 is a longitudinal section through the clutch taken along the line 33 in FIG. 2;
FIG. 4 is a fragmentary section showing the path of flow of magnetic flux;
FIG. 5 is a face view of the armature or output disc looking along the line 5-5 in FIG. 3;-
-FIG. 6 is a fragmentary section showing the cross section of an oil groove looking along the line 6--6 in FIG.
FIG. 9 is a schematic circuit diagram showing the means for controlling the clutch output speed.
While the invention has been discussed in connection with a preferred embodiment, it will be understood that we do not intend to be limited to the embodiment shown but intend, on the contrary, to cover the various alternative and equivalent constructions included Within the spirit and scope of the appended claims.
Turning now to FIGURE 1, there is disclosed at a portion of a knitting machine incorporating a drive mechanism in accordance with the present invention. A machine of this type is disclosed in Larkin Patent 2,422,568, issued June 17, 1947 and to which cross reference is made. In the knitting machine of Patent 2,422,568 means are provided for regulating the speed of the machine during each of the successive operations required in forming the knitted product. Speed variations are obtained through the medium of electronic control devices acting upon the electric motor which serves as the power source for the machinery, particularly a potentiometer actuated directly from the pattern drum of the machine.
The cam ring 2 of the knitting machine, in the present instance, is held stationary and is rigidly secured to the top frame of the knitting machine. The knitting or needle cylinder 3 is of the rotary type and is adapted to rotate about a vertical axis within the cam ring 2. The sinker ring mechanism is illustrated generally at 4. The needle cylinder 3 is provided with an integral bevel gear 5 which meshes with and is rotated by a bevel gear 6, which latter is fixedly mounted for rotation with the horizontal shaft 7. The shaft 7 is rotatably mounted in suitable bearings in opposite side frame members (not shown). Loosely mounted for rotation about the axis of the shaft 7, is a gear 12 which meshes with a spur gear 13 which is rotatably mounted on a fixed stub shaft 14. The gear 13, in turn, meshes with a pinion 15 which is fixed to a jack shaft 16 suitably journaled in the machine. Secured to the jack shaft 16 is a second spur gear '19 which meshes with a spur gear 20. The spur gear 20 is secured to a take-off shaft 21. Mounted on the take-off shaft 21 is a bevel gear 22 which meshes with a bevel pinion 23. The latter is secured to the output shaft 26 of a variable speed coupling 25 constructed in accordance with the present invention having an input shaft 24.
It will be apparent that that the gear train as thus far described, and the needle cylinder 3, rotate at a relatively slow rate of speed which depends upon the gear ratio. However, as described in detail in the above patent, provision is also made for oscillating the gear 5 as an alternative to continuous driving. For this purpose the gear 13 carries a crank pin 26 to which is secured one end 27 of a pitman 28, the opposite end 29 of the pitman carrying a pin 30 which engages one arm 31 of a gear segment lever 32. The lever 32 is mounted for oscillatory movement on a shaft 33. At the left hand end of the lever 32 a gear segment 34 is provided which engages a gear similar to the gear 12 on shaft 7, but which is not visible in the drawing. It will suflice to say that for selecting between the two conditions of continuous and oscillatory movement, a shift mechanism is provided operated by a shifting fork. Thus, there is provided a sleeve 37 which carries a key 36 which is slidable in a slot formed in the gear 6. The sleeve 37 has a peripheral groove 38 which is engaged by a shifting fork 39 having a shifting lever 40. Thus, when the gear 12 is coupled to the hub of the gear 6, the needle cylinder 3 rotates continuously but when the companion gear is coupled to the hub, the rocking movement of the gear sector 34 causes the needle cylinder to oscillate back and forth. Selection of the two modes of operation is brought about by cam plates secured to the peripheral surface of a pattern drum mounted on a shaft 51, which is rotatably mounted in the framework of the machine. Secured to the shaft is a ratchet wheel 52. For advancing the ratchet wheel a pawl 53 is provided mounted upon a lever 54 which is secured to the oscillating shaft 33.
Means are, however, provided for disabling the pawl 53, lifting it clear of the ratchet wheel 52 so that the pattern drum does not rotate continuously but is advanced only in accordance with a predetermined program. Thus, there is provided a kick-out arm or latch 55 which is pivotally 4 mounted on the frame of the machine and which operates against a pin 56 which projects laterally from the pawl 53. The position of the latch 55 is controlled by the links of a pattern chain which is constantly driven at a slow rate of speed. Referring tothe drawing, it will suffice to say that a sprocket or chain wheel 57 is provided which is directly connected to a second ratchet wheel 59 which is engaged by a pawl 60 oscillated by a lever 32. Trained about the sprocket wheel 57 is a pattern chain having cams 66 secured at predetermined points along its length. These cams are in the path of movement of an arm 58, forming a part of the latch 55 which controls the action of a pawl 53.
Thus, as the lever 32 rocks back and forth, reciprocation of the pawl 60 causes rotation of the ratchet Wheel 59, accompanied by movement of the pattern chain 65. Whenever one of the earns 66 engages the arm 58, of latch 55, the pawl '53 is lowered into working engagement with the ratchet wheel 52, thus stepping the pattern drum 50 forwardly in accordance with a predetermined pattern of movement.
It may, incidentally, be noted that means operated by the pattern drum are provided for .changing the yarn. This is accomplished by yarn change fingers 62 which engage lift levers 63 pivotally mounted on a cross shaft 64. The shaft 64 carries a cam follower 64a which rides on cams 67 formed on the periphery of the pattern drum.
In the above patent a potentiometer was provided in the machine having a rotor and stator which were separately adjustable by cam members in the machine. However, in accordance with one of the aspects of the present invention, separate manually settable reference elements are provided in the control circuit for establishing predetermined speeds and program cams or the like are provided on the pattern chain 65 and pattern drum 50 for operating limit switches for switching between the reference elements. Thus, associated with the cam follower 64a, which rides on the drum 50, there is provided a limit switch 78 having contacts 78a, 78b. Similarly, associated with the arm 58, which rides on the chain, there is provided a second switch 79, having contacts 79a, 79b. The manner in which all of these contacts are employed to effect a change in the driving speed will be apparent when considering the control circuit covered in a subsequent paragraph. For the present it will suflice to say that the pattern chain and pattern drum together serve to switch the driving mechanism thereby to change the operating speed of the machine. Directing attention next to the upper portion of FIG. 1, means are provided for feeding strands of yarn into the machine and for detecting breakage of any of the strands. In the present instance, three strands indicated at 91, 92, 93 are fed from bobbins 91a, 92a, 93a. Associated with the strands are switches 94, 95, 96 which are connected to disabling lines 97, 98, and which are so constructed that when breakage occurs the switch contacts close, thereby to produce a short circuit across the lines 97, 98. Such short circuiting is utilized to bring about immediate disabling of the drive mechanism and stoppage of the machine so that damage to the machine is minimized.
At the lower right of FIG. 1 is disclosed a blower for producing an air blast to a stocking ejector apparatus (not shown). As is well known to those skilled in the knitting art, the purpose of such apparatus is for pneumatically ejecting a finished product.
Up to the present time, and to the best of our knowledge, machines of the type disclosed herein utilized a separate motor for product ejecting purposes other than the motor used for the variable speed drive. Furthermore, it is also well known that it is desirable to have the blower operating motor developing a constant speed in order to maintain a constant eject force within the blower. Thus, it can be appreciated that the variable speed drive motor was unsuitable for such application as any alteration of its speed altered theeject conditions within the blower.
By the example arrangement of the variable speed drive of the instant invention (FIG. 1) only a single constant speed drive motor is required whereby a variable speed and eject function isefficiently' obtained. Moreover, the drive motor benefits from the cooling effect given off by theblower unit due to 'itsconvenient location adjacent thereto. Thus, the single drive motor serves a dual function which results in a reduction of overall-expense and affords sought after compactness; I
Turning attention next to the construction of the coupling 25which is set forth in longitudinal section in'FIG. 3, it will be noted that it includes a housing 100',-having a cup-shaped portion 101 and an end bell 102, the two sections being clamped together by machine screws 103 engaging mated flanges 104, 105, respectivelyrExtending from the left-hand end of the machine is the input shaft 24 and extending from the right-hand end of the machine, and alined therewith, is the output shaft 26. The input shaft is journaled in spaced bearings 111, 112 so as to' be capable ofsupporting an overhanging load. In the present instance the bearings are mounted in a sleeve 113 and are spaced apart by a spacer 114 which engages the inner races. For the purpose of preventing escape of lubricant along the shaft, an oil seal 115 is provided which may be of any suitable type, commercially available. Similarly, the output shaft 26 is supported on bearings 121, 122 mounted in a sleeve 123 and separated by a spacer 124, sealing being taken care of by a seal 125. The housing is intended to be operated approximately half full of oil orother viscous fluid capable of eflicient lubrication and cooling. An O-ring 126 is Preferably interposed between the portions 101, 102 of the housing to provide an effective seal.
In carrying out the present invention, a driving disc or rotor is secured to the input shaft and a driven disc, or armature, is secured to the output shaft, with means for setting up a variable magnetic flux between them, thereby to regulate the output torque and speed. Turning attention first to the rotor, which has been indicated at 130, it includes a hub 131 mounting a disc portion 132, the hub being secured to the shaft by a key 133 and locked against endwise movement by any suitable means, preferably snap rings such as the ring 134, seated in a shallow groove formed on the shaft. The disc 132 is of composite construction including coaxial sleeves 135, 136 of magnetic material spaced apart by a nonmagnetic annulus 137 to form separate annular poles 141, 142. Surrounding the sleeve 136 is a furthur annulus 143 to which is cemented, or otherwise secured, an annular friction member 145. V Cooperating with the rotor 130 is an armature 150 mounted on a hub 151 providing a freely slidable splined connection 152. The armature is preferably made of soft steel or other permeable magnetic material, completing the magnetic circuit between the poles 141, 142 on the rotor previously referred to.
For the purpose of establishing a flow of flux through the poles,'a stationary annular electromagnet 160 is provided having poles 161, 162 thereon which axially overlap, and have a close spacing with respect to the pole members 135, 136 on the rotor. The magnet 160 is of U cross section accommodating .an annular coil 165 to which current is conducted by leads 166, 167 leading to a connector 168 outside of the machine.
It will be apparent from FIG. 4'that the flux, indicated at F, passes from the electromagnet through the annular poles 13-5, 136for magnetic attraction of the armature which is free to move on its central spline connection 152, the amount of force being dependent upon the current flow through the winding. Preferably the friction material 145 is made flush with the outer pole 142 while the inner pole is undercut to provide a small amount of clearance 146 on the order of a few thousandths of an inch.
In accordance with one of the aspects of the present invention, sharp edged, radial grooves are formed in the face of the armature for the purpose of conducting the oil to the faces which are in engagement and to provide an escape path for the oil film as the magnetic attraction is increased with resulting increase in rotational drag. Thus, referring to FIGS. '5 and 6, radial grooves 171-176 are cut in the face of the armature spaced at equal angles. Each of the grooves defines edges 177, 178 which are preferably relatively sharp and each of the grooves is of square cross section, having an area which may be on the order of .01 square inch. It should be here pointed out, however, that similar grooves 171-176 may be formed in the friction member (instead of armature and through the outer edge of annular pole 142 to provide for the above explained oil circulation without departing from the spirit of the invention.
For the purpose of admitting the oil to the inner ends of the grooves 171-176, the magnet is so dimensioned with respect to the hub 131 as to provide an 'annu lar oil passageway 181, and openings 182 are formed in the rotor at spaced intervals (see FIGS. 3, 7 and 8). As the input shaft turns, and assuming flow of current through the electromagnet, drag torque is applied to the armature so that it too begins to turn. As will be set forth in greater detail in connection with the control circuit, the current through the coil under starting conditions is high and the attractive force on the armature is correspondingly great so that the film tends to be squeezed out from between the engaging surfaces resulting in a high value of transmitted torque and with immediate acceleration of the output shaft to a speed approaching the desired value. Simultaneously, the centrifugal force, acting upon the oil in the armature grooves, causes oil to be discharged radially outward along the path P shown in FIGS. 5 and 8. Because the grooves are in multiple, having substantial total area, a large volume of fluid is conducted. For example, in the case of a practical coupling having a rating of /2 H.P., the rate of flow may be on the order of approximately 50 cubic inches per minute when rotating at 1800 r.p.m. It is to be noted that, while the oil conducting grooves are formed in the output disc rather than the input disc, the output disc is immediately effective on startup and has the advantage of rotating thereafter at a maintained speed. The clearance at the pole face 141 augments the grooves in providing replenishment of the fluid to the space 138 (FIG. 8).
Conversely, when prompt shutoff is required the current in the coil is immediately dropped to zero by the control circuit to be described, thereby releasing the magnetic attractive force upon the armature. To insure prompt separation, the armature preferably carries a set of three separator springs 183 having separator buttons 184 which engage the rotor face (see FIG. 5). One of the spring assemblies is shown in FIG. 4, wherein a rivet passes through a hole at the lower portion of spring 183 and is pressed into a hole provided in the armature 150. The button 184 loosely fits in a second hole provided at the upper portion of armature 150. Button 184 is fixed to the upper portion of spring 183. With the coil 165 in energized condition, button 184 is drawn toward the friction member 145 (as shown) thereupon tending to straighten spring 183. Such action causes a pressure build-up at the rear of button 184. Upon deenergization of coil 165, the magnetic attractive force is released, whereupon springs 183 apply their stored energy at the rear of buttons 184 and positively disengage the armature 150 from the friction member 145. Thus, it can be appreciated that immediate separation is effected and any possible adhesion condition is prevented. The pressure of the fluid in the grooves is also effective to cause the armature to move away from the rotor, greatly increasing the thickness of the film between them so that negligible torque is transmitted to the output shaft. In accordance with one of the aspects of the invention, it will be noted that the armature is axially quite thin and of low mass so that the inertia of the output element is kept to a low value. The net result is that when current is turned off the output shaft stops with little overtravel. This is to be contrasted with conventional driving arrangements either in the form of motors or in the form of a clutch of the eddy type in which there is substantial inertia and hence substantial overtravelwhich must be arrested by plugging or similar techniques.
Our observations show that the oil in the device performs a number of ditferent functions. Not only does it lubricate the interface between rotor and armature to prevent wear but it also serves to provide a frictional drag torque which varies more or less inversely with respect to the film thickness. The arrangement is such that a thin film is available on starting for maximum accelerating or break-away torque and a thick film is established promptly upon stopping to provide prompt torque cutoff. In addition, the relatively large amount of fluid which is pumped by the centrifugal force serves efficiently to carry away the energy of slippage in the form of heat which is conducted to the housing of the device. Thus, notwithstanding the fact that the clutch is only half filled with oil, the entire inner surface of the housing is thermally coupled to the oil by scrubbing action.
Means are provided at the outside of the housing for carrying away this conducted heat. In the present instance the portions 101, 102 of the housing have integrally molded fins 101a, 102a which are in register with one another providing longitudinal air channels having a large total surface area over which air is forced by a fan, indicated at 185, secured to the input shaft. For safetys sake, the end member 102 may be provided with a cup-shaped shield which fits over the fan so as to protect against contact with the whirling blades or, if desired, a shield may be provided which is sufficiently deep so as to enclose not only the fan but also an input drive pulley which may be secured to the shaft adjacent the fan and in absence of a separate driving motor.
For the purpose of venting the housing to prevent the build up of pressure therein as the fluid is brought up to operating temperature, a breather plug 186 is provided above the oil level having a breather opening 187 and which is protected against loss of fluid by an internal shield or bathe 188.
In accordance with one of the aspects of the present invention, for the purpose of monitoring and automatically controlling the output speed, a tachometer is provided within the housing adjacent the armature disc 150. The tachometer, indicated at 190, includes a stator 191 and rotor 192. The stator is clamped in place within the structure by a retaining ring 193, while the rotor is keyed to the shaft on a key 194. The tachometer is of thhe commutatorless type producing an output voltage and frequency which varies directly with speed. Briefly stated, the stator 191 includes a toroidal coil between annular core pieces having fingers bent inwardly and interspersed with one another to define a plurality of stator poles. The rotor is permanently magnetized with pairs of poles integrally related to the fingers on the stator. Thus, when the rotor is in a reference position flux is caused to flow through the coil in one direction and when the rotor is advanced through an incremental distance, flux is caused to flow through the coil in the opposite direction, thereby gen erating an A-C wave. Integrating the tachometer into the construction makes it unnecessary to provide a separate housing and outboard mounting for the tachometer, reducing the cost to a fraction of that formerly necessary. In addition, the tachometer is protected and both the control leads and tachometer leads which lead to the control unit may be run through the connector 168, simplifying the installation.
- In accordance with the invention improved means are provided for automatic maintenance of the output speed in spite of wide variations in the speed of the input shaft.
More'specifically, the current from the tachometer generator is bucked against an adjustable source of reference current to produce a net input current to a'transistor amplifier having the clutch coil in its output circuit so that a corrective change is made in the clutch current when there is any tendency for the speed to change. Thus, upon a slight drop in the output" of the tachometer, current through the clutch coil is increased and any slight excess in output of the tachometer causes the clutch current to decrease with the result that the output speed is maintained constant within close limits.
Turning to the control circuit as set forth in FIG. 9, attention may be directed first to. the power supply set forth in the top portion of the diagram. Assuming that the motor M is supplied with .three phase current via linesv L1, L2 and L3, voltage is taken from two of the lines, passed through a step downtransformer 200 into a bridge rectifier 201, having output terminals 202, 203 of the polarity indicated. The output voltage is filtered by a capacitor 204. The voltage is maintained constant by a Zener'205 having a series resistor 206.
For producing a selectable reference voltage, a reference voltage source 210 is provided as shown at the foot of the diagram. Alternating current is conveniently obtained from a winding 211 which may be wound on the transformer 200. The output is rectified by a diode 212 and filtered by a capacitor 213. To enable selection of reference voltage, a plurality of potentiometers are provided, in the present instance a first potentiometer 215 having an output terminal 216 and a second potentiometer 217, having an output terminal 218.
To turn the power on and off a relay 220 is provided having a start switch 221, a stop switch 222, and contacts 223, 224. Pressing the start switch energizes the relay, with contacts 223 sealing in to maintain the relay closed. To turn off the circuit, momentary pressing of the stop button drops out the relay.
In order to make the reference voltage independent of fluctuations in line voltage, a Zener voltage regulator is provided including a Zener diode 225 and series resistor 226 connected as shown.
Means are provided for converting the output of the tachometer to A-C feedback voltage for bucking against the selected reference voltage. For this purpose the tachometer generator is connected to a bridge rectifier 230, the output of which is filtered by capacitor 231. Both legs of the circuit are provided with a series or droop resistor for limiting the current flow. Thus, in series with the tachometer generator circuit, the feed back current is limited by a resistor 232 having a rheostat 233 connected in series therewith for adjustment of maximum speed. In parallel with the resistor 232 is a capacitor 234 to stabilize the circuit, particularly in the face of sudden changes in output of the tachometer generator. In the reference leg of the circuit, a resistor 235 is provided in series with the switch terminal. It will be seen, then, that the tachometer circuit and reference circuit, each with a series resistance, are in parallel with the input terminal 236 of the amplifier stage.
For the purpose of responding to the differential current and for producing an amplified signal which is applied to the clutch coil, an amplifier 240 is provided having direct coupled transistors 241, 242. The emitter of the first transistor has a resistor 243 and-is directly connected to the base of the second. Both emitters are supplied from the positive terminal 202 of the power supply and the collectors are jumpered together and returned to the negative terminal 203 of the power supply with the clutch coil 165 in series therewith. A diode 244, polarized as shown, is connected across the base-emitter, or input, circuit of the first transistor to protect the latter against reverse overvoltage.
To insure that the output current'may be reduced to zero upon shut off, particularly under high ambient tem perature conditions, means are provided for applying a small amount of positive bias to the base of the second transistor. This is accomplished by employing a constant voltage drop diode 245 or stabistor in the emitter circuit of the transistor 242 with the circuit being completed through a series resistor 246. Upon flow of current from the power supply through diode 245 and resistor 246 a constant voltage drop occurs through the diode, making the base slightly positive with respect to the emitter.
Finally, to prevent the transistors from being injured by the inductive kick from the clutch coil 165 when the latter is deenerg-ized, the coil is short-circuited bya diode While the operation of the circuit described above will be apparent to one skilled in the art, it may be described briefly as follows. It will be assumed that the clutch input I shaft is being turned at a certain-nominal speed by the motor, that a load is connected to the output shaft, that the first potentiometer 215 is in the active position, and that sufficient current is flowing through the clutch coil so that a predetermined output speed is obtained. In the event that the output load drops slightly resulting in a tendency for the output speed to increase, the net input current applied to the base of the first transistor decreases slightly, thereby decreasing its current output which is fed to the emitter and base of the transistor 242 whereupon the output of transistor 242 is decreased. Then the load current of the two transistors which flows through the clutch coil 165 tends to decrease slightly, reducing the drag torque so that there is a corrective, slight increase in speed of the output shaft and restoring a condition of equilibrium. A corrective change in the same direction takes place upon any tendency for the speed of the input shaft to increase, for example, as a result of a sudden increase in line voltage.
The converse takes place when there is a decrease in the output speed from the desired equilibrium value due to added loading or a drop in the line voltage supplying the motor. Under such conditions the resulting unbalance between the tachometer circuit and reference circuit causes a slight increase in the current flowing through the base circuit of the transistor 241, increasing the emitter current and thereby slightly increasing its current output which is fed into the emitter and base of the transistor 242 whereupon the output of transistor 242 is increased. Then the load current of the two transistors which flows through the clutch coil 165 tends to increase slightly, increasing the drag torque so that there is a corrective, slight decrease in the speed of the output shaft that restores a condition of equilibrium.
It is one of the characteristics of conventional transistors, particularly where of the germanium type, andparticularly under high temperature conditions, that the transistor output circuit is conductive even where the input current is zero. The presence of the stabistor 245 in the circuit insures that under zero input conditions there will be sufficient positive bias on the base with respect to the emitter so that the current through the clutch coil will be substantially zero. r 1
By using the above described combination of clutch and control circuit, the speed regulation may be held to within approximately 2% or better in spite of variations in input speed over a wide range. i 1
In accordance with one of the aspects of the present invention, a novel contact arrangement is employed including both normally open and normally closed contacts in the switches 78, 79 to permit switching between the potentiometers 215, 217 directly without use of an interposed relay. Thus, we provide in switch 78 normal-1y closed contacts 78a and normally open contacts 78b, and we also provide, in switch 79, normally open contacts 79a and normally closed contacts 79b. Contacts 78a, 79a are arranged in parallel with one another and connected in series with the output terminal 216 of potentiometer 215. The remaining contacts 78b, 79b are connected in series with one another and in series with output terminal 218 of potentiometer 217. As a result, potentiometer 217 is connected in the circuit only when switch 78 is actuated and when switch 79 is in its normal, or nonactuated position. Under such conditions it will be apparent that contacts 78b are closed so that a circuit is completed to potentiometer 217 through the normally closed contacts 79b, whereas the contacts associated with the potentiometer 215 are both open circuited.
- Referring briefly to the other possible conditions, it will be apparent that when neither switch is actuated, potentiometer 215 is in the circuit via normally closed contacts 78a. When only switch 79 is actuated, potentiometer 215 is again in the circuit since the closure of contacts 79a and opening of contacts 79b is simply redundant. Finally, it will be apparent that when both switches 78 and 79 are actuated the circuit to potentiometer 215 is set up through closure of contacts 79a, with the circuit to the poteniometer 217 being opened by opening of contacts 79b. In short, the contacts in the two switches are connected to perform a logic function, with the potentiometer 217 being connected in the circuit only during one of the four possible switch conditions.
The ability of the device to maintain the speed constant at an adjusted value is particularly important in a knitting machine where operation at maximum efficiency requires a certain operating speed for certain operating parameters, notably the type and gauge of the yarn being used. The drive is well suited for use in those areas where wide swings in line voltage are encountered or where wide changes in input speed may occur, as where water power is being utilized as the power source. To take a practical case it may be assumed that the desired output speed is 1800 rpm. and that the available speed at the input shaft is a nominal 2200 rpm, with substantial variation possible below this value. Using the present control arrangement the speed of the input shaft would have to drop more than 18% to below 1800 r.p.m., be fore there would be any reduction in output speed below the setvalue. Consequently, knitting machines employing the present invention may be sent to any country of the world independently of the kind of power available with assured efiiciency of the operation of the machine, provided only that the input speed does not fall below a stated minimum.
The clutch and control circuit, comprising a. system,
have a short time constant, i.e., are capable of responding immediately to changes in the operating conditions. Thus, upon breaking the yarn in the knitting machine, causing momentary short circuiting of the relay coil, the resulting drop-out removes power from the clutch with practically no overtravel due to inertial effects and without necessity for resorting to plugging. The circuit may be readily inched or jogged by holding the start button down and releasing the stop button in short pulses.
Control over the entire speed range is achieved using low values of control current so that conventional and inexpensive circuit components may be used, permitting compact unit, or plug in, construction. Because of the small amount of current drawn by the control system, the voltage across the power supply output terminals 202, 203 may be regulated by the low cost Zener diode 205 and series resistor 206 which are optional.
The amount of heat dissipated by the control circuit is negligible. Moreover, where operating conditions are such that a constant high degree of slippage in the variable drive unit must be employed, resulting in a high rate of energy transferred to the cooling fluid, the cooling air may be vented from the work space or a heat exchanger may be used for recirculating the cooling fluid and for maintaining it at a relatively low temperature.
The control system is so simple as to enable servicing by relative untrained personnel, particularly where plug in units permit simple substitution of the circuit or subassembly.
While the mechanism whereby torque is transmitted through the oil film is a matter for continued investigation, it would appear that a thin film of moderately viscous oil or the like, because of internal friction between the oil molecules, tends to resist shearing force. Thus, when the rotor rotates with respect to the armature at a certain slip speed and where the film is only a few molecules thick, it will be apparent that there must be a high speed of slip between adjacent molecules which is accompanied by a high reactive force, i.e., a high torque. However, where the rotor and armature are more widely spaced with a thick film between them, the same relative speed of slip between the discs is accompanied by a relatively low speed of slip between adjacent molecules. Hence the reactive force, or torque, is reduced. In short, when the current to the coil 165 is reduced, oil from the grooves 171-176 feeds bet-ween the disc faces to reduce the transmitted torque.
Wear is negligible in the instant variable drive construction due to the opposed surfaces being at all times during operation swept and cooled by oil. It has been experienced over extended periods of operation that the sleeve 136, which is flush with the friction material, and the armature face tend to wear a trivial amount. However, such wear has no influence n the engaging surfaces and the desired torque characteristics remain constant when varying loads are applied over extremely long periods of operation.
It is one of the features of the present drive system that it is fail safe in operation. Thus, the driving torque is not only instantly terminated as a result of thread breakage, or the breakage of any other element in the machine causing thread breakage, but the drive is turned off as a result of failure of control current, the effects of which are simply to cut off current flow in the transistors which supply current to the clutch coil 165. Thus, the system is to be contrasted with systems in which decleration or cut-off requires control current in the form of brake or plugging current.
It is to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention, which, as a matter of language, might be said to fall therebetween.
Having described our invention, what we claim as new and desire to secure by Letters Patent is:
1. In a drive system for a knitting machine or the like, the combination comprising a source of rotative power rotating at a speed which is at least as great as the maximum speed required by the machine, a variable speed drive coupling interposed between the power source and the machine, said drive coupling having a housing including alined input and output shafts carrying input and output discs, said discs being made of magnetic material, means including a coil for varying the magnetic attraction between the discs thereby varying the slip which occurs between the faces of the discs, a tachometer on said output shaft for producing a Speed signal, means for producing an adjustable reference signal, an amplifier having its input connected for response to the net value of the signals and having said electromagnet in its output circuit for correctively varying the current through the magnet thereby to maintain a constant but adjustable output speed, said housing having a charge of oil therein, means for feeding oil between the faces of the discs, at least one of said discs having oil conducting ports extending radially therein for pumping oil through said disc by centrifugal force and into heat transferring contact with the inside wall of the housing, thereby to maintain the discs at a relatively low operating temperature during continued operation at high percentage of slip.
2. In a driving arrangement for a knitting machine or the like, the combination comprising a, source of rotative power having a speed at least as high as the maximum speed required by the machine, a variable speed drive coupling interposed between the source and the machine,
said variable speed drive coupling having a housing and output shafts arranged coaxially therein surrounded by a cooling surface, adjacent input and output clutch discs at the opposed ends of said shafts, one of said discs having a pair of annular pole pieces and the other disc being made of magnetic material, a stationary electromagnet cooperating with said annular pole pieces and having a coil therein for varying the magnetism, at least one of said discs being mounted for limited endwise movement on its shaft so that variation in the current through the coil produces variation in the slip of the output disc relative to the input disc, a tachometer coupled to said output shaft for generating a speed signal, means for generating an adjustable reference signal, an amplifier responsive to the net value of said signals and having the clutch coil at the output thereof for correctively varying the current in the coil upon departure of the speed of the output shaft from a set value, at least one of said discs having a set of radial grooves formed on the face thereof, means for feeding oil to the inner ends of the grooves so that upon rotation in said coupling the oil is pumped through the grooves by centrifugal force for supplying of oil between the faces of the discs followed by flowing of the oil against the cooling surface for operation at low temperature during extended periods of high slip.
3. In a drive coupling for use with a knitting machine or the like for driving the same from a power source having a speed which is at least as high as the maximum speed required by the machine, the combination comprising, a housing, input and output shafts journaled in said housing and arranged end to end, input and output clutch discs arranged on the ends of the shafts, said input clutch disc having a pair of annular magnetic pole pieces and said output disc being made of magnetic material for cooperating with said pole pieces, an annular electromagnet mounted in said housing in a stationary position having poles for cooperating with the annular pole pieces on the input disc, a tachometer including a permanently magnetized rotor onsaid output shaft and a stationarily mounted stator secured inside said housing telescoped over said rotor for cooperating therewith, said housing having a charge of oil contained therein, and means including radial grooves formed in the face of at least one of said discs for pumping oil by centrifugal force for cooling of said discs and for the supplying of oil to the engaged surfaces thereof.
4. In a drive coupling for use with a knitting machine or the like and capable of being powered by a source of rotative power operating at a speed at least as high as the maximum speed required by the machine, the combination comprising a housing, input and output shafts journaled end to end in said housing, input and output discs secured to the opposed ends of the shafts, said input disc being of composite construction including inner and outer concentric annular pole pieces separated by a nonmagnetic annular stator, a flange on the outer annular pole piece, an annulus of friction material mounted on said flange, the friction material being flush with the outer annular pole piece for engaging output disc, the inner annular pole piece being foreshortened to provide clearance with respect to the output disc, means including an annular electromagnet having poles cooperating with the nner and outer annular pole pieces, said housing includmg a charge of oil, said output disc having radial grooves on the face thereof, said grooves being of generally square cross-section and having relatively sharp edges, means for feeding oil to the inner ends of said radial grooves so that upon rotation of the output shaft a fluid is pumped by centrifugal action through said grooves for cooling said discs and for providing a film of oil between them the thickness of which is determined by the current flowing through said electromagnet thereby to vary the speed of the output shaft.
5. A variable speed coupling for a knitting machine or the like for powering from a rotating power source having a speed which is at least as high as the maximum speed required in the machine, the combination comprising a housing, input and output shafts journaled end to end in said housing, input and output discs of magnetic material connected to the ends of the shafts respectively with at least one of said discs having provision for limited axial movement, the input disc including a pair of annular pole members concentrically arranged thereon and having an annular friction member adjacent the pole members, means including an annular electromagnet for applying fiuxto said pole pieces for varying theattraction between said discs, means defining radial grooves of generally square cross-section and having relatively sharp edges formed in the face of the output disc, said housing having a charge of oil therein, said annular electromagnet defining with said shaft an annular oil conductings-pa-ce leading to the inner edge of the input disc, the inner edgeof the input disc having apertures formed therein for conducting said oil to the inner ends of the grooves formed in the output disc so that upon rotationv of said disc oil is drawn into said grooves and expelled therefrom by centrifugal force for replenishment of an oil film between said discs and for maintaining the discs at a safe operating temperature.
6. In a variable speed coupling for driving a knitting machine or the'like, the combination comprising a cylindrical housing having a cup-shaped body portion and an end member, input and output shafts axially arranged end to end 'in said housing, one of said shafts being journaled in said cup-shaped member and the other of said shafts being journaled in said end member, said cup-shaped member and said end member having mating flanges thereon together with means for' securing the flanges together, input and. output clutch discs connected to the respective shafts, said enclosure having a charge of oil therein for forming an oil film between the discs, means including an annular electromagnet for varying the pressure exerted between the two discs thereby to vary the thickness of the oil film, at least one of said discs having radial grooves formed on the face thereof for pumping oil outwardly so that the heat of said oil is transferred to the inner wall of the cup-shaped body portion, said body portion and said end member having fins integrally formed thereon, said input shaft having a fan for moving air axially in contact with said tins for constant removal of the liberated heat.
7. In a variable speed coupling for powering a knitting machine or the like, the combination comprising a housing, input and output shafts journaled in said housing end to end, input and output discs secured to the ends of said shafts, said discs having engaging clutch faces, a charge of oil in said housing, at least one of the discs having relatively sharp edged, radial grooves of generally square cross-section in its face for conducting said oil and forming it into a film, electromagnetic means for varying the force at the clutch faces thereby to vary the film thickness, the other one of said discs having an annular liner of friction material, said grooved disc having a plurality of spring biased plugs mounted therein and bearing upon said liner so that when the electromagnet is deenergized the biasing force exerted by said plugs produces immediate separation of said discs.
8. In a drive system for a knitting machine or the like having a malfunction detector, the combination comprising a source of rotative power having a speed which is at least equal to the maximum speed required of the machine, a variable speed drive coupling interposed between the driving source and the machine, said coupling including a housing journaling input and output shafts arranged end to end, input and output discs mounted on the respective shafts for clutching them together, said discs being formed of magnetic material and having an annular electromagnet cooperating therewith for varying the attraction between the discs, said housing including a charge of oil together with means for flowing oil between the discs, a tachometer in said housing for producing a speed signal proportional to the speed of the output shaft, means for generating a reference signal, an amplifier having a pair of direct coupled transistors together with an input and output circuit, the input circuit being connected for response to the net value of the signals and the output circuit being connected to the electromagnet so that the current through the latter is correctively varied upon departure of the speed of the output shaft from the set value, said transistors having auxiliary biasing means for insuring the current in the output circuit is zero net input signal, and means for disabling flow of current through said electromagnet upon operation of the malfunction detector in the machine.
9. In a drive system for a knitting machine or the like, the combination comprising a source of driving power having a variable speed coupling interposed between the power source and the machine, said variable speed coupling including a pair of clutch discs and an associated electromagnet for varying the force between the faces of the clutch discs, at least one of said clutch discs having means defining radial grooves for conducting oil to the clutch faces, said variable speed coupling having a tachometer coupled to its output for producing an A.-C. speed signal, means for rectifying said signal to produce a D.-C. speed voltage, an amplifier having input terminals and output terminals, means including a series resistor for applying said D.-C. speed signal to the input terminals, means for producing a D.-C. reference voltage, means including a series resistor for applying said reference voltage to the input terminals so that the net current in the input circuit of the amplifier is proportional to the algebraic sum of the speed and reference voltages, the output of said amplifier being connected to said electromagnet so that upon variation in speed of the output of the coupling device the current in the electromagnet is correctively adjusted for maintenance of a predetermined speed.
10. In a drive system for a knitting machine or the like having a malfunction detector, the combination comprising a current source, a source of rotative power rotating at a speed which is at least as great as the maximum speed required by the machine, a variable speed drive coupling interposed between the power source and the machine, said drive coupling having a housing including aligned input and output shafts carrying input and output discs, said discs being made of magnetic material, means including a coil for varying the magnetic attraction between the discs thereby varying the torque exerted between the faces of the discs, a tachometer on said output shaft for producing a speed signal, means for producing an adjustable reference signal, an amplifier responsive to the net signal and having said electromagnet in its output circuit for correctively varying the current through the magnet thereby to maintain a constant output speed, said housing having a charge of oil therein, means for feeding oil between the faces of the discs, at least one of said discs having oil conducting ports extending radially therebetween for pumping oil through said discs by centrifugal force and into heat transferring contact with the inside wall of the housing thereby to maintain the discs at a relatively low operating temperature during continued operation at high percentages of slip, and means responsive to the operation of the malfunction detector for disabling flow of current through said electromagnet so that rotation of the output shaft ceases upon either a malfunction or failure of the current source.
11. In a variable speed coupling for driving a knitting machine or the like, the combination comprising a cylindrical housing having a cup-shaped body portion and an end member, input and output shafts axially arranged end to end in said housing, one of said shafts being journaled in said cup-shaped member and the other of said shafts being journaled in said end member, said cup-shaped member and said end member having mating flanges thereon together with means for securing the flanges together, input and output clutch discs connected to the respective shafts, said housing having a charge of oil therein for forming an oil film between the discs, means including an annular electromagnet for varying the pressure exerted between the two discs thereby to vary the thickness of the oil film, at least one of said discs having radial grooves of generally square cross-section and having relatively sharp edges formed on the face thereof for pumping oil outwardly so that the heat of said oil is transferred to the inner wall of the cup-shaped body por tion, and means including an air circulating fan mounted on said coupling input shaft for removing said transferred heat.
12. In a variable speed coupling for driving a knitting machine or the like, the combination comprising a housing, input and output shafts journaled in said housing axially arranged end to end, input and output discs secured to the ends of said shafts, said discs having engaging clutch faces, a charge of oil in said housing, at least one of the discs having radial grooves of generally square cross-section and having relatively sharp edges in its face for conducting said oil and forming a film between the discs, means including an electromagnet for varying the pressure exerted between the discs thereby to vary the thickness of the oil film, the other one of said discs having an annular liner of friction material and said grooved disc having means for conducting oil to the grooves so that upon rotation of the disc oil is drawn into and expelled from said grooves for replenishment of said oil film and for transferring the heat of said oil away from said discs.
13. A variable speed coupling as claimed in claim 12 wherein said grooved disc includes biasing means mounted therein bearing on said liner so that when the electromagnet is de-energized, the force exerted by said biasing means causes immediate separation of said discs.
14. In a drive system for a knitting machine or the like having a malfunction detector, the combination comprising a current source, a source of rotative power rotating at a speed which is at least as great as themaximum speed required by the machine, a variable speed drive coupling interposed between the power source and the machine said drive coupling having a housing including alined input and output shafts carrying input and output discs, said discs being made of magnetic material, means including a coil for varying the magnetic attraction between the discs thereby varying the torque exerted between the faces of the discs, a tachometer on said output shaft for producing a speed signal, means for producing an adjustable. reference signal, an amplifier responsive to the net signal and having said electromagnet in its output circuit for correctively varying the current through the magnet thereby to maintain a constant output speed, saidhousing having a charge of oil therein, means for feeding oil between the faces of the discs, and means responsive to the operation of the malfunction detector for disabling flow of current through said electromagnet so that rotation of the output shaft ceases upon either a malfunction or failure of the current source.
References Cited UNITED STATES PATENTS 2,884,107 4/1959 Frankel 192-84 2,107,954 2/1938 Morton et al. 192113.1 2,289,440 7/ 1942 Kugel.
2,348,025 5/1944 Peets et al. 192113.1 3,007,561 11/1961 Harting 19284 3,022,876 2/1962 Frankel 192113.2 X 3,058,555 10/1962 Scofield et al 19284 X 3,063,532 11/1962 Jaeschke 192113.2
MERVIN STEIN, Primary Examiner.
R. FELDBAUM, Assistant Examiner.