US2598555A - Variable output transformer - Google Patents

Description

y 1952 J. E. JONES ET AL 2,598,555

VARIABLE OUTPUT TRANSFORMER Original Filed July 2, 1948 Patented May 27, 1952 VARIABLE OUTPUT TRANSFORMER Jesse E. Jones, Wauwatosa, and James B. Reeves,

Whitefish Bay, Wis., assignors to Cutler-Hammer, Inc., Milwaukee, Wis., a corporation of Delaware Original application July 2, 1948, Serial No. 36,718. Divided and this application April 20, 1951, Serial No. 222,026

2 Claims.

This invention relates to transformers and more particularly to transformers of the variable output type.

The present application is a division of our application Serial Number 36,718, filed July 2, 1948, now Patent No. 2,571,454.

A primary object of the present invention is to provide a transformer affording an output signal variable throughout a wide range, and

Another object is to provide a transformer of the aforementioned type having variable coupling means which is substantially frictionless and operable without producing any retarding torque, whereby the coupling means will respond to a very small operating force such as may be transmitted through textile thread without undue strain thereon.

Other objects and advantages of the invention will hereinafter appear.

The accompanying drawing illustrates a preferred embodiment of the invention which will now be described, it being understood that the embodiment illustrated is susceptible of various modifications without departing from the scope of the appended claims.

In the drawings:

Figure 1, which is in part diagrammatic and in part schematic, illustrates a control system for motor-driven thread winding apparatus incorporating the invention;

Fig. 2 is a view in front elevation of a variable coupling transformer shown schematically in Fig. l, and

Fig. 3 is a sectional view taken along the line 3-3 of Fig. 2.

Referring to Fig. 1, it shows a motor-driven thread winder comprising a reel or bobbin It! on which a length of thread II is to be wound by means of a three phase alternating current motor I2 which drives bobbin IEI through a shaft I3. The thread II is shown as being supplied from a spool I4 which may here be assumed to be driven at a constant rotational speed through means not shown.

Idler rollers I5 and I6 are suitably placed in the path of thread I I between spool I4 and bobbin ID to facilitate the formation of a loop or festoon in thread I I which passes through a thread guide or eyelet I'I secured to a tension arm I8 of a control device l9. Tension arm I8 is non-rotatably secured to a shaft 20 of control device I9 and is provided with a weight 2| which may be variously positioned thereon to adjust the force exerted through the eyelet I! on thread I I.

The motor I2 is shown as being of the squirrel cage type, its primary being provided with supply terminals T T and T which are respectively connected to supply lines L L and L of a three phase alternating current source; terminal T being connected to supply line L in series with a resistor 22. Motor I2 may be any suitable three phase alternating current motor having high secondary resistance, a motor of the so-called torque type being preferred.

A gas filled triode tube 23 is connected at its anode 23 to terminal 1' of motor I2 and at its cathode 23 to terminal T of said motor. Tube 23 is provided with a control grid 23 which is connected to one end of a coil 24 of control device I9 through a resistor 25 and a rectifier 26. A capacitor 21 and a resistor 28 are connected in parallel between the cathode 23 of tube 23 and the interconnnection between the resistor 25 and rectifier 26, whereas a point common to cathode 23 resistor 28 and capacitor 21 is connected to the end of coil 24 opposite the end aforementioned. A second capacitor 29 connected between cathode 23 and control grid 23 of tube 23 is provided for by-passing transient and harmonic currents.

Control device I9 is also provided with a coil 30 which is connected across supply lines L and L and which has its longitudinal axis curved concentrically with shaft 20. An arm 3I is nonrotatably secured to shaft 20 and is adapted to assume various angular positions in'rcsponse to rotational movement of shaft 20 to vary the magnetic flux linking the coils 24 and 30. A frame 32 (shown in broken lines) is provided to support the aforedescribed components of control device I9. The arm 3I and frame 32 are preferably formed of magnetic material such as soft steel to provide a low reluctance path for the magnetic flux induced by energization of coil 30'. A preferred form for control device I9 will be hereinafter described in detail.

As will be apparent, the coil 30 will be energized whenever supply lines L and L are energized and as a result a voltage will be induced in the coil 24. In the position of arm 3I depicted in Fig. 1, the maximum possible magnetic coupling obtains between coils 24 and. 30 and consequently the maximum possible voltage is induced in coil 24. If tension arm I8 is'moved clockwise from its position depicted in Fig. 1, the arm M will be moved a corresponding amount in the same direction and the magnetic coupling between coils 24 and 30 will be decreased. As a result the voltage induced in coil 24 will be reduced in proportion to the decrease in magnetic coupling. Movement of arm 3| upwardly beyond a certain point will not effect any appreciable reduction in the magnetic coupling, such point corresponding to minimum voltage induced in coil 24. The action of control device I9 to produce a voltage varying in value between a maximum and minimum in relation to mechanical movement of a part thereof is utilized to control the conduction of tube 23 for regulation of the speed of motor l2, as will now be explained.

Tube 23 is only capable of conduction when the potential polarities of its anode 23 and cathode 23 are respectively positive and negative which occurs on alternate half cycles when the voltage at motor terminal T is positive with respect to the voltage at terminal T of said motor. As a further condition to conduction of tube 23 the potential of its control grid 23 must rise to a critical value, at which conduction is initiated during such half cycles. As will now be explained, the potential attained by control grid 23 during each such half cycle is dependent upon the peak value of the induced voltage in coil 24 attained during preceding half cycle when tube 23 is non-conductive.

The coil 24 is so connected that on the half cycles when tube 23 is non-conductive, the voltage induced in coil '24 will effect current flow through rectifier 26 and will charge capacitor 27 to a potential corresponding to the peak value of voltage induced in coil 23. As a result the potential of control grid 23 will be made negative with respect to the potential of cathode 23 in an amount corresponding to the potential to which capacitor 21 is charged and in any event to an amount blocking conduction by tube 23. Unblocking of the tube is then dependent upon discharge of the capacitor through resistor 25, which discharge begins as soon as the surge of current through the coil 24 reaches and passes its peak. According to the charge of the capacitor and its rate of discharge unblocking of tube 23 is effected during the next half cycle or may be continued throughout the next half cycle. In the latter event the tube is rendered idle while in the former event the tube conducts for part or all of the half cycle depending upon the movement at which the negative voltage impressed upon the control grid 23 is reduced sufficiently by discharge of the capacitor to permit the tube to become conductive with its anode and cathode respectively subjected to positive and negative voltages. When a condition of maximum magnetic coupling obtains in control device 19, capacitor 2'! will be charged to such a potential that its subsequent discharge will consume the next half cycle, thus rendering'the tube idle during such half cycle. Reducing the degree of magnetic coupling in control device 19 will of course reduce the potential to which capacitor 21 is charged, and if it be reduced sufficiently, then the negative potential impressed upon the control grid 23 will be reduced to permit conduction by tube 23 during at least part of the half cycle following the half cycle during which the capacitor reserves its charge. A further reduction of magnetic coupling in control device l9 will result in initiation of conduction of tube '23 earlier in its conducting half cycles.

Conduction of tube 23 effects a single phase connection of motor l2, both its terminals T and T being connected to supply line L Consequently while tube 23 conducts, the motor primary is afforded unbalanced excitation. The resistor 22 normally effects a slight voltage unbalance of the motor primary but the resistor need not be of a value such as to effect more than a than it is fed from spool M.

negligible unbalance. Assuming that tube 23 conducts during portions of alternate half cycles the motor periodically changes from a condition of almost balanced to unbalanced excitation which causes the speed of the motor to decrease. The greater the average current conducted by tube 23, the greater will be the reduction in speed of motor I2.

As will be understood, tension arm 18 acting through the eyelet l1, maintains the thread H under constant tension in its passage from spool M to the bobbin H3 so long as a loop is maintained between rollers l5 and it; the amount of tension being determined by the magnitude 3 and position of weight 21 on arm 13. The diameter of bobbin H] will progressively increase due to successive winding layers of thread I I and the peripheral speed of bobbin ill will tend to increase with consequent tendency to wind faster This causes the aforedescribed loop in thread H to progressively decrease in length as the bobbin it increases in diameter. As a result tension arm "3 is progressively moved in the clockwise direction with consequent progressive reduction in the magnetic coupling between coils 24 and 39 of control device I9. Thus it will be seen that the speed of motor 12 will be progressively reduced so that the peripheral speed of bobbin It will be main- M, tained substantially constant relative to the peripheral speed of spool I l which decreases as thread is unwound therefrom.

.Vhereas it has here been assumed that thread i l is unwound from a spool driven at a constant 3 rotational speed such a condition of thread supon control device l9 can be best reduced by increasing the effective length of tension arm l8.

Referring to Figs. 2 and 3, they show a preferred form for control device Ii! which will now be described in detail.

The coils 2-5 and 35 are provided with individual carriers E l and Ell of a spool type, which are preferably formed of a non-magnetic material such as a linen based Bakelite. Coil 38 is rigidly secured to plate 32 by a plurality of attaching lugs 5 2 which are sheared from plate 32, peripherally about an end flange of carrier 36 and bent over said end flange. An opening extending axially through carrier 30 is provided to freely accommodate the shaft which preferably is steel and on which the coupling arm 3! is non-rotatably secured. Coil 24 is secured to plate 32 in a spaced relation to coil 3i) by means of a screw which extends through a central opening in carrier 2d and which takes into a threaded opening formed in plate 32.

An inverted U-shaped bearing bracket formed of a non-magnetic material such as brass is secured to plate 32 in a straddling relation to coil by means of screws which extend through openings in oppositely depending end portions of said bracket and take into threaded openings in plate 32. The portion of bracket 35 overlying coil 3%] is provided with a threaded opening concentric with respect to shaft 21) to accommodate a screw type bearing seat 35 for shaft 20. The end of seat 36 adjacent shaft 20 is provided with an inverted conical recess to partially accommodate a small polished steel ball 31 which is also partially accommodated in a corresponding recess formed in the adjacent end of shaft 20. Seat 36 is slotted at its other end to facilitate its adjustment relative to bracket 34 so that its recessed end may be moved toward or away from shaft 20. A desired adjustment of seat 36 is maintained by means of a nut 36 which has engagement with the threaded shank of seat 35 to be clamped against bracket 34 to lock seat 33 in adjusted position.

Shaft 2!), as aforedescribed, extends through the coil 30 and also extends through and beyond plate 32, the latter being provided with a clearance opening to accommodate said shaft. A ball bearing 38 is fitted on shaft 20 with a driving fit to afford radial bearing support for the latter within a bearing housing 39 which is secured to plate 32 oppositely of the coil 30. The housing 39 is secured to plate 32 by a plurality of screws 40 which pass through said housing marginally thereof and take into threaded openings formed in plate 32. Housing 39 is suitably formed interiorly to tightly engage with ball bearing 38 peripherally about the outer race of the latter and to restrain the same and shaft 20 against any substantial axial movement. A clearance opening extending through the end wall of housing 39 is provided to accommodate shaft 20 which extends beyond said housing.

The coupling arm 3| is provided with a hub portion 3| which has an opening to accommodate with clearance a reduced threaded end por tion 20 of shaft 20. Arm 3|, is non-rotatably secured to shaft 20 by a nut 4| threaded onto the portion 20 of shaft 20 to clamp said arm against an annular shoulder 20' formed on shaft 20. Arm 3| is provided with a straight portion 3| which is integrally connected to the hub 3| at one end thereof and which merges at its other end with a portion 3| which depends perpendicularly toward the plate 32. The portion 3| 0 is so proportioned in length as to freely clear the carrier 24 upon angular movement of arm 3|. Arm 3| is also provided with a circular segment portion 3| which is integrally connected with the hub portion 3|; said portion 3| affording limitation of angular movement of arm 3| by engagement of its radial sides with the portions of bracket 34 which extend perpendicularly with respect to plate 32. Preferably, the portion 3| is so proportioned as to afford balance of the arm 3| with respect to its pivotal axis.

Tension arm I8 is non-rotatably secured, in any preferred manner, to the portion of shaft 20 which extends beyond the housing 39. While tension arm I8 is depicted in Figs. 2 and 3 as being mounted on shaft'MI in certain relation with respect to the portion 3| of coupling arm 3|, it may be mounted in various relations to coupling arm 3| according to the particular application of control device l9. Tension arm I 8 is depicted as having the open eyelet H as preferred thread engaging means, but as will be apparent this may be replaced, if desired, by a roller when used in connection with web materials or the like.

As will be apparent, when coupling arm 3| is in the position depicted in full lines in Fig. 2, the condition of maximum magnetic coupling between coils 24 and 30 is afforded and the voltage induced in coil 24 will be at a maximum. Conversely when coupling arm 3| is in the position depicted in broken lines in Fig. 2, a condition of minimum magnetic coupling between coils 24 and 30 is afforded and consequently the voltage induced in coil 24 will be at a minimum. Accordingly, the voltage induced in coil 24 can be varied between minimum and maximum values by variously positioning coupling arm 3| between the positions aforedescribed.

As will be understood by those skilled in the art, coil 24 will have a considerably greater number of coil turns than coil 33 and the ratio of coil turns will depend upon the particular application and the circuit to which the coil 24 is connected.

We claim:

1. A transformer comprising a member formed of a material of low magnetic reluctance, a first coil for predetermined alternating current excitation mounted contiguously to said member, a second coil mounted contiguously to said member in a manner such that its axis is parallel to the axis of the first coil and spaced therefrom by a distance at least equal to the sum of the maximum radii of said coils, a shaft concentric with said first coil and extending through said member, anti-friction bearing means supported on said member and affording said shaft rotational bearing support, a member secured to the first mentioned member and straddling said first coil and one end of said shaft, anti-friction bearing means for said one end of said shaft carried by the last mentioned member, and a second member formed of a material of low magnetic reluctance secured to said shaft in overlying relation to said first coil, said last mentioned member being so proportioned as to :be statically balanced about the axis of said shaft and being movable by rotation of said shaft into different relations with said second coil to vary the magnetic coupling between said coils thus to vary the potential induced in said second coil.-

2. In combination, a base member formed of a material of low magnetic reluctance, a first coil for predetermined alternating current excitation mounted contiguously to said base member, a second coil mounted contiguously to said base member in a manner such that its axis is parallel to the axis of the first coil and spaced therefrom by a distance at least equal to the sum of the maximum radii of said coils, a shaft concentric with said first coil and extending through said member, anti-friction bearing means supported on said member and affording said shaft rotational bearing support, a non-magnetic bracket member secured to said base member and straddling said first coil and one end of said shaft, anti-friction bearing means for said one end of said shaft carried by said bracket member, an arm member formed of a material of low magnetic reluctance secured to said shaft in overlying relation to said first coil, said arm member being so proportioned as to be statically balanced about the axis of said shaft and being movable by rotation of said shaft into different relations with said second coil to vary the magnetic coupling between said coils, and a tension arm non-rotatably secured to said shaft, said tension arm having means at its free end to accommodate and guide a thread and also having an adjustably positionable weight for varying the tension on said thread.

JESSE E. JONES. JAMES B. REEVES.

No references cited.

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