US1960293A - Circuit-control means - Google Patents

Description

D. ULREY CIRCUTv CONTROL MEANS Filed Dec /CZa/ May 29, 1934.

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lNvENToR ayon U/r'e/v f ATTORNEY Patented May 29, 1934 PATENT OFFICE CIRCUIT-CONTROL MEANS Dayton Ulrey, Wilkinsburg, Pa., assignor to Westinghouse Electric & Manufacturing Company, a corporation of Pennsylvania Application December 10, 1929, Serial No. 412,999

2 Claims. (Cl. 172-240) My invention relates to means for controlling electric currents and particularly to control means for electric motors of the reciprocating type.

One object of my invention is to provide means for causing a reciprocating motion to be imparted to the armature of an electric motor by making and breaking a current through a winding of the motor at appropriate intervals.-

Another object of my invention is to provide means for interrupting the ilow` of relatively large .currents at relatively frequent intervals without arcing.

Another object of my invention is to provide means for interrupting heavy electric currents Aand currents ilowing through highly inductive circuits without the arcing which ordinarily takes place when such circuits are opened under load.

' A further object of my invention is to provide means for making and breaking heavy electric currents at frequent intervals by means of apparatus which is not subject to the deterioration produced by aroing between separated contacts.

Other objects of my invention will become apparent on' reading the following description, taken in conjunction with the drawing, in which Figure 1 shows, schematically, a reciprocating electric motor provided with a grid-controlled 'mercury-arc device and embodying the principles of my invention, and

Fig. 2 is a similar view of an alternative means for controlling the operation of a mercury-arc device. g

' Reciprocating electric motors, adapted to cause a rapid reciprocation of movable members, have previously been proposed for use in electric hammers, pile drivers and apparatus of similar kinds. Many such electric motors aredesigned to be operated by causing heavy currents to flow through windings which vactuate movable armatures in rectilinear paths in one direction. The ,current is then interrupted in these windings, and, in

, some cases, is caused to start flowing through other windings, thereby permitting the armature to be moved in the opposite direction toward its initial position, where it strikes a blow upon the pile or other object which the hammer is intended to drive.

When such reciprocation motors are designed for heavy duty, it is necessary to make and break electric currents of several hundred amperes at frequent intervals. 'I'he repeated interruption of such large currents at frequent intervals has vacuum electrical-discharge devices provided A with hot cathodes may be interrupted by imposing a negative charge upon a control electrode positioned between the anode and the cathode. Such devices, however, suffer from the limitation that it is impossible, with cathodesn of practical dimensions, to obtain currents of a magnitude suitable for the operation of electric mo.- \tors of large power. On the other hand, gaseous discharge devices, particularly those of the mer-'- ,cury-arc type are capable of carrying currents of suilicient magnitude; but, when it is attempted to interrupt current ow in such devices by imposing a negative charge on control electrodes, it is found that current ow continues substantially unaffected. It is, however, found that, once then current in a gaseous discharge device has been" caused to fall to zero by some external agency, a negative charge imparted to the grid will prevent the resumption of current flow therein. It is, accordingly, possible by supplying current through a grid-controlled gaseous discharge device from analternating-current source toy electrical power apparatus, to cause an effective interruption of current flow at the end -making the control electrode positive in poten- By vemploying two 1 gaseous dischargedevices, of which a mercurytial relative to the cathode.

arc relay is one familiar example, each of said devices permitting the llow of current from the alternating-current source to the load during one half-period of said current, it is possible to supply current continuously through any desired number of half periods of the alternatingcurrent source; and hence, for practical purposes, to initiate and interrupt the flow of heavyload currents for any desiredintervals of time. Since such arrangements employ no separable contacts which are required to open while carrying the power current, no difficulties are experienced from arcing and deterioration, such as is characteristic of ordinary mechanical switching devices.

With the foregoing principles and objects of invention in mind, reference is made to Fig. 1 of the accompanying drawing, in which the reference numeral l designates the windings on the stator of a reciprocating motor of a type too well known in the art to require detailed description. The flow of current from an alterhating-current source 2,. through the windings- 1, produces a ilux in the magnetic circuit of the reciprocating motor and attracts a movable armature 3 which may be mechanically interlinked with a hammer or other device 4, to which it is desired to impart reciprocating motion. Current through the windings 1 ows to a control aggregate comprising two mercury- arc tubes 5 and 6 having main anodes 7, control electrodes 8, and mercury cathodes 9 kept continuously excited by side branches 10 fed by transformers 11. The cathode 9 of arc tube 5 is connected to the anode 7 of arc tube 6, and cathode 9 of arc tube 6 is connected to anode 7 of arc tube 5. The control electrodes 8 of arc tube 5 may be connected, through a limiting resistor, to the hinge terminal 13 of a double-pole double-throw switch 12, while the control electrode 8 of arc tube 6 is connected tothe other hinge terminal 14. One diagonally opposite pair of the cooperating terminals 15 of the switch 12 may be connected to one side of the source 2, while the other pair of terminals 16 of said switchare connected to the other side f source 2. The switch 12 is mechanically interlinked with the reciprocating armature 3 through a lost-motion connection so that, when the latter is in its lowest position, the switch 12 is thrown to the upper position indicated in Fig. l, thus connecting each control electrode 8 to itsl adjacent anode 7 and to maintain this connection until the armature 3 reaches a position near the upper end of its desired stroke. The mechanical linkage is so constructed and'assembled that it then interrupts the contact between the control electrodes 8 and their adjacent anode 7 and makes a connection between the said electrodes and the side of source 2 which is connected to their adjacent cathodes 9, thus giving the control electrodes the same potential as said cathodes.

The mode of operation of the above-described apparatus is as follows:

Current flows from the side of the alternatingcurrent source 2 which happens to be positive at any particular instant to the adjacent anode of one of the mercury arcs 5, 6. Suppose that this is the upper wire from source 2, as it appears in Fig. 1. If the armature 3 is in its lowest position and the switch 12 is, therefore, in its upper position, the control grid 8 of arc tube 5 has a positive potential relative to the cathode 9 thereof, and, consequently current iiows through the mercury arc 5 to the wire leading from the cathode of 5 to the anode of arc tube 6 and, through the lead to windings 1 of the reciprocating motor, to -the other side of the alternating-current source 2. When the polarity of the alternating-current source 2 reverses, current ilow ceases from the anode oi arc tube 5 to the cathode 9 thereof, the control electrode 8 of arc tube 6 being at substantially the same potential as its anode 7 and, therefore, permitting current flow. It is to -be noted in passing that the windings 1 of the hammer are interposed between the control electrode 8 and the anode 7 of the tube 6. However, when the tube 6 is deenergized, (as it is when the potential supplied to the tube 5 passes from a negative polarity to a positive polarity) the circuit including the control electrode 8 and the anode 7 is an open circuit between the anode and control electrode, since the inter-electrode capacity between these' electrodes is small. Hence the control electrode 8 of the tube 6 is substantially at the same potential as the anode 7. Current then ows from the lower line of source 2, through' the windings 1 of the hammer to the anode 7 of arc tube 6 through the tube 6 to the upper line of source 2. Current flow thus continues through one mercury-arc tube or the other so long as the control electrodes 8 are connected to their adjacent anodes 7. The armature 3 is, accordingly, drawn upward, and the lost-motion connection permits this movement to continue until, when the armature 3 nears the upper end of its stroke, the switch 12 is reversed and caused to make the control grids 8 of the same potential as their adjacent cathodes 9 when the tubes 5 and 6 are in their turn deenerg'zed. At the end of the next succeeding half cycle of alternating current from the source 2, current iiow cannot start through either of the arc tubes 5 and 6 because their control grids are at cathode potential, and current flow through the windings 1 remains interrupted. The force of gravity or, if desired, any other biasing means, then causes the armature 3 to fall downward toward its initial position, where it imparts a` tion connection, switch 12 remains in the condition last described until the armature 3 approaches the lower end of its stroke; switch l2 is thenymoved to again give the control electrodes 8 the potential of their respective anodes; current flow can then resume from the alternating-current source 2 through the windings 1 and is employed to impart the desired potentials to.

control electrodes 8. The elements shown in Fig. 2 are like those designated by the same rei'- erence numerals in Fig. 1, except as indicated in the following description.

l Control electrodes 8' are connected together to the hinge terminal 23 of a single-pole doublethrow switch 22 through a protective resistor 24.

One terminal 25 of switch 22 is connected to the positive terminal 26 of a source of unidirectional electromotive force 27, and the other terminal 28 of switch 22 is connected to the negative terminal of source 27. A midpotential point of source 27, which, preferably, is at a potential greater than the peak value of the electromotive force of source 2 above the lower terminal of the battery, is connected'to the anode lead of one of the arc tubes 5 and 6.

The switch 22 is so inter-linked with the movements of the armature 3 of the reciprocating motor, through a lost-motion device, that terminal 23 ofswitch 22 is connected to the positive terminal 26 of source 27 while the armature 3 is moving upward toward its top position and is then connected to the negative terminal 28 of source 27 when it is desired that the armature 3 shall have a downward movement. When the terminal 23 is connectedto the negative terminal 28 of the battery 27, the control electrode 8 of tube 5 is at a potential which isRbelow the potential of the cathode 9 of the tube by an amount equal to the excess of the potential difference between the lowest point or the battery 27 and the midpoint over the potential of the source. On the other hand, the control electrode 8 ofthe tube 6 is at a potential below the potential bf the cathode by an amount equal to the difference of potential between the mid-point of the battery 27 and the lowest point. When the terminal 23 is connected to the positive terminal 25 of the battery the control electrode 8 of the tube 6 is at a potential above the anode which is equal to the above excess while the control electrode of the tube 5. is at a potential above the anode is equal to half the potential of the battery. By this expedient, arc tubes 5 and 6 are both rendered capable of carrying current when the armature is to be moved upward; and are rendered incapable of acquiring conductivity when the armature 3 should be moved downward.

Since the switch 22 merely controls the potential of control electrodes 8, it is not required to interrupt any substantial current, and no difliculties from arcing at its terminals are experienced.

While I have described specic circuit connections, it will be recognized that other circuit connections may readily be devised, the principal requirement being a system by means of which one-half wave of alternating current may ow from one arc tube and the other half Wave of alternating current may flow from another arc tube. Alternative arrangements which permit the performance of such functions are Well known in the art. It will also be recognized that the windings 1 of the motor are not necessarily separate from eachother in physical position but may be composed of alternate coils symmetrically distributed upon the magnetic circuit of the motor.

It will also be recognized that, while I have described my control arrangement as applied to a reciprocating motor, its use is by no means limited to this particular eld but may be applied to the operation of motors of any type, or, in fact, to the control of large currents flowing to an electrical load of any type.

In accordance with the patent statutes, I have described a particular embodiment of my invention, buty it will be evident to those skilled in the art that the principles thereof are of broader application, and many different ways of embodying-thern will be readily apparent. I desire, therefore, that the following claims shall be given the broadest interpretation of which their terms are susceptible in view of the limitations imposed by the prior art.

I claim as my invention:

l. In combination with an electrical load an alternating-current supply source connected to said load through a plurality of gaseous electrical-discharge devices of the unilaterally conductive type each provided with an anode, a cathode and a control electrode, 'the anode of each of the devices being connected with the cathode of the other device and switching means for connecting each said control electrode at times to one side of said source and at other times to the other side of said source, said control electrodes being connected respectively to opposite sides of said source.

2. In combination with reciprocating electric motor, an alternating-current source connected to said motor through a plurality of electrical gaseous discharge devices each having an anode, a cathode and a control-electrode, the anode of each said discharge device being connected to the .cathode of the other device and means responsive to the movements of said motor to give said control electrodes at times the same polarity as their respective anodes and at other times polarities opposite to those of their respective anodes.

DAYTON ULREY.

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