US2036783A - Circuit-control means - Google Patents

Description

April 7, 19366 D. ULREY 2,036,783

CIRCUIT CONTROL MEANS Original Filed Dec. 10, 1929 WITNESSES: INVENTOR dab A W Dayfof) U/r'ey v I v v ATTORN I Patented Apr. 7, 1936 UNITED STATES PATENT OFFICE CIRCUIT-CONTROL MEANS Original application December 10, 1929, Serial No. 412,999, now Patent No. 1,960,293, dated May 29, 1934.

Divided and this application May 19, 1934, Serial No. 726,591

Claims. (Cl. 175-373) My invention relates to means for controlling electric currents and particularly to control means for electric motors of the reciprocating type.

This application is a division of my application Serial No. 412,999, filed December 10, 1929, patented May 29, 1934, No. 1,960,293.

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 flow of relatively large currents at relatively frequent intervals without arcing.

Another object of my invention is to provide means for interrupting heavy electric currents and currents flowingthrough 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 arcing between separated contacts.

Other objects of my invention will become apparent on reading the following description, taken in conjunction with the drawing, in which the single figure is a diagrammatic view showing the essential features of my invention.

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 are designed to be operated by causing heavy current to flow through windings which actuate 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 reciprocating motors are designed for heavy duty, it is necessary to make and break electric currents of several hundred amperes at frequent intervals. The repeated interruption of such large currents at frequent intervals has hitherto presented a problem for which no successful solution has been available.

In accordance with the principles of my inven\ tion, I control the flow of current from an alternating-current source through the operative windings of a reciprocating motor, of the type above described, through the agency of a gridcontrolled gaseous discharge device. A mercury arc, in vacuum, is a convenient form of such discharge device, although my invention is not limited to gaseousor' vapor discharge devices of this particular type.

As is well known, the flow of current in highvacuum electrical-discharge devices provided 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, sufier from the limitation that it is impossible, with cathodes of practical dimensions, to obtain currents of a magnitude suitable for the operation of electric motors of large power. On the other hand, gaseous discharge devices, particularly those of the mercury-arc type are capable of carrying currents of suflicient magnitude; but, when it is attempted to interrupt current flow in such devices by imposing a negative charge on control electrodes, it is found that current flow continues substantially unaffected. It is, however, found that, once the 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 an alternating-current source to electrical power apparatus, to cause an effective interruption of current flow at the end of any half cycle of the alternating current by making a control electrode negative in potential relative to the oathode; and, conversely, to initiate flow of current at any desired instant by making the control electrode positive in potential relative to the cathode. By employing two gaseous discharge devices, of which a mercury-arc relay is one familiar example, each of said devices permitting the flow of current from the alternatingcurrent source to the load during one halfperiod of said current, it is possible to supply current continuously through any desired number of half periods of the alternating-current source; and hence, for practical purposes, to initiate and interrupt the flow of heavy-load currents for any desired intervals 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 isJnade to the accompanying drawing, in which the reference numeral I 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 alternatingcurrent source 2, through the windings I, produces a flux in the magnetic circuit of the reciprocating motor and attracts a movable arma ture 3 which may be mechanically interlinked with a hammer or other device I, to which it is desired to impart reciprocating motion. Current through the windings I flows to a control aggregate comprising two mercury-arc tubes 5 and 6 having main anodes I, control electrodes 8, and mercury cathodes 9 kept continuously excited by side branches I0 fed by transformers II. The cathode 9 of arc tube 5 is connected to the anode 1 of arc tube 6, and cathode 9 of arc tube 6 is connected to anode I of arc tube 5.

The control electrodes 8 are connected together to the hinge terminal 23 of a single-pole double-throw 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 21, and the other terminal 28 of switch 22 is connected to the negative terminal of source 21. A midpotential point of source 21, which, preferably is at a potential greater than the peak value of the electro-motive 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 interlinked with the movements of the armature 3 of the reciprocating motor, through a lost-motion device, that terminal 23 of switch 22 is connected to the positive terminal 26 of source 21 while the armature 3 is moving upward toward its top position and is then connected to the negative terminal 28 of source 2'! when it is desired that the armature 3 shall have a downward movement. When the terminal 23 is connected to the negative terminal 28 of the battery 21, the control electrode 8 of tube 5 is at a potential which is below the potential of the cathode 5 of the tube by an amount equal to the excess of the potential diil'erence between the lowest point of the battery 21 and the midpoint over the potential of the source. On the other hand, the control electrode 8 of the tube 6 is at a potential below the potential of the cathode by an amount equal to the difference of potential between the midpoint of the battery 21 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 which 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, andno difiiaosensa culties from arcing at its terminals are experienced.

While I have described specific 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 flow from one are tube and the other half wave of alternating current may flow from another are tube. Alternative arrangements which permit the performance of such functions are well known in the art. It will also be recognized that the windings I of the motor are not necessarily separate from each other 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 field 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, but it will be evident to those skilled in. the art that the principles thereof are of broader application, and many different ways of embodying them 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:

1. In combination with an electric translating device requiring current to be interrupted for appreciable time intervals, a pulsating-voltage source connected to supply current to said device, and means, for controlling the current to said translating device from said source comprising a gaseous discharge device having electrode control and means for making a control electrode at times positive and at other times negative in potential relative to the anode of said discharge device by a voltage greater than the maximum instantaneous voltage of said source.

2. Apparatus according to claim 1 characterized by an additional gaseous discharge device having a control electrode, the cathode and anode of said additional discharge device being so connected as to be maintained at substantially the same potential as the anode and cathode respectively of said first-named discharge device and the control electrode of said additional discharge device being so connected as to be maintained at substantially the same potential as the control electrode of said first-named discharge device.

3. In combination with an electric translating device requiring current to be interrupted for appreciable time intervals, at pulsating-voltage source connected to supply current to said device, and means for controlling the current to said translating device from said source, comprising a gaseous discharge device having a control electrode and an anode, and a current path extending from the control electrode to the anode but devoid of other electrical connection to other electrodes of said discharge device, said path including means for making said control electrode at times negative in potential relative to said anode by a voltage greater than the maximum instantaneous voltage of said aoaavas source, and at other times positive in potential relative to said anode.

4. In combination with an electric translating device requiring current to be interrupted for appreciable time intervals, a pulsating-voltage source connected to supply current to said device, and means for controlling the current to said translating device from said source, comprising a gaseous discharge device having a control electrode and an anode, and a current path extending from the control electrode to the anode but devoid of other electrical connection to other electrodes of said discharge device, said path including means for intermittently interposing between said control electrode and said anode a second

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