US2255905A - Electrical control - Google Patents

Description

P 1941- R. M. soMERs ET AL 2,255,905

ELECTRICAL CONTROL Filed April 6, 1959 i R Fw y r d :95am ems Charles I Jacobs BY 4%,... 1. A ORNEY Patented Sept. 16, 1941 ELECTRICAL CONTROL Richard M. Somers, West Orange, and Charles T.

Jacobs, New Providence,

N. J., assignors to Thomas A. Edison, Incorporated, West Orange, N. J a corporation of New Jersey Application April 6, 1939, Serial No. 266,338

18 Claims.

This invention relates to electrical control, and more particularly to such control of the position of a movable systemwhich may be a system, itself of any nature, which it is desired to move selectively between a plurality of positions. An

embodiment of the invention involves the me chanical association with the movable system of electrically actuable moving means-typically electromagnets-and the control or selective actuation of the moving means, from a remote point if desired, through simple and improved switch and conductormeans. In a preferred embodiment of the invention the control switch means is movable at will between two positions, and by very simple arrangements the movable system is moved between a respective two positions in accordance with the movement of the switch means. It is an object of the invention to provide a novel and simple control of the type described.

It is an object to provide an improved control of that type employing a minimum number of conductors between the control means and the movable system.

It is an object to provide simple means whereby the movable system will be kept in step with the control means with a high degree of reliability.

It is an object to provide simple means whereby the movable system, if out of step, will be promptly and automatically restored to step with the control means.

It is an object to provide an improved control 1 wherein the actuating currents for movement of the movable system in a plurality of directions are conveyed thereto from the control means through the same conductor.

It is an object, in such a control, to render the movable system selectively responsive to the different control means movements with a high degree of reliability.

It is an object, in such a control, to provide improved means for preventing multiple operation of the movable system upon single manipulations of the control means.

It is an object to provide a novel arrangement of electromagnetic device and system moved thereby only upon lower-power actuation of that device.

Other and allied objects will more fully appear from the following description and the appended claims.

In the description reference is had to the accompanying drawing, of which Figure 1 is a schematic diagram of a control embodying our invention in one form; and

Figure 2 is a schematic diagram of a portion of a control embodying our invention in a modified form, Figure 2 being intended for optional substitution for the righthand portion of Figure 1.

In the illustration of our invention We have shown a movable system comprising a lever I, pivoted as at I and rockable for example from the illustrated inclined position to a posiiton correspondingly inclined on the other side of vertical. Any other device whose control between two positions is to be eil'ected may be connected to the lever I, thus entering into the movable system; this has been schematically indicated by the device 4 having the control lever 3, and the rod 2 terminally pivotally connected with and coupling together the levers 3 and I. Purely as an example, the device A may be a clutch or other apparatus, moved between engaged and disengaged positions by the movement of the lever I.

For moving the lever I between its two positions there has been illustrated an assembly of two electromagnets II and I2, alternately actuable to effect alternately directed lever movements. While the response of the lever to the electromagnets may be a direct one, we prefer that this response take place through the intermediary of a double pivoted armature arrangement, following the teachings of U. S. Patent No. 1,380,486, issued June 7, 1921, on application of Sam G. Langley. While the armature arrangement may follow as closely as desired the arrangement shown in that patent, we have illustrated it in simple form as comprising a pair 01' armatures I3 and I 4 pivoted at and extending upwardly from points I3 and I4 on either side of the lever-pivoting point I, and a spring I1 tensioned between the armatures to bias them against the respective sides of an enlarged head Ia provided at the top of lever I. The electromagnets I I and I2 may be positioned respectively to the right and left of intermediate portions of the armatures I3 and It, the electromagnet axes lying for example in a common horizontal line. The components may be arranged so that when (as illustrated) armature I3 touches the pole tip I I of electromagnet II, that armature will be substantially vertical, lever I will be in its first position (of rightward-upward inclination), and armature I 4 will have a rightward-upward inclination and will be spaced from the pole tip I2 of electromagnet I2-whereas when armature I4 has been attracted to touch pole tip I2, that armature will be substantially vertical, lever I will have been moved to its second position (of leftward upward inclination), and armature I3 will have a leftward-upward inclination and will be spaced from pole tip II.

It may be desirable to positively maintain the movable system in either of its two positions until the deliberate movement thereof to the other position by electromagnet actuation. While any means may be employed for this function, there is very appropriate with the illustrated armature arrangement a means similar to that disclosed in the mentioned Langley patent. This may comprise a pair of cams l and lfi, each cam being secured to a respective one of the armatures l3 and I4, somewhat above the point of pivoting of the latter, and extending toward the other armature. The top surface of each cam (e. g., It) may be arcuate about the pivot point (e. g., W) of the armature to which that cam is connected; the outer end surface of each cam (e. g., l5) may also be arcuate and, when thearmature to which that cam is connected is vertical (i. e., in substantial contact with the respective pole tip), that end surface may be in substantial contact with the top surface (e. g., E6) of the opposite cam. It will be obvious that the top of the cam connected with the inclined armature acts as a stopfor the end of the cam connected with the vertical armature, and hence as a lock to maintain the latter armature in its vertical position; this look for the vertical armature, together with the spring I! effective on the inclined armature, positively maintains the movable system in that one of its two positions which it has assumed, until the deliberate movement of the inclined armature. It will further be understood that when the inclined armature (e. g., [4) is subjected to movement toward its vertical position, the respective top cam surface (e. g., It) will slide along the end surface (e. g., I5") of the opposite cam, clearing that endvsurface only when that movement is substantially completed; only upon that clearing will the originally vertical armature (e. g., it) be effectively un locked, whereupon it will execute a follow-up movement to its inclined position under the infiuence of spring 11. In the absence of some constant bias (for example, from the device 4) causingit to follow the first-moved armature, the lever 1 will be moved from its original to its opposite position by the follow-up movement of the originally vertical armature.

A current source 28 is illustrated; one terminal of the source being connected to a control switch S hereinafter described, as through a conductor 2!. The other terminal of the source 20 is connected to the control switch S through the conductor 22, in which the electromagnet assembly is serially connected to be controllably supplied with current; in other words, the conductor 22 may be considered as broken, and the ends produced by the break respectively connected to terminals A and 'B of the electromagnet assembly; First terminals of the respective electromagnets maybe connected together to form the assembly terminal A. The other terminal B of the assembly may comprise the pole of a switch means which is automatically operated by each electromagnet, upon actuation of that electromagnet, to disconnect the conductor 22 from the actuated electromagnet and to connect it to the other electromagnet. Aswitch means to perform .a similar immediate function was disclosed in' the mentioned patent to Langley, to which reference may be had if desired for one typical construction; in the instant case the switch means may be very simply provided by employ ing a portion of the lever l as a switch pole (the terminal B being specifically, for example, formed at the pivoting point I), and by arranging two contacts Iil and 9 to be respectively'contacted by that switch pole when the lever I is respectively in its first and second positions. Contact 9 is electrically connected to the second terminal of electromagnet l i, contact l8 to the second terminal of electromagnet ii. In general, this arrangement may be considered as a means, included in the electromagnet assembly, for alternating the supply of current to the two electromagnets.

Thus with the lever l disposed in its first (illustrated) position, the electromagnet l2 is the one which will be actuated on the next current supply through conductor 22. Upon that supply and actuation the armature It will be sharply accelerated toward pole tip l2, and the lever l and armature i3 willfollow it in manner already described. The lever movement will disconnect the conductor 22 from the electromagnet 2 at contact it), and will connect that conductor to the electromagnet H at contact 9. The electromagnet H has then become the one which will be actuated upon further currentsupply through the conductor 22.

In the mentioned patent to Langley separate conductors were employed to lead actuating current to the respective electromagnets. The con trol switch was a simple single-pole, doublethrow switch which operated to keep voltage continuously supplied to one or the other of these conductors, according to its throw; the switch means automatically operated by the electromagnets was relied on to limit the electromagnet actuations to single, momentary ones. With the instant control system, however, only one conductor is employed forthe actuation of both electromagnets; and it will be obvious that, unless some special measure be taken, operation of'the control switch to keep voltage continuously supplied to the single conductor would result in a sustained oscillation of the movable system back and forth between its two positions. In other words, although the automatically operated switch meansstill functions to limit actuations to momentary ones, it no longer in itself can function to limit the actuations to single ones. 7 r

We may limit the actuations to single ones by employing for the control switch S a switch which in each throw executes only a temporary closure, for an interval which is automatically ended before the lever I has contacted the contact (it) or 9) to which it is being thrown by that closure. Such a switch has been schematically illustrated in Figure 1. It may comprise simply a switch pole 3| pivoted as at point 3i, throwable back and forth in an are (for example below point 3|) between two stationary stop members 33, and passing over and contacting a stationary contact 30 in each of its throws. The switch pole 31 is thrown in a uniform manner by a toggle arrangement comprising an arm 35 pivoted for example at the same point 31' but extending therefrom to be thrown in a somewhat larger arc, on the opposite side of (e. g., above) point 3|, between stationary stop members 36; pole 3! may be toggled to arm 35 as by spring 34 tensioned between pins Sla and 35a extending forwardly from intermediate points on pole and arm, respectively. Arm 35 may be thrown directly or in any convenient manner. By way of example there has been shown a rod 31 pivotally secured to the arm and passing leftwardly therefrom through an aperture 38' in panel 38, to terminate in a knob 40 which may be pushed and pulled toward and away from the panel to throw the arm; the arm may be subjected only to the bias of the toggle spring 34 urging it to retain each of its two positions, or if desired may be biased into a predetermined one of those positions by a sufficiently strong spring 39. However it is chosen to throw arm 35, it will be understood that as the arm, in a leftward throw from its illustrated or first position of contact with the rear stop member 35, closely approaches the front stop member 36, the spring 34 will pass across the pivoting point 3! and will thereupon cause the forward throw of pole 3|, with momentary closure of that pole against contact 39. A converse but entirely analogous action takes place on rightward throw of arm 35. The duration of the contact of 3| with 33, or interval of control switch closure, on each throw may be predetermined at desired value by apportionment of the length of the contact 30 in the direction of the throw, the tension of spring 34, and the effective mass of pole 3lthe latter being regulable as by suitable weighting of its extremity, indicated as 32.

The control switch S as so described may be connected to by the conductor 2| at 30; and by the conductor 22 at 3|, through the schematically indicated switch 23 which at the moment may be taken as closed to short-circuit and functionally eliminate the elements shown above the arm 35. Its function may be considered to be the supply to the electromagnet assembly of current pulsations, each pulsation for a single actuation of one of the electromagnets and consequent single throw or movement of th movable system; and under theoretically perfect conditions the control switch and movable system will remain in step, or predetermined positional relationship, with each other. Possibilities exist, however, of various influences occasionally causing an abnormally long switch closure, with double or other multiple electromagnet actuation; and for many purposes there cannot be tolerated even the small degree of independability which these possibilities entail. It'is also of course possible in very exceptional cases that a closure of the control switch will be deficient to such a degree that no electromagnet actuation takes place thereon, a reversal of proper relationship thus being caused; or, again, that a reversal may have been effected by some ill-advised, purely mechanical manipulation of one of the parts.

Our invention accordingly contemplates a plurality of arrangements for constraining the electrcmagnet assembly to move the movable system in'predetermined directional relationship to the movement of the control switch. or constrairn ing the movable system to a predetermined positional relationship with the switch. Thus a function of each arrangement is to automatically restore the system and switch, if at any time they are out of step, into step. Two of these arrangements are incorporated in the control of Figure 1; each operates on the throw of the control switch in one of its directions to prevent the operation of that electromagnet whose operation on that throw is improper. Each involves a differentiation between the current pulsations or currents respectively supplied on the two throws of the control switch; this differentiation may be simply a differentiation of the Voltages at which the currents are supplied, effected for example by the selective inclusion in circuit of a resistance. When such a resistance is employed it is usually most conveniently provided in physical adjacency to the switch S; but wherever physically located it, or whatever difierentiating means is employed, may be considered as forming a part of the control means.

To associate a resistance with the control switch S so that it functions to limit the voltage on one but not on the other throw, we may expand the control switch to a form such as described and claimed in the co-pending application of the present co-applicant Richard M. Somers, Serial No. 252,523, filed January 24, 1939. Typically this may be done by employing the abovementioned arm 35 as a switch pole, with a contact button 35a carried in its right-angularly twisted upper end portion 35b; and by arranging two contact springs 4| and 42, with respective contact points Ma and 42a, adapted to be contacted by the arm (e. g., by button 35a) when the arm is respectively in its first and second posi tions. Conductor 22 may be connected to spring 41 directly, and to spring 42 through the resistance 25 bridged between the springs; arm is of course electrically connected to pole 3!, as at the common pivot point 3 i The schematically illustrated switch 23 will of course be kept open to render the springs 4| and 42 and arm 35 effective to control the connection of conductor 22 with pole 3|.

The springs are arranged so that as arm 35 is moved toward either spring, that spring will be contacted by the arm materially before the arm reaches the extremity of its movement in that direction, the spring flexing as that movement is completed. Accordingly as the arm 35 is moved leitwardly from. its first (illustrated) position to its second position, it will quit contact with spring 4! and make contact with spring 42, and only after the contact with spring 42 is established will the arm cause the forward throw of the pole 31; thus in this throw of the control switch conductor 22 is supplied with a current pulsation from conductor 2! through the voltage-limiting resistance 25. Conversely, as the arm 35 is moved from its second position to its first position, it will quit contact with spring 42 and make contact with spring 4 I, and only after the latter contact is made will the arm cause the rearward throw of pole 3 I; thus in this throw of the control switch the conductor 22 is supplied with a cu"- rent pulsation free of voltage limitation by the resistance 25.

One of the constraining arrangements incorporated in Figure l is a means associated with the electromagnet |2-which is the electromagnet intendedly actuated, to throw the movable systern to its second position, by the limited-voltage current supplied on throw of the control switch S to its second positiontor preventing its operation of throwing the movable system to second position when full-voltage current is supplied to it. While there may be employed any or" a variety of means for preventing the electromagnet operation under these conditions, we have illustrated a means which, though it permits the actuation of the electromagnet (i. e., its energization in sufficient degree to move its armature, in the absence of abnormal armature restraint), renders that actuation ineffective by blocking the response of the movable system thereto. In turn, while the means for blocking the response of the movable system may be associated with that systern in any of a variety of manners, we have illustrated it as a means which immediately influences the armature l4.

Thus at the end of the electromagnet i2 opposite to its armature end there may be provided a catch member having a top extremity pivoted as atpoint 58, extending generally downwardly therefrom past the pole tip [2" at this end of the electromagnet to below the electromagnet, and having a small lug portion 50a formed rightwardly from its lower extremity. The catch member 50 may be of very light material and structure, but opposite the pole tip i2" it may carry a small armature 5! of ma netic material adapted for attraction by that pole tip. The catch member 56 may be biased leftwardly against a stop member 52 as by a tension spring 53; when the catch member is in its rest position of contact with this stop member, the armature 5! may be slightly spaced from the pole tip l2". Rigidly secured to armature M and extending therefrom leftwardly underneath the electromagnet I2 is an arm 55. This arm is of such length that as the armature M is rocked when the catch member 50 is in rest position, the

left-hand arm extremity will just clear the lug portion 58a. The bottom of the arm extremity may be spacedly above the level of the top of lug portion 58a when the armature I4 is rightwardly inclined (as illustrated), but may move to slightly below that level as the armature M is attracted into contact with pole tip l2.

The spring 53 is made just dependably strong enough to prevent the attraction of the catch member 50 by the electromagnet l2 when the latter is actuated by the limited-voltage current supplied upon throw of the control switch to its second position; accordingly the then-intended throwing of the movable system to its second po-' sition is not interferred with. Should the fullvoltage current be supplied to the electromagnet l2, however-either by reason of the apparatus having previously gotten out of step, or by reason of a closure of the control switch S, on its throw to first position, continuing until after the throw of the movable system-the armature 5i will be attracted to the pole tip l2", and the lug portion 50a of the catch member will be brought under the extremity of the arm 55. In view of the spacing factors detailed above, the lug portion 58a will prevent at least the final small portion of downward movement of arm 55 and leftward. movement of armature M; and since the cams l5 and 56 act to prevent movement of the vertical armature until that of the inclined armature is substantially completed, the armature 83 will be maintained stationary no matter how long the full-voltage current supply may continue. At the termination of that supply, the springs ii and 53 will of course cause the armature i3 and the catch member to resume their illustrated positions, the operation of the electromagnet I2 to throw the movable system having been thus prevented.

It will be understood that the catch member Ell, which is not movable by the limited-voltage current supply to electromagnet l2, must by the full-voltage current supply to that electromagnet be moved so rapidly that its lug portion 5130. dependably moves into the path of the end portion of arm 55 before the armature l4 movement is completed-this in spite of the fact that the l armature t l, since it mustbe dependably movable by the limited-voltage current supply to electromagnet l2, will be quite rapidly accelerated by the full-voltage current supply. The

very small effective mass of the catch member 59 relative to the large efiective mass of the armature M with arm 55 is, however, sufficient to insure the proper action, particularly since advantage is taken of the ability to block the movement of the movable system by blocking only a small terminal portion of the armature Hi movement-an ability arising from the action of the cams l5 and I6. It may be noted that if the device 4 tends to impart any bias to the lever I, toward one or the other armature, it is desirable that it be toward the armature (e. g., l3) opposite to that with which a preventing structure of the particular type illustrated is associated. The constraining arrangement so described prevents operation of one of the electromagnets (e. g., l2, intended to be actuated by the limitedvoltage current) by the current (e. g., of full voltage) not intended for that electromagnet; it accordingly permits any continued length of control switch closure in the throw intended to actuate the other electromagnet (e. g., H); and it restores to normal the positional relationship between the movable system and the control switch, if that has by any mishap been reversed, either upon the first control switch closure succeeding the reversal (if immediately succeeding the reversal electromagnet I2 is prepared for actuation) or upon the second control switch closure succeeding the reversal (if immediately succeeding the reversal electromagnet H is prepared for actuation)-in any event withinone cycle of operation of the control switch. 7

The other constraining arrangement incorporated in Figure 1 also depends upon difierentiation between the alternate current supplies, as by the means already described, but does not involve the use of the catch member 50, arm 55 etc. of the first arrangement; it may be considered initially with the latter elements omitted from the control. Its ultimate functions, are analogous but converse to those set forth, for the first-described arrangement, in the last preceding paragraph-that paragraph applying literally to the second arrangement if read with electromagnet H substituted for electromagnet i2 and vice versa, and with full-voltage current substituted for limited-voltage current and vice versa. The second arrangement consists simply in the arrangement of electromagnet l I so that it is actuable only by current at a voltage substantially exceeding the limited voltage abovementioned-e. g., is actuable by the full-voltage current--while electromagnet l2 remains actuable (i. e., capable of being energized in sufficient degree to move its armature) by either the fullvoltage or limited-voltage current. Purely as an example of a means for rendering the electromagnet l I actuable only as stated, there has been illustrated in series with it in the electromagnet assembly a resistance H); but it will be understood that the means may consist in any element or elements in or associated with the electromagnet, such as the electromagnet coil itself (l 50), then wound for inefiectiveness when supplied with current at only the limited voltage.

The performance of the ultimate functions abovementioned will be understood to follow inherently from the ineffectiveness of the supply to electromagnet H of the limited-voltage current. In general, it may be said that this constraining arrangement operates electrically and, in distinction thereto, that the first-described one operates mechanically.

While either of these constraining arrangements may be employed without the other, for the benefits already made apparent, we prefer to employ them in combination with each other. Such a combination prevents operation of each of the electromagnets by the current at a voltage respectively not intended for that electromagnet; it accordingly permits any continued length of control switch closure in each of the two throws of that switch, so that the apparatus may be considered to be effectively maintained, rather than merely constrained, in step. And in the highly exceptional case of failure of switch closure on switch throw, or of mechanically effected reversal of the proper relationship, the combination restores the proper relationship between control switch and movable system upon the very first control switch closure following the reversal, so that its residual constraining function is especially efficiently performed.

It will of course be understood that while the duration of each current pulsation need no longer be limited for the purpose of avoiding multiple electromagnet actuation, it is generally desirable that the current supply shall still take place in the form of pulsations as distinguished from indefinitely continued supplies, for the avoidance of unnecessary and wasteful continued current fiow, overheating of the electromagnets, etc. The system may if desired, however, be operated with spring 34 removed and switch pole 3| left in contact with contact (the first and second positions of the arm and knob 48 in such a case becoming the opposites of those above described). It is therefore to be understood that we do not intend to limit all aspects of our invention to the supply by the control switch of momentary currents.

In Figure 2 we illustrate a modification of the electromagnet assembly (operable for example with a control switch S similar to that illustrated and described for Figure 1), in which the second constraining arrangement above described may again be employed; but with it there is employed, instead of the first constraining arrangement, a modified arrangement with a somewhat different immediate function. As will hereinafter be apparent, this in itself functions to avoid multiple electromagnet actuation on the supply of current to one of the electromagnets by retarding the completion of operation of that electromagnet; employed, as illustrated, in connection with the second constraining arrangement, it provides a composite system whose overall function is almost identical with that of Figure 1. The changes in the electromagnet assembly lie in the omission of the catch member 59, arm etc. from association with electromagnet l2; and in the association with electromagnet H (that actuable only by the larger current) of a somewhat analogous structurebut with the arm therein still associated with the same armature as in Figure 1, which is to say armature M for the electromagnet l2 actuable by the current at either voltage.

Thus at the end of the electromagnet H opposite to its armature end there may be provided a catch member 69, having a bottom extremity pivoted as at point extending generally upwardly therefrom past the pole tip I I at this end of the electromagnet to above the electromagnet, and having a small lug portion 60a formed leftwardly from its upper extremity. The

catch member 60 may be of very light material and structure, but opposite the pole tip II" it may carry a small armature 6| of magnetic material adapted for attraction by the pole tip. The catch member 60 may be biased rightwardly against a stop member 62 as by a tension spring 63; when the catch member is in its rest position of contact with this stop member, the armature 6| may be slightly spaced from the pole tip ll Rigidly secured to the top of armature I4, and extending therefrom rightwardly above the armature I3 and the electromagnet H, is an arm 65. This arm is of such length that as the armature M is rocked when the catch member 60 is in rest position, the righthand extremity of the arm will just clear the lug portion 60a. The bottom of the arm extremity may be slightly spaced above the level of the top of lug portion 60a when the armature I4 is vertical (as it has been illustrated in this figure), but may move to below that level as the armature l4 executes a follow-up movement rightwardly after attraction of armature l3 into contact with pole tip H on actuation of the electromagnet H.

Whenever the electromagnet H is actuated, the catch member 60 will be attracted leftwardly by pole tip II", and lug portion 6041 will come into the downward path which the extremity of arm 65 has to traverse during the follow-up movement of armature l4. All but a very small initial portion of that follow-up movement is accordingly prevented so long as the current supply through conductor 22 continues; with it there is correspondingly prevented any significan movement of the lever l and movable systern (any bias of the upper portion of lever I, as by the device 4, now being preferably a leftward one). It will be understood that the slight ini tial movement of armature l4 which is permitted serves to permit the top surface of cam I 6 to get underneath the end surface of cam l5, so that when the current supply ceases and catch member 69 is withdrawn rightwardly, the followup movement of armature M will dependably occur. It will also be understood that, by virtue of cams l5 and I6, no movement of the arm M will tend to occur upon actuation of the electromagnet H until after the movement of arm l3 has been substantially completed; thus there is an especially wide safety margin of time interval in which the light catch member Bil may be attracted into its interfering position.

There may be reviewed the action of the control of Figure 2 under conditions of current supplies from the control switch not themselves sufficiently short to avoid multiple electromagnet actuation. The operation of the catch 8!) prevents multiple electromagnet operation upon the intended supply to electromagnet H of the fullvoltage current-by preventing the transfer of current supply to the electromagnet l2 at contact 10 so long as the supply continues. The ineffectiveness of the limited-voltage current on electromagnet H of course prevents multiple operation on the intended supply to electromagnet I2 of that current; it also of course prevents any operation at all on an unintended supply to electromagnet ll of that current, so restoring the movable system to step with the control means as it did under similar conditions in the control of Figure 1. In the one case of an unintended supply to electromagnet 12 of the full-voltage current can a multiple operation occurand that multiple operation will be limited to a double one, also effective to restore the movable system to step with the control means. And of course if the current supply from the control means is sufiiciently short to avoid multiple operation,

any out-of-step condition will be automatically rectified on the first supply to electromagnet ll of the limited-voltage current-necessarily within the first cycle of control switch operation following the displacement from normal relationship.

It will be understood that while we have shown and described our invention in terms of two particular embodiments thereof, these embodiments are presented in an illustrative rather than in a limiting sense. Thus for example the electromagnetic assembly may comprise any of a variety of forms of electromagnetic devices or the control means may comprise switch means of any of a variety of forms, adapted to perform functions analogous to those above indicated as expected of those respective elements. Modifications in these or other respects from the details of the illustrated embodiments will readily suggest themselves to those skilled in the art, and will not necessarily constitute departures from the true spirit and proper scope of the invention.

We claim:

1. In an electrical control system including means operable to supply currents at two difierent voltages through a common conductor: the combination of an electromagnetic assembly supplied with said currents, said assembly comprising a pair of electromagnetic devices and means for alternating the supply of current thereto; a movable system electromagnetically operated between respective positions by said devices; and means, comprised in said assembly, for rendering each of said devices ineffective to operate said system when supplied with current at a respective one of said two voltages.

2. In an electrical control system including means operable to supply currents at two different voltages through a common conductor: the combination of an electromagnetic assembly supplied with said currents, said assembly comprising a pair of electromagnetic devices and means for alternating the supply of current thereto; a system movable by said devices; and means, Operated by one of said devices when current at a predetermined one of said voltages is supplied thereto, for blocking the movement of said systern by that device.

3. In an electrical control system including means operable to supply currents at two different voltages through a common conductor: the combination of an electromagnetic assembly supplied with said currents, said assembly comprising an electromagnetic device actuable by current at the larger only of said voltages, an electromagnetic device actuable by current at either of said voltages, and means operated by said devices for alternating the supply of current thereto; a movable system operated by said devices; and means, comprised in said assembly, for preventing operation of said second-mentioned device by the supply of said larger-voltage current continued after actuation of said first-mentioned device.

4. In an electrical control system including means operable to supply currents at two different voltages through a common conductor: the combination of an electromagnetic assembly supplied with said currents, said assembly comprising an electromagnetic device actuable by current at the larger only of said voltages, an electromagnetic device actuable by current at either of said voltages, and means operated by said devices for alternating the supply of current thereto; a movable system operated by said devices; and means, comprised in said assembly and rendered effective throughout the supply of said larger-voltage current to said first-mentioned device, for preventing the transfer of current supply to said second-mentioned device.

' 5. In an electrical control system including means operable to supply currents at two difierent voltages through a common conductor: the combination of an electromagnetic assembly supplied with said currents, said assembly comprising an electromagnetic device actuable by current at the larger only of said voltages and an electromagnetic device actuable by current at either of said voltagesya movable system electromagnetically operated between respective positions by said devices; and means, associated with said second-mentioned device, for preventing the operation of said system thereby upon actuation of that device with said larger-voltage current.

6. The combination according to claim 5, wherein said assembly further comprises means operated by the devices for alternating the supply of current to said two devices.

'7. In an electrical control system including means operable to supply currents at two different voltages through a common conductor: the combination of an electromagnetic assembly supplied with said currents, said assembly comprising a pair of electromagnetic devices; a movable system electromagnetically operated between respective positions by said devices; means for electrically rendering one of said devices ineirective to operate said system upon supply to that device of current at one of said voltages; and means for mechanically rendering the other of said devices ineffective to operate said system upon the supply to that device of current at the other of said voltages. V

8. The combination according to claim 7, wherein said assembly further comprises means operated by the devices for alternating the supply of current to said two devices.

9. In an electrical control system including means operable to supply currents at two different voltages through a common conductor: the combination of an electromagnetic assembly supplied with said currents, said assembly comprising a pair of electromagnetic devices; a movable system electromagnetically moved between respective positions by said devices; and means, comprised in said assembly, for causing each of said devices to operate said system only in response to current at a respective one of said two voltages.

10. The combination according to claim 9, wherein said assembly further comprises means operated by the devices for alternating the supply of current to said two devices.

11. In an electrical control system including control means throwable between two positions to supply on its respective throws currents at two different voltages through a common conductor: the combination of an electromagnetic assembly supplied with said currents; a movable system electromagnetically moved in respective directions between two positions by said assembly; and means, comprising voltage-controlled means in said assembly, for constraining said assembiy to move said system in predetermined directional relationship to the movement of said control means.

12. The combination according to claim 11, wherein said assembly comprises a pair of electromagnetic devices and means operated by the devices for alternating the supply of current thereto.

13. In an electrical control system including control means throwable between two positions to supply on its respective throws currents at two difierent voltages through a common conductor: the combination of an electromagnetic assembly supplied with said currents; amovablesystem electromagnetically moved inrespective directions between two positions by said assembly; and means, including voltage-controlled means in said assembly, and rendered effective upon an operation of said control means following any departure of said system from predetermined positional relationship with said control means, for restoring said system to that predetermined relationship.

14. The combination according to claim 13, wherein said assembly comprises a pair of electromagnetic devices and means operated by the devices for alternating the supply of current thereto.

15. In an electrical controlsystem including means operable to supply currents at two different voltages: the combination of an electromagnetic device supplied with said currents; a movable system electromagnetically moved by said device upon the supply to said device of current at the smaller of said voltages; and movable means, moved by said device upon the supply to said device of current at the larger only of said voltages, for interfering with the movement of said system by said device upon said supply of larger-voltage current.

16. In an electrical control system including means operable to supply currents at two difierent voltages: the combination of an electromagnetic device supplied with said currents; a system electromagnetically moved by said device upon the supply to said device of current at the smaller of said voltages; and means, associated with said device and rendered effective by the supply to said device of current at the larger only of said voltages, for rendering said device ineffective to move said system upon said supply of larger-voltage current.

17. In an electrical control system including means operable to supply currents at two different voltages: the combination of an electromagnetic device supplied with said currents; an armature subjected to movement by said device upon the supply to said device of current at the smaller of said voltages; a movable system mechanically moved by, but only at the substantial completion of, said armature movement; and means, associated with said device and rendered efiective by the supply to said device of current at the larger only of said voltages, for blocking the terminal portion of said armature movement, whereby to prevent movement of said movable system upon said larger-voltage current supply.

18. In an electrical control system including means operable to supply currents at two different voltages: the combination of an electromagnetic device supplied with said currents; an armature subjected to movement by said device upon the supply to said device of current at the smaller of said voltages; a movable system mechanically moved by, but only at the substantial completion of, said armature movement; and a member of small effective mass relative to that of said armature, arranged for movement by said device upon the supply of current thereto but biased against movement upon said smallervoltage current supply, moved upon said largervoltage current supply into position interfering with said armature movement.

' RICHARD M. SOMERS.

CHARLES '1". JACOBS.

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