US1474094A - Switch drum for starting and controlling electromotors - Google Patents

Description

.Nbv. 13,1923

L. sci-16M I SWITCH DRUM FOR STARTING AND CONTROLLING ELECTROMOTORS Filed Sent. 26, 1922 Patented Nov. 13, 1923.

UNITED STATES 1,474,094 PATENT OFFICE.

LUDWIG soHoN, or

ESSEN, GERMANY, ASSIGNOR TO FRIED. KRUPP AK'IIENGESELL- SCHAFT, 0F ESS EN-ON-TI-IE-RUHB, GERMANY.

SWITCH DRUM FOR STARTING AND CONTROLLING ELECTROMOTORS.

Application filed September 26, 1922. Serial No. 590,710.

[0 aZZ whom if; may concern:

Be it known that I, Loo'wre SoHoN, residing at Essen. Germany, a citizen of the German Republic, have invented a certain new and useful Improvement in,Switch Drums for Starting and Controlling Electromotors, of which the following is a specification.

This invention relates to improvements in switch drums for starting and controlling electromotors and has for its object to provide the switch drum with a device by means of which the drum can be locked in such a manner that an abnormally rapid return of the drum to a lower switch step is rendered impossible and that any inadmissibly high stress on the contacts designed to close or break the motor circuit is securely avoided.

The subject matter of the invention is of particular importance in connection with switch drums of the kind in which the motor circuit is not interrupted at the contact members of the switch drum itself but at an auxiliary electromagnetic cut-out situated outside the switchdrum. This means that the device according to the invention is likewise adapted for use in cases in which it is held desirable to lock the drum also in the driving positions or solely in the same. while without the use of such an auxiliary cut-out the switch drum can only be locked in its braking positions.

The accompanying drawing diagrammati-- cally illustrates, as an embodiment of the subject matter of the invention in connection with the wiring diagram of a D. C. t *amcar motor, a controller which cooperates with an auxiliary electromagnetic cut-out serving to interrupt the motor circuit and which is automatically locked as long as the motor current exceeds a predetermined maximum value.

Referring now to the drawing. A designates the overhead line which is connected to the positive pole ot a source of direct current and to which is connected by means of a trolley 13 a line C leading to the ground (negative pole). Placed in the line C so as to be connected in series with one another and with the switch drum K when the latter is in its driving positions, are: the releasing coil. and the two break forming contact pointsd and d of a circuit-breaker D provided for protection of the plant against overload, a multi-step starting resistance E, the winding f of a magnet F that will still be further described, the two break forming contact pointsg and g of the auxiliary electromagnetic cut-out G as well as the armature H and the exciting winding H of the D. 0. motor to be controlled The overload circuit-breaker D contains, in addition, another magnet coil d which acts on the same magnet core as the main current releasing coil (Z and which is wound in the same direction as the last mentioned coil. The magnet coil (F is connected in parallel to the break (Z (Z and is of a strength such as to be able to hold the opened circuit-breaker D in its cut-out position contrary to the action of a spring coil 6Z constitutes therefore axholding coil. The auxiliary cut-out G possesses only one magnet coil which is connected, on the one hand, to the contact point 9 of the cut-out G and. on the other hand, to the outset of the first step of the starting resistance E. Interposed between the coil 9 and the contact point 9 is aresistance J by which any short-circuit is rendered impossible when the auxiliary cut-out G is osed. The magnet coil is proportioned so that it will be able to overcome the force ot a spring 9 counteracting the coil and open the cut-out Gr only in case itis put into direct COHTflGClIlOn with the full voltage of the source of direct current. This is rendered possible by the intermediary of an auxiliary switch device which forms partc:! the controller and will therefore be de scribed in connection with the same.

The controller cooperating with the starting resistance consists oi? a switch drum K provided i *ith contact bars and ot a regulating lever K which constitutes the driving means for the drum and which is rotatable round the axis oi the switch drum for a slight angle with. relation to the switch drum. l1} the drawing, the contact bars de signed to start and control the motor H H are mnittcd from the lower portion of the switch drum lit the terminals of the corresponding wipers are indicated by small cir cles 11 at which terminates the connecting tires leading to the starting rcsistance'E,

the motor H H and the poles ol. the source of direct current. The regulating lever K is mounted for tree rotation on the upper end taco Z1 or the switch drum K by means of a pin 7 so as to he aljile to more with relation to the switch drum between two stops and a which are likewise arranged on the end taco a at a small distance. The end face 71 ot the switch drum K :turth e r carries a one-armed lever which is proi'ided with a projection l1 adapted to en 'age a notch 7v oi the regulating: lcrer lll'ltltl the in'lluencc ot a spring if. \Vhei the i'egailatinn lever K is not handled, it forced by t he engagement oi? the project on 76' with the notch Z to take a position midway hetween the two stops 70' and Z The regulating lever K possesses at its rear end an extension enlarged so as to Form a sector 70 of :1 radius somewhat. larger than that. of the switch drum Kand having ttastened to its edge. in the. manner to he seen from the drawing, a metal rod 7x extemlino' parallel with relation to the axis of the switch drum. The rod 70 constitutes a contact member which serves to cm'iduct ely connect, in the limit positions ot the regulating lever K determinec by, the stops 70* and 70 two oi" three slightly resilient contact members Z7. Z1 and 77 each otwhich is arrange on one of three contact bars 70" to which are riveted in parallel. radial planes to the switch drum K. The uppermost; contact har 7'1 embraces approximately one halt and. the lowermost one 7d the other halt of the circumtercnce ot the switch drum. while the intermediate bar l embraces nearly the entire circumference. The cooperating wipers 7a to 7r are arranged at a stationary por-- tion of the contr llcr casing in a manner such as to hear against a part of the switch drum not covered hy the contact h rs when the switch drum K is in the position shown, in which. it takes its Zero position with relation to the casino; (not shown). The intermediate contact memher 7r oi the three contact memhers 70 to if is COllSi't'llClT-il and arranged so as to he touched by the rod 7r in each of the two limit positions oi the. reg"- ulating lever K. while the two other con tact memhcrs Z1 and are arranged so as to cause the rod Z? to engage the contact meinhcr oi" the uppermost contact bar 7c when the regulating lever touches the stop N. and to engage the contact memher Z of the lowermost contact bar I? when the regulating lerer touches the stop If. On account of the descrihed arrangement oi the contact hairs Z to 7r". the intern'lcdiate contact har Ki will he in enminementwith the correspond- .in; wiper 7' in all operative positions ol the switch drum K except for the zero-position. while the uppermost contact har i113 hetwcen the releasing coil /j" of the. auxiliary cut-out (:t and the series resistance .l. while the wiper is grounded through a line As will he re ilf. seen 'l'rom the drawin". the described :-1 witch connections will cause the magnet coil r to he put under the volt age of the direct current source every time. the regulating lever K will he returned 'lrom any one o! its ()llQl'tllQlYfl positions towards the zero-position, o l the switch drum K. so that now. in the driving positions ol' the switchv drum. the i of contact" memhers Z9 1 r and in the hralcin; positions the pair oi contact members if. l will he hride'cd hr the. metal rod a.

The switch drum K carries at its upper end a ring-rtector-shapeil extension Z? the margin of which is provided with a series o'l teeth 7c corres ionding in number to the number of driving. steps. The margin of the sector-shaped rearward extension 70 0'! the regulating lever k is likewise provided with teeth 0 which, however, are arranged more closely to each other than the teeth Zr and are directed oppositely to the latter. The toothed portions 7: and Xi thus form parts oi two oppositely directed locking mechanisms which act each in one single direction and the cooperating parts oi which are tor-med by two pawls P and Q influenced by the magnet F 7. already mentioned. The pawl P is pivotally and resiliently connected to one arm P of a wrought iron hell crank lever P P which mounted on the casing of the controller K K and the other arm P of which has a thickened end 22" facing one ot the end Faces ot' the magnet core F. The. pawl Q which is directed oppositely and mounted tor swinging motion in a plane parallel to the pawl P is similarly pivoted to one arm (Q of another hell crank lerer Q Q the other arm Q of which has its thickened end of facing the other end face oi. the magnet core F. The two thickened ends 7) and 7 form armatures ot the magnet l i'\ compression spring-1' R engaging hoth the le- Vcr arms P and Q tends to hold the ends p and apart from the end faces of the ma"- net 1*. The stroke oi the two lever arms and Q pressed outwards hy the spring R, is limited by two fixed stops P" and Q? in such a position that the pawls P and Q are out of en jag'emcnt with the corresponding teeth 70? and 70 The magnetic conditionsht the douhle looking (lOVicO l 7. P 0, Q 70 are proportioned. so that. in case the strength oi the motor current flowing avens;

tation of the regulating lever K and the switch drum K, either one or the other of the two single acting locking devices P k and Q will cause a locking of the controller K K A locking of the controller can therefore takeplace in the driving positions as well as in the braking positions of the switch drum. Both locking devices will, however, become inoperative as soon as the motor current drops below the determined maximum value or the motor circuit is interrupted. In this case, the controller is free to be rotated in both directions of rotation.

With the end of describing the operation of the device set forth, it is assumed that all parts take the position illustrated in the drawing in which, more particularly, the regulating lever K of the controller K K takes the position in the middle between the stops k and 70 and the switch drum K is in its zero-position, so that the motor circuit and the circuit of the auxiliary switch device containing the contact members 70 to 70 is interrupted at the switch drum and the magnet coils cl, g and f are currentless. The cut-outs I) and G are therefore closed and the two locking devices P 70 and Q, is are inoperative. r

If the motor H H should be started, the controller K K has to be brought first intothe position corresponding to the first driving step, this being effected by rotating the regulating lever K in the direction of the arrow m. This movement will cause the projection 70 to be disengaged from the notch k and the regulating lever K to become engaged with the stop 70 while the switch drum is still. at rest. In this position, the metal rod 70 will establish a conductive connection between the contact members k and 7:" and, consequently, between the contact bars 76 and 70 but the circuit con taining the contact members 7.1 to is will still remain broken at the wipers 70 to 7.1 In continuing the rotation of the regulating lever theswitch drum K will likewise be moved in the direction of the arrow m and the motor circuit will close now in a wellknown manner through the resistance steps oi the starting resistance E and the wipers indicated by the terminals Z! as well as through the main current contact bars (not shown) ot' the switch drum K. At the same lllll'lG lllfle wipers 7c and 70 will enter into touch with the corresponding contact bars 70 and 7' of the auxiliary switch device, while a contact between the wiper k and the contact bark does not take place owing to the peculiar construction of this contact bar. Therefore, no circuit will as yet be closed through the contact members is. i

70 and the rod k, and the lineslVI, N will even remain currentless when the SWl ECh drunr further rotated n the direction ot a direction opposite to the arrow 0:, the

switch drum K will at first remain at rest and the metal rod 70 will come into touch with the contact members 7c and 70 will cause the circuit-l-A. B C (Z (Z (Z M 70 70 72 k 72 is N C-to be closed so that the magnet coil 9 will be under the full voltage and open the auxiliary cutout G. However, a certain although short time, known as switch-lag, will pass between the moment the said circuit is; closed and the moment at which the break of the motor circuit is terminated, this lag being due to the mechanical inertia of the cut-out G, the magnetic inertia of its magnet coil 9'' and the inductive resistances existing in the main circuit. According to experience, this switch-lag is mostly considerably longer than the time that is necessary, in switching by jerks, for moving the controller into the position corresponding to the next lower switch step. In order to prevent injurious arc-forniations at the main current contact members of the controller, provision has therefore to be made for allowing a returning of the switch drum K from a higher to a lower switch step only after the motor current has disappeared or at' least not sooner than the motor current has dropped below the predetermined maximum value. This is automatically obtained by the in termediary of the electromagnetic locking device F 7, P P 72 For as long as the current flowing through the coil 7 still exceeds the admissible maximum value, the

This

magnet armature p as well asthe magnet armature are attracted and. the pawl P is held in engagement with the teeth 0 so that a rotation of the switch drum opposite to the direction of the arrow :20, that is, to wards its zero-position, is rendered .nnpossible. As Wlll. be evldent from what has been said, a further movement of the switch drum K in the said direction can. only take place when thestrength of current in the motoucircuit has dropped below the said maximum value. soon as this takes place, the power of the spring R will overcome that of the magnet F 7 so that; the pawl P again placed out oi engagement with the teeth la In the said positions of l the switch drum the likewise attracted magnet armature 9* does not execute any locking action, since the teeth Z1 are not in reach of the pawl The described device will operate entirely similarly when using the controllerK K- for braking electrically, in which case the motor-If! H operates as generator on the starting resistance It througl'l the auxiliar cut-out G and the magnet coil f. It the controller should be returned from a position which corresponds to a strong braking, lo a lower braking step, the regulating lever K which had been moved. opposite to the direction of the arrow rotor instituting the braking llltlOll, must be turned back in the direction o'l the arrow rt'.-- This movement is. however, automatically rendered. impossible by the locking device F fl, Q (2?, X1 until the motor current has dropped below the predeterulined inaxin'iuni value. As. long as the motor current: still exceeds this maximum value the force of the magnet 1 f overcomes that of the spring R and the armature j renniins attracted and the pawl. Q? engaged with the, teeth As long as the locking device ll 7, Q 71: Opera'- tive, the narrow pitch chosen -for the teeth Z7 will not allow the regulating lever K to approach to the stop to such an extent that the rod 70 will abut against the contact members 0 h and thus close the circuit containing the contact members Z1 to is.

The re ulatin lever K may. at the most C R) o I 3 move with relation to the pawl Q by a fraction of the pitch of the teeth Z11 it the pawl Q is not just opposite to a tooth space. The controller is therefore forced to remain in the switch step once set untilthe braking current has dropped below the predetermined maximum value. ills soon as this occurs, the magnet F 7 will release the armature and the pawl Q will again come out of engagement with the teeth Z0 under the influence of the spring The main advantage of the described device resides in the :tact that an abnormally rapid returning ot the controller is rendered impossible in driving as well as in braking, thereby securely avoiding onerous and injurious arc-formations at the main current contact members of the switch drum and at the auxiliary cutout Gr. A special advantage of the described locking device resides in the fact that the driver, when properly handling the controller, does not at all become aware of the locking device which will only enter into action when the switching operations are executed at an improperly high speed.

Without changing the spirit ot the invention, one ot the locking devices, such as P M, may be omitted and one may restrict oneself to protect the controller K K and the auxiliary cutout against arc-'lm'mation only in braking electrically. In this case. for example, it it is intended to lock the controller electromagnetically inthe braking positions but not in the driving positions, the auxiliary cutout G r might also be dispensed with and the regulating lever K rigidly coupled with "the switch drum K.

Hmvever the use ofa double locking device 11 i'moei and ol? the auxiliary cut-out alliord the guarantee thatcven the slightest iiriulrious arc formation is kept away from the. Controller.

If the controller should not he used at all or only exceptionally for electrical braldngthe electric connections can be changeih without departing from the nature ot the invention in. such a manner that the auxiliary cutout G' is only made use o'l in driving and not in braking. In this case, one oi the threev contact bars of the auxiliary switch device at the switch drum and the corresponding wiper can be dispensed with. This embodiment atlords the further advan tage that the overload circuit breaker D can then be used as auxiliary cut-out instead oi". the auxiliary cut-out G, this being rendered possible by connecting the holding coil (Z o l the breaker D with the auxiliary cut-out in such a manner that it may serve at the same time as releasing coil.

Finally, it must be remarked that the magnet coil f can also become currentless by releasing the main current coil (Z ot the overload circuitbreaker D. In such case. however the driver can restore the main circuit only when he has returned the controller into its zero-position and thus broken the main circuit also at the switch drum. thereby making the holding coil d currentless. The motor and the controller are thus protected from injuries by abnormal strengths of current.

Claims:

1. The combination with a switch drum for starting and controlling motors, comprising a driving member for said drum. ol a single acting magnetic locking device tor preventing said driving member from return movement, said device being kept in its loch-- ing position by the armature current of the. motor to be controlled when exceeding a predetermined value. said locking devi -e comprising magnet to be energized by said armature current and two cooperative elements, one of these elements being termed by said driving member and the other elementbeing placed under the influence ol said magnet.

2. The combination with a switch drum for starting and controlling motors comprising a. regulating lever mounted to rotate freely with relation to the switch drum for a small angle and an auxiliary switch device adapted to actuate a cut-out arranged in the motor circuit at a point outside the controller upon returning the regulating lever from any of its driving or braking pos ions. of a single acting electromagnetic locking device including a magnet ada ted to he energized by the armature current oi the motor to be controlled and two cooperative elements, one of these elements being formed by the regulating lever o l? the switch drum and the other element being placed under the influence of the said magnet, and another single acting electromagnetic locking device arranged oppositely to the first mentioned locking device and, including also two cooperative elements one of these elemnts being formed by the switch drum and the other element being likewise placed under the influence of the said magnet. e

3. The combination with a switch drum for starting and controlling motors comprising regulating leveryof two single acting electromagnetic locking devices, an

auxiliary cut-out arranged in the motor circuit at a point outside the controller, and an auxiliary switch device for cooperation with the switch drum and for causing the auxiliary cut-out to enter into action only upon moving the said regulating lever back from any of its driving positions.

The foregoing specification signed at Essen, Germany, this 4th day of September, 1922.

LUDWIG SCHGN.

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