US3162797A

US3162797A - Starting devices for electric motors

Info

Publication number: US3162797A
Application number: US81602A
Authority: US
Inventors: Blanchard Jean; Douchet Florimond
Original assignee: VEHICULES ET TRAVAUX VETRA
Current assignee: VEHICULES ET TRAVAUX VETRA
Priority date: 1960-01-20
Filing date: 1961-01-09
Publication date: 1964-12-22
Anticipated expiration: 1981-12-22
Also published as: FR1255034A; BE597732A; CH371498A; ES263219A1

Description

Dec. 22, 1964 J. BLANCHARD ETAL 3,162,797

STARTING DEVICES FOR ELECTRIC MOTORS Filed Jan. 9, 1961 2 Sheets-Sheet 1 lNl EN TUEJ. JEAN BLANCH/1E0 Fl Oil/MONO DOZ/U/FT 3) ATTOE/VEYS 2 Sheets-Sheet 2 1964 J. BLANCHARD ETAL STARTING DEVICES FOR ELECTRIC MOTQRS Filed Jan. 9, 1961 United States Patent 3,162,797 TARTNG DEVHCES lFil R ELECTRIC MOTQRS lican Blanchard, Paris, France, and Florimond Donchet, 41 Rue Henri Vassenr, Argenteuil, France; said Blanchard assignor to Vehicuies ct Travaux VETRA, Paris, France, a French company Filed Jan. 9, 1961, Ser. No. 81,662 Qlaiins priority, application France, Jan. 20, 1966?, Model, Patent 1,255,034 (Claims. (Cl. 318-278) Change-over switches are already known which comprise a number of cams keyed on a common shaft and having a certain angular displacement with respect to each other, each cam being adapted to co-operate with a lever provided with a movable contact or contact-stud, with the object either of displacing the said movable contact at a distance away from a fixed contact employed in combination with the said movable contact or of bringing this latter into contact with the said fixed contact. The rotation of this common shaft and therefore the displacement of the said levers has the effect of progressively cutting out of the circuit the electrical resistances which are inserted in the armature circuit of the motor so as to limit the current surge at each phase of the starter.

Change-over switches of this type are usually, although not exclusively, employed in starting devices for electric motors employed in rail and road haulage.

The devices of this type which are at present known carry out both the supply and the interruption of the electric currents which they control. Consequently, each of the switching elements constituting the said devices must necessarily be arranged so as to produce the quenching of the electric breaking are as rapidly as possible, and this requirement considerably complicates their construction inasmuch as each of these elements must have the same potential capabilities as a circuit-breaker.

The present invention has for its object various improvements made in the devices referred to above and is mainly characterized by the fact that it achieves the separation of the two functions referred to above, that is: the supply and the interruption of current.

A device in accordance with the invention therefore comprises, firstly a cam-type change-over switch having the exclusive function of successively closing the circuits in which the starting resistances are located so that the closure of one circuit corresponds to the elimination or cutting-out of the corresponding resistance, and secondly a circuit-breaker of the conventional type employed in combination with the said change-over switch, the purpose thereof being to effect the interruption of the current when the motor is stopped by means of the said circuit-breaker alone.

The change-over switch mainly constituting the object of the present invention comprises one or a number of the characteristic features defined hereunder:

(a) The cams have a profile such that the camshaft cannot move back in the direction opposite to its normal direction of rotation as long as the current remains established;

(b) The cams also have a profile such that the closure of a circuit by means of a contact-surface is effected suddenly under the action of a spring, the said spring being also employed for the purpose of applying a continuous pressure against the contact-surfaces which work together;

(0) The contact surfaces are at an oblique angle with respect to the direction of the movement of the contacts, in such manner that the elastic deformation which results from the effort of contact produces a very light sliding of the said contact surfaces one over the other. This arrangement makes it possible to limit any danger of rebounding of'these contacts with respect to each other and to avoid the subsequent formation of electric arcs which are detrimental to the proper performance and resistance of the said contacts; moreover, the light sliding of the contacts one over the other cleans the surfaces in contact and eliminates the light coating of oxide with which the contacts may be covered;

(d) When the electric current is interrupted by the circuit-breaker, a device comes into action in such manner as to move the contact-carrying levers away from the corresponding cams, while an elastic member is provided for the purpose of restoring the said cams to their initial position;

(e) There is more especially provided a releasing device comprising as many levers carrying push-fingers as there are contact-carrying levers, these levers being operated simultaneously with the object of bearing against the contact-carrying levers so as to hold these latter at a distance from the cams with which they co-operate;

(f) The contact-carrying levers are mounted in detachable manner with a view to facilitating their rapid separation from the body of the apparatus.

Further characteristic features of the invention will be brought out by the description which follows below, reference being made to the accompanying drawings, which are iven by way of example only without any limitation being implied, and in which:

FIG. 1 illustrates a diagrammatic general view of a device in accordance with the invention.

FIG. 2 is a transverse partial cross-section of the said device.

FIG. 3 is a partial front view corresponding to FIG. 2.

FIG. 4 is a view in profile of a system of operation of the contact-carrying levers.

FIG. 5 is a view in perspective corresponding to FIG. 3.

As shown in FIG. 1, the motor is supplied from the main current source between the input and output terminals 1 and 2, the current successively passing through the change-over switch, the outline of which is shown in the drawing in chain-dotted lines, and passing through resistances in series such as those designated by the references 3, i, 5, etc. The current subsequently passes through the switch 6, the operation of which is carried out by means of an electro-magnet 7 which is excited by a current drawn off the main circuit through an auxiliary circuit. This current can also be supplied from an auxiliary source.

There is additionally provided in the change-over switch a release electro-magnet 8 which will be described in det-ail below, and the excitation of which is controlled by the action of a switch 9 operating in the direction opposite to that of the switch 6, both switches 9 and 6 being controlled by the electro-magnet 7. As a result of the arrangement of the contacts 6 and 9, the excitation of the electro-magnet 8 can only be produced when the switch 6 is open, that is to say, during the interruption of the main current.

It has been found that in this form of arrangement, the units 7, 6 and 9 carries out the function of establishing and breaking the main current whereas the change-over switch plays no part in these operations.

As is shown more especially in FIG. 2, the change-over switch comprises a shaft iii on which are keyed a certain, number of cams such as the cam 11 which are preferably made of insulating material. The said shaft 19 can be driven in rotation by any suitable means, either manually or mechanically. The said cams comprise a circular cam-profile in the shape of a spiral, the said cams terminating in a substantially radial face 12, so that the cam can rotate in the direction of the arrow F but cannot rotate in the opposite direction while co-operating with a roller which will be described below. The cams, which are mounted in succession on the shaft 10, are angularly displaced in such manner that the radial faces 12 are also displaced with a view to bringing the contact-carrying levers into successive operation.

A contact-surface 1 3 formed on a lever 14 is designed to correspond to each cam and to co-operate with the said cam; this lever 14 terminates in the shape of a semicircle 1611 at the extremity opposite to the contact-surface 13, the said semi-circular portion bearing against a conductive bar 1'7 having a circular section, as shown in FIG. 1. This conductive bar 17 is insulated from the remainder of the installation and is connected to the electric circuit controlled by the change-over switch. The lever 14 is applied against the shaft 1'7 by means of a stirrup member 15 which is rigidly fixed to the said lever and on which is mounted the roller 16.

As can be seen in the drawing, the stirrup member 15 and its lever 14- are applied against the circular bar 17, on the one hand as a result of the pressure applied by the roller 16 against the cam 11 or of the pressure applied against each other by the two

contacts

13 and 21 and, on the other hand, on account of the fact that a rod 18 is passed through the said stirrup member 15 at the opposite extremity of this latter with respect to the said roller 16 and that a spring 19 which is fitted round the said rod 18 serves to push the said stirrup member towards a member 20 having the shape of an angle-iron which is rigidly fixed to the frame, but electrically insulated from this latter. The rod 18 is held to the member 20 by means of a cotter-pin passed transversely through one of the extremities of the said rod, while the other extremity carries a supporting member for the spring 19. This arrangement on the one hand ensures the articulation of the lever 14 on the bar 17, thereby permitting the lever tov pivot about the said bar, and on the other hand permits the assembly of stirrup member and lever to be easily detached from the remainder of the device, this operation being carried out after having first detached the rod 18 from the member 20.

A fixed contact 21 designed to correspond to each movable contact 13 is fixed to an insulated collar 22 mounted on a common bar 23. Each collar is connected to the. input or to the output of one of the resistances such as those designated by the references 3, 4 and 5.

Each of these levers 14 carrying movable contacts 13, is thus subjected to the action of the spring 19 which tends to cause the said levers to pivot about. the circular bar 17. This spring 19 therefore has the effect of tending to bring the roller towards the cam and consequently to bring the movable contact-surface 13 towards the contact-surface 21 which is fixed, so that when these latter arev in contact with each other, the said spring also supplies the effort which is necessary to ensure the proper flow of current. The combined assembly of movable contacts and fixed contacts which have just been described operates as follows:

It is assumed that the electrical starting system is such that in the initial position, the movable contacts ofthe type indicated by the reference 13 and the fixed contacts of the type designated by the reference 21 are in the separated position, the rollers 16 being applied against those portions of the cams having a larger diameter such as the portions 11 and all the resistances being thus inserted in the armature circuit of the motor.

As a result of the rotation of the shaft 10, which takes place in the direction of the arrow F, that portion of the cam 11 which has the smaller diameter is brought into a position oppositely facing the roller 16. From this moment, the lever 14, which is subjected to the action of the spring 19, pivots about the bar 17 and thus, in a sudden manner, brings into contact the contact-surface 13 and the contact-surface 21. In the sequence which has been chosen, this bringing into contact has the effect of cutting out a portion of the starting resistance. The same effect takes place successively in the case of each switching element as the rotation of the shaft 10 proceeds, since the cams are displaced angularly.

It is in this respect that the characteristic shape given to the cam and especially to the radial surface 12 produces its effect, by preventing the rotation of the shaft 10 in the reverse direction, which otherwise would result in the sudden opening of the electrical circuit concerned.

In the example of construction which has been described, the releasing system is composed of a certain number of push-fingers 24 formed on levers 33, as can be seen in FIGS. 2 to 5. These levers 33 are rigidly fixed to the bar 17 and can thus be displaced angularly as a result of the rotation of the said bar. The pushmember or finger 24 is slightly set back with respect to the contact-carrying lever 14. When the circular bar 17 begins to move in rotation, the fingers 24 are brought to bear against the levers 14 and tend to move the said levers away from the cam 11, with the resulting effect of separating the

contacts

13 and 21 and moving the rollers 16 away from the radial surface 12 of the cam 11. The cams being thus released, they can be returned to their initial position; this return to position can be effected by any suitable means, for example under the action of an opposing spring. The rotation of the bar 17 can be effected by means of a device which is more especially shown in FIGS. 4 and 5. This device comprises an electro-magnet which is illustrated diagrammatically at 8' in FIGS. 1 and 4 and which comprises a plunger 26, pivotally mounted by means of a bell-crank or elbowjoint lever 27-28 which is pivotally mounted at 29; the said bell-crank transmits movement by means of the connecting-rod 30 to a link-rod 31 which is keyed to the bar 17. Any excitation of the electro-magnet naturally results in the rotation of the said bar 17 and is consequently followed by a thrust applied by the fingers 24 against the levers such as those designated by the reference 14 which are provided with the movable contacts 13.

The general operation of the apparatus which has been described above is as follows:

In the initial position, all the rollers 16 bear against those portions of the earns 11 having a larger diameter, all the contacts 13-21 are open, so that all the resistances in series 3, 4 and 5, etc. are inserted in the circuit supplying the armature of the motor. When the electromagnet '7 is excited by operating the switch 32, the circuit of the electro-magnet 8 is broken at 9, while the main circuit is closed at 6'. The electro-magnet 8 is no longer excited, the fingers 24 thus return to their initial position and. no longer obstruct the movement of the contactcarrying levers 14.

At this moment, the shaft 10 can beset in rotation by any suitable means, thereby giving rise to the successive putting into contact of the various pairs of contacts 13-21 and consequently the progressive cuttingout by short-circuiting of the resistances such as those which have been designated by the references 3, 4 and 5. The motor has thus been brought up to operative speed. When it is desired to stop the motor, the excitation circuit of the electro-magnet 7 is interrupted by means of the switch 32. This results in the interruption both of the circuit supplying the motor by means of the switch 6 and of the excitation of the electro-magnet 8 by means of the switch 9. The combined assembly of levers 33 carrying the push-fingers 24 works on the levers 14 and the stirrup-members 15 carrying the rollers 16. The said rollers 16 are moved away from the cams 11, thus making itpossible for these latter to rotate freely.

When urged by a means such as a manual control or an oppositely-acting spring, the shaft 10 rotates in the direction opposite to that of the arrow F and brings back all the cams 11 combined to their initial position. The

. apparatus is thus ready for starting up again.

It is naturally understood that the form of execution which has just been described is given solely by way of non-limitative. example, and alternative forms of execution or construction can be devised without thereby departing either from the scope or the spirit of the present invention. In particular, the device as described or illustrated comprises a bar 17 which is common to all contactcarrying levers. It is obvious that this arrangement is not indispensable although it constitutes a simplification, and it can perfectly well be assumed that the different contact-carrying levers 14 have no common point and no positive drive-coupling.

What We claim is:

1. A starting device for an electric motor having a plurality of starting resistances, comprising:

a switch having a first set of contacts connected, respectively, to the starting resistances, said switch having a second set of contacts, each contact of the second set being adapted for engagement with one of the contacts of the first set;

spring means for urging the contacts of said second set into engagement with the contacts of said first set;

cam means rotatable in one direction for holding the contacts of said second set away from the contacts of said first set against the urging of said spring means, said cam means having a sharply broken profile for permitting the contacts of the second set to move quickly into contact With the contacts of the first set under the urging of said spring means, said profile preventing reverse rotation of said cam means;

selectively operable push means for moving the contacts of said second set away from the contacts of said first set and out of contact with said cam means so that said cam means can be returned to a starting position;

an electrically operated device connected for effecting operation of said push means;

a circuit breaker connected in series with said motor for controlling the supply of electrical energy thereto; and

a switch responsive to operation of said circuit breaker and connected to said electrically operated device so that said electrical operated device is energized to effect movement of the second set of contacts away from the first set of contacts and away from the cam means when the supply of electrical energy to the motor is interrupted by said circuit breaker.

2. A starting device for an electric motor according to claim 1, in which each of the contacts of the second set is carried by a pivotable cam-carrying lever;

said spring means including a spring associated with each cam-carrying lever for urging the contact carried by each lever toward its associated contact of the first set;

said cam means including a cam associated with each cam-carrying lever and rotatable about an axis sub stantially parallel with the pivot axis of its associated lever, said cam having a circumferential cam surface and a substantially radially extending end surface; and

said push means including a push lever carrying a push finger pivotable into engagement with each of said cam-carrying levers.

3. A starting device according to claim 2, in which said cam-carrying levers and said push levers are commonly mounted for pivotal movement on a bar.

4. A starting device according to claim 3 in which the bar is circular in cross section and in which said camcarrying levers each include an arcuate portion partially embracing less than half of the bar so that they can be easily removed therefrom, said spring holding each camcarrying lever in releasable engagement with said bar.

5. A starting device according to claim 1, in which the contacts of said first and second sets having substantially parallel contact surfaces which are disposed at an oblique angle to the direction of movement of said contacts with respect to each other.

References Cited in the file of this patent UNITED STATES PATENTS 1,547,143 Cox July 21, 1925 1,980,951 Buchhold Nov. 13, 1934 2,366,968 Kaufmann Jan. 9, 1945 2,519,976 Phelon Aug. 22, 1950 FOREIGN PATENTS 454,929 Great Britain a Oct. 5, 1936

Claims

1. A STARTING DEVICE FOR AN ELECTRIC MOTOR HAVING A PLURALITY OF STARTING RESISTANCES, COMPRISING: A SWITCH HAVING A FIRST SET OF CONTACTS CONNECTED, RESPECTIVELY, TO THE STARTING RESISTANCES, SAID SWITCH HAVING A SECOND SET OF CONTACTS, EACH CONTACT OF THE SECOND SET BEING ADAPTED FOR ENGAGEMENT WITH ONE OF THE CONTACTS OF THE FIRST SET; SPRING MEANS FOR URGING THE CONTACTS OF SAID SECOND SET INTO ENGAGEMENT WITH THE CONTACTS OF SAID FIRST SET; CAM MEANS ROTATABLE IN ONE DIRECTION FOR HOLDING THE CONTACTS OF SAID SECOND SET AWAY FROM THE CONTACTS OF SAID FIRST SET AGAINST THE URGING OF SAID SPRING MEANS, SAID CAM MEANS HAVING A SHARPLY BROKEN PROFILE FOR PERMITTING THE CONTACTS OF THE SECOND SET TO MOVE QUICKLY INTO CONTACT WITH THE CONTACTS OF THE FIRST SET UNDER THE URGING OF SAID SPRING MEANS, SAID PROFILE PREVENTING REVERSE ROTATION OF SAID CAM MEANS; SELECTIVELY OPERABLE PUSH MEANS FOR MOVING THE CONTACTS OF SAID SECOND SET AWAY FROM THE CONTACTS OF SAID FIRST SET AND OUT OF CONTACT WITH SAID CAM MEANS TO THAT SAID CAM MEANS CAN BE RETURNED TO A STARTING POSITION; AN ELECTRICALLY OPERATED DEVICE CONNECTED FOR EFFECTING OPERATION OF SAID PUSH MEANS; A CIRCUIT BREAKER CONNECTED IN SERIES WITH SAID MOTOR FOR CONTROLLING THE SUPPLY OF ELECTRICAL ENERGY THERETO; AND A SWITCH RESPONSIVE TO OPERATION OF SAID CIRCUIT BREAKER AND CONNECTED TO SAID ELECTRICALLY OPERATED DEVICE SO THAT SAID ELECTRICAL OPERATED DEVICE IS ENGERGIZED TO EFFECT MOVEMENT OF THE SECOND SET OF CONTACTS AWAY FROM THE FIRST SET OF CONTACTS AND AWAY FROM THE CAM MEANS WHEN THE SUPPLY OF ELECTRICAL ENERGY TO THE MOTOR IS INTERRUPTED BY SAID CIRCUIT BREAKER.