US2146228A - Selector for electric wiring systems - Google Patents

Description

Feb.7, 1939. M. E. RICHTER SELECTOR FOR ELECTRIC WIRING SYSTEMS Filed Aug. 17, 1957 lNVENTOR MORTEN EAM-HMM ElcHTr-:R

Patented Feb. 7, 1939 UNITED STATES PATENT OFFICE SELECTOR FOR ELECTRIC WIRING SYSTEMS Morten Balthazar Richter, Copenhagen, Denmark 9 Claims.

For electric wiring systems, for instance automatic and semi-automatic telephone plants, it is known to use selectors with one or more rows of stationary line contacts, the said rows being arranged one above the other one in circular rows or parts of such rows, about the axis of rotation of a rotary supporting member for one or, more frequently, two sets of movable line contacts, which member is adapted to be rotated relatively 10 to the said stationary contacts, and which sets of movable line contacts are disposed diametrically opposite one another on the said supporting member, which by its rotation moves the movable line contacts along the row of stationary line contacts and-when the stationary line contacts, for a desired connection across the selector, have been found by means of the searching contacts of the latter-will effect the desired connection by interconnecting, in pairs, the stationary line contacts concerned.

It is known to mount the movable line contacts slidably on the rotary supporting member in such a manner that when a coupling magnet, serving to couple the said member to a continuously driven driving shaft or driving disc, enters into operation, the movable contacts will be withdrawn radially from the stationary line contacts at the same time as, or immediately before, this coupling is effected, and consequently the movable contacts will not slide on the stationary contacts during the adjusting motion. Hereby the noise is avoided which the motion of the movable line contacts along the stationary line contacts would otherwise produce in the already effected concs nections across the same or other selectors in 'the selector-multiple concerned, and the advantage is attained that the wear on the contacts becomes small, and that no resistance against the motion of the rotary part of the selector will be produced by a co-operation between the movable and the stationary line contacts.

The coupling of the supporting member to the driving disc or shaft is ordinarily effected by one or, more frequently, two coupling shoes mounted i adjustably on the supporting member and being adapted to be adjusted by the armature of the coupling magnet, when the latter is attracted, and to be withdrawn from the coupling position by springs, when the desired connection has been found, and the coupling magnet then automatically has been rendered currentless.

It is essentially important that the rotary motion of the selector should be stopped practically 55 at once, when a desired connection across the selector has been found by the searching contacts of the same.

Such an instantaneous stoppage of the rotary part of the selector has formerly been proposed to be produced by means of a ratchet wheel connected rigidly to the supporting member and one 0r more stopping pawls co-operating with the said wheel and being by means of springs moved into engagement with the ratchet wheel, when the coupling magnet becomes currentless. 10

The heretofore proposed selectors of this kind, however, suifer from the drawback that the ratchet mechanism will not with certainty stop the selector in the position found by the selector contacts, but allows the rotary part of the selec- 15 tor, which has a certain inertia, to continue its rotary motion so far, after the coupling magnet has released the coupling between the supporting member and the driving shaft or disc, that the selector will stop in the space between the found 2u set of stationary line contacts and the following set of stationary line contacts, or possibly does not stop until it comes opposite the latter, viz. if the angular distance between adjacent stationary line contacts in the same row is small. 25

This is an essential drawback which certainly can be avoided either by constructing the selector with a relatively large play for the said further motion of the rotary part thereof, i. e., with relatively broad stationary line contacts and a cono siderable distance between the same, whereby, however, the number of line contacts to be disposed inside of a certain angular space in each row will be greatly reduced, or by fitting the selector with braking means for instantaneous stopping of the adjusting motion, when the coupling magnet becomes currentless. Such braking means, however, are unsuitable, as they constitute a relatively considerable resistance to the motion of the movable system of the selector, which is objectionable, as it is highly important that the adjusting motion of the selector should be effected as easily and as free of obstructions as possible.

The cause of a too late stopping of the rotary motion of the selector is to be looked for in the circumstance that the dead motion in the rachet mechanisms used heretofore in selectors of the above mentioned kind is too great, i. e., that the angular motion performed by the ratchet wheel in the most unfavourable case, from the moment when the pawls have come into contact with the teeth thereof until the moment when one of the teeth engages one of the pawls-whereby the rotary motion of the rachet wheel and, consequently, of the selector is stopped-is greater than the permissible angular motion of the movable line contacts, after the desired connection has been found. Even if the said angular motion in the ratchet-wheelmechanism can be reduced by.

an increase in the number of ratchet-wheel teeth and the use of several mutually displaced pawls, there will nevertheless, owing to the size of the teeth, be a limit to the number of teeth that can be used, and owing to the circumstance that all the pawls should be able to be operated simultaneously by means of simple constructional devices. there is a limit to the number'of pawls that can be used.

The present invention has for its object to remove the said drawback in a different manner, viz. by constructing the ratchet wheel with a diameter oi the same, or maybe a greater, order of magnitude as the diameter of circular path of the free ends of the movable line contacts, which is contrary to what has been the case heretofore, as the ratchet-Wheel diameter heretoiore, in View lof the adjustment of the pawls relatively to the coupling shoes and the displacement of the movable contacts, has beenmade considerably smaller. According to the invention, the advantage is attained that the ratchet wheel can be fitted with such a great number of teeth that the magnitude of the angular motion of the ratchet wheel and, consequently, of the rotary supporting member of the movable contacts, after the desired connection has been found, will be entirely irrelevant to the operation of the selector, provided that the pawl or pawls accordingV to the invention is or are coupled in out of engagement with the ratchet wheel during the last short part of the attraction of the arma- Y ture to the coupling magnet and, consequently,

will again be moved into engagement with the ratchet wheelvm by means of a 'spring or the like-during the iirst short part of the return motion of the armature, after a desired connection has been found, i` e., practically at the same momentas the coupling magnet has been rendered currentless.

The armature of the coupling magnet is returned from its withdrawn position by one f" more springs constructed so powerful that the residual magnetism in the coupling magnet will not appreciably delay the return motion of the armature, after the same has been attracted. Thi'sspring may be the same as the spring that causes the pawl to engage the ratchet wheel.

i As the ratchet wheel has a relatively considerable diameter, and the paw] must co-operate with he teeth on the periphery ofthe ratchet wheel,v

the coupling magnet is disposed entirely outside of the rotary part of the ratchet wheel, and in a preferred construction of the invention, the armature of the coupling magnet is coupled to the adjustable coupling shoes disposed on .the rotary part of the selector and the movable line contacts disposed on the said part by means of a vertical rod disposed centrally in relation to the rotary part of the selector, the said rod being adapted to slide longitudinally, and one end thereof being connected to the armature of the coupling magnet, while the other end thereof co-operates with two levers pivoted to the rotary supporting member of the selector, the said levers being each connected to one of the coupling shoes disposed on the supporting member, and each to one of twoV supports for two sets of movable line contacts, the said two supports being slidably mounted on two diametrically opposite sides of the supporting member, in such amanner that the said levers will be rotated by the said rod, when the armature is attracted, and thereby pulls the supports of the movable line contacts radially inward on the supporting member, at the same time as the coupling shoes are pushed radially outward so as to couple the said member to a continuously rotating driving disc.

AThe latter and the supporting member are mutually co-aXial and are journalled mutually independently ci one fanother on a common hollow stationary pivot pin, in which the said rod is adapted to slide. i

The said two levers" pivoted on the supporting member are preferably pivoted about horizontal axes, may consist of two bell-crank levers, which are mutually linked together in such a manner that a motion of the one lever about its axis of rotation will produce a corresponding simultaneous motion of the `other lever about the pivot axis of the latter and the two levers may further be interconnected by means of springs which, when the armature is released by the coupling magnet, willV force these levers to rotate in such a manner that the coupling shoes are drawn from theV coupling position, and the movable line contacts are pushed radially outward so as to touch the stationary line contacts after the same have been found.

The said pawl is suitably coupled to the armature oi the coupling magnet by means of a lever with unequal arms, the shorter one of which is actuated by the said armature during the last part cf the attraction motion of the latter, an thereby the longer arm willvbe caused to an angular motion suitable for withdrawing the pawl from the ratchet wheel, immediately before the armature, by its attraction, nas caused the coupling shoes Von the supporting member to couple the latter to the driving disc. When the couphng magnet becomes currentless, the pawl will consequently during the rst short part of the return motion of the armature from the attracted position, i. e., practically at themoment when the coupling magnet becomes currentless, move into engagement with the ratchet wheel and will, thereby, stop the motion of the selector.

The said lever, which causes the pawl to beV adjusted may be iitted with a hook which enters into the path of the armature, if the stopping pawl is not in full engagement with the teeth on Vthe ratchet wheel, and the latter therefore is in a position in which the movable linecontacts come opposite the spaces between the stationary line contacts. In such a case the said hookV will prevent the armature from moving so far backward that the movable line contacts can be moved out to the stationary line contacts and, thereby, can enter into the spaces between the latter, in which case the movable part ofthe selector would be unable to be set into operation by a fresh impulse.

The further details of the invention appear from the following description of the construction of the same shown on the drawing.

Fig. l shows a longitudinal section of the selector,

'Fig 2 the same in top view, partly in section,

Figs. 3 and 4 the central part of the selector in side elevations, in two directions at right angles to one another,

In Fig. 1 l is a continuously rotating driving disc, which is driven for instance by a driving belt 2 consisting of a helical steel spring and journalled by means of a ball bearing 3, on a hollow vertical stationary post 4, Fig. 1, on which there is further journalled, by means of another ball bearing 50, a supporting member 5 for two radially slidable supports 'I disposed on diametrically opposite sides thereof, the said supports supporting two sets of movable line contacts 6, only one of which sets is shown in Fig. l, while both sets are shown in Fig. 2. Each of these contact sets consists of three metal laminations which are wedge-shaped at their free end, and are disposed one above the other oneon the plateshaped support 'I which is made from electrically,T insulating material and is standing edge-wise, and is coupled by means of a pin 8, Fig. l, to a lever 9, which is pivoted to the supporting member 5 and is further mentioned in the following.

In the construction shown, there are two such mainly plate-shaped levers 9 disposed in a vertical or approximately vertical position on diametrically opposite sides of the post 4, in such a manner that they rest with their lower edges I on the supporting member 5.

The post 4 is iirmly held in the supporting base II of the selector on which several rows of stationary line contacts I2, Figs. l and 2, are disposed in circles about the axis of rotation A for the supporting member 5. In the construction shown, there are six rows of stationary line contacts disposed above one another and extending each over an angle of 180, so that at any time either one or the other one of the two diametrically opposite sets of movable line contacts will be situated within the angular space in which the stationary line contacts are provided.

The stationary line contacts I2 disposed in the various rows are interconnected in pairs by the movable line contacts E, when the latter are adjusted to the line contacts concerned, viz. when a desired connection has been found. The searching is effected in known manner by means of two rows of stationary searching contacts I3, Fig. 1, and one or two movable searching contacts, not shown on the drawing, which co-operate with the stationary contacts, and are disposed on the supporting member 5 in such a manner that they slide in known manner along the contacts I3 during the adjusting motion of the selector, of. my co-pending U. S. application No. 94.258, filed August 4, 1936, now Patent No. 2,135,015, dated November 1, 1938.

The movable line contacts are guided by pins I 4 on the insulating supports '1. These pins eX- tend through slits I5, Fig. 1, in the contacts 6. and between the inner end 5I of each of the latter and one of the pins I4 for instance, as shown, the inner one or, more suitably, the outer one of these, there is inserted a helical spring I5 maintaining the contacts 5 in resilient touch with the contacts I2, when a circuit connection across the selector has been established.

Il is a ratchet Awheel rigidly attached to the rotatable member 5. I8 is a pawl engaging the ratchet wheel I7 and being pivotally mounted on the supporting base I I. The surface of the pawl I8 facing the ratchet wheel is fitted with a plurality of teeth, engaging a corresponding number of the teeth of the ratchet wheel. The pawl I8 is brought into engagement with the ratchet wheel l? by means of a spring I9. ZI, 25 is a two-armed lever pivoted about a pin 22 on the base II. The said lever has a long arm 2I engaging one end of a rod 20, the other end of which is linked to the pawl I8, and a short arm 25, extending into the path of movement of the armature 23 of an electromagnet 24 mounted on the base II, so that the said armature, when attracted by the electromagnet, will engage the said short arm and thereby cause the lever 23, 25 to move into the position shown in Fig. l, thus vcausing the rod 2| to pull the pawl I8 out of engagement with the ratchet wheel ll, when the eleotromagnet 24 is energized for the purpose of intercoupling the driving disc I and the rotatable member 5 inthe manner described below.

When the electromagnet 24 is thereafter deenergized-which occurs in a well-known manner, not described, when the searching contacts I 3 of the selector have selected a desired circuit connection at the terminal I2 during the rotation of the member 5, the armature 23 is released by the electromagnet, and the spring I9 will then cause the pawl I8 to move into engagement with the ratchet wheel I1 in order to stop the rotary motion of the member 5. The rod linked to the pawl I8 will, due to the action of the spring I 9 upon the pawl I8, be forced to move longitudinally and will thereby turn the lever 2l, 25 so as to cause the short arm 25 of same to shift the armature 23 to the same short distance away from the electromagnet 24.

The armature 23 is shaped as, or supported by, a lever 21 which is pivoted about a pin 28 on the base I I and is connected, at one end, to a vertical rod 29 adapted to slide in the hollow post 4, the top end of the said rod being connected to a transverse member 3G the free ends of which support two downwardly directed pins 3l. The latter rest each against the top side of one of two naps 32 projecting on two opposite sides of the post 4 from one of the levers The said flaps 3.2, in combination with corresponding flaps 33, Figs. 2 and 3, on the other one of the levers 9, form link connections between the two levers 9, in such a manner that the latter will be forced to rotate simultaneously from the positions shown by dotted lines 33 in Fig. 3 to the position shown by full lines in the same iigure, when the flaps 33 are caused to rotate on account of the pins 3l acting the-reon, viz. when the rod 29 is moved downward, in that the armature 23 is attracted towards the coupling magnet.

By this rotation of the levers 9, the latter are forced into the positions shown by full lines in Figs. l and 3, where their upper ends rest against a transverse member 34 on the top of the post 4. As appearing from Fig. l, the levers 9 have then withdrawn the contacts t so far, .in a radial direction, from the stationary line contacts I2 that the contacts B will not touch the former. At the same time, two short arms provided on each of the two levers 5 and pr 'ecting down through incisions 52 in the support g' member 5, have pushed two coupling shoes l, disposed slidably on the supporting member 5, outward in a radial direction, so that the said shoes will come into contact with an annular flange 3l on the drivinrI disc I, in such a manner that the latter will take the supporting member 5 along during its rotary motion. The coupling shoes 35 are held in position and guided on supporting member in any suitable known manner, for instance by means of screws 39 which pass through slits 5S in the coupling shoes.

Between the short arms S5 of levers 9, springs 25, Fig. 3, are inserted on beth sides of the supporting member and when the armature 23 is released from the coupling magnet the said springs will turn the Lipper ends of levers 3 away tions 9 shown by dotted lines in Fig. 3, and thereby the levers 9 will push the supports I radially outward, in such a manner that each of the movable contacts 6, that at the given moment are situated within the arch in which the stationary line contacts are located, will be moved towards two of the said stationary contacts, and will establish the desired contact. At the same time the levers 9 will pull the coupling shoes 36 away from the ilange 31 of the driving disc. The springs 26 act by way of the aps 33 on the pins 3l, and push the latter and the rod 3U`upward, as soon as the armature is released from the coupling magnet.

During the iirst short part of the return motion of the armature, the pawl is brought into operation by the spring I9, at the same time as, or immediately after the coupling shoes 35 have been withdrawn by the springs 26 from the anget'l of the driving disc, and not until then, during the continued motion of the armature, the springs 26 will move the levers 9, in such a manner that the contacts 6 will be caused to touch the contacts I2.

When the coupling magnet again receives current, the armature will be attracted, and will then in the rlrst place cause the contacts t to be withdrawn radially from the contacts I2, before the coupling shoes, 'owing to the action of the armature, are moved out into the coupling position, as shown in Fig. 1, at the same time as, or immediately after, Vthe armature has moved the pawl I8 out of engagement with the ratchet wheel I1.

The pawl I8 is disposed in such a manner, relatively to the stationary line contacts, that it will always stop rthe movable line contacts 6 in a position radially opposite one or another of the stationary Yline contacts, when the pawl reaches the bottom of the tooth spaces in the ratchet wheel, and the pitch of the latter can easily be made as small as required in View of the selector having to be stopped just at the set of stationary line contacts that has been found at the given moment. It may happen, however, that the pawl, for some reason or other, does not slide home in the tooth spaces, but comes to rest against the side faces of a tooth or two and,

,A thereby, stops the supporting member 5 in an intermediate position in which the movable contacts 6 come opposite the vspace between two consecutive stationary line contacts. In order to prevent the contacts 6 from their moving out into these spaces, whereby the movable part of the selector would become unable to Venter into operation at a subsequent starting impulse, the lever 2l may be tted with a hook 53 which, in the case of the pawl I8 having not reached the bottom of the tooth spaces of the ratchet wheel, will extend down into the path of the armature 23, or rather the path of a pawl 55 attached adjustably thereto by means of screws 5d, and will thereby prevent the armature from returning so far from an attracted state that the contacts 6 can be moved out so as to touch the contacts I2.

Having now particularly described 'and ascertained the nature of my invention and in what manner the same is to be performed I declare that what I claimis: Y

1. A selector of the power driven type for electric connecting systems, comprising a plurality of stationary terminals arranged in a number of circular arcs, a Vrotatable 'member centrally disposedre'latively to the said arcs, a driving mem; bei' to be continuously rotated, coupling means mounted on said rotatable member and adapted to intercouple the latter and the driving member, a number of movable contacts, adjustably mounted on the4 said rotatable member so as to be moved by same in circular paths along the said aros of stationary terminals, a stationarily disposed electromagnet, an armature for said electromagnet, associated with the said 'coupling means, and with the said movable contact so as to cause the coupling means to engage the driving member and to simultaneously shift the movable contacts radially out of engagement with the stationary terminals, when the said electromagnet is energized, a ratchet wheel rmly connected to the said rotatable member and being co-axial to same, a pawl co-operating with the saidA ratchet wheel, a lever engaging the said pawl and arranged to be engaged itself Vby the said armature, when attracted, so as to move the pawl out of engagement with the ratchet wheel, before the armature due to its attraction causes the said coupling means to intercouple the said rotatable member and the said driven member.

2. A selector of the power driven type for electric connecting systems', comprising a plurality of stationary terminals arranged in a number of circular arcs, a rotatable member centrally disposed relatively to the said arcs, a driving member to be continuously rotated, coupling means mounted on said rotatable member and adapted to intercouple the latter and the driving member, a number of movable contacts, adjustably mounted on the said rotatable member so as to be moved by same in circular paths along the said arcs of stationary terminals, a stationary disposed electromagnet, an armature for said electromagnet, associated withY the 'said coupling means and with the said movable contact so as to cause the coupling means to engage the driving member and to simultaneously shiftV the movable contacts radially out of engagement with the stationary terminals, when the said electromagnet is energized, a ratchet wheel iirmly connected to the said rotatablememberandbeing Yco-aXial to same, a pawl co-operating with .the

said ratchet wheel, a lever comprising a short arm arranged to be engaged by the said armature when attracted and a longer arm engaging the said pawl, so as to move the pawl out of 'engagement with the ratchet Wheel during the last fraction of the total motion of said armature when attracted, directly before the armature causes the interooupling of the rotatable member and the driving member.

3. A selector of the power driven type for electric connecting systems, comprisingra plurality of stationary terminals arranged in a number of circular arcs, a rotatable member centrally disposedrelatively to the said arcs, a driving member to be continuously rotated, coupling means mounted on said rotatable member and adapted to intercouple the latter and the driving member, two sets of movable contacts, resiliently and slidably mounted on the said rotatable member so 'as to be moved by turns along the arcs of stationary terminals, a ratchet wheel, associated with the said rotatable member so as to be rotated together with same, a pawl, a spring causing the said pawl to engage the said Yratchet,

tromagnet, a lever journalled on a stationary base and associated with the said pawl and arranged to be engaged by the said armature so as to remove the said pawl from the ratchet wheel against the action of the said spring when attracted by the electromagnet, a vertically disposed rod, adjustably mounted in a central position relatively to the said rotatable member so as to be shifted longitudinally, means interconnecting the said armature and the said rod to Shift the latter longitudinally in a downward direction, when the armature is attracted by the said electromagnet, two levers pivotally mounted on the rotatable member on opposite sides of the said centrally disposed rod so as to be engaged by same, when the rod is slid by the said armature, means for connecting each of said levers to one of said sets of movable contacts to shift the latter radially on the said rotatable member apart from the circular rows of stationary terminals, when the said levers are engaged by the said rod, and other means to connect the said two levers to the said coupling means, so as to cause the latter to intercouple the rotatable member and the continuously rotated driving member, simultaneously with the said radial displacement of the movable contacts.

4. A selector of the power driven type for electric connecting systems comprising a plurality of stationary terminals arranged in a number of circular arcs, a hollow stationary pivot pin centrally disposed relatively to the said arcs, a-rotatable member pivotally mounted on the said pivot pin, a driven member pivotally mounted on the said pivot pin and adapted to be continuously rotated, means supported by the said rotatable member and adapted to intercouple this member and the said driven member, two sets of movable contacts, resiliently and slidably mounted on the said movable member so as to be moved by turns along the arcs of stationary terminals, a ratchet wheel, associated with said rotatable member, a pawl arranged to engage said ratchet wheel, a spring causing this engagement, an electromagnet, an armature for said electromagnet, a lever arranged to be engaged bythe said armature, when attracted by the electromagnet, so as to cause the said pawl to move out of engagement with the said ratchet wheel against the action of the said spring, a vertical rod slidably mounted in the said hollow vertical pivot pin, means interconnecting the said armature and the said rod to shift the latter longitudinally in a downward direction, when the armature is attracted by the said electromagnet, two levers pivotally mounted on the rotatable member on opposite sides of the said centrally disposed rod so as to be engaged by same when the rod is slid by the said armature, means for connecting each of said levers to one of said sets of movable contacts to shift the latter radially on the said rotatable member apart from the circular rows of stationary terminals, when the said levers are engaged by the said rod, and other means to connect the said two levers to the said coupling means so as to cause the latter to intercouple the rotatable member and the continuously driven member, simultaneously with the said radial displacement of the movable contacts.

5. A selector of the power driven type for electric connecting systems comprising a plurality of stationary terminals arranged in a number of circular arcs, a hollow stationary pivot pin centrally disposed relatively to the said arcs, a

rotatable member pivotally mounted on the said pivot pin, a driven member pivotally mounted on the said pivot pin and adapted to be continuously rotated, means supported by the said rotatable member and adapted to intercouple this member and the said driven member, two sets of movable contacts, resiliently and slidably mounted on the said movable member so as to be moved by turns along the arcs of stationary terminals, a ratchet wheel, associated with said rotatable member, a pawl arranged to engage said ratchet wheel, a spring causing this engagement, an electromagnet, an armature for said electromagnet, a lever arranged to be engaged by the said armature, when attracted by the electromagnet, so to cause the said pawl to move out of engagement with the said ratchet wheel against the action of the said spring, a vertical rod slidably mounted in the said hollow vertical pivot pin, means interconnecting the said armature and the said rod to shift the latter longitudinally in a downward direction, when the armature is attracted by the said electromagnet, two levers pivotally mounted on the rotatable member on opposite sides of the said centrally disposed rod and comprising each an edgewise disposed vertical plate supported freely at its lower edge upon the rotatable member and arranged to be engaged by the said rod, when the latter is slid by the said armature, means for connecting each of said levers to one of said sets of movable contacts to shift the latter radially on the said rotatable member apart from the circular rows of stationary terminals, when the said levers are engaged by the said rod, and other means to connect the said two levers to the said coupling means so as to cause the latter to intercouple the rotatable member and the continuously driven member, simultaneously with the said radial displacement of the movable contacts.

6. A selector according to claim 5 comprising springs interconnecting the downward extending portion of the lower portions of the two edgewise disposed levers on the rotatable member so as to swing the said two levers away from the positions into which they are brought by the action of the said rod, when the armature is released by the electromagnet, in order that one set of the movable contacts should engage the stationary terminals, and simultaneously putting the coupling means out of engagement with the driving member.

'7. A selector of the power driven type for electric connecting systems comprising a plurality of stationary terminals arranged in a number of circular arcs, a hollow stationary pivot pin centrally disposed relatively to the said arcs, a rotatable member pivotally mounted on the said pivot pin, a driven member pivotally mounted on the said pivot pin and adapted to be continuously rotated, means supported by the said rotatable member and adapted to intercouple this member and the said driven member, two sets of movable contacts, resiliently and slidably mounted on the said movable member so as to be moved by turns along the arcs of stationary terminals, a ratchet wheel, associated with said rotatable member, a pawl arranged to engage said ratchet wheel, a spring causing this engagement, an electromagnet, an armature for said electromagnet, a lever arranged to be engaged by the said armature, when attracted by the electromagnet, so as to cause the said pawl to move out of engagement with the said ratchet 'wheel againstthe action .o'f Vthe said spring, a vertical rod slidably mounted in the said hollow verticalY pivot pin, means interconnecting the said armature and the said rod to shift, the latter longitudinally in a downward direction, when the armature is attracted by the said electromagnet, two levers pivotally mounted on the rotatable member on opposite sides of the said centrally disposed rod, a traverse member connected .to the upper end .of the, said rod, a vertical, downwardly projecting pin on each end of said traverse member, the said two levers comprising each an edgewise disposed vertical plate freely supported at its lower edge upon the rotatable members and fitted with radially disposed arms arranged to be engaged by the said pins so as` to cause ther said two levers to swing when the 1 centrally diposed rod is slided by the said armature, means for connecting each of said levers to one of said sets of movable contacts to shift the latter radially on the said rotatable member apart from the circular rows of stationary terminals, when the said levers are engaged by the Vsaid rod, and other means to connect the said two levers to the said coupling means so as to cause the latter to intercouple the rotatable member and the continuously driven member simultaneously with the said radial displacement of the movable contacts.

8. A selector according to claim 7 in which the two levers mounted on the rotatable member are interlinked.

9. A selector of the power driven type for electric connecting systems, comprising a plurality of stationary terminals arranged in a number of circular arcs, a rotatable member centrally disposed relatively to the said arcs, a

driving member to be continuously rotated, coupling means'mounted on said rotatable member and adapted to `intercouple the latter and the driving member, .a number of movable contacts, adjustably mounted on the said rotatable member ,so as to be moved by same in circular paths along the said arcs of stationary terminals, a stationary disposed electromagnet, an armature for said electromagnet, associated with the said coupling means and with the said movable Contact so as to cause the coupling means to engage the driving member and to simultaneously shift the movable contacts radially out of engagement with the stationary terminals, when the said electromagnetV is energized, a ratchet Wheel iirm-ly connected to Ythe said rotatable member and being coaxial to same, a pawl cooperating with the said ratchet wheel, a lever comprising a short arm arranged to be engaged by the said .armature when attracted and a longer arm engaging the said pawl, so as to move the pawl out of engagement with the ratchet wheel during the last fraction of the total motion `of the said armature When attracted, directly before the armature causes the intercoupling of the rotatable member and the driving member, and a hook on the said pawl arranged to extend into the path of the said armature of the said electromagnet, if the pawl is not in full engagement with the teeth of the ratchet wheel in order to prevent the armature from returning to a position, in which it allows the movable contacts to engage .stationary terminals, until the pawl has moved in proper engagement with therratchet wheel.

MOETEN ALTHAZAR RICHTER.

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