US2313466A - Electric clock system - Google Patents

Description

March 9, 1943. o. H. DICKE ELECTRIC CLOCK SYSTEM 5 Sheets-Sheet 1 Filed Dec.

'INVENTOR March 9, 1943.

0. H. DICKE ELECTRIC CLOCK SYSTEM Filed Dec. 14, 1938 s Sha'ets-Sheet 2 INVENTOR A March 9,1943. 0. H. D ICKE ELECTRIC CLOCK ISHYS'IQ'EM Filed Dec. 14, 1958 5 Sheets-Sheet 3 INVENTOR omua March 9, 1943. o. H. DlCKE ELECTRIC CLOCK SYSTEM 5 Sheets-Sheet 4 Filed Dec. 14, 1938 March 9, 1943.

FIG. 8.

O H. DICKE ELECTRIC GLOCK SYSTEM Filed Dec. 14, 1938 5 Shets-Sheet 5 INVENTOR wwz 1 Patented Mar. 9, 1943 I UNITED STATES PATENT OFFICE ELECTRIC CLOCK SYSTEM Oscar H. Dicke, Rochester, N. Y. Application December 14, 1938, Serial No. 245300 23 Claims. (01. sa -24) The present invention relates to time control systems and more particularly to time clock systems driven by synchronous motors forpunching or printing on a time card the time of arrival and departure of an employee to and from his place of employment, indicating time in railway stations, schools and office buildings, and the like.

In systems of the above type the secondary clocks may be corrected in the fifty-ninth minute, in that extreme accuracy in the last minute is not important.

In accordance with the present invention a slow secondary clock is advanced by a second or auxiliary synchronous motor which has a higher speed or is connected to the time shaft by a gear train having a higher'gear ratio so as to rotate the time shaft at a higher speed; or is corrected by the same motor by operating it at a higher 1 speed from the same source of alternating current during the correcting period so as to make the time shaft run faster during correction of a slow clock. In accordance with the present invention a fast clock is corrected by stopping the secondary clock at a certain time indicating point and to again allow it to advance when the master clock reaches a corresponding time indicating P int.

One of the objects of the present invention resides in the employment of one or more syn- Another object of the present invention resides in the provision of novel master clocks in which one element of the master clock used for operating clock correcting contacts is always in substantial synchronism with the secondary clocks in spite of the fact that the secondary clocks are at rest during alternating current cessation, such current being derived from a commercial power system having its frequency regulated to correctly manifest passing of time.

Other objects of the present invention reside in the provision of master clocks in which joint action of escapement mechanisms and synchronous motors driven by alternating current of regulated frequency correctly manifest the passing of time and in which the master clock time cycle passage during the presence of alternating current.

Another bject of the present invention resides in the provision of means to accelerate a master clock when it is tardy with respect 0 a synchronous motor and to retard such aster clock when. it is fast with respect to such synchronous motor during the presence of alternating current and to adjust its time measuring mechanism to normal during a cessation of alternating current.

The alternating current mentioned being derived from a source having its frequency regulated to manifest accurately the passing of time.

Another object of the present invention resides in the provision of a plurality of line circuits connecting a master clock and one or more secondary clocks, these circuits-being energized in sequence by the master clock, and to provide circuit selecting means for each "secondary clock, I

which secondary clock has a high speed driving circuit and a low speed driving circuit, such that the high speed driving circuit is connected to the then energized line circuit; when the secondary clock is slow, but the low speed driving circuit is so connected when the secondary clock is correct, other means being provided to holdthe secondary clock at stop when it is fast.

trains having difl'erent gear ratio;

Fig. 1A shows how a push button manually operated may correct a secondary clock;

Fig. 2 illustrates a modified master clock from A that shown in Fig.1 for controlling a secondary clock suchas illustrated in Fig. 1, but through the medium of a single circuit, rectiflers being used to isolate two different currents ioto separate synchronous motors, and in which the master clock is automatically regulated from time to time so as to cause it to run in accordance with the rate of cycle passage only so long as there is no current cessation;

Fig. 3 shows a modification of time control system which is conveniently called a correspondshaft is advanced in accordance with current once type time control system whereby a simple commutator on a continuously running shaft of a master clock such as shown in Figs. 1 and 2 may control a secondary clock over four wires;

Fig. 4 shows a time control system similar to that shown in Fig. 3 but employing only three line wires instead of four,

Fig. 5 shows a modified secondary clock contact structure for the system shown in Fig. 4, this modified structure when used in the system of Fig. 4 causes a secondary clock to be corrected only to the extent of a predetermined fraction of its then tardiness during each of successive equal time intervals similar to the system shown in Fig. 3;

Fig. 6 shows a time control system employing the master clock shown in Fig. 2 and employing a secondary clock such as shown in Fig. 4 but employing additional contact mechanism for at times connecting the two control lines together;

Fig. '7 illustrates the mechanism that is preferably employed when a secondary clock is used for stamping time cards, or the like.

Fig. 8 shows a double synchronous motor for secondary clock control and correction.

Fig. 9 shows an exploded perspective of the motor shown in Fig. 8.

Fig. 10 shows in section a modified form of double synchronous motor taken on the line I0-l 0 of Fig. 11 as viewed in the direction of the arrows.

Fig. 11 is a section of the same motor taken on the line I II I of Fig. 10.

Fig. 12 shows how Fig. 6 may be modified when using synchronous motors SM and SM", the double motors of Fig. 8 or 11 or the two speed synchronous motor of Fig. 13 in the secondary clocks; and

Fig. 13 shows a two speed synchronous motor which constitutes either a two pole or a four pole motor depending on which of its two circuits is energized.

In accordance with the present invention it is proposed to employ or have available a commercial alternating current power distributing system delivering current of regulated frequency, that is, current having its average frequency regulated to correctly manifest time by cycle passage or summation. In each case the master clock is of a construction to be regulated (Fig. 2) so as to run in synchronism with alternating current cycle passage, or by correcting a master electric clock in accordance with the duration of a current cessation during each current cessation (Fig. 1). The secondary clocks may be used as a tower clock by using a separate unit for each dial, to operate record sheets, as bell ringers or for any other program purpose.

extremely simple construction. It is found that it is more economical to add an auxiliary motor than to add a relayyor an electrically operated clutch or gear shift. This is especially true If the added synchronous motor has its rotor mounted on the same shaft with the main motor so that no additional bearings are required as is the case in applicants construction in Figs. 3, 4, and 6. It is also proposed to employ contacts to temporarily stop the secondary clock by opening the motor circuit to correct a fast secondary clock. In order to correct a slow clock it is proposed to employ a stator acting on a higher speed, fewer poles, rotor, see Figs. 3 and 4, for instance. In each of Figs. 3 and 4 the secondary clock is advanced after each alternating current cessation although not necessarily immediately and is specially corrected at the end of each particular time interval such as an hour, and ii the first 20 mentioned correction carries through such even hour point on the secondary clock no special release is necessary.

In the correspondence form of invention shown in Figs. 3 and 4 each secondary clock includes two motors capable of driving the secondary clock ary clock is late or on time.

5 means for stopping the secondary clock when it The inventions disclosed in this application are improvements over the inventions disclosed in my prior applications Ser. No. 365,584 filed May 23,

,1929 now Patent No. 2,248,164 granted July 8,

1941; Ser. No. 441,109 filed April 2, 1930; Ser. Nos. 729,079 and 729,080 filed June 5, 1934, and now respectively Patents Nos. 2,248,165:a'nd 2,185,334

granted respectively on July 8, 1941, and January 2, 1940; Ser. No. 239,538 filed November 8, 1938, and the application of Robert H. Dicke Ser. No. 39,146, filed September 4, 1935, now Patent No. 2,151,317 granted March 21, 1939.

The subject matter of Figs. 1, 1A, 2 and 13 is not specifically claimed herein but is claimed in divisional application Ser. No. 472,698, filed January 18, 1943.

It is also proposed to have secondary clocks of reaches the end of such period if the secondary clock is fast.

In the correspondence type of clock'system construction of Figs. 3 and 4 the secondary clock is one in which two synchronous motors having common bearings is employed. As' illustrated one of these motors has a six pole rotor and has a synchronous speed of 1200 R. P. M. whereasthe other has a two pole rotor and has a. synchronous speed of 3600 R. P. M., and the construction is such that normally only the 1200 R. P. M. motor is energized.

Fig. 1 structure Referring to Fig. 1, the system shown therein is in certain respects different from that shown in Figs. 3, 4, 6 and. 12, particularly in that all corrections of secondary clocks is made at the end of the first hour, or some other time interval, as manifested by the master clock,.that is, there is no repeated correction as in Figs. 3, 4, 6 and 12. Y

In this form of my invention the master clock and the secondary clocks, only one having been shown structurally are very much alike. That is, each includes a rotatable gear box containing reduction gearing including pinions I92, I84 and gears I93 and I95, the gear boxes G and G being preferably oil filled. This reduction gearing pref erably including suflicient friction or some worm gears, so that if the gear box is rotated and the synchronous motor whose rotor I96 projects from the gear box is not energized this rotor will be rotated at the same speed as the gear box, that is, will be stationary with respect to the gear box.

Referring to Fig. l the gear boxes G1 and G are pivotally mounted in stationary frames 1", F, F and F. To one end of these gear boxes is fastened a gear I40 or I! which is preferably of slightly larger diameter than the gear box dione on the bearings of the gear box is a motor shaft I4I or Ill on which is mounted the rotor ,IllBof a synchronous motor, these motors having been designated SM and SM. Concentric with and mounted within the other bearing of the gear boxes G and (i is a minute shaft (1 R. P. H.) designated I42 for the master clock and I42. for the secondary clock these minute shafts carry insulating cams K" and K respectively. f The gear ratio of the pinions I92-I94 and gears I93I95 within the gear boxes G and Gr is such that if these gear boxes are held stationary and the synchronous motors SM and SM are rotated at synchronous speed by current from the regulated frequency current source, the minute shafts I42 and I42 will rotate clock- -wise at a speed of one revolution per hour (1 R. P. H.).

The gear I40 of the master clock MC is at times, namely, during power failures, driven by any suitable escapement clock including preferin exactly the same way as synchronous motor SM may 'drive shaft I42 Operation Fig. 1

Normally, that is when alternating current of regulated frequency is available, the alternating current from the regulated source energizes the brake magnet I5l-I 55 and holds the escapement portion of the master clock M0 at rest. At the same-time the synchronous motor SM drives the shaft Hi and the cam K at 1 R. P. H. through the medium of the gear reduction I92I95 within the then stationary gear box G Also, this altematlng current of regulated frequency flows through contacts .I6II--I6I through the line L, through winding of synchronous motor SM", and through common return wire C back to the power line, and causes the shaft I42 and the cam K to be rotated at l R. P. H. When the master clock cam K reaches the 59:00 minute minute position the contacts I60I6I open and ably a pendulum I 44 having a magnetic bob J44,

an escape Wheel I45, a driven pinion I45,-and gear reduction means conventionally indicated by the pinion I48, and the gears I40 and I41. This escapement clock also includes'a main spring I50 anchored to a hand winding ratchet wheel I5I driving the gear I41. This ratchet wheel I5I is kept from unwinding by the ratchet pawl I52 and may be hand wound by the key I53. Suitable electric motor winding means such as shown in my prior applications above referred to may be used if desired. The pendulum I is normally, that is when alternating current is available, held at rest, or is braked, by the electro-magnet I54I 55 having its projecting legs surrounded individually by slugs or short circuited rings I56 of low resistance. The winding I55 of this electro-magnet isnormally energized by direct ourrent derived through the medium of a rectifier cessation in order that the shaft I42 may accurately indicate standard time after a current cessation. In this connection it is desired to point out that a synchronous motor of the kind contemplated, and in fact any commercial synchronous motor, will coast for a time so that it will not be stationary during the entire current cessation. It has been observed that such a synchronous motor will, if deenergized for one second,

be tardy only to the extent of about a half second.

The slugs I56 are of such resistance that a current cessation of say two seconds will cause the two pole rotor I 96 to coast thirty revolutions (one-- half second) and will cause the escapement clock to operate for one and one-half seconds.

Referring now to the secondary clock S of Fig.

1, the gear I40 is at times, namely when the sec-.

ondary clock is being-corrected, driven by an auxthe contacts I6IJI62 close. The secondary clock motor SM stops due to deenergization'of line wire L and if the secondary clock S was less than fifty-nine seconds fast the contacts I63-I64 of the secondary clock will not yet have opened. The application of the regulated alternating current frequency to the high wire H causes themotor M of the secondary clock to be operated to cause the minute shaft (1 R. P. H.) I42 to be driven at about sixty times normal speed. This high speed rotation of the shaft I42 and cam K will, however, only continue until the contacts IB3-I6 I operated by this cam K open. The secondary clock may therefore be slow as much as fifty-nine minutes and be brought to the end-of-hour position during the last minute of actual time as' indicated by the master clock. When the master clock now reaches the end-of-hour or sixty minute position, the contacts I 60-462 open and the contacts I60--I6I reclose after which the secondary clock will run in exact synchronism with the master clock until the fifty-nine minute position of both clocks is reached providing there has been no current cessation. If a current cessation occurs duringa certain hour and it does not exceed fifty-nine minutes the secondary clock will be corrected during the sixtieth minute of such hour. Obviously, if desired, corrections of longer outages than one hour may be corrected if the discs or cams K and K are driven by two hour or three hour shafts.

Fig. 1A illustrates how secondary clocks, such as shown in Fig. may be manually corrected. Let us assume that a person has tuned his radio set to receive the usual Arlington or any other time signal audibly over such set. He will depress the push button PB from one to several minutes before the end of the hour as a result of which all secondary clocks will assume the sixty minute or end of hour position. When he hears the sound manifesting the end-of-hour period he will release the push button PB as a result of iliary synchronous or induction motor M through the medium of a gear train including pinions I51 and I58 and gear I59. The gear ratio of this gear train is preferably such that if the motor M is operated at normal speed and the synchronous motor SM is deenergized, the shaft I42". will be rotated at about sixty times normal speed, that is, at 60 R. P. H. instead of l R. P. H. The synchronous motor SM may drive the shaft I'M whichall secondary clocks will again be operated at normal speed and will be correct. A plurality of secondary clocks may be connected in multiple and corrected in like manner.

Fig. 2 structure cept forthe addition of the rectifiers RF and RI and transformers T and T These rectifiers RI and R1 and transformers T and T are really filtering apparatus so that it can still be said that the secondary clocks of Figs. 1 and 2 are identical.

Referring to the master clock of Fig. 2, this clock is an escapement clock in which the pendulum is not dominated like it is in the Fig. 1 Ser. No. 239,538 construction, but is controlled or regulated so as to at times run faster or slower than its normal adjusted correct time measuring operating rate. In this construction there is preferably provided a permanent magnet PM which has leakage poles of soft iron I projecting inwardly from the poles of the permanent magnet. It is also provided with soft iron extensions I'll. This permanent magnet is placed directly below the pendulum I12 having a soft iron bob I12" and the pendulum is then adjusted to keep correct time. The leakage poles are provided with a sucking winding I13, so to speak, which is at times energized by direct current derived from the regulated alternating current system through the medium of a rectifier RI and flowing through the front contact I19 of relay R and the front contact I14 of the relay R The flowof this current is in such a direction through the winding I13 that the magneto-motive force produced thereby aids the magneto-motive force of the permanent magnet and causes a large part of the flux emitted by said permanent magnet to be diverted away from the pendulum so that gravity is no longer magnetically aided to any appreciable extent and the pendulum operates at a lower freouency. In a similar manner the soft iron extensions "I are provided with boosting windings I16 and I11 which when energized by direct current derived through the rectifier RI through the front contact I19 of relay R and the back'icontact I13 of relay R causes the apparent strength of the permanent magnet PM to be increased spring is fully wound the relay R and R' pick up and by closure of their front contacts I14 and I19 energize the sucking winding I13 thereby reducing from normal the downward pull on the pendulum I12. This causes the pendulum to run abnormally slow and causes winding motor SM", which was substituted for the windin motor SM when the relay R picked up, to

gain with respect to the escapement I12-I18,

resulting ln-the opening of Contacts I82-l88 -chronous" speed from alternating current of resulated frequency and will operate at exactly 3 thereby still further magnetically aiding gravity 1 and causing the, pendulum to operate at a faster rate or frequency. The windings I13, I16 and I 11 are when energized so poled as to aid the permanent magnet so as to avoid weakening of the permanent magnet as might be the case if they were bucking its magneto-motive force.

The relay R is so controlled that it is deenergized whenthe main spring I18 is esp cially fully wound up, that is, is wound up to a point where contacts I82I83 open, as it would be if the escapement did not quite keep up with the synchronous winding motor SM" and when deenergized it speeds up the escapement clock for reasons above given. The relay R is however also deenergized when the contact I82 is dead by reason of being out of contact with the contact pin I80. This control of the relays R and R is accomplished by connecting the pin I80 electrically to the gear I8l, which in turn is connected by the brush I86 directly to the out-put side of rectifier RI and by feeding either the spring contact I82 aloneor both of the contact springs I82 and I83 with energy from this If the main spring I18 is fully wound the contacts I8Ii--I82 are closed with contacts I82 and I83 still in engagement, thus energizing relays R and R, but if the main spring is slightly over-wound because the escapement I12--I15 is running slower than the winding motor, that is, is running slower than the cycle passage of the alternating current, the relay R drops although the relay R remains energized, thereby causing the pendulum to be speeded up. Putting this in different words, after a temporary current cessation both of the relays R and R are in retracted conditions. when the main R. P. H. when the high speed synchronous motor SM operates at synchronous speed from the regulated source of alternating current. The gear ratio from main spring gear IN to the shaft 233 is one to one, because gears IN and 234 have the same number of teeth and pinions 239 and 238 have the same number of teeth. In other words, when the pendulum I12 operates at correct speed and the winding shaft is rewound by the low speed synchronous motor SM" the shafts 242 and 233 operate at the same speed of 1 R. P. H. The master clock MC also includes a rectifier R1 for at times applying pulsating current of negative polarity to the secondary clocks.

Operation Fig.2

- R energized and through its front contact I energizing the low speed synchronous winding motor SM". The relay R will, of course, be

' at times energized and at other times deenergized to cause the escapement mechanism to run an average speed such that the contacts I82-I8I remain at the point of barely touching. Between the zero and the fifty-nine minute position of the master clock as reflected by contacts I81- I88I88, and by clock hand I 8|! pulsating current of positive polarity is derived from the regulated alternating current source through rectifier R1 and is applied to the line wire H -L This current is blocked by the rectifler RI but flows freely through the rectifier R1 and energizes the transformer T The secondary winding of this transforms turn has alternating current of the same frequency (60 cycle) induced therein, which alternating current energizes the synchronous motor SM". The pulsating current of course returnsto the source over the common return wire C As explained in connection with Fig. 1 the synchronous motor SM through gears Ill-I88 (see Fig. 1) drives the shaft I42 and the clock hand Ill exactly at the rate of l R. P. H. when sixty cycle current of regulated frequency isnpplied thereto, the gears I81I88II8 preferably having .sufflcient friction so that they will not'be rotated by motor SM".

I the normal rate.

upon reaching the secondary clock is blocked by the rectifier R1 but flows freely through the rectifier RI and energizes the primary windingof transformer T The secondary winding of transformer T in turn energizes the synchronous motor M or an induction motor, through a circuit includingcontacts l63- l64. This motor M drives the shaft I42 and clock hand l9] at substantially sixty times the speed they are driven by synchronous motor SM", so that the secondary clock may be driven to the sixty minute position where the contacts l63|64 open to stop motor M This occurs during the last minute of the hour as reflected by the master 'clock MC. That is, a clock that is slow to the extent of about fifty-eight minutes may be corrected. Also, a clock that is fast less than one minute will be corrected. At the end of the hour (sixty minute position) of the master clock the contact I81 also slips off of the cam K as a result of which contacts Nil-I08 close and contacts l8l-I89 open, so, that the secondary clocks all start from the sixty minute position in synchronism and operate again at It is thus seen that a fast clock'will be corrected and that even though a power failure of fifty-eight minutes occurs the secondary clocks will be advanced. Also, it will be noted since both of the windin s associated with the permanent magnet PM are deenergized during a current c ssation and also during the rewinding operation that the master clock will during this time, be adjusted to normal speed adjustment, and therefore will keep very good time. The indicating lamp I91 indicates when the secondary clock S is being corrected.

Fig. 3 structure The modification of my invention as disclosed in Fig. 3 of the drawings employs a somewhat difierent principle of operation than Figs. 1 and" 2, in that the correction of a slow secondary clock does not take place in the last minute of the hour as is true of the systems shown in Figs.

1 and 2, nor does it take place immediately after a that shown in. Figs. 1 and 2 where the master clock shaft operates continuously and continu- .ously manifests correct time as distinguished from the type where the master clock has its correcting contacts on the rewind shaft as shovm' in my above mentioned last filed application.

Referring to Fig. 3 the shaft 200 is preferably a minute shaft, rotating preferably at l R. P. H., of one of the master clocks shown in Fig. 1 or 2. This shaft is provided with suitable time indicating means shown conventionally by the minute hand 20!. This shaft 200 is provided with an insulated contact arm 202 rotating therewith and connected, as through the medium of a slip ring 205 and brush 206 to one terminal of a source of alternating current of regulated frequency, the other terminal being connected to a common return wire C To the end of this arm 2 02 is secured a wipe spring contact 203 which is in contacting relationship with the inside of one of.

the three twenty minute sectors X, Y and Z of an annulus. These three sectors are insulated from each other as by insulating joints 204 and are so shaped, as shown, that the spring contact 203 snaps from one contact to the other very quickly as the arm 202 rotates at 1 R. P. H.

The secondary clock S is provided with a similar annulus comprising three conducting sectors :c, y and z. The sectors X, Y and Z are connected to the sectors :c, y and 2 through the medium of wires II I, I I2 and H3 respectively. It is thus seen that sections X and a: have a source of alternating current potential connected thereto for the first twenty minutes of an hour. Furthermore, that sectors Y and y and Z andz have alternating current potential applied thereto during the second and third twenty minute period of each hour, respectively.

The secondary clocks S one having been shown conventionally and one having been shown to illustrate its principle of operation, each comprise a minute shaft 214 (1 R. P. H.) provided with suitable time indicating means, such as, the minute hand H5 (1 R. P. H.) and two contact arms 2l6 and 2|! provided with wipe contact springs 2H! and H9. These contact springs engage the inside of the annulus :c, y, z, and are angularly spaced 120 degrees apart so that spring 2l8 snaps from sector 2 to sector a: when spring 2|9 snaps from sector as to sector y. The arms 2l6 and 2 I! are insulated from each other. The arm H6 is connected to slip ring 220, whereas theiarm 2" is electrically connected to slip ring 22l. The slip ring 220 is connected to the low speed motor SM (1200 R. P. M.) through the medium of brush 222, whereas the slip ring 22! is connected to the high speed motor SM (3600 R. P. M.) through the medium of the brush 223. The other terminal of each of the synchronous motors SM and SM is connected to the common return wire 0 These synchronous motors are energized one at a time as hereinafter explained and through the medium of reduction gearing conventionally shown by the pinion 225 and the gear 226 rotate the minute shaft 2l4 at one revolution per hour when the synchronous tor SM is energized from the regulated source.

Operation Fig. 3

Referring to Fig. 3 it will be noted that alter- I nating current of regulated frequency is successively applied, for twenty minute intervals, by the master clock M0 to the stationary segments X, Y, and Z and to wires 2, 212, 2l3 in that order. It is also readily apparent that the secondary clock S is so constructed, if the master clock M0 shifts the energy from segment Z to segment X before the secondary clock has shifted its contact spring 2l8 from stationary segment 2 to stationary segment a: that the contact spring 2!!! will. still be in. contact with the segment a: and therefore the high speed motor, which may be a synchronous motor or an induction motor but is preferably a two-pole 3600 R. P. M. syn chro-nous motor, will be energized. If the high speed motor sM 'has a synchronous speed of 3600 R. P. M. and the low speed motor SM has a synchronous speed of 1200 R. P. M. then the secondary clock will near the end of every twenty minute period, as defined by the master clock, be

advanced to an extent of two-thirds of its tardiness. For instance, should the master clock MC shift alternating current energy from segment Z to segment X when the secondary clock is fifteen minutes tardy and its contact spring 2 l 8 assumes the forty-five minute position and the contact spring 219 assumes the five minute position the secondary clock S would run for a period of five minutes at triple speed or in other words would be only five minutes slow instead of fifteen minutes slow when the contact 2i8 snaps from segment 2 to segment r, after which time the secondary clocks again operates at normal speed until the master clock reaches the twenty minute position. In the next twenty minutes as measured off by the master clock MC the five minute tardiness of the secondary clock will be reduced for like reasons, to five-thirds minutes or one and two-thirds (1%) minutes. Such corrections will continue at reduced values until the secondary clock has been fully corrected. Also, it will be seen that if a secondary clock S should, for any reason, such as by reason of manual tampering, be fast from one second to nineteen minutes the contacts M8 and 2I9 would both be in contact with dead or deenergized segments, and therefore the secondary clock would stop until the master clock catches up with the secondary clock, so to speak. In other words, fast clocks that are fast less than twenty minutes when the secondary clock has its'contacts shift to new positions will be immediately corrected and slow secondary clocks that are slow less than twenty minutes when the master clock shifts current from one line wire to another will be corrected to the extent of two thirds of its then error in each twenty minute period until it is finally caught up.

Theoretically the secondary clock will never catch up but insofar as practical considerations are concerned it will catch up and be correct in about two hours. For instance, let us assume that a power outage occurs at the forty-five minute position of the master clock and all secondary clocks and that power returns at the end of the sixtieth minute. For reasons above given this fifteen minute tardiness is at twenty minute intervals reduced to the following values: V17, %1 and late minutes- Since $543 minutes is equal to one and one-fourth seconds the secondary clocks have, as a practical matter, been corrected within two hours after the termination of the current cessation.

Let us now assume that a current cessation occurs at the one minute position of the master clock and the secondary clocks and that this current cessation continues for thirty minutes, namely, when the master clock is indicating thirty-one minutes past the hour. The master clock M0 will, therefore, after the return of power continue to engage the segment Y for a period of nine minutes. During the flrstsix and one-third minutes of these nine minutes the contact 2l9 of the secondary clock will engage segment y as a result of which the secondary clock will operate at triple speed and will assume the twenty minute position when the master clock assumes the thirty-seven and one-third minute position. For the next two and twothird minutes the secondary clock will operate at normal speed and when the master clock reaches the forty minute position and shifts the application of energy from the segment Y to the segment Z the secondary clock S will be slow less than twenty minutes, namely, seventeen and one-third minutes, so that the tardiness of the secondary clock will thereafter be removed for reasons already explained. It is thus seen that under certain favorable time occurrences of current cessations a secondary clock .of tardiness greater than twenty minutes or even greater than thirty minutes will be automatically 'corrected. v

Let us now assume that the secondary clock S assumes the fifty-nine minute position when the master clock MC assumes the twenty-one minute position. The master clock contact 203 will therefore engage segment Y, whereas brushes 2" and N9 of the secondary clock en'- gage the segments 2 and 0:, respectively. During the next nineteen minutes of movement of the master clock the secondary clock will of course remain stationary. When now the master clock reaches the forty minute position and shifts energy from the segment Y to the segment Z alternating current can reach the low speed motor SM of the secondary clock S for a period of one minute after which the brush 218 of the secondary clock S shifts from segment 2: to segment 9:. This operation of the secondary clock again opens the circuit for the slow speed synchronous motor SM, and since motor SM is also deenergized the secondary clock S remains in the sixty minute position until the master clock MC also reaches the sixty minute position.

Under certain indicating conditions of the master clock a fast secondary clock, which is fast as much as thirty-eight minutes, will be stopped intermittently until it ia-in time indicating synchronism with the master clock. In practice it may be dimcult to so construct the secondary clock that the contact springs H8 and H9 snap from one segment to another simultaneously for this reason the contacts are preferably so constructed that the spring 218 snaps over a moment earlier than does the contact 2l9 so that the secondary clock cannot be stopped by reason of the spring 2l9 having moved off of a particular segment before the spring 2I8 has moved on such segment. In other words, it is preferable to have both of the motors SM and SM energized simultaneously for a moment rather than to have neither of these motors energized which might result in stoppage of the secondary clock for a twenty minute period.

Fig. 4 structure In Fig. 4 has been shown a modification of the clocksystem shown in Fig. 3. Since Fig. 3 shows in considerable detail one way how the contacts at both the master clock and the secondary clock may be made snap acting and how the segments with which the rotating brushes make contact may be insulated from each other these features of the present modification will not be specifically shown but will instead be conventionally illustrated. In the system shown in Fig. 3 three" control wires and one common return wire arerequired, whereas in the Fig. 4'

construction the line wires have been reduced .to two control wires and one common return wire. Also, in the construction of Fig. 3 a tardy secondary clock can be corrected only to the extent of a predetermined fraction of its entire tardiness in each predetermined time period an hour whereby corrections of a tardy clock are made much quicker especially where the tardiness is not in excess of forty-five seconds.

Referring to Fig. 4 the master clock MC may be identical to the master clock M except for the provision of only two stationary segments A and B instead of three such segments, these two segments suspending substantially equal arcs of 180 degrees, whereas the segments of master clock MC suspend arcs of 120 degrees. As shown this master clock M0 also includes a contact arm conventionally shown by an arrow 230 connected to and driven in a clockwise direction by a suitable master clock mechanism such, for instance, as illustrated in Fig. 1 or 2 of the drawings The master clock shaft 231 (1 R. P. H.) drives suitable time indicating means as conventionally shown by the clock hands 232 and 231 driven thereby. The rotatable contact arm 230 is connected to one'terminal of a source of frequency regulated alternating current, as through the medium of a slip ring and brush 235-435. This source has been conventionally illustrated by the transformer T which has its other secondary terminal connected to a common return wire 0.

The secondary clock S two such clocks having been shown, is of the same general construction as that shown in Fig. 3 but differs therefrom in the provision of two stationary segments insteadof three and in having these segments constructed to perform special functions not performed by the system of Fig. 3, and in the further departure in construction whereby the two contact arms conventionally illustrated by arrows 24!] and 2 operate in different planes and engage different paths over the stationary segments a and b, these paths having been shown current cessation takes place for an hour thereassumes the fifty-nine minute position and for its low speed arm 240 enter upon dead segment by dotted lines. The stationary segments A and stationary segments B and b are connected by a line wire 243. The clock hands 246 and 241 are driven by the minute shaft (1 R. P. H.) 245, which minute shaft is driven by a synchronous motor SM or SM", through the medium of a gear train conventionally shown by the gear 248 and thepinion 249. The stationary segments a. and b are so shaped and the contact arms 240 and 2 engage these sectors overr such paths that the ,low speed arm 240 engages segment a between the fifty-nine minute and thirty minute position of clock S and engages segment b between the thirty and the fifty-nine minute position. The high speed arm 24l engages the segment a between the thirty minute and the fifty-nine minute position and engages the segment b between the fifty-nine minute and the sixty (zero) minute position and also between the one ininute position and the thirty minute position of the secondary clock 8*. The low speed arm 240 is connected to the low speed synchronous motor SM (synchronous speed preferably 1200 R. P. M.) through the medium of slip ring 255 and brush 256, whereas the-high speed arm 24l is connected to the high speed synchronous motor SM" (synchronous speed preferably 3600 R. P. M.) through the medium of slip ring 253 and brush 254.

' Operation Fig. 4

Let us first assume that the secondary clock 5 is correct and that the master'clock MC and the secondary clock both assume the forty-five in exact time synchronism with the master clock,

a, but at the same time has its high speed arm 24f .enter upon live or energized segment b, it formerly having contacted with segment a. If desired the contact structure for secondary clock 5 may be such that there is a slight overlap in contact making, that is, the contact arms 24!! and 2 are make-before-break except when the contact arm 2 enters the cut-away portion or insulation 25L This, the engagement of contact 2 with energized segment b, causes the low speed motor SM to be deenergized and causes the high speed motor SM" to be energized, so that the secondary clock 8* operates at triple speed and will therefore reach the sixty minute position when the master clock reaches the fiftynine minute twenty second position. The low speed arm 240 will also have moved upon segment a at the fifty-nine minute position of the secondary clock, which segment a is still deenergized. When the secondary clock S reaches the zero position the high speed arm 2 will move upon insulation or notch 25L which will also not supply any current so that both of the synchronous motors SM and SM are deenergized and the secondary clock stops. wait of forty seconds the master clock M0 removes the source of alternating current from segment B to segment A and correspondingly from segment b to segment a. This causes alternating current to be again applied to the low speed synchronous motor SM For the next thirty minutes the secondary clock will remain at the end of which time the low speed arm 240 will snap from segment a to segment b simultaneously with snapping of the arm 230 from segment A to segment B. It is apparent that the high speed arm 2 isnot in contact with the segment a between the zero and thirty minute position and that it is not in engagement with segment b between the thirty minute and fifty-nine minute position, so that with the secondary clock running at correct time the high speed motor remains deenergized between the zero minute and the fifty-nine minute position. In other words if a secondary clock is tardy to the extent of forty seconds or less just before the end of the hour the secondary clock will be minute position and that no power failure or advanced to indicate correct time to the second at the end of the hour. It is also apparent that a fast clock will be corrected because he con tact arm 2 will drop into notch?? a little earlier and the secondary clock will en be held at stop until the contact arm 23!] ofthe master clock snaps from segment B to segment A.

Let us'now assume that at the thirty-two minute position of shafts 23! and 24,5 and clock hands 232 and 246 a temporary current cessation occurs, and that this current cessation continues for twenty-six minutes. The master clock will, upon resumption of alternating current flow, indicate flfty-eight minute's, whereas the clock hand 246 of the secondary clock will still indicate thirty-, two minutes. For a period of two minutes the master clock applies current to segments B and b. During these two minutes" the secondary clock advances at the normal rate to the thirty-four After aminute position. As the contact arm 230 of the master clock MC snaps from the segment B to the segment A current is removed from the low speed synchronous motor SM and is applied to the high speed synchronous motor SM": This will of course cause the secondary clock to operate at triple speed. This will continue for a period of eight minutes and twenty seconds, namely, until the master clock MC has reached the eight minute, twenty second, position and the secondary clock S has reached the fifty-nine minute position. The secondary clock has thus picked up sixteen minutes and forty seconds and is still nine minutes, twenty seconds, slow. With the secondary clock assuming the fifty-nine minute position the high speed contact 2 passes of! of the segment a and onto the segment I) and therefore the high speed synchronous motor SM will be deenergized. The low speed arm 240 however at this instant moves from the segment 1) upon the segment a as a result of which the low speed synchronous motor SM is energized. The secondary clock 8 will now operate at normal speed and when the master clock M assumes the thirty minute position the secondary clock will' assume the twenty minute, forty second position, that is, is still nine minutes, twenty seconds slow. At this instant the master clock MC removes alternating current from the segments A and a and applies it to segments .8 and b by snap action contacts such as shown in Fig. 3. This switching of alternating current from segment a to segment b causes the low speed motor SM to be deenergized and causes the high speed motor SM" to be energized, so that the secondary clock again operates at triple speed, but only for a period of one third of nine minutes and twenty seconds, that is, for a period of three minutes and six and two-thirds seconds, at which point in the operation the contact arm 24! of the secondary clock, namely, the thirty minute position of the secondary clock, passes from segment b to segment a and contact arm 240 passesfrom segment a to segment b. The secondary clock will now operate at normal speed and since it has picked up six minutes and thirteen and onethird seconds it is still tardy or late to an extent of three minutes and six and two-thirds seconds. When the master clock reaches the sixty minute (zero) position the secondary clock will reach the fifty-six minute fifty-three and one third secend position. The master clock will now shift the alternating current supply from the segment B to the segment A, and of course also from segment b to segment a. This will cause the low speed motor BM" to be deenergized and the high speed motor SM" to be energized, but since the insulation at both the top and the bottom between segments a and b makes a one minute jog the high speed arm moves upon the segment I) at the fifty-nine minute position or one-third of two minutes and six and two-thirds seconds (42% seconds) later, at which time the secondary clock has gained one minute and twenty-four and utes plus one third of one minute and 42% seconds) the secondary clock will reach the thirty minute position at which point the contact arms 240 and 2 switch about on the segments a and b and the secondary clock again operates at normal speed. The secondary clock will have gained one minute 8%, seconds and is still 34 and seconds late. When the master clock reaches the 59 minute 34 and second position the secondary clock reaches the 59 minute position at which point low speed contact arm I" shifts onto dead segment a and high speed contact arm 24 shifts onto the hooked part of live segment b, thu operating the secondary clock at triple speed. In the next twenty seconds of operation of the master clock the high speed contact arm 2 will drop into the notch 25l with the secondary clock assuming the sixty minute (zero) position and this occurs at 59 minutes 54 and seconds and before the master clock MC assumes the even hour zero minute position. The secondary clock is now 5 and seconds fast. The secondary clock will then remain at stop until the master clock reaches the even hour position and again shifts the alternating current from the segment 12 to the segment a. In other words, the secondary clock has been fully corrected.

In view of the above discussions of the operating characteristics of the systems shown in Figs. 3

and 4 it is believed helpful to express by formula how a slow clock is corrected in terms of the total tardiness. Let us assume that X is the extent of the tardiness of a secondary clock in minutes, and that each expression on the opposite side of the equation expresses the amount of correction that will bemade in that order. For all cases in the Fig. 3 construction where each segment spans an arc of degrees where w is infinity. The tardiness X of the secondary clock must of course not be so large that the master clock will energize the segment of the secondary clock in advance of the one engaged by contact spring N9 of the master clock of Fig. 3, for when that occurs the secondary clock will stop until it is slow exactly one hour.

If Fig. 4 were modified to employ segments for the secondary clock such as shown in Fig. 5 then the above formula would apply, but the successive corrections would be made thirty minutes apart instead of twenty minutes apart as is true of the Fig. 3 construction. Referring now to the system shown in Fig. 4 it will be noted that the high speed contact 2 shifts at the bottom (namely at the full hour position) one minute earlier (59 minute position), so that only two thirds of the whole tardiness minus one minute can be corrected at each end of an hour. In view of this difference the above formula must be modified to read for those cases where the current cessation takes place in the second half of an hour as follows:

-;-{of last correction used] Simplifying this expression it reads:

: +1]+%[1ast correction used] If we now assume the secondary clock S indicates somewhere in the second half of an hour and is twenty-six minutes slow, the five successive corrections by substituting for X in the above formula will be as follows, where m and-s signify minutes and seconds respectively:

If we now assume that a current cessation of forty-one minutes takes place at say the thirtyone minute position of the secondary clock then the successive corrections as indicated by the above formula will be as follows:

The above formula (2) is useful if the power failure occurs in the early part of the second half of the hour. For outages that occur shortly after the even hour the following formula must be used:

This may be simplified to read v +%[last correction used] If we now assume that a current cessation occurs at say three minutes after the hour and continues for twenty-six minutes the several correc- It will be noted that the fourth and fifth ex pressions were not used. The reason for this is that the special end-of-hour correcting means by the application of current to the high speed motor SM" during the fifty-ninth minute of the hour is capable of making a maximum correction of forty seconds. clock is at 59m 4 0s it can advance the secondary clock 5* forty seconds during the remaining,

twenty seconds in the fifty-ninth minute. In other words, if the advance in any odd advancing period is less than eighty seconds all the remain-' ing expressions except the last in Formula 3 will be omitted. The same is true of Formula 2 as to %[last correction used] This is true because if the master flast correction used] If we now, with a speed ratio of six to one, as-

sume that a current cessation takes place in the early part of the first half of an hour and that this cessation continues for ten minutes, and we substitute in the last above mentioned formula the successive corrections will be as follows:

(so X=8m20s+33 s+55%s +11%s='1om If. we now assume a current cessation of twenty-eight minutes at the thirty-two minute even instead of odd advancing periods. ,If we now assume a current cessation of two minutes occurs in the first half of an hour, using Formula 3,

the advances made -by the secondary clock will be: 1m 20s and 40s=2m. a

It should be understood that each of the three above mentioned formulae assume synchronous hour.

position of a secondary clock having motors of a speed ratio of 8 to 1 Formula 2 will become:

and substituting 28 forXwe'have:

In other words the secondary clock will only be tardy 32 seconds an hour after the current cessation started, that is, a half hour after the current cessation terminated, and will be fully corrected one hour after the current cessation terminated. I

If a current cessation takes place at such a time that the first correction in the formula cannot be made then the correction that is actually made by the structure of Fig. 4 will be subtracted from the total tardiness and then the proper formula will be used for the remainder. For instance, let us assume that with the Fig. 4 construction a current cessation of fifteen minutes is started at the twenty-seven minute'position of the master and secondary clock. When power comes on the secondary clock will advance two minutes during the first minute that ourrentis available. The remaining error will be thirteen minutes and by substituting 13 in Formula 2 since the secondary clock is now operbe corrected. Let us now assume that clock 8* is fast two minutes during the first half of an At the twenty-eight minute position of the master clock MC the secondary clock 8 shifts from the, low speed motor to the high speed motor and during the next two minutes seconds and then contact 24!! remains in the zero minute position on dead segment a with contact 2 in notch 25| until the master clock has also reached the zero minute position.

Fig. 6 structure In the system shown in Fig. 6 the master clock is identical to the one shown in Fig. 2 except that alternating currentis applied to the two control line wires 248 and 249 alternately. in half hour intervals by the contact arm 250, as also shown in Fig. 4, and except for the further modification including back contact 259 of relay R. which connects the two control line wires 248 and 249 together during high speed rewinding operation of the master clock as manifested by deenergization of the relay R Furthermore, the secondary clock employed in the system of Fig. 6 is identical to the secondary clock of Fig. 4, for which reason like parts of Fig. 6 also shown in Fig. 2 or 4 will be assigned like reference characters as already used in Figs. 2 and 4. In the structure of Fig. 6 alternating current is derived from a source of regulated frequency, preferably sixty cycle, which has been conventionally illustrated by the transformer T Operation Fig. 6

as it will be when the relay R. is in its deenergized condition while alternating current is available, that is, after each current cessation being energized through back contact I85 of relay R, the relay R being deenergized because conand for a time proportional to the duration of such cessation. The synchronous motors SM and SM" of Fig. 6 have such relative torque that the high speed motor SM" dominates when both motors are energized. In other words, the secondary clock S operates at triple speed while both of its motors are energized, operates at triple speed when the motor SM" only is energized and operates at normal speed if only the low speed motor SM" is energized. It is thus seen that after a current cessation the secondary clock will operate at triple speed so long as alternating current is available and the relay R is deenergized, and this is for a period equal to half of the timeof the current cessation since the high speed winding motor SM of Fig. 2 operates at triple the speed of winding motor SM" or the winding operation catches up, so to speak, at double speed. In other words, since the high speed and low speed motors SM" and SM of Fig. 6 have synchronous speeds like the high speed and low speed winding motors SM" and SM of Fig. 2 the shaft 245 of the second ary clock of Fig. 6 operates substantially in syn- I half minute .position.

tacts I and I82 are not in contact with each other. Also with relay R deenergized its back contact 259 connects (see Fig. 6) line wires 248 249 together as a result of which both of the contact segments a and b of the secondary clock S have potential applied thereto. During the first minute of the return of current on the alternating current system the low speed synchronous motor SM only of the secondary clock S will be energized. This is true because the contact arm 2 will be in the notch 25! durin the first minute of operation as manifested by the secondary clock S and this secondary clock will operate at normal speed. The rewinding opera? tion of the master clock will take place at triple speed so that the rewind shaft 242 is only fiftythree minutes tardy, whereas the secondary clock S is still fifty-five minutes tardy. During the next twenty-six and one-half minutes of operation of the master clock MC the contact I82 01' this master clock will have caught up with the pin I80 because it gains two minutes for every minute of.operation when the high speed rewind motor SM (see Fig. 2) is energized. During the next nineteen and two-thirds minutes of operation as measured by the master clock MC the secondary clock S runs at triple speed and gains two minutes for each minute of operation so that it has gained thirty-nine and one-third minutes.

when its shaft 245 has operated through an arc of fifty-nine minutes and again indicates the sixty minute (zero) position. The secondary clock is now only fifteen and two-thirds minutes tardy. During the next minute of operation 01' the master clock MC the secondary clock S does not gain with respect to the master clock MC, because only thelow speed synchronous motor SM" is energized the contact arm 2 again being in the notch 25!. The fifty-five minute tardiness of the rewind shaft 242 (see Fig. 2) has now been corrected to the extent of forty-three and one third minutes and is still tardy to the extent of eleven and two-thirds minutes. During the next live and five-sixths minutes of operation of the master clock MC the main spring I'll is fully wound up and the relay R is energized and the shunt is removed from the line wires 248-249 by the opening of back contact 259. Also during this live and flve-sixths minutes of operation of the master clock MC the secondary clock S gains twice this amount making a gain of eleven and two-thirds minutes or a total gain of fifty-one minutes. The secondary clock S is therefore only four minutes late or tardy at this time,

'namely, when the master clock MC assumes the twenty-twoand one-half minute position and the secondary clock S assumes the eighteen and one- These four minutes of tardiness of the secondary clock S will now be corrected in precisely the same manner as was Y described in connection with the system shown in Fig. 4. It is readily seen from the foregoing discussion that had theassumed power failure of fifty-five minutes occurred one minute later the secondary clock would only have been tardy two minutes instead of four minutes when the master clock was fully rewound, because the secondary clock would have had its contact arm 2 pass over the notch 25I only once during the rewinding operation of the master clock MC. It should also be understood that the feature of connecting together the line wires, such as wires 248 and 249- by contact 259, during the rewinding operation may also be employed when the contact making structure such as shown in Fig. 5 of the drawings is used.

Reviewing the structure of Figs. 3, 4, 5,6 and 12,

the systems shown therein employ the principle of correspondence and non-correspondence.

When a secondary clock is tardy or late the low speed motor is not switched to a new circuit as early as energy is applied to such new circuit by the master clock and non-correspondence exists.

l ig. 12 construction and operation Instead of employing a back contact 259 of the relay R of Fig. 6 for connecting the control line wires 248 and 24!] together pole changer contacts 6 by having contact arm 250 mounted on the rewind shaft 242 instead of on the main minute shaft 233. Let us, for instance, assume that at the ten minute position of the master clock and the secondary clock'a current cessation of fifteen minutes takes place with the Fig. 6'construction modified as illustrated in Fig. 12. Upon termination of the current cessation, the relay R will remain deenergized for reasons explained in con-' nection with the-master clock construction of Fig. 2. The contact arm 250 of Fig. 12 and the contact arm 240 of its secondary clock (not shown but see Fig. 6) will both assume the ten minute position. With the contacts 330 and 331 of the relay R in their retracted position the segments A and b will be connected together, as a result of which the synchronous motor SM" will receive energy from segment'b through the medium of contact arm 24!. ,Forthe next seven and onehalf minutes of actual time the rewind motor SM (see Fig. 2) and the synchronous motor SM" (see Fig. 6) will be energized, the relay It being deenergized. At the end of this seven and one-half minute period'the relay R picks up and the low speed rewind motor SM" is substituted for the high speed rewind motor SM and the segment A and B are reconnected to segments a and b respectively, as a result of which the secondary clock, since it operated at triple speed for a period of seven and one-half minutes, has fully caught up and now again. indicates substantially-correct time. If a secondary clock should be slightly in error it will be corrected at the end of the hour asexplained in connection with the Fig. 4 system. If desired however the contact arm 250 of the Fig; 12 system may be driven by the shaft 233 instead of the rewind shaft 242. In the Fig. 12 construction therefore correspondence between contacts 253 and 240 has artiflcially been changed'to non-correspondence so that insofar as circuits are concerned non-"correspondence exists, so that the high speed motor, unless its contact arm is in the notchor dead "one revolution per minute. at 33 and having a lug 32 has its lug engage the position 25l, will be connected in the circuit to which energy has been supplied and the secondary clock will gain so long as the contacts of the secondary clock remain out of correspondence with the master clock contacts.

Fig. 7 construction and operation In Fig. 7 has been illustrated how a continuously operated one revolution per minute shaft movement of any one of the secondary clocks of Figs. 1, 2, 3, 4, 5 and 6 may be converted into an intermittently operated one revolution per hour shaft movement. Such an intermittently driven minute shaft (1 R. P. H.) is desirable where the secondary clock is employed to record or register time in suitable intervals preferably minute intervals. In the construction illustrated it is proposed to register minute intervals bythe type wheel 30. In the construction shown the shaft 3| is operated by the synchronous motors of one ofthe secondary clocks shown in Fig. l, 2, 3, 4, 5 or 6 in a clockwise direction and at a speed of The arm 32 pivoted cam 34 keyed or otherwise fastened to the shaft This arm 32 has pivoted thereto a pawl 35 so shaped that it will engage the teeth of the ratchet wheel 36 and when it has operated this ratchet wheel 36 an are equal to one ratchet tooth this pawl will bind under the pin 31, so as to avoid overthrow. That is, to avoid the ratchet wheel 36 being turned more than one tooth onesixtieth of a revolution for each rotation of the shaft 3|. The arm 32 is biased to the right by a spring 38 and the'pawl 35 is biased down by the spring 39. The holding pawl 40 is pivoted to a stationary support by a pivot 4| and is urged in engagement with the ratchet wheel 36 by a spring 42. From the construction illustrated in Fig. '1 it is readily seen that during the major part of each revolution of the shaft 3| the arm 32 is gradually moved toward the left and that at the' end of each minute, or other suitable interval, the lug 32 slips off of the cam 34 thereby causing the ratchet wheel 36 to be advanced in a clockwise direction six degrees, or an amount equal to one minute. This wheel 35 operates the type wheel 30, and for each operation of the pawl 35 advances this type wheel to the next minute number. This type wheel may through suitable means operate other type wheelsintermittently,

once for each type character thereon, to indicate the hour of the day, the day of the week or month, and the like. a

Referring for a moment to the rotatable mechanism housings G andG shown in Figs. 1 and 2 instead of having the rotor l96 on a shaft l4l projecting from the housing and having it driven by a stationary stator 5M or SM the stator may also be located entirely within the housing and rotated therewith when the housing is rotated. In this case slip rings engaged by stationary brushes are preferably connected to and insulated from this housing. This latter construction' would permit a smaller air gap to be used and would permit the rotor l96 to be contained within the oil contained housing G or G.

Motor structure In Figs. 8 and 9 have been illustrated one form and in Figs. 10 and 11 have been illustrated an- "other form of double motor, including each a low speed stator and rotor and a high speed stator and rotor, wherein both rotors are secured to the same shaft or sleeve and supported by the same bearing structure.

Structure and operation Figs. 8 and 9 Fig. 8 shows the preferred form of double motor in cross-section and Fig.9 shows an exploded isometric view of the same motor. In this double motor the two pole rotor 269, which is preferably made of soft iron or steel, is press mounted on the same sleeve 26! with the six pole rotor 262 made of the same material as the rotor 269. Each of these rotors 269 and 262 has associated therewith a hysteresis cup 264 of very thin sheet steel having an outside diameter equal to the outside diameter of its associated rotor armature 269 or 262. These steel cups are made of permanent magnet steel or other permanent magnetic material and are primarily used to produce starting torque when a cup is at rest or is rotating at less than synchronous speed. The two rotors 269-264 and 262-264 are .held apart on the sleeve by a second sleeve 265. The sleeve 26! has gear teeth 399 out therein near one end for driving a gear train including the gear 261. The sleeve 26! is mounted for rotation on the spindle 268 fixedly secured in the housing including end plates 269 and a circular box 219.

The double stator comprises disks 21!, 212, 213 and 214 of soft iron and disks 215, 216, 211, 218 and 219 of copper or other conducting material of low resistance. Of these disks the disks 214 and 219 are provided with a rather small central opening, the copper disks 216, 211 and 218 are provided with a slightly larger central central openings in the copper disks 216, 211 and 218 are made smaller than the central openings in iron disks 212 and 213 in order to more citiesciously screening the iron disks 212 and 213 from each other and from the rotors 269264 and 262-264. Between the disks 215 and 216, and around the outside of the pole pieces 288, 284, 285, 281,288, 289, 294 and 295 thereof, is mounted the low speed coil 289 and between the disks 218 and 219. and around the pole pieces 296, 291, 298 and 299 thereof, is mounted the high speed coil 28!. The casing 219 is constructed of'iron and constitutes, at certain points, the magnetic circuit for each of the two motors. That is, the low speed coil 289 surrounds the three poles or pole pieces 283, 284 and 285, conveniently called north poles, and their associated shaded poles 281, 288 and 289 respectively. These six pole pieces are securely fastened in the iron plate or disk 21 I. The copper disk 215 is provided with holes into which these pole pieces fit snugly so as to furnish a low in magneto-motive forces in the twelve poles lying axially in the opening thereof, but this will result in very little magnetic flux passing directly endwise through these pole pieces from one iron plate 21! to the other iron plate 212. This is true because the copper plate 216 shields the iron plate 212 magnetically from the pole pieces 283, 284, 285, 281, 288 and 289 and similarly shading is afforded by the copper plate 215 between the iron plate 21! and the six south poles including pole pieces 294 and 295. The net result is that a six pole motor has been constructed in which the magnetic pole shoes are fed magnetically from the ends thereof instead of radially as in the more common construction. The magneto-motive forces thus cause magnetic fluxes to pass first from. the unshaded north poles to the unshaded south poles and then from the'shaded north poles to the shaded south poles, and these fluxes find the path of least reluctance tobe through the rotor 262-264. These successive fluxes alternating in polarity and shifting in position produced by alternating current passing through the winding 289 results in a rotating magnetic field which tends to drag the steel cup 264, associated with the six lobe disk 262 with it substantially up to a speed of synchronism, at which point the lobes or points of this disk 262, which may be constructed of soft iron or steel, fall into step with the magnetism and rotate in synchronism with thi magnetic field. Since there are three pairs of unshaded poles the rotor will run at twelve hundred R. P. M.

v with sixty cycle applied to the winding 289.

energized by alternating current of sixty cycle resistance path for eddy currents flowing around 284 and one unshaded pole- 295 of these six poles have been illustrated and these two south poles 294 and 295 are located between the north poles 285 and 281. The shaded south pole 295 is shaded by the copper disk 218. It is readily seen that energization of the low speed winding will result frequency. Since the high speed synchronous motor 269-28! is used for the purpose of allowing a tardy secondary clock (see my prior application Ser. No. 239,538) to catch up suitable con- 7 tact means controlled by the secondary clock is preferably employed. And although this contact means may be of the construction shown in Figs. 3, 4 and 6 the contacts 88! controlled by the insulating cam 892 driven by gear 261 has been !1- lustrated. These contacts 39! open the circuit at. predetermined chronological conditions of the secondary clock so that the clock will stop until the low speed motor winding 289 is energized. A single motor of the construction shown in Fig. 8 is preferably used within the gear housing G or (3' (Figs. 1 and 2) when it is desired to use a motor mounted wholly within such gear housing as pointed out hereinbefore, in :Zyhh event slip rings and brushes will be used energize such motor for any position the gear housing may then beassuming.

In Figs. 19 and 11 have been illustrated another form of doublesynchronous motor also designed to operate at 1299 or 3699 R. P. M. 'depending on which of its two windings is energized, and having both of its rotors secured to the same shaft 8. From the clock gear housing 8" is projecting the shaft 8!! to which are secured the rotors M2 and M8. The two pole rotor 8!2 is preferably of a construction the same as that of the rotor of synchronous motors SM", SM", BM", SM and SM", which comprises a very thin disk of tempered steel punching, the punching having holes punched therein to leave two spokes and a rim, the spokes being 180 apart. This construction results in low reluctance through the rotors in one direction and comparatively high reluctance at a right angle to such direction through the plane of the disk. When this rotor reaches its synchronous speed the steel disk be-- comes a permanent magnet having its flux divided between the end-to-end spoke and the two substantially parallel rim portions, and this permanent magnet locks itself into the rotating magnetic field and therefore runs in synchronism -with the rotating field. The high speed stator 3 has only been shown in Fig. 11 but isof a construction such as the stators of the synchro-' nous motors SM, SM, SM, SM and SM except that the shaded pole of one polarity is substantially in contact with the unshaded pole of the opposite polarity. This latter construction produces a heavier lagging flux in the shaded poles. These rotors 3l2 and 3l3 have been omitted from Fig. 10. in order to more clearly show the six pole low speed stator 3l5.

The six pole rotor 3l3 is punch-and-die formed in a shape such as illustrated in cross-section in Fig. 11 and is constructed of tempered steel having high permanenqe so that when magnetized it acts like a permanent magnet. This permanence is, however, not so high that it cannot here-magnetized by the stator, this in order to make it act like a hysteresis disk to afford starting torque when the rotor is started from rest. It will be noted that the shape of the rotor is such as to afiord an external cylindrical surface lying within the projecting stator poles of the stator 3| 5 and to afford an internal cylindrical surface to cooperate with the outside surfaces of these stator poles.

This stator 3l5 comprises a central, preferably laminated, core 3l5 to one end of which is secured a soft iron spider M6 and to the other end of which is secured a soft iron spider 3". These spiders. 316 and 3|! have their projecting poles bent at right angles to the plane of such spider, as illustrated, so as to all lie in the same cylindrical plane of a diameter to fall midway between the two cylindrical planes of the rotor M3. The poles are held in position by a ring 320 of copper, or other metal of low electrical conductance, having twelve rectangularly shaped holes therein. Alternate ones of these holes are slotted as shown by the slots 32L The slots are duce a rotating magnetic field in' the rotor 3|3 rotating at 1200 R. P. M. In order not to rely on the residual magnetism of the rotor 3l3 alone for obtaining synchronous speed operation radial slots are cut into this rotor 3i3 substantially as shown for the rotors of synchronous motors SM, SM and SM. It is thus apparent that if the winding 325 of the stator 3i 5 is energized by alternating current of sixty cycle frequency the shaft 3| I will be driven at 1200 R. P. M., whereas if the winding of the stator 3|4 is energized by such alternating current the shaft 3 is rotated at 3600 R. P. M. It is, of course, understood that the stator 3l4 includes shading coils such as illustrated for the synchronous motors SM SM, SM, SM and SM" and that the stator will be so placed on the rotor that both of the .rotors Y '3l2 and 3|3 will rotate in the same direction.

provided so as to render the poles passing through the holes to which these slots are cut nonshaded. It is thus seen that if we, for convenience, call the right-hand end of core 3|5 a north pole and the left-hand end a south pole that each of the iron poles projecting from spider 3 i6 are north poles and the poles projecting from spider 3|! are south poles. It is also apparent from Fig. 10 that alternate north poles are shaded and the remaining ones are unshaded and that that is also true of the south poles projecting from spider 3|]. Also that shaded north poles lie closer to unshaded south poles-than do shaded south poles. This latter construction is resorted to in order to increase the lagging flux emitted from the shaded poles especially during the latter part of each magnetic flux wave. The north and south poles heretofore mentioned are produced by energization of the winding 325 surrounding this core 3l5. This winding is in practice energized by alternating current preferablyof sixty Fig. 13 construction and operation In Fig. 13 has been illustrated a twocircuit two speed single stator single rotor synchronous motor 25M that may be substitutedfor any one of the double units SM -SM (Figs. 2; 6 and 12); SM SM SM ---SM (Figs. 3, 4, 6 and 12). q

This two-speed synchronous motor 28M" comprises two generally U-shaped stator cores 340 and 3 constructed of soft iron laminations. One pole, namely, the rearward pole with respect to the direction of rotation, of each of these U-shaped cores 340 and 34! is bifurcated and provided with a shading coil 342 to cause such direction of rotation. The ends of the poles of these U-shaped cores 340 and 3 are rounded to leave a small uniform air-gap between them and the tempered steel rotor 345 and are so spaced as to constitute a four pole construction in which alternate poles are shaded for the same polarities we have a typical two-pole motor stator of which each pol belongs half to one core 340 and half to the other core 3 and which two poles each has a single shading coil to produce clock-wise rotation of a magnetic field. This two-pole magnetic field rotating in a clockwise direction produces hysteresis torque in the rotor 345 tending to drag this rotor with it. As the rotor approaches its synchronous speed of 3600 R. P. M. the rotor due to the path across it of low reluctance and including the two spokes in series, having in multiple therewith two rim portions, locks in with this magnetic field, so that the rotor operates at 3600 R. P. M., assuming a sixty cycle alternating current source.

If now the stator cores 340 and 34! are so magnetically excited from such a source of alternatingcurrent that adiacent poles of different cores have opposite instantaneous magnetic polarities we have a four-pole stator of which two adjacent poles belong to one core member 340 and the clockwise rotation for a, particular magnetic wave of a magnetic cycle; This four-pole magnetic field will of course rotate only at a speed of- 1800 R. P. M. and will tend to drag the rotor 345 with it. When the rotor 345 approaches synchronous speed it will lock in, so to speak, with this rotating magnetic field. This locking-in effect is produced by the four slots 346 out radially into the rotor 345 from the outside and causes the rotor to operate at 1800 R. P. M.

In order to increase the amount of alternating current flowing in the shading rings 342 and correspondingly increase the lagging magnetic flux produced thereby the pole pieces are provided with extensions of magnetic material 340 and 34H. By looking at the stator structure of Fig. 13 it will be seen that if the stator is magnetized to produce a two-pole magnetic field the usual shading is afforded but that when the stator is magnetized to produce a four-pole magnetic field only two of the four poles are provided with shading coils. This has been done purposely, because if the other two poles had been bifurcated and shading rings had been provided these additional shading rings would have produced harmful effects when the magnetic structure is excited to produce a two-pole magnetic field, in that such additional shading rings would lie in the middle of the unshaded portion of each of the two poles.

In order to produce two-pole or four-pole magnetization of the core structures 340-341 the core 340 i preferably provided with a plane helical coil 341 and the core 3 is provided with a helical coil 348-349 having a center tap 350. This center tap is preferably connected to one terminal of the coil 341 the other terminal of this coil 341 being connected to the common wire in the particular system in which the motor 2SM is used. Each of the coils 341, 348 and 349 preferably has the same number of turns so that the magneto-motive force from pole to pole of the two cores 340 and 3 is the same irrespective of which of the two circuits is energized. It is thus seen that if alternating current is caused to flow from the wire low to the wire.common four-pole magnetization will result causing the rotor to operate at 1800 R. P. M., but if alternating current is caused to flow from the wire high to the wire common two pole magnetization results, the magnetic polarities for four-pole magnetization and for two-pole magnetization of the core 34f having been illustrated by the solid letters N and S and the dotted letters N and S, respectively. Under normal conditions the motor 2SM will be energized to constitute a four-pole motor, but it will be energized to constitute a two-pole motor when a secondary clock is to be advanced or a main spring is to be wound up at double speed.

If the motor 253M is substituted for the winding motors SM and SM the wire low will be connected to front contact I35 of relay R whereas the wire high will be connected to back contact I85 of this relay. The gear ratio of the winding gears will remain the same but the time required for the rewinding to catch up will be increased. When this master clock of Fig. 2 is employed as a master clock for the systems of Figs. 6 and 12 it is also essential that a similar motor be used for each of the secondary clocks used in the system. In other words, the ratio of high speed to low speed ratio for the secondary clocks should be the same as high speed to low speed ratio of the rewind apparatus of the master clock for such system.

When the motor 2SM is substituted for the two motors in any one of the secondary clocks the wire that formerly lead to thelow speed motor will be connected to th lead-in wire low and the wire that was formerly connected to the high speed motor will be connected to the leadin wire marked high. This motor 2SM will obviously not be used inthe secondary clocks of Figs. 1 and 2.

If this motor is used in the systems of Fig. 3, 4, 6 or 12 instead of the two synchronous motors the corrections of a tardy secondary clock will be made slower in proportion to the ratio of speeds high to low. Since the motor 28M" has a high-to-low speed ratio of 2 and the synchronous motors SM and SM has a high-tolow speed ratio' of 3 it will take approximately fifty percent more time to correct a tardy clock if the motor 2SM is substituted, and Formulae 2 and 3 above will have to be correspondingly changed. Also, if desired, the poles 296 and 298 of Figs. 8 and 9 may be secured to iron plate 212 in which event plates 213 and 211 may be omitted.

It should be understood that when the two speed synchronous motor 2SM is substituted for the two synchronous motors SM and SM" of Fig. 6 that the secondary clock S will run double normal speed when both of the line wires 248 and 249 are energized. This by reason of the fact that the currents flowing in coils 348 and 349 will be neutralized'and that the current flowing in the coil 241 will be materially increased by reason of reduced resistance due to coils 348 and 349 being in multiple, so that a two-pole magnetic field will be produced in which the poles are almost displaced degrees causing the rotor to operate at two pole synchronous speed. If on the other hand, this two speed synchronous motor 2SM is used in the system of Fig. 12 there is a possibility that during a secondary clock correction after a power failure the contact arm 2 will lodge in the notch 25! and thereby hold the secondary clock at stop. In order to prevent this, contacts 352-453 controlled by the rewind shaft 242 and closed between the 59 /2 and the 2 minute positions of this shaft connected in series with a back contact 353 of relay R may be employed to apply currentto the wire 248 as a result of which current is applied to the four-pole circuit of this motor ZSM" durin the first minute of an hour as manifested by the secondary clock and resulting in the operation of this motor at normal speed and movement of the contact arm 24I out of the notch 25l, all as shown in Fig. 12 of the drawings. Thereafter the secondary clock will again operate at double speed until the relay R picks up.

Referring to the drawings it should be understood that the various inventions and the various forms illustrating the same general invention have been shown specifically in some instances for the purpose of explaining their principles of operation and not with any attempt of limiting them to this particular construction. Referring to Figs. 1 and 2, for instance, the two embodiments of master clocks illustrated therein, although they have been illustrated as master clocks and are particularly applicable to perform a master-clock function it should be understood that they may be used as a mantle clock of the sustained power type. In Fig. l the condenser N is used to dampen out the direct current ripples produced by the rectifier R1 so that the direct current flom'ng in the coil I55 is substantially continuous. In each form of the invention illustrating a clock system two secondary clocks have been illustrated. One of these secondary clocks shows its outside appearance whereas the other shows conventionally its internal construction. The double motors shown in Figs- 8 and 11 and the two speed motor of Fig. 13 may be used in any one of the secondary clocks S, S or S or may be used in place of the rewind motors SM and SM" of Fig. 2. Having thus shown and described a number of embodiments of the present invention it is desired to be under stood that the invention is not limited to these particular constructions except as demanded by the scope of the following claims.

What I claim as new is: 1. In an electric clock system, the combinatio with a source of alternating current of regulated frequency regulated to correctly manifest thepassing of time, a master clockincluding in combination a mechanical time measuring means and a synchronous motor for accurately manifesting the passing of time so long as no current cessation occurs and for substantially accurately'manifesting the passing of time during a current'cessation, a secondary clock including a low speed synchronous motor and a high speed synchronous motor, said low speed synchronous motor "when energized from said source operating said secondary clock to correctly manifest the passing of time clock for connecting said synchronous motors to said line circuits in succession in the same order in accordance with the lapse of time as manifested by said secondary clock and in amanner so that both synchronous motors are not simultaneouslyconnected in th same line circuit and so that the low speed motor is connected into that line circuit into which the high speed motor was last connected, whereby if the contacts controlled by said master clock are operated to shift th source of alternating current from one circuit to another before the contacts of the secondary clock have operated said .high speed synchronous motor is energized.

2. In an electric clock system, the combination with a source of alternating current having its frequency regulated to correctly manifest the passing of time, a master clock of the sustained power type having a time shaft that operates in perfect sub-synchronism with the alternating current from said source so long as no current cessation occurs and which operates at substantially the same speed during a current cessation, a secondary clock having a low speed synchronous motor and a high speed synchronous motor, said low speed motorwhen energized from said source operating said secondary clock to correctly manifest the passing of time and said high speed motor when energized operating said secondary clock at a higher speed, two line circuits connecting said master clock and said secondary clock, contacts controlled by said master clock for energizing said circuits alternately at time intervals as measured by said master clock, means includin contacts operated by said secondary clock for alternately connecting said low speed motor to one and then the other of said circuits at corresponding time intervals as measured by said secondary clock and forv at times connecting said high speed motor to thatline circuit to which said low speed motor is not connected, whereby if said secondary clock is tardy it is at times operated at increased speed by said high speed motor.

'3. In an electric'clock system, the combination with a source of alternating current having its frequency regulated to correctly manifest the passing of time, a master clock of the sustained power type having a time shaft that operates in perfect sub-synchronism with the alternating current from said source so long as no current cessation occurs and which operates at substantially the same sped during a current cessation, aesecondary clock having a low speed synchronous motor and a. high speed synchronous motor, said low speed motor when energized from said source operating said secondary clock to correctly manifest the passing of time and said high speed motor when energized operating said secondary clock at a higher speed, two, line circuits connecting said master clock and said secondary clock, contacts controlled by said master clock for energizing said circuits alternately at time intervals as measured by said master clock, means including contacts operated by said secondary clock" for alternately connecting said low speed motor to one and then the other of said circuits at corresponding time intervals as measured by said secondary clock and for connecting said high speed motor to the opposite circuit during the latter part of each of said time intervals and for isolating said high speed motor from both of said circuits during the early part of at least alternate ones of said time intervals, whereby if said secondary clock is tardy it will be advanced and whereby if said secondary clock is fast it will be temporarily held stationary until correct.

4. In an alternating current clock system; the combination with an alternating current power system delivering alternating current at a frequency regulated to correctly manifest the passing of time; a master clock manifesting standard time; a secondary clock having a drive shaft, synchronous motor means for driving said shaft at a high synchronous speed or at a low synchronous speed; two circuits connecting said master clock and said secondary clock; contacts controlled by said master clock for alternately, for equal time periods as manifested by said master clock, supplying said circuitswith alternating current; means including contacts controlled by said secondary clock for during a first portion of such time period as manifested by said secondary clock connecting said synchronous motor means so as to operate at a low synchronous speed and to a' particular one of said circuits, for during the second portion of such timeinterval connecting said synchronous motor means so as to,

operate at a high synchronous speed and to such particular circuit and for disconnecting said synchronous motor means from such particular circuit during a third portion of such time period, whereby if said secondary clock is ardy it will be accelerated and whereby ifflsyti secondary clock is fast it will be temporar heldat rest.

5. In an electric clock system, the combination with a sourcepf alternatingcurrent, a central location and asecondary clock location, two circuit channels. connecting vsaid central location and said secondary clock location, a master clock at said central location for alternately energizing said circuit channels from said source for equal time intervals; as determined by said master clock and for energizing both of said circuit channels after each current cessation for a time period proportional to such current cessation, a secondary clock at said secondary clock location in-' cluding a low speed synchronous motor and a high speed motor for driving the same, and con-

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