US2864231A - Electric timing device - Google Patents

Description

Dec. 16, 1958 sp 2,864,231

ELECTRIC TIMING DEVICE Filed March 17, 1954 2 Sheets-Sheet 1 Inventor: 1:522 Hans Spfln er" by,a?fiw-(.

His Att oYney Dec. 16, 1958 H, SPRINGER 2,864,231

ELECTRIC TIMING DEVICE Filed March 17, 1954 2 Sheets-Sheet 2 Inventor'- Hams Spvm 6 His Attorne United States Patent ELEcrnrc TlMh DEVICE Hans Sp in er, Ashlanrl, l dass, assignor to General Electric Company, a corporation of New York Application March 17, 1954, Serial No. 4l6,774

5 Claims. (Cl. 5@23} This invention relates to electric clocks and timing devices and has particular application to electric clocks of the type to be operated from a low voltage direct current source such as a storage battery or dry cell. Electric clocks of this general type have found considerable application in automobiles, boats, aircraft and other movable craft and vehicles and for such applicaticns are adapted to be operated from a storage battery or similar power source.

In household and similar applications for electric clrcl's where a Controlled frequency source of alternetting current power is avai able, a synchronous motor is often provided to drive the clock mechanism. The speed at which the clock mechanism is driven is, in such a case, controlled by the frequency of the alternating current source, so that no separate speed reg lating means need normally be provided. In automobile applications, however, where normally only a low voltage (i. e., 6 or 12 volts) direct current source is available, some means must be provided for regulating the speed at which the clock mechanism is driven. governor for an electric clock which has no available external synchronizing signal must be self-contained, the operation of such a governor is usually based on some form of resonance involving oscillatory, vibratory or some other form of cyclic motion. Thus the instantaneous speed of a clock mechanism controlled by this type of governor is not constant but rather follows a cyclic pattern along with the governor. Only the average speed of the clock mechanism is limited to a substantially constant value while the instantaneous speed rapidly accelerates and decelerates above and below the average value.

One example of a governor of the above-mentioned type is the well known balance wheel type of escapement quite commonly employed in spring driven clocks and watches. This type of governor limits the average speed of the clock mechanism by repeatedly interrupting the movement of the clock gear train and bringing it to a complete halt usually around 4 or 5 times a second. Although other types of speed limiting governors falling Within this category may or may not completely interrupt the movement of the clock mechanism in accomplishing the speed limiting function, they all have the common characteristic of intermittently decelerating the speed of the clock or timer mechanism and then allowing a period of acceleration.

Governors of this type have been found to perform satisfactorily and can generally be produced at a relatively low cost so that they are widely used in clocks and timing devices requiring self-contained governors. However, the employment of such a. governor poses certain problems arising from the rapid accelerations and decelerations of the clock mechanism. It is apparent that in order to minimize the driving force required to acc rate the clock mechanism at the required rate and to minimize the inertia loads transmitted during apid deceleration period, the inertia of the rotating Since a I .periods.

parts must be kept as low as possible within the stress limits required for a satisfactory operating life.

This consideration also applies to the driving mechanism of the clock. For this reason, among others, direct current torque motors have not heretofore been generally employed to drive clocks controlled by the abovementioned intermittent deceleration type of speed limiting governor, since the addition of the relatively large inertia of the motor would not only require that a much greater torque be developed in order to achieve the proper rate of acceleration but would also cause severe inertia loads to be transmitted to the delicate components of the mechanism during the rapid deceleration Such severe operating conditions would cause a considerable reduction in the operating life of the components of the clock mechanism. The problem is even more aggravated where the balance wheel type of escapement is employed as a governor since, in such a case, the movement of the clock mechanism is periodically fully interrupted so that the inertia loads are even more severe.

On the other hand, the reliability, accuracy and low cost generally obtainable with self-contained governors operating on a resonance principle have led others to retain this form of speed limiting means and to devise other forms of driving mechanisms. For instance, it has been a common practice in clocks of this type to employ a low inertia spring motor as a drive means with the spring being recharged at intervals by means of a solenoid which is automatically energized when the spring discharges beyond a certain point. In this and other forms of driving means heretofore commonly employed to drive clocks having governors of this type, the drive is of the intermittently operable type. That is, the ultimate source of mechanical drive power is alternately energized and de-energized through some form of automatically actuable switching arrangement, the application of a continuous torque from such a source being heretofore considered undesirable by reason of the problems arising out of the relatively .high inertia of the electrical components required to develop such a torque. The intermittently operable typev of drive is, on the other hand, subject to various problems such as that of switch contact deterioration by reason of the repeated switch actuations, a problem which is quite serious with relation to obtaining a satisfactory operating life.

In addition to the above considerations, it can be appreciated that clocks and timing devices for automobiles and similar vehicles must operate under a wide variety of conditions and are exposed to sand and dust atmospheres and similar conditions. Consequently, where a direct current motor driven clock or timing device is used, it is desirable to provide means for preventing sand and dust and other foreign particles from clogging the commutator and permanently interrupting contact between the brushes and commutator. In this same connection, it should be apparent that the motor must operate continuously over the entire life span of the clock and that consequently there is a danger that such extended operation may under certain conditions result in corrosion or pitting of the commutator or brush contact surfaces. Therefore it is also desirable that means he provided for automatically wiping the commutator and brush contact surfaces in the event that the electrical power is interrupted.

.A further consideration, which will be discussed herein, arises from'the well known tendency of the balance Wheel escapement type of governor to lock at rest in certain positions under starting conditions when the full operating torque is suddenly applied and maintained.

Accordingly, it is an object of this invention to pro vide an improved timing device driven by a' direct current torque motor and controlled by an intermittent deceleration governor of the above-mentioned type, which is not subject to the, disadvantages set forth above.

it is another object of this invertion to provide an im proved direct current electric clock controlled by a balance wheel type of escapernent mechanism and driven by a direct current torque motor, in which means are provided for coupl'ng the drive motor in driving relationship to the clock mechanism so as to avoid the occurrence of the above-mentioned inertia loads upon the intermittent interruptions of the clock mechanism motion by the escapement.

it is a further object of this invention to provide an proved electric clock driven by a direct current torque motor in which means are provided for rapidly rotatingthe motor in the reverse direction upon an interruption of electrical power so that the brush and commutator contact surfaces are rapidly wiped in the reverse direc tion to remove foreignparticles and clean the contact surfaces.

it is still a further object of this invention to provide means for removably mounting the motor in driving relationship to the clock mechanism so that the motor can be readily detached for servicing or replacement purposes.

It is still another object of this invention to provide an improved electric clock driven by a direct current motor and controlled by a balance wheel escapement, in which means are provided to prevent locking of the escapement mechanism at starting.

Briefly stated, in accordance with one aspect of this invention, a continuously operable motor means, including a small direct current, commutator type torque mete ispr-ov'ded to drive the clock mechanism. The motor means is coupled in driving relationship to the clock gear train through a resilient coupling means such as a coil spring and the speed of the clock mechanism is regulated by an intermittent deceleration type of governor which, in the embodiment illustrated, is a conventional balance wheel escapement. The resilient coupling serves to insulate the drive motor from the rapid accelerations and decelerations of the clock gear train and serves to minimize shock and inertia loads which occur during the deceleration and interruption of the gear train motion. The motor and spring driving arrangement is freely movable in the reverse direction so that the spring is allowed to discharge and rapidly rotate the motor in the reverse direct cn in the event of an electrical power interruption so that the brush and commutator contact surfaces are rapidly wiped in the reverse direction to remove foreign particles and clean the contact surfaces.

This invention will be better understood and other objects and advantages will be apparent from the following description taken in connection with the accompanying draw'ngs, and its scope will be pointed out in the appended claims.

Referring to the drawinggFig. 1 is a perspective view of a low voltage, direct current clock embodying this invention; Fig. 2 is a cross sectional view of the clock shown in Pig. 1 illustrating the arrangement of the clock mechan sm and drive motor components; Fig. 3 is an exploded view illustrating in perspective the arrangmrnt of the clock mechanism compcnents and the motcrdrive pinion together with the resilient coupling means; while Fig. 4 illustrates in perspective the motor rotor and the drive pinion.

The clock shown in Fig. 1 ha particular application to automobiles and comprises an outer casing 1 provided with mounting tabs 2 for mounting the clock on the instrument panel. A sweep second hand isprovided in addition to the usual indicating hands and a knob 3 is provided to allow manual adjustment of the minute and hour hands. The regulating mechanism, which controls the speed of the clock, is adjustable through the agency of a shaft 4, which is provided with a suitable slot so that it can be rotated by means of a screwdriver or similar tool. The position of the speed regulating mechanism can be observed through a slot 5 provided in the face of the clock.

The clock mechanism, shown in cross section in Fig. 2 and in the perspective in the exploded view of Fig. 3, is driven by a suitable direct current, commutator type torque motor through a resilient coupling means-such as a spring 6. The illustrated drive motor, shown in cross section at 7 in Fig. 2, is of the type which is shown and claimed in application of Edgar A. Phaneuf, John R. Enochs and myself, Serial No. 416,746, filed March 17, 1954, entitled Electric Motor and Method of Manufacture Therefor, now Patent Number 2,818,518, and assigned to the assignee of the present invention. It will be understood that Fig. 2 illustrates this type of motor as part of a preferred embod'ment of this invention and that other types of low voltage, direct current torque motors may be employed without departing from the scope of this invention.

Referring to Figs. 2 and 4, the drive motor shown comprises an outer casing 8 which positions and supports an annular field magnet 9. The rotor coils ill! are Y connected and symmetrically mounted as shown in Fig. 4 and are supported on a shaft ll; which is rotatably mounted at one end in a bearing portion 12 provided in the housing 8 and at the other end in a bearing portion formed in a tab 13 which extend from a motor mounting plate 14 as shown in Fig. 3. The motor is prov'ded with a commutator llla made up of three segments which are connected respectively to the outer ends of the rotor coils 1d. The commutator is engaged by a pair of wire brushes 1111 which are connectible to a direct current power source through a pair of terminals &9.

As shown in Figs. 2, 3 and 4, a pinion 15 is mounted to rotate with the motor shaft ill and engages a gear 16 mounted on a bushing member 17 which is in turn rotatably mounted on second hand shaft 18. The drive motor means is coupled in driving relationship to the clock mechanism through a resilient coupling means such as the spr'ng member 6 which resiliently connects the gear 16 with a gear 19 aflixed to the shaft 18. Since the gear 16 is rotatable with respect to the shaft 18, the motor output torque is transmitted through the spring 6 to the gear 19 which directly drives the second hand shaft 1%. V

The speed of the clock mechanism is regulated by a suitable governor of the intermittent deceleratirn type such as a balance wheel escapement mechanism shown at 24) in Fig. 3. The escapement 20 comprises the usual elements including an escape wheel 21, a pivotally mounted rocker arm 51, an oscillatory balance wheel 52, and a hairspring 26. This type of escapement operates in a well known manner with the rocker arm pivoting back and forth and interacting w'th the escape wheel 21 t0 alternately interrupt the motion of the gear train and then allow a brief period of acceleration. The average speed of the clock gear tra'n is thus limited to a substantially constant value by means of intermittent accelerations and decelerations. The escape Wheel 25. is driven by gear It) which engages a pinion 22 attached to the escape wheel shaft.

The escapement is provided with rdjusting means which can be manually actuated from the face of the clock by rotating the shaft 4. A pinion 23 is attached to the end of the shaft 4 and engages a rctat bly mounted gear segment 24. An adjusting member 25, shown in two secticns in Fig. 3 for convenience of illustration only, extends from the gear segment 24 and engages a hairspring 26 adjacent a fixed support 27. The member 25 moves with the gear segment 24 to change the effective length of the hairspring and thus control the speed of the escapement. An indicating member 28, shown in Fig. 2, is attached to the gear segment and has a portion thereon visible through the slot 5 to indicate the setting of the regulating mechanism.

As pointed out above, the second hand is driven through the spring 6 and the gear 19 attached to the shaft 18. A pinion 29 is affixed to the shaft 18 and drives a gear 30 which is attached to shaft 31 by means of a bushing 32. A pinion 33 rotates with the shaft 31 and drives gear 34 which is mounted on minute hand sleeve 35 but is free to rotate relative thereto. The minute hand sleeve 35 extends concentrically with the second hand shaft 13 and is rotatably mounted on a bushing 50 which is afiixed to a mounting plate 36 and extends through a second mounting plate 37. The second hand shaft 13 is supported independently of the minute hand sleeve 35 in the elongated bushing 50. The minute hand sleeve 35 extends through the gear 34 and engages a spring member 38 which is compressed into engagement with the face of the gear 34 upon assembly of a bushing 53 to the minute hand sleeve. The spring 38 provides a frictional drive between the gear 34 and the minute hand sleeve 35 in order to allow adjustment of the indicating hands as hereinafter described. Since the torque required to drive the indicating hands is relatively quite small, the gear 34 drives the minute hand shaft through the spring member 33 without the occurrence of any slipping action.

A pinion 39 is attached to the portion of the sleeve 35 extending through the plate 37. The speed is reduced to drive the hour hand sleeve 40 by gears 41, 42 and 43.

The knob 3, shown in Fig. l, is attached to a set shaft 44 which can be pulled forward against a spring 45 to bring gear 46 into engagement with the gear 41 thereby allowing both the hour and minute hand shafts to be manually rotated to the desired setting. Since the torque required to rotate the gear 34 in the reverse direction is relatively very high, the sleeve 35 will slip relative to the gear 34 through the agency of the spring member 38 thereby allowing the indicating hands to be set independently of the clock and motor drive mechanism.

The mounting plate 37 is attached in spaced relationship to the motor mounting plate 14 by means of the spacer members 47 which are afiixed to the mounting plate 14 and which are provided with suitable means such as the threaded portions shown so that they can be secured to the mounting plate 37. The mounting plate 36 is attached in spaced relationship to the motor mounting plate 14- by means of similar spacer members indicated at 48 in Fig. 3 but not shown in Fig. 2.

The spacer members 47 are provided with internally threaded portions which extend into the motor mounting plate 14. The motor is in turn provided with suitable mounting lugs which can be aligned with the internally threaded portions of the spacers 4-7 so that the motor can be attached to the motor mounting plate by means of screws 54 extending through the mounting lugs of the motor and into the internally threaded portions in the ends of the spacers 47. Thus the motor is freely removable as a unit so that it can be replaced or repaired without disturbing the rest of the assembly.

The details of the various components having been set forth above, the overall operation of the clock embodying this invention will now be described.

The clock motor means, comprising the direct current electric motor and the torque transmitting members extending from the motor up to the resilient coupling means 6, drives the intermittently movable gear train through the resilient coupling 6. The rapid accelerations and decelerations of the gear train are followed by the spring 6 but not by the motor drive means by reason of the relatively high inertia of the motor rotor. The spring 5.? unwinds slightly during the acceleration period, since the motor is rotating at a continuously lower speed mately its initial position by the continued rotation of the motor during the period in which the motion of the gear train is interrupted by the escapement.

The motor can therefore rotate continuously while driving the intermittently movable gear train. It is thus unnecessary to provide additional torque to accelerate the much heavier motor rotor along with the intermittent movements of the escapement controlled gear train, since the spring 6 will discharge slightly a small amount to provide this rapid movement. In addition, the inertia of the spring 6 is quite low and hence the spring can stop suddenly along with the gear train without transmitting any substantial additional shock loading beyond the relatively low torque exerted. This invention therefore not only eliminates the necessity for accelerating the motor means along with the gear train but also prevents the occurrence of the shock loads which would otherwise occur if the movement of the motor were also interrupted by the escapement mechanism.

The drive motor is unrestrained from reverse rotation so that if it should lose its driving force, the small amount of energy stored in the spring 6 would cause relatively rapid reverse rotation of the motor through at least a portion of a revolution. Thus if the electrical circuit were interrupted by reason of foreign particles sticking to the commutator or by corrosion or pitting on the commutator or brush contact surfaces, the motor would automatically be rapidly rotated in the reverse direction to allow the brush to again contact the commutator to cause the motor to again drive forward. Thus the brushes are rapidly wiped back and forth across the commutator so that in most cases any foreign particles will be dislodged and the contact surfaces cleaned by the wiping action. The spring 6 therefore not only provides a resilient coupling which permits the motor to rotate continuously under normal conditions but also provides for an automatic Wiping action between the brushes and the commutator segments in the event of an interruption of electrical power.

The resilient coupling spring also provides an additional advantage when a balance wheel escapement Is employed as the governor. It is well known that when this type of escapement is at standstill, the pallet pins on the rocker arm have a tendency in certain positions to lock with the serrations on the escape wheel when the operating torque is suddenly applied and maintained on the clock mechanism. The provision of the coupling spring 6 overcomes this disadvantage. Under starting conditions the running torque is applied gradually by reason of the presence of the resilient coupling 6 and the inertia of the motor rotor causes it to charge the spring 6 beyond the normal operating point so that the rotor will oscillate back and forth a number of times at starting to agitate the escapement mechanism into motion. Both the gradual application of torque and the agitating motion of the rotor serve to prevent locking of the escapement mechanism at starting.

It will be apparent that the size and other characteristics of the spring 6 will be affected by the particular configuration employed and by the magnitude of the shaft output torque delivered by the drive motor. By way of example, in an electric clock embodying this invention and designed for use in automobiles and similar vehicles, it was found that a drive motor having a shaft output torque in the rangeof .002 to .007 lb.-in. would perform satisfactorily in combination with a coupling spring meeting the following specifications:

Material: Spring steel.

Wire diameter: .010.

Free length of coiled spring: 0.250".

Total length of wire in spring: 5.077.

Effective length of wire in spring: 5.027".

Number of turns: 10.

inside diameter of coil: 0.150".

Angular spring constant: 19 per .001 ib.-in. torque,

The most important of these specifications from a performance standpoint is the angular spring constant, the remaining features being more concerned with cost, physical size and so forth, it has been established that in general springs having angular spring constants in the general vicinity of 4 to 30 per .001 lb.-in. torque may be employed in arrangements wherein the output torque of the drive motor falls within the above-mentioned range of .002 to .007 lb.-in.

It will be apparent, of course, that other forms of resilient couplings may be utilized to provide the angular resilience between the motor and the clock mechanism. And it will be realized that the above ranges of motor torques and spring constants may of course be substantially varied depending on the size and configuration of the other components employed. The above figures, however, serve to set forth a workable relationship between the parameters involved in a particular embodiment of this invention and may be used as a basis for establishing the proper magnitudes of parameters for other sizes and configurations.

Although the particular clock described herein and embodying this invention is controlled by means of a balance wheel type of escapement, it will be'undersood that this invention is also applicable to other types of clocks and timing devices in which the speed is controlled or limited by governors which operate to intermittently decelerate the speed of the clock or timer movement even though such governors may or may not fully interrupt the motion of the parts in accomplishing their function.

it will also be understood that the scope of this invention is not limited in its other aspects to the particular embodiment described, and that various changes, cornbinatio-ns, substitutions or modifications may be employed in accordance with these teachings Without departing in spirit or in scope from this invention in its broader aspects.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. Timing means comprising a gear train, escapement means interacting with said gear train to permit said gear train to be advanced in intermittent steps at a substantially constant average speed, a direct current continuously operable torque motor having a high inertia rotor for driving said gear train, a split commutator fixed to said rotor for rotation therewith, a plurality of brushes engaging said commutator for supplying electrical power to said commutator, and a low inertia spring connecting said rotor to said gear train for causing said rotor to oscillate back and forth a number of times at starting to agitate the escapement into motion.

2. Timing means comprising a gear train, escapemen means interacting with said gear train to permit said gear train to be advanced in intermittent steps at a substantially constant average speed, a direct current torque motor having a high inertia rotor for driving said gear train, a plurality of windings mounted on said rotor, a split commutator fixed to said rotor for rotation therewith, said windings being connected to said commutator, a plurality of brushes engaging said commutator for supplying electrical power to said windings, a low inertia spring connecting said rotor to said gear train for causing said rotor to oscillate back and forth a number of times at starting to agitate the escapernent into motion, said rotor being unrestrained from rotating in a reverse direction under the influence of said spring when the electrical power to the windings of said rotor is interrupted, whereby reverse rotation of the rotor and commutator Y 8 with respect to said brushes facilitates cleaning of said brushes.

3. In an electric clock, the combination of a unitary supporting structure comprising a plurality of mounting plates disposed in spaced-apart parallel relationship to each other, a gear train supported on said unitary supporting structure and including a plurality of shafts rotatably mounted on said mounting plates, said shafts extending substantially perpendicular to said mounting plates, time indicating means connected to be driven by said gear train, escapement control means mounted in said unitary supporting structure to interact with said gear train and limit the average speed thereof to a substantially constant value by periodically interrupting the movement of said gear train, a direct current torque motor having a high inertia rotor for driving said gear train, said motor being removably mounted on one of said-mounting plates, said motor rotor extending substantially perpendicular to said mounting plate, gear means fixed to said rotor extending through said one of said mounting plates, said gear means being in mesh with said gear train, a plurality of windings mounted on said rotor, a split commutator fixed to said rotor for rotation therewith, a plurality of brushes engaging said commutator for supplying electrical power to said commutator, and a low inertia spring having its axis arranged substantially perpendicular to said mounting plates disposed in said gear train for resiliently connecting said escapement to said high inertia motor rotor for causing said rotor to oscillate back and forth a number of times at starting to agitate the escapement into motion.

4. An electric clock operable from a low voltage direct current source comprising time indicating means, a gear train connected in driving relationship to said time indicating means, a mechanical escapement arranged to interrupt periodically movement of said gear train to limit the average speed thereof to a substantially constant level, a direct current torque motor having a high inertia rotor for driving said gear train, a plurality of windings mounted on said rotor, a split commutator fixed to said rotor for rotation therewith, a plurality of brushes engaging said commutator for supplying electrical energy to said commutator from said low voltage direct current source, an output shaft extending from said rotor and having a drive pinion fixed to rotate therewith, a rotatably supported gear member engaging said drive pinion, and a low inertia spring interconnecting said gear member and said gear train for causing said rotor to oscillate back and forth a number of times at starting to agitate the escapement into motion, said coupling spring being light, flexible, readily responsive and having low external friction.

'5. Timing means comprising a gear train, escapement means interacting with said gear train to permit said gear train to be advanced in intermittent steps at substantially constant average speed, a direct current torque motor having a high inertia rotor for driving said gear train, the rotor of said motor being unrestrained from rotation in a reverse direction, and an angularly resilient low-inertia spring connecting said rotor to said gear train for causing said rotor to oscillate back and forth a number of times at starting to agitate the escapement into motion.

Hookham July 23, 1901 Holtz Feb. 14, 1928

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