US2631423A - Electric clock - Google Patents

Description

March 17, 1953 R. H. SULLIVAN ET AL 2,631,423

ELECTRIC CLOCK Filed July 11, 1945 5 Sheets-Sheet l Snnentors (Ittorncgs March 1953 R. H. SULLIVAN ET AL 2,631,423

ELECTRIC CLOCK Filed July 11, 1945 5 Sheets-Sheet 2 a? /i A 20 a w :2 n W5 52 A58 0 //0 a W fil Am u j r v i w Illllllll 7 VIII/111M Summons March 17, 1953 R. H. SULLIVAN ET 1.

ELECTRIC CLOCK 3 Sheets-Sheet 5 Filed July 11, 1945 Snnentors (a'zz%zf&

Patented Mar. 17, 1953 UNITED STATES ,F-l CE ELECTRIC CLOCK Delaware .Application luly 11, 1945, .SerialNo. 604,386

The present invention relates generally to electric clocks and ,more particularly to certain improvements in a clock of the electromagnetic impulse type adapted especially for use in automobiles.

The principal object of the invention is to provideja clock of this type of relatively simple constructional design, small overall dimensions and low manufacturing cost which will give'longand reliable service under .such variable voltage, temperature and vibration conditions as are encountered in automobile use.

One feature of the present construction involves the use of a single electromagnet with poles associated with a timing mechanism including a balance wheel armature which controls and is sustained in oscillation by intermittent energization of the electromagnet, and with furtherpoles associated with a separate driving mechanism including anarmature to drive the clock gear train.

A further feature comprises the provision of means to compensate for variations in'vol-tage and regulate the strength of the magnetic field in the balance wheel circuit and a means to prevent destructive sparking at the contact points of the timing mechanism.

Many other features of'the present invention including provisions for star-ting and the construction and relative-arrangement of-the several parts of the clockwill be-apparent from or -specifically noted in the description of the embodiment shown in the accompanying-drawings.

In the drawings:

Fig. 1 is a perspective view. of the clockmechanism.

Fig-2 is aibottom plan view of the clock with the back cover and other part-s removed or broken away.

Fig.3 is a transverse sectionwithparts inelevation.

Fig.4 is an enlarged fragmentary section of the driving mechanism taken substantially -on line'44 of Fig. 2.

Fig. 5 is-a fragmentary elevation of part of the driving mechanism of Fig. 4.

Fig. 6 is a fragmentary'front view takensubstantially on line 66 of Fig. 3.

Fig. 7 is a fragmentary section taken substantially on line 1-! of Fig. 6.

Fig. 8 is a diagrammatic view showing the electrical starting and running circuits.

"Referringfirst to Figs. 1 to 3, a'base plate It is provided with spaced pillars l2 andxl' i on which a bridge It is secured by .screws l-8. vA threepole armature?!) which alsofunctions as the balance wheel is mounted on a staff 22 journaled in jeweled bearings 25 in the bridge is andanoffset portion of base plate [0. A hairspring 26 is secured at its inner end to collet 28 on the staff 22 and is securedat its outer end to a post 30 on the base plate with the outer turn of the hairspring passing through a slot in a regulator arm 32. This arm is connected as shown in Fig. 3 to an operating indicator pointer314 by a pivot post 36 extending through and rotatable in a bearing plate "38 on .base plate .H! below the staff 22 to provide for the adjustment of the arm 32 to shorten orlengthen the effective length of the hairspring to regulate the period of oscillation of the balance wheel in the'usual manner.

An electrical contactto which mayyconsistof a small pin or rodextendingparallel to the staff 2 2 is secured to thearmatureZO at a pointradial'ly spaced from the staff and this contact is grounded to-the baseplatei Othrough thearmature, stafi and hairspring. Abracket 42 which is secured to the base plate and electrically insulated therefrom by an insulating bushing '44 serves as a support for a helicalspring 46 which is formed with a straight portion 48 extending towards the staff 22. .An electrical contact blade .50 issecuredto the end of the spring portionAlS and 'is'so located as to project into the 'arcuate path of movement of the contact 40 on oscillation of the armature :26. The coils of the helical spring 46 are tightly wound together to eiiecta rapid damping of the vibrationsof the contact bladeifi when the blade is released after the, cleflection thereof by the-contact 40 as it engages and ,moves past theblade during oscillation of the armaturejt. w

During normal operation the contact 4,9 alternately engagesthe opposite faces offthe, contact blade 56 itoprovide for, the intermittent energization of the winding, of ,an, electromagnet, indicated generally at 52, which is adapted to impart1 periodic impulses to the armature fijli to maintain theoscillation thereof. The-electromagnet includes a core Mhav-ing one end securedtothe base plate It and upper and. lower pole pieces 56 and 58, respectively, .which-are-so formeduasto locate the pole tips in-thelplaneof t'he armature as at points relatively close tdthe periphery thereof. u

The. b anc -W ee armatu as mb a h electromagnet with its polepieces 55 ;and.58 and the contact arrangement above described constitute a timing mechanism in which .the balance wheel armature operates flwith out restraint .other than that imposed by the ha-irspring, the pivot friction, and the mechanical load imposed by the operation of the contacts. Since this mechanical load and the pivot friction is quite low and not subject to any appreciable variations, it will be seen that the balance wheel armature oscillates at a frequency determined principally by its mass and the torque of the hairspring.

Referring now to the driving mechanism for the clock gear train, the electromagnet 52 is provided with additional upper and lower pole pieces 60 and 62, respectively, which extend parallel to one another and terminate in vertically spaced ends adapted to impart periodic impulses to an armature 64 which is pivotally mounted for limited oscillation between the ends of the pole pieces. The armature 64 which is generally of channel form with the flanges thereof adjacent the pole pieces is secured to a sleeve 66 journaled on a stationary shaft 68 supported by brackets '16 and I2 on the base plate Ill.

A spiral spring I4 having its inner end secured to the sleeve 66 and its outer end secured to the bracket I is adapted to urge the armature 64 out from between the pole pieces 66 and 62 and the extent of movement of the armature is limited by the provision of an arcuate slot E6 in the armature and a closely wound helical spring 18 having one end secured to the bracket 76 with the other end located within the slot 76. This spring I8 also acts as a buffer to cushion the motion of the armature at both ends of its movement as it is oscillated about the pivot shaft 68 being moved in one direction by the spring 24 and in the other direction by magnetic action when the electromagnet is energized by the timing mechanism.

A driving pawl in the form of a hairpin spring or spring wire of U-shape indicated generally at 86 is secured to the sleeve 66. As shown in Fig. 4, this spring is formed with substantially parallel arms of unequal length connected by several turns or coils to provide the desired spring action. The spring 8!] is arranged with these arms extending substantially parallel to the axis of the shaft 68 with the shorter arm 82 tightly secured to the sleeve 66 between similarly formed sheet metal plates 84 and 86 which are clamped around the sleeve and welded or riveted together. The abutting fiat portions of the plates 84 and 66 at one side of the sleeve 66 are provided with similarly formed spaced extensions 88 and 96, respectively, which are ofiset outwardly from the planes of the flat portions to form longitudinally aligned grooves between these extensions to receive the longer arm 92 of the spring 86.

The free end of the arm 92 projects beyond the extensions 88 and 90 to engage a ratchet wheel 94 and arm 92 acts as a spring pawl to advance the ratchet Wheel one tooth each time the electromagnet is energized and the armature 64 moved in one direction. The end of arm 92 is held by the spring action of the coils of the hairpin spring in engagement with the ratchet wheel and the grooves between plates 84 and 86 which receive arm 92 function as guides for the radial movement of the arm with reference to the axis of the shaft 68 as the end of the arm is radially displaced by the teeth of the ratchet Wheel.

The ratchet wheel 64 is secured to a driving worm 96 journaled on the stationary shaft 63 and the driving worm carries an index or star wheel 98. A detent spring I60 which is secured at one end to the bridge I6 as by screws I62 has its free end of substantially V-shaped to engage 4 the teeth of the star wheel to prevent reverse rotation or any movement of the ratchet Wheel and driving worm at times other than when these parts are being moved in one direction by the spring pawl.

The driving worm 96 engages a gear I64 secured on a shaft I66 mounted in brackets I68 and ill! on the base plate I0, and a worm II2 on shaft I66 meshes with a gear II4 which is rotatable on a central shaft H6 and forced by a spring H8 into frictional driving engagement with a collar I20 fixed to the shaft. The shaft H6 is journaled at one end in the bridge I6 and extends through the base plate I6 and a dial plate I 22 with the usual minute hand I24 mounted on the end of this shaft and the hour hand I26 driven thereby through a reduction gear train consisting of the gears I26, I30, I32 and I34.

A setting mechanism for manually setting the position of the hands includes a setting stem I36 which is journaled for rotation and limited endwise movement in a mounting plate or other support I38 and a bracket I46 secured to the plate I36 with the stem extending through the dial plate I22 and provided with a knurled knob I42. A gear I44 and a metal disk I46 of slightly larger diameter than the gear are secured on the stem I36 which is normally held against endwise movement with the disk I46 in engagement with plate I28 by means of a spring I48. An idler gear I50 is mounted on the plate I38 in mesh with the gear I36 of the reduction gear train and this gear I66 is adapted to be engaged by the gear I44 on th setting stem when the stem is moved endwise to then provide for the adjustment of the hands by rotation of the stem in the usual manner.

As shown in Figs. 6 and '7, a spring contact arm I52 is secured to and insulated from the base plate i6 and formed with a flanged end which extends over the edge of the disk I46 on the setting stem I36 and is normally spaced therefrom but will be engaged thereby when the stem I36 is moved endwise during the setting operation to complete a starting circuit to be hereinafter described.

The base plate Il) may be secured by screws I54 to the mounting plate or other support I38 and a sheet metal cover I56 secured as by screws on posts I58 and I66 on the base plate It to conceal and protect the timing and driving mechanisms.

Referring now to the diagrammatic showing in Fig. 8, the electromagnet is provided with two windings as indicated at I62 and I64. Although shown as separated these windings are wound in bifilar relationship, or in other words, the two wires constituting these windings are parallel and wound simultaneously on the core 54 with the same number of turns. The source of current, indicated as a battery I66, is connected directly to one end of each of the windings I62 and I64 by conductor I68.

The winding I62 which may be termed the running winding is connected at its other end by conductor I!!! to the contact blade 56 through the spring 46 and the running circuit will therefore be completed whenever the contact 46 on balance wheel armature 26 is in engagement with the contact blade 50 through the balance staff 22 and hairspring 26 to ground.

The ends of the winding I6 are connected together, thus shcrt-circuiting this winding on itself to function as a magnetic damping means, and the winding I64 is tapped at an intermediate point which is electrically off center with this tap connected by conductor I72 to the contact arm I52 to thereby function as a starting windparts have been diagrammatically shown when the circuits are open and the balance whcel armature 29 is in the position of rest or equilibrium to which it is urged by the hairspring 26. In this position it will be seen that the contact 46 is slightly spaced from the contact blade 56 and the contact arm I52 is also spaced from the disk I46. When the setting stem I36 is moved endwise during the setting operation the disk I45 will engage arm I52 to complete a starting circuit which will be effective, since the connection of conductor I12 to the winding I64 is electrically ofi center, to create a magnetic field through the pole pieces 55 and 58 to attract the balance armature and rotate the armature in a clockwise direction, until the arms of the armature which were closest to the pole pieces are drawn to substantially the position shown in Fig. 2.

The armature will then be magnetically held in this position during rotation of the setting stem'to set the hands but as soon as the stem is released and returned endwise by the spring 548, the starting circuit will be broken at contact arm I52 and the armature will then be rotated in a counter-clockwise direction with sufficient inertia to engage contact 4! thereon with the contact blade 53 and move on past this blade.

It will be understood that whenever contact 49 engages the contact blade 53 a circuit will be completed through the running winding I62 and the balance wheel armature will be sustained in oscillation, after starting, by magnetic impulses imparted thereto upon energization of this winding during movement of the armature in both directions. Whenever the winding IE2 is energized, a current will also be set up or induced in the short-circuited winding I54 which Will thereby function as a magnetic damping means to practically eliminate all sparking at the contact and contact blade 56.

In an electric clock of the magnetic impulse type for use in automobiles it is desirable to provide some means to compensate for the wide variations in battery voltage such as affect the rate of the clock by changing the magnetic field strength which varies the amplitude of the balance. The effect of varying voltages would be even more pronounced in the present clock wherein, as distinguished from prior clocks of this type, there is no mechanical connection between the timing mechanism and the driving mechanism so that there is no restraint such as caused by the drive and gear train friction on the amplitude of the balance wheel armature.

The provision in the present clock of separate pole pieces for the independent armatures of the timing mechanism and the driving mechanism is employed in the manner to be now described to maintain the magnetic flux utilized to operate th balance wheel armature at a practically constant value throughout the range of voltage variations that are encountered in automobile operation.

With reference first to the magnetic circuit of the timing mechanism, the electromagnet core 54, the pole pieces 56 and 58, and the balance wheel armature 253 are made from a material such as a nickel iron alloy containing over 40% nickel, and preferably a nickel iron alloy, which will become magnetically saturated at very low magnetic densities or under a very low magnetizing force.

The amount of flux, except for leakage, which is capable of passing through this magnetic circuit is determined and limited in the present arrangement by the minimum cross-sectional area of the pole pieces 56 and53 which are formed with their smallest cross section at the pole tips, and the magnetic circuit is so designed that the application of a relatively low voltage to the running winding 562 of the electromagnet will produce a magnetizing force sufficient to substantially saturate the pole pieces 56 and 58. The cross section of the narrowest portion of the armature 2 0 is larger than that of the pole pieces or pole tips so that the armature itself will not be substantially saturated but the flux which operates the armature will be kept practically constant at varying voltages by reason of the saturation of the pole pieces.

At hi her voltages than the minimum necessary to saturate the pole pieces or the reduced tips thereof, there would ordinarily be magnetic leakage through the air gaps in the magnetic circuit and some of this leakage flux would tend to increase the total flux acting on the unsaturated armature and increase its amplitude.

To absorb this leakage flux in addition to any flux in excess of that necessary to saturate the pole pieces and 58, the magnetic circuit through the pole pieces 50 and 62 for the driving armature 65 has been designed to function as a shunt path. For this purpose, the pole pieces 60 and 32 are made from a material such as Armco iron or Swedish iron or other known magnetic materials which do not become magnetically saturated or substantially so at the maximum volage or magnetic strength encountered in the present application.

Although the principal features of the present clock construction will be apparent from the foregoing description it is desired to call attention to certain distinguishing features thereof which have been combined to produce an automobile clock of exceptional performance from the standpoint of both accuracy and reliability.

By separating the clock mechanism into mechanically independent timing and driving mechanisms, the gear train friction and any variations therein will have no effect on the balance wheel timing which controls the periodic energization of the electromagnet. The balance wheel timing will also not be affected by variations in voltage since the pole pieces for the balance wheel armature will be substantially saturated at the minimum voltage and the pole pieces for the separate driving armature constitute an unsaturated shunt circuit to absorb the excess flux generated at higher voltages.

Destructive sparking at the contact points is eiiectively prevented by the provision of the short-circuited damping winding on the electromagnet and this winding is further employed in a starting circuit which includes a starting switch operated by the setting stem for manually setting the position of the hands.

Many other features including the details of construction and the mounting of the several parts as disclosed herein are considered to also constitute distinct improvements over prior practice. It will be understood that many modifications and the separate use of certain features are contemplated as coming within the scope of the present invention as defined in the claims appended hereto.

We claim:

1. In an electric clock, a base plate, an electromagnet having a core secured at one end to said base plate and extending at right angles thereto, pole pieces secured to the ends of said electromagnet and diverging from the axis of said core with end portions of said pole pieces bent in opposite directions to position the pole tips in a plane which is parallel to said base plate, and a balance Wheel armature mounted on said base plate for oscillation between said pole tips on an axis at right angles to said base plate.

2. The elements set forth in claim 1 in which, further pole pieces are secured to the ends of said electromagnet with said further pole pieces extending substantially parallel to said base plate, and a driving armature is mounted on said base plate for oscillation between the spaced ends of said further pole pieces on an axis substantially parallel to said base plate.

3. In an electric clock, an electromagnet, a timing mechanism including a balance wheel armature adapted to control the periodic energization of said electromagnet and be sustained in oscillation thereby, a pair of pole pieces for said balance wheel armature, said pole pieces being of such material and cross-section as to be magnetically saturated at a predetermined minimum voltage, and a driving mechanism including a gear train,

a driving armature for said gear train, and a further pair of pole pieces for said driving armature, said further pole pieces being of such material as not to become saturated at said predetermined minimum voltage and function as a magnetic shunt for the magnetic circuit of said saturated pole pieces.

RAYMOND H. SULLIVAN.

PETER R. CONTANT.

REFERENCES CITED The following references are of record in the file of this patent:

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