US2632292A - Impulse electric clock - Google Patents

Description

March 24, 1953 A. AMEND, JR

IMPULSE ELECTRIC CLOCK 3 Sheets-Sheet 1 Filed Feb. 16, 1949 iNSULRTlON J1me Np, \IR.

March 24, 1953 AMEND, JR

IMPULSE ELECTRIC CLOCK 3 Sheets-Sheet 2 Filed Feb. 16, 1949 NYENTO QDOLPH MEND JR. .5 QfiTTORNEZY March 24, 1953 AMEND, JR

IMPULSE ELECTRIC CLOCK 3 Sheets-Sheet 3 Filed Feb. 16, 1949 w w m w Bayard-for Q A D m MI w W. nwb

Patented Mar. 24, 1953 UNITED STATES PATENT QFFICE IMPULSE ELECTRIC CLOCK Adolph Amend, J r., Harrison Park, N. J assignor to General Time Corporation, a corporation of Delaware Application February 16, 1949, Serial No. 76,706

vide an electricclock for battery operation which is inherently of high accuracy in spite of wide variations in battery voltage. It is another object to provide an impulse clock which is extremely durable and capable of maintaining accuracy over long periods of time in spite of the shock and vibration encountered. in automotive use. It is a further object related. to the above to provide an electric clock which is not only compact but of simple and straightforward construction enabling the manufacturing cost to be reduced to a minimum, an important feature in a highly competitive field where profit margins are small. A more detailed object is to provide a clock which is inherently efiicient, the battery drain being sufliciently low as to enable it to run for long periods without battery recharge or replacement, thus making possible accurate time keeping remote from a commercial alternating current supply. Although electrical contacts are 7 used, interference with nearby radio sets is nonexistent.

Other objects and advantages of the invention will be apparent from the following detailed description taken in connection with the accompanying drawings, in which:

Figure 1 is a side view in elevation of a clock constructed in accordance with the present invention.

Fig. 2 is a sectional view taken along line 2-2 of Fig. 1, the clock being viewed from the rear.

Fig. 3 is a horizontal section looking downwardly along the section line 3-3 of Fig. 2.

Fig. 4 is a perspective view of the armature assembly with a portion thereof broken away to show the contact structure in greater detail.

Fig. 5 is a perspective view similar to Fig. 4 showing the other side of the armature assembly.

Fig. 6 is a fragment showing the combined balance wheel, hairspring, and contacts operated thereby.

Figs. 7-11 are stop motion views showing the positions of the armature and contacts as well as the direction of movement of the balance wheel at the various periods in the operating cycle.

Fig. 12 sets forth the wiring diagram in more or less schematic form.

While the invention is susceptible of various modifications and alternative constructions and uses, I have shown in the drawings and will here 4 Claims. (CI. 58-28) I vention.

alternative constructions and uses falling within the spirit and scope of the invention as expressed in the appended claims.

Referring now to the figures, and particularly Figs. 1-3, a clock 29 is shown having a frame which includes mounting plates 2|, 22 and; 23 spaced from one another in parallel relation by posts 24. The clock face 26 is arranged parallel to the plate 23 and the time is indicated thereon by a set of hands 21. As is conventional, the hands are driven by means of a gear train indicated generally at 28. The initial gear 29 of the series is driven by a worm 32 mounted on the plate 22. The present invention is concerned with an improved mechanism for causing the gear train to be accurately driven and in the present instance for causing rotation of the worm 36.

To this end a timing mechanism is employed which comprises an armature assembly indicated generally at 34 (see Figs. 4 and 5) which is actuated periodically by means of an electromagnet 35. Prior to discussing the armature assemblyit will be helpful to inspect the manner in which the electromagnet 35 is constructed and mounted. As shown to best advantage in Fig. 2 it includes a C-shaped pole piece 36 having legs 31, 38. These legs are opposite one another and have faces arcuately formed to receive the armature assembly 34 between them. The' faces include raised projections or teeth 39 which serve to concentrate the magnetism and to pull similarly shaped teeth on a cooperating armature into alinement. Encircling the centerportion of the electromagnet 35 is a coil 4-9 having many turns of fine wire wound thereon. For a purpose which will later appear, a short-circuiting sleeve of copper 46 surrounds the core and is included within the coil it.

Turning attention now to the armature assembly shown in Figs. 4 and 5 it will be noted that it includes a pair of supporting plates 45, 46 having a plate-like magnetic armature 4'! supported between them on posts 48, 4.9. The plates 45, 4B are preferably insulated from one another, for example by insulating washers 5B for the purpose of conducting current to the contacts which are internally contained. The ends of the armature 57 are preferably made convex and include toothed projections 54 for mating with the projections 39 previously referred to.

In order to support the armature assembly 34 within the frame of the clock, the supporting plates 45; 46 are provided with axially extending trunnions or spindles 55, 56. As shown in detail in Fig. 3 such spindles are respectively received in apertures provided in the plates 2!, 22.

In practicing-the invention in one of its aspects means are provided for not only making an electrical connection with the respective supporting plates 45, 46 but for biasing the armature assembly 34 as a whole to a backed-off o1- deenergized position in which it is cocked at a small angle with respect to the pole pieces N, 38 of the electromagnet. In the present instance thi is accomplished by hairsprings El, 58 which are connected at their inner ends to the respective spindles 55, E. The outer ends of the hairsprings are anchored to the frame by terminals 59, ee supported on plates 2|, 22. In order to insulate these terminals from one another the plate is formed of insulating material such as plastic and includes a terminal plate Zia riveted or. otherwise-fastened thereto for both receiving the spindie. 55. and for mounting the terminal 55. With thearmature assembly mounted as shown it will be apparent that it and the associated hairsprings arecompletely shielded. Protection against dam age is insured by the fact that the structure is equivalent to one rigid box rotating through a limited are inside another box. Further, the

I assembly 34 as a whole may be readily balanced about its axis of rotation so that shocks and vibration will affect all parts of the assembly equally and there will be no net rotation effect to interfere with the magnetically-produced rocking movement.

Included within the armature assembly 3% and mounted for rotation with respect thereto is a balance wheel 64 having a shaft 65. The ends of the shaft 65 are respectively received in jeweled or similar low-friction bearings 85, $1, the latter bearing being preferably axially adjustable.

Mounted adjacent the balance wheel Kit is a hairspring 68 having its inner end connected to the shaft 65 of the balance wheel and serving to transmit torque thereto in one direction 'or the other. The outer end of the hairspring 68 carries an enlargement 14 which is flexibly mounted and which is constrained so that it may undergo only a limited amount of movement in either direction. Movement in one direction, clockwise as viewed in Fig. 6 and counterclockwise as viewed in Fig. 4, is prevented by means of a stop l5 affixed to the armature plate ll. the opposite direction is strictly limited by means of, astop consisting of a contact it which passes through an aperture l! in the armature plate and which issecurely supported on the insulated plate (Fig. 4). It will be seen, therefore, that the outer end of the hairspring is constrained to move in general with the armature assembly rec ognizing, of course, that the stops allow a very limited amount of lost motion. Consequently,

rocking movement of the armature assembly Movement in pulse to the outer end of the hairspring, and thence to the balance wheel, in either direction. In the embodiment disclosed the impulse produced by movement of the armature into the energized position tends to wind the spring more tightly While rocking into the deenergized position under the influence of the return spring tends to unwind the hail-spring. It will become apparent as the discussion proceeds that the direction of the spiraling and hence the direction of winding or unwinding could be reversed from that shown without in any way departing from the present teachings. It may further be noted that the balance wheel is coaxial with the mounting of the armature assembly as a Whole. This has a number of beneficial effects worthy of mention. First of all it reduces to a minimum the rotational inertia of the assembly es, increasing the rapidity of rocking in response to external magnetism and spring forces. This is particularly important where the principle is adopted to larger clocks having heavier balance wheels. In addition it facilitates static balancing of the assembly previously alluded to and insures that the impulse force is of maximum value, being applied exactly tangentially to the outer end of the hairspring.

In accordance with the present invention tension in the h-ai'rs'p'ring 6-8 associated with the balance wheel and the consequent movement of the outer end portion of the hairspring is caused to actuate a pair of electrical contacts to produce energization of the electromagnet. In the present instance the contacts include the relatively i'ixed contact It as well as a cooperating movable contact I la which is mounted on the enlargement 74 connected to the hairspring. In practicing the invention means are further provided normally biasing the contacts 16, Ma into the open position so that closure of the contacts takes place only after a predetermined reactive force has been built up in the hairspring 68. In the present instance such biasing is accomplished by means of a leaf spring 18 which is rigidly anchored within the armature assembly by means of a supponting post 19. The outer or movable end of the spring 78 is fixed to the enlargement M and hence to the movable contact Ma. by riveting or any other desired means. Because of the action of the biasing spring 18 the contacts l6, lea will be in. the open position when the balance wheel and hairspring are at rest. The biasing force of the spring l8, however, is made sufiicien-tly weak so that it is readily overcome and the contacts thus allowed to close upon rotation of the balance wheel in the close direction. The latter direction is just opposite to the direction of rocking of the armature when the electromagnetic is energized. The force on the movable contact Ma as a result of balance wheel travel and the force on the relatively fixed contact 1.6 as a result of armature energization thus 1 add together to insure a good electric-a1 connec- With the contacts and associated parts in the armature assembly arranged as shown, the electromagnet will be energized cyclically to cause cyclic oscillation of the armature with a period which is dependent upon the natural period of the balance wheel 64 and its associated hairspring 68. lit is particularly important to note that the balance wheel is freely rotating and that the only torque transmitting connection thereto is the inner end of the hairspring 6%. Escapements are entirely eliminated and the only work which must be done by the balance wheel is the overcoming of bearing friction and windage. Assuming that low-friction bearings are used, the periodicity will be completely unaffected by the frictional forces which may develop in other portions of the mechanism. It might be thought that the movement of the contact 14a at the end of the hairspring would cause power to be drawn from the hairspring and associated balance wheel. While this may be true over a very small portion of the cycle it is to be particularly noted that whatever energy is thus subtracted is resiliently stored and is thus completely returned to the balance wheel and hairspring during a succeeding portion of the cycle.

The operation of the device as thus far described will be made clear upon inspection of the stop motion views shown in Figs. 7-11. The contacts are initially open by reason of the biasing spring 18; consequently the armature 41 is in its upwardly tilted or deenergized position. It will be assumed in order to start the cycle that a counterclockwise impulse is applied directly to the balance wheel as indicated by the arrow. Upon appreciable rotation of the balance wheel in such direction, the hairspring 68 will be increasingly wound and eventually the force at its outer end will be suflicient to deflect the biasing leaf spring 18 so that the contacts 16, Ma are closed. This condition is shown in Fig. 8. The

latter contacts are arranged in series with the coil 40 of the electromagnet so that the electromagnet becomes energized. This of course results in the overcoming of the force of the arm-ature return springs 51, 58 and the rotation of the armature 41 in a clockwise direction. Under this condition as shown in Fig. 9 the teeth on the armature and pole pieces are seen to be in alinement.

The coil and associated magnetic circuit are preferably designed so that the rotation of the armature into its energized position takes place almost instantaneously. There will, of course, be some small delay because of the build-up of magnetic flux but such delay is on the order of a very small fraction of a second and from a practical standpoint is negligible in view of the inertia of the balance wheel. The sudden tangential movement cf the outer end of the hairspring immediately produces a torque impulse on the balance wheel. Assuming that the spring 78 is of proper stiffness readily determined by one skilled in the art, such impulse will occur at about the time that the balance wheel is decelerating toward a stop in the counterclockwise direction with considerable energy stored in the wound hairspring. The impulse, occurring at this time, aids reversal of the balance wheel, as the balance wheel is caused to rotate in a clockwise direction as shown in Fig. 10 under the urging of the hairspring. As an incident to such movement the stress in the hairspring will decrease to a point where it is overcome by th biasing force of the spring 18 thus causing the contacts to open.

The final portion of the cycle is disclosed in Fig. 11. Opening of the contacts has allowed the armature A! to return to its upwardly rocked or deenergized position. This applies a return impulse to the outer end of the hairspring. At the same time, continued rotation of the balance wheel has caused it gradually to decelerate and the kinetic energy of the balance wheel to be stored in the unwound hairspring. As a result .rotation in a clockwise direction ceases and, as indicated by the dotted arrow, reversal takes place, the balance wheel being impelled in a counterclockwise direction by the energy stored in the spring. This, it will be recalled, places the mechanism in the same direction as disclosed in Fig. 7 and the cycle is repeated as long as impulsing voltage is available.

In practicing the present invention, the successive timed oscillations of the armature assembly 34 are caused to drive the gear train 28 and the indicating hands 2?. To accomplish this a ratchet wheel 8!) which is coupled to a worm 30 (Fig. 2) is rotatably mounted on the opposite side of plate 22 from the armature assembly. A portion of the teeth of ratchet wheel to projects through a slot in plate 22. Retrograde movement of the ratchet wheel is prevented by means of pawl 8i. To transmit force from the armature assembly to the ratchet wheel, a pawl in the form of a light leaf spring 82 is employed.

This spring is preferably arcuately shaped, being anchored to the armature assembly at one end and having a free end 83 which bears lightly against the face of plate 22. As the armature rotates under the influence of the electromagnet, the leading edge of the spring 82 is caused to bear against the ratchet wheel advancing the same at the rate of one tooth per cycle.

It should be noted that preferably the ratchet wheel 83 is small in mass and diameter to minimize the effect of flywheel action so that there is no danger of overshooting one tooth even though the movement of spring 3.2 is very rapid. Furthermore, since only one tooth of ratchet wheel to projects through the plate 22 in a posiion to be driven by the spring 32, it is impossible for said spring to pass over the next tooth in sequence and pick up a second tooth thereby advancing the clock at an improper rate. The tooth spacing of the ratchet wheel is intentionally smaller than the travel of the end of spring 82 to insure that one-tooth will be fully advanced, but because of the manner in which the ratchet wheel is mounted in the plate said spring cannot pick up more than one tooth.

Very little energy is required for this drive but it is noteworthy that all of the energy which is required either to move the ratchet, to overcome the restoring force of the springs 51, 58, or to overcome bearing friction, is supplied electrically through a force path which is completely independent of the balance wheel and hairspring. Consequently, the balance wheel is perfectly free to swing under the influence of the hairspring and an order of accuracy may be achieved which is far beyond that of good spring clocks and D. C. electrical clocks of the usual type.

To limit the range of rocking movement of the armature assembly in either direction resilient bumpers are used. The latter are shown in Fig. 2 to include a pair of oppositely extending leaf springs 35, 86 having cup-shaped receptaclesat their ends for receiving small rubber blocks 81, 88. It has been found that this arrangement is not only quiet but also long wearing, absorbing little energy from the system.

If desired, means may be provided for imparting an initial manual impulse to the balance wheel in order to put the clock into operation. Conveniently this is taken care of by means of a spring wiper 95 which is mounted for rotation on a manually twistable shaft 9| so that the lower resilient portion 92 thereof comes into wiping engagement with the shaft of the balance wheel (see Fig. 2). A return spring 93 insures that after the manual twisting force, is released essence the wiper will return to an at-rest position well clear of the balance wheel shaft. Adjustment of the periodicity is effected in the present construction by means of an adjustable arm as which .is rotatable about the axis of the hairspring t3 and which has a slot 95 formed therein which engages the outer convolution of the hairspring. By thisarrangement the convolution is allowed to move tangentially as required for the operation of the contacts 15, Ma. However, at the extremes of the radial contraction and expansion of the spiral spring, the outer convolution is brought against one or the other of the walls of the slot 95 considerably shortening the length of the hairspring during at least a portion of the cycle. The degree of such shortening may be varied with a Vernier-like action by movement of the arm 91!. into an adjusted position to the right or to the left of that shown. This adjusting arrangement does not subtract any appreciable amount of energy from the hairspring 68 since the hairspring is freely floating in the central portion of the slot 95 during the time that the tangential switch-operating movement is taking place.

Although the electrical connections between the contacts 15, 14a and the coil it have already been referred to, they are set forth schematically in Fig. 12. The dual function of the return springs 51, 58 is well brought out. The arcing at the contacts will normally be very minor in view of the small amount of electrical energy which need be supplied from the current source. If desired, however, the arcing which may talze place when the contact is broken may be considerably reduced by a resistor 96 placed across the terminals of the coil it. The value of such resistor is not critical and may readily be determined by one skilled in the art. The voltage surge which tends to occur when contact is broken is further reduced in the construction by means of the short-circuiting copper sleeve id which forms a lag coil preventing any sudden change in the amount of flux threading the magnetic circuit. The lag effect on the speed of the magnet has been found to be negligible. Tests conducted using the wide range of voltage have demonstrated clearly that the armature of movement is satisfactorily fast using voltages which are up to two volts greater or less than the six volt nominal rating. The fact that the mechanism can tolerate such a wide range variation without any sacrifice whatsoever in accuracy makes it possible to use the clock even where the drain on the storage battery or other current source may vary over wide limits. In

this connection it is important to note that this feature enables the clock to be powered by dry cells which may suiier a considerable drop in voltage before they are exhausted.

It will be seen that I have produced a clock which is not only of high inherent accuracy under all normally encountered operating conditions, but which is compact and eminently simple and straightforward of construction. The only hearings in the entire clock which need have minimum friction are those bearings which support the balance wheel. The clock may be thus very cheaply constructed providing considerable comvmercial advantage in a highly competitive field.

I claim as my invention: 1. In an electrical impulse clock an electro- -magnet having a c-shaped pole piece, a springreturned armature assembly mounted within said ,pole piece, said armature assemblycomprising a first mounting plate and a second mounting plate, means for holding said plates in spaced relation, a magnetic armature rigidly mounted therebetween, means for pivoting said armature assembly for balanced rotation about a central axis perpendicular to said plates, a balance wheel between said plates having bearings for allowing rotation about an axis coincident with the central axis of said assembly, a hairspring adjacent said balance wheel and having its inner end coupled thereto, a pair of electrical contacts one of which is arranged for movement by the outer end of said hairspring and the other of which is attached to one of said mounting plates, means for insulating said mounting plates from one another and a pair of hairsprings respectively associated with said mounting plates for not only returning said armature assembly to a deenergized position but also for bringing out connections from said electrical contacts, said contacts being so arranged that closure takes place upon rotation of aid balance wheel in a direction corresponding to the rotation of said armature assembly into the deenergized position to effect timed cyclical oscillation of said armature assembly.

2. In an electrical impulse clock an electromagnet having a pole piece, a spring-returned armature assembly cooperating with said pole piece, said armature assembly comprising a first mounting plate and a magnetic armature plate, means for holding said plates in spaced relation, means for pivoting said armature assembly for balanced rotation about a central axis perpendicular to said plates, a balance wheel adjacent said magnetic armature plate having bearings for allowing rotation about an axis coincident with the central axis of said assembly, a hairspring associated with said balance wheel and having its inner end coupled thereto, a pair of electrical contacts one of which is arranged for movement by the outer end of said hairspring and the other of which is attached to one of said plates, means for insulating said plates from one another and a pair of hairsprings respectively associated with said plates for not only returning said armature assembly to a deenergized position but also for bringing out connections from said electrical contacts, said contacts being so arranged that momentary closure takes place upon rotation of said balance wheel in a direction corresponding to the rotation of said armature assembly into the deenergized position to eiiect timed cyclical oscillation of said armature assembly.

3. In an electrical impulse clock an electromagnet having a pole piece, an armature assembly co-operating with said pole piece, said armature assembly comprising a first mounting plate and a magnetic armature plate, means for supporting said plates in spaced relation, means for pivoting said armature assembly for balanced rotation about a central axis, a balance wheel adjacent said magnetic armature plate having bearings for allowing rotation about an axis 00- incident with the central axis of said armature assembly, a hairspring associated with said balance wheel and having its inner end coupled thereto, a pair of electrical contacts one of which is arranged for movement by said hairspring and the other of which is attached to one of said plates, means for insulating said plates from one another and a spring associated with said armature assembly for returning said armature assembly to a deenergized position, said contacts being so arranged that closure takes place upon rotation of said balance wheel in a direction corresponding to the rotation of said armature assembly into the deenergization position to energize said electromagnet and effect timed cyclical oscillation of said armature assembly.

4. In an electrical impulse clock an electromagnet having a pole piece, an armature assembly co-operating with said pole piece, said armature assembly comprising a first mounting plate and a second mounting plate, means for holding said plates in spaced relation, a magnetic armature rigidly mounted therebetween, means for pivoting said armature assembly for balanced rotation about a central axis perpendicular to said plates, a balance wheel between said plates having bearings for allowing rotation about an axis coincident with the central axis of said assembly, a hairspring adjacent said balance wheel and having one end coupled thereto, a pair of electrical contacts connected in circuit with said electromagnet, one of said contacts being arranged for movement by said hairspring and REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,772,556 Poole Aug. 12, 1930 2,420,827 Kennedy May 20, 1947 FOREIGN PATENTS Number Country Date 188,079 Switzerland Mar. 1, 1937 682,134 Germany Oct. 9, 1939

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