US2371387A - Electric clock - Google Patents

Description

March 13, 1945. J. FlNK 2,371,387

ELECTRIC CLOCK Filed April 28, 1945 I INVENTOR.

, rfan Rain BY V Patented Mar. 13, 1945 ELECTRIC CLOCK Jean Fink, Delavan, Wis., assignor to George W. Borg Corporation, Chicago, 111., a corporation of Delaware Application April 28, 1943, Serial No. 484,830

7 Claims.

The present invention relates in general to electric clocks, and more in particular to electric clocks of the type in which an oscillating balance drives the clock train and in which the balance is maintained in oscillating condition by means of an electromagnet which is intermittently energized under control of the balance.

The object of the invention is the improvement of a clock of the foregoing type by the provision of a new and improved drive mechanism through the medium of which the oscillatory motion of the balance is converted into the unidirectional motion of the clock train.

A special object is a self-starting drive mechanism having features which insure reliable starting of the clock under all conditions.

The invention will be described in detail herelnafter, reference being made to the accompanying drawing, in which- Fig. 1 shows the essential parts of a clock embodying the invention; and

Fig. 2 is a section on the line 2-2, Fig. 1, showing the improved drive mechanism.

The invention may be employed in any electric clock of the general type hereinabove described. For a complete disclosure .of a suitable clock of this type reference is made to United States Patent No. 2,356,983, granted August 29, 1944. In view of the description in said patent, it will not be necessary to explain in detail the construction and operation of the whole clock, and the description will be limited, therefore, to the improved drive mechanism, except for such brief explanation of other parts as may be desirable for an understanding of the invention.

Referring to Fig. l, the various parts of the clock are mounted on a frame which comprises the front plate H), the plate II, and the three posts l2, l3 and Hi. The front plate I!) may be circular in/shape, as shown, and has the three posts secured to it by a riveting or staking operation. The plate H is of irregular shape and rests on shoulders formed on the posts I2, 13

and I 4, whereby it is maintained in the proper spaced relation to plate It). The posts l2, l3 and I4 are threaded above the shoulders and nuts are used to clamp plate I l in position.

The balance comprises a ring 15, of brass or other suitable material, and a four-pole armature which also functions as a support for the ring. Two of the armature poles are indicated at l6 and 16. The armature is a sheet metal stamping of high grade magnetic material and is mounted in suitable manner on the balance arbor H. The balance arbor has a, bearing at one, end in the down-turned portion l8 of the frame plate II and at the other end has a bearing supported on the balance cock I 9. Associated with the balance is the usual hairspring, indicated at 20.

The electromagnet for oscillating the balance includes a core 2|, a winding 22, and the Pole pieces 23 and 24. The pole pieces are supported on the frame plate H, and for this purpose are provided with slots whereby they may be forced on to the two cars by means of which the frame plate is supported on posts l2 and l3. The pole pieces are assembled to the frame plate before the latter is assembled on the posts. The pole pieces extend inwardly past the posts l2 and 13, whereby their respective free ends are brought into operative relation with the four-pole armature which forms part of the balance. The opposite ends of the pole pieces, extending upward from the plate H, are bifurcated to receive the core 2!, and engage shoulders formed near the ends of the core, against which they are clamped by nuts, as shown. The parts are so proportioned that the heads of the spool on which the Winding 22 is carried rest on the frame plate II. The reference character 25 indicates a condenser which is connected in parallel with the winding 22.

The circuit of the electromagnet is controlled by means of a pair of contact members 26 and 21.

The contact member 26 is a flexible spring and is supported in suitable manner on the post I3. The contact member 21 is the fixed member of the pair and is supported on one of the heads of the magnet spool. The contact spring 26 is normally out of engagement with the contact member 21; that is, spring 26 is tensioned in the proper direction to break the contact. During oscillations of the balance the spring 26 is actuated periodically into engagement with contact member 21' by means of an armature 28 secured to the spring and a small permanent magnet 29 mounted on the balance arbor H. The magnet 29 also functions, with the initial aid of the hairspring, to restore the parts and maintain them in a definite normal position as shown in Fig. 2, whenever the clock stops due to the current supply being disconnected. In this position of the parts the contact between the spring "26 and contact member 2'! is closed.

The oscillating balance operates the clock train by means of drive mechanism which will now be described, reference being had to Figs. 1 and 2 of the drawing.

Mounted on the balance arbor I1 adjacent the four-pole armature of the balance there is a roller 39, having the pin .3l projecting from the side thereof. The pin 3| may be of hardened steel or other suitable material, and lies in the fork which is provided at the end of arm 34 of the pallet lever. The latter part is shaped as shown in Fig. 2 and comprises the integrally formed arms 34 and 35 and the short tapered upright arm 40. The pallet lever is mounted on the shaft 38 which has a bearing at one end in the bracket 42 and at the other end in the upturned portion 43 of the plate ll. of the pallet lever carries a guard pin 33, which is located within the recess 32 in the roller 30 when the parts are in the position shown. The bracket 42 extends upward from the frame plate D, to which it is secured by screws, as indicated.

The pallet lever is provided with the twopal lets 36 and 31, which may be hardened steel pins, by means of which the so-called escape wheel 35 is rotated. The escape wheel is mounted on an arbor 44, which has a bearing at one end in the bracket 42 and at the other end in the post l4. Only a part of the arbor 44 can be seen in Fig. 1, since it is located below frame plate H and directly underneath the arbor 38. The arbor 44 drives the clock train. by means of the. worm 4t, whichengages the. gear wheel 46, the latter being the first wheel of the train. The remainder of the clock train is not shown, but is of the usual and known construction.

The reference character 4| indicates a light spring, which is mounted on post l2. The. spring 4| is formed near the. end. so as to piovide a V-shaped projection 41' which bears on the tapered end of the arm 40' of the pallet lever. Spring 4| is. tensioned downward, but applies no rotative force to the pallet-leverbecause the latter is on dead center.

The complete: clock includes a back plate (not shown) which isv mounted on posts- |2, I3 and M in spaced relation to plate II. For this purpose suitable tubular spacers. may be placed on the threaded portions. of the posts above the nuts shown, and. the back plate may be held in place by additional nuts- The details of this construction areimmaterial. to the invention but are fully disclosed in the patent previously referred to. The back plateis provided with. an insulated terminal to which one pole of thebattery or other current source is connected. This terminal extends through the. back plate and engages the coil terminal 48 mounted. on one of the heads of the magnet spool. The spool may be of molded. construction, in which. case the coil terminal 48 and" the contact. member 2'! are embedded in the two spool heads, respectively.

. From the foregoing. the circuit of the electromagnet will. be; readily understood. It extends from one pole-of the battery to the back plate terminal, and thence by way of the coil terminal 48-, .winding, 22. of the electromagnet, contact member 21', and contact spring. 26- to the frame. of the clock which is connected in any suitable manner to the other pole of. the battery.

The operation of the clock. will now be. explained, with special attention tothe functioning of the drive-mechanism.

It will be assumed to start with that. the battery or other source ofv current is disconnected,

The arm 34.

fork and the motion of the balanceis not impededv which meansof coursethat the clock hasstopped.

When the clock is notrunning the various parts of the drive mechanism are inthe position in which they appear in Fig. 2, as previously mentioned. The contact 26-41 is closed, and the pallet lever is in itsmid-positionwith the spring 4| under tension.

4 When the battery is connected a flow of current over the previously traced. circuit isestablished and the electromagnet is energized. The resulting magneticfield passes through the:ar-ma-- ture which forms part of the balance, and-arotative force is thus applied to thebalance which tends to rotate it. in one. direction or the other. Therotation of the, balance tensionsv the hair-- spring and also brings about the release of armature 28 and the opening of the circuit of the electromagnet by the disengagement of contact spring 26 and contact member ET. Thebalance then rotates in the opposite direction and as the ma net 29 passes the armature 2B the latter is attracted and the circuit of the electromagnet is again closed. The electromagnet thus receives another impulse of current, and the operation continues in this way until in a few seconds the balance is oscillating with its normal amplitude, the electromagnet being energized momentarily during each beat as the magnet attracts armature 28 to close the circuit.

The starting of the clock is facilitated by the action of spring 4|. As the balance starts to rotate, the roller 30 rotates also and the pin 3| rotates the-pallet lever. Assoon as the latter has moved oii dead: center its rotation is accelerated by the spring 4|, due to the V-shaped projection 41 engaging one of the tapered sides of arm 46. Thus the pallet lever delivers a secondary impulse to the. roller 38 by means of the forked arm 34 and pin 3|, which tends to augment the initial swing. of the balance. The power for thesecondary impulse is. stored in the spring 4|: by the magnet 29, when it brings the. parts to rest in the position shown in Fig. 2. When the clock. is running the spring M is tensioned during the first half ofeach beat,.the power being suppliedby the oscillating balance, and during. the last half of each beat thespring 4| assists in rotation of. the clock train, thus returning the power to the system. 1

The pallet lever is shown in the intermediate position, in which it stands when theclockisstopped. When the clock is running, the pallet lever oscillates. between. two extreme positions in. which the pin 3|v on the roller 3E! is clearof the by the drive mechanism. The drive is effected. as the balance passes through a short range of movement at the middle of each beat, and at times when it receivesimpulses from/theelectromagnet. The driving operation may'now becon sidered more indetail.

It. may be assumed that the balance and roller 30 are rotating in the direction shown by the arrow associated with the roller, having. completed one-half of. thebeat inthisdirection. The pin 3|. has entered the fork on arm 34- of the pallet lever and has rotated the palletlever to the position shown, tensioning the spring 4| As the rotation of the roller 30 continues, the pin 3| continues to rotate the pallet lever and. very shortly the pallet pin 3'! engages the toothv 50 of the escape wheel 39.. The continued. rotation. of the pallet lever now rotates the escape-wheel, the power stored in spring 4'! being of assistance in the rotation, as previously mentioned. When. the pallet 31 arrives nearly at the bottom of the notch between tooth 50 and the next. adjacent tooth, the pin 3| on roller 30 leaves the fork and the balance and. roller continue their excursion. in a counter-clockwise direction. The escape wheel has been advanced an angular distance equal to one-half the tooth spacing.

During the motion of the roller and pallet lever just describedthe guard pin- 33 on arm3'4 ofthe. pallet lever moves away fromthe balance arbor Hand as the pin 3| leaves the fork the distance between the guard pin 33 and the center of arbor I1 is slightly greaterthanthe radius of the roller; that is, the. pin 33 has moved far enoughso that it does not bear on the periphery of the roller,

The pallet lever is held in this position, with guard pin 33 clear of the roller, by the spring H. The guard pin is provided to prevent any displacement of the pallet lever, such as might be caused by an accidental shock, which would prevent the pin 3| from properly entering the fork on the return movement of the balance; but in the normal operation of the clock the guard pin is held just clear of the roller, which eliminates the drag that would otherwise be present.

The rotation of the balance and roller 30 in the direction indicated is stopped by the hairspring in the usual manner and the rotation in the opposite direction begins. As the balance approaches the middle of its beat the pin 3| enters the fork on arm 34 of the pallet lever and rotates it also. Shortly after the pallet lever passes its midposition, in which it is shown in Fig. 2, the pallet pin 36 engages the sloping face of tooth 5| of the escape wheel 39 and the continued movement of the pallet lever rotates the wheel in the same direction as .before and through the same angular distance. As the pallet 36 arrives nearly at the bottom of the notch between tooth 5| and the next adjacent tooth the pin 3| leaves the fork and the balance and roller continue their rotation. The pallet lever is held in this position by the spring 4|, until the pin 3| again enters the fork upon the next beat of the balance.

The operation continues in this manner as long as power is supplied to the clock. When the battery is disconnected, as by opening of the battery circuit at some point outside the clock, the

balance continues to oscillate, but with gradually decreasing amplitude, until eventually the mutual attraction between the magnet 28 and the armature 28 is sufiicient to overcome the inertia of the balance and the parts are brought to rest in the position in which they are shown. In this connection it should be noted that the rotative force due to the attraction between magnet 29 and armature 28 is considerably greater than the force which can be applied to the pallet lever by spring 4|, which insures that the pallet lever will be brought to mid-position each time the clock stops.

The invention having been described, that which is believed to be new and for which the protection of Letters Patent is desired will be pointed out in the appended claims.

I claim:

1. In a drive mechanism for a clock, a toothed wheel, a pallet lever for rotating said wheel responsive to oscillation of the lever, means including a balance for oscillating said lever, a spring acting on said lever and tending to rotate the same except when the lever is in midposition, and means including a permanent magnet for returning said pallet lever to mid-position against the tensibn of said spring whenever the balance comes to rest.

2. In a drive mechanism for a clock, a balance supported on an arbor and adapted to oscillate, a pallet lever adapted to be oscillated responsive to oscillation of said balance, a toothed wheel adapted to be rotated by said pallet lever, a spring acting on said pallet lever and tending to rotate the same to one or the other of the extreme positions which the pallet lever assumes during oscillation, said spring and lever being so arranged that the spring exerts no rotative force on the lever when the latter is in a position midway between said extreme positions, and a permanent magnet on the balance arbor cooperating with an armature fixed against angular motion around said arbor to maintain said pallet lever in mid-position until said balance starts oscillating.

3. In a drive mechanism for a clock, a toothed wheel included in the clock train, a pivoted pallet lever for rotating said wheel responsive to oscillation of the lever, means for oscillating said lever on its pivot, a spring acting on said pallet lever and tensioned during the first part of an oscillation of the pallet lever in one direction, said spring being effective during the latter part of said oscillation to apply force to the pallet lever to assist in driving said wheel, and means eifective when the clock stops for partly oscillating said lever to tension said spring.

4. In a drive mechanism for a clock, a toothed wheel for driving the clock train, a pivoted pallet lever for rotating said Wheel responsive to oscillation of the lever, the said lever being ineffective to drive said wheel until the lever has passed the halfway point in each oscillation, means including a balance for oscillating said lever, a spring acting on said lever during the last half of each oscillation to aid the balance in completingsuch oscillation, said spring being tensioned by said balance and lever during the first half of each oscillation of the lever, and means effective to complete a half oscillation of said lever and tension said spring if the balance stops oscillating.

5. In a drive mechanism for a clock, a toothed wheel for driving the clock train, a pivoted pallet lever for rotating said wheel responsive to oscillation of the lever, the said lever being effective to drive said wheel only during the last half of each oscillation, means including a balance for oscillating said lever, a spring associated with said lever for receiving and storing power from the balance during the first half of each oscillation which is applied to said lever to aid in driving said wheel during the last half of each oscillation, and means for insuring that said lever comes to rest in mid position with said spring under tension when the clock stops.

6. In a self-starting clock having a balance, means including an electromagnet for causing the balance to oscillate, drive mechanism responsive to oscillation of the balance for advancing the clock train, means for starting and stopping the clock by closing and opening the circuit of said electromagnet, and means associated with said drive mechanism for storing power when the clock stops and for applying at least a part of such power to the balance when the clock is started again.

7. In a self-starting clock, a balance supported on an arbor, an electromagnet, a permanent magnet on the balance arbor controlling the circuit of said electromagnet to cause the balance to oscillate, drive mechanism responsive to oscillation of said balance for advancing the clock train, means for starting and stopping the clock by closing and opening the circuit of said electromagnet at a point outside the clock, said permanent magnet being effective whenever the clock isstopped to bring the balance and a part of said drive mechanism to predetermined positions, and means associated with said drive mechanism and responsive to movement of said part thereof to said position to store power which is applied to the balance when the clock is started.

JEAN FINK.

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