US3002336A - Electrically driven timing mechanisms - Google Patents

Description

Oct. 3, 1961 H. .1. LOVEGROVE ELECTRICALLY DRIVEN TIMING MECHANISMS Filed Nov. 25, 1957 TIMING MECHANI CONTROL ESCAPEMENT DEVICE RELEASE f/e/zry (75.767272 [aye rave i 75AM a Patented Get. 3, 1961 3,002,336 ELECTRICALLY DRIVEN TIMING MECHANISMS Henry Joseph Lovegrove, Hadley Wood, Barnet, England, assignor, by mesne assignments, to Sangamo Electric Company, Springfield, 111., a corporation of Delaware Filed Nov. 25, 1957, Ser. No. 698,778 Claims priority, application Great Britain Dec. 20, 1956 4 Claims. (Cl. 5826) This invention relates to electrically driven timing mechanisms and is more particularly concerned with devices of the type known as carry-over clock mechanisms in which a time piece escapement is driven through a suitable gear train from an energy-storage means, such as a main driving spring, which is arranged to be continuously supplied with energy from an electric motor and in which synchronising means operated by a frequency-controlled alternating current supply, e.g. that of the public supply mains which are also used for energising said electric motor, are provided for normally maintaining the vibration of the time piece escapement at a frequency which is determined by the frequency of said alternating current supply.

A variety of devices of this type are already known including one in which forced oscillation of the balance wheel of the escapement is effected by the synchronous electric motor which is used for effecting continuous winding of a main driving spring forming the energy storage means from which the escapement is driven. In this prior art arrangement the motor is caused to rock the outer end of the hair spring associated with the escapement mechanism in a circumferential manner. Such a known device, while satisfactory for so long as the primary frequency-controlled alternating current supply is maintained, can prove disadvantageous in the event of current failure due to the fact that the position at which the hair spring rocking member comes to rest upon current failure, can be anywhere within its range of rock-ing movement since such position is dependent only upon the particular instant of failure of the supply. As a result, the exact position of the outer end of the hair spring during the carry-over time period when the timing mechanism is running on the stored energy of the wound spring alone without any superimposed synchronisation may likewise be anywhere within the range of rocking movement of the aforesaid hair spring rockingmember. Unless, by fortuitous circumstances, the current failure occurs at an instant when the synchronising member is near the optimum or midpoint of its travel, the balance wheel tends to run off beat which, apart from other disadvantages, may cause bad time keeping during the carry-over period.

The object of the present invention is to provide an improved and simplified construction of carry-over clockwork timing mechanism in which such disadvantages are materially reduced or even avoided.

In accordance with the broadest aspect of the present invention the mechanical synchronising of the escapement mechanism of the clockwork by the time-controlled means operated from the frequency-controlled alternating current supply is arranged to produce a periodic radial movement of the point of regulating connect-ion at the outer end of the hair spring instead of a ci-rcurnferential movement as hither-to.

In order that the nature of the invention may be more readily understood practical embodiments thereof will now be described by way of illustrative example with reference to the accompanying drawings, in which:

FIG. 1 is a block schematic view of the basic layout of the system according to the present invention.

FIG. 2 is a fragmentary elevational view of the essential parts of the synchronising mechanism of one arrangement according to the invention.

FIG. 3 is a fragmentary plan view of the par-ts shown in FIG. 2, and

FIG. 4 is a fragmentary elevational view, similar to FIG. 2, showing a modified arrangement embodying the invention.

Referring first to the block schematic drawing of FIG. 1, a synchronous electric motor 10 is arranged to be supplied from a frequency-controlled AC. supply source 11 which is conveniently the public supply mains. This motor 10 is coupled through suitable means such as a friction type slipping clutch 12 to the spring barrel 13 of clockwork timing mechanism so as to effect winding of the clock spring within the barrel 13 at a rate which is considerably greater than, for example twice, the rate of unwind of such spring during its normal operation of driving the timing mechanism 14 at the correct time keeping speed. The electric motor 10 is also arranged to operate a control device 15 which provides a regular mechanical movement, e.g. in the form of 16,200 vibrations per hour, which is compatible with the correct time keeping movement of the escapement release mechanism 16 of the clock, which latter controls the unwind speed of the spring barrel 13 in the usual and well known manner. The mechanical movement provided by the control device 15 operates to constrain the release mechanism 16 to operate at the predetermined and required speed for correct time keeping. The slipping clutch 12 may be incorporated with the spring barrel 13.

Referring now to FIGS. 2 and 3 of the drawings, 20 indicates a shaft mounted in suitable bearings in the framework 32 of the clockwork timing mechanism and connected by way of gearing (not shown) of an appropriate speed reduction ratio to the spindle of the synchronous motor 10 (FIG. 1). Exemplary forms of this speed reduction gearing are shown in prior patents to Arthur F. Poole Nos. 2,077,007 and 2,088,972. This shaft 20 carries a disc 21 secured thereon having an eccentric pin 22. The pin 22 operates within the slot 23 of a forked end of a rocking lever 24 which is pivotally mounted at 25 to the stationary framework 32 of the clockwork mechanism. The opposite end of the lever 24 is also forked to provide a slot 26 therein which receives a pin 27 secured to a slide bar 28 which is arranged for reciprocatory movement in a U-shaped guide channel 29. This guide channel 29 has diametrically opposite upstanding arms 29a at its ends, through which are provided horizontal guide slots 2% in which the slide bar 28 has free sliding movement. The guide channel 29 is mounted, in a manner similar to that of the usual time-adjusting arm of clockwork mechanism, by friction clamping means so as to be adjustable angularly about the axis of the balance wheel staff 30, the latter being carried in suitable bearings of the usual form such as that shown at 31 in FIG. 3, carried by the stationary framework 32 of the clockwork mechanism. This angular adjustability of the guide channel 29 and slide bar 28 is of relatively limited extent owing to the necessity of the slide bar 28 remaining in positions moderately close to right angle relationship to the slotted end 26 of rocking lever 24. Such limited angular adjustability of the guide channel '29 and slide bar 28 may be obtained by mounting the guide channel 29 on the upper end of the threaded bearing 31, which hearing may then be rotated in its threaded mounting in the framework 32 whenever it is desired to effect the angular adjustment of the guide channel and slide bar, such rotation of the threaded bearing 31 being relatively small.

The slide bar 28 carries, at its outer end, a projecting lug 33 which extends through a suitable aperture in the framework side plate 32 and is provided at its inner free end with a notch 34 for receiving the outermost turn of the hair spring 35, the inner end of which is secured in the usual manner to the balance wheel staff 39. The stafi? 30 has the normal balance wheel 36 secured thereto together with an eccentric pin or pins 36a forming part of escapement mechanism of usual form and com-- prising also a pallet lever 37 mounted upon the pallet staff 38 which is also journalled in the stationary framework 32 of the timing mechanism. The opposite end of the pallet lever 37 cooperates with the escape wheel 39 which is geared in the usual way to the timing gear train and the spring barrel 13. In the exemplary or wellknown form of escapement mechanism illustrated in the drawings, two eccentric pins 36a play in a notched area defined between two spaced fingers 37b which project from the adjacent end of the pallet lever 37. Also projecting from this end of the pallet lever 37, between the two laterally spaced fingers 37b, is a third intermediate finger 37d which is bent upwardly (FIGURE 3) to clear the tops of the eccentric pins 36a. Mounted on the balance wheel staff 30 is a hub 30a having an arcuate recess 30b therein through which swings this upwardly bent third finger 37d.

In normal operation of the device, i.e. when the supply mains 11 are operative, the electric motor operates continuously to wind the spring barrel 13 and thereby to provide a source of stored energy for the timing mechanism, such spring barrel 13 being operative to drive the timing mechanism 14 through the usual reduction gear train and thereby to cause vibration of the escapement mechanism at a predetermined frequency, set by appropriate adjustment of the angular position of the anchored end of the hair spring 35 to be as near as possible correct for proper time keeping purposes. guide channel 29 carrying the slide bar 28 is free for adjustment in the angular direction so as to determine the correct circumferential anchorage point for the outer end of the operative portion of the hair spring 35. The balance wheel 36 is constrained to oscillate at the correct predetermined and time-controlled frequency, as set by the frequency of the supply mains 11, by the continuous oscillation which is imparted to the rocking lever 24 due to the action of the eccentric pin 22 which is driven from the synchronous motor 10.

The oscillation of the lever 24 causes a corresponding continuous reciprocation of the slide bar 28 whereby the point of regulating connection at the outer end of the hairspring is moved in and out in a radial direction, once for each oscillation of the lever 24. This reciprocation of the slide bar 28 is effected at whatever angular position the guide channel 29 and such slide bar have previously been set in order to effect proper time keeping of the escapement mechanism under the driving power provided by the spring barrel 13. This radial movement imparted to the outer end of the hair spring 36 operates to lock the vibration frequency of the escapement to a frequency which is governed by that of the supply mains 11 over a range of frequencies which are centered substantially upon the free vibration frequency of the escapement mechanism.

In the event of failure of the supply mains 11, the eccentric pin 22 will stop at some random angular position dependent upon the instant of failure of the supply. In spite of this, the slide bar 28 is always in the correct angular relationship for proper time keeping of the escapement mechanism and the only disturbing effect is that the lug 33 to which the hair spring is anchored may be a little too near or a little too far from the axis of the balance wheel staff 30 thereby to cause slight distortion of the hair spring 35. The ill-effect of this, however, is relatively small compared with the ill-effect of incorrect circumferential positioning of the anchorage point of the outer end of the hair spring such. as could occur in the prior art arrangement previously IQE XQQ K The- FIG. 4 shows a modification in which the eccentric pin 22 carried by the disc 21 secured to the shaft 20 which is coupled by gearing to the synchronous motor 10, is connected by way of a connecting rod 49 directly to the pin 27 which is carried by the slide bar 28. The manner of operation of this modification is self-evident following the description already given of the embodiment shown in FIGS. 2.and 3.

I claim:

1. In escapement apparatus of the class described for carry-over clock mechanism driven by a synchronous electric motor, the combination of a spirally Wound hair spring, a guide member mounted adjacent to said hair spring, a synchronizing slide mounted for rectilinear sliding motion in said guide member, transmission means for transmitting synchronizing motion from said synchronous electric motor to said synchronizing slide, hair spring engaging means carried by said synchronizing slide for engaging the outer convolution of said hair spring at a point removed from the outer end extremity of said hair spring, and means rotatably mounting said guide member for rotation concentrically of the axis of said hair spring for enabling the point of engagement of said hair spring engaging means to be rotatably adjusted to different points around the outer convolution of said hair spring.

2. In escapement mechanism of the class described driven by a synchronous electric motor, the combination of a spirally wound hair spring, a guide member mounted adjacent to said hair spring, a synchronizing slide mounted for sliding motion in said guide member, transmission means for transmitting synchronizing motion from said synchronous electric motor to said synchronizing slide, 'hair spring engaging means carried by said synchronizing slide for engaging a convolution of said hair spring at a point removed from the outer end extremity of said hair spring, and means adjustably mounted said guide member enabling said guide member to be moved to different adjusted positions so as to enable the point of engagement of said engaging means to be adjusted to different points along the engaged convolution of said hair spring.

3. Escapement mechanism for clock mechanism driven by a synchronous electric motor, said escapement mechanism comprising a spirally wound hair spring, a guide member mounted adjacent to said hair spring. a synchronizing slide mounted for rectilinear sliding motion in said guide member, transmission means for transmitt ng synchronizing motion from said synchronous electric motor to said synchronizing slide, hair spring engaging means carried by said synchronizing slide for engaging the outer convolution of said hair spring at a point removed from the outer end extremity of said hair spring, said slide having synchronizing sliding movement along a line extending substantially radially of said hair spring, and means rotatably mounting said guide member for rotation substantially concentrically of the axis of said hair spring for enabling the point of engagement of said hair spring engaging means to be rotatably adjusted to different points around the outer convolution of said hair spring.

4. In apparatus of the class described provided with a frequency controlled alternating current synchronizing means, the combination of an escapement mechanism comprising a spirally wound hair spring having its outer extremity anchored to an outer fixed point of attachment, a movable member having hair spring engaging means for engaging an outer convolution of said hair spring at a point removed from the outer fixed point of attachment of said hair spring, motion transmitting means connecting said frequency controlled Synchronizing means with said movable member for synchronously moving said 6 movable member, and adjustable mounting means for References Cited in the file of this patent adjustably mounting said movable member so as to en- UNITED STATES PATENTS able the path of movement of said movable member to 2,077,007 Poole Apr. 13, 1937 be varied whereby the point of coactron of said hair 2,088,972 Poole Aug 3 1937 spring engaging means with said hair spring can be 5 adjusted to difierent points around the engaged convolu- FOREIGN PATENTS tion of said hair spring. 498,113 Great Britain Ian. 3, 1939

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