US2183655A

US2183655A - Means for adjusting vibrating systems

Info

Publication number: US2183655A
Application number: US78360A
Authority: US
Inventors: Edmund R Morton
Original assignee: Bell Telephone Laboratories Inc
Current assignee: AT&T Corp
Priority date: 1936-05-07
Filing date: 1936-05-07
Publication date: 1939-12-19
Anticipated expiration: 1956-12-19

Description

Dec. 19, 1939. E. R. MORTON MEANS FOR ADJUSTING VIBRATING SYSTEMS Filed llay 7, 1936 m M a M P. m

lNVE/VFOR I ERMORTQN B! 1 ATTQQNEY Patented Dec. 19, 1939 MEANS from ADJUSTING VIBRATING SYSTEMS Edmund R. Morton, New York, N. Y., assignor to Bell Telephone Laboratories,

Incorporated,

New York, N. Y., a corporation of New York' Application Mayl, 1936, Serial No. 78,360'

Claims.

This invention relates ,to apparatus for the optical calibration of oscillating members and more particularly relates to a device for the adjustment of rate of oscillation .of the balance 5 wheel of a timepiece before its assembly in the timepiece.

A very important feature in the manufacture of timepieces is their accurate adjustment. In the case of high grade watches, it isnot unusual to prolong the comparison of the manufactured timepiece with a standard timepiece over a period of clays or perhaps weeks. In the case of more inexpensive watches, the time taken for correct adjustment materially increases the cost 16 of manufacture and thus the manufacturer is faced with the problem of either spending too much time adjusting the watch in view of the selling price, or turning out watches which are not properly adjusted.

An object of the'present invention, therefore, is an adjusting apparatus which will permit the rapid adjustment of the rate of oscillation of a vibrating system such as the balance wheel of a watch before installation.

A further object of the invention is an apparatus for observing substantially instantaneously the deviation of the resonance of a vibrating system from the desired resonance.

In accordance with the present invention these and other objects are attained by employing a device comprising driving means for oscillating the vibrating system to be regulated at the desired frequency, and then viewing the vibrating system in stroboscopic flashes of a lamp periodically ac- 5 tuated by the driving means. The vibrating'system although driven in synchronism with the lamp flashes will ordinarily appear, when viewed in those flashes, to be out of phase with the driving means. A suitable adjustment of the vi- 40 brating system is then made until the vibrating system is brought into phase with the driving means,

In applying this invention to timepiece regulation, the balance wheel of the timepiece is os- 45 cillated at the desired predetermined frequency and viewed in the lamp flashes. Any apparent difference in phase is corrected by changing the effective length of the hair spring associated with the balance wheel. When there appears to be 60 no difference in phase when viewed in the lamp flashes the hair spring of the timepiece is correctly adjusted.

In the preferred form of the invention the testing and regulating device comprises a syn- 55 chronous motor whichby means of a rack and pinion drives a loose coupling with an oscillatory movement having a frequency equal to the desired frequency of the balance wheel. At the same time the motor periodically closes contacts to cause a neon lamp to flash atthe moment of 5 maximum velocity during each half cycle of the oscillatory movement. For the adjustment of the oscillating member of a timepiece the shaft of the balance wheel with its attached hair spring is placed in the loose coupling in such a manner 10 thatthe balance wheel is forced tooscillate at the frequency of oscillation .of the loose coupling. If the natural period of oscillation of the I balance wheel is different from the impressed frequency. of oscillation there will be a difference 16 in phase between the loose coupling and the balance wheel and by observing the balance wheel during successive light flashes its phase difference will be'indicated by the failure of theimage of the balance wheel to appear stationary. When 20 the effective length of the hair spring is adjusted to cause the image of the balance wheel to appear stationary the phase difference is substantially zero and the natural period of oscillation of the balance wheel is equal to that of the 25 driving force. This, therefore, indicates that the hair spring and balance wheel are correctly adjusted and are ready for installation as a part of a watch movement.

This invention will be more clearly understood 30 from the following detailed description and attached drawing in which:

. Fig. 1 is a schematic view of the-essentials of the apparatus of' this invention for regulatin the oscillation of a balance wheel; and Fig. 2 shows a stroboscopic means for viewing the vibrating member.

'As shown in the drawing, a balance wheel 5 and its associated hair spring 6 are mounted on the balance wheel shaft 1. One conical end of shaft 1 is located in a suitable bearing in plate 8 and the other conical end of the shaft rests in a suitable bearing held by sleeve 9 which is attached to a separate shaft l5. Sleeve 9 with itsbearing constitutes a loose coupling between the driving shaft l5 and the balance wheel shaft I.

The outer end of the hair spring 6 is clamped at the point I0 by a suitable clampingmember which may comprise a wedge block I 2 and a flat block I3 inserted in a slot in a plate l4 so that the effective length of the spring 6 can be readily adjusted.

The loose coupling member 9 is mounted on shaft 15 and is oscillated by gear [6 and rack I1. The rack I1 is driven by a suitable means such as "a constant speed motor l8 which acts through its shaft l9, gears 20, 21 to rotate cam 22 at a desired constant speed. Cam 22 engages rack arm 24 by means of its crank pin 23 so that the rotation of cam 22 imparts a reciprocating movement to rack i1. It is to be assumed that the rotationalfrequency of cam 22 is made equal to thedesired natural frequency of oscillation of the balance wheel and its hair spring '6.

Cam 22 also carries two diametrically

opposite projections

25 and 26 on its circumference which serve to close electrical contacts 29 and complete a circuit through battery 21 twice per cycle of oscillation of rack l1. Each time the circuit through battery 21 is closed a step-up transformer 3!] serves to supply a brief current impulse to the neon lamp 28 to cause it to flash momentarily and illuminate balance wheel 5 as more clearly shown on Fig. 2. The closure of contacts 29 is preferably timed to occur at the middle of each swing of rack l1, that is, at the moment of its maximum velocity and a telescope or lens system 3| is preferably provided as shown to facilitate observing the position of the balance wheel.

On starting the motor I8 the balance wheel assembly due to loose coupling 9 will be driven at the desired frequency of oscillation even though its natural frequency of oscillation differs from that of the driving force. The balance wheel will be illuminated once each half cycle at the moment when the driving rack I1 is at its maximum velocity. If the natural frequency of oscillation of the balance wheel assembly differs from the frequency of the driving force the balance wheel will not oscillate in phase with the driving force and hence the balance wheel as viewed throughthe telescope 3| by the lamp flashes will not appear stationary and the image of a selected spoke of the wheel for one half cycle will not be superposed on the image of the spoke for its second half cycle of oscillation. That is, if the natural frequency of the balance wheel differs from the frequency of the drive, the spoke will appear alternately at two positions. If the length of the hair spring is now changed the amplitude of the oscillation will be reduced if the adjustment is in the wrong direction; but if in the proper direction the angle between the two alternate positions of the spoke will be reduced until the two images are superposed when the correct length of the hair spring is reached. Therefore to obtain the correct adjustment hair spring 6 should be pulled through the clamp until the balance wheel appears to be stationary and the two images superposed when viewed in the lamp flashes. When this result is obtained this indicates that the balance wheel is now oscillating in phase with the driving force and that the hair spring is, therefore, correctly adjusted to the proper length to have the desired natural period of oscillation. The spring 6 may then be suitably marked to indicate the clamping point 10 and the balance wheel assembly can then be installed in a timepieeeiwhere it will oscillate at the desired rate.

An alternative methcd of describing this testing operation is to consider the electrical equivalent of the mechanical assembly just described. The hair spring, balance wheel and pivot friction at the point 9 may be considered as a closed oscillating system which is coupled to a constant amplitude driving force through the friction of the pivot 9. When the balance wheel system is greatly out of resonance there will be a negligible current or velocity in the tuned circuit representing the balance wheel assembly. As resonance is reached, the amplitude will increase, approaching a maximum and the velocity will, exactly at resonance, go into phase with the driving force. As previously stated, the phase angle of the stroboscopic lamp 28 is adjusted to the positions of maximum velocity of the driving force by the proper relation between

projections

25, 26 and electrical contacts 29. When the balance wheel assembly is in resonance with the frequency of the driving force the flashing lamp will illuminate the wheel at its points of maximum velocity, that is, in the middle of its swing, and the images of the selected spoke of the wheel will be superposed as the wheel reverses its direction.

' Since the above method of adjustmentdepends upon observing the change of phase angle at the position of maximum rate of change the method is very rapid in operation since the only time required is that for a steady rate to be reached.

While the rack and pinion arrangement for oscillating the loose coupling is preferred, it is obvious that various other suitable mechanical devices may be substituted therefor without departing from the scope of the invention.

What is claimed is:

1. Apparatus for adjusting a vibrating system to a desired frequency, comprising means independent of the vibrating system to be adjusted for driving said vibrating system at a constant predetermined frequency, a loose coupling between said vibrating system and said driving means, stroboscopic means for observing the phase angle between said driving means and vibrating system, and means engaging said vibrating. system for adjusting said phase angleto a predetermined value.

2. In a device for adjusting the rate of oscillation of a balance wheel of a timepiece, a synchronous motor, a loose coupling oscillated by said motor, a lamp periodically illuminated by said motor, a balance wheel assembly to be adjusted, means comprising said loose coupling for oscillating the balance wheel assembly, means including said lamp for viewing the phase angle between said oscillating coupling and balance wheel, and means comprising means for adjusting the length of the hairspring of said balance wheel assembly for causing the phases of said elements to correspond.

3. Apparatus for adjusting a vibrating system including means independent of the vibrating system to be adjusted for driving said vibrating system at a desired predetermined frequency, a loose coupling between said vibrating system and said driving means, means for observing the phase relation between said driving means and said vibrating system and means engaging said vibrating system for adjusting said phase angle to a predetermined value.

4. In a device for regulating the rate of oscillation of a vibrating member, driving means independent of the vibrating member and including a loose coupling for oscillating said vibrating member at a predetermined desired rate. stroboscopic means actuated by said driving means for illuminating said vibrating member, and means for adjusting the natural frequency of said member to a value such that its phase corresponds with that of the driving means when viewed by said stroboscopic means.

5. In a device for regulating the rate of oscillation of a vibrating member, driving means independent of the vibrating member and includaisaeuc 3 ing a loose coupling for oscillating said mempair of images which indicate the phase variance bet at a. constant predetermined frequency, between said member and the driving meansand' stroboscopic means actuated by said driving means for adjusting the phase of said member to means for illuminating said vibrating member at bring the images into coincidence thereby indi- 5 the same point during each oscillation in oppocating that the vibrating member and the driv- 5 site direction and at the moment of maximum ina means are in phase. velocity of said member thereby producing a v EDMUND R. MORTON.