US228995A - Attachment of hair-springs to balance-staffs - Google Patents

Description

(No Model.)

J. M. HEARD. Attachment of Hair Springs to Balance Staff.

No. 228,995. Patented June 22,1880.

mmxma Masses.

' UNITED STATES PATENT OFFICE.

JAMES M. HEARD, OF ST. PAUL, MINNESOTA.

ATTACHMENT OF HAIR-SPRINGS TO BALANCE-STAFFS.

SPECIFICATION forming part of Letters Patent No. 228,995, dated June 22, 1880.

Application filed April 5, 1880. (No model.)

To all whom it may concern:

Be it known that I, JAMES MIL'roN HEARD, of St. Paul, in the county of Ramsey and State of Minnesota, have invented a new and useful Improvement in the Method of Attaching the Hair-Springs to the Staffs in Watches, &c., of which the following is a specification.

This invention relates to the hair-sprin gs of watches, 850.; and it consists in so securing the inner end of the spring to the staff that the point of commencement of the vibration will occur at a point at or between the center and periphery of the staff, whereby all parts of the outer coil will be isochronal, as hereinafter set forth.

I attain these results by the mechanism i1- lustrated in the accompanying drawings, in which Figure l is a plan view, and Fig. 2 is a sectional side elevation, of a com pensatin gwheel, hair-spring, and staff of a watch enlarged five diameters, showing the method of applying my invention. Fig. 3 is a cross-section, and Fig. 4 a side elevation, of a portion of the staff and hair-spring enlarged fifteen times, showing my manner of securing the spring to the staff; Figs. 5 and 6, similar views, illust 'ating the ordinary method of securing the spring.

A is the compensating-wheel, B the staff, and O the hair-spring, all made in the usual manner.

In the ordinary method of securing the spring to the staff its inner end is passed through a hole through the side of a collet, a, (see Figs. 5 and 6,) on the staff and fastened therein by a wedge, I), while the outer end is secured to the under side of the cock at its isochronal point. In this method the isochronal point ordinarily occurs on the outer coil at or near the part c, Fig. 1, but not always so, as this point is very uncertain by reason of the varying thickness, length, and temper of the springs. Great care, nicety of adjustment, and experiment are necessary to determine its exact location.

If the spring were so attached to the staff that the exact center of the coil would be in the exact center of the staff, all points on the outer coil would be isochronal, and this advantage I obtain by securing the sprin 0 directly to the staff B by passing its inner end through a hole, (I, drilled through the staff, and fastening it" therein by a wedge, c. This brings the point 1 of the commencement of the vibration of the spring very near the center of the staff, while in the ordinary manner of fastening itby the collct this point occurs at the periphery of the latter, as shown in Figs. 5 and 6.

By my arrangement the center of the coil will be brought so near the center of the staff that all parts of the outer coil will be approximately isochronal; but by countersinking the side of the hole (1 next the vibration-point 9 this vibration-point will be brought back exactly to the center, so that all parts of the outer coil will be rendered still nearer isochronal, or at least near enough for all practical purposes, this isochronism being a matter of such delicate adjustment that it is next to an utter impossibility to perfectly attain it; but by my arrangement of the vibration-point exactly in the center of the staff I claim that, other things being equal, all watches may be made practically isochronous. This is a very important improvement, as by the old method it is a matter of great difficulty and expense to find the isochronal point of the spring; but by my arrangement all parts of the outer coil are isochronal; hence perfect time is insured.

What I claim as new is A watch balance-staff having a hole through the center of its upper part at right angles to its axial line, in which the inner end of the hair-spring is secured, whereby the point of commencement of the vibration of the spring occurs at apoint at the center of the staff, or at a point between the center and periphery,

substantially as set forth.

In testimony whereof I have hereunto set my hand in the presence of two subscribing witnesses.

JAMES MILTON HEARD.

Witnesses S. S. WOLCOTT, G. N. WOODWARD.

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