US2648188A

US2648188A - Watch balance and staff

Info

Publication number: US2648188A
Application number: US94104A
Authority: US
Inventors: Leo W Muffley
Original assignee: CHESTER L DAVIS
Current assignee: CHESTER L DAVIS
Priority date: 1949-05-19
Filing date: 1949-05-19
Publication date: 1953-08-11
Anticipated expiration: 1970-08-11

Description

Aug. 11, 1953 y L. WIMUFFLEY 2,648, 8

WATCH BALANCE AND STAFF 7 Filed May 19, 194's r 2-SheetsSheet 1 INVENTOR.

ATTORNEY g-" ,1953 w. 'MUFFLEY WATCH BALANCE AND STAFF Filed May 19 1949 2 Sheets-Sheet 2 Fig 6 INVENTOR.

1411; AL ATTORNEY Patented Aug. 11, 1953 WATCH BALANCE AND STAFF Leo W. Muffley, Palmyra, M0., assignor of onethird to Chester L. Davis, Perry, Mo.

Application May 19, 1949, Serial No. 94,104

My invention relates to a new and improved watch balance and staff and more especially to structure such as when embodied in a watch will be practically safe under most conditions of shock.

An object of my invention is to provide a new and improved construction of the balance wheel and staff enabling the same to move axially with respect to each other.

Another object of my invention is to provide a construction of the balance Wheel and its associ ated staff so that they are free to move axially with respect to each other while at the same time not permitted to rotate independenly.

1 Still a further object of my invention is to provide a modification of the conventional balance wheel and staff of an existing watch to embody my invention thereby reducing the further servicing of the watch.

Other and further objects of my invention will appear from the specification to follow and from examination of the drawings, in whichf Fig. 1 shows a side view in section of a conventional balance wheel and staff assembly such as would be found in most watches in present use,

Fig. 2 is a view of the conventional staff without my improvement,

Fig. 3 shows the general shape of an improved staff such as might be constructed in accordance with my invention,

Fig. 4 shows the general shape of a staff in section such as might be employed in-the practice of repairing an existing watch in accordance with my invention,

Fig. 5 is a sectional view of a complete assembly of balance wheel and staff according to one form of my invention,

Fig. 6 shows a perspective view of the spring member employed to support the balance wheel,

Fig. '7 shows a plan view of the spring member employed to support the balance wheel,

Fig. 8 is a plan view of a balance Wheel modified in accordance with my invention,

Fig. 9 is a side view in section of an arm of the balance wheel showin its position relative to the staff when the Watch is not under a condition of shock, and

Fig. 10 is a side view in section of an arm of the balance wheel showing its position relative to the staff when the watch is under a condition of shock.

It has long been known that watches are damaged most frequently by dropping or striking them against another object, this usually result- 3 Claims. (Cl. 58-407) ing in breaking the jewels or bending or breaking the pivots or a combination of both. This is due to the fact that the balance wheel of a watch is relatively heavy, the pivots on the ends of the balance staff are relatively small in diameter to minimize friction in the jewel bearings in which they rest. The heavy balance wheel attempts to follow the impact and in the usual type of construction, the balance wheel being riveted firmly to the staff, this force is concentrated on the pivots and jewels. I realize that I am not the first to recognize this problem and I am aware that there have been many prior attempts to provide a satisfactory solution. One of the methods heretofore employed is to make use of an elongated and spiral shaped arm serving as a spring support for the wheel upon the staff. The difficulty of such an arrangement is that if the spiral spring arm is of sufficient strength to adequately support the balance wheel under normal operating conditions, the spring is too strong to afford any degree of satisfactory shock-absorbing, unless as is usually the case, a compromise is effected and the pivots on the staff are enlarged in diameter thereby increasing friction. In my construction the balance Wheel normally rests against the staff in a positive and accurate poise and remains so under all normal conditions, thereby insuring proper motion of the balance wheel and accurate time keeping of the watch. The spring suspension that I employ does not at any time become effective unless and until and only during such time that the watch is actually undergoing a condition of shock. Its normal function is to keep the balance wheel against a leveling flange and to prevent independent rotation of the balance Wheel and the staff.

Fig. 1 shows a sectional view of a conventional balance wheel with its associated staff. The rim 1 is supported by the arm 6 and is rigidly connected, usually by riveting, to the staff l immediately above a leveling table or enlarged hub 2. Staff I is tapered on the ends forming pivots Ia and lb. The roller table 8 is usually secured to the staff I by means of a close or driven fit.

Fig. 2 is a diagrammatic view of a typical staff I, such as is shown in Fig. 1, previously referred to, like reference characters relating to like parts throughout all the drawings.

Fig. 3 shows a completed staff I, having pivots la and lb on the extreme ends thereof, the leveling table 2 being now merely a thin disc-shaped enlargement of the staff and having the appearance of a Washer. The rather thick leveling U table shown in Figs. 1 and 2 has also been turned down to produce the wafer-shaped leveling table 2 immediately above a cup-shaped section 2a beneath which is a neck portion 20 below which is a flange 2d adapted to be a stop for the roller table 8 shown elsewhere.

Fig. 4 shows a staff I which has been turned down considerably in its central portion and a washer driven on near the same position that would normally be the arm of the balance wheel and could be secured by riveting in the same manner as the balance wheel is normally secured to the staff.

Fig. 5 shows a complete assembly of a balance wheel and staff, the rim 1 and the arm 6 being, shown in section. As will be observed, the arm 6 has a hole centrally located, the arm 6 with the hole 6a being shown better in Fig. 8. The portion of the arm 6 immediately around the hole,

Ba constitutes the bearing surface of the balance wheel. This bearing surface of the arm 6 normally rests against the lower side of leveling table 2 and is held in contact therewith by the tension of spring 9. This spring 9 is shown more particularly in Figs. 6 and 7 as being of the elongated flat type having tapered ends 9a and a centrally located hole 9b. The ends 9a of the spring 9 are shown as curled upward.

Fig. 8 is a plan view of the balance wheel having a rim 1, an arm 6 with a hole 6a centrally located. Grooves or slotted sections H are provided equi-distant from the rim 1, in which the ends 9a of the spring 9 always rest.

Fig. 9 is a partial view in section of the balance arm 6 and the staff. Attention is called to the recessing .or countersinking of the arm 6 at the central hole, which may or may not be necessary depending upon the spacing afforded in the construction of the watch initially and is not necessary except in modifying an existing watch. It is important however to have the bearing surface between the leveling table 2 and the arm 6 to cover an appreciable area and at the same time to have the bearing surfaces between the central portion 61) of arm ,6 and the cup-shaped section 2a reduced as small as possible. It will be seen that the central portion 6b has therefore been countersunk or bevelled as an inclined plane surface and making contact with the cupshaped section 2a only at the lower part of the cylindrical section thereof. Once this relationship is understood I again refer to Fig. 5. The spring 9 is secured to the staff I and prevented from turning with respect to the staif I usually by a tight fit on the staff I and held in place by the roller table 8.

Fig. 10 shows thearm 5 in section displaced with respect to staff I as it would momentarily appear under shock. It will be observed that one side of the periphery of the hole, to the left of the staff I, is displaced downward along the axis of staff I and is clear therefrom. The other side of the periphery of the hole has also traveled downward the portion 6b of the arm 6 being below the cylindrical section of cup shaped portion 2a. In visualizing the relative position of thearm B with respect to cup-shaped portion 2a, from a condition of rest to one of momentarily displacement, it will be apparent that the inclined plane surface of the central section 6b has only one point of contact with cup-shaped section 2a throughout its travel downward. As the section 61: passes upward it bears against the.

junction between the cylindrical, section of 2a andthe convex portion of 2a. That is why, I refer to the convex portion and the cylindrical portion together as being a cup-shaped section 2a, the convex portion may be considered as a centering cone the base of which functioning as the final centering and the cylindrical portion above largely serving as a cut-away section to minimize friction. From Fig. 9 it will be observed that there is an open triangular area between the junction of leveling table 2 where it joins the cup shaped section 2a and portion 6b of the arm 6. Had the convex portion continued to be convex rather than change to cylindrical in shape it might very well serve as a centering cone but it might not serve as a leveling device as well. Since I depend upon the leveling table 2 for this function it is apparent that should one have the convex section continue to the leveling table 2, such section would prevent the functioning of the leveling table 2 unless the machining of the parts was executed to a precision nearly impossible of attainment.

It is also likely that any small dust particles on such a continued convex surface would interfere with the upward travel of the arm and prevent it from reaching the leveling table 2. In the arrangement that I employ, such dust particles and foreign matter as most certainly will accumulate on the cup-shaped section 2a, is carried into the open triangular area referred to. Of course if the seating of arm 6 against leveling table 2 is not correct, such as might be caused by accumulation of foreign matter between them, the balance wheel I would not be axially aligned on the staff I, resulting in erratic and inaccurate beat of the watch. Should the accumulation of dirt not be a serious matter the convex section could continue to the leveling table and friction between the same and the arm 6 would, in this case, be reduced by not having the sections 6b of the arm 6 to take the same shape as the convex section, in other words the hole in arm 6 would not be countersunk.

It should be understood that the drawings are not intended to be to accurate scale and the proportion of the various parts is not necessarily that which would be followed in practice. There are many different watch movements in use today and my invention may be applied to any of them by suitable modification as to size, shape and location of the staif, balance wheel, roller table and h-airspring collet. Much of the construction illustrated in the drawings has appeared necessary in order to embody my invention in an existing watch.

It will be observed that the arrangement I employ is particularly effective when the impact or shock is transmitted toward the lower pivot, when, as mentioned, the heavy balance wheel attempts to follow the direction of travel. It is likewise very effective when the motion is transmitted at ri ht angles to the staff I. At any angle, whether greater or less than that, the rim 6 of the balance wheel I attempt to carry the poised and heavy rim in the direction of travel and accordingly would leave its normal position against the leveling table 2. The entire rim of the balance wheel 1 would be axially aligned on the staff I during an actual shock condition, only when the motion is in exactly the same direction as the alignment of the pivots on the staff I. Should such a directional impact possibly take place, the heavy rim of the balance wheel 1 would leave its seating against leveling table 2 when the motionis in the direction of the upper pivot, the

spring 8, flexing to delay th seating until.

after the impact. When the motion is in the direction of the lower pivot the arm of the heavy balance wheel I does not and can not leave the leveling table 2 until the motion is arrested, when as previously mentioned, the mass of the wheel continues to follow in the direction of travel. It will thus be seen that for all practical purposes the shock-absorbing arrangement is at all times effective regardless of the direction of transmitted shock. Constructions reversing the position of the cup-shaped member 2a above the leveling table 2 are within the scope of my invention and when so arranged the spring 9 would be held in place by the hair-spring collet in a similar manner to the manner of its being held in position by means of roller table 8 as I have illustrated. It is important to my invention that the balance wheel I be held against a leveling shoulder 2 on a st-aiT I under normal operating conditions and prevented from rotating or twisting independently of the staif I under shock conditions. It is of course possible for the balance wheel I to rotate independently of the staff I when the balance Wheel I is in perfect poise without using a fixed locating spring such as my spring 9, and this would not cause any great difficulty, however under normal operating conditions when the watch is not under a condition of shock the balance wheel I must not rotate independently from the rotation of the staff I. It is for this reason that I use the straight spring 9 rather than a helical spring since the latter would permit separate rotation under merely normal operating conditions.

I realize that many modifications of my invention are possible without departing from the spirit of my invention and without departing from the scope of the following claims.

I claim:

1. An improved balance wheel and stafi assembly comprising in combination a staff having end pivots, a leveling shoulder on said staff intermediate said pivots, a spring intermediat one of said pivots and said shoulder, said balance wheel having an arm With a centrally located aperture therein, elongated grooves in said arm disposed on opposite sides of the axis of said staff,

said staff passing through the aperture of said arm, said arm held against said leveling shoulder under normal conditions by means of said spring and free to move from said shoulder under conditions of mechanical shock and said spring seating in said grooves in said arm to prevent independent rotations of said balance wheel and said staff.

2. An improved balance wheel and staff assembly comprising in combination a staff, a leveling shoulder on said staff, a balance wheel having an arm in which is an opening for freely receiving said stafi whereby said balance wheel is free to move axially along said staff under conditions of shock and otherwise normally seated against said leveling shoulder, a spring, the central portion of which is fastened to said staiT, the ends of said spring bearing against said arm and normally forcing the same against said leveling shoulder and means locking said spring to said arm against independent rotation.

3. A balance wheel and staff assembly comprising in combination a staff, a balance wheel having an arm, said arm having grooves on the under side thereof disposed on opposite sides of the axis of said stafi and of lesser width than the width of said arm, said staff having a shoulder, said arm having a central opening for freely receiving said staff and of lesser diameter than said shoulder, a spring having a central portion secured to said staff, said spring having upturned ends bearing in and seated in said grooves and normally forcing said arm against the shoulder on said staff.

LEO W. MUFFLEY.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 380,769 Rohde Apr, 10, 1888 1,951,995 Schaad Mar. 20, 1934 FOREIGN PATENTS Number Country Date 167,848 Switzerland June 1, 1934