US2864232A - Balance roller for lever escapement of a timepiece - Google Patents

Description

Dec. 16, 1958 P. TUETEY 2,864,232

BALANCE ROLLER FOR LEVER ESCAPEMENT OF A TIMEPIECE Filed Dec. 29, 1955 4 Sheets-Sheet 1 PRtOR ART INVENTOR Paul Tuareg ATTORNEY Dec. 16, 1958 P. TUETEY 2,864,232

BALANCE ROLLER FOR LEVER ESCAPEMENT OF A TIMEPIECE- Filed Dec. 29, 1955 v 4 Sheets-Sheet 2 INVENTOR ATTO R N EY Dec. 16, 1958 P. TUETEY 2,864,232

BALANCE ROLLER FOR LEVER ESCAPEMENT OF A TIMEPIECE Filed Dec. 29, 1955 4 Sheets-Sheet 5 Paul Tuer mm ATTORN EY Dec. 16, 1958 P. TUETEY 2,864,232

BALANCE ROLLER FOR LEVER ESCAPEMENT OF A TIMEPIECE.

Filed Dec. 29, 1955 4 Sheets-Sheet 4 H613 r p -15 Y 1w a INVENTOR. Paul Tuereg United States Patent BALANCE ROLLER FOR LEVER ESCAPEMENT OF A TIMEPIECE Paul Tuetey, Le Locle, Switzerland, assignor to Les Fabriques dAssortiments Runies, Le Locle, Switzerland Application December 29, 1955, Serial N 0. 556,241 Claims priority, application Switzerland February 25, 1955 9 Claims. (Cl. 58121) The present invention relates to a lever escapement of timepieces and more particularly to a balance roller for lever escapement and to a process of manufacture of same.

Up to now the impulse pin or roller jewel adapted to cooperate with the pallet fork or lever was driven in or maintained by means of gum-lac in a bore stamped out in the roller.

Fixing a pin by driving it into a suitable bore of the roller necessitates a very high precision of these elements. The impulse pinshould have bevelled edges so as to penetrate more easily into the bore and to avoid and additional stamping out of said bore. On the other hand, according to the material used for making the impulse pin (synthetic jewels), which is more or less fragile, there often occur grinding or breaking of the pin, resulting in the loss of the roller since it is practically impossible to replace a broken pin.

Securing the impulse pin by means of gum-lac necessitates a bore in the roller, the dimensions of which are somewhat larger than those of the pin. The latter may, therefore, assume different positions and the most frequent drawback is the lack of perpendicularity of the pin axis with respect to the plane of the roller. In addition, the gum-lac runs over on the roller and at the moment of assembling the roll onto the balance staff, it comes sometimes into contact with a flange of said staff, resulting in breaking the gum-lac and causing the pin to fall. Finally, the gum-lac is often dissolved by the liquids used for cleaning the balances.

The invention aims at overcoming the above-mentioned drawbacks. To this end, the balance roller carrying an impulse pin comprises a central disc having a non-circular recess receiving the pin, said pin being secured in its position by means of a ring bearing both on the pin and on the periphery of the disc.

The balance roller is generally rigidly fixed to a small roller adapted to cooperate with the guard pin or dart of the pallet fork or lever. Up to now, the bore of the large roller adapted to receive the impulse pin and the notch of the small roller had to be executed separately with the risks of imprecision involved therewith. As a matter of fact, the radial alignment of the pin bore and of the notch was not guaranteed, so that the safety functions of the escapement were not made correctly.

, 2,864,232 Patented Dec. 16, 19 53 Fig. 3 is an elevation view of the lever escapement shown in Fig. 2.

Fig. 4 is a perspective exploded view of the same embodiment at an enlarged scale.

Fig. 5 is a perspective view corresponding to Fig. 4, but in which the parts of the roller are assembled to one another.

Figs. 6 to 11 are bottom views of six other embodiments, at a reduced scale.

Figs. 12 and 13 are cross-sectional views of two modified structures.

Referring to Fig. 1, it will be seen the end portion of a lever or pallet fork 1 and a double balance roller 2, 3 of a lever escapement of a known construction. The limiting pins of the lever 1 are denoted by the numerals 4, the impulse pin or roller jewel by 5, the notch of the small roller by 6, the horns of the lever by 7, the guard pin or dart by 8, the balance staff by 9 and the roller can non by 10.

The construction illustrated in Figs. 2 and 3 difiers from that of Fig. 1 especially in the manner in which the impulse pin 5 is secured to the large roller and in the greater radius of the small roller.

The large roller comprises a central disc 11 having a non-circular recess 12 obtained for instance by a milling operation. The recess 12 is machined in such a way that the pin 5, when put into position, slightly lies outside the circumference of the disc 11. As usually, the pin 5 has an approximately semicylindrical shape and it is its plane face which closes the open side of the recess 12. A ring 13, which is driven onto the disc 11, holds the pin 5 in position. w

This assembling system of the impulse pin and ofthe large roller permits machining simultaneously the recess 12 and the notch 14 of the small roller '15. This machining is made in a single operation and with the same tool, preferably by milling. Thus, the notch 14 of the small roller has the same shape as a portion of the recess 12 of the large roller and is situated in the axial prolongation of thisportion. The risks ofimpr'ecisio'n mentioned above are therefore done away with, as the radial alignment of the place receiving the pin and of the notch of the small roller is now guaranteed. The safety functions of the escapement are made correctly; any subsequent checking is superfluous and an important cause of refuse in the manufacture is removed.

Another advantage of the described construction consists in the possibility of giving to the roller cannon a larger radius, so that the radius of the roller hole 19, whose machining is always difiicult, can be increased or else the strength of the roller can be reinforced by in- The invention also permits overcoming this difiiculty as it relates in addition to a process of manufacture of the double roller (large roller and small roller), in which the recess of the large roller adapted to receive the impulse pin and the notch of the small roller are machined Fig. 1 shows for comparison purposes a bottom view of a portion of a lever escapement of a known construction.

Fig. 2 is a view corresponding to Fig. 1 of the first embodiment of the invention and of the lever co-operating therewith.

creasing the thickness of the cannon wall. As a matter of fact, it will be seen in Fig. 1 that the'ends of the horns 7 do not permit giving to the cannon 10 'a radius r guaran teeing' a sufficiently thick Wall. On the contrary, in the escapement shown in Fig, 2, the ends of the horns 16 have been appreciably shortened, so that the radius r of the cannon 17 can be made somewhat greater. It was possible to shorten the horns 16 owning to the increase of the radius R of the small roller 3 .(Fig. 1), which becomes R for the small roller 15 of Fig. 2, and owing to the decrease of the angular width of the notch of' the smallroller, which passes from the value a (Fig. 1 to the value a, (Fig. 2).

At firstsight, it might seem that the possibility of increasing the radius of the roller cannon does not depend on the invention. In reality, the radius of the cannon only depends on 'the'length of the horns 7 or 16 respectively ofthe lever 1. This length in turn is conditioned .by the necessity of avoiding any overbanking of the lever 1 between the moment when thedar't- 8 or- '18 respectively is no longer in contact with the small roller 3 or '15 respectively (Within the range of the notch) and the moment when the pin 5 enters the opening of the lever. This lapse of time is the shorter as the radius of the small roller is greater or the dart is wider. In the construction illustrated in Fig. 2, machining of the notch 14 of the small roller 15 with the same tool as for the recess 12 makes it necessary to shorten the dart 18 and therefore to increase the radius of the small roller .15. It results naturally therefrom that, since the length of the horns 16 may be reduced, the radius of the cannon 17 may be increased.

The shape of the recess 12 and of the notch 14, instead of being semicylindrical as in Figs. 2 to 5, may be modified in order to facilitatethe machining by means of milling tools having a profile easy to draw up. Thus, in the embodiments shown in Figs. .6 and 9 to 11, the recess 12a and the notch14a have a rectangular cross-section, Whereas in the embodiment of Fig. 7 they have the shapeof a slightly obtuse dihedral angle and are denoted by 12b and 14b, respectively. In the example of Fig. 8 the cross-section of the recess 12c and of the notch 140 is trapezoidal.

It is not indispensable that the ring 13 be driven onto the disc 11. Its putting in place might be done by means of a preliminary elastic deformation which would be rendered possible by a suitable shape of the disc 11 which would have only a limited number .of points of contact with the ring 13, as illustrated in Figs. 8 and 9 in which the discs are denoted by 110 and 11a, respectively.

It is also not necessary that the impulse pin 5 lie partially outside the circumference of the disc 11. It is possible to hold it in position also in such a case. Figs. 10 and 11 show two constructions with this feature, the rings being denoted by.13a and 13b, respectively.

The large roller and the small roller are generally made integral with each other. However, the two-piece construction was also executed previously and in certain cases the small roller was made integral with the balance staff. Up to now nobody has succeeded in making the double roller integral with the balance staff, as it was necessary to stamp out in the large roller the bore adapted to receive the impulse pin. On the contrary, owing to the above-mentioned machining of the open recess 12, it is now possible to make in one piece the disc 11, the small roller 15 and the balance staff 9 (Fig. 13). In a modified structure, the disc 11 is made integral only with the balance staff 9, whereas the small roller 15 is held by a drive fit on the balance statf 9 (Fig. 12).

While the invention has been described and illustrated with reference to specific embodiments thereof, it will be understood that other embodiments may be resorted to without departing from the invention. Therefore, the form of the invention set out above should be considered as illustrative and not as limiting the scope of the follow? ing claims.

I claim:

1. A balance-roller for lever escapement of a timepiece, carrying an impulse pin adapted to cooperate with the lever, the roller comprising a central disc of uniform thickness having at its periphery a non-circular recess, open towards the outside and rec-eiving the impulse pin, and an outer ring surrounding the central disc and hearing both on the pin and on the periphery of the disc so as to press the pin against the wall of the recess and thus secure the pin in its position.

2. A :balance roller for lever escapement of a timepiece, carrying an impulse pin adapted to cooperate with the lever, the roller comprising a central disc of uniform thickness having at its periphery a non-circular recess, open towards the outside and receiving the impulse pin, the pin lying partially outside the circumference of the disc, and an outer ring surrounding the central disc and bearing both on the pin and on the periphery of the disc so as to press the pin against the wall of the recess and thus secure the pin in its position.

3. A balance roller for lever escapement of a timepiece, carrying an impulse pin adapted to cooperate with the lever, the roller comprising a central disc of uniform thickness having at its periphery a semicylindrical recess open towards the outside and receiving the impulse pin, and an outer ring surrounding the central disc and bearing both on the pin and on the periphery of the disc so as to press the pin against the wall of the recess and thus secure the pin in its position.

4. A balance roller for lever escapement of a timepiece, carrying an impulse pin adapted to cooperate with the lever, the roller comprising a central disc having a non-circular recess receiving the impulse pin, and an outer ring surrounding the central disc and bearing both on the pin and on the periphery of the disc so as to press the pin against the Wall of the recess and thus secure the pin in its position, the ring being held by a drive fit.

5. A balance roller for lever escapement of a timepiece, carrying an impulse pin adapted to cooperate with the lever, the roller comprising a central disc having a. non-circular recess receiving the impulse pin, and an outer ring surrounding the central disc and bearing both on the pin and on the periphery of the disc so as to press the pin against the wall of the recess and thus secure the pin in its position, the ring being held in position by elastic deformation.

6. A balance roller for lever escapement of a timepiece, carrying an impulse pin adapted to cooperate with the lever, the roller comprising a central disc having a non-circular recess receiving the impulse pin, and an outer ring surrounding the central disc and bearing both on the pin and on the periphery of the disc so as to press the pin against the wall of the recess and thus secure the pin in its position, the impulse pin being placed within the circumference of the disc.

7. A balance roller for lever escapement of a timepiece, carrying an impulse pin adapted to cooperate with the lever, the roller comprising a central disc having a non-circular recess receiving the impulse pin, and an outer ring surrounding the central disc and bearing both on the pin and on the periphery of the disc so as to press the pin against the wall of the recess and thus secure the pin in its position, the disc being made integral with the balance staff.

8. A balance roller assembly for lever escapement having a lever with a guard pin of a timepiece, carrying an impulse pin adapted to cooperate with the lever, the roller assembly comprising a central disc having a noncircular recess receiving the impulse pin, and an outer ring surrounding the central disc and bearing both on the pin and on the periphery of the disc so as to press the pin against the wall of the recess and thus secure the pin in its position, a small roller, the disc being rigidly fixed to the small roller which is adapted to cooperate with the guard pin of the lever, the central disc and the small roller being made integral with the balance staff.

9. A balance roller assembly for lever escapement having a lever with a guard pin of a timepiece, carrying an impulse pin adapted to cooperate with the lever, the roller assembly comprising a central disc having a noncircular recess receiving the impulse pin, and an outer ring surrounding the central disc and bearing both on the pin and on the periphery of the disc so as to press the pin against the wall of the recess and thus secure the pin in its position, a small roller, the disc being rigidly fixed to the small roller which is adapted to cooperate with the guard pin of the lever, the notch of the small roller having the same shape as a portion of the recess of the disc and being situated in the axial prolongation of said portion.

References Cited in the file of this patent UNITED STATES PATENTS

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