Pallets for the escapement of a clock movement

Abstract

The invention relates to pallets for an escapement of a clock movement including a pallet-stone support, pallet-stones mounted on the pallet-stone support, a fork including first and second horns, a safety pin and a rod connecting the pallet-stone support to the fork and to the safety pin, the pallet-stone support, the rod, the safety pin and the fork forming a monolithic body of the pallets, the pallet-stone support, the rod and the safety pin being formed by a main layer of constant thickness, the first and second horns of the fork having a greater height than the constant thickness and being formed by the main layer, and also by an additional layer, the main layer and the additional layer forming the monolithic body of the pallets.

Claims

1. Pallets for an escapement of a clock movement comprising: a pallet-stone support; pallet-stones mounted on the pallet-stone support; a fork including first and second horns; a safety pin; and a rod connecting the pallet-stone support to the fork and to the safety pin, wherein the pallet-stone support, the rod, the safety pin, and the fork form a monolithic body of the pallets, and wherein the pallet-stone support, the rod and the safety pin are formed by a main layer of constant thickness, and in that the first and second horns of the fork have a greater height than the constant thickness and are formed by said main layer, and also by an additional layer, the main layer and the additional layer form the monolithic body of the pallets.

2. The pallets according to claim 1, wherein the ratio between the height of the horns and the thickness of the main layer is between 1.5 and 10.

3. The pallets according to claim 1, wherein the body is manufactured from a material selected from the group of materials comprising silicon, silicon nitride, silicon carbide, steel, gold or one of its alloys, nickel, nickel-phosphorus, brass, copper-beryllium, nickel-silver, polymers, ceramic and amorphous metal.

4. The pallets according to claim 1, wherein the body is produced by a lithographic and electroforming process.

5. The pallets according to claim 4, wherein the process is a process of the LIGA type with two levels.

6. The pallets according to claim 5, wherein the additional layer is formed before the main layer.

7. An escapement of a clock movement comprising the pallets according to claim 1.

8. A clock movement comprising the escapement according to claim 7.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) The invention will be described hereafter in a more detailed manner with the help of the annexed drawings, given by way of example and non-limiting, in which:

(2) FIG. 1a is a perspective view from above of the pallets for an escapement mechanism of the Swiss pallets type, according to one embodiment of the invention;

(3) FIG. 1b is one similar to FIG. 1 a according to a different orientation;

(4) FIG. 1c is a perspective view from below of the pallets; and

(5) FIG. 2 is a sectional view of FIG. 1 a passing along the rod of the pallets.

DETAILED DESCRIPTION OF THE INVENTION

(6) With reference to the figures, pallets 2 for an escapement of the Swiss pallets type for a clock movement comprise a fork 10, a safety pin 12, a support part for the pallet-stones 6, pallet-stones 14 and a rod 8 interconnecting the support part for the pallet-stones 6 to the fork 10 and to the safety pin 12. The rod 8 is coupled in rotation to the plate of a clock movement by means of a pivot 15.

(7) The pallet-stones 14 engage with the teeth of a pallet wheel (not illustrated) of the escapement which is connected to a power source providing a rotational torque on the wheel. One of the pallet-stones constitutes the input pallet-stone and the other constitutes the output pallet-stone, this being as a function of the alternation of rotation of the pallets 2.

(8) The fork 10 comprises a first horn 10a and a second horn 10b provided on both sides of the safety pin 12. The fork engages with a plate pin of a double plate driven onto the axle of a balance wheel (not illustrated) which is intended to regulate the frequency of rotation of the pallet wheel by means of the pallets.

(9) In one direction of rotation of the balance wheel, the first horn 10a acts as input horn and the second horn 10b as output horn. In the other direction of rotation, the functions of the first and second horns are reversed. The safety pin 12 makes it possible to avoid the pallets pivoting and thus the fork passing from the wrong side of the pin when an impact is produced.

(10) The pallet-stone support 6, the rod 8, the safety pin 12 and the fork 10 formed by the first and second horns 10a, 10b form a monolithic body 4.

(11) The pallet-stone support 6, the rod 8, the safety pin 12 are formed by a main layer of constant thickness E. The first and second horns 10a, 10b of the fork have a greater height H than the constant thickness E and are formed by said main layer and by an additional layer, the main layer and the additional layer forming the monolithic body 4 of the pallets 2.

(12) The ratio between the height H of the first and second horns 10a, 10b and the thickness of the rod E of the body is, preferably, between 1.5 and 10.

(13) The first and second horns 10a, 10b of the fork 10 each comprise a bevelled surface 11a, 11b extending over the entirety of the height H of the first and second horns and intended to cooperate with the plate pin of the balance wheel.

(14) The body 4 can be manufactured from various materials including silicon, silicon nitride and silicon carbide, steel, gold or one of its alloys, nickel, nickel-phosphorus, brass, copper-beryllium, nickel-silver, polymers, ceramic and amorphous metal. In the embodiment of the pallets according to FIGS. 1a to 1c, the body 4 of the pallets is manufactured by a LIGA process (lithography, galvanisation and forming) with two levels, which constitutes an economical and precise manufacturing method for small-size parts. The LIGA process for superimposing two layers of pallets with several levels is in fact described in document CH704086.

(15) The first level, produced firstly via this method, is the additional layer of the body 4 which is composed of the portion of the first and second horns 10a, 10b which extend over the height H-E. The second level, produced secondly via this process, is the main layer of the body 4, composed of the other portion of the horns 10a, 10b of the fork 10, of the rod 8, of the safety pin 12 and of the pallet-stone support 6. Thus firstly the additional layer is formed then the main layer is formed on the additional layer in order to obtain the body 4 of the pallets 2 according to the invention.

(16) The invention therefore makes it possible to reduce the manufacturing costs and to increase the production yields of the pallets whilst avoiding imprecisions in the positioning of the safety pin relative to the horns, in particular in the division heights of the safety pin and of the horns.

REFERENCE NUMBER LIST

(17) Escapement pallets 2 body 4 pallet-stone support 6 rod 8 fork 10 first horn 10a bevelled surface 11a second horn 10b bevelled surface 11b safety pin 12 pallet-stones 14 input pallet-stone output pallet-stone pivot 15