Patent Publication Number: US-4055944-A

Title: Securing device for the outer end of the hair-spring of a timepiece

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a securing device for the outer end of the hair-spring of the balance wheel of a timepiece. 
     It is admitted that gluing the outer end of a hair-spring for a timepiece provides some advantages, especially in the rapidity of the operation of securing the hair-spring in mass production, in the absence of deformation of the hair-spring and in the risk of damage thereto. 
     However, gluing hair-springs also has some drawbacks, more particularly in repairing them, due to the fact that the people who do this work are not usually provided with the material or equipment needed for this operation. 
     The object of the present invention is to furnish means permitting the manufacturer to glue the hair-spring and, consequently, to take advantage of this method of securing, especially where mass production is concerned, but which also allows the hair-spring to be secured in another way, namely by means of a pin, thereby overcoming the drawback mentioned hereinabove concerning the repairing, the person doing the repair thus having at his disposal another securing means for the hair-spring. 
     SUMMARY OF THE INVENTION 
     The invention resides in providing a securing device for the outer end of the hair-spring in a watch or other timepiece with a U-shaped arm which extends radially of the axis of the balance wheel. Two thin-walled ears formed by the parallel legs of the U-shaped arm are disposed parallel to the axis of the balance wheel at a predetermined angle to the radial plane extending through the middle of the arm. One of the ears is provided with an opening, such as a notch, for gluing the outer end of the hair-spring, while the other ear has a second opening, such as a circular hole, to receive and fix the end off the hair-spring by means of a pin when it is not glued in the first opening. The ear for pinning is situated on a radial plane through the axis of the balance wheel such that the plane of the second opening is perpendicular to the tangent to the hair-spring at the point where it is pinned. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
     The drawing shows, by way of example, one embodiment of the invention. 
     FIG. 1 is an axial sectional view of a portion of a regulating device for a timepiece, including the balance wheel and hair-spring; 
     FIG. 2 is an elevational view of a detail of FIG. 1 as viewed from the diametrically opposite side thereof as viewed in FIG. 1; 
     FIG. 3 is a plan view, from underneath, of the hair-spring carrier; 
     FIG. 4 is a sectional view of this detail, along line IV--IV of FIG. 3; and 
     FIG. 5 is a plan view, also from underneath, of this same detail, during the manufacture. 
    
    
     The regulating device partially represented comprises a balance wheel 1 carried by a shaft 2 rotatably mounted between two bearings, only the upper one 3 of which has been represented. The support for bearing 3, which is forced into the cock 4, constitutes a cock-endstone around which is rotatably mounted a hair-spring carrier 5 on which is superimposed a regulator 6. This regulator is constituted by a thin sheet having a portion 6a bent at right angles to provide a slot 7, intended to receive a hair-spring 8, this portion 6a thus replacing the usual adjusting pins. The outer end of the hair-spring is secured to the hair-spring carrier 5, which to this end is provided with a thin arm 5a having two parallel ears 5b and 5c, bent at right angles thereto and forming an angle of 15° with the radical plane, designated by 9, passing through the middle portion of the arm 5a. 
     An opening or notch 10 is provided in the ear 5b (FIG. 1) for receiving the hair-spring which in this instance is glued thereto by means of a portion of thermoplastic material which is melted by means of a suitable apparatus comprising, generally, heating means operated by electro-resistance and which melts the piece of thermoplastic material in the notch 10. 
     A second opening 11, which may be example be a circular hole, is provided in ear 5c in order to receive the end of hair-spring 8 when it is not to be glued in the notch 10. In that event hair-spring 8 is pinned in hole 11 in the usual manner. It will be noted, however, that in order to ensure proper centering of the hair-spring, it is necessary that the plane of hole 11 be perpendicular to the tangent to the hair-spring at the point where it is fixed to ear 5c. As will be seen in FIG. 3, ear 5c is disposed in a radial plane 12 through the axis of rotation of the carrier and, therefore, of the hair-spring 8. Consequently, due to the fact that both ears 5b and 5c form an angle of 15° to the radial plane 9, the arm 5a of the hair-spring carrier can be rotated slightly about the cock-endstone 3 in order to reset the mark of the balance wheel when the change is made for gluing the balance wheel to pinning it. This arrangement permits the means for securing the end of the hair-spring to be readily changed without deforming or damaging it. 
     With the present arrangement, the manufacturer can take advantage of the gluing method of securing the hair-spring, while on the other hand the watch-repairman, who is not equipped to glue hairsprings, can secure the hair-spring by means of a pin. 
     In the example as represented, the hair-spring is secured to a carrier which can be very easily made by a stamping operation giving it the form represented in FIG. 5, and then by bending the ears at right angles to the plane of the carrier arm into parallel relation to each other. 
     However, the invention is not restricted to the case where a hair-spring carrier is employed. For example, two ears can be provided directly on the cock, one with a notch 10 for gluing the hair-spring, the other with a hole 11 for pinning it.