US 3621650 A
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23, 1971 E. SCHNYDER ETAL 3,621,650
BARREL FOR A SELF-WINDING TIMEPIECE 1 Filed Jan. 22, 1969 INVENTORS EDUARD SCHNYDER CHRISTOPH BIERI ATTORNEYS United States Patent 3,621,650 BARREL FOR A SELF-WINDIN G TIMEPIECE Eduard Schnyder and Christoph Bieri, Bienne, Switzerland, assignors to Omega Louis Brandt & Frere S.A., Canton, Bern, Switzerland Filed Jan. 22, 1969, Ser. No. 792,963 Claims priority, application Switzerland, Jan. 26, 1968, 1,272/68 Int. Cl. G04]; 1/18 US. Cl. 58-87 7 Claims ABSTRACT OF THE DISCLOSURE A main spring barrel for a timepiece, particularly a selfwinding timepiece, has an inner cylindrical wall to be frictionally engaged by the main spring or a slip spring as sociated therewith to enable slipping of the main spring relative to the barrel when the main spring is sufficiently wound. The inner surface of the barrel has a hardness substantially equal to that of the main spring or the slip spring and has self-lubricating characteristics. The inner barrel wall or surface is provided with a relatively wide, shallow depression that extends outwardly beyond the cylindrical surface of the inner wall, and constitutes a deterrent to relative movement between the main spring or its slip spring and the inner barrel surface by providing gradually sloping or inclined areas over which the end of the spring, either main or slip spring, must pass.
BACKGROUND OF THE INVENTION The main spring or a slip spring associated therewith is provided with an outwardly extending tang portion that frictionally engages the inner cylindrical surface of the main spring barrel to retard slip between the spring or springs and the barrel. This includes wear, not only of the springs so as to affect the efiiciency of the main spring, but also causes malfunction of the timepiece because of the main springs gradual change in tension. To offset this situation, it previously has been suggested to provide notches in the inner barrel surface which serve to retard the slipping of the tang on the spring as well as to provide an audible sound to indicate when the spring has become sufficiently wound.
It has been observed that, in such barrels, the outer coil of the main spring pressed against the Wall of the barrel attacks this wall, in spite of a good lubrication, thus impairing the operation of the friction coupling and affecting the working of the timepiece.
SUMMARY OF THE INVENTION According to the present invention, the inner wall of the barrel is generally cylindrical, but has at least one relatively wide, shallow depression extending outwardly of the inner wall surface to provide gradually sloping or inclined areas adjacent the cylindrical wall areas which serve to gradually inhibit slipping of the tang on the main spring or slip spring but do not induce an abrupt stopping or frictional reaction between the spring and the barrel wall. The inner barrel wall constitutes a surface of a hardness substantially equal to that of the spring and conveniently may comprise an insert of a harder material than that of which the barrel normally is made. Preferably, the shallow depression is provided in the barrel wall, and the insert is constituted by a blade spring whose length is equal to the circumference of the cylindrical portion of the inner wall plus the additional length produced by the depression, the ends of the blade spring in abutment to place it under compression so that it will follow the contour of the inner wall, including the depression. Preferably, the insert is self-lubricating and for maximum 3,621,650 Patented Nov. 23, 1971 efficiency, there are a plurality of depressions spaced equidistantly around the inner portion of the barrel and whose total circumferential area approximately equals that of the cylindrical portions between such depressions.
BRIEF DESCRIPTION OF THE DRAWING The single figure is a top plan view of a main spring barrel in accordance with the present invention, the main spring and slip spring being shown to illustrate the environment of the invention.
The barrel 1 illustrated in the drawing includes a drum 2 adapted to contain a spiral-coiled main spring m which may be associated with a slip spring S pressing the outer coil of the main spring and its retarding or brake element B against the inner wall of the drum 3 of the barrel in order to form a friction coupling preventing overwinding of the main spring, the inner end of the spring being secured to the arbor A. The inner wall of the barrel presents equidistant shallow depressions 4, alternating with cylindrical wall portions 3. In the example illustrated, there are six depressions, but this number might be different. Preferably, the depressions 4 have a cylindrical shape and their radius of curvature lies between R/ 2 and R, R being the inner radius of the barrel. In a particular embodiment, R is equal to 5.6 mm. and the depth of the depression is less than .1 mm. As seen in the drawing, the depressions 4 are milled in the mass of the drum 2 of the barrel.
A blade spring 5, the hardness of which is approximately equal to that of the main spring, is freely applied against the inner wall of the barrel drum 2 and takes exactly the shape of the depressions 4 and 0f the cylindrical wall portions 3. Its length is such that its ends 5 abut, so that the blade spring 5 is held in place under compression and cannot rotate with respect to the barrel.
The blade spring 5 is preferably specially manufactured. It is generally somewhat thinner than the main spring. As concerns its height, it has little importance; it is usually scarcely less than the inner height of the barrel drum, but is rather larger than the height of the main spring.
The presence of the depressions 4 ensures, on the one hand, the compression of the blade spring 5 and, therefore, prevents the latter from rotating with respect to the barrel. On the other hand, when the self-winding mechanism tends to wind the main spring, a moment arrives at which the friction coupling begins to slip; the presence of the depressions 4 permits controlling this slipping, i.e. the slipping takes place by small increments, the end of the outer coil of the main spring passing from one depression 4 to the next one; if there were no depression, a much greater slipping might occur, for instance by one full turn.
In the example illustrated, the ends 5 of the blade spring 5 abut within one of the depressions 4, but they might also abut along one of the cylindrical wall portions 3.
The blade spring 5 may be treated so that its surface is self-lubricating, for instance by phosphatization. In a modified embodiment, it may be made itself of a selflubricating material.
What we claim is:
1. A main spring barrel for a timepiece, comprising a drum having an inner cylindrical wall against which the outer end of the main spring or slip spring associated therewith frictionally engages to permit relative movement between the engaging spring and said inner wall to prevent over-winding of the main spring, said drum inner cylindrical wall being composed of a hard material and having a self-lubricating surface to withstand frictional wear, said inner cylindrical wall having at least one relatively wide shallow depression defining an arcuate surface disposed outwardly of the cylindrical surface of said inner wall, said depression having a circumferential width substantially exceeding its depth and including gradually sloping sides to inhibit excessive slipping of the engaged spring in short and rapid increments relative to said inner wall to preclude excessive Wear.
2. A barrel according to claim 1, wherein the depression has a cylindrical curvature, the radius of which is between R/ 2 and R, R being the inner radius of the barrel.
3. A barrel according to claim 1, wherein said drum inner wall comprises an insert defining said cylindrical and depression portions and composed of hard material and providing the frictional surface for engagement by the respective spring.
4. A barrel according to claim 3, wherein said depression is formed in said drum and said insert comprises a blade spring having a length equal to the inner circumference of the drum and the depression, the ends of said spring being in abutment and placing the spring under longitudinal compression to cause it to follow the contour of the depression as well as the cylindrical surface.
5. A barrel according to claim 1, comprising a plurality of depressions spaced equally about said drum and having a combined area substantially equal to the cylindrical portions between said depressions.
6. A barrel according to claim 5, wherein said depressions are formed in said drum and said inner wall is lined by an annular spring having a length equal to the inner cylindrical circumference portion of the drum and the depressions, and such as to place said spring under longitudinal compression to cause it to follow the contour of the depressions as well as the cylindrical portions.
7. A barrel according to claim 5, wherein the depressions each have a cylindrical curvature, the radius of which is between R/2 and R, R being the inner radius of the barrel.
References Cited UNITED STATES PATENTS 43,464 7/ 1864 Philippe 58-86 410,327 9/1889 Meylan 5886 654,873 7/1900 Church 5887 1,677,045 7/1928 Odom 5887 X FOREIGN PATENTS 208,209 1/1940 Switzerland 58-86 RICHARD B. WILKINSON, Primary Examiner G. H. MILLER, ]R., Assistant Examiner