HK1006742B - Sealing ring - Google Patents

Description

The present invention relates to a seal.

In fine or micromechanical engineering, these seals are commonly called o-ring or tori seals because of their ring shape and generally round section.

An example from watchmaking will give a good idea of the use of the object of the present invention, which can be used in many other known fields, such as photography (zoom lenses) or general camera use.

In its first embodiment, the invention described in CH-A-432 388 concerns a watch case comprising two elements which can be adjusted at will in relation to each other, one comprising a first ring organ bearing a glass and the other a second ring organ on which the first is rotatively mounted, a sealant being inserted between these two organs.

Figure 1 of this description shows this earlier art somewhat modified from the document cited but still equivalent in form and arrangement of the seal.

The cut in Figure 1 shows that the watch case has a case 8, a bottom 13, a movement 7 housed in the case, a dial 6 over the movement 7. A set 3 comprising a bezel 1 with an inner ring shoulder 20, a glass 2 attached to the bezel by means of a first trim 4 and a ring organ forming the top 5 can be driven in rotation relative to the case and the dial.

A ring of 10-11 frames inside the frame 8 has a ring necklace 21 square resting on the shoulder 20 of frame 1 to hang or hold the rotating assembly 3 on the frame 8. The frame 8 has a ring necklace 24 at its bottom extending towards the center of the frame. On this necklace 24 is supported the ring of 10-11 frames. Of the 31 vertically placed and 25 forcibly through the frame 25 screws are used to force the screws into the frame.

As mentioned above, the 9th gasket has a round section. By its construction it also has two diametrically opposed injection nozzles, symbolized on the figure by two lines 14 and 15. In the dimensions shown here, experimentation has shown that when the 1st gasket is rotated, the 9th gasket rolls (or twirls) on itself irregularly so that the 14th and 15th gaskets form propellers all around the perimeter of the gasket creating a path between the outside world and the inside of the box, this path being used by water to penetrate the mechanism contained in the box.

It has been shown that the phenomenon of twisting can disappear if a ratio between the inner diameter of the Di ring and the diameter Dt of the section of wire constituting the ring is adopted for the o-ring which is less than a limit value which can be estimated at 20. Thus, for an o-ring commonly used in micromechanics and having a diameter Di between 0.8 and 5 mm and a diameter Dt between 0.4 and 0.5 mm, this ratio is at worst 5/0.4 = 12.5 and the o-ring will not twist.

In the latter case, as the Di diameter of 38 mm is required by the construction, a wire section of at least 1.9 mm would have to be provided to achieve a ratio of 20 and avoid the twisting of the joint.

The second disadvantage of the O-ring 9 shown in Figure 1 is that not only water but also dust can enter through the slot shown in Figure 19 and can damage the seal by its abrasive action, which may make the seal unwaterproof. To solve this problem, some manufacturers have two O-rings on top of each other, the first retaining dust and the second - which remains intact with water.

The seal ring described in FR-A-1 185 726 (preamble to claim 1) has a polygonal cross-section with two regions separated by a depression, which may suggest a dumbbell configuration. However, the axis of this dumbbell is perpendicular to the axis of the ring so that if the latter is used to seal a rotating bezel, the result would be a prohibitive increase in the overall diameter of the watchpiece.

The sealing devices incorporating a ring-sealing with an elongated section whose longitudinal axis is parallel to the axis of the ring-sealing of these devices are also known from document FR 849 948.

GB 654 509 also describes a manufacturing process for a flexible seal with a generally circular section, whereby the seal is made of injection grooves located outside the pressure zones.

As for document CH 549 236, it describes a watertight watch case with the glass fixed to a rotating bezel, the sealing between the bezel and the frame being achieved by means of two o-ring-shaped sealing linings placed one above the other in a neat housing in the bezel.

To overcome the above disadvantages, the present invention proposes a trim which, on the one hand, does not twist and, on the other hand, replaces two overlapping joints.

The invention will now be explained by means of the following description given as an example and by means of the illustration which illustrates it and in which: Figure 1 is a cut in a watch case showing a seal according to the previous art, as discussed above,Figure 2 is a similar view to Figure 1 where a seal according to a first embodiment of the invention is shown,Figure 3 is a partial and enlarged view of the cut shown in Figure 2 where a seal according to a second embodiment of the invention is shown, andFigure 4 shows a manufacturing process of the seal according to Figure 3.

The same parts, therefore bearing the same references, are partly reproduced in Figure 1 and are replaced by a joint 30 in Figure 2 with a straight section in the shape of a dumbbell defined by two bollets 31 and 32 connected by an isthmus.

In particular, and according to a first embodiment of the invention, Figure 2 shows that the cylinders have a rounded section somewhat reminiscent of the two o-ring joints mentioned above. The gasket 30 is mounted between two circular elements, the casing 1 and the casing 8, which are embedded in each other, the casing 1 being capable of moving rotatively in relation to the casing 8. This mounting defines the pressure zones located on the cylinders 31 and 32, these being four zones, namely zones 34 and 34' for the cylinder 31 and zones 35 and 35' for the gasket 32.

Figure 3 shows a second preferred method of execution of the invention. Here the bolts 31 and 32 have a polygonal section. Similarly to Figure 2, these bolts are connected by an isthmus 33. Here the same pressure zones 34, 34', 35' and 35' are found. Also, when molding the gasket 30, the injection nozzles 36 and 37 are arranged to be located outside the pressure zones.

Figure 4 shows the manufacturing process of the trim 30 shown in Figure 3. Figure 4 is a perspective view showing a partially cut mould from which the joint to be obtained emerges. The mould is made in an upper part 40 and a lower part 41. When these parts are joined, an annular cavity 42 is formed, the right section of which is in the form of a dumbbell with two bolts 31 and 32 having a polygonal section, the bolts being connected by an isthmus 33.

When the two parts 40 and 41 of the mould are assembled, the so-called two planes of joints 43 and 44 are formed through which the injection of elastic material takes place. Once this material has been injected (usually a polymerizable product), the two parts of the mould are disassembled and the gasket is removed.

In the particular case of Figure 4, the X-inclination of the ring cavity 42 in relation to the Y-direction of disassembly of the molds is of the order of 45°. Similarly, the polygonal section of the hollow bolts has lines 45, 46, 47, 48, 49, 50 and 51 which are oriented in such a way as to allow this disassembly without strain and thus without damaging the elastic material of which the liner is made when the unmolding is carried out.

The fact that the seal is inclined at the exit of the mould does not prevent its use directly in the workpiece to be sealed, mainly because there is some natural straightening and the internal diameter Di is large in relation to the section Dt.

It should be noted that the moulding technique described above can be equally well applied to the rounded-bottomed seal according to Figure 2.

In the example of use of the gimp according to the invention, a watchmaking part was mentioned above. The invention is not limited to this field of application, but is used when two parts with different travel speeds are present, these parts being mounted concentrically or telescopically.

Claims (6)

1. Annular injection moulded water-tight packing (30), having a straight cross-section in the form of a dumbbell including two enlargements (31, 32) connected by a neck (33), characterized by the fact that the axis of the dumbbell passing through the neck and the two enlargements is parallel to the axis of the packing and by the fact that it is assembled between two circular elements (1, 8) fitted into one another and adapted to be displaced relative to one another around an axis substantially parallel to the packing axis, said assembly defining pressure zones (34, 34', 35, 35') localized on said enlargements, the injection burrs (36, 37) presented on said packing being located outside said pressure zones.
2. Packing according to claim 1, characterized by the fact that the enlargements exhibit a rounded cross-section.
3. Packing according to claim 1 characterized by the fact that the enlargements exhibits a polygonal cross-section.
4. Method of manufacture of the packing according to claim 3, characterized by the fact that a two-part mould (40, 41) is provided which once the parts are joined exhibits an annular cavity (42) the straight cross-section of which has the form of a dumbbell, the axis (X) of said dumbbell being inclined like the rim of a plate, that an elastic material is injected into said cavity, that the two parts of the mould are taken apart in order to extract the packing and that the packing is separated from the injection residue by cutting.
5. Method according to claim 4, characterized by the fact that the inclination of said annular cavity relative to the direction of separation (Y) of the mould parts is such that said injection burrs are located outside said pressure zones and that the polygonal cross-section of the enlargements in said cavity exhibits straight lines (45 to 51) oriented so as permit taking the mould apart without stressing the material of which the packing is made.
6. Utilization of the packing according to claim 1, characterized by the fact that said packing is arranged between a caseband (8) and a rotating bezel (1) in the timepiece.