HK1009071B - Push button and method for assembling such push button - Google Patents

Description

Push button and method of assembling the same

Technical Field

The present invention relates to a push-button and a method for assembling the push-button, which make the production and installation of the push-button, in particular in a watch case, simpler and more economical, and also make the assembly thus obtained waterproof or hermetic.

Background

A common method of assembling a push-button that allows the state of the mechanical or electronic device of the timepiece to be varied by absolute pressure consists in introducing the stem of the push-button from the outside of the case and then screwing it from the inside of the case at its end, a stop preventing the stem from being extracted and limiting the travel of the return spring. Typically, the waterproofing and sealing between the push-button stem and the passage through the watch case is ensured by one or more separate sealing gaskets of the push-button device itself.

In order to simplify such a structure requiring working and mounting work in a small space, various other devices have been proposed.

In swiss patent No.579031, the stop is formed by a flange fixed around the stem and disposed on the stem. In swiss patent No.599612, the stop member is integral with the stem and has a slit at its inner end which provides sufficient spring force to allow the snap-fit attachment to the inside surface of the watch case. Other snap-on attachment methods have been proposed which use either the resilience of the flange supported by the stem, as described in swiss patent No.610467, or, conversely, the resilience of the neck of the hole which opens into the watch case and allows the stopper to pass forcefully, as described in swiss patent No. 675811. In each case, the waterproofing or sealing between the watch case and the button stem is ensured by a sealing gasket which is not held or compressed directly by the stopper, thus requiring a special button stem device or a special button head device. In addition, the guidance of the stem cannot always be ensured in a satisfactory manner, in particular when using the snap-fit technique.

Disclosure of Invention

It is therefore an object of the present invention to overcome the disadvantages of the previously known push button devices by providing a push button of simple construction which is easy to assemble.

The push-button of a chronograph device according to the invention, comprising a stem provided with an manoeuvrable head and slidable into a circular hole provided in the central part of said chronograph device, and a sleeve preventing the extraction of said stem, is characterized in that the stem comprises, on the side of the head, a cylindrical body extending with a groove for receiving an O-ring sealing gasket and with a stem, said stem having, at its end, an annular recess forming an axial column ending with an annular rim, and in that, between the wall of the circular hole and the stem, the sleeve is inserted, having substantially the same length as the stem, partially blocked by a ring having an outer diameter greater than the diameter of the circular hole and having a hole substantially equal to the diameter of the axial column, said sleeve compressing the sealing gasket and being fixed to the stem by riveting the annular rim onto the ring of the sleeve, the inner surface of the sleeve comprising a groove, the male portion of the shank snaps into the groove to allow the sleeve to be positioned prior to staking.

The return means of the push-button may be formed, for example, by a spring arranged between an annular groove of the middle part of the watch case and the inside of the push-button head.

The button head may be a part added to the stem, but may also be integral with the stem.

According to the invention, the sleeve fixed to the end of the stem by riveting allows to avoid accidental extraction of the push-button and at the same time allows to exert a controlled compression on the O-ring sealing gasket, so as to ensure a good waterproofing or sealing action.

According to another embodiment, the pressure control on the sealing cushion may be adjusted during assembly by providing one or more grooves on the inner surface of the sleeve complementary to an annular projection provided on the shaft.

A method according to the invention for assembling the push button of the above mentioned timepiece is characterized in that a return spring is placed in a groove in the central portion, an O-ring seal is placed in the groove, the stem is set in place from the outside of the case, a sleeve is placed over the stem from the inside of the case, and the annular rim is riveted to the outer surface of the ring.

Other characteristics and advantages of the invention will become more apparent when reading the following description with reference to the attached drawings, given purely by way of non-limiting example.

Drawings

FIG. 1 is a cross-sectional view of a portion of a watch case in which the push button device of the present invention is installed;

FIG. 2 is an enlarged view of the button end of FIG. 1;

fig. 3 is an alternative to the embodiment shown in fig. 2.

Detailed Description

Figures 1 and 2 show a push-button 1 mounted in a circular hole 2 in a central part 3 of a watch case, said push-button mainly comprising two parts: a stem 10 rotatable about an axis X-X with an manoeuvrable head 5 arranged on the outer extension of the central portion 3 and a sleeve 20 fixed to the other end of the stem 10, between which an O-ring sealing gasket 30 is pressed to ensure waterproofing or sealing between the wall of the circular hole 2 and the stem.

The stem 10 comprises a body 11 of the same diameter as the bore 2 and a stem 13 and a recess 12 extending from the body 11 and partially receiving an O-ring sealing insert 30 therein. The distal portion of the shank 13 includes an annular recess 16 defining an axial post 17 terminating in an annular rim 18.

The sleeve 20, made in one piece, comprises a tubular element 21, the tubular element 21 having a thickness substantially equal to the free space between the inner surface of the circular hole 2 and the outer surface of the shank 13 and a length substantially equal to that of the portion of said shank. The tubular element 21 is partially blocked at one end by a ring 22 having a thickness substantially equal to the total length of the axial post 17 and the annular rim 18, an outer diameter greater than that of the shank through the circular hole 2 and having a hole substantially equal to the diameter of the axial post 17, which in the embodiment shown flares outwards.

As shown in fig. 1, when stem 10 and sleeve 20 are assembled, annular rim 18 is folded back by riveting onto the flared portion of ring 22. According to the invention, "riveting" means any operation that allows the annular rim 18 to be folded back.

Thus, the particular method implemented will depend substantially on the type of material from which the stem portion is made. In the case of the most common metal rod, for example stainless steel, the annular rim 18 will simply be hammered. In the case of a material which can be heat deformed, for example reinforced thermoplastic (for example with glass fibres or carbon fibres), it is possible, for example, to use a heating tool with the same taper as the hole of the ring 22.

Therefore, to assemble the push-button of the invention, a return spring 6 is first placed in a groove 4 of the central portion 3, an O-ring seal gasket 30 is placed in the groove 12, the stem 10 and the head 5 are placed in position from the outside of the central portion (pre-assembly may be preceded if these parts are not already made in one piece), then the sleeve 20 is fitted over the stem 13 from the inside of the watchcase, and then the annular rim 18 is riveted to the outer surface of the ring 22, which will subject the O-ring seal gasket 30 to compression by the end of said sleeve tube 21. As shown in the example of fig. 3, the stroke of the sleeve 20 and its positioning before riveting can be adjusted by providing a groove 25 on the inner surface of the sleeve 20 to which the projection 14 provided on the shaft 13 is snap-fitted.

Returning now to fig. 1, it shows the push-button acting indirectly on the electronic control device through an intermediate push-button 8 provided on the casing 9 of the machine member. A person skilled in the art can of course envisage other mechanical or electronic control means without departing from the scope of the invention relating to the structure of the proximal button and the method of assembly of the button in the watch case.

Claims (3)

1. Push button for a timepiece including a stem (10) provided with an operable head and slidable in a circular hole (2) provided in a central portion (3) of said timepiece, and a sleeve (20) preventing the withdrawal of said stem (10), characterized in that the stem (10) includes a cylindrical body (11) on the side of the head (5), the body (11) extending with a groove (12) for receiving an O-ring sealing gasket (30) and a stem (13), said stem (13) having at its end an annular recess (16) forming an axial post (17), the axial post (17) ending with an annular rim (18), and in that the sleeve (20) is interposed between the wall of the circular hole (2) and the stem (13), has substantially the same length as the stem (13), being partially blocked by a ring (22) having an outer diameter greater than the diameter of the circular hole (2) and having a hole substantially equal to the diameter of the axial post (17), the sleeve (20) compresses the sealing packing (30) and is fixed to the shaft (13) by riveting the annular rim (18) to the ring (22) of the sleeve (20), the inner surface of the sleeve (20) comprising a groove (25) in which the projection (14) of the shaft (13) snap fits to allow the sleeve (20) to be positioned before riveting.

2. Push button according to claim 1, wherein the hole of the ring (22) is flared outwards.

3. A method for assembling a push button for a timepiece according to claim 1, characterized in that a return spring (6) is placed in a groove (4) of the central portion (3), an O-ring seal (30) is placed in the groove (12), the stem (10) is set in place from the outside of the case, the sleeve (20) is placed over the stem (13) from the inside of the case, and the annular rim (18) is riveted to the outer surface of the ring (22).