CROWN FOR A TIME PIECE AND TIME PIECE WITH CROWN AND CRYSTAL

TECHNICAL FIELD

The present invention relates to a crown for a time piece comprising a case insert to be fixed in a watch case, a crown head mounted on the case insert, an actuation unit to move the crown head between a locked position and an unlocked position of a functional stem extending into the watchcase, and at least one seal between the case insert and the crown head; and further relates a time piece with such a crown and a crystal mounted on the watch case. PRIOR ART

Timepieces and more particularly watches have one or more crowns for setting functions of the watch or winding the clockwork. Seals have always been suggested to be used at such occasions as in US 3,130,539. At the beginning these seals were intended to be dustproof or waterproof. Therefore, these devices can then be used under water when the seals perform sufficiently well.

Things become more complicated, when professional divers descend to great depths to carry out work and are then returned to the surface using a pressurised chamber which controls the decompression stops required for the diver's health. Divers watches then include both a winding crown and a valve to prevent the watch exploding when the diver returns to the surface. During these decompression stops, gases - essentially helium - penetrate the divers' watch case through the sealing gaskets which are essentially suited to preventing water or dust from entering inside the watch. When the pressure in the chamber drops during decompression stops, if there is no pressure balance device in the watch, excess pressure may build up inside the watch relative to the surrounding pressure, which may cause the watch to explode.

US 2014/010055 A discloses a push button for a timepiece for correcting the time display associated with a decompression valve within a single control device, using springs to act as a valve spring.

Other prior art suggests helium permeable apertures as US 2011/235477 A.

Other prior art suggests a plurality of additional seals as US 201 1/051571 mitigating the gas transfer between the outside and the interior of the watch which is and remains a space which needs more or less an air environment to function. EP 2 615 149 suggests using joints have a permeability to hydrogen or helium gas of less

- 1 7 2 - 1 -1

than 5.10 m Pa s according to NF ISO 2782 even more mitigating this issue.

US 7,909,503 B2 discloses a crown including a crown shaft, a crown head, a screw ring, and a spring for urging the head in a direction of being separated from a case band. The crown shaft cooperatively moving a hand setting stem is provided with a rotational force receiving portion of a deformed shape. The receiving portion is arranged at outside of a pipe fixed to the case band and is provided with a diameter larger than that of a male screw portion formed at the pipe. A head main body of the crown head includes a rotational force transmitting portion of a deformed shape fitted attachably and detachably to the receiving portion, a ring mounting face in a circular shape formed on one end side of the main body from the transmitting portion, and an inner peripheral face in a circular shape formed on other end side of the main body from the transmitting portion at an inner periphery thereof.

FR 392 462 A shows a crown and further components allowing to displace the crown of a watch while acting on two arms which can glide within a guide and which allow at the same time the passage for the element maintaining the crown in a correct position

DE 19 50 955 discloses a crown for a watch, especially a vacuum watch, having a sealing packing.

SUMMARY OF THE INVENTION

Based on this prior art it is an object of the present invention to provide a crown for a timepiece resolving the above mentioned challenges relating to helium tightness or permeability asking on one hand for an additional opening in the watch case and on the other hand more complicated crowns with additional polymeric seals.

This object can be achieved with a crown for a time piece having the features of comprising a case insert to be fixed in a watch case, a crown head mounted on the case insert, an actuation unit to move the crown head between a locked position and an unlocked position of a functional stem extending into the watchcase, and at least one seal between the case insert and the crown head. Then, one seal is a metallic seal, i.e. a metal- to-metal seal, comprising an inner male seal body being a metal solid of revolution and a complementary metal female seal recess. The female seal recess is provided in the case insert having a stem opening and the inner male seal body comprises a stem receiving bore which is in line with the stem opening.

The sealing surface between the inner male seal body and the metal female seal recess can be a portion of a surface taken from the group comprising a spheroid, an oblate spheroid, a prolate spheroid, a paraboloid, an elliptic hyperboloid or having a conical form to name a few. Usually when the locking action comprises a longitudinal relative displacement between the two metal surfaces, a rotation of the crown head is thus possible, wherefore the solid is quite well adapted.

A crown head comprises an annular recess, wherein the case insert comprises a complementary cylindrical sleeve portion extending into the annular recess and wherein a annular top seal is provided in a reception in the annular recess contacting the free end of cylindrical sleeve portion.

An annular reception can be provided in longitudinal direction adjacent to the female seal recess at the inner wall of the case insert. Then an annular stem seal is provided in said annular reception facing a portion of the crown head above the inner male seal body. The crown head and the inner male seal body can be provided as two separate parts. Then an inner central blind bore is provided in the crown head to accommodate a guide shaft portion of the inner male seal body and wherein a spring is positioned between the free end of the guide shaft portion and the bottom of the inner central blind bore in the crown head. Within this solution, reception noses for said spring can be provided on the free end of the guide shaft portion and on the bottom of the inner central blind bore. On the other side, the crown head and the inner male seal body can be provided in one single piece. Then, preferably, an inner thread is provided at the case insert facing a complementary outer thread provided at the crown head for effecting the switch between a locked position and an unlocked position of the crown. Within this solution, the actuation unit comprises at least one bayonet groove and associated bayonet locking groove portion as well as at least one associated locking pin provided at the crown head and at the case insert, respectively, or vice versa, for effecting the switch between a locked position and an unlocked position of the crown. Of course, it is possible to provide two or more, especially three or four such tracks and complementary locking pins, especially in regular angular distances, i.e. 120 degree, if three locking pins and corresponding grooves are provided.

The crystal is usually attached to the timepiece with polymeric seals. Such seals degrade the advantage provided by the above mentioned crown. It is therefore a further object of the present specification to provide a timepiece with an improved solution for the attachment of the crystal at the watch case to ensure helium tightness at this surface.

Such a timepiece comprises a crown, a watch case and a crystal, wherein the watch case comprises a circumferential flat upper surface and wherein the crystal comprises an associated congruent circumferential flat lower surface and the crystal and the watch case are welded together at the complementary surfaces forming a helium-tight connection between crystal and watch case.

The circumferential flat upper surface of the watch case can be part of a recess comprising an inner shoulder, wherein the crystal abuts against and is welded on the inner side with this shoulder of the watch case.

The outer wall of the watch case near the crystal and the initial upper surface of the crystal can provide a flush wall connection which provides an additional esthetical effect beyond avoiding seals not allowing a side view on the dial under a shallow angle.

Further embodiments of the invention are laid down in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described in the following with reference to the drawings, which are for the purpose of illustrating the present preferred embodiments of the invention and not for the purpose of limiting the same. In the drawings,

Fig. 1 shows a schematical cross-sectional view of a crown in the locked position according to an embodiment of the invention in a partly shown watch case; Fig. 2 shows an exploded view of the crown according to Fig. 1 ;

Fig. 3 shows a cross-sectional view of the crown according to Fig. 2;

Fig. 4 shows a schematical cross-sectional view of a crown according to a further embodiment of the invention in a partly shown watch case;

Fig. 5 shows a side view of the mounted crown of Fig. 4;

Fig. 6 shows a cross-sectional side view of a complete watchcase according to an embodiment of the invention when used in connection with a crown according to an embodiment like Fig. 1 or Fig. 4;

Fig. 7 shows an enlarged detail view of the circle VII shown in Fig. 6;

Fig. 8 shows a perspective view of a bayonet case insert of the embodiment of Fig.

1 to realize the locking position of the crown head;

Fig. 9 shows a perspective view of a detail of a crown head and a crown body with the position of the locking pins, and also the bayonet sweep of a further embodiment

Fig. 10 shows a plan view of the embodiment of Fig. 9;

Fig. 11 shows a schematical cross-sectional view of the crown according to Fig. 1 in the unlocked position; and

Fig. 12 shows a side view of the mounted crown of Fig. 1 1.

DESCRIPTION OF PREFERRED EMBODIMENTS

Fig. 1 shows a schematic cross sectional view of a crown 10 according to an embodiment of the invention in a partly shown watch case 5. The description of Fig. 1 will be made in connection with Fig. 2 showing an exploded view of the crown 10 according to Fig. 1.

Watch case 5 is shown as a wall having a circular watch case opening 6 into which the case insert 20 is lodged. The case insert 20 is retained either by an interference fit or a threaded interface at the interface surface 26 between the watch case opening wall and the cylindrical outer surface of the case insert 20. The lower cylindrical portion 21 is followed by a larger cylindrical portion 22 providing a flange 24 sitting on the flattened watch case surface 8. The case insert 20 comprises a further cylindrical portion 23 providing the counter seal part for top seal 130. Case insert 20 comprises a through bore to accommodate, seen from the outside crown head 40, male metal seal body 60 as well as the movement stem 7 which can also be a winding and setting stem. Winding and setting stem 7 connects with the movement of the watch and is lodged in a stem receiving bore 65 provided centrally in the male metallic seal body 60. Bore 65 is a blind bore sufficiently long to allow a holding fit of stem 7.

The cylindrical top seal part is an annular upper surface 27 providing the lower seal bearing surface for top seal 130.

The crown head 40 comprises an outer annular head body 41 providing for an annular recess 47 to accommodate the cylindrical portion 23 of case insert 20. On the inside of the annular recess 47 is provided an annular extension lodging parts being not visible the side view of Fig. 2 in connection with the bayonet closing. The inner projection has a specific diameter and ends with a flange edge 42 followed by a smaller diameter guiding sleeve 43.

The flange edge 42 is intended to be positioned in front of the inner shoulder surface 25 of the case insert 20 when the female metal seal recess 28, followed by the stem seal 30 opens up into the bayonet related portion. The guiding sleeve 43 has a tapered end portion 44. The outer surface of the guiding sleeve 43 provides the seal counter surface for stem seal 30 as will be explained below. Crown head 40 further comprises a central inner blind bore 45 wherein the blind bore 45 comprises a reception nose 46. The blind bore 45 has a diameter to accommodate the shaft part 61 of the male metal seal body 60. The shaft part 61 equally comprises at its upper end a reception nose 62. The distance between the two reception noses 46 and 62 is predetermined to allow accommodating the direct metal regulation spring 1 10 which is a torsion spring pushing the male metal seal body 60 out of the blind bore 45 against the female metal seal recess 28 in the through bore of case insert 20.

Below the inner shoulder surface 25 is provided an annular recess in the case insert 20 to accommodate the stem seal 30. Stem seal 30 is an O-ring. Preferably, a graphite seal could be used as stem seal 30 in this position, allowing for less maintenance and being longer lasting than an O-ring; however other embodiments can use Viton, EPDM or rubber seal materials. Within the crown head 40 is provided in the inner annular recess 47 an additional recess in the longitudinal direction of the crown head to accommodate the top seal 130 which abuts on the other side on the annular edge of case insert 20.

In the cylindrical top seal part 23 of case insert 20 is provided a number of bores 29, arranged equally spaced around the diameter of the case insert 20, to accommodate bayonet locking pins 80. The number of bores 29 can be one, two, three, four or more bores 29, although higher numbers will not provide a different handling of the bayonet. The locking pins 80 can be screwed in, welded in or bonded in place. Ideally the pin 80 can be removed as it would allow disassembling the crown and therefore allowing for maintenance to be done. Generally the pin 80 is mounted from the outside when the crown is in the unlocked position. Fig. 11 as well as Fig. 12 show the gap 89 between the lower edge of the crown head 40 and the upper edge of inner shoulder 67, providing access to the bore accommodating the locking pin 80. Locking pin 80 extends into the inner part of annular recess 47 and is lodged within bayonet sweep 82 within the bayonet locking groove 84. In other words, crown head 40 can be rotated around the longitudinal access of the crown 10 which is at the same time the longitudinal access of the winding and setting stem 7 and can in this respect be switched between the locked position in Fig. 1 and an unlocked position shown in the drawing of Fig. 1 1.

Fig. 3 shows a cross sectional view of the crown 10 according to Fig. 2. Crown head 40 comprises the annular recess 47 which ends in an annular groove 48 inside the recess 47 to accommodate the top seal 130. Within the central through bore in case insert 20 is provided a further seal groove 31 to accommodate the stem seal 30. The section view of Fig. 3 shows two additional bores 29 but cut in the section view and with the pins as number 80 assembled in place. These drawings show three bores, equally spaced around 360 degrees. The number and spacing of the bores/pins can be altered as desired.

Fig. 4 shows a schematic cross sectional view of a crown according to a further embodiment of the invention in a partly shown watch case 5. Identical features as the winding and setting stem 7 receive the same reference numerals; similar features receive similar reference numerals. Nevertheless the major difference between the embodiment of Fig. 1 and Fig. 4 is related to the way that the metallic seal 100 is built and actuated. Both drawings show the crown in a locked position. Case insert 120 sits in a similar way with interface surface 26 in the watch case opening 6 and has an internal through bore with the female metal seal recess 28, the seal groove 31 to accommodate the stem seal 30 and it has the annular top seal part 23 with the upper surface as seal bearing 27 for the top seal 130. The main difference is that on the inside of the cylindrical top seal part 23 is provided an inner thread 180 being engaged by an outer thread 141 of crown head 140.

Fig. 5 shows a side view of the mounted crown 140 of Fig. 4 with a partly shown watch case 5 onto which is mounted the case insert 120 on to which is provided the crown head 140, shown in its locked position.

Fig. 6 then shows a cross sectional side view of a complete watch case according to an embodiment of the invention when used in connection with a crown 40 or 140 according to an embodiment like shown in Fig. 1 or Fig. 4. Fig. 7 then shows an enlarged detail of the circle VII shown in Fig. 6.

Watch case 5 comprises a movement 51 , a back cover 52, a dial 53 and a crystal 54. The back cover 52 is attached in the usual way to the watch case 5 comprising a form fit of back cover 52 with a shoulder inside watch case 5 as well as a seal provided in groove 55. This recess 55 makes space for a metallic compression seal, it basically looks like a "C" in its cross section but is made out of metal, e.g. stainless steel, copper or brass, rather than a polymer. This makes for a helium tight seal between the case 5 and the case back 52.

On the other side of the watch case 5 the dial 53 is positioned on the upper surface of the watch case 5 as well as the crystal 54. The connection of crystal 54 with watch case 5 is shown in detail in Fig. 7, reflecting the circle VII of Fig. 6. A recess with an upper surface 56 is provided around the edge of the upper surface of watch case 5. The sapphire 54 of the watch is extending with a flat complementary surface 58 on to the upper surface 56 of watch case 5. Crystal 54 abuts there on the inner side against a shoulder 57.

The crystal 54 is welded at the surfaces 56 and 57 onto the watch case material. Although sapphire windows can be welded with high temperature processes on metallic substrates, it is preferred to use a low temperature process due to the high stresses induced between the two materials. A low temperature process is a process with a process temperature of less than <400°C, the watch case 5 is connected with the crystal 54 under such a processing temperature.

With this feature of attaching crystal 54 to the edge near upper surface of the watch case 5 it is possible to avoid using of an O-Ring at that position. At the same time it is easily possible to provide a flush wall connection between the upper surface 71 of the crystal 54 (being also the side wall 73 of the crystal 54 at this occasion) and the outer wall portion 72 of the watch case 5 near the crystal 54 and the welding allow for a helium-tight connection between crystal 54 and watch case 5.

Therefore, the crystal sealing supports the crown sealing performance in a synergetic way. The crown sealing arrangement according to the embodiments of Fig. 1 or of Fig. 4 is introducing a metal contact service between a metallic seal and a case insert 20 or 120. In the following paragraphs, reference numerals are only mentioned in reference to the embodiment of Fig. 1, although it is clear that the functionality applies in the same way to the embodiment of Fig. 4. This arrangement is capable of maintaining an effective seal against a very high relative pressure of fluid mediums, e.g. water and is also far more capable of preventing the ingress or egress of gasses, especially helium when compared to elastomeric O-Rings. An additional advantage of the mechanical seal in general is the improved performance over time, since there is no degradation of performance due to changes in the composition of one of the components as e.g. the usual weak point of watch case sealing being the conventional elastomeric O-Ring.

The function of the metal insert is as follows: The crown case 20 has a through hole within which the case insert 20 is supported and retained by either an interference fit or a threaded interface. The case insert 20 has a spherically profiled concave surface at its central longitudinal axis which matches with a similar profiled convex spherical surface of the metallic seal body 60. The two spherical faces of the metallic seal body 60 and of the case insert 20 as such are forced together by the regulating spring 110. This regulating spring 1 10 is supported by the crown head 40 which is intrinsically connected by locking pins within the case insert.

In further embodiments not shown in the drawings, the two mechanical sealing surfaces may not be spherical. The complementary sealing surfaces could be of any form which produces contact between the case insert 20 and the metallic seal body 60; for example this case insert 20 could be conical, follow a parabolic arc or an elliptic arc. In this arrangement the spherical metallic seal will contact the case insert within a theoretically infinitesimal area, which ensures a helium tight seal as well.

Hertzian stresses at the contact point will be very high and as a result will locally deform the two contacting surfaces such that gap between the two contacting surfaces, on the macro level, will be reduced significantly. As a result, the ingress/egress of molecules larger than the gap size will be prevented. This prevents the movement of liquids and gasses from breaching the metal seal 100. For this the crown 10 has two operating positions; locked and unlocked. This is true for both embodiments of Fig. 1 and Fig. 4.

In the locked position the crown 10 is positioned towards the case 5, in this position three seals are actively engaged. The metallic seal 100, the winding seal 30 and the top seal 130. The metallic seal 100 has been described above and is the primary seal. The top seal 130 is a compressed between the underside of the crown 10 and the case insert 20 and forms a secondary seal. The winding seal 30 is always active regardless of the crown positions.

In the unlocked position, the crown 10 is positioned away from the case 5 and the top seal 130 is disengaged. The winding seal 30 remains engaged with no loss of functional performance. The winding seal 30 shall prevent the ingress/egress of media as fluids and dusts while the crown mechanism is being used to adjust the time of winding the watch. In the unlocked position, the regulating spring 110, if present as in Fig. 1, may still provide a force to the metallic seal 100 which may still provide a satisfactory seal. However, the force on the metallic seal will be less than when in the locked position.

The top seal 130 and the winding seal 30 are intended to be graphite seals, however, unlike the universally used elastomeric O-Rings which are sensitive to things like temperature, type of media they are immersed in, age, condition of surroundings, surfaces, etc. graphite seals are far more robust. The crown 10 is moved between locked and unlocked positions by the wearer rotating the crown head 40. When rotated clock wise or anti-clock wise in another form of the invention, the crown head 40 is guided towards the watch case 5 by locking pin tracks 80 and locking pins located in the case insert 20. There in the locked position the metallic seal regulation spring 110 is properly compressed, forcing the metallic seal into the case insert 20. Due to the regulating spring 110 also applying a force onto the crown, the crown 10 is held in its locked position more positively preventing unintentional unlocking of the crown 10.

When the crown is in the locked position and this rotated anti-clock wise, the crown is guided away from the watch case 20 by the tracks 80 in the crown and locking pins in the case insert. Such a bayonet like mechanism determines through the profile of the guiding tracks the relationship between rotational and linear (=longitudinal) movement of the crown 10. The regulating spring 110 provides assistance in moving the crown 10 to the unlocked position. To prevent the crown 10 from escaping from the case insert entirely, a locking pin groove runs around the circumference of the crown inner structure and is connected to locking pin guide tracks.

The arrangement prevents the crown from being separated from the watch insert 20. In order to remove the crown 10 the locked pins need to be removed from the case insert 20. When the crown 10 is in the locked position, the locking pins are not accessible. The crown must be returned to the unlocked condition to provide access to the locking means. This provides another level of safety to prevent the crown from moving out of the locked position unintentionally.

In one form of the invention not shown in the drawings, the crown 10 has small hole drilled through the outer circumference, approximately the same size as the locking pins. These are positioned such that the locking pins become visible and concentric to the holes only in the fully locked position. This provides a method for the wearer to easily see whether the crown is in the fully locked position or not.

Fig. 8 shows the case insert as a part of an embodiment of Fig. 1 to realize the locking position of the crown head. All reference numerals of Fig. 1 or Fig. 2 are also used here. The lower cylindrical portion 21 has an outer thread which has a complementary part in watch case 5 as inner thread in the watch case opening 6. Three bores 29 are provided in a regular 120 degree distance in the wall of the cylindrical top seal part 23 to accommodate three locking pins 80 which will be running in three associated bayonet grooves 82. Fig. 9 shows a perspective view of a detail of a crown head 40 and a crown body as case insert 20 with the position of the locking pins 80, and also the bayonet sweep or bayonet groove 82 of a further embodiment. Fig. 10 shows a plan view of the embodiment of Fig. 9. The guiding sleeve 43 of crown head 40 is partly embedded in the cylindrical top seal part 23 of case insert 20. The inner blind bore 45 accommodates the spring 1 10 (not shown). Three locking pins 80 are provided through the wall of cylindrical top seal part 23 and are lodged inside three inclined bayonet sweeps 82 provided in an angular distance of 120 degree one from the other. The three bayonet sweep 82 end in their upper portion in three horizontally arranged bayonet locking groove 84, also provided in the same angular distance.

Fig. 1 1 shows a schematical cross-sectional view of the crown 10 according to Fig. 1 in the unlocked position; and Fig. 12 shows a side view of the mounted crown of Fig. 11 and this drawing is similar to Fig. 5 but in the unlocked position of the crown 10. The main difference between Fig. 1 and Fig. 11 is the position of the crown head 40, which is displaced in the longitudinal direction of the crown away from the watch case. Therefore a larger gap 89 appears between the lower edge of the crown head 40 and the shoulder 67 of the case insert. Then the top seal 130 is no longer engaged by the opposite upper surface 27, acting as seal bearing in Fig. 1. There is now a non negligible portion of the annular recess 47 between these two surfaces. However, stem seal 30 is still touching the outer surface of the guiding sleeve 43 and acts as seal. Spring 1 10 is under less tension but ensures that the male metal seal body 60 is pressed in the through bore 69 against the metal female seal recess 28 of the case insert 20 as a direct metal seal 100.

The locking pins 80, here only one is shown, is at the lower end of the bayonet sweep groove 82 and ensures that the crown head cannot get loose. Fig. 12 shows in this respect that the gap 89 is large enough to access locking pin 80 just under the lower edge of crown head 80 for dismounting the crown, if necessary.

LIST OF REFERENCE SIGNS watch case 52 back cover

watch case opening 53 dial

winding and setting stem / 54 crystal

movement stem 55 groove

flattened surface 56 upper surface

crown 57 shoulder

case insert 58 flat lower surface of crystal cylindrical portion 60, 60' male metal seal body cylindrical portion 61 shaft part

cylindrical top seal part 62 reception nose

flange 63 male metallic seal body inner shoulder surface 64 male metallic seal surface interface surface 65 stem receiving bore upper surface / seal bearing 67 inner shoulder

female metal seal recess 69 through bore

bore 71 outer surface of crystal stem seal 72 side wall of watch case seal groove 73 side wall of crystal stem opening 80 bayonet locking pin head 82 bayonet sweep

annular head body 84 bayonet locking groove flange edge 89 gap

guiding sleeve 100 direct metal seal

tapered end portion 110 direct metal regulation sprinj blind bore 120 case insert

reception nose 130 top seal

annular recess 140 crown head

annular groove 141 thread at crown head movement 180 thread at case insert