Patent Publication Number: US-8540420-B2

Title: Gong mounting device for striking watch

Description:
The present invention relates to a device for mounting gongs in a striking watch, especially a device designed to be located against the crystal closing the case of such a timepiece. 
     Striking watches are fitted with a sound-generating member capable of producing one or more sound waves of different tones designed to propagate outside of the watch case. Typically, the member vibrating inside the case may be a gong which generates such waves after being struck by the hammer of the striking work. 
     The gong of a wristwatch usually consists of a circular-section metal bar or a metal strip wound around the watch movement. The length of the wound part determines the desired tone. 
     Mounted firmly at one of its ends, which is where the hammer strikes, the gong is thus supported by a block which is generally fixed to the movement or to the watch middle. 
     If watches are to have an effective sound function, they must be made capable of producing clearly audible sounds. While this feature usually creates few problems in so-called pocket watches or watches of the larger sizes, the same cannot be said of much smaller watches such as wristwatches, for which the subject of the present invention is primarily intended. 
     The limited amount of space available inside the cases of these watches directly limits the size of the multiple components which make up its movement. This miniaturization affects the amount of energy that such a watch can produce and in the last analysis is prejudicial to the acoustic capabilities of the sound-generating members. The case of such a watch is itself the first element that prevents the propagation of sound waves to the exterior. This disadvantage is accentuated by the presence of seals which are fitted to the great majority of wristwatch cases, especially at the interface between the crystal and the bezel, and between the middle and the back of the case. The latter may also be closed by a back crystal to allow the movement to be seen from the outside. 
     To improve sound propagation through the case, it is prior art to mount the block to which the gongs are attached on the movement and add a bearing against the crystal, either on the back or on the dial side. 
     In accordance with other mounting systems, it is suggested that the block be mounted on this crystal, by adhesive bonding or by welding. 
     Whether the crystal is mounted on the dial side or the back, it is invariably designed to close the case, which must usually be protected against the ingress of dust and water in order to properly protect the movement and the gongs. 
     The object of the present invention is to improve the transmission of the sound waves which is a significant component both of the strength of the sound perceived on the outside of the case and of the acoustic quality of the waves transmitted by the latter. 
     To this end, the subject of the present invention is a gong support mounting device in accordance with claim  1 . 
     For this purpose, a gong mounting device is suggested that is designed to bear against the crystal closing the watch case. The present device comprises a support or block capable of immobilizing at least one end of a gong inside the case, together with a means for mounting this block against the crystal. According to the invention, this mounting means is a clamping-type mounting means enabling the block to create pressure against the crystal. Being permanently set up by a clamping force applied to these two parts, this pressure has the advantage of accentuating the transfer of the strength and quality of the sound waves transmitted through the case. 
     In accordance with the preferred embodiment, the clamping-type mounting means incorporates a means of adjustment for modifying the force of assembly applied between the block and the crystal. 
     Advantageously, the clamping effect generated by this means is reversible. This makes it equally easy both to assemble and to separate the block and crystal once placed together. 
     Contrary to a received idea whereby the closing crystal or crystals of a watch case should not be pierced, the invention preferably suggests that the clamping-type mounting means should pass through the crystal via at least one hole made in the thickness of the crystal. 
     The clamping-type mounting means thus comprises preferably at least one threaded member that has, at one of its ends, a collar or bearing surface in contact with the outer face of the crystal. This member is designed to be screwed to a threaded portion located in the block to which the ends of the gongs are to be attached. 
     Advantageously, the arrangement of such a means makes it possible to create, in a range varying from the clamping limit to mechanical failure of the parts in question, a pressure of variable intensity between the block and the crystal. 
     The watch case can nonetheless still be made resistant to liquids and fine dust particles by the addition of at least one seal at the interface between the crystal and the bearing surface associated with the threaded member passing through the crystal. 
    
    
     
       Other advantages and features will become apparent on reading the following description referring to a preferred embodiment of the subject of the invention, and certain variants, which are given without implying any limitation and illustrated schematically and by way of example in the accompanying figures, in which: 
         FIG. 1  is a perspective view of the inside face of the crystal against which the mounting device, which holds the gongs of a striking wristwatch firmly in place, is positioned; 
         FIGS. 1   a  and  1   b  are detail views of the mounting device seen in  FIG. 1 , showing the inner and outer faces, respectively, of the crystal; 
         FIG. 2  is a simplified vertical cross section on II-II as marked in  FIG. 1   b.    
         FIG. 3  is a view similar to  FIG. 2 , illustrating a variant of the mounting device of the present invention; 
         FIG. 3   a  shows a variant of the device depicted in  FIG. 3 ; and 
         FIGS. 4   a  and  4   b  show a variant of the device illustrated in the corresponding  FIGS. 2 and 1   b.    
     
    
    
     It should be pointed out that the crystal used to close the case may either be that on the top, the dial side, or underneath, the back. 
     Referring to  FIG. 1 , this shows schematically the inner face  10   a  of a crystal  10  designed to close a watch case (not shown) for a timepiece fitted with a striking device. The latter is shown partially here by two gongs T 1 , T 2  immobilized at least one end  1 ,  2  (more clearly visible in  FIGS. 2 ,  3  and  3   a ) in a support termed the block  20 . It will seen that the number of gongs is irrelevant to the subject of the invention. Usually from 1 to 3, it basically depends only on the type of striking watch, examples of which include repeating watches, grand strike watches and chimes. 
       FIG. 1   a  shows in more detail the portion of  FIG. 1  shown ringed in dashes.  FIG. 1   b  shows the same detail but viewed from the outer face  10   b  of the crystal. As is clear from these figures, the block  20  is held in contact with the inner face  10   a  of the crystal by a mounting means  30 . This mounting means consists of a clamping-type mounting means that enables the block  20  to exert constant pressure on the crystal  10 . 
     With reference to  FIG. 2 , this shows the device of the invention in a simplified vertical cross section on II-II as indicated in  FIG. 1   b . The clamping-type mounting means  30  comprises at least one pair of threaded members, mainly at least one first element or threaded member  31  designed to engage with a threaded portion  32  on the block  20 . The first threaded member  31  is provided at one of its two ends with a head  33  designed to act as at least a bearing surface when this member is applied to the outer face  10   b  of the crystal  10 . As can be seen clearly in  FIG. 1   b , this head  33  preferably has a smooth surface with no recess or holding means of any kind. 
     Returning to  FIG. 2 , it can be seen that the threading on this first member consists of a tapped thread, that is internal threading  35 , formed in the tubular body of this member. More precisely, this tapped thread is machined in a blind hole in this open body in the opposite end to that topped by the head  33 . The outer part of the body of this first threaded member  31  is a preferably smooth and cylindrical outer segment or surface  37 . 
     As shown in  FIG. 2 , the threaded portion  32  corresponds more particularly to the threading of a second threaded member which is preferably completely embedded in the block  20 . Again preferably, this second member consists of a screw whose head  34  sits in a counterbored hole in the free surface of the block  20 . 
     With the preferred embodiment of the mounting device of the invention, the mounting device incorporates an adjustment means  40  that makes it possible advantageously to modify the clamping force generating the pressure between the block  20  and the crystal  10 . As shown in  FIGS. 1   a ,  2 ,  3 ,  3   a  and  4   a , this adjustment means can be used to act on the couple consisting of the first threaded member  31  and the threaded portion  32  which, depending on the case, corresponds to the second threaded member. This adjustment means preferably consists of a recess offering a means of control to allow one or other of these threaded members to be operated. In accordance with  FIG. 2 , this adjustment means  40  is on the head  34  of the second threaded member and allows this member to be tightened or slackened within the tapped thread  35  of the first threaded member  31 . 
     To ensure that the watch case remains sealed, one first seal  15  is also placed at the interface between the crystal  10  and the head  33  of the first threaded member  31 . Of circular shape and preferably torroidal, this seal is designed to be housed in the outer surface  10   b  of the crystal, in the depression of a chamfer machined around the edge of the circular opening through which the first threaded member is to pass. The diameter of this circular opening is preferably greater than that of the first threaded member in order to provide a clearance useful for positioning the block on the crystal, more specifically for positioning the gongs relative to the hammer of the striking device which will strike them. Thus, this clearance defines the latitude of positioning of the block  20  relative to the crystal  10  against which it is intended to be clamped. 
     The gongs T 1  and T 2  are each held in the block  20  by insertion of one of their ends  1 ,  2 , respectively, in a hole whose axis is parallel to that of the plane of the crystal  10 . This hole is preferably also situated in the vertical central plane of the block  20 , in accordance with the cross sectional view shown in  FIG. 2 . 
       FIG. 3  refers to a variant of the mounting means  30  illustrated in  FIGS. 1   a ,  1   b  and  2 . In this other embodiment, the adjustment means  40  can be seen to be provided on the head  33  of the first threaded member. In particular, the adjustment means  40  consists of a groove or slot comparable with or identical to that illustrated in  FIG. 1   a , allowing a tightening tool to be inserted in order to apply the appropriate clamping force. Of course, it would also be possible to use pins or holes instead of such a recess. 
     Although no clearance is shown in this figure between the first threaded member and the opening provided for its passage through the crystal, it will be understood that the pair of threaded members shown here in a variant could equally well perform its function if there were such a clearance. 
     The second threaded member illustrated in this  FIG. 3  consists more precisely of a pin, a first part  36  of the length of which is threaded. By this means the first threaded member  31  can be screwed to it. The second part  38  of the pin is designed to prevent any rotation of the second threaded member within the opening  21  in the block  20  for accommodating the second threaded member. Although shown as a through hole, this opening  21  could be a blind hole open to the crystal side. This member can be prevented from turning by a key, for example. Alternatively, rotation could be prevented by screwing the second part  38  into a thread tapped in the opening  21 , or by a bayonet system or clamping, with this second part being driven in. 
     In an identical or similar way, it would also be possible to prevent rotation of the first threaded member described in the preferred embodiment referring to  FIG. 2 . 
       FIG. 3   a  shows a variant of the device of  FIG. 3  in which the first threaded member  31  has no internal thread but does have an external thread  35 ′. The latter is at the end of the outer surface  37  of this member. Hence this outer surface comprises firstly a smooth segment designed to be positioned within the thickness of the crystal  10 , and secondly a threaded segment at the opposite end from the head  33 . The threaded segment is for screwing into the threaded portion  32 , which in this case consists of a thread tapped directly into the block  20 , for example a blind hole  21 ′. 
     The mounting device of the present invention will also preferably incorporate a means for positioning the block  20  against the crystal  10 , especially against the inner surface  10   a  of this crystal. In the embodiment shown in  FIG. 3 , this positioning means is provided by a bore  50  formed within the block  20 , coaxial with the opening  21 ,  21 ′ for insertion of the second threaded member. This bore is able to receive, without clearance, the free end of the outer surface  37  of the first threaded member. By engaging this outer surface in the bore  50 , the block  20  can be positioned precisely against the crystal  10 . The relative positions of the block and crystal can be defined by such a means provided there is no clearance between the first threaded member and the circular opening provided for its passage through the crystal. 
     As a variant, it would also be possible to achieve identical positioning by a system of engagement of a ball in a cavity, or a pin or dowel in an orifice. 
     Referring to  FIGS. 4   a  and  4   b , these illustrate yet another embodiment of the device shown in  FIGS. 2 and 1   b , respectively.  FIG. 4   a  corresponds to a simplified vertical cross section on as marked in  FIG. 4   b . This figure shows the addition of a collar  13  positioned between the crystal  10  and the associated bearing surface of the first threaded member  31 , in this case the head  33 . The latter thus bears against the crystal via the collar  13 , whose purpose is to extend the contact area on the outer face  10   b  of the crystal in order to reduce the pressure applied to the latter. 
     In such a configuration, a second seal  15 ′ is provided at the interface between the crystal  10  and the collar  13 , while the first seal  15  is in this case positioned at the interface between the collar  13  and the head  33 . This second seal  15 ′ is designed to sit in a groove formed in the inner surface of the collar  13 , along a closed curve running around the opening or openings for the passage of the first threaded member or members  31 . 
     As shown in  FIGS. 4   a  and  4   b , in which the clamping-type mounting means  30  comprises two pairs of threaded members  31 ,  32 , the collar  13  acts as a bridge between the two heads  33  and thus gives them a common seat. 
     In the embodiments described in the present account, the clamping force has been obtained by tightening a threaded member. However, it should be pointed out that other mechanical means could also provide the same effect. As an example, this clamping force could be obtained by rotating an eccentric or turning a small hinged lever arm. 
     As illustrated in the accompanying figures, the mounting device  30  comprises two couples, each consisting of a first threaded member  31  and a threaded portion  32 . However, the number of these couples could of course be different.