Abstract:
A watch, in particular a dive watch, having a movement ( 16 ) which is arranged in a watch case ( 12 ) and can be used to drive an hour hand ( 3 ) via an hour tube and a minute hand ( 4 ) via a minute tube in a fashion sweeping over a dial ( 1 ). Also present is a pressure detecting device for detecting the ambient pressure outside the watch case ( 12 ) and a display for representing the detected pressure values. There is arranged in the watch case ( 12 ) a mechanical pressure transducer to which the ambient pressure outside the watch case ( 12 ) can be applied and by means of which a mechanical depth measurement mechanism ( 17 ) of a mechanical display can be driven.

Description:
FIELD AND BACKGROUND OF THE INVENTION 
     The invention relates to a watch, in particular a dive watch, having a movement which is arranged in a watch case and can be used to drive an hour hand via an hour tube, and a minute hand and, if appropriate, a second hand via a minute tube in a fashion sweeping over a dial, as well as having a pressure detecting device for detecting the ambient pressure outside the watch case and a display for representing the detected pressure values. 
     It is known in dive watches to detect the ambient pressure by means of electric or electronic sensors and to convert it in an electronic evaluation device into signals for driving a dive depth display. Both the detection and the representation of the ambient pressures require a battery as power supply. If the battery performance drops, the dangerous situation arises for the diver that the sensors and the display can still function to a certain extent, with the result that the user assumes he has a fully functional dive watch. However, because of the no longer adequate power supply both the values detected and the values displayed are incorrect. 
     It is possible thereby for situations which endanger the diver&#39;s health or even life-threatening situations to occur, for example due to diving deeper than intended or ascending more rapidly than permissible. 
     FIELD AND BACKGROUND OF THE INVENTION 
     It is therefore the object of the invention to create a watch of the type mentioned at the beginning in which these disadvantages of known watches are avoided. 
     This object is achieved according to the invention there is arranged in the watch case a mechanical pressure transducer to which the ambient pressure outside the watch case can be applied and by means of which a mechanical depth measurement mechanism of a mechanical display can be driven. Since none of the watch components for displaying the dive depth depends on a supply of electric or mechanical power, all the disadvantages based on reduction in power and power loss are avoided. The depth display of the watch is completely autonomous and thus always operational and fully functional. 
     In a simple design, the mechanical depth measurement mechanism can have a display shaft which can be rotatably driven by the pressure transducer and carries a depth hand which can sweep over a depth scale. 
     A low overall size is achieved by virtue of the fact that the display shaft is arranged coaxially with the hour tube and minute tube, and the depth scale is arranged on the dial. 
     If the scale division of the depth scale corresponds to the scale division of the minute scale, the display on the depth scale can be taken in just as quickly and easily as is already usual from habit in the case of minute scales on analog watches. 
     A further contribution to reducing the overall size results when the display shaft projects coaxially through the hour and minute tubes and, if appropriate, the second tube. 
     The pressure transducer can be connected to the environment via a measuring opening. 
     If a measuring opening in the watch case is constructed such that it can be closed manually in order to connect the pressure transducer to the environment, a depth measurement can consciously be performed only if the measuring opening is opened for this purpose. If the watch is also used in other regions in which substantially higher pressures prevail than for the measuring range suitable for the pressure transducer, the pressure transducer is protected by closing the measuring opening. 
     As an alternative to this, a closing device of the measuring opening can be constructed as a pressure-reducing valve by means of which the measuring opening can be closed upon overshooting of a specific ambient pressure. 
     In a simple design, the measuring opening can in this case be closed manually by a screwed crown. 
     If it is possible to apply the ambient pressure outside the watch case to the mechanical pressure transducer via an incompressible medium, it is impossible for it to be damaged by pollutants and aggressive substances such as, for example, also sea water, which reach the pressure transducer from outside. 
     The incompressible medium can be a liquid such as, for example, water, in particular distilled water, or oil. 
     In a simple way, the ambient pressure can be applied to the incompressible medium via a movable wall. 
     If in this case the movable wall is a diaphragm which is clamped permanently and tightly at its circumferential edge on a housing, the result is simultaneously to achieve a tight separation of the region filled with the incompressible medium from the environmental region. 
     The purpose of transmitting the ambient pressure directly, and thus without impairment, to the pressure transducer is furthered when there is constructed in the watch case a measuring opening which serves for the application of the ambient pressure to the pressure transducer and leads to a chamber which is filled with the incompressible medium and of which one wall is the movable wall to which the ambient pressure can be applied. 
     A design which is particularly simple and not prone to defects consists in that the pressure transducer is an annular spring pressure gauge with an annular Bourdon spring of which one end is fastened on the watch case and is connected to the measuring opening and of which the other end, which can be freely swiveled radially, can drive in a movable fashion the depth measurement mechanism by means of which the pivoting movement of the free end of the Bourdon spring can be converted into a movement which can drive the display shaft rotatably. 
     For the purpose of protection against overloading, the capacity of the free end of the Bourdon spring to swivel radially can be limited by stops. 
     It is preferable for the Bourdon spring to be arranged surrounding the movement in the watch case, with the result that only a small overall space is required. If, in this case, the Bourdon spring is arranged with play in an annular chamber of the watch case, the walls of the annular chamber forming the stops, the Bourdon spring is simultaneously protected against overloading in conjunction with a small overall size. 
     The purpose of directly transmitting the ambient pressure to the Bourdon spring is furthered when the interior of the Bourdon spring is connected to the chamber via the measuring opening and is filled with the incompressible medium. In this case, the chamber with the movable wall serves at the same time as a volume-equalizing chamber for the volume of the Bourdon spring, which increases with rising pressure owing to widening of the curvature. 
     If the movable wall can be subjected to the action of a manually displaceable pusher in a fashion reducing the volume of the chamber, it is possible by applying a specific force to the pusher to simulate a specific dive depth, and thus to check the functionality and accuracy of the display. 
     Moreover, the pusher forms a support surface for the movable wall, which is constructed, in particular, as a diaphragm. 
     In order to define the position of the movable wall under standard ambient pressure, the capacity of the pusher to be displaced in the direction of which the volume of the chamber is increased is limited by a stop. If the stop can be set adjustably in the displacement direction of the pusher in this case, the pressure transducer can be adjusted by the pusher. 
     For the purpose of simple assembly, the chamber and/or the pusher can advantageously be arranged in a crown. 
     Since the position of the depth hand depends only on the position of the end piece, fixed to the case, of the Bourdon spring, in the case of changes in air pressure, an adjustment of the hand already comes about which falsifies the actual dive depth during a dive. In order to be able to set the depth hand exactly to zero before a dive, the end of the Bourdon spring fastened on the watch case can be adjusted radially. 
     For this purpose, in a simple construction the end of the Bourdon spring is fastened on the watch case via a shaft projecting radially out of the watch case, the shaft being adjustable in the direction of its longitudinal extent. For the purpose of adjusting the shaft easily, it is possible for the shaft to be guided displaceably in a crown bush which is firmly connected to the watch case and is provided with a thread on which there is arranged a union nut on which the free end of the shaft is supported. In order to permit fine adjustment, the thread can be a fine thread. The play in the thread is eliminated by virtue of the fact that a spring force is applied to the shaft axially against the union nut. 
     In order to connect the interior of the Bourdon spring to the environment, the shaft has an axial bore one of whose ends is connected to the environment and the other of whose ends is connected to the interior of the Bourdon spring. 
     If the union nut is constructed in a pot-shaped fashion and has a cover which covers the opening region, directed towards the environment, of the axial bore of the shaft, and in which one or more through bores of small cross section are constructed, the cover forms a support for the shaft. The through bores of small cross section prevent the ingress of contaminants. 
     The end of the shaft on the Bourdon spring end can be mounted with a transverse bore pivotably on a joint hollow screw, the axial bore of the shaft opening into an axial bore of the joint hollow screw, and the axial bore of the joint hollow screw, which is firmly connected to the Bourdon spring, opening into the Bourdon spring. The relative swivelings between the end of the Bourdon spring and shaft can be performed without stresses between these parts. 
     In order to permit the radial movement of the end of the Bourdon spring when the shaft is applied, the Bourdon spring can be fastened in the region of the joint hollow screw on one end of the pivoting arm whose other end can be pivoted about a pivoting axis which is arranged firmly on the watch case and extends parallel to the longitudinal axis of the joint hollow screw. 
     In order to be able to adjust the mechanical depth measurement mechanism and the depth hand in a simple way, the mechanical depth measurement mechanism can be arranged on the bottom side of the watch case, which is opposite the dial and can be closed by an openable case bottom. The depth measurement mechanism is thus accessible independently of the movement. 
     In this case, the display shaft preferably projects through the movement. 
     For the purpose of driving the depth measurement mechanism, the free end of the Bourdon spring can be pivotably connected via an articulated rod mechanism to a lever of a saw segment by means of which a drive pinion of the display shaft can be driven rotatably. In this case, the articulated rod mechanism is preferably pivoted with its one end at the free end of the Bourdon spring and with its other end at the free end of the saw segment lever. 
     In order to be able to compensate manufacturing tolerances in the Bourdon spring, the articulated rod mechanism can be set in a fashion varying its length. For this purpose, the connection of the articulated rod mechanism to the lever  26  of the saw segment is preferably guided displaceably and can be fixed in the longitudinal extent of the articulated rod mechanism. 
     In a simple way, it is possible in this case for the lever of the saw segment to have an elongated hole into which there project two guide pins which are arranged on the articulated rod mechanism at a smaller spacing from one another in the longitudinal extent of the articulated rod mechanism than the length of the elongated hole, it being possible for a fixing screw to be screwed in a fashion penetrating the elongated hole into a threaded hole in the lever of the saw segment, and to be pressed with its screw head on the lever of the saw segment against the articulated rod mechanism. 
     For the purpose of adjustment, a pin which is arranged such that it can rotate parallel to the guide pin on the lever of the saw segment and has an eccentric head can project into a bore in the articulated lever mechanism. 
     If a pivotably arranged spring-loaded resetting saw segment engages in the drive pinion and can be applied in order to move the drive pinion rotatably in the depth direction, the result is immediate resetting of the depth hand upon surfacing after a dive. At the same time, the saw segment remains with the flanks of its teeth always in the same direction of rotation bearing against the tooth flanks of the drive pinion, with the result that there is no tooth play to be overcome in the case of a reversal of the pivoting movement of the saw segment level upon resurfacing. This contributes to the accuracy of the depth display. 
     If the aim is also to display the maximum depth of a dive in a simple way, a non-return hand indicating the maximum depth of a dive can be driven pivotably in the depth direction by the pressure gauge or the depth measurement mechanism or the depth hand. Upon resurfacing, the non-return hand then remains in the position of the maximum dive depth reached. 
     It is possible in a simple way for the depth hand to have a driver by means of which the depth hand can strike against the non-return hand and the latter can be moved in the depth direction. A special drive for the non-return hand is therefore not required. 
     If the non-return hand can be driven pivotably about an axis coaxial with the rotation axis of the depth hand, it being the case that in a simple design the non-return hand is arranged on a non-return hand shaft or on a non-return hand tube surrounding the display shaft, the non-return hand and depth hand indicate their measured values on the same depth scale. 
     In order for the non-return hand to be able to return to its normal position after displaying a maximum depth, the pivoting movement of the non-return hand can be locked against the depth direction by a releasable latching device. In this case, in a simple design the pivoting movement of the non-return hand can be locked by a pawl-type lock. 
     The non-return hand shaft or the non-return hand tube can have a locking disk with a row of teeth which are arranged running around radially and in the tooth spaces of which a locking pawl can engage in a locking fashion against the depth direction. 
     For this purpose, it is possible, in a simple way, to construct the locking disk on its radially circumferential edge with a row of saw teeth of which the teeth are directed against the direction of rotation of the non-return hand toward depth. 
     For ease of movement of the locking pawl, the locking pawl can be pivotable about a pivoting axis. 
     In order to be able to reset the non-return hand the locking pawl can be acted upon manually in the unlocking direction, this being possible in a simple design by virtue of the fact that the locking pawl can be acted upon in the unlocking direction by an actuating slide which projects from the watch case with its one end such that it can be acted upon manually, or which can be acted upon manually by a pusher. The non-return hand can thus be reset in a simple and quick fashion. In order to define the position of the non-actuating locking slide, the unlocking slide can be spring-loaded against the direction in which the locking pawl can be acted upon. 
     If the non-return hand is resiliently biased against the depth direction with respect to the depth hand, it is automatically reset against as far as the stop on the depth hand after release of the latching device. In a simple way which saves overall space, it is possible, for this purpose, to provide that a biased spiral spring surrounding the display shaft is permanently arranged with its one end on the display shaft and with its other end on the non-return hand shaft or the non-return hand tube or the locking disk. 
     In order to prevent the locking pawl braking the locking disc, and thus to prevent a jerky movement of the non-return hand, in each case a locking pawl can be arranged at a spacing one from another in the circumferential direction of the locking disc on each lever arm of a two-arm lever which can be pivoted freely about a pivoting axis parallel to the axis of rotation of the locking disc, it being possible, upon rotation of the locking disc in the depth direction for the locking nose of one locking pawl to be moved, sliding along the tooth flank, out of a tooth space of the row of saw teeth and thereby for the two-arm lever to be pivoted in such a way that in the process the locking nose of the other locking pawl can be moved into a tooth space of the row of saw teeth. 
     For the purposes of decoupling the two locking pawls easily after a dive, the actuating slide can be displaceably guided approximately radially relative to the axis of rotation of the locking disc and can carry the pivoting axis of the two-arm lever. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Exemplary embodiments of the invention are represented in the drawings and are described in more detail below. 
     FIG. 1 shows a plan view of a dive watch, 
     FIG. 2 shows a cross section through the dive watch according to FIG. 1, 
     FIG. 3 shows a side view of the movement of the dive watch according to FIG. 1, with a depth measuring mechanism, in cross section, 
     FIG. 4 shows a plan view of the depth measurement mechanism according to FIG. 3, 
     FIG. 5 shows the depth measurement mechanism according to FIG. 4 without annular spring pressure gauge, in an exploded representation, 
     FIG. 6 shows the subassembly of the display shaft of the depth measurement mechanism according to FIG. 5, 
     FIG. 7 shows a partial cross section through the dive watch according to FIG. 1 in the region of the screwed crown in the closed position thereof, 
     FIG. 8 shows the partial cross section according to FIG. 7 in the open position of the screwed crown, 
     FIG. 9 shows a partial cross section through the dive watch according to FIG. 1 in the region of a pusher crown, 
     FIG. 10 shows a partial cross section through a further exemplary embodiment of a dive watch in the region of a crown, in the position for ambient pressure, 
     FIG. 11 shows the crown according to FIG. 10, in the position for applying pressure, and 
     FIG. 12 shows the crown according to FIG. 10, in the position for manual actuation, 
     FIG. 13 shows a further exemplary embodiment of an articulated rod mechanism of the dive watch according to FIG. 1, 
     FIG. 14 shows a perspective view of a further exemplary embodiment of a depth measuring mechanism of a dive watch according to FIG. 1, 
     FIG. 15 shows a view of a section of the depth measuring mechanism according to FIG. 14 in the region of the locking pawls of the locking disc, 
     FIG. 16 shows a cross section of a crown for applying ambient pressure to a Bourdon spring for a dive watch according to FIG. 1, 
     FIG. 17 shows a view of the crown connected to an end of the Bourdon spring and according to FIG. 16, 
     FIG. 18 shows a perspective view of the crown and Bourdon spring according to FIG. 16, and 
     FIG. 19 shows a plan view of the crown and Bourdon spring according to FIG. 16 in a watch case. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The dive watch represented in the figures has a dial  1  with an annular hour and minute scale  2 , which is assigned an hour hand  3  and a minute hand  4 . The hour and minute scale  2  is surrounded by a rotatably settable dive time setting ring  8  which can be set by a pusher crown  9 . The dive time setting ring  8  is surrounded in turn by a depth scale  5  which is assigned a depth hand  6  and a non-return hand  7 . 
     The scale divisions of the hour and minute scale  2  and the depth scale  5  correspond to one another, the depth scale  5  extending from the 12 o&#39;clock position up to the 9 o&#39;clock position. 
     The pusher crown  9  also serves to trigger a resetting movement of the non-return hand  7 , and a screwed crown  11  is present for applying pressure to a pressure transducer. A screwed crown  10  serves to set the time hands and for manually winding the automatic movement. 
     The dive watch is represented in cross section in FIG. 2, the watch case  12  being closed on the observer side by a cover glass  13 , and on the bottom side by a case bottom  14  which can be screwed in. The watch case  12  is provided with a pot-like opening  15  in which a movement  16  for driving the time hands of the watch is arranged. A depth measurement mechanism  17  (not represented in this figure) can be arranged below the movement  16  in the free space on the bottom side. 
     The pot-shaped opening  15  is surrounded by an annular chamber  18  of the watch case  12 , in which a Bourdon spring  19  of an annular spring pressure gauge is arranged such that it can move radially. The side walls  20  and  21  of the annular chamber  18  form stops for limiting the radial deflection of the Bourdon spring  19 . The crown  10  represented in section serves to set the time hands via the movement  16 . 
     The movement  16  and the depth measurement mechanism  17  are arranged above one another in mounting position in FIG. 3, the depth measurement mechanism  17  being represented in section. It is to be seen in this case that a display shaft  22  and a non-return hand tube  23 , surrounding the display shaft  22 , of the depth measurement mechanism  17  are guided through the movement  16 . 
     As is also to be gathered from the further FIGS. 4 to  6 , there is arranged on the lower end of the display shaft  22  a drive pinion  24  in which a saw segment  25  engages. The saw segment  25  has a lever  26  which is mounted at its end opposite the saw segment  25  such that it can pivot about a pivoting axis  27 . Pivoted with its one end at the saw segment lever  25 , which is constructed in two parts, is an articulated rod mechanism  28 , while with its other end it is pivoted at the free end of the Bourdon spring  19 . 
     This Bourdon spring  19  closed at its free end is fastened with its other end on the watch case  12  and connected via a connecting opening  29  to a measuring opening  30  via which the Bourdon spring  19  can be connected to the ambient pressure outside the watch case  12 . The Bourdon spring  19  can change its curvature in accordance with this ambient pressure, and this is shown in FIG. 4 by representing the Bourdon spring  19  with a continuous and a broken line. When the ambient pressure rises, the curvature of the Bourdon spring  19  expands and, via the articulated rod mechanism  28 , swivels the saw segment  25  about the pivoting axis  27 . Via the drive pinion  24 , this rotates the display shaft  22 , and thus swivels the depth hand  6  (not represented) arranged on the upper end of the display shaft  22 . The depth hand  6  thus indicates the instantaneous dive depth on the depth scale  5 . 
     A resetting saw segment  32  which can pivot about a pivoting axis  31  likewise engages in the drive pinion  24 . The drive pinion  24  is acted upon in the depth direction by means of a resetting spring  33  applied to the resetting saw segment  32 , with the result that when the ambient pressure drops through surfacing, the drive pinion  24 , and thus the depth hand  6  are swiveled to the start of the depth scale  5 . Furthermore, the resetting spring  33  and the resetting segment  32  ensure that the saw segment  25  always bears in the same direction against the teeth of the drive pinion  24 , and therefore no backlash is produced. 
     As is to be seen in FIG. 2, the depth hand  6  has a driver  34 , which is constructed as a stop and which, when the depth hand  6  moves in the depth direction  35 , that is to say in the direction of greater dive depth, bears against the non-return hand  7  and drives the latter in the depth direction  35 . In the inverse direction of movement of the depth hand  6 , the non-return hand  7  remains in its position of maximum depth, into which it has been moved by the depth hand  6 . The non-return hand  7  thus shows the maximum depth of a dive. The non-return hand  7  is arranged on the non-return hand tube  23 , which surrounds the display shaft  22  and likewise projects through the movement  16 . 
     On the end opposite the non-return hand  7 , the non-return hand tube  23  has a circular locking disk  36  which is provided on its radially circumferential edge with a row of saw teeth  37 . The radially directed teeth of the row of saw teeth  37  are directed against the direction of rotation of the non-return hand  7  toward depth. It is possible to latch into the spaces of the teeth of the row of saw teeth  37  a locking pawl  38  which can be pivoted about a pivoting axis  39  parallel to the non-return hand tube  23 , and can be applied with its latching nose  41  against the row of saw teeth  37  by a spring arm  40  which is constructed in one piece with the locking pawl  38  and is supported in a biased fashion on a subassembly fixed to the case. 
     As a result, the non-return hand  7  can be swiveled unimpeded in the depth direction  35  together with the depth hand  6 . If the depth hand  6  then moves back again, the non-return hand  7  is held in its position by the locking pawl  38 , which has latched in a tooth space of the row of saw teeth  34  and locks a return movement of the non-return hand  7 . 
     However, a manually actuable unlocking device is present in order also to permit the non-return hand  7  to be reset. This device comprises an actuating slide  42  which is guided such that it can be displaced radially relative to the non-return hand tube  35  and it is possible for its one end  42  to act on the locking pawl  38  to pivot in such a way that the latter raises its locking nose  41  out of the row of saw teeth  37 . The actuating slide  42  has two grooves  44  which extend in the direction of movement and into which permanently arranged guide pins  45  project. This provides the radial guidance of the actuating slide  42 . 
     In the normal position, in which the actuating slide  42  is out of engagement with the locking pawl  38 , the actuating slide  42  is biased by a biased spring arm  46  which is constructed in one piece with the actuating slide  42  and is supported on a subassembly fixed to the case. 
     The end, opposite the locking pawl  38 , of the actuating slide  42  can be acted upon displaceably through the pusher shaft  47  of the pusher crown  9  represented in FIG.  9 . 
     In order for the non-return hand  7  also to move against the depth direction when the locking disk  36  is unlocked, an adequately biased spiral spring  48  is present, which surrounds the display shaft  22  and is fastened with its inner end on the display shaft  22 , and with its outer end on the locking disk  36 . 
     As is to be seen in FIGS. 4,  7  and  8 , the Bourdon spring  19  has at its end fastened on the watch case  12  a holding part  49  by means of which it is fastened on the watch case  12 . Via the disgorging opening of the Bourdon spring  19 , the interior thereof is connected to the connecting opening  29 , which disgorges radially outward, of the holding part  49 , which leads, in turn, to the measuring opening  30  of the screwed crown  11 . 
     The screwed crown  11  is represented in the closed position in FIG. 7, and in the open position in FIG.  8 . Inserted tightly in a radially penetrating case opening  50  is a guide shaft  51  which projects radially outward and is provided with the axially penetrating measuring opening  30 . In this arrangement, the outer lateral surface, which runs around radially, the guide shaft  51  forms a sliding surface on which a sealing ring  52  surrounding the guide shaft  51  is seated such that it can be displaced both axially and in the circumferential direction. 
     The sealing ring  52  is seated with its radially external region in an annular groove  53  of a crown head  54  which reaches over the guide shaft  51  in the fashion of a pot. The crown head  54  has a center pin  55  which projects into the measuring opening  30 . An annular gap  56  is formed in the free end region of the pin  55  between the pin  55  and the wall of the measuring opening  30 , while at the free end region of the guide shaft  51  the measuring opening  30  is provided with an internal thread  57  into which the pin  55  can be screwed with an external thread  58  in the region closer to the crown head  54 . By rotating the crown head  54 , the pin  55  thereof is screwed further into the measuring opening, or screwed further out of the measuring opening  30 . In this case, the sealing ring  52  changes position axially from a position close to the case to a position remote from the case. 
     Constructed in the guide shaft  51  between these two positions are radially penetrating ventilation openings  59  via which the measuring opening  30  can be connected to the external environmental region when the sealing ring  52  is in its position remote from the case. If it is located in its position close to the case, it shuts off the connection of the measuring opening  30  with the external environmental region. 
     The pin  55  is provided with a base bore  60  which is open toward the interior of the case and in which a stop slide  61  is arranged in an axially displaceable fashion. On its one end projecting into the connecting opening  29 , the stop slide  60  has a radial extension  62  which is larger than the cross section of the measuring opening  30 . Since the capacity of the stop slide  61  to move axially in the base bore  60  is limited by stops  63 , in the case of a movement to screw on the crown head  54  the radial extension  62  strikes against the internal disgorging region of the measuring opening  30 , the result being to limit the screwing-on movement of the crown head  54 . 
     In order for the stop slide  61  normally to be located in its furthest extended position and not inadvertently to close the measuring opening with the radial extension, a biased compression spring  64  supported on the bottom of the base bore  60  acts on the stop slide  61  in the direction toward the interior of the watch case  12 . 
     As already stated, the pusher crown  9  represented in FIG. 9 serves both as a crown for adjusting the dive time setting ring  8  and as a pusher for acting on the actuating slide  42  to act on the locking pawl  38 . Inserted tightly for this purpose in a radially penetrating case opening  65  is a guide shaft  66  in which an actuating pin  67  is arranged to be guided such that it can both move axially and rotate. Arranged on its outwardly directed end on the actuating pin  67  is a crown head  68  on which there is supported a compression spring  73  which surrounds the actuating pin  67  and is supported with its other end on a step  69  in the case opening  65 . The actuating pin  67  is thereby always biased to be moved into its radially external position. By manually pressing on the crown head  68 , the latter moves the actuating pin  67  into the watch case  12  until the actuating pin  67  acts with its end face  70  on the actuating slide  42 , and the latter swivels the locking pawl  38  in the releasing direction. 
     Furthermore, there is arranged on that end of the actuating pin  67  which projects into the watch case  12  a positioning pinion  71  which engages in a row of teeth  72  which extends along the drive time setting ring  8  on the underside thereof in the circumferential direction of the drive time setting ring  8 . The setting position of the drive time setting ring  8  is varied by rotating the crown head  68 , and thus the actuating pin  67  and the positioning pinion  71 . 
     In the exemplary embodiment of FIGS. 10-12, the watch case  12 , the movement, the depth measurement mechanism and the annular spring pressure gauge have the same design as in the case of the exemplary embodiment of FIGS. 1-9, and are therefore partially not represented. 
     Instead of the screwed crown  11  in the exemplary embodiment of FIGS. 1-9, in the case of the exemplary embodiment of FIGS. 10-12 there is inserted into the case opening  50  a crown  74  which likewise has a measuring opening  30 . 
     The measuring opening  30  leads from the interior of the Bourdon spring  19  to a chamber  75 , which is constructed in the head of the crown  74  and is of larger diameter than the measuring opening  30 . The wall of the chamber  75  opposite where the measuring opening  30  disgorges is a movable wall which is constructed as a diaphragm  76  and to whose side averted from the interior of the chamber  75  it is possible to apply the ambient pressure via ventilation bores  77  in the crown  74  and in a pusher  78  guided displaceably in the crown  74 . 
     The pusher  78  is guided displaceably in a guide bore  79 , coaxial with the measuring opening  30 , of the crown  74 , its capacity to be displaced in the direction in which the volume of the chamber  75  is increased being limited by a stop  80  on the crown  74 . 
     The shaft  81  of the pusher  78 , which projects into the guide bore  79 , can be acted upon manually on its outwardly directed end face, and can be displaced in the direction reducing the volume of the chamber  75 . 
     On its end facing the chamber  75 , the pusher  78  is provided with a mushroom head  82  against which the diaphragm  76  can bear and be supported, and via which the diaphragm  76  can be deflected in the direction reducing the volume of the chamber  75  when the pusher  78  is acted upon manually. 
     The interior of the Bourdon spring  19 , the measuring opening  30  and the chamber  75  are filled with an oil in a fashion free from bubbles. 
     When standard ambient pressure is applied to the outside of the diaphragm  76  via the ventilation bores  79 , the diaphragm  76  is located in the position represented in FIG.  10 . 
     If the pressure acting on the diaphragm  76  from outside rises during a dive, this raised pressure is transmitted via the diaphragm onto the oil which is located in the chamber  75  of the measuring opening  30  and the interior of the Bourdon spring  19  and which in turn expands the curvature of the Bourdon spring  19 . 
     The curvature of the Bourdon spring  19  expands to a greater or lesser extent depending on the level at which pressure is applied to the diaphragm  76 , and leads via the depth measurement mechanism  17  to the appropriate setting of the depth hand  6 . 
     Since in the case when the Bourdon spring  19  expands the volume of its interior is increased, the diaphragm  76  moves from the position represented in FIG. 10 as far, at most, as the position represented in FIG. 11, in which it comes to bear against the bottom  83  of the chamber  75  and cannot be further deflected and damaged even in the case of a further rise in pressure. 
     Consequently, the reduction in the volume of the chamber  75  constitutes equalization of the volume for the enlargement of the volume of the interior of the Bourdon spring  19 . 
     In order to be able under standard ambient pressure to simulate application of pressure to the diaphragm  76  and thus the Bourdon spring  19 , it is possible by manually actuating the pusher  78  likewise to move the diaphragm  76  in the direction in which the volume of the chamber  75  is reduced, and to display a pressure value of the depth hand  6  in accordance with the force applied. 
     In the case of the exemplary embodiment of the articulated rod mechanism  28  as represented in FIGS. 4 and 5, it is necessary for the active length of the swan neck region thereof to be varied by bending, in order to compensate manufacturing tolerances in the Bourdon spring  19 . This is very expensive and imprecise. 
     In the case of the exemplary embodiment of the articulated rod mechanism  28 ′ represented in FIG. 13, said mechanism is constructed with a variable length by virtue of the fact that its connection to the lever  26  of the saw segment is guided displaceably and can be fixed in the longitudinal extent of the articulated rod mechanism  28 ′. For this purpose, the lever  26  of the saw segment has an elongated hole  84  into which there project two guide pins  85  which are arranged on the articulated rod mechanism  28 ′ at a smaller spacing from one another in the longitudinal extent of the articulated rod mechanism  28 ′ than the length of the elongated hole  84 . A threaded bore is constructed in the articulated rod mechanism  28 ′ between the two guide pins  85 . A fixing screw  86  projects with its shaft through the elongated hole  84 , and is screwed into the threaded bore. With its screw head  87 , it rests on the lever  26  of the saw segment in the edge region of the elongated hole  84  and clamps said lever against the articulated rod mechanism  28 ′. 
     In order to adjust the length of the articulated rod mechanism  28 ′, the fixing screw  86  is loosened so that the articulated rod mechanism  28 ′ can be led through the guide pins  85  projecting into the elongated hole  84 , can be displaced relative to the lever  26  of the saw segment, and can be fixed by subsequently screwing the fixing screw  86  tight. 
     The relative displacement is performed in this case by means of a pin which can be rotated parallel to the guide pins  85 , is arranged on the articulated rod mechanism  28 ′ and projects with an eccentric head  88  into a bore  89  of the lever  26  of the saw segment. The rotation of the eccentric head  88 , provided with a slot for a screwdriver, in the bore  89  effects a fine displacement of the lever  26  of the saw segment relative to the articulated rod mechanism  28 ′. 
     This construction of the articulated rod mechanism  28 ′ is also to be seen in the exemplary embodiment, represented in FIG. 14, of a depth measuring mechanism which corresponds largely to the depth measuring mechanism of FIGS. 4 and 5. The only difference is the construction of the locking pawl and the application to it of the actuating slide  42 ′. 
     In FIG. 14, the actuating slide  42 ′ largely surrounds the locking disc  36  with an arm  90 . Situated approximately diagonally opposite the actuating part of the actuating slide  42 ′, there is arranged on the arm  90  a pivoting axis  91  which is parallel to the axis of rotation of the locking disc  36  and on which a two-arm lever  92  is mounted such that it can pivot freely. Arranged on the free ends of each lever arm  93  of the lever  92  is a locking nose  41 ′ of a locking pawl  38 ′, of which in the normal position, represented in FIGS. 14 and 15, of the actuating slide  42 ′ a locking pawl  38  is always located in a tooth space  94  of the row  37  of saw teeth of the locking disc  36 . By rotating the locking disc  36  in the depth direction  35  during a dive, the locking nose  41 ′ of the locking pawl  38 ′ located in the tooth space  94  slides along the long tooth flank of a saw tooth and is thus moved out of the tooth space  94 . This effects swiveling of the lever  92 , and thus moves the other locking pawl  38 ′ into a tooth space  94 . As a result, one of the locking pawls  38 ′ is always located in one of the tooth spaces  94  and upon surfacing prevents the locking disc  36  and the non-return hand  7  from being turned back. After a dive, the diver can therefore read off at leisure the maximum dive depth he has previously reached. If, after reading off the maximum dive depth, the diver wishes to zero the non-return hand  7  again, he need only apply the actuating slide  42 ′ against the force of the spring arm  46  in the direction of the locking disc  36 . As a result, however, the arm  90  is displaced, and thus also the pivoting axis  91  and the lever  92  so far from the locking disc  36  that the two locking pawls  38 ′ are moved out of the tooth spaces  94  of the locking disc  36 . The spiral spring  48  can then reset the non-return hand  7  to the zero position without hindrance. 
     The crown represented in FIG. 16 has a crown bush  95  which is arranged firmly in the watch case  12  and projects away upward radially therefrom. Arranged in an axially displaceable fashion in the through bore of the crown bus  95  is a shaft  96  which is sealed by a sealing ring  120  and whose end projecting into the watch case  12  has a transverse bore  97 . A joint hollow screw  98  is sealingly inserted with its upper end in the transverse bore  97  via sealing rings  119  in such a way that the shaft  96  can pivot on the joint hollow screw  98 . The joint hollow screw  98  is screwed with its lower end into a threaded bore  99  of an end piece  100  of the Bourdon spring  19 . 
     The continuous axial bore  102  of the shaft  96  is connected to the interior of the Bourdon spring  19  via passage  101  in the joint hollow screw  98 . 
     The axial bore  102  of the shaft  96  is widened in a stepped fashion at the end averted from the watch case  12 , and holds a sliding bush  103 . On the end projecting out of the axial bore  102  widened in a stepped fashion, the sliding bush  103  has a flange-like extension  104  which is, in turn, supported axially on a cover  105  of a union nut  106  constructed like a pot. 
     Since the cover  105  has a plurality of through bores  107  of small diameter, and the sliding bush  103  likewise has an axial bore  108 , it is possible during a dive for ambient pressure to be applied to the liquid located in the Bourdon spring  19  via the through bores  107 , the axial bores  108  and  102  and the passage  101  in the joint hollow screw  98 . However, contaminants are largely prevented from entering the axial bores  108  and  102  and the Bourdon spring  19  by the small cross section of the through bores  107 . 
     The union nut  106  is of bipartite construction, the hollow cylindrical part  109  adjoining the cover  105  having an internal thread  110 , one end of which screws the hollow cylindrical part  109  onto an external thread  111  of the cover  105 . A sealing ring  121  is arranged in the connecting region between the cover  105  and the hollow cylindrical part  109 . 
     At the other end, the hollow cylindrical part  109  is screwed with its internal thread  110  onto an external thread  112  on a flange-like extension  113  of the crown bush  95 . 
     The internal thread  110  and the external threads  111  and  112  are fine threads. 
     By rotating the union nut  106  on the external thread of the crown bush  95 , the shaft  96  can be set in an axially displaceable fashion in the crown bush  95  via the cover  105  and the sliding bush  103 . However, the end piece  100  of the Bourdon spring  19  can also be adjusted radially relative to the watch case  12 . 
     However, this adjustment also varies the position of the other end of the Bourdon spring  19 , which is connected to the depth measurement mechanism, and thus also the position of the depth hand  6 . 
     The position of the depth hand  6  is therefore dependent on the position of the end piece  100  of the Bourdon spring  19 . If the curvature of the Bourdon spring  19  varies owing to changes in atmospheric pressure, the depth hand  6  moves slightly from its zero position either above or below zero. This error would be retained during a dive. The depth hand can be adjusted to exactly zero directly before a dive by rotating the union nut  106 , thus avoiding an erroneous display during the dive. 
     Present between the flange-like extension  113 , the crown bush  65  and the shaft  96  is an annular chamber  114  in which there is arranged a helical spring  115  which surrounds the shaft  96  and is supported with one of its ends on the crown bush  95  and with its other end on a flange-like extension  116  of the shaft  96  and holds the latter bearing against the cover  105  of the union nut. 
     As a result, the flanks of the internal thread  110  of the hollow cylindrical part of the union nut  106  are always held in one direction bearing against the flanks of the external threads  111  and  112 , the result being that no thread play can falsify the accuracy of the display of the depth hand  6 . 
     The free end of the hollow cylindrical part  109  grips the flange-like extension  113  of the crown bush  95  from behind and thus forms in one direction an axial limitation of the screwing movement of the union nut  106 . Furthermore, a sealing ring  122  is arranged between this end of the hollow cylindrical part  109  and the crown bush  95 . 
     The adjustment path required for the shaft  96  and the end piece  100  of the Bourdon spring  19  is 0.3 mm in the case of the original of the exemplary embodiment represented in an enlarged fashion, and this produces a hand adjustment corresponding to a water depth of 20 m. 
     The articulated connection of the shaft  96  to the joint hollow screw  98  eliminates distortions between these two parts during a setting operation and a measuring operation. 
     In order to ensure that the end piece  100  of the Bourdon spring  19  can be adjusted radially in a fashion moving as easily as possible when adjusting by means of the shaft  96 , the end piece is fastened on one end of a pivoting arm  117  whose other end can be pivoted about a pivoting axis  118  arranged firmly on the watch case  12  and extending parallel to the longitudinal axis of the joint hollow screw  98 . This permits the end piece  100  of the Bourdon spring  19  to be moved in a largely radial fashion in the watch case  12 .