Abstract:
A clock movement having a moon dial that includes symmetric teeth about its periphery. The movement also includes a driving gear with a pin that engages the teeth so that each rotation of the drive gear advances the moon disk. Because the moon dial teeth are symmetric, the moon dial can be rotated either forward or backward by moving the driving gear either forward or backward. The rotational support of the moon dial includes a wave washer to apply a small frictional force to prevent freewheeling.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to clock movements, and more particularly to clock movements including moon dials.  
         [0002]     An example of the structure of a conventional clock movement with a moon dial is shown in  FIG. 2  and generally designated  100 . The moon dial is a disk  114  that has a saw-toothed periphery  116  with each tooth angled in the same direction. The visible face of the moon dial (not shown) includes two moons that show the different phases of the moon as the dial rotates. The moon dial  114  is driven by a gear  118  that is driven by the movement through a series of other gears  122 . The drive gear  118  makes one revolution every twenty-four hours. A pin  120  extends from the underside of the drive gear  118 , and the pin  120  engages the saw teeth  116  to drive the moon dial  114  one step or tooth for each revolution of the drive gear  118  (i.e. one tooth per day). A click spring  140  engages the saw-teeth  116  of the moon disk  114  in a ratchet arrangement. The spring provides pressure to prevent the disk  114  from freewheeling and to prevent the disk  114  from rotating backward. The click spring  140  also advances the disk  114  beyond the capability of the drive gear  118  and pin  120 .  
         [0003]     In the above-described clock  110 , proper alignment of the pin  120 , the saw teeth  116 , and the click spring  140  is essential for proper operation. If a saw tooth  116  is out of position when the pin  120  rotates to engage it, the pin  120  and gear  118  may not provide an adequate force to properly advance the moon dial disk  114 . If the click spring  140  applies excessive force on the moon dial disk  114 , the click spring  140  may prevent the moon disk  114  from moving and, in severe cases, may halt the entire clock movement. If the click spring  140  is not properly adjusted to advance the disk  114  when driven by the drive gear  118  and pin  120 , it may also prevent the moon disk  114  from moving and, in severe cases, may halt the entire clock movement.  
       SUMMARY OF THE INVENTION  
       [0004]     The aforementioned problems are overcome by the present invention providing a moon dial that can move both forward and backward, having a simplified construction, and having a reliable performance without synchronized fine adjustment of the moon dial, drive gear, pin, and click spring. In particular, the moon disk includes teeth having a generally symmetric profile so that the drive gear can move the moon disk forward or backward with each rotation of the drive gear.  
         [0005]     In a specific embodiment, a rotational friction device is used in mounting the moon disk on the movement to prevent freewheeling of the disk. As disclosed, the friction device is a wave washer that applies consistent but small amount of friction to the moon disk to prevent over-rotation or freewheeling while still allowing the moon disk to be easily rotated.  
         [0006]     The present invention has several advantages. First, the click spring of the prior art is eliminated, along with its aforementioned problems. Second, the moon dial can be set by rotating the hands of the clock either forward or backward. Third, since it is no longer necessary to properly synchronize and adjust multiple components to function harmoniously, it is significantly less likely that the moon dial feature will prevent the moon disk from moving or halt the entire clock movement.  
         [0007]     These and other objects, advantages, and features of the invention will be more readily understood and appreciated by reference to the detailed description of the preferred embodiment and the drawings.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  is a front view of a clock having a movement in accordance with the present invention.  
         [0009]      FIG. 2  is a rear view of a prior art moon dial clock movement.  
         [0010]      FIG. 3  is a rear view of the clock dial of the present invention.  
         [0011]      FIG. 4  is an enlarged rear view of the present invention.  
         [0012]      FIG. 5  is a cross sectional view along line  5  in  FIG. 4 .  
         [0013]      FIG. 6  is a cross sectional view along line  6  in  FIG. 3 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0014]     A clock dial including a moon dial mechanism in accordance with the preferred embodiment is shown in  FIG. 1  and generally designated  10 . The clock  10  generally includes conventional face  12  and a separate moon dial disk  14 . Only a portion of the moon dial disk  14  is visible from a front view of the clock dial  10 . As shown in  FIG. 3 , the moon dial disk  14  generally has a plurality of teeth  16  about the periphery, and a drive gear  18  that includes a pin  20  to engage the teeth  16 . The drive gear  18  is integrated with a series of gears  22  such as those in a generally conventional clock dial, such that the drive gear  18  rotates once per twenty-four hour period.  
         [0015]     As shown in  FIGS. 1 and 3 , the clock dial is generally conventional. In the preferred embodiment, the clock dial  10  is adapted to be fit into a housing, such as a grandfather clock or the like. The clock dial  10  is shown in this configuration for purposes of description, but may also be sized or adapted for a variety of alternative arrangements. The clock dial  10  generally includes a face  12  with an hour hand  24  and a minute hand  26 . The hands  24  and  26  are rotatable about an axis  28 , and driven by conventional clock means. The axis  28  is linked, either directly or indirectly through conventional drive means, to a series of gears  22  including a drive gear  18  that engages the moon disk  14 . As shown in  FIG. 4 , in a preferred embodiment, the series of gears  22  includes a first gear  15  in direct communication with a gear on the axis  28 , a second gear  17  in communication with the first gear  15 , and a drive gear  18  in communication with second gear  17 . The gears  22  preferably have the same ratio and are driven such that they each make one revolution every twenty-four hour period.  
         [0016]     The drive gear  18  is generally a standard gear, rotatable about an axis  19  parallel to the clock dial axis  28 . The drive gear  18  also includes a pin  20  that engages the moon disk  14 . The pin  20 , shown in  FIG. 5 , preferably protrudes from the drive gear  18  in a direction perpendicular to the gear  18  and parallel with the axis  19 , extending into the clock dial  10  towards the moon dial  14 . The gear  18  is located relative to the moon disk  14  such that the pin  20  engages the teeth  16  of the moon disk  14  once for every revolution of the drive gear  18 . The moon dial disk  14  is therefore incremented one tooth per day.  
         [0017]     As shown in  FIG. 3 , the moon dial disk  14  is generally a circular metal sheet that is capable of rotation about an axis  26 . As seen in  FIG. 1 , the disk  14  includes a display  11  on one surface  13  of the moon dial disk  14 . The display  11  generally includes two depictions of the moon  21  (only one is shown) on opposing sides of the same surface  13  of the moon dial disk  14 . Approximately one-half of the display  11  is visible from a front view of the clock dial  10 , the other half covered behind the clock face  12  and a pair of semi-circular hemisphere projections  23  and  25  extending from the face  12 . As the moon dial disk  14  rotates clockwise, a portion of one of the moons  21  becomes visible behind semi-circular projection  23  representing a waxing moon. Further rotation brings the moon  21  into full view (a full moon), until a portion of the moon  21  is covered by the second semi-circular projection  25 , representing a waning moon.  
         [0018]     Referring now to  FIGS. 4 and 5 , the moon dial disk  14  includes a plurality of teeth  16  about the periphery. The teeth  16  preferably have a symmetric tooth profile, and are spaced such that pin  20  engages one tooth  16  for each revolution of the drive gear  18 . One revolution of the drive gear  18  in either direction increments the moon disk  14  one tooth  16 . The most preferred tooth profile is shown in the enlarged view of the moon dial disk  14  in  FIG. 4 . In this preferred tooth profile each tooth  16  has a symmetrical “V” shape, and adjacent teeth are joined by a semi-circular notch  29 .  
         [0019]     Referring now to  FIG. 6 , the axis  26  also includes a wave washer  30 . The washer  30  is preferably disposed about axis  26  and held in consistent friction with the moon dial disk  14  by a conventional bushing method. The washer  30  preferably has a curved or convex shape such that when held between the bushing  33  on disk  14  and a post  32  the washer can flex slightly to provide a constant pressure to the disk  14  without binding the rotation of the disk  14 . The washer  30  is shown in  FIG. 6  such that the convex side faces the disk  14 , but can be oriented in either direction so long as consistent friction is applied to the moon dial disk  14 .  
         [0020]     The above description is that of a preferred embodiment of the invention. Various alterations and changes can be made without departing from the spirit and broader aspects of the invention as defined in the appended claims, which are to be interpreted in accordance with the principles of patent law including the doctrine of equivalents. Any reference to claim elements in the singular, for example, using the articles “a,” “an,” “the” or “said,” is not to be construed as limiting the element to the singular.