Abstract:
The invention relates to a clock, especially a wall clock or a grandfather clock. Said clock comprises a drive element (weight  12 ) and a brake element (liquid  23 ). The braking action of the brake element is based on a hydrostatic fall of at least one free-flowing medium, creating a clock which works according to a physical principle a typical for a clock. Said principle can preferably be easily recognised from the outside.

Description:
REFERENCE TO RELATED APPLICATIONS  
         [0001]    The present application claims priority of the German Utility Model Application 200 18 537.3, filed on 28.10.2000, the disclosure content of which is herewith also made the subject of the present application.  
         DESCRIPTION  
         [0002]    1. Field of the Invention  
           [0003]    The invention relates to a clock, in particular a wall or hall clock according to the preamble of claim 1.  
           [0004]    2. Prior Art  
           [0005]    Traditionally, wall or hall clocks have not only the purpose of informing the observer of the current time, but frequently also serve as decorative pieces or ornaments. The charm of many such clocks is based on the feature that they allow observers a view of their internal workings, which generally comprise complex mechanics with numerous gears, springs etc.  
         SUMMARY OF THE INVENTION  
         [0006]    The object of the present invention is to provide a clock, which operates according to a physical principle that is a typical for a clock. This principle should preferably be clearly visible from the outside.  
           [0007]    This object is achieved with a clock with the features of claim 1.  
           [0008]    As is ultimately the case with every mechanical clock, this clock has a driving element and a braking element. The braking element works according to the principle of a hydrostatic gradient. The braking action, i.e. the dissipation of the energy provided by the driving element, is effected by the flow resistance of the medium with the hydrostatic gradient.  
           [0009]    Further advantageous configurations of the invention may be seen from the sub-claims. 
       
    
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0010]    [0010]FIG. 1 is a top view onto the entire clock, but without the case and clock face;  
         [0011]    [0011]FIG. 2 shows a section taken along line H-H in FIG. 1;  
         [0012]    [0012]FIG. 3 is a top view in partial section onto a braking element;  
         [0013]    [0013]FIG. 4 is a top view onto a further braking element. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0014]    The invention will now be explained in more detail with reference to the attached drawings by way of example. However, the embodiments only constitute examples which are not intended to limit the inventive concept to a specific arrangement.  
         [0015]    The drive wheel  15  is rigidly disposed on the first shaft  10 , which extends coaxially to the axis A-A. The shaft  10  is rotatably held by the two bearings  10 A (FIG. 2). The bearings  10 A are themselves disposed in a case, which also supports the clock face, for example. The case and clock face are not shown in the figures for reasons of clarity. A cable  14  lies over the drive wheel  15  and has the two different weights  11 ,  12  disposed at its ends. As a result of the difference in the two weights, a vertical force F 1  is exerted onto the drive wheel  15  and from this force a first torque M 1  results (see also FIG. 2). Two circular rails  18 , which are concentric relative to the first shaft  10 , are disposed on the first shaft  10  by means of connecting struts  17 . Only the cut faces of the rails  18  with the plane of projection are shown in FIG. 2. The first shaft  10  also supports the hour hand S. As already mentioned above, the associated clock face is not shown for reasons of clarity.  
         [0016]    The cylindrical drum  20  has a second shaft  22  that is concentric relative to the axis of symmetry B-B of this drum. At the two ends of the second shaft  22  a running wheel  25  is respectively disposed having a running surface  25 A with a surface made of a non-slip material, e.g. rubber. Each of the running surfaces  25  lies on one of the rails  18 , so that the drum  20  is partially located between the rails  18 . Because of the friction between the rails  18  and the running surfaces  25 A, the first shaft  10  and the second shaft  22  are coupled with respect to their rotation. Because of its weight F 2 , the drum  20  exerts a second torque on the first shaft  10 . At equilibrium, the first and second torques are equal, but are directed in opposite directions.  
         [0017]    If the drum  20  contained no moveable medium, then a static equilibrium would occur. However, this is not possible here. The drum  20  is divided into six compartments  27 . These compartments  27  each have a segment-shaped area and are separated from one another by means of compartment walls  28 . A hole  28 A is located in each of the compartment walls  28 , see FIG. 2, so that respectively adjacent compartments  27  are interconnected. In addition, each compartment wall  28  has an opening  28 C close to the axis to equalize air pressure. This is also shown in FIG. 2.  
         [0018]    The drum  20  is partially filled with a liquid, e.g. water. Since the second shaft  22  is located at a point of the rails  18  where their tangent does not run horizontally, a torque acts on the second shaft  22  because of the weight of the drum or of the water located in the drum. This causes the compartments located on the left side to be raised as a result of a rotation of the drum until an equilibrium of forces or a torque balance results in turn from the different water levels inside the compartments. Because of the differences in levels, water flows out of the compartments in which the water level is higher, into those in which the water level is lower. The different water levels are indicated in FIG. 1 by means of shaded areas with the reference numeral  23 .  
         [0019]    The driving element exerts a first torque on a shaft, which can support the hour hand, for example. This driving element can act gravitationally, for example. A braking element opposes the torque generated by the driving element. The equilibrium between the driving and braking elements is responsible for the speed and therefore the precision of the clock. The braking element is formed by the drum  20 , which is partially filled with liquid and is disposed to rotate around a second shaft  22 . The drum is coupled to the first shaft with respect to its rotational movement. The braking action results from the flow resistance of the liquid inside the drum. Coupling of the rotational movements only occurs indirectly. The braking torque opposed to the driving torque is generated gravitationally.  
         [0020]    The speed of these flow movements is determined by the size of the holes  28   a  and the viscosity of the water. As a result of these flow movements, the drum  20  and therefore the rails  18  or the first shaft  10  rotate. The flow resistance of the water acts as a brake in this case.  
         [0021]    The fine adjustment of the operating speed of the clock is achieved by means of adjusting wheels  26  (see FIG. 2). The running surfaces  25 A are truncated cone-shaped. The running wheels  25  and therefore also the running surfaces  25 A can be shifted in their axial position by means of the adjusting wheels  26  and two screw threads (not shown). As a result, the point where the running surfaces  25 A lie on the rails  18 , and therefore the effective circumference of the running surfaces  25 A, and thus also the effective radius can be varied. As a result of such a variation, the transmission ratio between the first shaft  10  and the second shaft  22  is varied. Therefore, a reduction in the effective circumference of the running surface  25 A causes the clock to slow down and vice versa.  
         [0022]    The control element can also be formed by a magnet  31 , preferably a bar magnet, as shown in FIG. 4. The compartments are held together by screws  32  in the crown  33 . If the magnet is now positioned so as to pivot in the vicinity of the crown, preferably arranged above the crown, then at the correct point it ensures that the water level is lower than without a magnet, since it attracts the screw. If the clock is set to be slightly slow from the outset, it can be finely adjusted by means of the magnet  31  as a result of the magnet  31  being pivoted more or less towards the screws  32  in the direction of the arrow  34 . The magnet is preferably arranged symmetrically to the central plane of the clock in side view. A corresponding configuration may, of course, also be achieved in the other embodiments.  
         [0023]    If water is used as flowable medium inside the drum  20 , the high surface tension of the water poses something of a problem, even if reduced by additives, e.g. dishwashing detergent. Because the holes  28 A must be selected to be relatively small in order to obtain a correspondingly high flow resistance, it can result that the water completely stops flowing because of the high surface tension and this causes the clock to stop. This problem can be overcome by arranging grooves  28 B extending from the hole  28 A in the compartment wall. Since the water also flows into these grooves starting from the hole  28 A, the surface can thus be increased to such an extent that the surface tension is no longer significant.  
         [0024]    It is also possible to completely dispense with the compartment walls and use a highly viscous medium instead of water. In this case, the medium, e.g. an oil, constantly has a non-horizontal surface. The braking action here is also mainly based on the internal friction of the oil. However, a problem here is that the viscosity of most highly viscous liquids is highly temperature-dependent, and therefore even slight fluctuations in temperature can lead to considerable differences in precision.  
         [0025]    It should also be mentioned that not only liquids are possible as flowable media, but fine-grain solids, e.g. sand or similar, could also serve in principle as flowable medium.  
         [0026]    [0026]FIG. 3 shows a further embodiment of a braking element. Here the second shaft  22 , which interacts with the rest of the clock in the same manner as in the embodiment illustrated above, does not directly support a drum, but a circular disc  30  that is concentric relative to the axis B-B. This disc  30  supports six symmetrically arranged drums  20 . The number of drums  20  can be selected as desired, but must amount to at least two. Each drum  20  is divided into two compartments  27  by means of a compartment wall  28 . Each of the compartment walls has two holes  28 A located at the edge and a central opening  28 C. This is only shown by way of the drum located at the top position. As in the first embodiment, the holes  28 A are for the flow of water and with their size determine the flow resistance. Grooves that extend away from the holes are also provided in the compartment walls in this embodiment. These grooves are not shown in FIG. 3. The openings  28 C serve to equalize the air pressure. The opening  28 C may also be dispensed with, depending on the diameter of the holes  28 A.  
         [0027]    [0027]FIG. 4 shows a third embodiment of a braking element. A round disc  30  is likewise arranged on the second shaft  22  here. This disc  30  supports six drums  20  on each side, each drum overlapping two drums of the other side in top view. In this case also the number of drums on each side need not necessarily amount to six. The drums of the rear side of the disc are shown in broken lines in FIG. 4. The overlapping drums  20  are respectively interconnected by means of a hole  28  extending through the disc  30 , so that the water located in the drums can flow between adjacent drums. The drums  20  here have the function of the compartments  27  of the first embodiment. To facilitate escape of the displaced air, internal air holes  29  can be provided which are generally larger than the external holes  28 . It is also advantageous to provide grooves here which extend away from the holes  28 .  
         [0028]    The running surfaces and drums may also be actively interconnected via crown wheels. In order to facilitate setting of the clock in such a case, the weight or weights  11 ,  12  should be interchangeable or their weights variable.  
         [0029]    It is fundamentally also possible to arrange a braking element, i.e. a drum shown in the first embodiment, for example, directly on the first shaft  10  and rigidly connect it to this. In this case, the first axis A-A and the second axis B-B would then coincide.  
         [0030]    Since the principle by which the clock works should be visible from the outside, it is advantageous to produce the drum or drums from a transparent material such as plexiglass, for example.  
         [0031]    It should also be understood that this description can be subject to a wide variety of modifications, changes and adaptations, which revolve around equivalents to the attached claims.  
         [0032]    List of Reference Numerals  
                                                       A-A   first axis           B-B   second axis           10   first shaft           10A   bearing           11   first weight           12   second weight           14   cable           15   drive wheel           18   rails           20   drum           22   second shaft           23   liquid           25   running wheels           25A   running surfaces           26   adjusting wheel           27   compartment           28   compartment wall           28A   hole           28B   groove           28C   opening           29   air hole           30   disc           31   magnet           32   screws           33   crown           S   hour hand