Tilt sensor
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a tilt sensor. More particularly, the present invention relates to a tilt sensor that can sense the movement of a bubble in response to a tilting direction and output a signal representative of the sensed tilting. 
     2. Description of Related Art 
     A conventional tilt sensor simply lets a user know the tilting direction and has a low sensitivity. Normally, the sensor resides in a circuit for converting a physical characteristic into an electrical signal in order to output a signal in response to the tilting direction. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a tilt sensor for converting a physical characteristic, such as the movement of a bubble in response to a tilting direction into an electrical signal which has a high sensitivity and outputting a representative signal. 
     To achieve the above and other objects, the present invention is directed to a tilt sensor, comprising: 
     a container having a bubble on the surface of a conductive liquid is filled in the container; 
     an electrode to provide a current to the conductive liquid in the container; and 
     terminals to output the current provided from the electrode through the conductive liquid, thereby outputting a tilt sensing signal by the presence of an electric connection between the electrode and the terminals. 
     The tilt sensor according to the present invention is useful for all kinds of vehicles that passengers may ride in, particularly for the type of vehicles in which it is relatively difficult to perform tilt-sensing but in which such sensing is indespensable, such as like an airplane or a submarine. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further advantages and other objects of the present invention will be apparent in the following detailed description in connection with the accompanying drawings, in which: 
     FIG. 1A through 1C show the operation of a tilt sensor according to a first preferred embodiment of the present invention; 
     FIG. 2A shows a front view taken along line II--II and FIG. 2B shows an elevational view of a tilt sensor according to the first preferred embodiment of the present invention; 
     FIG. 3A shows a front view taken along line III--III and FIG. 3B shows an elevational view of the tilt sensor according to a second preferred embodiment of the present invention; 
     FIG. 4A shows a front view taken along line IV--IV and FIG. 4B shows an elevational view of the tilt sensor according to a third preferred embodiment of the present invention; 
     FIG. 5 depicts a front elevational view of the tilt sensor according to a fourth preferred embodiment of the present invention; and 
     FIG. 6 depicts a front elevational view of the tilt sensor according to a fifth preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1A through 1C show the operation of a tilt sensor according to a first preferred embodiment of the present invention and FIG. 2A shows a front view, and FIG. 2B shows an elevational view of the tilt sensor according to the first preferred embodiment of the present invention. 
     Reference numerals appearing in FIGS. 1A through 6 designate the following: 
     1: a rectangular container filled with a conductive liquid having a bubble of a predetermined size; 
     10: a bubble moving in response to a tilting direction of the container; 
     11: the conductive liquid for providing a current path; 
     12 : an electrode providing the current to the conductive liquid; and 
     14: two terminals outputting a sensed signal by a current applied to the electrode 12 through the current path made by the conductive liquid 11. 
     Since the two terminals 14 are entirely coated with an insulating material 13 except for exposed portions at the ends of the terminals, the current (due to electric potential Vcc applied to the electrode 12 (not shown in FIGS. 3A-6 for clarity) is outputted through protruding output ports 15 in case one or both ends of the terminals which are not covered with the insulating material are soaked by the conductive liquid 11 for making the current path. 
     The following description is about the operation of a tilt sensor according to the preferred embodiment of the present invention. 
     FIGS. 1B and 1C show a position of the bubble 10 in the tilt sensor in response to the tilting direction thereof. FIG. 1B shows the position of the bubble 10 in a case where the tilt sensor tilts to the left, and FIG. 1C shows the position of the bubble in a case where the tilt sensor tilts to the right. 
     Since the bubble 10 in the tilt sensor moves to the right side when the tilt sensor tilts to the left and a tilting degree is over a predetermined size as shown in FIG. 1B, the current applied to the electrode 12 is outputted through the left terminal 14 of which the end is soaked by the conductive liquid 11, via the current path made by the conductive liquid. 
     Since the bubble 10 is positioned in the middle of the surface of the liquid when the tilt sensor is in a horizontal state as shown in FIG. 1A, the ends of the left and right terminals 14 which are not covered with the insulating material are separated from the conductive liquid 11 and the current outputted from the left and the right terminals 14 is zero. 
     Since the bubble 10 in the tilt sensor moves to the left side when the tilt sensor tilts to the right and a tilting degree is over a predetermined size as shown in FIG. 1C, the current applied to the electrode is outputted through the right terminal 14 of which the end is soaked by the conductive liquid 11, via the current path made by the conductive liquid 11. 
     Accordingly, the present invention provides a tilt sensor having a high sensitivity, which senses a tilting direction of the tilt sensor 1 by moving the bubble 10 according to the tilting direction of the tilt sensor, separating the corresponding terminal 14 from the current path, that is, the conductive liquid, and determining the current outputted through the corresponding terminal to be zero. 
     FIGS. 2 through 6 are front views and elevational views of the tilt sensor according to the first to fifth preferred embodiment of the present invention. 
     FIG. 2A shows a front view and FIG. 2B shows an elevational view of the tilt sensor according to a first preferred embodiment of the present invention and FIG. 3A shows a front view and FIG. 3B shows an elevational view of the tilt sensor enhancing the sensing precision by mounting a plurality of terminals 14 lengthwise in the container according to a second preferred embodiment of the present invention. 
     FIG. 4 shows a front view and FIG. 4B shows an elevational view of the tilt sensor 1 of which the container is hemispheric and the terminals 14 are mounted to radiate in all directions along the curved surface of the upper part of the container, according to the third preferred embodiment of the present invention. 
     According to the third preferred embodiment of the present invention, a tilting degree of a position corresponding to a coordinate can be sensed. 
     Referring to the terminals, it is possible to mount the stick-shaped terminals 14 on the bottom of the container as in the first and third preferred embodiments of the present invention or along the small projection on the inner surface of the upper part of the container where the bubble moves as the fourth and fifth preferred embodiment of the present invention. 
     FIGS. 5 and 6 show the tilt sensor according to the fourth and fifth preferred embodiment of the present invention. Particularly, FIG. 6 shows a tilt sensor according to the fifth preferred embodiment of the present invention, of which the container is spherical and the terminals 14 are mounted along the inner circumferential surface of the container, thereby having a large tilt-sensible range and a high sensibility.