Patent Publication Number: US-6339199-B1

Title: Tilt switch

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a tilt switch, more particularly to a tilt switch which is adapted to be mounted on a support and which will establish an electrical connection between central and surrounding electric contact terminals that are mounted on the support when the support is tilted. 
     2. Description of the Related Art 
     A conventional tilt switch generally includes an insulating housing with a bottom-opened accommodating space for receiving an electrically conductive ball member. An insulating cover is disposed to cover the opening and has a plurality of through holes such that a plurality of elongate electric contact terminals can be press fitted within the through holes to contact with the ball member when the housing is in an upright direction. Outside ends of the terminals are soldered on an electric contact member of a circuit board. With such a construction, the conventional tilt switch is complicated and is inconvenient to assemble. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a tilt switch which is simple in construction and which is easy to assemble. 
     According to this invention, the tilt switch is adapted to be mounted on and to be in electric contact with a support in an upright direction. The tilt switch includes a central electric contact member which is adapted to be disposed on the support, and which defines a rolling area and a central line that extends in the upright direction and normal to the rolling area. A surrounding seat member is adapted to be disposed on the support, and surrounds the central electric contact member. The seat member has at least one first electric contact terminal which is spaced apart from the central electric contact member. An electrically conductive ball member is rollable on the rolling area. An electrically conductive shell member includes a surrounding lower edge which is disposed on the seat member and which has at least one second electric contact terminal that extends radially and outwardly from the surrounding lower edge and that is in electric contact with the first electric contact terminal, and a surrounding wall which extends from the surrounding lower edge in the upright direction and which surrounds the central line to terminate at a surrounding upper edge. The surrounding wall has an inner peripheral surface which faces towards and which surrounds the central line, and which cooperates with the support to confine an accommodating space for rollably accommodating the ball member. The inner peripheral surface is of such a dimension that a shortest one of distances, each of which is measured between two respective points on the inner peripheral surface opposite to each other relative to the central line, is larger than a diameter of the ball member. The ball member is disposed on the rolling area so that when the rolling area remains in a horizontal plane, the ball member is retained on the rolling area without being in contact with the inner peripheral surface. Once the rolling area is tilted from the horizontal plane, the ball member will move by virtue of gravity to contact with the inner peripheral surface so as to establish an electrical connection between the central electric contact member and the first electric contact terminal. A cap member is disposed on and is formed integrally with the surrounding upper edge to prevent movement of the ball member out of the accommodating space in the upright direction without hindering the rolling of the ball member on the rolling area. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other features and advantages of the present invention will become apparent in the following detailed description of the preferred embodiment of the invention, with reference to the accompanying drawings, in which: 
     FIG. 1 is a perspective view of a preferred embodiment of a tilt switch according to this invention when mounted on a support; 
     FIG. 2 is an exploded perspective view of the preferred embodiment of this invention; 
     FIG. 3 is a cross-sectional view of the preferred embodiment of this invention, taken along lines  3 — 3  of FIG.  1 ; and 
     FIG. 4 is a cross-sectional view of the preferred embodiment of this invention in a tilted state. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIGS. 1,  2  and  3 , the preferred embodiment of the tilt switch according to the present invention is shown to be adapted to be mounted on and to be in electric contact with a support  30 , such as a circuit board, in an upright direction. The support  30  has a pair of first holes  33  and a second hole  34  between the first holes  33 . The tilt switch is shown to comprise a central electric contact member  32 , such as a central copper foil, which is adapted to be attached on an upper major surface of the support  30  to define a rolling area and a central line that extends in the upright direction and that is normal to the rolling area. The central electric contact member  32  extends downwardly in the second hole  34  from the upper major surface and outwardly to a lower major surface of the support  30 . 
     A surrounding seat member  31 , such as an annular copper foil, is adapted to be attached on the upper major surface of the support  30 , and surrounds and is spaced apart from the central electric contact member  32  radially. The seat member  31  has a pair of first electric contact terminals  311  which are diametrically opposite to each other. Each first electric contact terminal  311  has a through hole  312  which is registered with the first hole  33 . 
     An electrically conductive ball member  20  is made of copper material, and is rollable on the rolling area of the central electric contact member  32 . 
     An electrically conductive shell member  10  includes a surrounding lower edge  16  which is disposed on the seat member  31  and which has a pair of second electric contact terminals  17  that extend radially and outwardly from the surrounding lower edge  16 . Each second electric contact terminal  17  has a terminal leg  14  which is inserted through the through hole  312  in the first electric contact terminal  311  and into the first hole  33 . An electrically conductive solder material  40  is disposed to interconnect electrically the terminal leg  14  with the first electric contact terminal  311 . A surrounding wall  12  extends from the surrounding lower edge  16  in the upright direction, and surrounds the central line of the central electric contact member  32  to terminate at a surrounding upper edge  121 . The surrounding wall  12  has an inner peripheral surface  122  which faces towards and which surrounds the central line, and which cooperates with the support  30  to confine an accommodating space  11  for rollably accommodating the ball member  20 . The inner peripheral surface  122  of the surrounding wall  12  has such a dimension that a shortest one of distances, each of which is measured between two respective points on the inner peripheral surface  122  opposite to each other relative to the central line, is larger than a diameter of the ball member  20 . Thus, the ball member  20  is disposed on the rolling area of the central electric contact member  32  so that when the rolling area remains in a horizontal plane, the ball member  20  is retained on the rolling area without being in contact with the inner peripheral surface  122 . As shown in FIG. 4, once the rolling area is tilted from the horizontal plane, the ball member  20  will move by virtue of gravity to contact with the inner peripheral surface  122  so as to establish an electrical connection between the central electric contact member  32  and the first electric contact terminal  311 . Preferably, the surrounding wall  12  flares from the surrounding upper edge  121  to the surrounding lower edge  16 . 
     A hemi-spherical cap member  15  is disposed on and is formed integrally with the surrounding upper edge  121  of the surrounding wall  12  to cover the accommodating space  11  so as to prevent movement of the ball member  20  out of the accommodating space  11  in the upright direction without hindering the rolling of the ball member  20  on the rolling area. 
     In assembly, after the ball member  20  is received in the accommodating space  11 , the assembly of the shell member  10  and the ball member  20  is mounted on the support  30 . The terminal legs  14  are inserted into the respective holes  312 , 14  and are connected securely to the first electric contact terminals  311  by the solder materials  40 . As such, the tilt switch of this invention has a simple construction that is easy to assemble. The tilt switch of this invention can be applied to a warning device, a toy, a security system, etc. 
     While the present invention has been described in connection with what is considered the most practical and preferred embodiment, it is understood that this invention is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretations and equivalent arrangements.